The hypoglossal nerve is the twelfth cranial nerve, innervates all the extrinsic and intrinsic muscles of the tongue, except for the palatoglossus, innervated by the vagus nerve. It is a nerve with a motor function; the nerve arises from the hypoglossal nucleus in the brain stem as a number of small rootlets, passes through the hypoglossal canal and down through the neck, passes up again over the tongue muscles it supplies into the tongue. There are two hypoglossal nerves in the body: one on the left, one on the right; the nerve is involved in controlling tongue movements required for speech and swallowing, including sticking out the tongue and moving it from side to side. Damage to the nerve or the neural pathways which control it can affect the ability of the tongue to move and its appearance, with the most common sources of damage being injury from trauma or surgery, motor neuron disease; the first recorded description of the nerve is by Herophilos in the third century BC. The name hypoglossus springs from the fact that its passage is below the tongue, from hypo and glossa.
The hypoglossal nerve arises as a number of small rootlets from the front of the medulla, the bottom part of the brainstem, in the preolivary sulcus, which separates the olive and the pyramid. The nerve passes through the subarachnoid space and pierces the dura mater near the hypoglossal canal, an opening in the occipital bone of the skull. After emerging from the hypoglossal canal, the hypoglossal nerve gives off a meningeal branch and picks up a branch from the anterior ramus of C1, it travels close to the vagus nerve and spinal division of the accessory nerve, spirals downwards behind the vagus nerve and passes between the internal carotid artery and internal jugular vein lying on the carotid sheath. At a point at the level of the angle of the mandible, the hypoglossal nerve emerges from behind the posterior belly of the digastric muscle, it loops around a branch of the occipital artery and travels forward into the region beneath the mandible. The hypoglossal nerve moves forward lateral to the hyoglossus and medial to the stylohyoid muscles and lingual nerve.
It continues forward to the tip of the tongue. It distributes branches to the intrinsic and extrinsic muscle of the tongue innervates as it passes in this direction, supplies several muscles that it passes; the rootlets of the hypoglossal nerve arise from the hypoglossal nucleus near the bottom of the brain stem. The hypoglossal nucleus receives input from both the motor cortices but the contralateral input is dominant. Signals from muscle spindles on the tongue travel through the hypoglossal nerve, moving onto the lingual nerve which synapses on the trigeminal mesencephalic nucleus; the hypoglossal nerve is derived from the first pair of occipital somites, collections of mesoderm that form next to the main axis of an embryo during development. The musculature it supplies develop as the hypoglossal cord from the myotomes of the first four pairs of occipital somites; the nerve is first visible as a series of roots in the fourth week of development, which have formed a single nerve and link to the tongue by the fifth week.
The hypoglossal nucleus is derived from the basal plate of the embryonic medulla oblongata. The hypoglossal nerve provides motor control of the extrinsic muscles of the tongue: genioglossus, hyoglossus and the intrinsic muscles of the tongue; these represent all muscles of the tongue except the palatoglossus muscle. The hypoglossal nerve is of a general somatic efferent type; these muscles are involved in manipulating the tongue. The left and right genioglossus muscles in particular are responsible for protruding the tongue; the muscles, attached to the underside of the top and back parts of the tongue, cause the tongue to protrude and deviate towards the opposite side. The hypoglossal nerve supplies movements including clearing the mouth of saliva and other involuntary activities; the hypoglossal nucleus interacts with the reticular formation, involved in the control of several reflexive or automatic motions, several corticonuclear originating fibers supply innervation aiding in unconscious movements relating to speech and articulation.
