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definitions D


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d' (d prime)
from SIGNAL DETECTION THEORY; signifies discriminability of the signal (ie target stimulus) fr. bkgrd. stimulation w/o regard to the threshold or response bias
decerebrate rigidity
marked rigid extension of the legs bilaterally; arms are extended and internally rotated; the posture results from bilateral cerebral dysfx. extending to upper brain stem proximal to the red nucleus
decorticate rigidity
marked bilateral rigid flexion of the legs and of the arms to the chest; assoc. w/ bilat. dysfx of cerebral cortex; lesioned areas may include gray and white matter, internal capsule, thalamus bilaterally
decubitus ulcer
skin breakdown/bedsore; occurs most commonly at sacrum, heel, back of head; from constant pressure restricting bloodflow
crossover of paired fiber tracts across the midline
deep brain stimulation
approach to treatment of parkinsonism and chronic pain; constant hi-frequency stimulation applied to thalamic nuclei via pulse stimulator implanted near the collarbone
deep structure
coined by Noam Chomsky; refers to underlying meanings rather than exact linguistic form of a spoken or written expression; deep structures contain no words--rather, meaning conveyed through words and their order, referred to as "surface structure"
deep tendon reflexes
invol. muscle contractions after percussion of a tendon; hyperactive reflexes suggest upper motor neuron impairment, while hypoactive ones suggest lower motor neuron impairment
deja vu
a normal infrequent phenomenon, partic. in children and teens, that an experience has already been lived through; sometimes manifest in seizure auras and psychiatric d/o's such as schizotypal pers. d/o.
delayed response tasks
tasks assessing memory in animals; require recall of location of a reward until a response is allowed; two types--delayed match-to-sample and delayed response alternation; in former animal must recall into which well food has been placed; in the latter the food is switched to the 2nd of two wells and the animal must learn this switch--performance on this drops following dorsolateral frontal lesions
delirium tremens (DTs)
cond. assoc. w/ tremor, agitations, hallucinations, confusion; develops several days after abrupt withdrawal from ETOH in alcoholics; risk for generalized status epilepticus
generalized loss of cog fxs due to cerebral disease in absence off a confusional state; DSM criteria--impairs soc./occ. fx, must incl. memory impairment with 1+ of the following: aphasia, apraxia, agnosia, impaired exec. fx.,; DSM does not stipulate progressive nature or irreversibility, though this was part of prev. def'ns.
name several types of dementia causes
static lesions, TBI, AIDS progressive neurodegenerative d/o's incl. AD, Pick's, Creutzfeldt-Jakob, Parkinson's, Huntington's
AIDS dementia characteristic features
apathy, impairment in conc., memory, executive fxs, also psychomotor slowing; viewed by some as a subcortical dementia; in later stages usu. includes myoclonus or parkinsonism
alcoholic dementia characteristic features
follows chronic abuse of 15-20+ yrs; frontal lobes signs incl. apathy, poor hygiene, poor judgment, lower cog. efficiency, attention and recent memory, flattened affect; clinically similar to neurosyphillis; assoc. w/ enlarged cerebral ventricles, frontal atrophy, thinning of cortex
axial dementia
prototypical form is Korsakoff's syndrome; results from lesions of midline (axial)brain structures such as thalamus, hippocampus, fornix, mamillary bodies, hypothalamus
cortical dementia
prototypical form is AD; char. by loss of higher cortical fx (eg aphasia, apraxia, agnosia); contrast with subcortical dem. which has slowed proc. speed as hallmark; imprecise and controversial distinction as cort. and subcort. are imprecise terms and most forms of dementia incl. subcortical changes even if termed "cortical dementia"
dementia of Alzheimer's type (DAT)
describes dementia that appears to reflect AD; dx based on bx b/c pathology cannot be verified
dementia pugilistica
in longterm boxers; char. by forgetfulness, slowness in thought, dysarthria, wide-based unsteady gait; also common--flattened affect and parkinsonian extrapyramidal sxs
dialysis dementia
may follow yrs of hemodialysis for chronic renal failure; char. by subtle personality chg, speech and cog. impairment, may include asterixis, mutism, myoclonus, seizures; less common now that aluminum has been removed from dialysate and water in dialysis is being purified
lewy-body dementia
a Parkinson Plus syndrome w/ clinical presentation that may lk similar to AD or PD; cortical neurons seen to include Lewy bodies, but senile plaques & neurofibrillary changes not seen; typically see parkinsonian extrapyramidal d/o plus dementia w/ delusions, visual halluc., & fluctuations
multi-infarct dementia
form of vascular dementia; develops from repeated small cerebral infarctions; often assoc. paresis, clumsiness, rigidity, abnormal reflexes; contrasts w/ AD in its abrupt onset and stepwise progression; operationalized using the Hachinski ischemia scale
presenile vs. senile dementia
develops before 60-65 vs. post yrs; not used commonly since similar neuropathologic chgs. seen in pre-senile and senile DAT; but Pick's disease still freq. called a pre-senile dementia b/c usu. begins b/w 55-60 y.o.
