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Glossary of Neuroscience Terms F-L

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F

Facial Nerve (Cranial Nerve VII):
innervates the lip muscles including the obicularis oris and the zygomaticus. The muscles must contract during the oral preparatory and oral transport stages of the swallow to prevent food from dribbling out of the mouth. The facial also innervates the buccinator muscles of the cheeks. These must remain tense during the oral component of the swallowing process to prevent the pocketing of food between the teeth and the cheeks.

Sensory Component carries information about taste from the anterior 2/3 of the tongue.
 
falx cerebelli:
separates the lobes of the cerebellum; the falx cerebelli is formed by the dura mater
 
falx cerebri:
separates the lobes of the cerebrum; the falx cerebri is formed by the dura mater
 
festinating movements:
movements which become increasingly rapid and uncontrolled
 
final common pathway:
lower motor neurons traveling to the muscles of the body on the only route by which information from any of the upper motor tracts can reach the periphery. Thus, when lower motor neurons are damaged, the parts of the body that they innervate are deprived of input from the pyramidal and extrapyramidal tract as well as cerebellar pathways. Thus, voluntary, automatic and reflexive movements are all affected.
 
finger agnosia:
an inability to recognize objects through the sense of touch; may be the result of damage to the angular gyrus in the hemisphere dominant for speech and language
 
fissure:
a particularly deep sulcus
 
fissure of Rolando (central sulcus):
the sulcus that separates the frontal and parietal lobes
 
fissure of Sylvius (lateral fissure):
the fissure that separates the frontal and temporal lobes
 
flaccid (lower motor neuron) dysarthria:
the only form of dysarthria that results from damage to lower motor neurons.
 
Fluent Aphasias:
Fluent aphasias are the result of lesions affecting the post Rolandic area. Problems with meaning are associated with posterior lesions.
Phoneme selection and sequencing as well as syntax are preserved. Speech is characterized by a facility of articulation and many long runs of words combined using a variety of grammatical constructions. However, fluent speech is not equivalent to meaningful speech. Often the speech of fluent aphasics sounds like "jabberwocky." Typically, there are word-finding problems that affect nouns and picturable action words. Comprehension is typically poor with fluent/posterior lesion aphasias. (Conduction aphasia would be the exception to this). The amount and type of paraphasias, the presence of auditory receptive impairments and of impaired repetition are variable in fluent aphasias, depending upon the exact site of lesion.
 
flocculi:
the most ancient part of the cerebellum; the flocculi are part of flocculonodular lobe
 
flocculonodular lobe:
the lobe of the cerebellum that consists of the flocculi and the nodulus; the flocculonodular lobe is involved in the maintenance of equilibrium
 
focal lesions:
generally small and just in one area, focal lesions can affect the language and swallowing centers of the brain, they can cause symptoms similar to those seen as a result of a left cerebral vascular accident including apraxia, dysarthria, aphasia, dysphagia, agnosia, anomia, and dysphonia. Focal lesions can also cause more general impairments that affect language, similar to those resulting from right hemisphere damage. These include attentional, perceptual and pragmatic deficits.
 
foramina of Luschka:
two lateral openings (along with the medial foramen of Magendie) which serve to connect the fourth ventricle to the subarachnoid space
 
foramen of Magendie:
a medial opening (along with the lateral foramina of Luschka) which serves to connect the fourth ventricle to the subarachnoid space
 
foramina of Munro (interventricular foramina):
two openings which connect the lateral ventricles to the third ventricle
 
fornix:
a subcortical component of the limbic system; the fornix is a group of fibers that arise from the hippocampus and connect the rhinencephalon to the thalamus and hypothalamus; the fornix is connected to the septal nuclei and the mamillary bodies
 
fourth ventricle:
one of the four ventricles of the brain; it is filled with cerebrospinal fluid; the fourth ventricle is located between the cerebellum and the pons
 
frontal lobe:
the most anterior lobe of the brain; it is bounded posteriorly by the central sulcus and inferiorly by the lateral fissure; this lobe is associated with higher cognitive functions and is involved in the control of voluntary muscle movement
 
fusiform layer (multiform layer):
the sixth and most inferior layer of the cortex  

G

GABA:
Gamma Amino Butric Acid; a neurotransmitter that is involved in the inhibitory function of the basal ganglia; it is a glutamate
 
gag reflex:
a good example of a true reflex. It is "triggered" whenever a noxious substance touches the back of the tongue, back of the pharynx, or soft palate. The swallow response, on the other hand, cannot be initiated by touching any particular area in the oral cavity. The gag reflex and the swallow response also differ in terms of neurological control. The gag reflex is completely controlled by the brain stem. The swallow, on the other hand, is only partially controlled by the brain stem. It also receives cortical input, and input from muscle spindles, including feedback from tongue movements.

