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96-659: Sensation (psychology) refers to the processing of the senses by the sensory system. Sensation or sensations may also refer to: Sensation (psychology) A sense is a biological system used by an organism for sensation , the process of gathering information about the surroundings through the detection of stimuli . Although, in some cultures, five human senses were traditionally identified as such (namely sight , smell , touch , taste , and hearing ), many more are now recognized. Senses used by non-human organisms are even greater in variety and number. During sensation, sense organs collect various stimuli (such as

192-465: A central point. An example would be when we use parentheses in writing. We tend to perceive all of the words in the parentheses as one section instead of individual words within the parentheses. The Law of Continuity tells us that objects are grouped together by their elements and then perceived as a whole. This usually happens when we see overlapping objects. We will see the overlapping objects with no interruptions. The Law of Past Experience refers to

288-429: A fluid wave driven by pressure across the basilar membrane separating two of the sections. Strikingly, one section, called the cochlear duct or scala media , contains endolymph . The organ of Corti is located in this duct on the basilar membrane, and transforms mechanical waves to electric signals in neurons. The other two sections are known as the scala tympani and the scala vestibuli . These are located within

384-403: A group, but we can also perceive three groups of two lines with seven objects in each line. The Law of Closure is the idea that we as humans still see a full picture even if there are gaps within that picture. There could be gaps or parts missing from a section of a shape, but we would still perceive the shape as whole. The Law of Symmetry refers to a person's preference to see symmetry around

480-485: A human), close your eyes (preferably in a dark room) and press gently on the outside corner of one eye through the eyelid. You will see a visual spot toward the inside of your visual field, near your nose.) All stimuli received by the receptors are transduced to an action potential , which is carried along one or more afferent neurons towards a specific area ( cortex ) of the brain . Just as different nerves are dedicated to sensory and motors tasks, different areas of

576-586: A materialistic view of the mind. Some examples of human absolute thresholds for the nine to 21 external senses . Humans respond more strongly to multimodal stimuli compared to the sum of each single modality together, an effect called the superadditive effect of multisensory integration . Neurons that respond to both visual and auditory stimuli have been identified in the superior temporal sulcus . Additionally, multimodal "what" and "where" pathways have been proposed for auditory and tactile stimuli. External receptors that respond to stimuli from outside

672-495: A mechanoreceptor. Photoreceptors convert light (visible electromagnetic radiation ) into signals. Chemical stimuli can be interpreted by a chemoreceptor that interprets chemical stimuli, such as an object's taste or smell, while osmoreceptors respond to a chemical solute concentrations of body fluids. Nociception (pain) interprets the presence of tissue damage, from sensory information from mechano-, chemo-, and thermoreceptors. Another physical stimulus that has its own type of receptor

768-427: A panoply of auditory reactions and sensations. Hair cells are columnar cells, each with a "hair bundle" of 100–200 specialized stereocilia at the top, for which they are named. There are two types of hair cells specific to the auditory system; inner and outer hair cells . Inner hair cells are the mechanoreceptors for hearing: they transduce the vibration of sound into electrical activity in nerve fibers , which

864-468: A particular color . Visible light is electromagnetic radiation with a wavelength between 380 and 720 nm. Wavelengths of electromagnetic radiation longer than 720 nm fall into the infrared range, whereas wavelengths shorter than 380 nm fall into the ultraviolet range. Light with a wavelength of 380 nm is blue whereas light with a wavelength of 720 nm is dark red . All other colors fall between red and blue at various points along

960-471: A respective visual system (sense of vision), auditory system (sense of hearing), somatosensory system (sense of touch), olfactory system (sense of smell), and gustatory system (sense of taste). Those systems, in turn, contribute to vision , hearing , touch , smell , and the ability to taste . Internal sensation, or interoception, detects stimuli from internal organs and tissues. Many internal sensory and perceptual systems exist in humans, including

1056-439: A sense, but it is generally regarded as a cognitive (that is, post-sensory) function of the visual cortex of the brain where patterns and objects in images are recognized and interpreted based on previously learned information. This is called visual memory . The inability to see is called blindness . Blindness may result from damage to the eyeball, especially to the retina, damage to the optic nerve that connects each eye to

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1152-498: A series of tiny bones to hair-like fibers in the inner ear , which detect mechanical motion of the fibers within a range of about 20 to 20,000  hertz , with substantial variation between individuals. Hearing at high frequencies declines with an increase in age. Inability to hear is called deafness or hearing impairment. Sound can also be detected as vibrations conducted through the body. Lower frequencies that can be heard are detected this way. Some deaf people are able to determine

