Common peroneal nerve
The common fibular nerve is a nerve in the lower leg that provides sensation over the posterolateral part of the leg and the knee joint. It divides at the knee into two terminal branches: the superficial fibular nerve and deep fibular nerve, which innervate the muscles of the lateral and anterior compartments of the leg respectively; when the common fibular nerve is damaged or compressed, foot drop can be the end result. The common fibular nerve is the smaller terminal branch of the sciatic nerve; the common fibular nerve has root values of L4, L5, S1, S2. It arises from the superior angle of the popliteal fossa and extends to the lateral angle of the popliteal fossa, along the medial border of the biceps femoris, it winds around the neck of the fibula to pierce the fibularis longus and divides into terminal branches of superficial fibular nerve and deep fibular nerve. Before its division, the common fibular nerve gives off several branches in the popliteal fossa. Lateral sural cutaneous nerve - supplies the skin of the upper two-thirds of the lateral side of leg.
Sural communicating nerve - it runs on the posterolateral aspect of the calf and joins the sural nerve. Superior lateral genicular nerve - accompanies artery of the same name and lies above the lateral femoral condyle. Inferior lateral genicular nerve - accompanies artery of the same name and lies just above the head of the fibula. Recurrent genicular nerve - It arises from the point of division of the common fibular nerve. There is only one motor branch that arises directly from common fibular nerve, the nerve to the short head of the biceps femoris muscle; the common fibular nerve innervates the short head of the biceps femoris muscle via a motor branch that exits close to the gluteal cleft. The remainder of the fibular-innervated muscles are innervated by its branches, the deep fibular nerve and superficial fibular nerve, it provides sensory innervation to the skin over the upper third of the lateral aspect of the leg via the lateral sural cutaneous nerve. It gives the aural communicating nerve.
Chronic fibular neuropathy can result from, among other conditions, bed rest of long duration, hyperflexion of the knee, peripheral neuropathy, pressure in obstetric stirrups, conditioning in ballet dancers. The most common cause is habitual leg crossing that compresses the common fibular nerve as it crosses around the head of the fibula. Transient trauma to the nerve can result from peroneal strike. Damage to this nerve results in foot drop, where dorsiflexion of the foot is compromised and the foot drags during walking. A common yoga kneeling exercise, the Vajrasana, has been linked to a variant called yoga foot drop. Surgical procedures involving the nerve involve: Fibular nerve decompression To surgically decompress the common fibular nerve, an incision is made over the neck of the fibula. Fascia surrounding the nerves to the lateral side of the leg is released. Deep fibular nerve decompression In the surgical treatment of deep peroneal nerve entrapment in the foot, a ligament from the extensor digitorum brevis muscle that crosses over the deep peroneal nerve, putting pressure on it and causing pain, is released.
Deep fibular nerve Peroneal strike Peroneal vein Peroneus muscles This article incorporates text in the public domain from page 964 of the 20th edition of Gray's Anatomy Anatomy photo:14:st-0501 at the SUNY Downstate Medical Center Peroneal_nerve at the Duke University Health System's Orthopedics program latleg at The Anatomy Lesson by Wesley Norman arteries-nerves%20LE/nerves4 at the Dartmouth Medical School's Department of Anatomy Overview at okstate.edu
The cerebral cortex known as the cerebral mantle, is the outer layer of neural tissue of the cerebrum of the brain, in humans and other mammals. It is separated into two cortices, by the longitudinal fissure that divides the cerebrum into the left and right cerebral hemispheres; the two hemispheres are joined beneath the cortex by the corpus callosum. The cerebral cortex is the largest site of neural integration in the central nervous system, it plays a key role in memory, perception, thought and consciousness. In most mammals, apart from small mammals that have small brains, the cerebral cortex is folded, providing a greater surface area in the confined volume of the cranium. Apart from minimising brain and cranial volume cortical folding is crucial for the wiring of the brain and its functional organisation. In mammals with a small brain there is no folding and the cortex is smooth. A fold or ridge in the cortex is termed a gyrus and a groove is termed a sulcus; these surface convolutions appear during fetal development and continue to mature after birth through the process of gyrification.