Reports of damage to the hypoglossal nerve are rare. The most common causes of injury in one case series were compression by tumours and gunshot wounds. A wide variety of other causes can lead to damage of the nerve; these include surgical damage, medullary stroke, multiple sclerosis, Guillain-Barre syndrome, infection and presence of an ectatic vessel in the hypoglossal canal. Damage can be on both sides, which will affect symptoms that the damage causes; because of the close proximity of the nerve to other structures including nerves and veins, it is rare for the nerve to be damaged in isolation. For example, damage to the left and right hypoglossal nerves may occur with damage to the facial and trigeminal nerves as a result of damage from a clot following arteriosclerosis of the vertebrobasilar artery; such a stroke may result in tight oral musculature, difficulty speaking and chewing. Progressive bulbar palsy, a form of motor neuron disease, is associated with combined lesions of the hypoglossal nucleus and nucleus ambiguus with wasting of the motor nerves of the pons and medulla.
This may cause difficulty with tongue movements, speech and swallowing caused by dysfunction of several cranial nerve nuclei. Motor neuron disease is the most common disease affecting the hypoglossal nerve; the hypoglossal nerve is tested by examining its movements. At rest, if the
Inferior temporal gyrus
The inferior temporal gyrus is placed below the middle temporal gyrus, is connected behind with the inferior occipital gyrus. This region is one of the higher levels of the ventral stream of visual processing, associated with the representation of complex object features, such as global shape, it may be involved in face perception, in the recognition of numbers. The inferior temporal gyrus is the anterior region of the temporal lobe located underneath the central temporal sulcus; the primary function of the occipital temporal gyrus – otherwise referenced as IT cortex – is associated with visual stimuli processing, namely visual object recognition, has been suggested by recent experimental results as the final location of the ventral cortical visual system. The IT cortex in humans is known as the Inferior Temporal Gyrus since it has been located to a specific region of the human temporal lobe; the IT processes visual stimuli of objects in our field of vision, is involved with memory and memory recall to identify that object.
This region processes the color and form of the object in the visual field and is responsible for producing the “what” from this visual stimuli, or in other words identifying the object based on the color and form of the object and comparing that processed information to stored memories of objects to identify that object. The IT cortex’s neurological significance is not just its contribution to the processing of visual stimuli in object recognition but has been found to be a vital area with regards to simple processing of the visual field, difficulties with perceptual tasks and spatial awareness, the location of unique single cells that explain the IT cortex’s relation to memory; the temporal lobe is unique to primates. In humans, the IT cortex is more complex than their relative primate counterparts; the human inferior temporal cortex consists of the inferior temporal gyrus, the middle temporal gyrus, the fusiform gyrus. When looking at the brain laterally –, from the side and looking at the surface of the temporal lobe – the inferior temporal gyrus is along the bottom portion of the temporal lobe, is separated from the middle temporal gyrus located directly above by the inferior temporal sulcus.
Additionally, some processing of the visual field that corresponds to the ventral stream of visual processing occurs in the lower portion of the superior temporal gyrus closest to the superior temporal sulcus. The medial and ventral view of the brain – meaning looking at the medial surface from below the brain, facing upwards – reveals that the inferior temporal gyrus is separated from the fusiform gyrus by the occipital-temporal sulcus; this human inferior temporal cortex is much more complex than that of other primates: non-human primates have an inferior temporal cortex, not divided into unique regions such as humans' inferior temporal gyrus, fusiform gyrus, or middle temporal gyrus. This region of the brain corresponds to the inferior temporal cortex and is responsible for visual object recognition and receives processed visual information; the inferior temporal cortex in primates has specific regions dedicated to processing different visual stimuli processed and organized by the different layers of the striate cortex and extra-striate cortex.
The information from the V1 –V5 regions of the geniculate and tectopulvinar pathways are radiated to the IT cortex via the ventral stream: visual information related to the color and form of the visual stimuli. Through comparative research between primates – humans and non-human primates – results indicate that the IT cortex plays a significant role in visual shape processing; this is supported by functional magnetic resonance imaging data collected by researchers comparing this neurological process between humans and macaques. The light energy that comes from the rays bouncing off of an object is converted into chemical energy by the cells in the retina of the eye; this chemical energy is converted into action potentials that are transferred through the optic nerve and across the optic chiasm, where it is first processed by the lateral geniculate nucleus of the thalamus. From there the information is sent to the primary visual cortex, region V1, it travels from the visual areas in the occipital lobe to the parietal and temporal lobes via two distinct anatomical streams.
