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158-414: A seizure is a sudden change in behavior, movement, and/or consciousness due to abnormal electrical activity in the brain . Seizures can look different in different people. It can be uncontrolled shaking of the whole body ( tonic-clonic seizures ) or a person spacing out for a few seconds ( absence seizures ). Most seizures last less than two minutes. They are then followed by confusion/drowsiness before

316-414: A brain–computer interface . Oscillatory activity is observed throughout the central nervous system at all levels of organization. Three different levels have been widely recognized: the micro-scale (activity of a single neuron), the meso-scale (activity of a local group of neurons) and the macro-scale (activity of different brain regions). Neurons generate action potentials resulting from changes in

474-403: A neural ensemble , also referred to as local synchronization. In addition to local synchronization, oscillatory activity of distant neural structures (single neurons or neural ensembles) can synchronize. Neural oscillations and synchronization have been linked to many cognitive functions such as information transfer, perception, motor control and memory. The opposite of neuron synchronization

632-452: A second-line treatment for adult obsessive–compulsive disorder (OCD) with mild functional impairment, and a first-line treatment for those with moderate or severe impairment. In children, SSRIs are considered as a second-line therapy in those with moderate-to-severe impairment, with close monitoring for psychiatric adverse effects. Sertraline and fluoxetine are effective in treating OCD for children and adolescents. Clomipramine ,

790-436: A TCA drug, is considered effective and useful for OCD. However, it is used as a second-line treatment because it is less well-tolerated than SSRIs. Despite this, it has not shown superiority to fluvoxamine in trials. All SSRIs can be used effectively for OCD. SNRI use may also be attempted, though no SNRIs have been approved for the treatment of OCD. Despite these treatment options, many patients remain symptomatic after initiating

948-672: A bimodal distribution, i.e. a high- and low-amplitude mode, and hence shows that resting-state activity does not just reflect a noise process. In case of fMRI, spontaneous fluctuations in the blood-oxygen-level dependent (BOLD) signal reveal correlation patterns that are linked to resting state networks, such as the default network . The temporal evolution of resting state networks is correlated with fluctuations of oscillatory EEG activity in different frequency bands. Ongoing brain activity may also have an important role in perception, as it may interact with activity related to incoming stimuli. Indeed, EEG studies suggest that visual perception

1106-506: A biological neuron is a mathematical description of the properties of nerve cells, or neurons, that is designed to accurately describe and predict its biological processes. One of the most successful neuron models is the Hodgkin–Huxley model, for which Hodgkin and Huxley won the 1963 Nobel Prize in physiology or medicine. The model is based on data from the squid giant axon and consists of nonlinear differential equations that approximate

1264-461: A bite. Weakness of one limb or asymmetric reflexes are also signs a seizure just occurred. Presence of urinary incontinence or fecal incontinence also strongly suggests a seizure occurred. However, most people who have had a seizure will have a normal physical exam. Blood tests can determine if there are any reversible causes of the seizure (provoked seizures). This includes a complete blood count that may show infection. A comprehensive metabolic panel

1422-1165: A broad spectral content similar to pink noise , but also reveal oscillatory activity in specific frequency bands. The first discovered and best-known frequency band is alpha activity (8–12 Hz ) that can be detected from the occipital lobe during relaxed wakefulness and which increases when the eyes are closed. Other frequency bands are: delta (1–4 Hz), theta (4–8 Hz), beta (13–30 Hz), low gamma (30–70 Hz), and high gamma (70–150 Hz) frequency bands. Faster rhythms such as gamma activity have been linked to cognitive processing. Indeed, EEG signals change dramatically during sleep. In fact, different sleep stages are commonly characterized by their spectral content. Consequently, neural oscillations have been linked to cognitive states, such as awareness and consciousness . Although neural oscillations in human brain activity are mostly investigated using EEG recordings, they are also observed using more invasive recording techniques such as single-unit recordings . Neurons can generate rhythmic patterns of action potentials or spikes. Some types of neurons have

1580-1195: A cause that is temporary and reversible. They are also known as Acute Symptomatic Seizures as they occur closely after the injury. Unprovoked seizures do not have a known cause or the cause is not reversible. Unprovoked seizures are typically considered epilepsy and treated as epilepsy. Of those who have a seizure, about 25% have epilepsy . Those with epilepsy may have certain triggers that they know cause seizures to occur, including emotional stress, sleep deprivation, and flickering lights. Dehydration can trigger epileptic seizures by changing electrolyte balances. Low blood sugar, low blood sodium , high blood sugar , high blood sodium , low blood calcium , high blood urea , and low blood magnesium levels may cause seizures. Up to 9% of status epilepticus cases occur due to drug intoxication. Common drugs involved include antidepressants , stimulants ( cocaine ), and antihistamines . Withdrawal seizures commonly occur after prolonged alcohol or sedative use. In people who are at risk of developing epileptic seizures, common herbal medicines such as ephedra , ginkgo biloba and wormwood can provoke seizures. Systemic infection with high fever

1738-429: A common frequency, they will generate oscillations in the mean field. (See also figure at top of page.) Neural ensembles can generate oscillatory activity endogenously through local interactions between excitatory and inhibitory neurons. In particular, inhibitory interneurons play an important role in producing neural ensemble synchrony by generating a narrow window for effective excitation and rhythmically modulating

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1896-458: A discussion between the patient and doctor. In children with one simple febrile seizure , starting anti-seizure medications is not recommended. While both fever medications ( antipyretics) and anti-seizure medications reduce reoccurrence, the harmless nature of febrile seizures outweighs the risks of these medications. However, if it was a complex febrile seizure, EEG should be done. If EEG is abnormal, starting prophylactic anti-seizure medications

2054-451: A dynamical pattern at the global scale. The Kuramoto model is widely used to study oscillatory brain activity, and several extensions have been proposed that increase its neurobiological plausibility, for instance by incorporating topological properties of local cortical connectivity. In particular, it describes how the activity of a group of interacting neurons can become synchronized and generate large-scale oscillations. Simulations using

2212-402: A first seizure depends on many factors. If it was an unprovoked seizure with abnormal brain imaging or abnormal EEG, then it is recommended to start anti-seizure medication. If a person has an unprovoked seizure, but physical exam is normal, EEG is normal, and brain imaging is normal, then anti-seizure medication may not be needed. The decision to start anti-seizure medications should be made after

2370-414: A group of interacting neurons that form a network, called a central pattern generator . Central pattern generators are neuronal circuits that—when activated—can produce rhythmic motor patterns in the absence of sensory or descending inputs that carry specific timing information. Examples are walking , breathing , and swimming , Most evidence for central pattern generators comes from lower animals, such as

2528-404: A mental health professional in the previous year. Several strategies are used in clinical practice to try to overcome these limits and variations. They include switching medication, augmentation, and combination. There is controversy amongst researchers regarding the efficacy and risk-benefit ratio of antidepressants. Although antidepressants consistently out-perform a placebo in meta-analyses,

2686-706: A more physiologically realistic setting, oscillatory activity is generally studied using computer simulations of a computational model . The functions of neural oscillations are wide-ranging and vary for different types of oscillatory activity. Examples are the generation of rhythmic activity such as a heartbeat and the neural binding of sensory features in perception, such as the shape and color of an object. Neural oscillations also play an important role in many neurological disorders , such as excessive synchronization during seizure activity in epilepsy , or tremor in patients with Parkinson's disease . Oscillatory activity can also be used to control external devices such as

2844-513: A much slower time scale. That is, the concentration levels of certain neurotransmitters are known to regulate the amount of oscillatory activity. For instance, GABA concentration has been shown to be positively correlated with frequency of oscillations in induced stimuli. A number of nuclei in the brainstem have diffuse projections throughout the brain influencing concentration levels of neurotransmitters such as norepinephrine , acetylcholine and serotonin . These neurotransmitter systems affect

