Brain-Behavior Relationships
Overview of Topics
PREFRONTAL CORTEX
PREMOTOR CORTEX
POSTCENTRAL GYRUS
ANGULAR GYRUS
INFERIOR PARIETAL CORTEX
TEMPORAL CORTEX
WERNICKE'S AREA
PARIETO-OCCIPITAL CORTEX
OCCIPITAL LOBE
VISUAL AGNOSIA
Brain-Behavior Relationships
I. Prefrontal Cortex:
(Behavior Regulation - Goal oriented behavior -- occurs by comparisons of
the plan of action with the actual effects of movements).
A. Extensive Lesions
- Can't do complex motor sequencing (Light and smoke a cigarette).
- Gross disintegration of acts involving objects.
- No distress or attempts at correction.
- Frontal apraxia - disturbance of preliminary synthesis.
- Perseveration
- Serial tasks more likely disturbed.
- Cannot reproduce drawings from memory.
- Problem is with plans rather than movements.
- Patient's behavior can be controlled by irrelevant stimuli.
B. Less Extensive Lesions
- Carry out simple single acts after visual or auditory instructions.
- Examples contrary to spoken instructions give them trouble (can't follow verbal instructions).
- Can't shift set if instructions are varied.
- Instructed to squeeze rubber bulb patient will:
- make verbal statement but not correct motor response.
- begin squeezing without stopping
- can give verbal statements but can't make proper response.
- with less damage can't discriminate: left to red, right to green
- even after patient learns response he may not be aware of it.
- difficulty altering response sequence.
- One of first signs of frontal cortex involvement -- loss of speech regulation of fine movements.
- Frontal - only lesion which disrupts ANS components of the orienting R.
- Stimulus looses signal status.
- may cause the development of arousal reactions that do not extinguish for a long time.
- Disturbance of active scanning.
- perceive far fewer details from a picture
- difficulty with fast-moving objects
- Patients can't find hidden figures.
- perceive one aspect and make impulsive judgment as to the total
- series perception - altered by first perceptions
- Alpha blocking in all patients to spoken instructions except frontal lesions.
- Show series of figures for 30 sec. & have reproduce; frontal patients may insert some of first series in second.
- Give verbal instructions to draw circle, cross, square.
- Replicate with pairs.
- Mixed
- Increase to 5 elements
- frontal - more perseveration
- temporal tend to misconstruct word meanings.
- temporal - improve if repeat instructions aloud
- no improvement with frontals
C. Analysis of Motor Functions
- Prerequisite of Motor Act
- muscle strength
- muscle tone
- functional afferent systems
- kinesthetic impulses
- face patient
- raise hand
- position hand frontally, sagittally, horizontally
- touch eye and ear
- two hand position
- repeat with spoken commands
- intact optic - spatial afferent system
- motor sequencing
- Plans for activity
II. Pre-motor Cortex
(Responsible for kinetic organization of movement once started, transfer, smooth sequencing.)
- Touch fingers with thumb AFAP (reveals paresis, lack of precision, pathological dystonia, ataxia).
- Separate and close fingers AFAP
- Clinch and relax fingers (both hands) (AFAP - selective fatigue?)
- Alternate clinch - extended
- post central lesions will not disrupt
- most impaired with anterior corpus callosum lesions.
- Place hands in front (tap twice with right, once with left).
- Reverse
- Pre-motor - patient carries out indiscreet steps rather than a series.
- Pre-motor - rough but correct mistakes
- Frontal - tap haphazardly without correction
- Fist - ring test - can't do them in series.
- reverse sequence produces problems
- Fist-edge-palm test - non automatic in character
- Piano playing test (first forward then reverse)
- frontal patients can't reverse
- pre-motor may improve with spoken commands or feedback
- frontals - may repeat correctly but still can't make proper movement
- Graphic Test
A. Investigation of Oral Praxis
- Smile (symmetrical)
- Tongue extension and movement
- Can't thread a needle
- Loss in automatism and fluency of speech
- words may come in wrong order.