1248-416: A sound or smell) for transduction , meaning transformation into a form that can be understood by the brain. Sensation and perception are fundamental to nearly every aspect of an organism's cognition , behavior and thought . In organisms, a sensory organ consists of a group of interrelated sensory cells that respond to a specific type of physical stimulus. Via cranial and spinal nerves (nerves of

1344-478: A specific type of stimulus. For example, the general sensation and perception of touch, which is known as somatosensation, can be separated into light pressure, deep pressure, vibration, itch, pain, temperature, or hair movement, while the general sensation and perception of taste can be separated into submodalities of sweet , salty , sour , bitter , spicy, and umami , all of which are based on different chemicals binding to sensory neurons . Sensory receptors are

1440-662: A stimulus is constant and unchanging, perceptual sensory adaptation occurs. During that process, the subject becomes less sensitive to the stimulus. Biological auditory (hearing), vestibular and spatial, and visual systems (vision) appear to break down real-world complex stimuli into sine wave components, through the mathematical process called Fourier analysis. Many neurons have a strong preference for certain sine frequency components in contrast to others. The way that simpler sounds and images are encoded during sensation can provide insight into how perception of real-world objects happens. Perception occurs when nerves that lead from

1536-669: A stronger sense of smell than humans. Some animal species lack one or more human sensory system analogues and some have sensory systems that are not found in humans, while others process and interpret the same sensory information in very different ways. For example, some animals are able to detect electrical fields and magnetic fields , air moisture , or polarized light . Others sense and perceive through alternative systems such as echolocation . Recent theory suggests that plants and artificial agents such as robots may be able to detect and interpret environmental information in an analogous manner to animals. Sensory modality refers to

1632-752: Is a barrier between scalae, along the edge of which the IHCs and OHCs sit. Basilar membrane width and stiffness vary to control the frequencies best sensed by the IHC. At the cochlear base the BM is at its narrowest and most stiff (high-frequencies), while at the cochlear apex it is at its widest and least stiff (low-frequencies). The tectorial membrane (TM) helps facilitate cochlear amplification by stimulating OHC (direct) and IHC (via endolymph vibrations). TM width and stiffness parallels BM's and similarly aids in frequency differentiation. The superior olivary complex (SOC), in

1728-432: Is a bundle of decussating fibers in the ventral pons that carry information used for binaural computations in the brainstem. Some of these axons come from the cochlear nucleus and cross over to the other side before traveling on to the superior olivary nucleus. This is believed to help with localization of sound . The superior olivary complex is located in the pons , and receives projections predominantly from

1824-411: Is a molecule called propylthiouracil (PROP) that some humans experience as bitter, some as almost tasteless, while others experience it as somewhere between tasteless and bitter. There is a genetic basis for this difference between perception given the same sensory stimulus. This subjective difference in taste perception has implications for individuals' food preferences, and consequently, health. When

1920-429: Is a perception resulting from activation of neural receptors , generally in the skin including hair follicles , but also in the tongue , throat , and mucosa . A variety of pressure receptors respond to variations in pressure (firm, brushing, sustained, etc.). The touch sense of itching caused by insect bites or allergies involves special itch-specific neurons in the skin and spinal cord. The loss or impairment of

2016-568: Is a tract of axons in the brainstem that carries information about sound from the cochlear nucleus to various brainstem nuclei and ultimately the contralateral inferior colliculus of the midbrain . The inferior colliculi (IC) are located just below the visual processing centers known as the superior colliculi . The central nucleus of the IC is a nearly obligatory relay in the ascending auditory system, and most likely acts to integrate information (specifically regarding sound source localization from

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2112-564: Is an approximately exponential function of the length of the cochlea within the Organ of Corti . In some species, such as bats and dolphins, the relationship is expanded in specific areas to support their active sonar capability. The organ of Corti forms a ribbon of sensory epithelium which runs lengthwise down the cochlea's entire scala media . Its hair cells transform the fluid waves into nerve signals. The journey of countless nerves begins with this first step; from here, further processing leads to

2208-401: Is associated with the left posterior superior temporal gyrus (STG). The superior temporal gyrus contains several important structures of the brain, including Brodmann areas 41 and 42, marking the location of the primary auditory cortex , the cortical region responsible for the sensation of basic characteristics of sound such as pitch and rhythm. We know from research in nonhuman primates that

2304-482: Is attached to the tympanic membrane and articulates with the incus. The incus, in turn, articulates with the stapes. The stapes is then attached to the inner ear , where the sound waves will be transduced into a neural signal. The middle ear is connected to the pharynx through the Eustachian tube , which helps equilibrate air pressure across the tympanic membrane. The tube is normally closed but will pop open when