These two cortical visual systems were classified by Mishkin. One stream travels ventrally to the inferior temporal cortex while the other travels dorsally to the posterior parietal cortex, they are labeled the “what” and “where” streams, respectively. The Inferior Temporal Cortex receives information from the ventral stream, understandably so, as it is known to be a region essential in recognizing patterns and objects; the understanding at the single-cell level of the IT cortex and its role of utilizing memory to identify objects and or process the visual field based on color and form visual information is a recent in neuroscience. Early research indicated that the cellular connections of the temporal lobe to other memory associated areas of the brain – namely the hippocampus, the amygdala, the prefrontal cortex, among others; these cellular connections have been found to explain unique elements of memory, suggesting that unique single-cells can be linked to specific unique types and specific memories.
Research into the single-cell understanding of the IT cortex reveals
Middle cerebral artery
The middle cerebral artery is one of the three major paired arteries that supply blood to the cerebrum. The MCA arises from the internal carotid and continues into the lateral sulcus where it branches and projects to many parts of the lateral cerebral cortex, it supplies blood to the anterior temporal lobes and the insular cortices. The left and right MCAs rise from trifurcations of the internal carotid arteries and thus are connected to the anterior cerebral arteries and the posterior communicating arteries, which connect to the posterior cerebral arteries; the MCAs are not considered a part of the Circle of Willis. The middle cerebral artery can be classified into 4 parts: M1: The sphenoidal segment, so named due to its origin and loose lateral tracking of the sphenoid bone. Although known as the horizontal segment, this may be misleading since the segment may descend, remain flat, or extend posteriorly the anterior in different individuals; the M1 segment perforates the brain with numerous anterolateral central arteries, which irrigate the basal ganglia.
M2: Extending anteriorly on the insula, this segment in known as the insular segment. It is known as the Sylvian segment when the opercular segments are included; the MCA branches may bifurcate or sometimes trifurcate into trunks in this segment which extend into branches that terminate towards the cortex. M3: The opercular segments and extends laterally exteriorly from the insula towards the cortex; this segment is sometimes grouped as part of M2. M4: These finer terminal or cortical segments irrigate the cortex, they begin at the external of the Sylvian fissure and extend distally away on the cortex of the brain. The M2 and M3 segments may each split into 2 or 3 main trunks with an upper trunk, lower trunk and a middle trunk. Bifurcations and trifurcations occurs in 50% and 25% of the cases respectively. Other cases include duplication of the MCA at the internal carotid artery or an accessory MCA which arise not from the ICA but as a branch from the anterior cerebral artery; the middle trunk that exist in parts of the population, when present provides the pre-Rolandic, anterior parietal, posterior parietal and the angular artery for irrigation instead of the upper and lower trunks.
The branches of the MCA can be described by the areas. Lateral frontobasal: This artery branches out anteriorly and laterally to vascularize the inferior frontal gyrus, it "competes" in size with the frontal polar branch of the anterior cerebral artery Prefrontal arteries: These arteries fan out over the insula and exit to the cortex via the medial surface of the frontal operculum. The arteries fan superiorly over the pars triangularis and vascularize the inferior and middle frontal gyrus. Near the superior frontal gyrus these arteries anastamose with branches from the pericallosal artery of the anterior cerebral artery. Pre-Rolandic artery: The artery extends out on the medial surface of the operculum and supplies the posterior parts of the middle and inferior frontal gyri as well as the lower parts of the pre-central gyrus; this artery branches once or twice and is invariant across anatomies. Rolandic arteries: The artery extends out and exits from the central portion of the operculum passes inside the central sulcus.