- speaks in telegraphic style
- Loss of intellectual functions?
III. Post Central Gyrus
(responsible for topological organization of motor impulses, erecting and giving precision to the motor action)
A. Kinesthetic basis of movement
- Eyes closed - patient is to position hand to match position of other as set by examiner.
- Passive finger detection
- Two point threshold
- Von Frey hair threshold
- Vibration sense
- With lesion - most severe changes in distal parts of limbs.
- pain returns first
- pressure and touch next
- temperature next
- position sense and passive movement
- vibration
- stereognosis did not return
- Pin - point vs. head
- Touch area on skin and have patient point to area on contralateral side.
- Fasten a button.
- Tie a shoelace.
- Left hemisphere lesions may also give problems with left hand.
- Right Parietal and right frontal - defects in visual but not auditory tasks.
- Left parietal - deficits in both
- Left frontal - no deficit in either
IV. Supramarginal Gyrus
- astereognosis
- fingertip number writing
may have disturbance in body schemes
- Right - Left confusion
- finger agnosia
- Gerstmann's syndrome - left inferior parietal lesion R-L confusion, finger agnosia, agraphia, acalculia.
V. Angular Gyrus
- Pure word blindness (can't read aloud or comprehend written words)
- Can copy words but not write from dictation
- Dyslexia, dysgraphia
- Spelling loss
- Can name and recognize object (have multiple associations)
- Loss of color naming but can't match colors.
- Loss of ability to read music.
VI. Inferior Parietal Gyrus
- Can't organize perceptions into a single structure
- Right - Left Confusion
- Problems dressing
- Can't tell time without numbers on clock
- Can't find bearings on a map
- Constructional apraxia - Benton's test
- Can't draw letters easily
- Severe loss - can't copy
- Less severe - only have loss of memory when required to reverse?
VII. Temporal Cortex
A. Right temporal lobe
- Seashore loss (area 22) or may remain asymptomatic
- Modified taps at 0.5 to 1.5 intervals
- Have patients reproduce patterns presented acoustically.
- Reproduce verbal instructions
- 2, 3, 2, 2 strong - 3 weak, etc.
- reproduce pattern while saying aloud
- premotor lesions
- use of complex tools
- discreet taps - poor rhythm
- no difference between acoustic and verbal presentation.
- verbal rehearsal - temporals improve, frontals don't
- Confused by sketchy drawings
- Impaired discrimination of fragmented concentric circle patterns.
- Can't remember paragraph previously observed.
- Difficulty with any visual stimulus that can't be easily attached to a name.
- Problems on recurrent nonsense figures
- Impaired stylus maze learning.
B. Left Temporal
Pattern description (auditory sensory area)
On nonverbal - function as normals)
- Sound interpretation appears to be more a function of association areas in dominant hemisphere.
- Superior temporal gyrus stimulation and n irritation produces sensation of movement (vertigo)
- also somewhat by parietal area stimulation
- Cochlear disease - strong subjective noises w/ high freq. loss (gradual onset)
- Nerve disease - loss of low frequency range (more rapid onset.)
- Thalamic injury - distortion and unpleasant character of sounds.
- Cortical Disease
- inability to locate sound
- may see HH (upper homonymous quatranopoia)
- wernicke's area - word deafness
- Tinnitus - reception to pathway disease.
- Mild impairment on dicotic listening test.
- Greatest impairment on retest after one hour unannounced.
- Impaired learning of words, 3 digit numbers, nonsense syllables. No problem with nonsense drawing (reverse for right)
C. Anterior Temporal
- Stimulation
- Deja vu
- feelings of remoteness
- hallucinations (auditory and/or visual)
- elevated blood pressure
- uncinate seizures - lip-smacking, olfactory aura.
D. Middle Temporal
- Stimulation - arrest of speech
- Can't remember words presented orally (especially series of three or four)
- Difficulty reproducing under complicated conditions.