3002-425: A neural code representing multiple items in a temporal frame Neural synchronization can be modulated by task constraints, such as attention , and is thought to play a role in feature binding , neuronal communication , and motor coordination . Neuronal oscillations became a hot topic in neuroscience in the 1990s when the studies of the visual system of the brain by Gray, Singer and others appeared to support

3160-536: A new drug and staying on the old medication: although 34% of treatment-resistant people responded when switched to the new drug, 40% responded without being switched. For a partial response, the American Psychiatric Association (APA) guidelines suggest augmentation or adding a drug from a different class. These include lithium and thyroid augmentation, dopamine agonists , sex steroids , NRIs , glucocorticoid -specific agents, or

3318-459: A person has never had a seizure but anti-seizure medications are started to prevent seizures in those at risk. Following traumatic brain injury , anti-seizure medications decrease the risk of early seizures but not late seizures. However, there is no clear evidence that anti-seizure medications are effective at preventing seizures following brain surgery ( craniotomy) , a brain bleed, or after a stroke . Prevention of seizures from re-occurring after

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3476-612: A person suffering from loss of energy and enjoyment of life would take a norepinephrine–dopamine reuptake inhibitor . The UK National Institute for Health and Care Excellence (NICE)'s 2022 guidelines indicate that antidepressants should not be routinely used for the initial treatment of mild depression, "unless that is the person's preference". The guidelines recommended that antidepressant treatment be considered: The guidelines further note that in most cases, antidepressants should be used in combination with psychosocial interventions and should be continued for at least six months to reduce

3634-474: A person's first seizure, they are legally not allowed to drive until they are seizure-free for a period of time. This period of time varies between states, but is usually between 6 and 12 months. They are also cautioned against working at heights and swimming alone in case a seizure occurs. Following a first unprovoked seizure, the risk of more seizures in the next two years is around 40%. Starting anti-seizure medications reduces recurrence of seizures by 35% within

3792-547: A phenomenon called publication bias or selective publication. Although this issue has diminished with time, it remains an obstacle to accurately assessing the efficacy of antidepressants. Misreporting of clinical trial outcomes and of serious adverse events, such as suicide, is common. Ghostwriting of antidepressant trials is widespread, a practice in which prominent researchers, or so-called key opinion leaders, attach their names to studies actually written by pharmaceutical company employees or consultants. A particular concern

3950-433: A placebo, while the other SNRIs are not considered particularly useful for this disorder as many of them did not undergo testing for it. As of 2008 , it is unclear if duloxetine and desvenlafaxine can provide benefits for people with social anxiety. However, another class of antidepressants called MAOIs are considered effective for social anxiety, but they come with many unwanted side effects and are rarely used. Phenelzine

4108-567: A population of physically interconnected neurons or a group of disparate neurons whose inputs or signalling targets define a recognizable circuit. These models aim to describe how the dynamics of neural circuitry arise from interactions between individual neurons. Local interactions between neurons can result in the synchronization of spiking activity and form the basis of oscillatory activity. In particular, models of interacting pyramidal cells and inhibitory interneurons have been shown to generate brain rhythms such as gamma activity . Similarly, it

4266-513: A potentially lethal hypertensive crisis . At lower doses, the person may only experience a headache due to an increase in blood pressure. In response to these adverse effects, a different type of MAOI, the class of reversible inhibitor of monoamine oxidase A (RIMA), has been developed. The primary advantage of RIMAs is that they do not require the person to follow a special diet while being purportedly effective as SSRIs and tricyclics in treating depressive disorders. Tricyclics and SSRI can cause

4424-620: A risk of causing epilepsy. Infection with the pork tapeworm , which can cause neurocysticercosis , is the cause of up to half of epilepsy cases in areas of the world where the parasite is common. Meningitis and encephalitis also carry the risk of causing long-term epilepsy as well. During childhood, well-defined epilepsy syndromes are generally seen. Examples include Dravet Syndrome , Lennox-Gastaut Syndrome , and Juvenile Myoclonic Epilepsy . Neurons function by either being excited or inhibited. Excited neurons fire electrical charges while inhibited neurons are prevented from firing. The balance of

4582-570: A second seizure. In children, the risk of seizure recurrence within the five years following a single unprovoked seizure is about 50%; the risk rises to about 80% after two unprovoked seizures. In the United States in 2011, seizures resulted in an estimated 1.6 million emergency department visits; approximately 400,000 of these visits were for new-onset seizures. Epileptic seizures were first described in an Akkadian text from 2000 B.C. Early reports of epilepsy often saw seizures and convulsions as

4740-540: A seizure. Some claim that seizure response dogs , a form of service dog , can predict seizures. Evidence for this, however, is poor. Cannabis has also been used for the management of seizures that do not respond to anti-seizure medications. Research on its effectiveness is ongoing, but current research shows that it does reduce seizure frequency. A ketogenic diet or modified Atkins diet may help in those who have epilepsy who do not improve following typical treatments, with evidence for its effectiveness growing. Following

4898-671: A short follow up after termination of treatment; non-systematic recording of adverse effects; very strict exclusion criteria in samples of patients; studies being paid for by the industry; selective publication of results. This means that the small beneficial effects that are found may not be statistically significant. Among the 21 most commonly prescribed antidepressants, the most effective and well-tolerated are escitalopram , paroxetine , sertraline , agomelatine , and mirtazapine . For children and adolescents with moderate to severe depressive disorder, some evidence suggests fluoxetine (either with or without cognitive behavioral therapy )

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5056-495: A slow wave and a fast wave. There are many kinds, generally written as A-B coupling, meaning the A of a slow wave is coupled with the B of a fast wave. For example, phase–amplitude coupling is where the phase of a slow wave is coupled with the amplitude of a fast wave. The theta-gamma code is a coupling between theta wave and gamma wave in the hippocampal network. During a theta wave, 4 to 8 non-overlapping neuron ensembles are activated in sequence. This has been hypothesized to form

5214-399: A system affect each other after significant time delays. Limit-cycle oscillations can be complex but there are powerful mathematical tools for analyzing them; the mathematics of delayed-feedback oscillations is primitive in comparison. Linear oscillators and limit-cycle oscillators qualitatively differ in terms of how they respond to fluctuations in input. In a linear oscillator, the frequency

5372-437: A tool that allows people to rate their concern about common side effects of antidepressants. The tool ranks potential treatment options in a visual display that highlights the drugs with side effects of least concern to an individual. SSRI use in pregnancy has been associated with a variety of risks with varying degrees of proof of causation. As depression is independently associated with negative pregnancy outcomes, determining

5530-441: A treatment for social anxiety disorder , but their efficacy is not entirely convincing, as only a small proportion of antidepressants showed some effectiveness for this condition. Paroxetine was the first drug to be FDA-approved for this disorder. Its efficacy is considered beneficial, although not everyone responds favorably to the drug. Sertraline and fluvoxamine extended-release were later approved for it as well, while escitalopram

5688-524: Is a benzodiazepine , with most guidelines recommending lorazepam . Diazepam and midazolam are alternatives. It may be given in IV if emergency services is present. Rectal and intranasal forms also exist if a child has had seizures previously and was prescribed the rescue medication. If seizures continue, second-line therapy includes phenytoin , fosphenytoin , and phenobarbital . Levetiracetam or valproate may also be used. Starting anti-seizure medications

5846-462: Is a common cause of seizures, especially in children. These are called febrile seizures and occur in 2–5% of children between the ages of six months and five years. Acute infection of the brain, such as encephalitis or meningitis are also causes of seizures. Acute stroke or brain bleed may lead to seizures. Stroke is the most common cause of seizures in the elderly population. Post-stroke seizures occur in 5-7% of those with ischemic strokes. It

6004-479: Is a common disorder in which the central feature is excessively worrying about numerous events. Key symptoms include excessive anxiety about events and issues going on around them and difficulty controlling worrisome thoughts that persists for at least 6 months. Antidepressants provide a modest to moderate reduction in anxiety in GAD. The efficacy of different antidepressants is similar. Some antidepressants are used as