This artery bifurcates in 72% of individuals and irrigates the posterior pre-central gyrus and the inferior portion of the post-central gyrus. Anterior parietal: This artery originates from the anterior or middle MCA trunk. In some cases it branches from the posterior parietal artery, it extends the length of interparietal sulcus and descends posteriorly. Posterior parietal: Emerges from the posterior end of the Sylvian fissure and extends first posteriorly, anteriorly along the posterior of the parietal lobe, it branches to the supramarginal gyrus. Angular: The angular artery is a significant terminal branch of the anterior or middle trunk of the MCA, it emerges from the Sylvian fissure and passes over the anterior transverse temporal gyrus and divides into two branches. One of the branches supplies the angular gyrus while the other supplies the supramarginal gyrus, posterior superior temporal gyrus, the parietooccipital arcus. Temporooccipital: The longest cortical artery, it runs posteriorly opposite to the center of the operculum.
Upon its exit from the Sylvian fissure, it runs parallel to the superior temporal sulcus and supplies the superior and inferior occipital gyri. This vessel anastamoses with the posterior cerebral artery and may exist as one or two arteries, 67% or 33% of the time, respectively. Temporopolar: The artery extends from the sphenoidal segment of the MCA via the inferior surface of the operculum and supplies the polar and anterior lateral portions of the temporal lobe; the vessel can be identified in 52% of normal angiograms Anterior temporal: This artery extends in the similar fashion as the temporopolar artery and vascularizes the same regions. Middle temporal: This artery extends from the Sylvian fissure opposite to the inferior frontal gyrus and supplies superior and middle portions of the middle temporal lobe, it can be identified in 79% of angiograms. Posterior temporal: This artery extends out and away from the operculum and turns in a step-wise manner first inferiorly posteriorly into the superior temporal sulcus to the middle temporal sulcus.
This vessel supplies posterior portion of the temporal lobe and is the origin of several perforating arteries that irrigate the insula. It is identifiable in most radiograms. Areas supplied by the middle cerebral artery include: The bulk of the lateral sur
The third ventricle is one of four connected fluid-filled cavities comprising the ventricular system within the mammalian brain. It is a median cleft in the diencephalon between the two thalami, is filled with cerebrospinal fluid, it is between the left and right lateral ventricles. Running through the third ventricle is the interthalamic adhesion, which contains thalamic neurons and fibers that may connect the two thalami; the third ventricle is a narrow, laterally flattened, vaguely rectangular region, filled with cerebrospinal fluid, lined by ependyma. It is connected at the superior anterior corner to the lateral ventricles, by the foramina of Monro, becomes the cerebral aqueduct at the posterior caudal corner. Since the foramina of Monro are on the lateral edge, the corner of the third ventricle itself forms a bulb, known as the anterior recess; the roof of the ventricle comprises choroid plexus, forming the inferior central portion of the tela choroidea. The lateral side of the ventricle is marked by a sulcus - the hypothalamic sulcus - from the inferior side of the foramina of Monro to the anterior side of the cerebral aqueduct.
The lateral border posterior/superior of the sulcus constitutes the thalamus, while anterior/inferior of the sulcus it constitutes the hypothalamus. The interthalamic adhesion tunnels through the thalamic portion of the ventricle, joining together the left and right halves of the thalamus, although it is sometimes absent, or split into more than one tunnel through the ventricle; the posterior border of the ventricle constitutes the epithalamus. The superior part of the posterior border constitutes the habenular commissure, while more centrally it the pineal gland, which regulates sleep and reacts to light levels. Caudal of the pineal gland is the posterior commissure; the commissures create concavity to the shape of the posterior ventricle border, causing the suprapineal recess above the habenular, the deeper pineal recess between the habenular and posterior commissures. The anterior wall of the ventricle forms the lamina terminalis, within which the vascular organ monitors and regulates the osmotic concentration of the blood.
The optic recess - marks the inferior end of the lamina terminalis, with the optic chiasm forming the adjacent floor. The portion of the floor posterior of the optic chiasm distends inferiorly, anteriorly, to form a funnel; the border of the funnel is the tuber cinereum, which constitutes a bundle of nerve fibres from the hypothalamus. The funnel ends in the posterior lobe of the pituitary gland, thus neurally connected to the hypothalamus via the tuber cinereum. A venous sinus surrounds the superior portion of the tuber cinereum; the mammillary bodies form the floor posterior of the tuber cinereum, acting as the link between the fornix and the hypothalamus. Posterior of the mamillary bodies, the ventricle becomes the opening of the cerebral aqueduct, the inferior borders becoming the crus cerebri of the midbrain; the third ventricle, like other parts of the ventricular system of the brain, develops from the neural canal of the neural tube. It originates from the most rostral portion of the neural tube which expands to become the prosencephalon.