- Similarities disturbed.
- Phonemic bearing intact but defect in audio verbal memory
- patient can't retain short series of sounds, syllables, or word:
- modality specific memory loss.
- deficit not present with long ISI's
VIII. Wernicke's Area (22 Post)
- No permanent hearing loss.
- Problems with pattern discrimination.
- Loss in ability to decipher the phonemic code.
- Can copy but can't write from dictation.
- Noun more significantly impaired.
- Problems with word memory.
- Left hemisphere lesion may not disturb musical hearing.
- Evidence now that neocortical lesions produce severe memory defects.
A. Right Temporal
- Vision - impaired on recurrent nonsense figure test (any visual pattern without name).- photographs
- Auditory - impaired on tonal patterns (Tonal memory Test)
- impaired on timbre (Seashore M of M Talents)
- effects greater when auditory cortex spared.
- Spatial - stylus maze learning impaired (both visual and proprioceptive S).
B. Left Temporal
- Verbal memory tasks - impairment on both auditory and visual.
- impaired on learning to recognize words nonsense syllables, 3 digit numbers
- dichotic digits test impairment (measures more temporal cortex involvement)
- delayed recall score low with hippocampal involvement
C. Left Frontal
- Word fluency impairment Impairment of spontaneous speech
IX. Parieto-occipital Cortex
A. Right Hemisphere
- Can match position of pencil held in various positions.
- Right - left homonymous heminopsia
- Paragnosia - difficulty with visual recognition of objects
- Prosopagnosia - recognition of faces.
- Spatial loss greater than with left lesions.
- Unilateral spatial agnosia
- Lack of awareness of own defects.
X. Parieto-temporal-occipital cortex
- Can understand word meanings but can't grasp meaning of the whole construction.
- Ability to evoke visual images in response to a given word.
- Gross inability to draw a picture of an object named.
XI. Occipital Lobes
A. Area 17
- Unilateral ablation of 17 results in complete homonymous hemianopsia of the contralateral field
- partial deficits often occur due to macular sparing
- Bilateral ablation of 17 results in bilateral homonymous hemianopsia
- (cortical blindness) sometimes called Anton's syndrome
- The individual may deny blindness and confabulate
- Similar deficits may occur without lesions of area 17 when complete oblation of the optic radiations occur.
- Ablation of the optic radiations can be differentiated from lesions of area 17 by the fact that damage to area 17 is more often characterized by macular sparing
B. Areas 18 and 19
- Deficits may occur in visual recognition and reading.
- If the lesion does not extend beyond 18 and 19 but involves both hemispheres or its connections then a visual agnosia results.
- Rare to find this type of deficit without involvement of parieto-occipital and/or inferior parietal regions.
- A limited unilateral ablation may produce deficits in visual following
- A unilateral lesion extending past 17, 18, and 19 may re sult in 'unilateral spatial agnosia'.
- Degree of deficit is related to the extent of lesion, i.e., how much parietal or temporal is included?
- Severe - can't recognize simplest objects
- Less severe - can recognize familiar objects but not more complicated objects.
- Based on parts of an object, the subject will make logical guesses but can't synthesize the signs into an integrated whole.
C. Types of Visual Agnosias
- Visual object agnosia
- Prosopagnosia - inability to recognize faces (special case of (1).
- occurs more frequently with right hemisphere damage
- Color agnosia
- Simultanagnosia - inability to absorb more than one aspect of a visual stimulus at a time.
- accompanied by ataxia of gaze.
- Metamorphopsia - objects recognized accurately but subjectively distorted
D. Integrative Functions
- Optic - kinesthetic - motor organization
- Patient instructed to reproduce position of experimenter's hands with own. (arrange so can't see own hands).
- perseverative movements - frontal lesions.
- Left frontal - word fluency
- Hippocampal - bilateral - severe memory deficit.