6162-529: Is a high treatment response heterogeneity. Some patients, that differ strongly in their response to antidepressants, could influence the average response, while the heterogeneity could itself be obscured by the averaging. Studies have not supported this hypothesis, but it is very difficult to measure treatment effect heterogeneity. Poor and complex clinical trial design might also account for the small effects seen for antidepressants. The randomized controlled trials used to approve drugs are short, and may not capture

6320-526: Is a person's first seizure and it was "provoked", or caused by another condition, treatment of the cause is usually enough to treat the seizure. If the seizure is "unprovoked", brain imaging is abnormal, and/or EEG is abnormal, start anti-seizure medications is generally recommmended. A seizure can last from a few seconds to 5 minutes. Once it reaches and passes 5 minutes, it is known as status epilepticus . Accidental urination ( urinary incontinence ), stool leaking ( fecal incontinence ), tongue biting, foaming of

6478-495: Is affected. Focal seizures usually consist of motor symptoms or sensory symptoms. Generalized seizures affect both sides of the brain and typically involve both sides of the body. They all involve a loss of consciousness and usually happen without warning. There are six main types of generalized seizures: tonic-clonic, tonic, clonic, myoclonic, absence, and atonic seizures. Seizures have a number of causes. Seizures can be classified into provoked or unprovoked. Provoked seizures have

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6636-414: Is also important in evaluating risk for epilepsy. History regarding medication use, substance use, and alcohol use is important in determining a cause of the seizure. Most people are in a postictal state (drowsy or confused) following a seizure. A bite mark on the side of the tongue or bleeding from the mouth strongly indicates a seizure happened. But only a third of people who have had a seizure have such

6794-481: Is amplitude change in oscillatory activity. For instance, gamma activity often increases during increased mental activity such as during object representation. Because induced responses may have different phases across measurements and therefore would cancel out during averaging, they can only be obtained using time-frequency analysis . Induced activity generally reflects the activity of numerous neurons: amplitude changes in oscillatory activity are thought to arise from

6952-464: Is an increased risk of suicidal thinking and behavior when taken by children, adolescents, and young adults. Discontinuation syndrome , which resembles recurrent depression in the case of the SSRI class, may occur after stopping the intake of any antidepressant, having effects which may be permanent and irreversible. Research regarding the effectiveness of antidepressants for depression in adults

7110-496: Is an ongoing debate. It has recently been proposed that even if phases are not aligned across trials, induced activity may still cause event-related potentials because ongoing brain oscillations may not be symmetric and thus amplitude modulations may result in a baseline shift that does not average out. This model implies that slow event-related responses, such as asymmetric alpha activity, could result from asymmetric brain oscillation amplitude modulations, such as an asymmetry of

7268-517: Is arbitrary, and that antidepressants consistently result in significantly raised scores on the mood item of the scale. Assessments of antidepressants using alternative, more sensitive scales, such as the MADRS , do not result in marked difference from the HDRS and likewise only find a marginal clinical benefit. Another hypothesis proposed to explain the poor performance of antidepressants in clinical trials

7426-449: Is best seen in local field potentials which reflect the synchronous activity of local groups of neurons, but has also been shown in EEG and MEG recordings providing increasing evidence for a close relation between synchronous oscillatory activity and a variety of cognitive functions such as perceptual grouping and attentional top-down control. Cells in the sinoatrial node , located in

7584-433: Is considered to play a crucial role during brain development, such as in network formation and synaptogenesis. Spontaneous activity may be informative regarding the current mental state of the person (e.g. wakefulness, alertness) and is often used in sleep research. Certain types of oscillatory activity, such as alpha waves , are part of spontaneous activity. Statistical analysis of power fluctuations of alpha activity reveals

7742-483: Is controversial and has found both benefits and drawbacks. Meanwhile, evidence of benefit in children and adolescents is unclear, even though antidepressant use has considerably increased in children and adolescents in the 2000s. While a 2018 study found that the 21 most commonly prescribed antidepressant medications were slightly more effective than placebos for the short-term (acute) treatments of adults with major depressive disorder , other research has found that

7900-579: Is currently unclear which factors predict partial remission. However, it is clear that residual symptoms are powerful predictors of relapse, with relapse rates three to six times higher in people with residual symptoms than in those, who experience full remission. In addition, antidepressant drugs tend to lose efficacy throughout long-term maintenance therapy . According to data from the Centers for Disease Control and Prevention , less than one-third of Americans taking one antidepressant medication have seen

8058-423: Is dependent on both the phase and amplitude of cortical oscillations. For instance, the amplitude and phase of alpha activity at the moment of visual stimulation predicts whether a weak stimulus will be perceived by the subject. In response to input, a neuron or neuronal ensemble may change the frequency at which it oscillates, thus changing the rate at which it spikes. Often, a neuron's firing rate depends on

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8216-524: Is done to detect structural problems inside the brain, such as tumors. MRI is generally the better imaging test, but CT scan is preferred when intracranial bleeding is suspected. Imaging may be done at a later point in time in those who return to their normal selves while in the emergency room. An electroencephalography (EEG) measures the brain's electrical activity. It is used in cases of first seizures that have no provoking factor, normal head imaging, and no prior history of head trauma. It will help determine

8374-642: Is estimated to result in costs of US$ 1.7 billion or 0.5% of the GDP. They make up about 1% of emergency department visits (2% for emergency departments for children) in the United States. Scientific work into the prediction of epileptic seizures began in the 1970s. Several techniques and methods have been proposed, but evidence regarding their usefulness is still lacking. Two promising areas include: (1) gene therapy , and (2) seizure detection and seizure prediction . Gene therapy for epilepsy consists of employing vectors to deliver pieces of genetic material to areas of

8532-506: Is found, it is called an idiopathic seizure. After a first unprovoked seizure, the chance of experiencing a second one is about 40% within 2 years. People with repeated unprovoked seizures are diagnosed with epilepsy . Doctors assess a seizure by first ruling out other conditions that look similar to seizures, such as fainting and strokes. This includes taking a detailed history and ordering blood tests. They may also order an electroencephalogram (EEG) and brain imaging (CT and/or MRI). If it

8690-410: Is higher in those who experienced brain bleeds, with 10-16% risk in those patients. Recent traumatic brain injury may also lead to seizures. 1 to 5 of every 10 people who have had traumatic brain injury have experienced at least one seizure. Seizures may occur within 7 days of the injury (early posttraumatic seizure ) or after 7 days have passed (late posttraumatic seizure). Space-occupying lesions in

8848-508: Is inversely related to the delay time. An example of such a feedback loop is the connections between the thalamus and cortex – the thalamocortical radiations . This thalamocortical network is able to generate oscillatory activity known as recurrent thalamo-cortical resonance . The thalamocortical network plays an important role in the generation of alpha activity . In a whole-brain network model with realistic anatomical connectivity and propagation delays between brain areas, oscillations in

9006-423: Is less than 20% regardless of treatment. Those who have a seizure that is provoked have a low risk of re-occurrence, but have a higher risk of death compared to those with epilepsy. Approximately 8–10% of people will experience an epileptic seizure during their lifetime. In adults, the risk of seizure recurrence within the five years following a new-onset seizure is 35%; the risk rises to 75% in persons who have had

9164-491: Is loss of inhibitory neurons because they die due to the injury. The brain may also adapt and make new neuron connections that may be hyper-excitatory. Brief seizures, such as absence seizures lasting 5–10 seconds, do not cause observable brain damage. More prolonged seizures have a higher risk of neuronal death. Prolonged and recurrent seizures, such as status epilepticus, typically cause brain damage. Scarring of brain tissue ( gliosis ), neuronal death, and shrinking of areas of

9322-513: Is more or less constant but the amplitude can vary greatly. In a limit-cycle oscillator, the amplitude tends to be more or less constant but the frequency can vary greatly. A heartbeat is an example of a limit-cycle oscillation in that the frequency of beats varies widely, while each individual beat continues to pump about the same amount of blood. Computational models adopt a variety of abstractions in order to describe complex oscillatory dynamics observed in brain activity. Many models are used in

