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137-470: The hippocampus ( pl. : hippocampi ; via Latin from Greek ἱππόκαμπος , ' seahorse ') is a major component of the brain of humans and other vertebrates . Humans and other mammals have two hippocampi, one in each side of the brain . The hippocampus is part of the limbic system , and plays important roles in the consolidation of information from short-term memory to long-term memory , and in spatial memory that enables navigation. The hippocampus

274-457: A multiple-systems model , suggesting that some effects may not be simply mediated by one portion of the brain. Studies on freely moving rats and mice have shown many hippocampal neurons to act as place cells that cluster in place fields , and these fire bursts of action potentials when the animal passes through a particular location. This place-related neural activity in the hippocampus has also been reported in monkeys that were moved around

411-543: A pitch accent . In Modern Greek, all vowels and consonants are short. Many vowels and diphthongs once pronounced distinctly are pronounced as /i/ ( iotacism ). Some of the stops and glides in diphthongs have become fricatives , and the pitch accent has changed to a stress accent . Many of the changes took place in the Koine Greek period. The writing system of Modern Greek, however, does not reflect all pronunciation changes. The examples below represent Attic Greek in

548-447: A seahorse , and the terms seahorse and sea-horse refer to the mythological creature. The above-mentioned fish hybrids are seen less frequently. In appearance, the heraldic sea-horse is depicted as having the head and neck of a horse, the tail of a fish and webbed paws replacing its front hooves. Its mane may be that of a horse or it may be replaced with an additional fin. Sea-horses may be depicted with wings, and winged sea-horses with

685-416: A broader system that incorporates both the memory and the spatial perspectives in its role that involves the use of a wide scope of cognitive maps. This relates to the purposive behaviorism born of Tolman's original goal of identifying the complex cognitive mechanisms and purposes that guided behaviour. It has also been proposed that the spiking activity of hippocampal neurons is associated spatially, and it

822-416: A comparison with the shape of the folded back forelimbs and webbed feet of the mythological hippocampus , a sea monster with a horse's forequarters and a fish's tail. The hippocampus was then described as pes hippocampi major , with an adjacent bulge in the occipital horn , described as the pes hippocampi minor and later renamed as the calcar avis . The renaming of the hippocampus as hippocampus major, and

959-530: A distinct pattern of neural population activity and waves of electrical activity as measured by an electroencephalogram (EEG). These modes are named after the EEG patterns associated with them: theta and large irregular activity (LIA). The main characteristics described below are for the rat, which is the animal most extensively studied. The theta mode appears during states of active, alert behavior (especially locomotion), and also during REM (dreaming) sleep. In

1096-452: A fantastic marine creature with the body and tail of a fish and the forepart of a goat. This sea-goat moves to the right and turns his head back to look at the goddess. This group also appears on Aphrodisian coins from the 3rd century A.D. Aside from aigikampoi , the fish-tailed goats representing Capricorn, other fish-tailed animals rarely appeared in Greek art, but are more characteristic of

1233-414: A full-fledged theory of the role of the hippocampus in anxiety. The inhibition theory is currently the least popular of the three. The second major line of thought relates the hippocampus to memory. Although it had historical precursors, this idea derived its main impetus from a famous report by American neurosurgeon William Beecher Scoville and British-Canadian neuropsychologist Brenda Milner describing

1370-443: A hidden goal. Other cells have been discovered since the finding of the place cells in the rodent brain that are either in the hippocampus or the entorhinal cortex. These have been assigned as head direction cells , grid cells and boundary cells . Speed cells are thought to provide input to the hippocampal grid cells. Approach-avoidance conflict happens when a situation is presented that can either be rewarding or punishing, and

1507-619: A horn were part of the armorial bearings granted to Sir Sean Connery in 2018 by the Lord Lyon King of Arms , the head of Scotland's heraldic authority. The sea-horse is also a common image in Renaissance and Baroque art, for example, in the Trevi fountain , dating to 1732. A winged hippocampus has been used as a symbol for Air France since its establishment in 1933 (inherited from its predecessor Air Orient ); it appears today on

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1644-477: A lack of contemporaneous evidence. Several theories exist about what Hellenic dialect groups may have existed between the divergence of early Greek-like speech from the common Proto-Indo-European language and the Classical period. They have the same general outline but differ in some of the detail. The only attested dialect from this period is Mycenaean Greek , but its relationship to the historical dialects and

1781-419: A lesser degree. Pamphylian Greek , spoken in a small area on the southwestern coast of Anatolia and little preserved in inscriptions, may be either a fifth major dialect group, or it is Mycenaean Greek overlaid by Doric, with a non-Greek native influence. Regarding the speech of the ancient Macedonians diverse theories have been put forward, but the epigraphic activity and the archaeological discoveries in

1918-404: A life-long memory of the event even after a single training session. The memory of such an event appears to be first stored in the hippocampus, but this storage is transient. Much of the long-term storage of the memory seems to take place in the anterior cingulate cortex . When such an intense learning event was experimentally applied, more than 5,000 differently methylated DNA regions appeared in

2055-472: A line of work that eventually led to their very influential 1978 book The Hippocampus as a Cognitive Map . There is now almost universal agreement that hippocampal function plays an important role in spatial coding, but the details are widely debated. Later research has focused on trying to bridge the disconnect between the two main views of hippocampal function as being split between memory and spatial cognition. In some studies, these areas have been expanded to

2192-414: A number of studies that show the involvement of the hippocampus in conflict tasks. The authors suggest that one challenge is to understand how conflict processing relates to the functions of spatial navigation and memory and how all of these functions need not be mutually exclusive. The hippocampus has received renewed attention for its role in social memory. Epileptic human subjects with depth electrodes in

2329-409: A phenomenon in the rabbit hippocampus that appeared to meet Hebb's specifications: a change in synaptic responsiveness induced by brief strong activation and lasting for hours or days or longer. This phenomenon was soon referred to as long-term potentiation (LTP). As a candidate mechanism for long-term memory , LTP has since been studied intensively, and a great deal has been learned about it. However,

2466-498: A prefix /e-/, called the augment . This was probably originally a separate word, meaning something like "then", added because tenses in PIE had primarily aspectual meaning. The augment is added to the indicative of the aorist, imperfect, and pluperfect, but not to any of the other forms of the aorist (no other forms of the imperfect and pluperfect exist). The two kinds of augment in Greek are syllabic and quantitative. The syllabic augment