2400-438: Is based on their location relative to the stimuli. An exteroceptor is a receptor that is located near a stimulus of the external environment, such as the somatosensory receptors that are located in the skin. An interoceptor is one that interprets stimuli from internal organs and tissues, such as the receptors that sense the increase in blood pressure in the aorta or carotid sinus . The cells that interpret information about

2496-489: Is concerned with the nature of perceptual experience and the status of perceptual data , in particular how they relate to beliefs about, or knowledge of, the world. Historical inquiries into the underlying mechanisms of sensation and perception have led early researchers to subscribe to various philosophical interpretations of perception and the mind , including panpsychism , dualism , and materialism . The majority of modern scientists who study sensation and perception take on

2592-431: Is dedicated to the auditory system . The main point is to understand why humans are able to use sound in thinking outside of actually saying it. Relating to auditory cognitive psychology is psychoacoustics . Psychoacoustics is more directed at people interested in music. Haptics , a word used to refer to both taction and kinesthesia, has many parallels with psychoacoustics. Most research around these two are focused on

2688-465: Is described by Steven's power law . Signal detection theory quantifies the experience of the subject to the presentation of a stimulus in the presence of noise . There is internal noise and there is external noise when it comes to signal detection. The internal noise originates from static in the nervous system. For example, an individual with closed eyes in a dark room still sees something—a blotchy pattern of grey with intermittent brighter flashes—this

2784-549: Is encoded or transduced. Multimodality integrates different senses into one unified perceptual experience. For example, information from one sense has the potential to influence how information from another is perceived. Sensation and perception are studied by a variety of related fields, most notably psychophysics , neurobiology , cognitive psychology , and cognitive science . Sensory organs are organs that sense and transduce stimuli. Humans have various sensory organs (i.e. eyes, ears, skin, nose, and mouth) that correspond to

2880-480: Is heavily involved in emotion-sound, emotion-facial-expression, and sound-memory processes. The entorhinal cortex is the part of the 'hippocampus system' that aids and stores visual and auditory memories. The supramarginal gyrus (SMG) aids in language comprehension and is responsible for compassionate responses. SMG links sounds to words with the angular gyrus and aids in word choice. SMG integrates tactile, visual, and auditory info. The folds of cartilage surrounding

2976-410: Is internal noise. External noise is the result of noise in the environment that can interfere with the detection of the stimulus of interest. Noise is only a problem if the magnitude of the noise is large enough to interfere with signal collection. The nervous system calculates a criterion, or an internal threshold, for the detection of a signal in the presence of noise. If a signal is judged to be above

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3072-425: Is often multimodal. Multimodality integrates different senses into one unified perceptual experience. Information from one sense has the potential to influence how information from another is perceived. Multimodal perception is qualitatively different from unimodal perception. There has been a growing body of evidence since the mid-1990s on the neural correlates of multimodal perception. The philosophy of perception

3168-594: Is seen into patterns or groups: Common Fate, Similarity, Proximity, Closure, Symmetry, Continuity, and Past Experience. The Law of Common fate says that objects are led along the smoothest path. People follow the trend of motion as the lines/dots flow. The Law of Similarity refers to the grouping of images or objects that are similar to each other in some aspect. This could be due to shade, colour, size, shape, or other qualities you could distinguish. The Law of Proximity states that our minds like to group based on how close objects are to each other. We may see 42 objects in

3264-496: Is surrounded by secondary auditory cortex, and interconnects with it. These secondary areas interconnect with further processing areas in the superior temporal gyrus , in the dorsal bank of the superior temporal sulcus , and in the frontal lobe . In humans, connections of these regions with the middle temporal gyrus are probably important for speech perception . The frontotemporal system underlying auditory perception allows us to distinguish sounds as speech, music, or noise. From

3360-428: Is temperature, which is sensed through a thermoreceptor that is either sensitive to temperatures above (heat) or below (cold) normal body temperature. Each sense organ (eyes or nose, for instance) requires a minimal amount of stimulation in order to detect a stimulus. This minimum amount of stimulus is called the absolute threshold. The absolute threshold is defined as the minimum amount of stimulation necessary for

3456-455: Is the first site of the neuronal processing of the newly converted "digital" data from the inner ear (see also binaural fusion ). In mammals, this region is anatomically and physiologically split into two regions, the dorsal cochlear nucleus (DCN), and ventral cochlear nucleus (VCN). The VCN is further divided by the nerve root into the posteroventral cochlear nucleus (PVCN) and the anteroventral cochlear nucleus (AVCN). The trapezoid body