(It is important to note that the gag reflex and the swallow response are not related. In the past, many physicians would determine feeding status based on the presence or absence of a patient's gag. Actually, the presence or absence of a gag reflex does not predict the status of the swallow response.)
 
gamma neurons:
neurons of the final common pathway (located on the ventral aspect of the spinal cord); these cells conduct slow motor impulses and their main function is to stretch muscle spindles; gamma cells are only half as numerous as alpha cells
 
ganglionic cells:
neurons of the autonomic system that originate within the ganglia of the autonomic nervous system and project to post-ganglionic neurons
 
ganglionic layer:
the fifth layer of the cortex; it contains small granular cells, large pyramidal cells, and the cell bodies of some association fibers (the association fibers that originate here form the Bands of Baillerger and Kaes Bechterew, which are two large fiber tracts)
 
Glasgow Coma Scale:
developed by Jennett and Teasdale (1989), instrument most frequently used to quantify levels of consciousness, consists of three categories: eye opening, verbal responses and motor responses.
 
Global Aphasia:
third most common aphasic syndrome after Broca's and Wernicke's, occurs when there are both anterior and posterior lesions. All aspects of language are so severely impaired that there is no longer a distinctive pattern of preserved vs. impaired components. Articulation may be adequate in the context of stereotypical utterances. Prognosis is poor.
 
globus pallidus:
the more medial part of the lenticular nucleus
 
Glossopharyngeal Nerve (Craninial Nerve IX):
considered the major nerve for the swallowing center, Motor Component innervates the 3 salivary glands in the mouth. The saliva from these glands mixes with the chewed up food to form a bolus. Has motor, sensory, and autonomic nervous system nerve fibers. It, along with the vagus (CN. X), provides some innervation to the upper pharyngeal constrictor muscles (Zemlin, 1997). Innervates the stylopharyngeus muscle which elevates the larynx and pulls it forward during the pharyngeal stage of the swallow. This action also aids in the relaxation and opening of the cricopharyngeus muscle. Sensory components mediate all sensation, including taste, from the posterior 1/3 of the tongue. Also carries sensation from the velum and the superior portion of the pharynx. A lesion may impair the gag reflex unilaterally (Zemlin, 1997).
 
graduated stick:
may be used instead of a pacing board. Graduated sticks have bumps on them at regular intervals and the patient must touch one bump for every syllable. Metronomes can also be used to slow speech rate. Patients are taught to produce one syllable per "tick" on the metronome.
 
gyrus:
a raised fold of brain tissue  

H

hemianopsia:
loss of sight in one half of the visual field. damage to either middle cerebral artery can cause This blindness affects the contralateral aspect of both visual fields. For example, a blockage in the right middle cerebral artery will cause left hemianopsia or blindness in the left visual field of both eyes.
 
hyposthesia:
lack or sensation
 
hemiplegia:
complete paralysis on one side
 
hemiparesis:
partial paralysis on one side
 
hematomas:
or pools of congealed blood, in the parenchyma, the subarachnoid space, or the subdural space, bleeding due to stroke, hemmorrhage or traumatic brain injury, tissue is irritated rather than infarcted
 
Hemophilia:
is a thinning of the blood which prevents it from coagulating.
 
hemorrhagic strokes
Hemorrhagic stroke occurs when a cerebral artery ruptures, causing bleeding within the cranium. Such ruptures may be caused by aneurysms,   weak spots in arterial walls. (Aneurysms can balloon out rather than bursting. The excess pressure resulting from this swelling can also damage brain tissue.) 
 