2603-507: A proportion of the claimed CA1 cells in the study. The dorsal CA2 and ventral CA1 subregions of the hippocampus have been implicated in social memory processing. Genetic inactivation of CA2 pyramidal neurons leads to pronounced loss of social memory, while maintaining intact sociability in mice. Similarly, ventral CA1 pyramidal neurons have also been demonstrated as critical for social memory under optogenetic control in mice. The hippocampus shows two major "modes" of activity, each associated with

2740-410: A rat's location to be reconstructed with high confidence. The size of place fields varies in a gradient along the length of the hippocampus, with cells at the dorsal end showing the smallest fields, cells near the center showing larger fields, and cells at the ventral tip showing fields that cover the entire environment. In some cases, the firing rate of hippocampal cells depends not only on place but also

2877-540: A result of depression, but this can be stopped with anti-depressants even if they are not effective in relieving other symptoms. Chronic stress resulting in elevated levels of glucocorticoids , notably of cortisol , is seen to be a cause of neuronal atrophy in the hippocampus. This atrophy results in a smaller hippocampal volume which is also seen in Cushing's syndrome . The higher levels of cortisol in Cushing's syndrome

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3014-576: A room whilst in a restraint chair. However, the place cells may have fired in relation to where the monkey was looking rather than to its actual location in the room. Over many years, many studies have been carried out on place-responses in rodents, which have given a large amount of information. Place cell responses are shown by pyramidal cells in the hippocampus and by granule cells in the dentate gyrus . Other cells in smaller proportion are inhibitory interneurons , and these often show place-related variations in their firing rate that are much weaker. There

3151-608: A separate historical stage, though its earliest form closely resembles Attic Greek , and its latest form approaches Medieval Greek . There were several regional dialects of Ancient Greek; Attic Greek developed into Koine. Ancient Greek was a pluricentric language , divided into many dialects. The main dialect groups are Attic and Ionic , Aeolic , Arcadocypriot , and Doric , many of them with several subdivisions. Some dialects are found in standardized literary forms in literature , while others are attested only in inscriptions. There are also several historical forms. Homeric Greek

3288-475: A severe impact on many types of cognition including memory . Even normal aging is associated with a gradual decline in some types of memory, including episodic memory and working memory (or short-term memory ). Because the hippocampus is thought to play a central role in memory, there has been considerable interest in the possibility that age-related declines could be caused by hippocampal deterioration. Some early studies reported substantial loss of neurons in

3425-443: A sharp wave, there is a dramatic increase in firing rate in up to 10% of the hippocampal population These two hippocampal activity modes can be seen in primates as well as rats, with the exception that it has been difficult to see robust theta rhythmicity in the primate hippocampus. There are, however, qualitatively similar sharp waves and similar state-dependent changes in neural population activity. The underlying currents producing

3562-630: A standard subject of study in educational institutions of the Western world since the Renaissance . This article primarily contains information about the Epic and Classical periods of the language, which are the best-attested periods and considered most typical of Ancient Greek. From the Hellenistic period ( c.  300 BC ), Ancient Greek was followed by Koine Greek , which is regarded as

3699-674: A theme in Etruscan tomb wall-paintings and reliefs, where they are sometimes provided with wings, as they are in the Trevi fountain. Katharine Shepard found in the theme an Etruscan belief in a sea-voyage to the other world. The sea-horse also appears in Pictish stone carvings in Scotland. The symbolism of the carving (also known as " Pictish Beast " or " Kelpie ") is unknown. Although similar but not identical to Roman sea-horse images, it

3836-608: A very irregular temporal pattern. Sharp waves are less frequent during inactive waking states and are usually smaller. Sharp waves have also been observed in humans and monkeys. In macaques, sharp waves are robust but do not occur as frequently as in rats. One of the most interesting aspects of sharp waves is that they appear to be associated with memory. Wilson and McNaughton 1994, and numerous later studies, reported that when hippocampal place cells have overlapping spatial firing fields (and therefore often fire in near-simultaneity), they tend to show correlated activity during sleep following

3973-510: A vowel or /n s r/ ; final stops were lost, as in γάλα "milk", compared with γάλακτος "of milk" (genitive). Ancient Greek of the classical period also differed in both the inventory and distribution of original PIE phonemes due to numerous sound changes, notably the following: The pronunciation of Ancient Greek was very different from that of Modern Greek . Ancient Greek had long and short vowels ; many diphthongs ; double and single consonants; voiced, voiceless, and aspirated stops ; and

4110-503: Is a deep emotional connection between episodic memories and places. Due to bilateral symmetry the brain has a hippocampus in each cerebral hemisphere . If damage to the hippocampus occurs in only one hemisphere, leaving the structure intact in the other hemisphere, the brain can retain near-normal memory functioning. Severe damage to the hippocampi in both hemispheres results in profound difficulties in forming new memories ( anterograde amnesia ) and often also affects memories formed before

4247-570: Is a literary form of Archaic Greek (derived primarily from Ionic and Aeolic) used in the epic poems , the Iliad and the Odyssey , and in later poems by other authors. Homeric Greek had significant differences in grammar and pronunciation from Classical Attic and other Classical-era dialects. The origins, early form and development of the Hellenic language family are not well understood because of

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4384-418: Is added to stems beginning with consonants, and simply prefixes e (stems beginning with r , however, add er ). The quantitative augment is added to stems beginning with vowels, and involves lengthening the vowel: Some verbs augment irregularly; the most common variation is e → ei . The irregularity can be explained diachronically by the loss of s between vowels, or that of the letter w , which affected

4521-460: Is also substantial evidence that it makes a contribution to memory, which can be distinguished from the contribution of the hippocampus. It is apparent that complete amnesia occurs only when both the hippocampus and the parahippocampus are damaged. The major input to the hippocampus is through the entorhinal cortex (EC), whereas its major output is via CA1 to the subiculum. Information reaches CA1 via two main pathways, direct and indirect. Axons from

4658-666: Is called 'East Greek'. Arcadocypriot apparently descended more closely from the Mycenaean Greek of the Bronze Age. Boeotian Greek had come under a strong Northwest Greek influence, and can in some respects be considered a transitional dialect, as exemplified in the poems of the Boeotian poet Pindar who wrote in Doric with a small Aeolic admixture. Thessalian likewise had come under Northwest Greek influence, though to

4795-410: Is concealed by the parahippocampal gyrus . The cortex thins from six layers to the three or four layers that make up the hippocampus. The term hippocampal formation is used to refer to the hippocampus proper and its related parts. However, there is no consensus as to what parts are included. Sometimes the hippocampus is said to include the dentate gyrus and the subiculum . Some references include