9480-894: Is neural isolation, which is when electrical activity of neurons is not temporally synchronized. This is when the likelihood of the neuron to reach its threshold potential for the signal to propagate to the next neuron decreases. This phenomenon is typically observed as the spectral intensity decreases from the summation of these neurons firing, which can be utilized to differentiate cognitive function or neural isolation. However, new non-linear methods have been used that couple temporal and spectral entropic relationships simultaneously to characterize how neurons are isolated, (the signal's inability to propagate to adjacent neurons), an indicator of impairment (e.g., hypoxia). Neural oscillations have been most widely studied in neural activity generated by large groups of neurons. Large-scale activity can be measured by techniques such as EEG. In general, EEG signals have

9638-542: Is not typically recommended if it was a provoked seizure that can be corrected. Examples of causes of provoked seizures that can be corrected include low blood sugar, low blood sodium, febrile seizures in children, and substance/medication use. Starting anti-seizure medications is usually for those with medium to high risk of seizures re-occurring. This includes people with unprovoked seizures with abnormal brain imaging or abnormal EEG. It also includes those who have had more than one unprovoked seizure more than 24 hours apart. It

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9796-457: Is often selectively reported in trials of antidepressants. For children and adolescents, fluvoxamine is effective in treating a range of anxiety disorders. Fluoxetine, sertraline, and paroxetine can also help with managing various forms of anxiety in children and adolescents. Meta-analyses of published and unpublished trials have found that antidepressants have a placebo -subtracted effect size ( standardized mean difference or SMD) in

9954-436: Is one of the most abstract and fundamental models used to investigate neural oscillations and synchronization. It captures the activity of a local system (e.g., a single neuron or neural ensemble) by its circular phase alone and hence ignores the amplitude of oscillations (amplitude is constant). Interactions amongst these oscillators are introduced by a simple algebraic form (such as a sine function) and collectively generate

10112-465: Is ordered to rule out abnormal sugar levels (hypoglycemia or hyperglycemia) or electrolyte abnormalities (such as hyponatremia) as a cause. A lumbar puncture is mainly done if there is reason to believe infection or inflammation of the nervous system is occurring. Toxicology screening is also mainly done if history is suggestive. Brain imaging by CT scan and MRI is recommended after a first seizure, especially if no provoking factors are discovered . It

10270-411: Is planned. Reviews of antidepressants generally find that they benefit adults with depression. On the other hand, some contend that most studies on antidepressant medication are confounded by several biases: the lack of an active placebo , which means that many people in the placebo arm of a double-blind study may deduce that they are not getting any true treatment, thus destroying double-blindness;

10428-498: Is recommended to start with one anti-seizure medication. Another may be added if one is not enough to control the seizure occurrence. Approximately 70% of people can obtain full control with continuous use of medication. The type of medication used is based on the type of seizure. Anti-seizure medications may be slowly stopped after a period of time if a person has just experienced one seizure and has not had anymore. The decision to stop anti-seizure medications should be discussed between

10586-407: Is recommended. During an active seizure, the person seizing should be slowly laid on the floor. Witnesses should not try to stop the convulsions or other movements. Potentially sharp or dangerous objects should be moved from the area around a person experiencing a seizure so that the individual is not hurt. Nothing should be placed in the person's mouth as it is a choking hazard. After the seizure, if

10744-464: Is referred to as phase resetting. In addition, external activity may not interact with ongoing activity at all, resulting in an additive response. Spontaneous activity is brain activity in the absence of an explicit task, such as sensory input or motor output, and hence also referred to as resting-state activity. It is opposed to induced activity, i.e. brain activity that is induced by sensory stimuli or motor responses. The term ongoing brain activity

10902-652: Is significantly higher than what paroxetine and sertraline achieved. However, it did not address as many symptoms of PTSD as paroxetine and sertraline, in part due to the fact that venlafaxine is an SNRI . This class of drugs inhibits the reuptake of norepinephrine, which may cause anxiety in some patients. Fluvoxamine, escitalopram, and citalopram were not well-tested for this disorder. MAOIs , while some of them may be helpful, are not used much because of their unwanted side effects. This leaves paroxetine and sertraline as acceptable treatment options for some people, although more effective antidepressants are needed. Panic disorder

11060-524: Is that the psychoactive effects of antidepressants may lead to the unblinding of participants or researchers, enhancing the placebo effect and biasing results. Some have therefore maintained that antidepressants may only be active placebos. When these and other flaws in the research literature are not taken into account, meta-analyses may find inflated results on the basis of poor evidence. Critics contend that antidepressants have not been proven sufficiently effective by RCTs or in clinical practice and that

11218-622: Is the best treatment, but more research is needed to be certain. Sertraline, escitalopram, and duloxetine may also help reduce symptoms. A 2023 systematic review and meta-analysis of randomized controlled trials of antidepressants for major depressive disorder found that the medications provided only small or doubtful benefits in terms of quality of life . Likewise, a 2022 systematic review and meta-analysis of randomized controlled trials of antidepressants for major depressive disorder in children and adolescents found small improvements in quality of life. Quality of life as an outcome measure

11376-486: Is the result of pharmaceutical advertising, research manipulation, and misinformation. Current mainstream psychiatric opinion recognizes the limitations of antidepressants but recommends their use in adults with more severe depression as a first-line treatment. The American Psychiatric Association 2000 Practice Guideline advises that where no response is achieved within the following six to eight weeks of treatment with an antidepressant, switch to an antidepressant in

11534-551: Is treated relatively well with medications compared to other disorders. Several classes of antidepressants have shown efficacy for this disorder, with SSRIs and SNRIs used first-line. Paroxetine, sertraline, and fluoxetine are FDA-approved for panic disorder, while fluvoxamine, escitalopram, and citalopram are also considered effective for them. SNRI venlafaxine is also approved for this condition. Unlike social anxiety and PTSD , some TCAs antidepressants , like clomipramine and imipramine, have shown efficacy for panic disorder. Moreover,

11692-435: Is used off-label with acceptable efficiency. However, there is not enough evidence to support Citalopram for treating social anxiety disorder, and fluoxetine was no better than a placebo in clinical trials. SSRIs are used as a first-line treatment for social anxiety, but they do not work for everyone. One alternative would be venlafaxine , an SNRI , which has shown benefits for social phobia in five clinical trials against

11850-445: Is used in electroencephalography and magnetoencephalography for those signal components that are not associated with the processing of a stimulus or the occurrence of specific other events, such as moving a body part, i.e. events that do not form evoked potentials / evoked fields , or induced activity. Spontaneous activity is usually considered to be noise if one is interested in stimulus processing; however, spontaneous activity

12008-405: Is very common in single neurons where spike timing is adjusted to neuronal input (a neuron may spike at a fixed delay in response to periodic input, which is referred to as phase locking ) and may also occur in neuronal ensembles when the phases of their neurons are adjusted simultaneously. Phase resetting is fundamental for the synchronization of different neurons or different brain regions because

12166-546: The FitzHugh–Nagumo model and the Hindmarsh–Rose model , or highly idealized neuron models such as the leaky integrate-and-fire neuron, originally developed by Lapique in 1907. Such models only capture salient membrane dynamics such as spiking or bursting at the cost of biophysical detail, but are more computationally efficient, enabling simulations of larger biological neural networks . A neural network model describes

12324-612: The MAOI phenelzine is also considered useful. Panic disorder has many drugs for its treatment. However, the starting dose must be lower than the one used for major depressive disorder because people have reported an increase in anxiety as a result of starting the medication. In conclusion, while panic disorder's treatment options seem acceptable and useful for this condition, many people are still symptomatic after treatment with residual symptoms. Antidepressants are recommended as an alternative or additional first step to self-help programs in