3552-523: Is the sensation of potentially damaging stimuli. Mechanical, chemical, or thermal stimuli beyond a set threshold will elicit painful sensations. Stressed or damaged tissues release chemicals that activate receptor proteins in the nociceptors. For example, the sensation of heat associated with spicy foods involves capsaicin , the active molecule in hot peppers. Low frequency vibrations are sensed by mechanoreceptors called Merkel cells , also known as type I cutaneous mechanoreceptors. Merkel cells are located in

3648-449: Is transmitted to the brain. Outer hair cells are a motor structure. Sound energy causes changes in the shape of these cells, which serves to amplify sound vibrations in a frequency specific manner. Lightly resting atop the longest cilia of the inner hair cells is the tectorial membrane , which moves back and forth with each cycle of sound, tilting the cilia, which is what elicits the hair cells' electrical responses. Inner hair cells, like

3744-489: The cell membrane that mediates a physiological change in a neuron, most often through the opening of ion channels or changes in the cell signaling processes. Transmembrane receptors are activated by chemicals called ligands . For example, a molecule in food can serve as a ligand for taste receptors. Other transmembrane proteins, which are not accurately called receptors, are sensitive to mechanical or thermal changes. Physical changes in these proteins increase ion flow across

3840-524: The cochlea via the oval window , which vibrates the perilymph liquid (present throughout the inner ear ) and causes the round window to bulb out as the oval window bulges in. Vestibular and tympanic ducts are filled with perilymph, and the smaller cochlear duct between them is filled with endolymph , a fluid with a very different ion concentration and voltage. Vestibular duct perilymph vibrations bend organ of Corti outer cells (4 lines) causing prestin to be released in cell tips. This causes

3936-413: The oval window or vestibular window. The manubrium (handle) of the malleus articulates with the tympanic membrane, while the footplate (base) of the stapes articulates with the oval window. Higher pressure is necessary at the oval window than at the tympanic membrane because the inner ear beyond the oval window contains liquid rather than air. The stapedius reflex of the middle ear muscles helps protect

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4032-418: The photoreceptor cells of the eye, show a graded response , instead of the spikes typical of other neurons. These graded potentials are not bound by the "all or none" properties of an action potential. At this point, one may ask how such a wiggle of a hair bundle triggers a difference in membrane potential. The current model is that cilia are attached to one another by " tip links ", structures which link

4128-413: The pons , is the first convergence of the left and right cochlear pulses. SOC has 14 described nuclei; their abbreviation are used here (see Superior olivary complex for their full names). MSO determines the angle the sound came from by measuring time differences in left and right info. LSO normalizes sound levels between the ears; it uses the sound intensities to help determine sound angle. LSO innervates

4224-410: The sensory organs (e.g. eye) to the brain are stimulated, even if that stimulation is unrelated to the target signal of the sensory organ. For example, in the case of the eye, it does not matter whether light or something else stimulates the optic nerve, that stimulation will results in visual perception, even if there was no visual stimulus to begin with. (To prove this point to yourself (and if you are

4320-433: The stratum basale of the epidermis . Deep pressure and vibration is transduced by lamellated ( Pacinian ) corpuscles, which are receptors with encapsulated endings found deep in the dermis, or subcutaneous tissue. Light touch is transduced by the encapsulated endings known as tactile ( Meissner ) corpuscles. Follicles are also wrapped in a plexus of nerve endings known as the hair follicle plexus. These nerve endings detect

4416-450: The superior olivary complex and dorsal cochlear nucleus ) before sending it to the thalamus and cortex . The inferior colliculus also receives descending inputs from the auditory cortex and auditory thalamus (or medial geniculate nucleus ). The medial geniculate nucleus is part of the thalamic relay system. The primary auditory cortex is the first region of cerebral cortex to receive auditory input. Perception of sound

4512-594: The vestibular system (sense of balance) sensed by the inner ear and providing the perception of spatial orientation ; proprioception (body position); and nociception (pain). Further internal chemoreception - and osmoreception -based sensory systems lead to various perceptions, such as hunger , thirst , suffocation , and nausea , or different involuntary behaviors, such as vomiting . Nonhuman animals experience sensation and perception, with varying levels of similarity to and difference from humans and other animal species. For example, other mammals in general have

4608-416: The "blue" cones predominantly. The relative activation of the three different cones is calculated by the brain, which perceives the color as blue. However, cones cannot react to low-intensity light, and rods do not sense the color of light. Therefore, our low-light vision is—in essence—in grayscale . In other words, in a dark room, everything appears as a shade of gray . If you think that you can see colors in