4932-448: Is considered by some linguists to have been closely related to Greek . Among Indo-European branches with living descendants, Greek is often argued to have the closest genetic ties with Armenian (see also Graeco-Armenian ) and Indo-Iranian languages (see Graeco-Aryan ). Ancient Greek differs from Proto-Indo-European (PIE) and other Indo-European languages in certain ways. In phonotactics , ancient Greek words could end only in

5069-415: Is described as having an anterior and posterior part (in primates ) or a ventral and dorsal part in other animals. Both parts are of similar composition but belong to different neural circuits . In the rat, the two hippocampi resemble a pair of bananas, joined at the stems by the commissure of fornix (also called the hippocampal commissure). In primates , the part of the hippocampus at the bottom, near

5206-437: Is little, if any, spatial topography in the representation; in general, cells lying next to each other in the hippocampus have uncorrelated spatial firing patterns. Place cells are typically almost silent when a rat is moving around outside the place field but reach sustained rates as high as 40 Hz when the rat is near the center. Neural activity sampled from 30 to 40 randomly chosen place cells carries enough information to allow

5343-408: Is located in the allocortex , with neural projections into the neocortex , in humans as well as other primates. The hippocampus, as the medial pallium , is a structure found in all vertebrates . In humans, it contains two main interlocking parts: the hippocampus proper (also called Ammon's horn ), and the dentate gyrus . In Alzheimer's disease (and other forms of dementia ), the hippocampus

5480-572: Is more involved in executive functions and regulation during verbal memory recall. The tail of the left hippocampus tends to be closely related to verbal memory capacity. Damage to the hippocampus does not affect some types of memory, such as the ability to learn new skills (playing a musical instrument or solving certain types of puzzles, for example). This fact suggests that such abilities depend on different types of memory ( procedural memory ) and different brain regions. Furthermore, amnesic patients frequently show "implicit" memory for experiences even in

5617-455: Is not yet clear. In rats (the animals that have been the most extensively studied), theta is seen mainly in two conditions: first, when an animal is walking or in some other way actively interacting with its surroundings; second, during REM sleep . The function of theta has not yet been convincingly explained although numerous theories have been proposed. The most popular hypothesis has been to relate it to learning and memory. An example would be

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5754-515: Is occasionally interrupted by large surges called sharp waves . These events are associated with bursts of spike activity lasting 50 to 100 milliseconds in pyramidal cells of CA3 and CA1. They are also associated with short-lived high-frequency EEG oscillations called "ripples", with frequencies in the range 150 to 200 Hz in rats, and together they are known as sharp waves and ripples . Sharp waves are most frequent during sleep when they occur at an average rate of around 1 per second (in rats) but in

5891-488: Is one of the first regions of the brain to suffer damage; short-term memory loss and disorientation are included among the early symptoms. Damage to the hippocampus can also result from oxygen starvation ( hypoxia ), encephalitis , or medial temporal lobe epilepsy . People with extensive, bilateral hippocampal damage may experience anterograde amnesia : the inability to form and retain new memories . Since different neuronal cell types are neatly organized into layers in

6028-471: Is suggested that the memory, spatial cognition, and conflict processing functions may be seen as working together and not mutually exclusive. Psychologists and neuroscientists generally agree that the hippocampus plays an important role in the formation of new memories about experienced events ( episodic or autobiographical memory ). Part of this function is hippocampal involvement in the detection of new events, places and stimuli. Some researchers regard

6165-472: Is unclear whether this depiction originates from images brought over by the Romans, or had a place in earlier Pictish mythology. The mythic hippocampus has been used as a heraldic charge , particularly since the Renaissance, most often in the armorial bearings of people and places with maritime associations. However, in a blazon , the terms hippocamp and hippocampus now refer to the real animal called

6302-444: Is usually the result of medications taken for other conditions. Neuronal loss also occurs as a result of impaired neurogenesis. Another factor that contributes to a smaller hippocampal volume is that of dendritic retraction where dendrites are shortened in length and reduced in number, in response to increased glucocorticoids. This dendritic retraction is reversible. After treatment with medication to reduce cortisol in Cushing's syndrome,

6439-555: The Great Hippocampus Question . The term hippocampus minor fell from use in anatomy textbooks and was officially removed in the Nomina Anatomica of 1895. Today, the structure is just called the hippocampus, with the term cornu Ammonis (that is, 'Ammon's horn') surviving in the names of the hippocampal subfields CA1-CA4 . The term limbic system was introduced in 1952 by Paul MacLean to describe

6576-759: The Greek region of Macedonia during the last decades has brought to light documents, among which the first texts written in Macedonian , such as the Pella curse tablet , as Hatzopoulos and other scholars note. Based on the conclusions drawn by several studies and findings such as Pella curse tablet , Emilio Crespo and other scholars suggest that ancient Macedonian was a Northwest Doric dialect , which shares isoglosses with its neighboring Thessalian dialects spoken in northeastern Thessaly . Some have also suggested an Aeolic Greek classification. The Lesbian dialect

6713-423: The entorhinal cortex via the perforant path . The entorhinal cortex (EC) is strongly and reciprocally connected with many cortical and subcortical structures as well as with the brainstem. Different thalamic nuclei , (from the anterior and midline groups), the medial septal nucleus , the supramammillary nucleus of the hypothalamus, and the raphe nuclei and locus coeruleus of the brainstem all send axons to

6850-471: The hypothalamic mammillary body , and the anterior nuclear complex in the thalamus , and is generally accepted to be part of the limbic system. The hippocampus can be seen as a ridge of gray matter tissue , elevating from the floor of each lateral ventricle in the region of the inferior or temporal horn. This ridge can also be seen as an inward fold of the archicortex into the medial temporal lobe . The hippocampus can only be seen in dissections as it

6987-501: The present , future , and imperfect are imperfective in aspect; the aorist , present perfect , pluperfect and future perfect are perfective in aspect. Most tenses display all four moods and three voices, although there is no future subjunctive or imperative. Also, there is no imperfect subjunctive, optative or imperative. The infinitives and participles correspond to the finite combinations of tense, aspect, and voice. The indicative of past tenses adds (conceptually, at least)

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7124-473: The thalamus to field CA1. A very important projection comes from the medial septal nucleus, which sends cholinergic , and gamma amino butyric acid (GABA) stimulating fibers (GABAergic fibers) to all parts of the hippocampus. The inputs from the medial septal nucleus play a key role in controlling the physiological state of the hippocampus; destruction of this nucleus abolishes the hippocampal theta rhythm and severely impairs certain types of memory. Areas of