12482-540: The Wilson-Cowan model . If a group of neurons engages in synchronized oscillatory activity, the neural ensemble can be mathematically represented as a single oscillator. Different neural ensembles are coupled through long-range connections and form a network of weakly coupled oscillators at the next spatial scale. Weakly coupled oscillators can generate a range of dynamics including oscillatory activity. Long-range connections between different brain structures, such as

12640-455: The beta frequency range emerge from the partial synchronisation of subsets of brain areas oscillating in the gamma-band (generated at the mesoscopic level). Scientists have identified some intrinsic neuronal properties that play an important role in generating membrane potential oscillations. In particular, voltage-gated ion channels are critical in the generation of action potentials. The dynamics of these ion channels have been captured in

12798-476: The heart rate . In the absence of extrinsic neural and hormonal control, cells in the SA node will rhythmically discharge. The sinoatrial node is richly innervated by the autonomic nervous system , which up or down regulates the spontaneous firing frequency of the pacemaker cells. Synchronized firing of neurons also forms the basis of periodic motor commands for rhythmic movements. These rhythmic outputs are produced by

12956-448: The lamprey , but there is also evidence for spinal central pattern generators in humans. Antidepressants Antidepressants are a class of medications used to treat major depressive disorder , anxiety disorders , chronic pain , and addiction . Common side effects of antidepressants include dry mouth , weight gain , dizziness , headaches , akathisia , sexual dysfunction , and emotional blunting . There

13114-400: The neural binding hypothesis. According to this idea, synchronous oscillations in neuronal ensembles bind neurons representing different features of an object. For example, when a person looks at a tree, visual cortex neurons representing the tree trunk and those representing the branches of the same tree would oscillate in synchrony to form a single representation of the tree. This phenomenon

13272-438: The right atrium of the heart, spontaneously depolarize approximately 100 times per minute. Although all of the heart's cells have the ability to generate action potentials that trigger cardiac contraction, the sinoatrial node normally initiates it, simply because it generates impulses slightly faster than the other areas. Hence, these cells generate the normal sinus rhythm and are called pacemaker cells as they directly control

13430-584: The thalamus and the cortex (see thalamocortical oscillation ), involve time-delays due to the finite conduction velocity of axons. Because most connections are reciprocal, they form feed-back loops that support oscillatory activity. Oscillations recorded from multiple cortical areas can become synchronized to form large-scale brain networks , whose dynamics and functional connectivity can be studied by means of spectral analysis and Granger causality measures. Coherent activity of large-scale brain activity may form dynamic links between brain areas required for

13588-521: The Kuramoto model with realistic long-range cortical connectivity and time-delayed interactions reveal the emergence of slow patterned fluctuations that reproduce resting-state BOLD functional maps, which can be measured using fMRI . Both single neurons and groups of neurons can generate oscillatory activity spontaneously. In addition, they may show oscillatory responses to perceptual input or motor output. Some types of neurons will fire rhythmically in

13746-612: The Sacred Disease , who proposed that the source of epilepsy was from natural causes rather than supernatural ones. Early surgical treatment of epilepsy was primitive in Ancient Greek, Roman and Egyptian medicine. The 19th century saw the rise of targeted surgery for the treatment of epileptic seizures, beginning in 1886 with localized resections performed by Sir Victor Horsley , a neurosurgeon in London. Another advancement

13904-401: The absence of any synaptic input. Likewise, brain-wide activity reveals oscillatory activity while subjects do not engage in any activity, so-called resting-state activity . These ongoing rhythms can change in different ways in response to perceptual input or motor output. Oscillatory activity may respond by increases or decreases in frequency and amplitude or show a temporary interruption, which

14062-478: The benefit of antidepressants for anxiety disorders is attributable to placebo responses rather than to the effects of the antidepressants themselves. Antidepressants are recommended by the National Institute for Health and Care Excellence (NICE) for the treatment of generalized anxiety disorder (GAD) that has failed to respond to conservative measures such as education and self-help activities. GAD

14220-491: The brain ( abscesses , tumours ) are one cause of unprovoked seizures. In people with brain tumours , the frequency of epilepsy depends on the location of the tumor in the cortical region . Abnormalities in blood vessels of the brain ( Arteriovenous malformation ) can also cause epilepsy. In babies and children, congenital brain abnormalities, such as lissencephaly or polymicrogyria , will also result in epilepsy. Hypoxic-ischemic encephalopathy in newborns will also predispose

14378-410: The brain ( atrophy ) are linked to recurrent seizures. These changes may lead to the development of epilepsy. Diagnosis of seizures involve gathering history, doing a physical exam, and ordering tests. These are done to classify the seizure and determine if the seizure is provoked or unprovoked. Events leading up to the seizure and what movements occurred during the seizure are important in classifying

14536-516: The brain involved in seizure onset. Seizure prediction is a special case of seizure detection in which the developed systems is able to issue a warning before the clinical onset of the epileptic seizure. Computational neuroscience has been able to bring a new point of view on the seizures by considering the dynamical aspects. Neural oscillation Neural oscillations in humans were observed by researchers as early as 1924 (by Hans Berger ). More than 50 years later, intrinsic oscillatory behavior

14694-490: The brain is widely observed at different levels of organization and is thought to play a key role in processing neural information. Numerous experimental studies support a functional role of neural oscillations; a unified interpretation, however, is still lacking. Richard Caton discovered electrical activity in the cerebral hemispheres of rabbits and monkeys and presented his findings in 1875. Adolf Beck published in 1890 his observations of spontaneous electrical activity of

14852-818: The brain of rabbits and dogs that included rhythmic oscillations altered by light, detected with electrodes directly placed on the surface of the brain. Before Hans Berger , Vladimir Vladimirovich Pravdich-Neminsky published the first animal EEG and the evoked potential of a dog. Neural oscillations are observed throughout the central nervous system at all levels, and include spike trains , local field potentials and large-scale oscillations which can be measured by electroencephalography (EEG). In general, oscillations can be characterized by their frequency , amplitude and phase . These signal properties can be extracted from neural recordings using time-frequency analysis . In large-scale oscillations, amplitude changes are considered to result from changes in synchronization within

15010-621: The central idea is to take the density of neurons to the continuum limit , resulting in spatially continuous neural networks . Instead of modelling individual neurons, this approach approximates a group of neurons by its average properties and interactions. It is based on the mean field approach , an area of statistical physics that deals with large-scale systems. Models based on these principles have been used to provide mathematical descriptions of neural oscillations and EEG rhythms. They have for instance been used to investigate visual hallucinations. The Kuramoto model of coupled phase oscillators

15168-571: The condition is serious, it is not particularly common, generally only appearing at high doses or while on other medications. Assuming proper medical intervention has been taken (within about 24 hours) it is rarely fatal. Antidepressants appear to increase the risk of diabetes by about 1.3-fold. MAOIs tend to have pronounced (sometimes fatal) interactions with a wide variety of medications and over-the-counter drugs . If taken with foods that contain very high levels of tyramine (e.g., mature cheese, cured meats, or yeast extracts), they may cause

15326-454: The critical threshold and therefore do not result in an action potential. They can result from postsynaptic potentials from synchronous inputs or from intrinsic properties of neurons. Neuronal spiking can be classified by its activity pattern. The excitability of neurons can be subdivided in Class I and II. Class I neurons can generate action potentials with arbitrarily low frequency depending on

15484-474: The difference is modest and it is not clear that their statistical superiority results in clinical efficacy. The aggregate effect of antidepressants typically results in changes below the threshold of clinical significance on depression rating scales. Proponents of antidepressants counter that the most common scale, the HDRS , is not suitable for assessing drug action, that the threshold for clinical significance

15642-416: The doctor and patient, weighing the benefits and risks. In severe cases where seizures are uncontrolled by at least two anti-seizure medications, brain surgery can be a treatment option. Epilepsy surgery is especially useful for those with focal seizures where the seizures are coming from a specific part of the brain. The amount of brain removed during the surgery depends on the extent of the brain involved in