In the human brain the majority of the cerebral cortex is not visible from the outside, but buried in the sulci, the insular cortex is hidden. The major sulci and gyri mark the divisions of the cerebrum into the lobes of the brain. There are between 16 billion neurons in the cerebral cortex; these are organised into cortical columns and minicolumns of neurons that make up the layers of the cortex. Most of the cerebral cortex consists of the six-layered neocortex. Cortical areas have specific functions; the cerebral cortex is the outer covering of the surfaces of the cerebral hemispheres and is folded into peaks called gyri, grooves called sulci. In the human brain it is between two and three or four millimetres thick, makes up 40 per cent of the brain's mass. There are between 14 and 16 billion neurons in the cortex, these are organized in cortical columns, minicolumns of the layers of the cortex. About two thirds of the cortical surface is buried in the sulci and the insular cortex is hidden; the cortex is thickest over thinnest at the bottom of a sulcus.
The cerebral cortex is folded in a way that allows a large surface area of neural tissue to fit within the confines of the neurocranium. When unfolded in the human, each hemispheric cortex has a total surface area of about 1.3 square feet. The folding is inward away from the surface of the brain, is present on the medial surface of each hemisphere within the longitudinal fissure. Most mammals have a cerebral cortex, convoluted with the peaks known as gyri and the troughs or grooves known as sulci; some small mammals including some small rodents have smooth cerebral surfaces without gyrification. The larger sulci and gyri mark the divisions of the cortex of the cerebrum into the lobes of the brain. There are four main lobes: the frontal lobe, parietal lobe, temporal lobe, occipital lobe; the insular cortex is included as the insular lobe. The limbic lobe is a rim of cortex on the medial side of each hemisphere and is often included. There are three lobules of the brain described: the paracentral lobule, the superior parietal lobule, the inferior parietal lobule.
For species of mammals, larger brains tend to have thicker cortices. The smallest mammals, such as shrews, have a neocortical thickness of about 0.5 mm. There is an logarithmic relationship between brain weight and cortical thickness. Magnetic resonance imaging of the brain makes it possible to get a measure for the thickness of the human cerebral cortex and relate it to other measures; the thickness of different cortical areas varies but in general, sensory cortex is thinner than motor cortex. One study has found some positive association between the cortical intelligence. Another study has found that the somatosensory cortex is thicker in migraine sufferers, though it is not known if this is the result of migraine attacks or the cause of them. A study using a larger patient population reports no change in the cortical thickness in migraine sufferers. A genetic disorder of the cerebral cortex, whereby decreased folding in certain areas results in a microgyrus, where there are four layers instead of six, is in some instances seen to be related to dyslexia.
The six cortical layers of the neocortex each contain a characteristic distribution of different neurons and their connections with other cortical and subcortical regions. There are direct connections between different cortical areas and indirect connections via the thalamus. One of the clearest examples of cortical layering is the line of Gennari in the primary visual cortex; this is a band of whiter tissue that can be observed with the naked eye in the fundus of the calcarine sulcus of the occipital lobe. The line of Gennari is composed of axons bringing visual information from the thalamus into layer IV of the visual cortex. Staining cross-sections of the cortex to reveal the position of neuronal cell bodies and the intracortical axon tracts allowed neuroanatomists in the early 20th century to produce a detailed description of the laminar structure of the cortex in different species. After the work of Korbinian Brodmann the neurons of the cerebral cortex are grouped into six main layers, from the outer pial surface to the inner white matter.
