A finger is a limb of the human body and a type of digit, an organ of manipulation and sensation found in the hands of humans and other primates. Normally humans have five digits, the bones of which are termed phalanges, on each hand, although some people have more or fewer than five due to congenital disorders such as polydactyly or oligodactyly, or accidental or medical amputations. The first digit is the thumb, followed by index finger, middle finger, ring finger, and little finger or pinkie. According to different definitions, the thumb can be called a finger, or not.
The trigeminal nerve (the fifth cranial nerve, or simply CN V) is a nerve responsible for sensation in the face and motor functions such as biting and chewing; it is the most complex of the cranial nerves. Its name ("trigeminal" = tri-, or three, and - geminus, or twin: thrice-twinned) derives from the fact that each of the two nerves (one on each side of the pons) has three major branches: the ophthalmic nerve (V1), the maxillary nerve (V2), and the mandibular nerve (V3). The ophthalmic and maxillary nerves are purely sensory, whereas the mandibular nerve supplies motor as well as sensory (or "cutaneous") functions. Adding to the complexity of this nerve is the fact that autonomic nerve fibers as well as special sensory fibers (taste) are contained within it.
A Brodmann area is a region of the cerebral cortex, in the human or other primate brain, defined by its cytoarchitecture, or histological structure and organization of cells.
The parietal lobe is one of the four major lobes of the cerebral cortex in the brain of mammals. The parietal lobe is positioned above the temporal lobe and behind the frontal lobe and central sulcus.
The precuneus is the portion of the superior parietal lobule on the medial surface of each brain hemisphere. It is located in front of the cuneus. The precuneus is bounded in front by the marginal branch of the cingulate sulcus, at the rear by the parietooccipital sulcus, and underneath by the subparietal sulcus. It is involved with episodic memory, visuospatial processing, reflections upon self, and aspects of consciousness.
Cortical maps are collections (areas) of minicolumns in the brain cortex that have been identified as performing a specific information processing function.
The postcentral gyrus is a prominent gyrus in the lateral parietal lobe of the human brain. It is the location of the primary somatosensory cortex, the main sensory receptive area for the sense of touch. Like other sensory areas, there is a map of sensory space in this location, called the sensory homunculus.
The primary somatosensory cortex is located in the postcentral gyrus, and is part of the somatosensory system. It was initially defined from surface stimulation studies of Wilder Penfield, and parallel surface potential studies of Bard, Woolsey, and Marshall. Although initially defined to be roughly 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.
The motor cortex is the region of the cerebral cortex involved in the planning, control, and execution of voluntary movements. Classically, the motor cortex is an area of the frontal lobe located in the posterior precentral gyrus immediately anterior to the central sulcus.
The lobes of the brain were originally a purely anatomical classification, but have been shown also to be related to different brain functions. The cerebrum, the largest portion of the human brain, is divided into lobes, but so is the cerebellum. If not specified, the expression "lobes of the brain" refers to the cerebrum.
Brodmann area 43, the subcentral area, is a structurally distinct area of the cerebral cortex defined on the basis of cytoarchitecture. Along with Brodmann Area 1, 2, and 3, Brodmann area 43 is a subdivision of the postcentral region of the brain, suggesting a somatosensory function. The histological structure of Area 43 was initially described by Korbinian Brodmann, but it was not labeled on his map of cortical areas.
A cortical homunculus is a distorted representation of the human body, based on a neurological "map" of the areas and proportions of the human brain dedicated to processing motor functions, or sensory functions, for different parts of the body. The word homunculus is Latin for "little man", and was a term used in alchemy and folklore long before scientific literature began using it. A cortical homunculus, or "cortex man", illustrates the concept of a representation of the body lying within the brain. Nerve fibres—conducting somatosensory information from all over the body—terminate in various areas of the parietal lobe in the cerebral cortex, forming a representational map of the body.
A topographic map is the ordered projection of a sensory surface, like the retina or the skin, or an effector system, like the musculature, to one or more structures of the central nervous system. Topographic maps can be found in all sensory systems and in many motor systems.
The colour centre is a region in the brain primarily responsible for visual perception and cortical processing of colour signals received by the eye, which ultimately results in colour vision. The colour centre in humans is thought to be located in the ventral occipital lobe as part of the visual system, in addition to other areas responsible for recognizing and processing specific visual stimuli, such as faces, words, and objects. Many functional magnetic resonance imaging (fMRI) studies in both humans and macaque monkeys have shown colour stimuli to activate multiple areas in the brain, including the fusiform gyrus and the lingual gyrus. These areas, as well as others identified as having a role in colour vision processing, are collectively labelled visual area 4 (V4). The exact mechanisms, location, and function of V4 are still being investigated.
A digit is one of several most distal parts of a limb, such as fingers or toes, present in many vertebrates.
The somatosensory system is a part of the sensory nervous system. The somatosensory system is a complex system of sensory neurons and neural 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, chemoreceptors, and nociceptors which send signals along a sensory nerve to the spinal cord where they may be processed by other sensory neurons and then relayed to the brain for further processing. Sensory receptors are found all over the body including the skin, epithelial tissues, muscles, bones and joints, internal organs, and the cardiovascular system.
The primary motor cortex is a brain region that in humans is located in the dorsal portion of the frontal lobe. It is the primary region of the motor system and works in association with other motor areas including premotor cortex, the supplementary motor area, posterior parietal cortex, and several subcortical brain regions, to plan and execute movements. Primary motor cortex is defined anatomically as the region of cortex that contains large neurons known as Betz cells. Betz cells, along with other cortical neurons, send long axons down the spinal cord to synapse onto the interneuron circuitry of the spinal cord and also directly onto the alpha motor neurons in the spinal cord which connect to the muscles.
Michael Steven Anthony Graziano is an American scientist and novelist who is currently a professor of Psychology and Neuroscience at Princeton University. His scientific research focuses on the brain basis of awareness. He has proposed the "attention schema" theory, an explanation of how, and for what adaptive advantage, brains attribute the property of awareness to themselves. His previous work focused on how the cerebral cortex monitors the space around the body and controls movement within that space. Notably he has suggested that the classical map of the body in motor cortex, the homunculus, is not correct and is better described as a map of complex actions that make up the behavioral repertoire. His publications on this topic have had a widespread impact among neuroscientists but have also generated controversy. His novels rely partly on his background in psychology and are known for surrealism or magic realism. Graziano also composes music including symphonies and string quartets. He is an avid practitioner of ventriloquism and uses a puppet orangutan "Kevin" as sidekick.
Neurocomputational speech processing is computer-simulation of speech production and speech perception by referring to the natural neuronal processes of speech production and speech perception, as they occur in the human nervous system. This topic is based on neuroscience and computational neuroscience.
Cortical remapping, also referred to as cortical reorganization, is the process by which an existing cortical map is affected by a stimulus resulting in the creating of a 'new' cortical map. Every part of the body is connected to a corresponding area in the brain which creates a cortical map. When something happens to disrupt the cortical maps such as an amputation or a change in neuronal characteristics, the map is no longer relevant. The part of the brain that is in charge of the amputated limb or neuronal change will be dominated by adjacent cortical regions that are still receiving input, thus creating a remapped area. Remapping can occur in the sensory or motor system. The mechanism for each system may be quite different. Cortical remapping in the somatosensory system happens when there has been a decrease in sensory input to the brain due to deafferentation or amputation, as well as a sensory input increase to an area of the brain. Motor system remapping receives more limited feedback that can be difficult to interpret.