15800-549: The effects of serotonergic psychedelics like psilocybin and lysergic acid diethylamide (LSD). Among individuals treated with a given antidepressant, between 30% and 50% do not show a response. Approximately one-third of people achieve a full remission , one-third experience a response, and one-third are non-responders. Partial remission is characterized by the presence of poorly defined residual symptoms. These symptoms typically include depressed mood, anxiety, sleep disturbance, fatigue, and diminished interest or pleasure. It

15958-424: The efficacy of combining modafinil for treatment-resistant people. It has been used to help combat SSRI-associated fatigue. The effects of antidepressants typically do not continue once the course of medication ends. This results in a high rate of relapse . In 2003, a meta-analysis found that 18% of people who had responded to an antidepressant relapsed while still taking it, compared to 41% whose antidepressant

16116-516: The electric membrane potential. Neurons can generate multiple action potentials in sequence forming so-called spike trains. These spike trains are the basis for neural coding and information transfer in the brain. Spike trains can form all kinds of patterns, such as rhythmic spiking and bursting , and often display oscillatory activity. Oscillatory activity in single neurons can also be observed in sub-threshold fluctuations in membrane potential. These rhythmic changes in membrane potential do not reach

16274-451: The electrical characteristics of a neuron, including the generation and propagation of action potentials . The model is so successful at describing these characteristics that variations of its "conductance-based" formulation continue to be utilized in neuron models over a half a century later. The Hodgkin–Huxley model is too complicated to understand using classical mathematical techniques, so researchers often turn to simplifications such as

16432-829: The evidence supporting this association is of low quality. Bupropion is used to help people stop smoking . Antidepressants are also used to control some symptoms of narcolepsy . Antidepressants may be used to relieve pain in people with active rheumatoid arthritis . However, further research is required. Antidepressants have been shown to be superior to placebo in treating depression in individuals with physical illness, although reporting bias may have exaggerated this finding. Antidepressants have been shown to improve some parts of cognitive functioning for depressed users, such as memory, attention, and processing speed. Certain antidepressants acting as serotonin 5-HT 2A receptor antagonists, such as trazodone and mirtazapine , have been used as hallucinogen antidotes or "trip killers" to block

16590-414: The field, each defined at a different level of abstraction and trying to model different aspects of neural systems. They range from models of the short-term behaviour of individual neurons, through models of how the dynamics of neural circuitry arise from interactions between individual neurons, to models of how behaviour can arise from abstract neural modules that represent complete subsystems. A model of

16748-402: The firing rate of excitatory neurons. Neural oscillation can also arise from interactions between different brain areas coupled through the structural connectome . Time delays play an important role here. Because all brain areas are bidirectionally coupled, these connections between brain areas form feedback loops. Positive feedback loops tend to cause oscillatory activity where frequency

16906-448: The first two years. The greatest predictors of more seizures are problems either on the EEG or on imaging of the brain. Those with normal EEG and normal physical exam following a first unprovoked seizure had less of risk of recurrence in the next two years, with a risk of 25%. In adults, after 6 months of being seizure-free after a first seizure, the risk of a subsequent seizure in the next year

17064-399: The frequency of large-scale oscillations does not need to match the firing pattern of individual neurons. Isolated cortical neurons fire regularly under certain conditions, but in the intact brain, cortical cells are bombarded by highly fluctuating synaptic inputs and typically fire seemingly at random. However, if the probability of a large group of neurons firing is rhythmically modulated at

17222-537: The full effect of antidepressants. Additionally, the placebo effect might be inflated in these trials by frequent clinical consultation, lowering the comparative performance of antidepressants. Critics agree that current clinical trials are poorly-designed, which limits the knowledge on antidepressants. More naturalistic studies, such as STAR*D , have produced results, which suggest that antidepressants may be less effective in clinical practice than in randomized controlled trials. Critics of antidepressants maintain that

17380-434: The idea that low serotonin levels cause depression is not supported by scientific evidence. Proponents of the monoamine hypothesis of depression recommend choosing an antidepressant which impacts the most prominent symptoms. Under this practice, for example, a person with MDD who is also anxious or irritable would be treated with selective serotonin reuptake inhibitors (SSRIs) or norepinephrine reuptake inhibitors , while

17538-422: The input strength, whereas Class II neurons generate action potentials in a certain frequency band, which is relatively insensitive to changes in input strength. Class II neurons are also more prone to display sub-threshold oscillations in membrane potential. A group of neurons can also generate oscillatory activity. Through synaptic interactions, the firing patterns of different neurons may become synchronized and

17696-433: The integration of distributed information. Microglia  – the major immune cells of the brain – have been shown to play an important role in shaping network connectivity, and thus, influencing neuronal network oscillations both ex vivo and in vivo . In addition to fast direct synaptic interactions between neurons forming a network, oscillatory activity is regulated by neuromodulators on

17854-440: The intracellular currents that propagate forward and backward down the dendrites. Under this assumption, asymmetries in the dendritic current would cause asymmetries in oscillatory activity measured by EEG and MEG, since dendritic currents in pyramidal cells are generally thought to generate EEG and MEG signals that can be measured at the scalp. Cross-frequency coupling (CFC) describes the coupling (statistical correlation) between

18012-425: The lack of inhibition of neurons resulting in seizures. Glutamate serves to excite neurons into firing when appropriate. It was found to be increased in those with epilepsy.  This is a possible mechanism for why there is hyper-excitability of neurons in seizures. Seizures that occur after brain injury may be due to the brain adapting to injury ( neuroplasticity ). This process is known as epileptogenesis . There

18170-501: The medication, and less than half achieve remission . Placebo responses are a large component of the benefit of antidepressants in the treatment of depression and anxiety. However, placebo responses with antidepressants are lower in magnitude in the treatment of OCD compared to depression and anxiety. A 2019 meta-analysis found placebo improvement effect sizes (SMD) of about 1.2 for depression, 1.0 for anxiety disorders, and 0.6 for OCD with antidepressants. Antidepressants are one of

18328-481: The most effective class, with moderate effects on pain and sleep, and small effects on fatigue and health-related quality of life. The fraction of people experiencing a 30% pain reduction on tricyclics was 48%, versus 28% on placebo. For SSRIs and SNRIs, the fractions of people experiencing a 30% pain reduction were 36% (20% in the placebo comparator arms) and 42% (32% in the corresponding placebo comparator arms) respectively. Discontinuation of treatment due to side effects

18486-674: The motion of a pendulum , and vibrations of every sort. They generally arise when a physical system is perturbed by a small degree from a minimum-energy state , and are well understood mathematically. Noise-driven harmonic oscillators realistically simulate alpha rhythm in the waking EEG as well as slow waves and spindles in the sleep EEG. Successful EEG analysis algorithms were based on such models. Several other EEG components are better described by limit-cycle or delayed-feedback oscillations. Limit-cycle oscillations arise from physical systems that show large deviations from equilibrium , whereas delayed-feedback oscillations arise when components of

18644-424: The mouth, and turning blue due to inability to breathe commonly are seen in seizures. A period of confusion typically follows the seizure that lasts from seconds to hours before a person returns to normal. This period is called a postictal period . Other symptoms during this period include drowsiness, headache, difficulty speaking, psychosis, and weakness. Observable signs and symptoms of seizures vary depending on

18802-622: The newborn to epilepsy. Strokes, brain bleeds, and traumatic brain injury can all also lead to epilepsy if seizures re-occur. If the first seizure occurs more than 7 days following a stroke, there is a higher chance of the person developing epilepsy. Post-stroke epilepsy accounts for 30%-50% of new epilepsy cases. This is also the case for traumatic brain injury, with 80% of people with late posttraumatic seizures having another seizure occur, classifying it as epilepsy. Infections of newborns that occur while before or during birth, such as herpes simplex virus , rubella , and cytomegalovirus , all carry

18960-405: The newer anticonvulsants . A combination strategy involves adding another antidepressant, usually from a different class to affect other mechanisms. Although this may be used in clinical practice, there is little evidence for the relative efficacy or adverse effects of this strategy. Other tests conducted include the use of psychostimulants as an augmentation therapy. Several studies have shown