Layer I is the molecular layer, contains few scattered neurons, including GABAergic rosehip neurons. Layer I consists of extensions of apical dendritic tufts of pyramidal neurons and horiz
Primary somatosensory cortex
The primary somatosensory cortex is located in the postcentral gyrus, is part of the somatosensory system. It was defined from surface stimulation studies of Wilder Penfield, parallel surface potential studies of Bard and Marshall. Although defined to be the same as Brodmann areas 3, 1 and 2, more recent work by Kaas has suggested that for homogeny with other sensory fields only area 3 should be referred to as "primary somatosensory cortex", as it receives the bulk of the thalamocortical projections from the sensory input fields. At the primary somatosensory cortex, tactile representation is orderly arranged from the toe to mouth. However, some body parts may be controlled by overlapping regions of cortex; each cerebral hemisphere of the primary somatosensory cortex only contains a tactile representation of the opposite side of the body. The amount of primary somatosensory cortex devoted to a body part is not proportional to the absolute size of the body surface, instead, to the relative density of cutaneous tactile receptors on that body part.
The density of cutaneous tactile receptors on a body part is indicative of the degree of sensitivity of tactile stimulation experienced at said body part. For this reason, the human lips and hands have a larger representation than other body parts. Brodmann areas 3, 1, 2 make up the primary somatosensory cortex of the human brain; because Brodmann sliced the brain somewhat obliquely, he encountered area 1 first. Brodmann area 3 is subdivided into areas 3b. Where BA 1 occupies the apex of the postcentral gyrus, the rostral border of BA 3a is in the nadir of the Central sulcus, is caudally followed by BA 3b BA 1, with BA 2 following and ending in the nadir of the postcentral sulcus. BA 3b is now conceived as the primary somatosensory cortex because 1) it receives dense inputs from the NP nucleus of the thalamus. BA 3a receives dense input from the thalamus. Areas 1 and 2 receive dense inputs from BA 3b; the projection from 3b to 1 relays texture information. Lesions confined to these areas produce predictable dysfunction in texture and shape discrimination.
Somatosensory cortex, like other neocortex, is layered. Like other sensory cortex the thalamic inputs project into layer IV, which in turn project into other layers; as in other sensory cortices, S1 neurons are grouped together with similar inputs and responses into vertical columns that extend across cortical layers. This area of cortex, as shown by Wilder Penfield and others, is organized somatotopically, having the pattern of a homunculus; that is, the legs and trunk fold over the midline. While it is not well-shown here, the lips and hands are enlarged on a proper homunculus, since a larger number of neurons in the cerebral cortex are devoted to processing information from these areas; the positions of Brodmann areas 3, 1, 2 are - from the nadir of the central sulcus toward the apex of the postcentral gyrus - 3a, 3b, 1, 2, respectively. These areas contain cells. Lesions affecting the primary somatosensory cortex produce characteristic symptoms including: agraphesthesia, astereognosia and loss of vibration and fine touch.
It can produce hemineglect, if it affects the non-dominant hemisphere. Destruction of brodmann area 3, 1, 2 results in contralateral hemihypesthesia and astereognosis, it could reduce nociception and crude touch, since information from the spinothalamic tract is interpreted by other areas of the brain, it is not as relevant as the other symptoms. List of regions in the human brain ancil-1040 at NeuroNames - area 1 ancil-1041 at NeuroNames - area 2 ancil-1042 at NeuroNames - area 3
Neuropsychology is the study and characterization of the behavioral modifications that follow a neurological trauma or condition. It is both an experimental and clinical field of psychology that aims to understand how behavior and cognition are influenced by brain functioning and is concerned with the diagnosis and treatment of behavioral and cognitive effects of neurological disorders. Whereas classical neurology focuses on the pathology of the nervous system and classical psychology is divorced from it, neuropsychology seeks to discover how the brain correlates with the mind through the study of neurological patients, it thus shares concerns with neuropsychiatry and with behavioral neurology in general. The term neuropsychology has been applied to lesion studies in animals, it has been applied in efforts to record electrical activity from individual cells in higher primates. In practice, neuropsychologists tend to work in research settings, clinical settings, or forensic settings or industry.