The lamina terminalis is the rostral termination of the neural tube. After about five weeks, different portions of the prosencephalon begin to take distinct developmental paths from one another - the more rostral portion becomes the telencephalon, while the more caudal portion becomes the diencephalon; the telencephalon expands laterally to a much greater extent than it does dorsally or ventrally, its connection to the remainder of the neural tube reduces to the foramina of Monro. The diencephalon expands more evenly; the third ventricle is the space formed by the expanding canal of the diencephalon. The hypothalamic region of the ventricle develops from the ventral portion of the neural tube, while the thalamic region develops from the dorsal portion; the hypothalamic area of the ventricle begins to distend ventrally during the 5th week of development, creating the infundibulum and posterior pituitary. The optic recess is noticeable by the end of the 6th week, by which time a bend is distinguishable in the dorsal portion of the ventricle border.
Rostral of the bend, the medial dorsal portion of the ventrical begins to flatten, become secretory, forming the roof of the ventricle. Caudal of the bend, the ventricle border forms the epithalamus, begins to distend towards the pareital bone.
An anastomosis is a connection or opening between two things that are diverging or branching, such as between blood vessels, leaf veins, or streams. Such a connection may be abnormal; the reestablishment of an anastomosis that had become blocked is called a reanastomosis. Anastomoses that are abnormal, whether congenital or acquired, are called fistulas; the term is used in medicine, mycology, geology and architecture. Anastomosis: medical or Modern Latin, from Greek ἀναστόμωσις, anastomosis, "outlet, opening", Gr ana- "up, on, upon", stoma "mouth", "to furnish with a mouth", thus the - stom - syllable is cognate with that of stoma in stoma in medicine. An anastomosis is the connection of two divergent structures, it refers to connections between blood vessels or between other tubular structures such as loops of intestine. In circulatory anastomoses, many arteries anastomose with each other; the circulatory anastomosis is further divided into venous anastomosis. Arterial anastomosis includes potential arterial anastomosis.
Anastomoses form alternative routes around capillary beds in areas that don't need a large blood supply, thus helping regulate systemic blood flow. An example of surgical anastomosis occurs when a segment of intestine, blood vessel, or any other structure are connected together. Examples include Roux-en-Y anastomosis or ureteroureterostomy. Surgical anastamosis techniques include Linear Stapled Anastomosis, Hand Sewn Anastomosis, End-to-End Anastomosis. Anastomosis can with an anastomosis assist device. Studies have been performed comparing various anastomosis approaches taking into account surgical "time and cost, postoperative anastomotic bleeding and stricture". Pathological anastomosis results from trauma or disease and may involve veins, arteries, or intestines; these are referred to as fistulas. In the cases of veins or arteries, traumatic fistulas occur between artery and vein. Traumatic intestinal fistulas occur between two loops of intestine or intestine and skin. Portacaval anastomosis, by contrast, is an anastomosis between a vein of the portal circulation and a vein of the systemic circulation, which allows blood to bypass the liver in patients with portal hypertension resulting in hemorrhoids, esophageal varices, or caput medusae.
In evolution, anastomosis is a recombination of evolutionary lineage. Conventional accounts of evolutionary lineage present themselves as the simple branching out of species into novel forms. Under anastomosis, species might recombine after initial branching out, such as in the case of recent research that shows that ancestral populations along human and chimpanzee lineages may have interbred after an initial branching event; the concept of anastomosis applies to the theory of symbiogenesis, in which new species emerge from the formation of novel symbiotic relationships. In mycology, anastomosis is the fusion between branches of the different hyphae. Hence the bifurcating fungal hyphae can form true reticulating networks. By sharing materials in the form of dissolved ions and nucleotides, the fungus maintains bidirectional communication with itself; the fungal network might begin from several origins. Once encountering the tip of another expanding, exploring self, the tips press against each other in pheromonal recognition or by an unknown recognition system, fusing to form a genetic singular clonal colony that can cover hectares called a genet or just microscopical areas.