19118-433: The person is not fully conscious and alert, they should be turned to their side to prevent choking. This is called recovery position . Timing of the seizure is also important. If a seizure is longer than five minutes, or there are two or more seizures occurring in five minutes, it is a medical emergency known as status epilepticus . Emergency services should be called. The first line medication for an actively seizing person

19276-529: The person returns to normal. If a seizure lasts longer than 5 minutes, it is a medical emergency ( status epilepticus ) and needs immediate treatment. Seizures can be classified as provoked or unprovoked. Provoked seizures have a cause that can be fixed, such as low blood sugar , alcohol withdrawal , high fever , recent stroke , and recent head trauma . Unprovoked seizures have no clear cause or fixable cause. Examples include past strokes, brain tumors, brain vessel malformations, and genetic disorders. If no cause

19434-519: The physiological state, e.g., wakefulness or arousal , and have a pronounced effect on amplitude of different brain waves, such as alpha activity. Oscillations can often be described and analyzed using mathematics. Mathematicians have identified several dynamical mechanisms that generate rhythmicity. Among the most important are harmonic (linear) oscillators, limit cycle oscillators, and delayed- feedback oscillators. Harmonic oscillations appear very frequently in nature—examples are sound waves,

19592-664: The placebo effect may account for most or all of the drugs' observed efficacy. Research on the effectiveness of antidepressants is generally done on people who have severe symptoms, a population that exhibits much weaker placebo responses, meaning that the results may not be extrapolated to the general population that has not (or has not yet) been diagnosed with anxiety or depression. Antidepressants are prescribed to treat major depressive disorder (MDD), anxiety disorders , chronic pain , and some addictions. Antidepressants are often used in combination with one another. Despite its longstanding prominence in pharmaceutical advertising,

19750-563: The potential to serve as pacemakers for synchronous network oscillations, and bursts of spikes may underlie or enhance neuronal resonance. Many of these neurons can be considered intrinsic oscillators, namely, neurons that generate their oscillations intrinsically, as their oscillation frequencies can be modified by local applications of glutamate in-vivo. Apart from intrinsic properties of neurons, biological neural network properties are also an important source of oscillatory activity. Neurons communicate with one another via synapses and affect

19908-429: The presentation of a stimulus. As a consequence, those signal components that are the same in each single measurement are conserved and all others, i.e. ongoing or spontaneous activity, are averaged out. That is, event-related potentials only reflect oscillations in brain activity that are phase -locked to the stimulus or event. Evoked activity is often considered to be independent from ongoing brain activity, although this

20066-534: The rhythmic changes in electric potential caused by their action potentials may accumulate ( constructive interference ). That is, synchronized firing patterns result in synchronized input into other cortical areas, which gives rise to large-amplitude oscillations of the local field potential . These large-scale oscillations can also be measured outside the scalp using electroencephalography (EEG) and magnetoencephalography (MEG). The electric potentials generated by single neurons are far too small to be picked up outside

20224-433: The risk for relapse . Antidepressants can cause various adverse effects , depending on the individual and the drug in question. Almost any medication involved with serotonin regulation has the potential to cause serotonin toxicity (also known as serotonin syndrome ) – an excess of serotonin that can induce mania, restlessness, agitation, emotional lability , insomnia, and confusion as its primary symptoms. Although

20382-709: The risk of relapse and that SSRIs are typically better tolerated than other antidepressants. American Psychiatric Association (APA) treatment guidelines recommend that initial treatment be individually tailored based on factors including the severity of symptoms, co-existing disorders, prior treatment experience, and the person's preference. Options may include antidepressants, psychotherapy , electroconvulsive therapy (ECT), transcranial magnetic stimulation (TMS), or light therapy . The APA recommends antidepressant medication as an initial treatment choice in people with mild, moderate, or severe major depression, and that should be given to all people with severe depression unless ECT

20540-459: The same class, and then to a different class. A 2006 meta-analysis review found wide variation in the findings of prior studies: for people who had failed to respond to an SSRI antidepressant, between 12% and 86% showed a response to a new drug. However, the more antidepressants an individual had previously tried, the less likely they were to benefit from a new antidepressant trial. However, a later meta-analysis found no difference between switching to

20698-486: The scalp, and EEG or MEG activity always reflects the summation of the synchronous activity of thousands or millions of neurons that have similar spatial orientation. Neurons in a neural ensemble rarely all fire at exactly the same moment, i.e. fully synchronized. Instead, the probability of firing is rhythmically modulated such that neurons are more likely to fire at the same time, which gives rise to oscillations in their mean activity. (See figure at top of page.) As such,

20856-412: The seizures. It can range from just removing one lobe of the brain ( temporal lobectomy ) to disconnecting an entire side of the brain ( hemispherectomy ). The procedure can be curative, where seizures are eliminated completely. However, if it is not curative, it can be palliative that reduces the frequency of seizures but does not eliminate it. Helmets may be used to provide protection to the head during

21014-446: The so-called drug-induced QT prolongation , especially in older adults; this condition can degenerate into a specific type of abnormal heart rhythm called Torsades de points , which can potentially lead to sudden cardiac arrest . Some antidepressants are also believed to increase thoughts of suicidal ideation . Antidepressants have been associated with an increased risk of dementia in older adults. Researchers have developed

21172-669: The strength of neural oscillations in recorded data. Neural oscillations are commonly studied within a mathematical framework and belong to the field of "neurodynamics", an area of research in the cognitive sciences that places a strong focus on the dynamic character of neural activity in describing brain function. It considers the brain a dynamical system and uses differential equations to describe how neural activity evolves over time. In particular, it aims to relate dynamic patterns of brain activity to cognitive functions such as perception and memory. In very abstract form, neural oscillations can be analyzed analytically . When studied in

21330-747: The summed activity it receives. Frequency changes are also commonly observed in central pattern generators and directly relate to the speed of motor activities , such as step frequency in walking. However, changes in relative oscillation frequency between different brain areas is not so common because the frequency of oscillatory activity is often related to the time delays between brain areas. Next to evoked activity, neural activity related to stimulus processing may result in induced activity. Induced activity refers to modulation in ongoing brain activity induced by processing of stimuli or movement preparation. Hence, they reflect an indirect response in contrast to evoked responses. A well-studied type of induced activity

21488-591: The superiority of antidepressants over placebo is the result of systemic flaws in clinical trials and the research literature. Trials conducted with industry involvement tend to produce more favorable results, and accordingly many of the trials included in meta-analyses are at high risk of bias. Additionally, meta-analyses co-authored by industry employees find more favorable results for antidepressants. The results of antidepressant trials are significantly more likely to be published if they are favorable, and unfavorable results are very often left unpublished or misreported,

21646-429: The synchronization of neural activity, for instance by synchronization of spike timing or membrane potential fluctuations of individual neurons. Increases in oscillatory activity are therefore often referred to as event-related synchronization, while decreases are referred to as event-related desynchronization. Phase resetting occurs when input to a neuron or neuronal ensemble resets the phase of ongoing oscillations. It

21804-522: The tendency to fire at particular frequencies, either as resonators or as intrinsic oscillators . Bursting is another form of rhythmic spiking. Spiking patterns are considered fundamental for information coding in the brain. Oscillatory activity can also be observed in the form of subthreshold membrane potential oscillations (i.e. in the absence of action potentials). If numerous neurons spike in synchrony , they can give rise to oscillations in local field potentials . Quantitative models can estimate

21962-613: The timing of spike trains in the post-synaptic neurons. Depending on the properties of the connection, such as the coupling strength, time delay and whether coupling is excitatory or inhibitory , the spike trains of the interacting neurons may become synchronized . Neurons are locally connected, forming small clusters that are called neural ensembles . Certain network structures promote oscillatory activity at specific frequencies. For example, neuronal activity generated by two populations of interconnected inhibitory and excitatory cells can show spontaneous oscillations that are described by