7261-1031: The 5th century BC. Ancient pronunciation cannot be reconstructed with certainty, but Greek from the period is well documented, and there is little disagreement among linguists as to the general nature of the sounds that the letters represent. /oː/ raised to [uː] , probably by the 4th century BC. Greek, like all of the older Indo-European languages , is highly inflected. It is highly archaic in its preservation of Proto-Indo-European forms. In ancient Greek, nouns (including proper nouns) have five cases ( nominative , genitive , dative , accusative , and vocative ), three genders ( masculine , feminine , and neuter ), and three numbers (singular, dual , and plural ). Verbs have four moods ( indicative , imperative , subjunctive , and optative ) and three voices (active, middle, and passive ), as well as three persons (first, second, and third) and various other forms. Verbs are conjugated through seven combinations of tenses and aspect (generally simply called "tenses"):

7398-495: The Archaic period of ancient Greek (see Homeric Greek for more details): Μῆνιν ἄειδε, θεά, Πηληϊάδεω Ἀχιλῆος οὐλομένην, ἣ μυρί' Ἀχαιοῖς ἄλγε' ἔθηκε, πολλὰς δ' ἰφθίμους ψυχὰς Ἄϊδι προΐαψεν ἡρώων, αὐτοὺς δὲ ἑλώρια τεῦχε κύνεσσιν οἰωνοῖσί τε πᾶσι· Διὸς δ' ἐτελείετο βουλή· ἐξ οὗ δὴ τὰ πρῶτα διαστήτην ἐρίσαντε Ἀτρεΐδης τε ἄναξ ἀνδρῶν καὶ δῖος Ἀχιλλεύς. The beginning of Apology by Plato exemplifies Attic Greek from

7535-597: The Classical period of ancient Greek. (The second line is the IPA , the third is transliterated into the Latin alphabet using a modern version of the Erasmian scheme .) Ὅτι [hóti Hóti μὲν men mèn ὑμεῖς, hyːmêːs hūmeîs,   Hippocampus (mythology) Coins minted at Tyre around the 4th century BC show the patron god Melqart riding on a winged hippocampus and accompanied by dolphins. Coins of

7672-507: The DH were shown to cause spatial memory impairment while VH lesions did not. Its projecting pathways include the medial septal nucleus and supramammillary nucleus . The dorsal hippocampus also has more place cells than both the ventral and intermediate hippocampal regions. The intermediate hippocampus has overlapping characteristics with both the ventral and dorsal hippocampus. Using anterograde tracing methods, Cenquizca and Swanson (2007) located

7809-512: The DNA base excision repair pathway (see Epigenetics in learning and memory ). The between-systems memory interference model describes the inhibition of non-hippocampal systems of memory during concurrent hippocampal activity. Specifically, Fraser Sparks, Hugo Lehmann, and Robert Sutherland found that when the hippocampus was inactive, non-hippocampal systems located elsewhere in the brain were found to consolidate memory in its place. However, when

7946-451: The EC that originate in layer III are the origin of the direct perforant pathway and form synapses on the very distal apical dendrites of CA1 neurons. Conversely, axons originating from layer II are the origin of the indirect pathway, and information reaches CA1 via the trisynaptic circuit . In the initial part of this pathway, the axons project through the perforant pathway to the granule cells of

8083-400: The EC, so that it serves as the interface between the neocortex and the other connections, and the hippocampus. The EC is located in the parahippocampal gyrus , a cortical region adjacent to the hippocampus. This gyrus conceals the hippocampus. The parahippocampal gyrus is adjacent to the perirhinal cortex , which plays an important role in the visual recognition of complex objects. There

8220-484: The Etruscans. These include leokampoi (fish-tailed lions ), taurokampoi (fish-tailed bulls ) or pardalokampoi (fish-tailed leopards ). The combination of a horse and a fish was also evoked in the concept of an Ichthyocentaur , which replaced the head and neck of the horse portion with the upper body of a man, akin instead to the more widespread hippocentaur . Icthyocentaurs appeared in ancient visual art from

8357-501: The LIA mode, the EEG is dominated by sharp waves that are randomly timed large deflections of the EEG signal lasting for 25–50 milliseconds. Sharp waves are frequently generated in sets, with sets containing up to 5 or more individual sharp waves and lasting up to 500 ms. The spiking activity of neurons within the hippocampus is highly correlated with sharp wave activity. Most neurons decrease their firing rate between sharp waves; however, during

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8494-480: The absence of conscious knowledge. For example, patients asked to guess which of two faces they have seen most recently may give the correct answer most of the time in spite of stating that they have never seen either of the faces before. Some researchers distinguish between conscious recollection , which depends on the hippocampus, and familiarity , which depends on portions of the medial temporal lobe. When rats are exposed to an intense learning event, they may retain

8631-431: The ancient Egyptian god often portrayed as such takes the name c ornu A mmonis . Its abbreviation CA is used in naming the hippocampal subfields CA1, CA2, CA3, and CA4 . It can be distinguished as an area where the cortex narrows into a single layer of densely packed pyramidal neurons , which curl into a tight U shape. One edge of the "U," – CA4, is embedded into the backward-facing, flexed dentate gyrus. The hippocampus

8768-550: The aorist. Following Homer 's practice, the augment is sometimes not made in poetry , especially epic poetry. The augment sometimes substitutes for reduplication; see below. Almost all forms of the perfect, pluperfect, and future perfect reduplicate the initial syllable of the verb stem. (A few irregular forms of perfect do not reduplicate, whereas a handful of irregular aorists reduplicate.) The three types of reduplication are: Irregular duplication can be understood diachronically. For example, lambanō (root lab ) has

8905-419: The augment when it was word-initial. In verbs with a preposition as a prefix, the augment is placed not at the start of the word, but between the preposition and the original verb. For example, προσ(-)βάλλω (I attack) goes to προσ έ βαλoν in the aorist. However compound verbs consisting of a prefix that is not a preposition retain the augment at the start of the word: αὐτο(-)μολῶ goes to ηὐ τομόλησα in

9042-410: The base of the temporal lobe , is much broader than the part at the top. This means that in cross-section the hippocampus can show a number of different shapes, depending on the angle and location of the cut. In a cross-section of the hippocampus, including the dentate gyrus, several layers will be shown. The dentate gyrus has three layers of cells (or four if the hilus is included). The layers are from

9179-490: The behavioral session. This enhancement of correlation, commonly known as reactivation , has been found to occur mainly during sharp waves. It has been proposed that sharp waves are, in fact, reactivations of neural activity patterns that were memorized during behavior, driven by strengthening of synaptic connections within the hippocampus. This idea forms a key component of the "two-stage memory" theory, advocated by Buzsáki and others, which proposes that memories are stored within