Neuropsychology is a new discipline within the field of psychology. The first textbook defining the field, Fundamentals of Human Neuropsychology, was published by Kolb and Whishaw in 1980. However, the history of its development can be traced back to the Third Dynasty in ancient Egypt even earlier. There is much debate as to. For many centuries, the brain was thought useless and was discarded during burial processes and autopsies; as the field of medicine developed its understanding of human anatomy and physiology, different theories were developed as to why the body functioned the way it did. Many times, bodily functions were approached from a religious point of view and abnormalities were blamed on bad spirits and the gods; the brain has not always been considered the center of the functioning body. It has taken hundreds of years to develop our understanding of the brain and how it affects our behaviors. In ancient Egypt, writings on medicine date from the time of the priest Imhotep, they took a more scientific approach to medicine and disease, describing the brain, trauma and remedies for reference for future physicians.
Despite this, Egyptians saw the heart not the brain as the seat of the soul. Aristotle reinforced this focus on the heart, he believed the heart to be in control of mental processes, looked on the brain, due to its inert nature, as a mechanism for cooling the heat generated by the heart. He drew his conclusions based on the empirical study of animals, he found that while their brains were cold to the touch and that such contact did not trigger any movements, the heart was warm and active and slowing dependent on mood. Such beliefs were upheld by many for years to come, persisting through the Middle Ages and the Renaissance period until they began to falter in the 17th Century due to further research; the influence of Aristotle in the development of neuropsychology is evident within language used in modern day, since we "follow our hearts" and "learn by the heart". Hippocrates looked upon the brain as the seat of the soul, he drew a connection between the brain and behaviors of the body saying "The brain exercises the greatest power in the man".
Apart from moving the focus from the heart as the "seat of the soul" to the brain, Hippocrates did not go into much detail about its actual functioning. However, by switching the attention of the medical community to the brain, the doors were opened to a more scientific discovery of the organ responsible for our behaviors. For years to come, scientists were inspired to explore the functions of the body and to find concrete explanations for both normal and abnormal behaviors. Scientific discovery led them to believe that there were natural and organically occurring reasons to explain various functions of the body, it could all be traced back to the brain. Over the years, science would continue to expand and the mysteries of the world would begin to make sense, or at least be looked at in a different way. Hippocrates introduced man to the concept of the mind –, seen as a separate function apart from the actual brain organ. Philosopher René Descartes expanded upon this idea and is most known by his work on the mind-body problem.
Descartes' ideas were looked upon as overly philosophical and lacking in sufficient scientific background. Descartes focused much of his anatomical experimentation on the brain, paying specific attention to the pineal gland – which he argued was the actual "seat of the soul". Still rooted in a spiritual outlook towards the scientific world, the body was said to be mortal, the soul immortal; the pineal gland was thought to be the place at which the mind would interact with the mortal and machine-like body. At the time, Descartes was convinced the mind had control over the behaviors of the body – but that the body could have influence over the mind, referred to as dualism; this idea that the mind had control over the body, but man's body could resist or influence other behaviors was a major turning point in the way many physiologists would look at the brain. The capabilities of the mind were observed to do much more than react, but to be rational and function in organized, thoughtful ways – much more complex than he thought the animal world to be.
These ideas, although disregarded by many
A brain–computer interface, sometimes called a neural-control interface, mind-machine interface, direct neural interface, or brain–machine interface, is a direct communication pathway between an enhanced or wired brain and an external device. BCI differs from neuromodulation. BCIs are directed at researching, assisting, augmenting, or repairing human cognitive or sensory-motor functions. Research on BCIs began in the 1970s at the University of California, Los Angeles under a grant from the National Science Foundation, followed by a contract from DARPA; the papers published after this research mark the first appearance of the expression brain–computer interface in scientific literature. The field of BCI research and development has since focused on neuroprosthetics applications that aim at restoring damaged hearing and movement. Thanks to the remarkable cortical plasticity of the brain, signals from implanted prostheses can, after adaptation, be handled by the brain like natural sensor or effector channels.