Heschl's Gyrus (anterior transverse temporal gyrus):
the primary auditory area; it is located in the temporal lobe
 
hippocampus:
a cortical area classified as part of the limbic system; it is a gyrus located on the medial edge of the temporal lobe, it is involved with memory
 
homunculus:
"little man"; a pedagogical device that is used to explain and demonstrate the functioning of the motor strip
 
horizontal cut (transverse cut):
a cut that divides the brain into upper and lower sections; perpendicular to coronal, medial, and sagittal cuts
 
hydrocephalus:
a condition that occurs when too much cerebrospinal fluid is produced and the ventricles swell, resulting in pressure being exerted on the tissue of the brain; it may be caused by tumors
 
hydroencephali:
a rare birth defect in which the cerebrum is absent and the space where it should be is filled with cerebrospinal fluid; the term literally means "water brain"
 
hyperkinetic dysarthria:
occur when the extrapyramidal tract is damaged, specifically the basal ganglia
 
hypertension:
blood pressure that is elevated regardless of activity level; may be a factor in stroke
 
Hypokinesia :
"the reduced amplitude of muscle movement" (Love & Webb, 1992, p. 146).
 
Hypoglossal Nerve (Cranial Nerve XII)
Information about motor movement is received from the muscle spindles in the tongue via this nerve, serves as part of the swallowing center that initiates the swallow. The hypoglossal innervates all extrinsic and intrinsic tongue muscles. (It is strictly a motor nerve.)
 
hypopharynx (of the Pharynx):
lower portion of the pharynx. It is also known as the laryngopharynx
 
hypothalamus:
a subcortical structure located immediately below the thalamus, part of it is also anterior to the thalamus and it forms the floor and part of the lateral walls of the third ventricle; by controlling the functioning of the pituitary gland it regulates basic biological functions (e.g., appetite, body temperature, sex drive)
 
hypokinetic dysarthria:
occur when the extrapyramidal tract is damaged, specifically the substantia nigra
 
Hyperuricemia:
a risk factor for CVA, involves an elevation of the level of uric acid in the blood. (This is the cause of gout.)

I

infarction:
death of tissue
 
inferior:
refers to the lower parts of the nervous system
 
inferior cerebellar peduncles (restiform bodies):
one of the three fiber bundles called cerebellar peduncles that connect the cerebellum to the brain stem; the inferior cerebellar peduncle connects the cerebellum with the vestibular nuclei located in the lower pons and medulla, and with the reticular formation; proprioceptive information from the upper body (information that travels along the dorsospinocerebellar tract) enters the cerebellum on the inferior cerebellar peduncle
 
inferior colliculi:
structures of the midbrain that relay auditory information to the medial geniculate bodies of the thalamus
 
insula (the Island of Reil):
the cortical area that lies below the fissure of Sylvius; it is considered by some anatomists as the fifth lobe of the brain; it may be associated with the viscera
 
interconnecting fibers:
nerve fibers that connect structures within the brain; the two types of interconnecting fibers are commisural fibers and association fibers
 
internal capsule:
a group of myelinated ascending and descending fiber tracts that connect the cortex to other parts of the central nervous system; although the axons that pass through it descend to the brain stem and spinal cord, the capsule itself ends within the cerebrum; the internal capsule is located between the lenticular nucleus and the caudate nucleus
 
internal carotid artery:
a division of the common carotid; the internal carotid arteries supply blood to the brain; the two main branches of this artery are the anterior cerebral artery and the middle cerebral artery,  The internal carotids and basilar arteries are connected via the Circle of Willis, which allows blood to pass from one system to another in the event of blockage.
 
internal granular layer:
the fourth layer of the cortex; it is very thin; it contains pyramidal cells in row formation
 
interneurons:
association neurons of the spinal cord; interneurons connect the anterior and posterior horns of grey matter and are involved in the reflex arc (they function within the same segment of the spinal cord)
 
internuncial neurons:
association neurons of the spinal cord; internuncial neurons project (ascend) to the brain stem and cerebellum
 
intraparnchymal bleeding:
can occur at a very slow rate within structure such as the thalamus, the spontaneous recovery period following a stroke caused by this type of bleeding may be especially lengthy. For this reason, it is justifiable to continue therapy for a longer period of time with patients who have had parenchymal bleeding than with those who have had other types of hemorrhages.
 
