G. Dennis Rains,
Kutztown University of Pennsylvania
| (fiber) tract | A large number of axons bundled together and conveying information from one region of the central nervous system to another.
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| afferent | "Toward." Neural input. Thalamic afferents are neurons projecting to the thalamus.
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| agnosia | Impairment in recognition not due to primary sensory impairment. Agnosias are modality specific.
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| allocortex | Areas of cortex with fewer than six layers.
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| amygdala | Collection of nuclei in the base of the temporal lobe, anterior to the hippocampus. Considered part of the limbic system.
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| anterior | Term designating the front part of the brain and spinal cord.
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| anterior commissure | An important fiber tract connecting the two temporal lobes.
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| anterior pituitary gland | A gland protruding from the base of the hypothalamus that has a major role in the control of endocrine function.
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| anterograde amnesia | An impairment in the ability to remember new events following some compromise of brain function.
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| arachnoid membrane | The middle membrane surrounding the brain (positioned between the dura mater and the pia mater). It consists of two layers of fibrous and elastic tissue. It does not follow the contours of the sulci and gyri of the cortex.
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| archicortex | Areas of cortex that have only one layer. It includes regions of the hippocampus (Ammon's horn and the dentate gyrus).
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| arcuate fasciculus | Fiber tract connecting Wernicke's and Broca's areas.
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| association cortex | According to older, sequential models of cortical processing, the areas of cortex (not devoted to sensory or motor function) where higher-order (associative) processes are represented. Because of our growing understanding of the function of these areas, this term is now seen as insufficiently specific and its use is becoming increasingly infrequent.
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| auditory association cortex (AII) | Area surrounding the auditory cortex that receives projections from the auditory cortex and is involved in higher-order auditory processing.
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| auditory cortex | Area of cortex in Heschl's gyrus in the lower lip of the sylvian fissure that receives the major projections from the medial geniculate nucleus of the thalamus.
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| auditory nerve | The nerve fibers connecting the structures of the inner ear to the cochlear nucleus in the brain stem.
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| auditory radiations | Fibers conveying auditory input from the medial geniculate nucleus to the auditory cortex.
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| autonomic nervous system (ANS) | The part of the peripheral nervous system that innervates internal organs, blood vessels, and glands and that is not under voluntary control.
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| basal ganglia | A large group of gray matter structures deep within the forebrain including the caudate nucleus, putamen, globus pallidus, subthalamic nuclei, and substantia nigra. (The substantia nigra is actually in the midbrain.) This term is an exception to the general rule that collections of neuron cell bodies within the cen-tral nervous system are called nuclei, whereas those in the peripheral nervous system are called ganglia.
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| bilateral | On both sides (of the body).
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| blindsight | The ability of patients with cortical blindness to have some preserved but unconscious visual function.
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| brain stem | The part of the brain lying between the diencephalon and the spinal cord. It is composed of the midbrain, pons, and medulla.
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| cauda equina | "Horse tail." The array of lower spinal nerves as they continue to course caudally beyond the end of the spinal cord before leaving the spinal column.
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| caudal | In the brain stem and spinal cord, the direction away from the brain.
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| caudate nucleus | One of the nuclei of the basal ganglia.
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| central nervous system (CNS) | The brain and the spinal cord.
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| cerebellar ataxia | Disruptions in the mainte-nance of posture and the sequential coordina-tion of movement associated with cerebellar dysfunction.
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| cerebellar peduncles | Massive fiber tracts connecting the cerebellum and forebrain.
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| cerebellum (metencephalon) | The large and intricate structure bulging out of the dorsal surface of the brain at the level of the pons and forming the roof of the fourth ventricle.
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| cerebral cortex | The massive sheet of neuron cell bodies that forms the outer layer of gray matter surrounding the telencephalon.
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| cerebral cortex | The massive sheet of neuron cell bodies that forms the outer layer of gray matter surrounding the telencephalon.
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| cerebral cortex | The massive sheet of neuron cell bodies that forms the outer layer of gray matter surrounding the telencephalon.
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| cerebral ventricles | See ventricles.
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| cerebrospinal fluid (CSF) | Fluid that fills the cerebral ventricles and the subarachnoid space. CSF surrounds the brain, providing structural support for it and a measure of protection to it from blows to the head.