Following years of animal experimentation, the first neuroprosthetic devices implanted in humans appeared in the mid-1990s. The history of brain–computer interfaces starts with Hans Berger's discovery of the electrical activity of the human brain and the development of electroencephalography. In 1924 Berger was the first to record human brain activity by means of EEG. Berger was able to identify oscillatory activity, such as Berger's wave or the alpha wave, by analyzing EEG traces. Berger's first recording device was rudimentary, he inserted silver wires under the scalps of his patients. These were replaced by silver foils attached to the patient's head by rubber bandages. Berger connected these sensors to a Lippmann capillary electrometer, with disappointing results. However, more sophisticated measuring devices, such as the Siemens double-coil recording galvanometer, which displayed electric voltages as small as one ten thousandth of a volt, led to success. Berger analyzed the interrelation of alternations in his EEG wave diagrams with brain diseases.
EEGs permitted new possibilities for the research of human brain activities. Although the term had not yet been coined, one of the earliest examples of a working brain-machine interface was the piece Music for Solo Performer by the American composer Alvin Lucier; the piece makes use of EEG and analog signal processing hardware to stimulate acoustic percussion instruments. To perform the piece one must produce alpha waves and thereby "play" the various percussion instruments via loudspeakers which are placed near or directly on the instruments themselves. UCLA Professor Jacques Vidal coined the term "BCI" and produced the first peer-reviewed publications on this topic. Vidal is recognized as the inventor of BCIs in the BCI community, as reflected in numerous peer-reviewed articles reviewing and discussing the field, his 1973 paper stated the "BCI challenge": Control of objects using EEG signals. He pointed out to Contingent Negative Variation potential as a challenge for BCI control; the 1977 experiment Vidal described was the first application of BCI after his 1973 BCI challenge.
It was a noninvasive EEG control of a cursor-like graphical object on a computer screen. The demonstration was movement in a maze. After his early contributions, Vidal was not active in BCI research, nor BCI events such as conferences, for many years. In 2011, however, he gave a lecture in Graz, supported by the Future BNCI project, presenting the first BCI, which earned a standing ovation. Vidal was joined by his wife, Laryce Vidal, who worked with him at UCLA on his first BCI project. In 1988, a report was given on noninvasive EEG control of a robot; the experiment described was EEG control of multiple start-stop-restart of the robot movement, along an arbitrary trajectory defined by a line drawn on a floor. The line-following behavior was the default robot behavior, utilizing autonomous intelligence and autonomous source of energy. In 1990, a report was given on a bidirectional adaptive BCI controlling computer buzzer by an anticipatory brain potential, the Contingent Negative Variation potential.
The experiment described how an expectation state of the brain, manifested by CNV, controls in a feedback loop the S2 buzzer in the S1-S2-CNV paradigm. The obtained cognitive wave representing the expectation learning in the brain is named Electroexpectogram; the CNV brain potential was part of the BCI challenge presented by Vidal in his 1973 paper. Neuroprosthetics is an area of neuroscience concerned with neural prostheses, that is, using artificial devices to replace the function of impaired nervous systems and brain related problems, or of sensory organs; the most used neuroprosthetic device is the cochlear implant which, as of December 2010, had been implanted in 220,000 people worldwide. There are several neuroprosthetic devices that aim to restore vision, including retinal implants; the difference between BCIs and neuroprosthetics is in how the terms are used: neuroprosthetics connect the nervous system to a device, whereas BCIs connect the brain with a computer system. Practical neuroprosthetics can be linked to any part of the nervous system—for example, peripheral nerves—while the term "BCI" designates a narrower class of systems which interface with the central nervous system.