4704-678: The Central and Peripheral nervous systems that relay sensory information to and from the brain and body), the different types of sensory receptor cells (such as mechanoreceptors , photoreceptors , chemoreceptors , thermoreceptors ) in sensory organs transduct sensory information from these organs towards the central nervous system, finally arriving at the sensory cortices in the brain , where sensory signals are processed and interpreted (perceived). Sensory systems, or senses, are often divided into external (exteroception) and internal ( interoception ) sensory systems. Human external senses are based on

4800-400: The IHC. VNTB innervate OHC. MNTB inhibit LSO via glycine. LNTB are glycine-immune, used for fast signalling. DPO are high-frequency and tonotopical. DLPO are low-frequency and tonotopical. VLPO have the same function as DPO, but act in a different area. PVO, CPO, RPO, VMPO, ALPO and SPON (inhibited by glycine) are various signalling and inhibiting nuclei. The trapezoid body is where most of

4896-618: The ability to feel anything touched is called tactile anesthesia . Paresthesia is a sensation of tingling, pricking, or numbness of the skin that may result from nerve damage and may be permanent or temporary. Two types of somatosensory signals that are transduced by free nerve endings are pain and temperature. These two modalities use thermoreceptors and nociceptors to transduce temperature and pain stimuli, respectively. Temperature receptors are stimulated when local temperatures differ from body temperature . Some thermoreceptors are sensitive to just cold and others to just heat. Nociception

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4992-522: The auditory system is required to able to sense, process, and understand sound from the surroundings. Difficulty in sensing, processing and understanding sound input has the potential to adversely impact an individual's ability to communicate, learn and effectively complete routine tasks on a daily basis. In children, early diagnosis and treatment of impaired auditory system function is an important factor in ensuring that key social, academic and speech/language developmental milestones are met. Impairment of

5088-398: The basilar membrane supplying the inputs to a particular afferent nerve fibre can be considered to be its receptive field . Efferent projections from the brain to the cochlea also play a role in the perception of sound, although this is not well understood. Efferent synapses occur on outer hair cells and on afferent (towards the brain) dendrites under inner hair cells The cochlear nucleus

5184-404: The basis of the type of stimuli they transduce. The different types of functional receptor cell types are mechanoreceptors , photoreceptors , chemoreceptors ( osmoreceptor ), thermoreceptors , electroreceptors (in certain mammals and fish), and nociceptors . Physical stimuli, such as pressure and vibration, as well as the sensation of sound and body position (balance), are interpreted through

5280-415: The basis of three different criteria: cell type , position, and function. Receptors can be classified structurally on the basis of cell type and their position in relation to stimuli they sense. Receptors can further be classified functionally on the basis of the transduction of stimuli, or how the mechanical stimulus, light, or chemical changed the cell membrane potential . One way to classify receptors

5376-450: The beginning of the middle ear . Sound waves travel through the ear canal and hit the tympanic membrane, or eardrum . This wave information travels across the air-filled middle ear cavity via a series of delicate bones: the malleus (hammer), incus (anvil) and stapes (stirrup). These ossicles act as a lever, converting the lower-pressure eardrum sound vibrations into higher-pressure sound vibrations at another, smaller membrane called

5472-460: The best temporal precision while firing, they decode the auditory timing code. The DCN has 2 nuclei. DCN also receives info from VCN. Fusiform cells integrate information to determine spectral cues to locations (for example, whether a sound originated from in front or behind). Cochlear nerve fibers (30,000+) each have a most sensitive frequency and respond over a wide range of levels. Simplified, nerve fibers' signals are transported by bushy cells to

5568-434: The binaural areas in the olivary complex , while signal peaks and valleys are noted by stellate cells, and signal timing is extracted by octopus cells. The lateral lemniscus has three nuclei: dorsal nuclei respond best to bilateral input and have complexity tuned responses; intermediate nuclei have broad tuning responses; and ventral nuclei have broad and moderately complex tuning curves. Ventral nuclei of lateral lemniscus help

5664-452: The body are called exteroceptors . Human external sensation is based on the sensory organs of the eyes , ears , skin , vestibular system , nose , and mouth , which contribute, respectively, to the sensory perceptions of vision , hearing , touch , balance , smell , and taste . Smell and taste are both responsible for identifying molecules and thus both are types of chemoreceptors . Both olfaction (smell) and gustation (taste) require

5760-475: The bony labyrinth, which is filled with fluid called perilymph , similar in composition to cerebrospinal fluid. The chemical difference between the fluids endolymph and perilymph fluids is important for the function of the inner ear due to electrical potential differences between potassium and calcium ions. The plan view of the human cochlea (typical of all mammalian and most vertebrates ) shows where specific frequencies occur along its length. The frequency