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| choroid plexus | Tufts of capillary vessels in the cerebral ventricles through which CSF enters the ventricle.
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| cochlear nucleus | The brain-stem nucleus to which the auditory nerve projects.
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| contralateral | On the opposite side.
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| corpus callosum | The massive fiber tract that forms neural connections between the two cerebral hemispheres.
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| corpus striatum | A collective name for the putamen, globus pallidus, and caudate nucleus.
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| cortical blindness | Blindness due to damage to the cortical visual system, particularly the primary visual cortex (V1).
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| cortical deafness | Deafness due to cortical damage.
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| corticobulbar tract | A bundle of fibers carrying information from the forebrain to the brain stem.
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| corticocortical connections | Interconnections between cortical areas.
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| corticospinal tract | A large bundle of fibers carrying information from the forebrain to the spinal cord.
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| cytoarchitectonics | The study of variations in the characteristics (e.g., thickness, neuron type) of cell layers in different parts of the cerebral cortex.
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| decussation | The crossing-over of fibers from one side of the brain to the other.
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| diencephalon | The part of the forebrain between the telencephalon and the midbrain, including the thalamus, hypothalamus, and epithalamus.
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| dorsal horn | The dorsal part of the spinal gray matter containing the cell bodies of interneurons that convey input from primary somatosensory neurons to the brain and to motor neurons at the same and other levels of the spinal cord.
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| dorsal root | Fiber bundles containing the axons of primary sensory neurons as they enter each segment of the dorsal (posterior) spinal cord.
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| dorsal root ganglion | The concentration of cell bodies of primary sensory neurons forming a protuberance in the spinal nerve near the point where the dorsal root enters the spinal cord.
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| dura mater | The outermost membrane surrounding the brain. It is tough, inelastic, and follows the contour of the skull.
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| efferent | "Away from." Neural output. Thalamic efferents are neurons projecting out of the thalamus.
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| extrastriate cortex | Areas of cortex outside V1 that are involved in vision. Also called prestriate cortex.
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| forebrain (prosencephalon) | The most rostral part of the brain, including the telencephalon (cerebral hemispheres, basal ganglia, amygdala, and hippocampus) and the diencephalon (thalamus and hypothalamus). Also termed the prosencephalon.
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| frontal lobes | Area of cortex and underlying white matter in the front part of the forebrain, anterior to the central sulcus.
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| functional mapping | The mapping of particular parts of a neural structure to particular behaviors or experiences, using the results of electrical stimulation of the brain, the effects of lesions, or other methods. The homunculi of the motor and sensory cortices are examples.
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| ganglion (pl., ganglia) | A concentration of neuron cell bodies outside the central nervous system.
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| globus pallidus | One of the nuclei in the basal ganglia.
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| gray matter | Brain tissue composed of neuron cell bodies.
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| gyrus (pl., gyri) | An outfolding on the cerebral cortex.
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| hemianopia | Blindness in one (left or right) visual field.
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| hemiplegia | Paralysis on one side of the body.
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| Heschl's gyrus | Gyrus on the lower lip of the sylvian fissure that is roughly equivalent to the primary auditory cortex.
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| hindbrain (rhombencephalon) | The part of the brain stem caudal to the midbrain. It includes the metencephalon (pons and cerebellum) and the myelencephalon (the medulla oblongata).
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| hippocampus | Cortical structure lying in the anterior and medial part of the temporal lobe.
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| homeostasis | The internal biological steady state that every organism must constantly maintain to stay alive.
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| homotopic fields | Corresponding areas in the right and left hemispheres.
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| hydrocephalus | A condition characterized by abnormal accumulation of cerebrospinal fluid in one or more cerebral ventricles, resulting in increased intracranial pressure and destruction of brain tissue.
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| hypothalamus | Collection of nuclei lying below the thalamus and involved in a wide range of functions, particularly autonomic functions. It is considered part of the limbic system.
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| inferior | Term designating the lower part of the brain. Also designates "below," relative to a reference point.
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| inferior colliculus | Area in the midbrain that receives auditory projections from the superior olive.
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| ipsilateral | On the same side.
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| ipsilateral corticocortical fibers | Fibers connecting areas within the same hemisphere.
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| isocortex | See neocortex.