22120-479: The timing of spikes can become phase locked to the activity of other neurons. Phase resetting also permits the study of evoked activity, a term used in electroencephalography and magnetoencephalography for responses in brain activity that are directly related to stimulus -related activity. Evoked potentials and event-related potentials are obtained from an electroencephalogram by stimulus-locked averaging, i.e. averaging different trials at fixed latencies around

22278-610: The treatment of bulimia nervosa . SSRIs (fluoxetine in particular) are preferred over other antidepressants due to their acceptability, tolerability, and superior reduction of symptoms in short-term trials. Long-term efficacy remains poorly characterized. Bupropion is not recommended for the treatment of eating disorders, due to an increased risk of seizure. Similar recommendations apply to binge eating disorder . SSRIs provide short-term reductions in binge eating behavior, but have not been associated with significant weight loss. Clinical trials have generated mostly negative results for

22436-605: The treatment of neuropathic pain and found limited useful randomized clinical trial data. They concluded that the long history of successful use in the community for the treatment of fibromyalgia and neuropathic pain justified its continued use. The group was concerned about the potential overestimation of the amount of pain relief provided by amitriptyline, and highlighted that only a small number of people will experience significant pain relief by taking this medication. Antidepressants may be modestly helpful for treating people who have both depression and alcohol dependence , however,

22594-407: The treatment of anxiety disorders of around 0.3, which equates to a small improvement and is roughly the same magnitude of benefit as their effectiveness in the treatment of depression. The effect size (SMD) for improvement with placebo in trials of antidepressants for anxiety disorders is approximately 1.0, which is a large improvement in terms of effect size definitions. In relation to this, most of

22752-485: The treatment options for PTSD . However, their efficacy is not well established. Paroxetine and sertraline have been FDA approved for the treatment of PTSD. Paroxetine has slightly higher response and remission rates than sertraline for this condition. However, neither drug is considered very helpful for a broad patient demographic. Fluoxetine and venlafaxine are used off-label. Fluoxetine has produced unsatisfactory mixed results. Venlafaxine showed response rates of 78%, which

22910-547: The two maintains our central nervous system. In those with seizures, neurons are both hyperexcitable and hypersynchronous, where many neurons fire numerously at the same time. This may be due to an imbalance of excitation and inhibition of neurons. γ-aminobutyric acid (GABA) and Glutamate are chemicals called neurotransmitters that work by opening or closing ion channels on neurons to cause inhibition or excitability. GABA serves to inhibit neurons from firing. It has been found to be decreased in epilepsy patients. This may explain

23068-434: The type of seizure or epilepsy syndrome present, as well as where the seizures are coming from if its focal. It is also used when a person has not returned to baseline after a seizure for a prolonged time. Other conditions that commonly get mistaken for a seizure include syncope , psychogenic nonepileptic seizures , cardiac arrhythmias , migraine headaches , and stroke / transient ischemic attacks . There are times when

23226-701: The type of seizure. The person's memory of what happened before and during the seizure is also important. However, since most people that experience seizures do not remember what happened, it is best to get history from a witness when possible. Video recording of the seizure is also helpful in diagnosis of seizures. Events that occurred after the seizure are also an important part of the history. Past medical history, such as past head trauma, past strokes, past febrile seizures, or past infections, are helpful. In babies and children, information about developmental milestones, birth history, and previous illnesses are important as potential epilepsy risk factors. Family history of seizures

23384-407: The type. Seizures can be classified into generalized seizures and focal seizures, depending on what part of the brain is involved. Focal seizures affect a specific area of the brain, not both sides. It may turn into a generalized seizure if the seizure spreads through the brain. Consciousness may or may not be impaired. The signs and symptoms of these seizures depends on the location of the brain that

23542-613: The use of SSRIs in the treatment of anorexia nervosa . Treatment guidelines from the National Institute of Health and Care Excellence (NICE) recommend against the use of SSRIs in this disorder. Those from the American Psychiatric Association (APA) note that SSRIs confer no advantage regarding weight gain, but may be used for the treatment of co-existing depressive, anxiety, or obsessive–compulsive disorders. A 2012 meta-analysis concluded that antidepressant treatment favorably affects pain, health-related quality of life, depression, and sleep in fibromyalgia syndrome. Tricyclics appear to be

23700-905: The well-established Hodgkin–Huxley model that describes how action potentials are initiated and propagated by means of a set of differential equations. Using bifurcation analysis , different oscillatory varieties of these neuronal models can be determined, allowing for the classification of types of neuronal responses. The oscillatory dynamics of neuronal spiking as identified in the Hodgkin–Huxley model closely agree with empirical findings. In addition to periodic spiking, subthreshold membrane potential oscillations , i.e. resonance behavior that does not result in action potentials, may also contribute to oscillatory activity by facilitating synchronous activity of neighboring neurons. Like pacemaker neurons in central pattern generators , subtypes of cortical cells fire bursts of spikes (brief clusters of spikes) rhythmically at preferred frequencies. Bursting neurons have

23858-450: The widespread use of antidepressants is not evidence-based. They also note that adverse effects, including withdrawal difficulties, are likely underreported, skewing clinicians' ability to make risk-benefit judgements. Accordingly, they believe antidepressants are overused, particularly for non-severe depression and conditions in which they are not indicated. Critics charge that the widespread use and public acceptance of antidepressants

24016-492: The work of " evil spirits ". The perception of epilepsy, however, began to change in the time of Ancient Greek medicine. The term "epilepsy" itself is a Greek word, which is derived from the verb "epilambanein", meaning "to seize, possess, or afflict". Although the Ancient Greeks referred to epilepsy as the " sacred disease ", this perception of epilepsy as a "spiritual" disease was challenged by Hippocrates in his work On

24174-645: Was common. Antidepressants including amitriptyline , fluoxetine, duloxetine, milnacipran , moclobemide , and pirlindole are recommended by the European League Against Rheumatism (EULAR) for the treatment of fibromyalgia based on "limited evidence". A 2014 meta-analysis from the Cochrane Collaboration found the antidepressant duloxetine to be effective for the treatment of pain resulting from diabetic neuropathy . The same group reviewed data for amitriptyline in

24332-486: Was encountered in vertebrate neurons, but its functional role is still not fully understood. The possible roles of neural oscillations include feature binding , information transfer mechanisms and the generation of rhythmic motor output . Over the last decades more insight has been gained, especially with advances in brain imaging . A major area of research in neuroscience involves determining how oscillations are generated and what their roles are. Oscillatory activity in

24490-408: Was shown that simulations of neural networks with a phenomenological model for neuronal response failures can predict spontaneous broadband neural oscillations. Neural field models are another important tool in studying neural oscillations and are a mathematical framework describing evolution of variables such as mean firing rate in space and time. In modeling the activity of large numbers of neurons,

24648-510: Was shown to be a good treatment option, but its use is limited by dietary restrictions. Moclobemide is a RIMA and showed mixed results, but still received approval in some European countries for social anxiety disorder. TCA antidepressants , such as clomipramine and imipramine , are not considered effective for this anxiety disorder in particular. This leaves out SSRIs such as paroxetine, sertraline, and fluvoxamine CR as acceptable and tolerated treatment options for this disorder. SSRIs are

24806-536: Was switched for a placebo . A gradual loss of therapeutic benefit occurs in a minority of people during the course of treatment. A strategy involving the use of pharmacotherapy in the treatment of the acute episode, followed by psychotherapy in its residual phase, has been suggested by some studies. For patients who wish to stop their antidepressants, engaging in brief psychological interventions such as Preventive Cognitive Therapy or mindfulness-based cognitive therapy while tapering down has been found to diminish

24964-545: Was that of the development by the Montreal procedure by Canadian neurosurgeon Wilder Penfield , which involved use of electrical stimulation among conscious patients to more accurately identify and resect the epileptic areas in the brain. Seizures result in direct economic costs of about one billion dollars in the United States. Epilepsy results in economic costs in Europe of around €15.5 billion in 2004. In India, epilepsy

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