5856-546: The brain (cortices) are similarly dedicated to different sensory and perceptual tasks. More complex processing is accomplished across primary cortical regions that spread beyond the primary cortices. Every nerve, sensory or motor , has its own signal transmission speed. For example, nerves in the frog's legs have a 90 ft/s (99 km/h) signal transmission speed, while sensory nerves in humans, transmit sensory information at speeds between 165 ft/s (181 km/h) and 330 ft/s (362 km/h). Perceptual experience

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5952-515: The brain, and/or from stroke ( infarcts in the brain). Temporary or permanent blindness can be caused by poisons or medications. People who are blind from degradation or damage to the visual cortex, but still have functional eyes, are actually capable of some level of vision and reaction to visual stimuli but not a conscious perception; this is known as blindsight . People with blindsight are usually not aware that they are reacting to visual sources, and instead just unconsciously adapt their behavior to

6048-432: The cells or structures that detect sensations. Stimuli in the environment activate specialized receptor cells in the peripheral nervous system . During transduction, physical stimulus is converted into action potential by receptors and transmitted towards the central nervous system for processing. Different types of stimuli are sensed by different types of receptor cells . Receptor cells can be classified into types on

6144-653: The cells to be chemically elongated and shrunk ( somatic motor ), and hair bundles to shift which, in turn, electrically affects the basilar membrane 's movement (hair-bundle motor). These motors (outer hair cells ) amplify the traveling wave amplitudes over 40-fold. The outer hair cells (OHC) are minimally innervated by spiral ganglion in slow (unmyelinated) reciprocal communicative bundles (30+ hairs per nerve fiber ); this contrasts with inner hair cells (IHC) that have only afferent innervation (30+ nerve fibers per one hair) but are heavily connected. There are three to four times as many OHCs as IHCs. The basilar membrane (BM)

6240-461: The cochlear nucleus (CN) fibers decussate (cross left to right and vice versa); this cross aids in sound localization. The CN breaks into ventral (VCN) and dorsal (DCN) regions. The VCN has three nuclei. Bushy cells transmit timing info, their shape averages timing jitters. Stellate (chopper) cells encode sound spectra (peaks and valleys) by spatial neural firing rates based on auditory input strength (rather than frequency). Octopus cells have close to

6336-524: The criterion, thus the signal is differentiated from the noise, the signal is sensed and perceived. Errors in signal detection can potentially lead to false positives and false negatives . The sensory criterion might be shifted based on the importance of the detecting the signal. Shifting of the criterion may influence the likelihood of false positives and false negatives. Subjective visual and auditory experiences appear to be similar across humans subjects. The same cannot be said about taste. For example, there

6432-453: The dark, it is most likely because your brain knows what color something is and is relying on that memory. There is some disagreement as to whether the visual system consists of one, two, or three submodalities. Neuroanatomists generally regard it as two submodalities, given that different receptors are responsible for the perception of color and brightness. Some argue that stereopsis , the perception of depth using both eyes, also constitutes

6528-401: The dermis of the skin are examples of neurons that have free nerve endings (1). Also located in the dermis of the skin are lamellated corpuscles , neurons with encapsulated nerve endings that respond to pressure and touch (2). The cells in the retina that respond to light stimuli are an example of a specialized receptor (3), a photoreceptor . A transmembrane protein receptor is a protein in

6624-425: The detection of a stimulus 50% of the time. Absolute threshold is measured by using a method called signal detection . This process involves presenting stimuli of varying intensities to a subject in order to determine the level at which the subject can reliably detect stimulation in a given sense. Differential threshold or just noticeable difference (JDS) is the smallest detectable difference between two stimuli, or

6720-466: The direction and location of vibrations picked up through the feet. Studies pertaining to audition started to increase in number towards the latter end of the nineteenth century. During this time, many laboratories in the United States began to create new models, diagrams, and instruments that all pertained to the ear. Auditory cognitive psychology is a branch of cognitive psychology that

6816-414: The ear canal are called the auricle . Sound waves are reflected and attenuated when they hit the auricle, and these changes provide additional information that will help the brain determine the sound direction. The sound waves enter the auditory canal , a deceptively simple tube. The ear canal amplifies sounds that are between 3 and 12 kHz . The tympanic membrane , at the far end of the ear canal marks

6912-462: The environment can be either (1) a neuron that has a free nerve ending , with dendrites embedded in tissue that would receive a sensation; (2) a neuron that has an encapsulated ending in which the sensory nerve endings are encapsulated in connective tissue that enhances their sensitivity; or (3) a specialized receptor cell , which has distinct structural components that interpret a specific type of stimulus. The pain and temperature receptors in