semantic dementia
dementia featuring selective impairment in semantic (i.e. meaning-based) memory; other fxs rel. spared, incl. nonsemantic language components; may involve focal cortical degeneration with main effect on temporal lobes
subcortical dementia
char. by slowed thought process, problems with memory, visual-spatial fxs, mood/affect; includes Huntington's, Parkinson's, progressive supranuclear palsy, HIV dementia
vascular dementia
dementia that results from cerebrovascular disease; causes may include repeated infarcts, single insult to critical area, chronic ischemia w/ no discrete events
disintegration of myelin sheaths surrounding nerve fibers; retards neural conduction; MS is most common disease but other causes include different leukodystrophies, toxins and viruses
what is the most common peripheral demyelinating disease?
Guillain-Barre syndrome
extension of the cell body; the process of a neuron that receives synaptic inputs; other anxons or dendrites terminate onto it
block normal connections to a nerve
denervation supersensitivity
refers to phenomenon in which nerve receptors that are partially cut off from connections develop supersensitivity to remaining inputs; results in partial restoration or sparing of fx
dependent variable
in experimental design, the outcome measure of interest
derivational error
error of single word in reading, writing or speech; correct morphemic root is used but in a different part of speech (e.g. amuse rather than amusement, infer rather than defer)
region of skin; supplied by (afferent) nerve fibers by solitary posterior spinal root
developmental dysphasia/aphasia
lack of language skill development, typically w/o identifiable etiology; may be primarily expr., receptive, or both; in DSM classified as a "language disorder"
deviation quotient
std. score which reflects performance relative to a reference group's mean
dexamethasone suppression test
procedure involved in dx of Cushing's disease. In normals, cortisol secretion is suppressed for 24 hours following admin of dexamethasone, but does not occur in those with C's disease
temporary loss of fx that can result from acute focal brain damage in a region that is adjacent to the region resp. for that fx, or a region connected to the region by fiber tracts
how may the phenomenon of diaschisis help to account for functional recovery after a focal brain injury?
as the functional continuity b/w various areas of the brain is disrupted following a lesion, and as this disruption extends beyond the direct effect of the lesion, resolution of these disruptions may help account for recovery of fx
inferior portion of the forebrain
what are the constituents of the diencephalon?
thalamus, hypothalamus, subthalamus, lenticular nucleus
differential reinforcement of appropriate behavior
bx modification technique; reinforce positive bxs, and ignore negative bxs to help extinguish them
diffuse axonal injury (DAI)
injury to brain tissue that is widespread, patchy, and macro- & microscopic; assoc. w/. rotational forces in TBI sustained at high speed; produced by shear strains b/w brain tissues that differ in density; also results from released cytotoxic neurochemicals (eg free radicals), and hours after injury from 2ary degeneration of cells
paralysis of corresponding limbs that is bilateral
double vision
disconnection syndrome
refers to any d/o in which cortical areas that normally work together are isolated from e/o, typically 2ary to white matter lesions
name one type of disconnection syndrome
alexia without agraphia-- lesion in the visual cortex of the dominant hemisphere exists along with CC pathways from nondominant hemisphere
name one d/o that is incorrectly referred to as a disconnection syndrome
conduction aphasia; while the term "disconnection syndrome" is not anatomically correct in this case, it is retained for historical continuity
What did Geschwind have to say about disconnection syndromes?
Geschwind asserted that many NP syndromes such as aphasias, apraxias, agnosia, disturbances of memory and bx issues tied to limbic lesions were due not only to specific lesioned areas but also to disruption of info. txfr from one brain region to another
discriminant analysis
technique in multivariate statistics that describes diffs. b/w 2+ grps. on a set of measures--descriptive discr. analysis; or that classifies Ss into grps. based on a set of measures--predictive discriminant analysis
what does it mean to be "disoriented to person"?
not that one is disoriented towards one's one self (eg name); rather, it signifies that one is disoriented w/r/t others in one's environment; e.g., failure to recognize that one's being surround by nurses might indicate that one is in a hospital; can also refer to those who are nonresponsive to their name despite being awake
displacement refers to what, w/r/t memory process?
refers to the memory process in new information causes previous information to become lost to one's attention span
what is the doll's eye reflex/maneuver, and what is its clinical significance?
the reflexive eye mvmt. in the opposite direction to which head is moved; absence indicates brainstem legion
dopamine is implicated in what disorders and syndromes?
certain mvmt. d/o's (Parkinson's, Tourette's)and several neuropsychiatric syndromes incl. schizophrenia, ADD
what causes the following constellation of symptoms seen in Parkinson's: rigidity, tremor, akinesia?