9316-416: The brain that are either in the hippocampus itself or are strongly connected to it, such as the speed cells present in the medial entorhinal cortex . Together these cells form a network that serves as spatial memory. The first of such cells discovered in the 1970s were the place cells, which led to the idea of the hippocampus acting to give a neural representation of the environment in a cognitive map . When

9453-469: The brakes!") was very popular up to the 1960s. It derived much of its justification from two observations: first, that animals with hippocampal damage tend to be hyperactive ; second, that animals with hippocampal damage often have difficulty learning to inhibit responses that they have previously been taught, especially if the response requires remaining quiet as in a passive avoidance test. British psychologist Jeffrey Gray developed this line of thought into

9590-441: The calcar avis as hippocampus minor, has been attributed to Félix Vicq-d'Azyr systematizing nomenclature of parts of the brain in 1786. Mayer mistakenly used the term hippopotamus in 1779, and was followed by some other authors until Karl Friedrich Burdach resolved this error in 1829. In 1861 the hippocampus minor became the center of a dispute over human evolution between Thomas Henry Huxley and Richard Owen , satirized as

9727-438: The center of Greek scholarship, this division of people and language is quite similar to the results of modern archaeological-linguistic investigation. One standard formulation for the dialects is: West vs. non-West Greek is the strongest-marked and earliest division, with non-West in subsets of Ionic-Attic (or Attic-Ionic) and Aeolic vs. Arcadocypriot, or Aeolic and Arcado-Cypriot vs. Ionic-Attic. Often non-West

9864-495: The complexity and variety of the intracellular signalling cascades that can trigger LTP is acknowledged as preventing a more complete understanding. The hippocampus is a particularly favorable site for studying LTP because of its densely packed and sharply defined layers of neurons, but similar types of activity-dependent synaptic change have also been observed in many other brain areas. The best-studied form of LTP has been seen in CA1 of

10001-448: The damage occurred ( retrograde amnesia ). Although the retrograde effect normally extends many years back before the brain damage, in some cases older memories remain. This retention of older memories leads to the idea that consolidation over time involves the transfer of memories out of the hippocampus to other parts of the brain. Experiments using intrahippocampal transplantation of hippocampal cells in primates with neurotoxic lesions of

10138-472: The dentate gyrus (first synapse). From then, the information follows via the mossy fibres to CA3 (second synapse). From there, CA3 axons called Schaffer collaterals leave the deep part of the cell body and loop up to the apical dendrites and then extend to CA1 (third synapse). Axons from CA1 then project back to the entorhinal cortex, completing the circuit. Basket cells in CA3 receive excitatory input from

10275-401: The dentate gyrus and the subiculum in the hippocampal formation, and others also include the presubiculum, parasubiculum , and entorhinal cortex . The neural layout and pathways within the hippocampal formation are very similar in all mammals. The hippocampus, including the dentate gyrus, has the shape of a curved tube, which has been compared to a seahorse, and to a horn of a ram, which after

10412-615: The dialect of Sparta ), and Northern Peloponnesus Doric (including Corinthian ). All the groups were represented by colonies beyond Greece proper as well, and these colonies generally developed local characteristics, often under the influence of settlers or neighbors speaking different Greek dialects. After the conquests of Alexander the Great in the late 4th century BC, a new international dialect known as Koine or Common Greek developed, largely based on Attic Greek , but with influence from other dialects. This dialect slowly replaced most of

10549-408: The direction a rat is moving, the destination toward which it is traveling, or other task-related variables. The firing of place cells is timed in relation to local theta waves , a process termed phase precession . In humans, cells with location-specific firing patterns have been reported during a study of patients with drug-resistant epilepsy . They were undergoing an invasive procedure to localize

10686-420: The earliest widely held hypothesis was that the hippocampus is involved in olfaction . This idea was cast into doubt by a series of anatomical studies that did not find any direct projections to the hippocampus from the olfactory bulb . However, later work did confirm that the olfactory bulb does project into the ventral part of the lateral entorhinal cortex, and field CA1 in the ventral hippocampus sends axons to

10823-476: The elderly than in the young. Furthermore, a randomized control trial published in 2011 found that aerobic exercise could increase the size of the hippocampus in adults aged 55 to 80 and also improve spatial memory. The hippocampus contains high levels of glucocorticoid receptors , which make it more vulnerable to long-term stress than most other brain areas . There is evidence that humans having experienced severe, long-lasting traumatic stress show atrophy of

10960-532: The engine nacelles of Air France sea craft Bronze hippocampi appear in Dublin , Leinster , Ireland on lampposts next to a statue of Henry Grattan and on Grattan Bridge . The English football club Newcastle United has two hippocampi depicted on its crest. They appear to the left and right of the shield in the middle. The Civic Centre in Newcastle-upon-Tyne is also adorned with hippocampi at

11097-480: The ensuing decision-making has been associated with anxiety . fMRI findings from studies in approach-avoidance decision-making found evidence for a functional role that is not explained by either long-term memory or spatial cognition. Overall findings showed that the anterior hippocampus is sensitive to conflict, and that it may be part of a larger cortical and subcortical network seen to be important in decision-making in uncertain conditions. A review makes reference to

11234-407: The fastest routes between them in order to pass a strict test known as The Knowledge in order to gain a license to operate. A study showed that the posterior part of the hippocampus is larger in these drivers than in the general public, and that a positive correlation exists between the length of time served as a driver and the increase in the volume of this part. It was also found the total volume of

11371-516: The first to illustrate the structure, also wavered between "seahorse" and "silkworm". "Ram's horn" was proposed by the Danish anatomist Jacob Winsløw in 1732; and a decade later his fellow Parisian, the surgeon de Garengeot, used cornu Ammonis – horn of Amun , the ancient Egyptian god who was often represented as having a ram's head. Another reference appeared with the term pes hippocampi , which may date back to Diemerbroeck in 1672, introducing

11508-673: The forms of the Greek language used in ancient Greece and the ancient world from around 1500 BC to 300 BC. It is often roughly divided into the following periods: Mycenaean Greek ( c.  1400–1200 BC ), Dark Ages ( c.  1200–800 BC ), the Archaic or Epic period ( c.  800–500 BC ), and the Classical period ( c.  500–300 BC ). Ancient Greek was the language of Homer and of fifth-century Athenian historians, playwrights, and philosophers . It has contributed many words to English vocabulary and has been