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| kinesthesis | Sense of body movement.
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| lateral | Term designating that, relative to another structure, a given structure is closer to the side of the brain.
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| lateral geniculate nucleus (LGN) | Nucleus of the thalamus, to which information from the retina projects.
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| lemniscal system | A pathway in the spinal cord that conveys information about touch, proprioception, and body movement to the thalamus.
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| limbic system | A term that is widely used to denote a number of structures that have been hypothesized to be centrally involved in the neural mediation of emotion.
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| mamillary bodies | Nuclei in the posterior part of the hypothalamus. Their name comes from their breastlike appearance when viewed on the ventral surface of the brain.
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| medial | Term designating that, relative to another structure, a given structure is closer to the midline of the brain.
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| medial geniculate nucleus | Area of the thalamus that receives auditory input from the inferior colliculus and projects to the auditory cortex.
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| medulla oblongata (myelencephalon) | Portion of the hindbrain rostral to the spinal cord and caudal to the pons.
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| meninges | The collective name for the three membranes that surround the brain. From outside in, these are the dura mater, arachnoid membrane, and pia mater.
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| midbrain (mesencephalon) | The short segment of the brain stem between the forebrain and the hindbrain. It includes the tectum and the tegmentum. Also termed the mesencephalon.
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| motor cortex (M1) | The area of cortex (just anterior to the central sulcus) that is most directly involved in the implementation of movement. Also called M1.
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| motor homunculus | The representation of the body on the precentral gyrus (motor cortex) as revealed by electrical stimulation.
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| motor strip | See motor cortex.
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| neocortex | Six-layer cortex that is thought to have evolved relatively late in evolution. Also called isocortex.
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| neostriatum | The caudate nucleus and the putamen.
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| nucleus (nuclei) | (1) A concentration of neuron cell bodies within the central nervous system. (2) A spheroid body within a cell containing a number of organelles and the cell's complement of DNA.
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| occipital lobes | The areas of cortex and underlying white matter lying beneath the back part of the skull.
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| occulomotor nucleus | One of the cranial nerve nuclei in the midbrain that participates in the control of eye movement. It also mediates the pupillary reflex.
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| paleocortex | Areas of cortex with only two cell layers. This includes olfactory cortex and the parahippocampal gyrus.
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| parahippocampal gyrus | A gyrus near the hippocampus in the ventral and medial part of the temporal lobe.
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| parietal lobes | The area of cortex and underlying white matter lying beneath the parietal bones, at the posterior, superior part of the skull.
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| peripheral nervous system (PNS) | Parts of the nervous system other than the brain stem and spinal cord. This includes the sensory and motor nerves, which are distributed throughout the body and which convey information to and from the brain and spinal cord (peripheral nerves).
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| pia mater | The innermost membrane surrounding the brain. It follows the contours of the gyri and sulci.
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| plexiform layer | The outermost layer of the cerebral cortex, consisting of fibers (axons) connecting different areas of cortex.
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| pons | Rostral portion of the hindbrain, between the midbrain and the medulla oblongata.
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| posterior | Term designating the back part of the brain and spinal cord.
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| posterior commissure | A fiber tract connecting posterior areas of the two hemispheres.
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| prefrontal cortex | The area of the frontal lobes anterior to the premotor and supplementary motor cortices. It is involved in the higher-order control and regulation of behavior.
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| premotor area (PMA) | The area of cortex just anterior to the motor cortex on the anterior surface of each cerebral hemisphere. It is involved in the coordination of sequences of movement.
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| prestriate cortex | Areas of cortex outside V1 that are involved in vision. Also called extrastriate cortex.
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| primary visual cortex (V1) | Area in the occipital lobes that receives the primary projection from the lateral geniculate nucleus of the thalamus. Also called V1.
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| primary visual pathway | The pathway from retina to lateral geniculate nucleus to V1.
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| proprioception | Body position sense.
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| putamen | One of the nuclei that make up the basal ganglia.
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| pyramidal decussation | The area of the medulla at which corticospinal fibers cross over from one side of the brain stem to the other.
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| rostral | In the brain stem and the spinal cord, the direction toward the brain.
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| secondary motor area | According to the sequential hierarchical model, the area of cortex to which tertiary motor cortex projects (i.e., the premotor cortex).