For fungi, anastomosis is a component of reproduction. In some fungi, two different haploid mating types -- -- merge. Somatically, they form a morphologically similar mycelial wave front that continues to grow and explore; the significant difference, is that each septated unit is binucleate, containing two unfused nuclei, i.e. one from each parent that undergoes karyogamy and meiosis to complete the sexual cycle. The term "anastomosing" is used for mushroom gills which interlink and separate to form a network. In geology, anastomosis refers to quartz veins displaying this property, related to shearing in metamorphic regions. Anastomosing streams consist of multiple channels that divide and reconnect and are separated by semi-permanent banks formed of cohesive material, such that they are unlikely to migrate from one channel position to another, they can be confused with braiding, the splitting of a river by sand bars or hard rocks and some definitions require that an anastomosing river be made up of interconnected channels that enclose floodbasins.
Rivers with anastomosed reaches include the Magdalena River in Colombia, the upper Columbia River in British Columbia and the upper Narew River in Poland. The term anabranch has been used for segments of anastamosing rivers
The tela choroidea is a region of meningeal pia mater and underlying ependyma that gives rise to the choroid plexus in each of the brain’s four ventricles. Tela is used to describe a web-like membrane or layer; the tela choroidea is a thin part of the loose connective tissue of pia mater that overlies and adheres to the ependyma with no intervening tissue. It has a rich blood supply; the ependyma and vascular pia mater that make up the tela choroidea form regions of minute projections known as a choroid plexus that projects into each ventricle. The choroid plexus produces the cerebrospinal fluid of the ventricular system; the tela choroidea in the ventricles forms from different parts of the roof plate in the development of the embryo. In the lateral ventricles the tela choroidea–a double-layered fold of pia mater and ependyma, produces the choroid fissure; the choroid fissure is C-shaped, runs between the fornix and the thalamus in the body of the ventricle, between the stria terminalis and hippocampal fimbria in the inferior horn, is the location of the attachment of the margins of the choroid plexus.
In the choroid fissure of the lateral ventricles, the tela choroidea is a lateral extension of the tela choroidea from the third ventricle. In the third ventricle the tela choroidea forms the roof of the ventricle. Two vascular fringes from the lower fold form the choroid plexus; the tela choroidea of the fourth ventricle is a double layer of pia mater and ependyma, between the cerebellum and the lower part of the roof of the fourth ventricle. The two layers are continuous with each other in front, are adherent throughout; the anterior layer of the fold, contains vascular fringes. The anterior layer is continuous inferiorly with the pia mater on the inferior cerebellar peduncles and the closed part of the medulla oblongata; the posterior layer covers the antero-inferior surface of the cerebellum. The blood supply of these plexuses is from the posterior inferior cerebellar artery; the lateral ventricles contains the right and left internal cerebral veins at its roof. The arteries carrying blood into the choroid plexuses are: the anterior choroidal artery.
The posterior choroidal artery. Medial posterior choroidal branches run forward beneath the splenium of the corpus callosum, supply the tela chorioidea of the third ventricle and the choroid plexus
The fusiform gyrus known as the lateral occipitotemporal gyrus, is part of the temporal lobe and occipital lobe in Brodmann area 37. The fusiform gyrus is located between the lingual gyrus and parahippocampal gyrus above, the inferior temporal gyrus below. Though the functionality of the fusiform gyrus is not understood, it has been linked with various neural pathways related to recognition. Additionally, it has been linked to various neurological phenomena such as synesthesia and prosopagnosia. Anatomically, the fusiform gyrus is the largest macro-anatomical structure within the ventral temporal cortex, which includes structures involved in high-level vision; the term fusiform gyrus refers to the fact that the shape of the gyrus is wider at its centre than at its ends. This term is based on the description of the gyrus by Emil Huschke in 1854.. The fusiform gyrus is situated at the basal surface of the temporal and occipital lobes and is delineated by the collateral sulcus and occipitotemporal sulcus, respectively.