11645-453: The goddess riding on a sea-goat. Brody describes her thus: ... a semi-nude female figure appears riding on a sea-goat, accompanied by a dolphin and a Triton. This is the goddess Aphrodite herself, shown here not in her distinctive local guise but in a more traditionally Hellenistic style. She is the marine aspect of Aphrodite, known to the Greeks as Aphrodite Pelagia  .... She rides on

11782-485: The hippocampal volume is seen to be restored by as much as 10%. This change is seen to be due to the reforming of the dendrites. This dendritic restoration can also happen when stress is removed. There is, however, evidence derived mainly from studies using rats that stress occurring shortly after birth can affect hippocampal function in ways that persist throughout life. Ancient Greek Ancient Greek ( Ἑλληνῐκή , Hellēnikḗ ; [hellɛːnikɛ́ː] ) includes

11919-617: The hippocampus neuronal genome of the rats at one hour and at 24 hours after training. These alterations in methylation pattern occurred at many genes that were down-regulated , often due to the formation of new 5-methylcytosine sites in CpG rich regions of the genome. Furthermore, many other genes were upregulated , likely often due to the removal of methyl groups from previously existing 5-methylcytosines (5mCs) in DNA. Demethylation of 5mC can be carried out by several proteins acting in concert, including TET enzymes as well as enzymes of

12056-421: The hippocampus and occurs at synapses that terminate on dendritic spines and use the neurotransmitter glutamate . The synaptic changes depend on a special type of glutamate receptor , the N -methyl-D-aspartate (NMDA) receptor , a cell surface receptor which has the special property of allowing calcium to enter the postsynaptic spine only when presynaptic activation and postsynaptic depolarization occur at

12193-400: The hippocampus are shown to be functionally and anatomically distinct. The dorsal hippocampus (DH), ventral hippocampus (VH) and intermediate hippocampus serve different functions, project with differing pathways, and have varying degrees of place cells. The dorsal hippocampus serves for spatial memory, verbal memory, and learning of conceptual information. Using the radial arm maze , lesions in

12330-439: The hippocampus as part of a larger medial temporal lobe memory system responsible for general declarative memory (memories that can be explicitly verbalized – these would include, for example, memory for facts in addition to episodic memory). The hippocampus also encodes emotional context from the amygdala . This is partly why returning to a location where an emotional event occurred may evoke that emotion. There

12467-479: The hippocampus during behavior and then later transferred to the neocortex during sleep. Sharp waves in Hebbian theory are seen as persistently repeated stimulations by presynaptic cells, of postsynaptic cells that are suggested to drive synaptic changes in the cortical targets of hippocampal output pathways. Suppression of sharp waves and ripples in sleep or during immobility can interfere with memories expressed at

12604-470: The hippocampus has been studied extensively as part of a brain system responsible for spatial memory and navigation. Many neurons in the rat and mouse hippocampus respond as place cells : that is, they fire bursts of action potentials when the animal passes through a specific part of its environment. Hippocampal place cells interact extensively with head direction cells , whose activity acts as an inertial compass, and conjecturally with grid cells in

12741-410: The hippocampus have shown that the hippocampus is required for the formation and recall, but not the storage, of memories. It has been shown that a decrease in the volume of various parts of the hippocampus in people leads to specific memory impairments. In particular, efficiency of verbal memory retention is related to the anterior parts of the right and left hippocampus. The right head of the hippocampus

12878-403: The hippocampus is dysfunctional, orientation is affected; people may have difficulty in remembering how they arrived at a location and how to proceed further. Getting lost is a common symptom of amnesia. Studies with animals have shown that an intact hippocampus is required for initial learning and long-term retention of some spatial memory tasks, in particular ones that require finding the way to

13015-427: The hippocampus more than of other parts of the brain. These effects show up in post-traumatic stress disorder , and they may contribute to the hippocampal atrophy reported in schizophrenia and severe depression . Anterior hippocampal volume in children is positively correlated with parental family income and this correlation is thought to be mediated by income related stress. A recent study has also revealed atrophy as

13152-539: The hippocampus of elderly people , but later studies using more precise techniques found only minimal differences. Similarly, some MRI studies have reported shrinkage of the hippocampus in elderly people, but other studies have failed to reproduce this finding. There is, however, a reliable relationship between the size of the hippocampus and memory performance; so that where there is age-related shrinkage, memory performance will be impaired. There are also reports that memory tasks tend to produce less hippocampal activation in

13289-529: The hippocampus to space. The spatial theory was originally championed by O'Keefe and Nadel, who were influenced by American psychologist E.C. Tolman's theories about " cognitive maps " in humans and animals. O'Keefe and his student Dostrovsky in 1971 discovered neurons in the rat hippocampus that appeared to them to show activity related to the rat's location within its environment. Despite skepticism from other investigators, O'Keefe and his co-workers, especially Lynn Nadel, continued to investigate this question, in

13426-593: The hippocampus was considered an appropriate decoration for mosaics in Roman thermae or public baths, as at Aquae Sulis modern day Bath in Britannia. Poseidon's horses, which were included in the elaborate sculptural program of gilt-bronze and ivory , added by a Roman client to the temple of Poseidon at Corinth , are likely to have been hippocampi; the Romanised Greek Pausanias described

13563-453: The hippocampus was reactivated, memory traces consolidated by non-hippocampal systems were not recalled, suggesting that the hippocampus interferes with long-term memory consolidation in other memory-related systems. One of the major implications that this model illustrates is the dominant effects of the hippocampus on non-hippocampal networks when information is incongruent. With this information in mind, future directions could lead towards

13700-483: The hippocampus was unchanged, as the increase seen in the posterior part was made at the expense of the anterior part, which showed a relative decrease in size. There have been no reported adverse effects from this disparity in hippocampal proportions. Another study showed opposite findings in blind individuals. The anterior part of the right hippocampus was larger and the posterior part was smaller, compared with sighted individuals. There are several navigational cells in

13837-410: The hippocampus, it has frequently been used as a model system for studying neurophysiology . The form of neural plasticity known as long-term potentiation (LTP) was initially discovered to occur in the hippocampus and has often been studied in this structure. LTP is widely believed to be one of the main neural mechanisms by which memories are stored in the brain. In rodents as model organisms ,

13974-561: The historical Dorians . The invasion is known to have displaced population to the later Attic-Ionic regions, who regarded themselves as descendants of the population displaced by or contending with the Dorians. The Greeks of this period believed there were three major divisions of all Greek people – Dorians, Aeolians, and Ionians (including Athenians), each with their own defining and distinctive dialects. Allowing for their oversight of Arcadian, an obscure mountain dialect, and Cypriot, far from