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| secondary sensory areas | According to the sequential hierarchical model, areas of cortex that, receive projections from primary sensory cortex for a given modality.
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| secondary somatosensory cortex (SII) | The area of cortex ventral to the somatosensory cortex that receives input mainly from that structure and projects to posterior parietal areas where higher-order somatosensory and spatial processing takes place.
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| sensory homunculus | The orderly mapping of the body surface on the somatosensory cortex (S1) in the postcentral gyrus.
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| septum (septal nuclei) | Nuclei that lie ventral and medial to the lateral ventricles in the basal forebrain. They are considered part of the limbic system.
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| somatic motor system | Skeletal muscle and the parts of the nervous system that control it.
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| somatic nervous system | The part of the peripheral nervous system innervating skin, joints, and skeletal muscles.
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| somatosensory cortex (S1) | The area of cortex in the postcentral gyrus of each hemisphere that receives and processes sensory information from the contralateral side of the body about touch, temperature, vibration, proprioception, and kinesthesis.
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| somatosensory system | The system that processes information about the body, including touch, temperature, pain, body position, and body movement.
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| special sensory | Term sometimes used to refer to the major sensory modalities other than somesthesis (i.e., vision, audition, smell, and taste).
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| spinal cord | The part of the central nervous system extending from the medulla rostrally, to the cauda equina caudally. Its exterior portion is white matter, composed of fiber tracts that carry information to and from the brain. Its central portion is gray matter.
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| spinothalamic system | A multisynaptic pathway in the spinal cord that conveys information about pain and temperature to the thalamus.
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| striate cortex | Another name for V1 in the calcarine sulcus of the occipital lobes.
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| subarachnoid space | The space between the two layers of the arachnoid membrane.
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| subcallosal gyrus | The area of cortex on the medial aspect of the cerebral hemispheres lying inferior to the anterior part of the corpus callosum.
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| substantia nigra | A midbrain nucleus that is a major source of dopamine for the cortex. It is generally considered to be part of the basal ganglia.
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| subthalamic nuclei | Small nuclei that lie ventral to the thalamus. They are generally considered to be part of the basal ganglia.
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| sulcus (pl., sulci) | Furrows or grooves in the folded surface of the cerebral cortex.
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| superior | Term designating the upper part of the brain; also designates "above," relative to a reference point.
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| superior olive | Brain-stem nucleus that receives auditory projections from the cochlear nucleus.
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| supplementary motor area (SMA) | The area on the medial surface of each hemisphere just anterior to the motor cortex. It is involved in the coordination of sequences of movement.
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| tectum | The part of the midbrain dorsal (posterior) to the cerebral aqueduct. It includes the superior and inferior colliculi.
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| tegmentum | The part of the midbrain that lies ventral to the cerebral aqueduct.
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| telencephalon | The most rostral part of the forebrain, including the cerebral hemispheres, basal ganglia, the amygdala, and the hippocampus, but not including the diencephalon.
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| temporal lobes | Areas of cortex and underlying white matter lying beneath the temporal bone, at the sides of the skull.
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| tertiary motor area | According to the sequential hierarchical model, the area in the frontal lobes to which information from the tertiary sensory area projects.
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| tertiary sensory area | According to the sequential hierarchical model, the area of cortex in which information from each of the secondary sen-sory areas (visual, auditory, and somatosensory) converges.
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| tonotopic maps | Orderly representations of sound frequency in the auditory cortex.
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| transduction | The changing of a specific form of energy into a pattern of neural impulses. It is seen in vision, audition, and somesthesis.
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| trochlear nucleus | One of the cranial nerve nuclei in the midbrain that participates in the control of eye movement.
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| uncinate fasciculus | The fiber tract connecting the temporal and frontal cortex.
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| unilateral | On one side (of the body).
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| ventral horn | The ventral region of the gray matter within the spinal cord containing the cell bodies of α motor neurons.
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| ventral root | The fiber bundles emerging from the ventral aspect of the spinal cord and containing axons of α motor neurons.
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| visual association cortex | Areas of cortex outside V1 that are involved in vision. These areas are now more frequently referred to a extrastriate cortex or prestriate cortex.
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| white matter | Brain tissue composed of the axons of neurons.
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2002 McGraw-Hill Higher Education