The terms are sometimes, used interchangeably. Neuroprosthetics and BCIs seek to achieve the same aims, such as restoring sight, movement, ability
Near-infrared spectroscopy is a spectroscopic method that uses the near-infrared region of the electromagnetic spectrum. Typical applications include medical and physiological diagnostics and research including blood sugar, pulse oximetry, functional neuroimaging, sports medicine, elite sports training, rehabilitation, neonatal research, brain computer interface and neurology. There are applications in other areas as well such as pharmaceutical and agrochemical quality control, atmospheric chemistry, combustion research and astronomy. Near-infrared spectroscopy is based on molecular combination vibrations; such transitions are forbidden by the selection rules of quantum mechanics. As a result, the molar absorptivity in the near-IR region is quite small. One advantage is that NIR can penetrate much further into a sample than mid infrared radiation. Near-infrared spectroscopy is, not a sensitive technique, but it can be useful in probing bulk material with little or no sample preparation; the molecular overtone and combination bands seen in the near-IR are very broad, leading to complex spectra.
Multivariate calibration techniques are employed to extract the desired chemical information. Careful development of a set of calibration samples and application of multivariate calibration techniques is essential for near-infrared analytical methods; the discovery of near-infrared energy is ascribed to William Herschel in the 19th century, but the first industrial application began in the 1950s. In the first applications, NIRS was used only as an add-on unit to other optical devices that used other wavelengths such as ultraviolet, visible, or mid-infrared spectrometers. In the 1980s, a single-unit, stand-alone NIRS system was made available, but the application of NIRS was focused more on chemical analysis. With the introduction of light-fiber optics in the mid-1980s and the monochromator-detector developments in early-1990s, NIRS became a more powerful tool for scientific research; this optical method can be used in a number of fields of science including physics, physiology, or medicine. It is only in the last few decades that NIRS began to be used as a medical tool for monitoring patients.
Instrumentation for near-IR spectroscopy is similar to instruments for the UV-visible and mid-IR ranges. There is a source, a detector, a dispersive element to allow the intensity at different wavelengths to be recorded. Fourier transform NIR instruments using an interferometer are common for wavelengths above ~1000 nm. Depending on the sample, the spectrum can be measured in either transmission. Common incandescent or quartz halogen light bulbs are most used as broadband sources of near-infrared radiation for analytical applications. Light-emitting diodes can used. For high precision spectroscopy, wavelength-scanned lasers and frequency combs have become powerful sources, albeit with sometimes longer acquisition timescales; when lasers are used, a single detector without any dispersive elements might be sufficient. The type of detector used depends on the range of wavelengths to be measured. Silicon-based CCDs are suitable for the shorter end of the NIR range, but are not sufficiently sensitive over most of the range.
InGaAs and PbS devices are more suitable though less sensitive than CCDs. It is possible to combine InGaAs detectors in the same instrument; such instruments can record both UV-visible and NIR spectra'simultaneously'. Instruments intended for chemical imaging in the NIR may use a 2D array detector with an acousto-optic tunable filter. Multiple images may be recorded sequentially at different narrow wavelength bands. Many commercial instruments for UV/vis spectroscopy are capable of recording spectra in the NIR range. In the same way, the range of some mid-IR instruments may extend into the NIR. In these instruments, the detector used for the NIR wavelengths is the same detector used for the instrument's "main" range of interest. Typical applications of NIR spectroscopy include the analysis of food products, combustion products, a major branch of astronomical spectroscopy. Near-infrared spectroscopy is in astronomy for studying the atmospheres of cool stars where molecules can form; the vibrational and rotational signatures of molecules such as titanium oxide and carbon monoxide can be seen in this wavelength range and can give a clue towards the star's spectral type.