14111-476: The historical circumstances of the times imply that the overall groups already existed in some form. Scholars assume that major Ancient Greek period dialect groups developed not later than 1120 BC, at the time of the Dorian invasions —and that their first appearances as precise alphabetic writing began in the 8th century BC. The invasion would not be "Dorian" unless the invaders had some cultural relationship to

14248-577: The horse of Poseidon emerging from the sea and galloping across the Libyan sands. This compares to the specifically "two-hoofed" hippocampi of Gaius Valerius Flaccus in his Argonautica : " Orion when grasping his father’s reins heaves the sea with the snorting of his two-hooved horses." In Hellenistic and Roman imagery, however, Poseidon (or Roman Neptune ) often drives a sea- chariot drawn by hippocampi. Thus, hippocampi sport with this god in both ancient depictions and much more modern ones, such as in

14385-429: The horses, with the parts below the waist of ivory. On the car stand Amphitrite and Poseidon, and there is the boy Palaemon upright upon a dolphin . These too are made of ivory and gold. On the middle of the base on which the car has been wrought a Sea holding up the young Aphrodite , and on either side are the nymphs called Nereids . Hippocampi appear with the first Oriental-phase of Etruscan civilization : they remain

14522-432: The left posterior, left anterior or right anterior hippocampus demonstrate distinct, individual cell responses when presented with faces of presumably recognizable famous people. Associations among facial and vocal identity were similarly mapped to the hippocampus of rheseus monkeys. Single neurons in the CA1 and CA3 responded strongly to social stimulus recognition by MRI. The CA2 was not distinguished, and may likely comprise

14659-528: The level of the behavior, nonetheless, the newly formed CA1 place cell code can re-emerge even after a sleep with abolished sharp waves and ripples, in spatially non-demanding tasks. Since at least the time of Ramon y Cajal (1852–1934), psychologists have speculated that the brain stores memory by altering the strength of connections between neurons that are simultaneously active. This idea was formalized by Donald Hebb in 1949, but for many years remained unexplained. In 1973, Tim Bliss and Terje Lømo described

14796-551: The main olfactory bulb, the anterior olfactory nucleus, and to the primary olfactory cortex. There continues to be some interest in hippocampal olfactory responses, in particular, the role of the hippocampus in memory for odors, but few specialists today believe that olfaction is its primary function. Over the years, three main ideas of hippocampal function have dominated the literature: response inhibition , episodic memory , and spatial cognition. The behavioral inhibition theory (caricatured by John O'Keefe and Lynn Nadel as "slam on

14933-458: The medial septum is more than just the controller of theta; it is also the main source of cholinergic projections to the hippocampus. It has not been established that septal lesions exert their effects specifically by eliminating the theta rhythm. During sleep or during resting, when an animal is not engaged with its surroundings, the hippocampal EEG shows a pattern of irregular slow waves, somewhat larger in amplitude than theta waves. This pattern

15070-488: The moderate projections to two primary olfactory cortical areas and prelimbic areas of the medial prefrontal cortex . This region has the smallest number of place cells. The ventral hippocampus functions in fear conditioning and affective processes. Anagnostaras et al. (2002) showed that alterations to the ventral hippocampus reduced the amount of information sent to the amygdala by the dorsal and ventral hippocampus, consequently altering fear conditioning in rats. Historically,

15207-541: The most active of them. An active cell typically stays active for half a second to a few seconds. As the rat behaves, the active cells fall silent and new cells become active, but the overall percentage of active cells remains more or less constant. In many situations, cell activity is determined largely by the spatial location of the animal, but other behavioral variables also clearly influence it. The LIA mode appears during slow-wave (non-dreaming) sleep, and also during states of waking immobility such as resting or eating. In

15344-439: The most intensively studied subject in medical history. In the ensuing years, other patients with similar levels of hippocampal damage and amnesia (caused by accident or disease) have also been studied, and thousands of experiments have studied the physiology of activity-driven changes in synaptic connections in the hippocampus. There is now universal agreement that the hippocampi play some sort of important role in memory; however,

15481-464: The neighboring entorhinal cortex . The earliest description of the ridge running along the floor of the temporal horn of the lateral ventricle comes from the Venetian anatomist Julius Caesar Aranzi (1587), who likened it first to a silkworm and then to a seahorse ( Latin hippocampus , from Greek ἱππόκαμπος, from ἵππος, 'horse' + κάμπος, 'sea monster'). The German anatomist Duvernoy (1729),

15618-508: The older dialects, although the Doric dialect has survived in the Tsakonian language , which is spoken in the region of modern Sparta. Doric has also passed down its aorist terminations into most verbs of Demotic Greek . By about the 6th century AD, the Koine had slowly metamorphosed into Medieval Greek . Phrygian is an extinct Indo-European language of West and Central Anatolia , which

15755-408: The outer in – the molecular layer , the inner molecular layer , the granular layer , and the hilus . The CA3 in the hippocampus proper has the following cell layers known as strata: lacunosum-moleculare, radiatum, lucidum, pyramidal, and oriens. CA2 and CA1 also have these layers except the lucidum stratum . The input to the hippocampus (from varying cortical and subcortical structures) comes from

15892-421: The output to the EC, additional output pathways go to other cortical areas including the prefrontal cortex . A major output goes via the fornix to the lateral septal area and to the mammillary body of the hypothalamus (which the fornix interconnects with the hippocampus). The hippocampus receives modulatory input from the serotonin , norepinephrine , and dopamine systems, and from the nucleus reuniens of

16029-487: The perfect stem eilēpha (not * lelēpha ) because it was originally slambanō , with perfect seslēpha , becoming eilēpha through compensatory lengthening. Reduplication is also visible in the present tense stems of certain verbs. These stems add a syllable consisting of the root's initial consonant followed by i . A nasal stop appears after the reduplication in some verbs. The earliest extant examples of ancient Greek writing ( c.  1450 BC ) are in

16166-442: The phase with which theta rhythms, at the time of stimulation of a neuron, shape the effect of that stimulation upon its synapses. What is meant here is that theta rhythms may affect those aspects of learning and memory that are dependent upon synaptic plasticity . It is well established that lesions of the medial septum  – the central node of the theta system – cause severe disruptions of memory. However,

16303-430: The point of near convergence. In an attempt to reconcile the two disparate views, it is suggested that a broader view of the hippocampal function is taken and seen to have a role that encompasses both the organisation of experience ( mental mapping , as per Tolman's original concept in 1948) and the directional behaviour seen as being involved in all areas of cognition, so that the function of the hippocampus can be viewed as