intraparynchemal hemorrhaging:
Due to Penetrating Brain Injury Bleeding within the structures of the brain is usually the consequence of penetrating head wounds rather than CHI. This kind of hemorrhaging can occur in the cortex as well as in subcortical areas. When it is the result of closed head injury, rather than CVA, it most commonly affects the frontal and temporal lobes. Most penetrating brain injuries result from high velocity missiles such as bullets. Low velocity focal injuries (blows to the head-head hitting windshield) can result in bone fragments penetrating the brain. There is a high rate of mortality following penetrating brain injury especially to the brain stem (Brookshire, 1997).
 
ischemic:
refers to a lack of blood-bourne oxygen. Ischemic strokes are more common than hemorrhagic strokes and may be caused by stenosis or thrombosis of the arteries, as well as by the presence of thrombo-emboli in the arteries. Almost always contralateral and therefore unilateral
 
Island of Reil (the Insula):
the cortical area that lies below the fissure of Sylvius; it is considered by some anatomists as the fifth lobe of the brain; it may be associated with the viscera. It has recently been associated with programming for muscle movement involved in speech. 

J 

K

kinesthesia:
feedback from muscle spindles (a more specific term than proprioception)  

L

lateral:
toward the sides
 
lateral aspect:
the part of the motor strip that is located on the lateral surface of the hemisphere; it is responsible for motor control of the upper body (including the larynx, face, hands, shoulders, and trunk)
 
lateral corticospinal tract (lateral pyramidal tract):
the fibers of the corticospinal tract that decussate at the pyramids
 
lateral fissure (fissure of Sylvius):
the fissure that separates the frontal and temporal lobes
 
lateral geniculate bodies:
the thalamic nuclei that receive visual information from the superior colliculi of the midbrain, process, and then transmit this information to the cortex
 
lateral pterygoid muscle of the oral cavity:
depresses, opens, and protrudes the mandible, as well as moving it laterally
 
lateral ventricles:
the two large ventricles (filled with cerebrospinal fluid) that have anterior horns located in the frontal lobes, inferior horns located in the temporal lobes, and which also extend posteriorly into the parietal lobes
 
left middle cerebral artery:
supplies blood to Broca's area, Wernicke's area, Heschl's gyrus, angular gyrus and also the  areas of the motor and sensory strips from the head to the hips.
 
left-right disorientation:
an inability to distinguish the left from the right; may be the result of damage to the angular gyrus in the hemisphere dominant for speech and language
 
left side neglect:
an impairment in the ability to recognize and respond to stimuli on the left side of the body
 
lenticular nucleus (lentiform nucleus):
one of the two structures that make up the basal ganglia; it is composed of the globus pallidus and the putamen; the lenticular nucleus is located between the caudate nucleus and the Island of Reil with its anterior aspect attached to the head of the caudate nucleus
 
levator veli palatini (oral cavity):
with the palatoglossal both raise the velum. They are innervated by the vagus nerve (CN. X).
 
limbic system (rhinencephalon):
the most ancient and primitive part of the brain; it is composed of both cortical and subcortical structures located on the medial, inferior surfaces of the cerebral hemispheres; the limbic system is involved in the processing of olfactory stimuli, emotions, motivation, and memory, and may be involved in cortical speech and language behavior
 
literal/phonological paraphasia:
More than half of the intended word is produced correctly. For example, a patient may say /pun/ instead of /spun/. In addition, transpositions of sounds can occur, e.g tevilision for television. (Brookshire, 1997).
 
long association fibers:
association fibers that connect areas that are located in different lobes of the brain (e.g., the arcuate fasciculus)
 
longitudinal fissure (interhemispheric fissure):
the split or gap between the right and left cerebral hemispheres that is lined with cortex
 
lower motor neurons:
second order neurons; the cranial and spinal nerves; the cell bodies of the lower motor neurons are located in the neuraxis (brain stem), but their axons synapse with the muscles of the body, sometimes called the final common pathway
 
lumbar puncture (spinal tap):
a diagnostic procedure in which a needle is inserted in the lower lumbar section of the vertebral canal to obtain a sample of cerebrospinal fluid