It is used for studying molecules in other astronomical contexts, such as in molecular clouds where new stars are formed. The astronomical phenomenon known as reddening means that near-infrared wavelengths are less affected by dust in the interstellar medium, such that regions inaccessible by optical spectroscopy can be studied in the near-infrared. Since dust and gas are associated, these dusty regions are those where infrared spectroscopy is most useful; the near-infrared spectra of young stars provide important information about their ages and masses, important for understanding star formation in general. Astronomical spectrographs have been developed for the detection of exoplanets using the Doppler shift of the parent star due to the radial velocity of the planet around the star. Near-infrared spectroscopy is applied in agriculture for determining the quality of
The somatosensory system is a part of the sensory nervous system. The somatosensory system is a complex system of sensory neurons and pathways that responds to changes at the surface or inside the body; the axons of sensory neurons connect with, or respond to, various receptor cells. These sensory receptor cells are activated by different stimuli such as heat and nociception, giving a functional name to the responding sensory neuron, such as a thermoreceptor which carries information about temperature changes. Other types include mechanoreceptors and nociceptors which send signals along a sensory nerve to the spinal cord where they may be processed by other sensory neurons and relayed to the brain for further processing. Sensory receptors are found all over the body including the skin, epithelial tissues, muscles and joints, internal organs, the cardiovascular system. Somatic senses are sometimes referred to as somesthetic senses, with the understanding that somesthesis includes the sense of touch and haptic perception.
The mapping of the body surfaces in the brain is called somatotopy. In the cortex, it is referred to as the cortical homunculus; this brain-surface map is not immutable, however. Dramatic shifts can occur in response to injury; the four mechanoreceptors in the skin each respond to different stimuli for long periods. Merkel cell nerve endings are found in hair follicles. Due to having a small receptive field, they are used in areas like fingertips the most. Tactile corpuscles react to moderate light touch, they are located in the dermal papillae. They respond unlike Merkel nerve endings, they are responsible for the ability to feel gentle stimuli. Lamellar corpuscles distinguish rough and soft substances, they react in quick action potentials to vibrations around 250 Hz. They have large receptor fields. Pacinian reacts only to sudden stimuli so pressures like clothes that are always compressing their shape are ignored. Bulbous corpuscles react and respond to sustained skin stretch, they are responsible for the feeling of object slippage and play a major role in the kinesthetic sense and control of finger position and movement.
Merkel and bulbous cells - slow-response - are myelinated. All of these receptors are activated upon pressures that squish their shape causing an action potential. All afferent touch/vibration info ascends the spinal cord via the posterior column-medial lemniscus pathway via gracilis or cuneatus. Cuneatus sends signals to the cochlear nucleus indirectly via spinal grey matter, this info is used in determining if a perceived sound is just villi noise/irritation. All fibers cross in the medulla; the postcentral gyrus includes the primary somatosensory cortex collectively referred to as S1. BA3 receives the densest projections from the thalamus. BA3a is involved with the sense of relative position of neighboring body parts and amount of effort being used during movement. BA3b is responsible for distributing somato info, it projects texture info to BA1 and shape + size info to BA2. Region S2 divides into parietal ventral area. Area S2 is involved with specific touch perception and is thus integrally linked with the amygdala and hippocampus to encode and reinforce memories.
Parietal ventral area is the somatosensory relay to the premotor cortex and somatosensory memory hub, BA5. BA5 is association area. BA1 processes texture info. Area S2 processes light touch, visceral sensation, tactile attention. S1 processes the remaining info. BA7 integrates visual and proprioceptive info to locate objects in space; the insular cortex plays a role in the sense of bodily-ownership, bodily self-awareness, perception. Insula plays a role in conveying info about sensual touch, temperature and local oxygen status. Insula is a connected relay and thus is involved in numerous functions; the somatosensory system is spread through all major parts of the vertebrate body. It consists both of sensory receptors and afferent neurons in the periphery, to deeper neurons within the central nervous system. A somatosensory pathway will have three long neurons: primary and tertiary; the first neuron always has its cell body in the dorsal root ganglion of the spinal nerve. The second neuron has its cell body either in the brainstem.
This neuron's ascending axons will cross to the opposite side either in the spinal cord or in the brainstem. In the case of touch and certain types of pain, the third neuron has its cell body in the VPN of the thalamus and ends in the postcentral gyrus of the parietal lobe. Photoreceptors, similar to those found in the retina of the eye, detect damaging ultraviolet radiation (