16440-517: The precise nature of this role remains widely debated. A recent theory proposed – without questioning its role in spatial cognition – that the hippocampus encodes new episodic memories by associating representations in the newborn granule cells of the dentate gyrus and arranging those representations sequentially in the CA3 by relying on the phase precession generated in the entorhinal cortex . The third important theory of hippocampal function relates

16577-406: The pyramidal cells and then give an inhibitory feedback to the pyramidal cells. This recurrent inhibition is a simple feedback circuit that can dampen excitatory responses in the hippocampus. The pyramidal cells give a recurrent excitation which is an important mechanism found in some memory processing microcircuits. Several other connections play important roles in hippocampal function. Beyond

16714-606: The results of surgical destruction of the hippocampi when trying to relieve epileptic seizures in an American man Henry Molaison , known until his death in 2008 as "Patient H.M." The unexpected outcome of the surgery was severe anterograde and partial retrograde amnesia ; Molaison was unable to form new episodic memories after his surgery and could not remember any events that occurred just before his surgery, but he did retain memories of events that occurred many years earlier extending back into his childhood. This case attracted such widespread professional interest that Molaison became

16851-417: The rich ensemble in the later 2nd century AD ( Geography of Greece ii.1.7-.8): On the temple, which is not very large, stand bronze Tritons . In the fore-temple are images, two of Poseidon, a third of Amphitrite , and a Sea, which also is of bronze. The offerings inside were dedicated in our time by Herodes Atticus , four horses, gilded except for the hoofs, which are of ivory, and two gold Tritons beside

16988-449: The same period from Byblos show a hippocampus diving under a galley. A gold sea-horse was discovered in a hoard from the kingdom of Lydia in Asia minor , dating to the 6th century BC. In the Iliad , Homer describes Poseidon , god of horses, earthquakes, and the sea, driving a chariot drawn by brazen -hoofed horses over the sea's surface, and Apollonius of Rhodes , describes

17125-465: The same time. Drugs that interfere with NMDA receptors block LTP and have major effects on some types of memory, especially spatial memory. Genetically modified mice that are modified to disable the LTP mechanism, also generally show severe memory deficits. Age-related conditions such as Alzheimer's disease and other forms of dementia (for which hippocampal disruption is one of the earliest signs) have

17262-412: The set of structures that line the deep edge of the cortex (Latin limbus meaning border ): These include the hippocampus, cingulate cortex , olfactory cortex , and amygdala . Paul MacLean later suggested that the limbic structures comprise the neural basis of emotion. The hippocampus is anatomically connected to parts of the brain that are involved with emotional behavior – the septum ,

17399-422: The source of their seizures , with a view to surgical resection. The patients had diagnostic electrodes implanted in their hippocampus and then used a computer to move around in a virtual reality town. Similar brain imaging studies in navigation have shown the hippocampus to be active. A study was carried out on taxi drivers. London's black cab drivers need to learn the locations of a large number of places and

17536-474: The spiking of hippocampal neurons and synchronise across the hippocampus in a travelling wave pattern. The trisynaptic circuit is a relay of neurotransmission in the hippocampus that interacts with many brain regions. From rodent studies it has been proposed that the trisynaptic circuit generates the hippocampal theta rhythm. Theta rhythmicity is very obvious in rabbits and rodents and also clearly present in cats and dogs. Whether theta can be seen in primates

17673-445: The study of these non-hippocampal memory systems through hippocampal inactivation, further expanding the labile constructs of memory. Additionally, many theories of memory are holistically based around the hippocampus. This model could add beneficial information to hippocampal research and memory theories such as the multiple trace theory . Lastly, the between-system memory interference model allows researchers to evaluate their results on

17810-517: The syllabic script Linear B . Beginning in the 8th century BC, however, the Greek alphabet became standard, albeit with some variation among dialects. Early texts are written in boustrophedon style, but left-to-right became standard during the classic period. Modern editions of ancient Greek texts are usually written with accents and breathing marks , interword spacing , modern punctuation , and sometimes mixed case , but these were all introduced later. The beginning of Homer 's Iliad exemplifies

17947-401: The theta mode, the EEG is dominated by large regular waves with a frequency range of 6 to 9 Hz , and the main groups of hippocampal neurons ( pyramidal cells and granule cells ) show sparse population activity, which means that in any short time interval, the great majority of cells are silent, while the small remaining fraction fire at relatively high rates, up to 50 spikes in one second for

18084-425: The theta wave are generated mainly by densely packed neural layers of the entorhinal cortex, CA3, and the dendrites of pyramidal cells. The theta wave is one of the largest signals seen on EEG, and is known as the hippocampal theta rhythm . In some situations the EEG is dominated by regular waves at 3 to 10 Hz, often continuing for many seconds. These reflect subthreshold membrane potentials and strongly modulate

18221-506: The top of its central tower. Closely related to the hippocampus is the "sea goat", represented by Capricorn , a mythical creature with the front half of a goat and the rear half of a fish. Canonical figures, most of which were not themselves cult images , and coins of the Carian goddess associated with Aphrodite as the Aphrodite of Aphrodisias through interpretatio graeca , show

18358-462: The waters of the 18th-century Trevi Fountain in Rome surveyed by Neptune from his niche above. The appearance of hippocampi in both freshwater and saltwater is counter-intuitive to a modern audience, though not to an ancient one. The Greek picture of the natural hydrological cycle did not take into account the condensation of atmospheric water as rain to replenish the water table , but imagined

18495-526: The waters of the sea oozing back landwards through vast caverns and aquifers , rising replenished and freshened in springs. Thus, it was natural for a temple at Helike in the coastal plain of Achaea to be dedicated to Poseidon Helikonios , (the Poseidon of Helicon), the sacred spring of Boeotian Helikon . When an earthquake suddenly submerged the city, the temple's bronze Poseidon accompanied by hippocampi continued to snag fishermens' nets. Likewise,

18632-480: Was Aeolic. For example, fragments of the works of the poet Sappho from the island of Lesbos are in Aeolian. Most of the dialect sub-groups listed above had further subdivisions, generally equivalent to a city-state and its surrounding territory, or to an island. Doric notably had several intermediate divisions as well, into Island Doric (including Cretan Doric ), Southern Peloponnesus Doric (including Laconian ,

18769-460: Was suggested that the mechanisms of memory and planning both evolved from mechanisms of navigation and that their neuronal algorithms were basically the same. Many studies have made use of neuroimaging techniques such as functional magnetic resonance imaging (fMRI), and a functional role in approach-avoidance conflict has been noted. The anterior hippocampus is seen to be involved in decision-making under approach-avoidance conflict processing. It

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