The OTS separates the fusiform gyrus from the inferior temporal gyrus and the CoS separates the fusiform gyrus from the parahippocampal gyrus. The fusiform gyrus can be further delineated into a lateral and medial portion, as it is separated in its middle by the shallow mid-fusiform sulcus. Thus, the lateral fusiform gyrus is delineated by the MFS medially; the medial fusiform gyrus is delineated by the MFS laterally and the CoS medially. The mid-fusiform sulcus serves as a macroanatomical landmark for the fusiform face area, a functional subregion of the fusiform gyrus assumed to play a key role in processing faces; the fusiform gyrus has a contentious history, clarified. The term was first used in 1854 by Emil Huschke from Jena, who called the fusiform gyrus a “Spindelwulst”, he chose this term because of the similarity that the respective cerebral gyrus bears to the shape of a spindle, or fusil, due to its wider central section. At first, researchers located the fusiform gyrus in other mammals as well, without taking into account the variations in gross organizations of other species’ brains.
Today, the fusiform gyrus is considered to be specific to hominoids. This is supported by research showing no fusiform gyrus in macaques; the first accurate definition of the mid-fusiform sulcus was coined by Gustav Retzius in 1896. He was the first to describe the sulcus sagittalis gyri fusiformis, determined that a sulcus divides the fusiform gyrus into lateral and medial partitions. W. Julius Mickle mentioned the mid-fusiform sulcus in 1897 and attempted to clarify the relation between temporal sulci and the fusiform gyrus, calling it the “intra-gyral sulcus of the fusiform lobule”; the exact functionality of the fusiform gyrus is still disputed, but there is relative consensus on its involvement in the following pathways: In 2003, V. S. Ramachandran collaborated with scientists from the Salk Institute for Biological Studies in order to identify the potential role of the fusiform gyrus within the color processing pathway in the brain. Examining the relationship within the pathway in cases of synesthesia, Ramachandran found that synesthetes on average have a higher density of fibers surrounding the angular gyrus.
The angular gyrus is involved in higher processing of colors. The fibers relay shape information from the fusiform gyrus to the angular gyrus in order to produce the association of colors and shapes in grapheme-color synesthesia. Cross-activation between the angular and fusiform gyri has been observed in the average brain, implying that the fusiform gyrus communicates with the visual pathway. Portions of the fusiform gyrus are critical for body recognition, it is believed. Further research by MIT scientists showed that the left and right fusiform gyri played different roles, which subsequently interlinked; the left fusiform gyrus recognizes "face-like" features in objects that may or may not be actual faces, whereas the right fusiform gyrus determines if that recognized face-like feature is, in fact, a face. In a 2015 study, dopamine was proposed to play a key role in face recognition task, was considered to be related to neural activity in fusiform gyrus. By studying the correlation between the binding potential of dopamine D1 receptor by PET and blood-oxygen-level-dependent in fMRI scan during a face recognition task, higher availability of D1 receptor was shown to be associated with higher BOLD level.
This study showed that this association with D1 BP is only significant for FFG, not other brain regions. The researchers showed the possibility that higher availability of dopamine D1 receptor may underlie better performance in face recognition task. Why is dopamine release linked to face recognition related BOLD activity? Dopamine is known to be related to the reward system. Dopaminergic system shows active response to stimuli; as a social demand, face recognition task could be a cognition process that involves dopamine, which can elicit a reinforcement feedback. But how may dopamine regulate FFG activity during face recognition task? A 2007 study indicates that BOLD activity can be modulated by dopamine’s influence on postsynaptic D1 receptors; the regulation is achieved in a way that dopamine first influence post-synaptic potential, th