decreased dopamine in the nigrostriatal pathway
what can be associated withi excessive DA levels in levodopa tx during later stages of Parkinson's?
dyskinesia, an excess of movement
what is the primary mechanism by which antipsychotics work?
blockage of DA receptors in the striatum
DA is a precursor of what NTs?
norepinephrine and epinephrine
bending backwards or turning upwards of the hand/fingers or feet/toes
double dissociation
technique by which 2 fxs are determined to be selectively and independently affected; needed in developing modular theories of cognitive functioning
What is another name for Down syndrome, referencing the relavant chromosomal abnormality?
trisomy 21
drug potentiation
synergistic action of 2+ drugs when this is more powerful than their additive effects
dual code theory
theory of memory holding that concrete words can be represented by both an IMAGINAL and a VERBAL code, while abstract words can only be represented by a VERBAL code
dual task performance
an experimental technique that helps to determine whether two tasks share overlapping/common resources; if interference is shown (ie slower/more error-ridden performance), suggests common resources are being drawn from
Duchenne muscular dystrophy
sex-linked d/o; progresses after inital weakness in thighs and shoulders; results in wheelchair-boundedness and respiratory insufficiency by end of childhood; assoc. w/ mild mental retardation
speech d/o due to impaired muscular control of speech mechanisms; origin may be either peripheral or central
what distinguishes dysarthria from apraxia of speech?
dysarthria includes consistent articulation errors in both voluntary and involuntary speech activities; apraxia of speech includes inconsistent articulation errors
ataxic dysarthria
imapired articulation & prosody; slurred speech; resulting from cerebellar lesions, pt. may appear drunk
flaccid dysarthria
hypotonia & weakness of the speech muscles; due to lesions in motor units of cranial or spinal nerves
hyperkinetic dysarthria
abnormal rhythmic speech that is assoc. w/ invol. mvmts (such as choreiform, ballistic, or athetoid); usu. assoc. w/ basal ganglia lesions, subthalamic nucleus lesions can also be involved
hypokinetic dysarthria
char. by monotone speech, reduced speech range; assoc. w/ basal ganglia lesions
spastic dysarthria
char. by slow speech, worsens with fatigue; assoc. w/ bilateral upper motor neuron lesions
unilateral upper motor neuron dysarthria
results from weakness of tongue/lower facial muscles; assoc. w/ acute upper motor neuron lesions; mild, and usually sx resolve or diminish
dysconjugate gaze
gaze in which the eyes are unable to move together in aligment; may result from congenital d/o, lesion of the brainstem or of the cranial nerves controlling the extraocular muscles, or disease of the extraocular muscles (eg myasthenia gravis); fixation point is uncoupled, leading to diplopia
impairment of voluntary mvmt. characterized by excessive mvmt.; may be choreic, dystonic, stereotypic, or ballistic; usu. very disabling; seen in Parkinson's, and sometimes in those with neuroleptic treatment
1ary, congenital, or developmental disability in learning to read/spell that does not result from MR, aphasia, psych. d/o, or lack of motivation or educational exposure; vs. ALEXIA, which signfies an acquired reading impairment
dyseidetic dyslexia
features inability to read words as a whole; reads phonetically, sounding out familiar words as if they were new; spelling mistakes usu. phonetic
dysphonetic dyslexia
reading depends heavily on sight vocabulary; tend to respond to words as individual configurations; weak word attack and phonetic decoding/coding skills; nonphonetic spelling errors; may make semantic substitution (e.g. "scary" for "afraid")
mixed dysphonetic-dyseidetic dyslexia
characterized by inability to dev. phonetic-word synthesis skills & to perceive letters & words as visual gestalts
L-type dyslexia
premature reliance on a left hemisphere linguistic strategy, in which semantic and syntactic strategies are generated; reading is fast and inaccurate
P-type dyslexia
too much reliance on rt. hemisphere bias emphasizing perceptual strategies--a normal approach in early stages of reading development, but there is a failure to develop the more advanced semantic and syntactic strategies; read slowly in fragmented fashion, though not too inaccurate
measuring of distance in muscular acts/ control of range of movement in muscular acts is disordered; often tested with finger-to-nose test; a cardinal sign of cerebellar disease & cerebellar ataxia
impaired ability to chew/swallow food or liquid; a prominent component of bulbar palsy
what types of lesions may result in dysphasia?
lesions in the corticobulbar tracts; lesions in the 5th (trigeminal) 7th (facial) 9th (glossopharyngeal) 10th (vagus) or 12th (hypoglossal) cranial nerves
impairment of phonation (sound generation)from the larynx; reflect abnormal vocal fold vibration; may result in breathiness, hoarseness, harsh vocal quality
abnormal tissue development
slow involuntary arrhythmic muscle contractions; result in forced & distorted postures; may be sx of a disease such as Parkinson's or exist as an independent disease; can be induced by levodopa
degeneration with loss of fx

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