7008-445: The environment that affect receptor cell membrane potentials. Other stimuli include the electromagnetic radiation from visible light. For humans, the only electromagnetic energy that is perceived by our eyes is visible light. Some other organisms have receptors that humans lack, such as the heat sensors of snakes, the ultraviolet light sensors of bees, or magnetic receptors in migratory birds. Receptor cells can be further categorized on

7104-629: The inferior colliculus (IC) decode amplitude modulated sounds by giving both phasic and tonic responses (short and long notes, respectively). IC receives inputs not shown, including: The above are what implicate IC in the 'startle response' and ocular reflexes. Beyond multi-sensory integration IC responds to specific amplitude modulation frequencies, allowing for the detection of pitch. IC also determines time differences in binaural hearing. The medial geniculate nucleus divides into: The auditory cortex (AC) brings sound into awareness/perception. AC identifies sounds (sound-name recognition) and also identifies

7200-450: The inner ear from damage by reducing the transmission of sound energy when the stapedius muscle is activated in response to sound. The middle ear still contains the sound information in wave form; it is converted to nerve impulses in the cochlea . The inner ear consists of the cochlea and several non-auditory structures. The cochlea has three fluid-filled sections (i.e. the scala media, scala tympani and scala vestibuli) , and supports

7296-481: The instrument, the listener, and the player of the instrument. Somatosensation is considered a general sense, as opposed to the special senses discussed in this section. Somatosensation is the group of sensory modalities that are associated with touch and interoception. The modalities of somatosensation include pressure , vibration , light touch, tickle , itch , temperature , pain , kinesthesia . Somatosensation , also called tactition (adjectival form: tactile)

7392-512: The lateral aspect of the head is known as the auricle . At the end of the auditory canal is the tympanic membrane, or ear drum , which vibrates after it is struck by sound waves. The auricle, ear canal, and tympanic membrane are often referred to as the external ear . The middle ear consists of a space spanned by three small bones called the ossicles . The three ossicles are the malleus , incus , and stapes , which are Latin names that roughly translate to hammer, anvil, and stirrup. The malleus

7488-438: The membrane, and can generate an action potential or a graded potential in the sensory neurons . A third classification of receptors is by how the receptor transduces stimuli into membrane potential changes. Stimuli are of three general types. Some stimuli are ions and macromolecules that affect transmembrane receptor proteins when these chemicals diffuse across the cell membrane. Some stimuli are physical variations in

7584-408: The molecular level, visual stimuli cause changes in the photopigment molecule that lead to changes in membrane potential of the photoreceptor cell. A single unit of light is called a photon , which is described in physics as a packet of energy with properties of both a particle and a wave. The energy of a photon is represented by its wavelength , with each wavelength of visible light corresponding to

7680-437: The movement of hair at the surface of the skin, such as when an insect may be walking along the skin . Stretching of the skin is transduced by stretch receptors known as bulbous corpuscles . Bulbous corpuscles are also known as Ruffini corpuscles, or type II cutaneous mechanoreceptors. The heat receptors are sensitive to infrared radiation and can occur in specialized organs, for instance in pit vipers . The thermoceptors in

7776-403: The muscles of the pharynx contract during swallowing or yawning . Mechanoreceptors turn motion into electrical nerve pulses, which are located in the inner ear. Since sound is vibration, propagating through a medium such as air, the detection of these vibrations, that is the sense of the hearing, is a mechanical sense because these vibrations are mechanically conducted from the eardrum through

7872-452: The neurotransmitter glutamate communicates signals from the hair cells to the dendrites of the primary auditory neurons. There are far fewer inner hair cells in the cochlea than afferent nerve fibers – many auditory nerve fibers innervate each hair cell. The neural dendrites belong to neurons of the auditory nerve , which in turn joins the vestibular nerve to form the vestibulocochlear nerve , or cranial nerve number VIII. The region of

7968-473: The posterior superior temporal gyrus and sulcus, inferior parietal lobule and intra-parietal sulcus. Both pathways project in humans to the inferior frontal gyrus. The most established role of the auditory dorsal stream in primates is sound localization. In humans, the auditory dorsal stream in the left hemisphere is also responsible for speech repetition and articulation, phonological long-term encoding of word names, and verbal working memory. Proper function of

8064-440: The primary auditory cortex can probably be divided further into functionally differentiable subregions. The neurons of the primary auditory cortex can be considered to have receptive fields covering a range of auditory frequencies and have selective responses to harmonic pitches. Neurons integrating information from the two ears have receptive fields covering a particular region of auditory space. The primary auditory cortex

8160-405: The primary auditory cortex emerge two separate pathways: the auditory ventral stream and auditory dorsal stream. The auditory ventral stream includes the anterior superior temporal gyrus, anterior superior temporal sulcus, middle temporal gyrus and temporal pole. Neurons in these areas are responsible for sound recognition, and extraction of meaning from sentences. The auditory dorsal stream includes

8256-714: The sensory organs of the eyes , ears , skin , nose , mouth and the vestibular system . Internal sensation detects stimuli from internal organs and tissues. Internal senses possessed by humans include spatial orientation , proprioception (body position) and nociception (pain). Further internal senses lead to signals such as hunger , thirst , suffocation , and nausea , or different involuntary behaviors, such as vomiting . Some animals are able to detect electrical and magnetic fields , air moisture , or polarized light , while others sense and perceive through alternative systems, such as echolocation . Sensory modalities or sub modalities are different ways sensory information

8352-432: The skin are quite different from the homeostatic thermoceptors in the brain ( hypothalamus ), which provide feedback on internal body temperature. Auditory system The outer ear funnels sound vibrations to the eardrum , increasing the sound pressure in the middle frequency range. The middle-ear ossicles further amplify the vibration pressure roughly 20 times. The base of the stapes couples vibrations into

8448-482: The smallest difference in stimuli that can be judged to be different from each other. Weber's Law is an empirical law that states that the difference threshold is a constant fraction of the comparison stimulus. According to Weber's Law, bigger stimuli require larger differences to be noticed. Magnitude estimation is a psychophysical method in which subjects assign perceived values of given stimuli. The relationship between stimulus intensity and perceptive intensity

8544-498: The sound's origin location. AC is a topographical frequency map with bundles reacting to different harmonies, timing and pitch. Right-hand-side AC is more sensitive to tonality, left-hand-side AC is more sensitive to minute sequential differences in sound. Rostromedial and ventrolateral prefrontal cortices are involved in activation during tonal space and storing short-term memories, respectively. The Heschl's gyrus/transverse temporal gyrus includes Wernicke's area and functionality, it

8640-465: The stimulus. On February 14, 2013, researchers developed a neural implant that gives rats the ability to sense infrared light which for the first time provides living creatures with new abilities, instead of simply replacing or augmenting existing abilities. According to Gestalt Psychology, people perceive the whole of something even if it is not there. The Gestalt's Law of Organization states that people have seven factors that help to group what

8736-452: The tendency humans have to categorize objects according to past experiences under certain circumstances. If two objects are usually perceived together or within close proximity of each other the Law of Past Experience is usually seen. Hearing, or audition, is the transduction of sound waves into a neural signal that is made possible by the structures of the ear . The large, fleshy structure on

8832-563: The tips of one cilium to another. Stretching and compressing, the tip links may open an ion channel and produce the receptor potential in the hair cell. Recently it has been shown that cadherin-23 CDH23 and protocadherin-15 PCDH15 are the adhesion molecules associated with these tip links. It is thought that a calcium driven motor causes a shortening of these links to regenerate tensions. This regeneration of tension allows for apprehension of prolonged auditory stimulation. Afferent neurons innervate cochlear inner hair cells, at synapses where

8928-587: The transduction of chemical stimuli into electrical potentials. The visual system, or sense of sight, is based on the transduction of light stimuli received through the eyes and contributes to visual perception . The visual system detects light on photoreceptors in the retina of each eye that generates electrical nerve impulses for the perception of varying colors and brightness. There are two types of photoreceptors: rods and cones . Rods are very sensitive to light but do not distinguish colors. Cones distinguish colors but are less sensitive to dim light. At

9024-406: The ventral cochlear nucleus, although the dorsal cochlear nucleus projects there as well, via the ventral acoustic stria. Within the superior olivary complex lies the lateral superior olive (LSO) and the medial superior olive (MSO). The former is important in detecting interaural level differences while the latter is important in distinguishing interaural time difference . The lateral lemniscus

9120-416: The wavelength scale. The three types of cone opsins , being sensitive to different wavelengths of light, provide us with color vision. By comparing the activity of the three different cones, the brain can extract color information from visual stimuli. For example, a bright blue light that has a wavelength of approximately 450 nm would activate the "red" cones minimally, the "green" cones marginally, and

9216-413: The way that information is encoded, which is similar to the idea of transduction . The main sensory modalities can be described on the basis of how each is transduced. Listing all the different sensory modalities, which can number as many as 17, involves separating the major senses into more specific categories, or submodalities, of the larger sense. An individual sensory modality represents the sensation of

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