Lecture 4: Cerebral Asymmetry

Question 1

Laterality

Answer 1

refers to the side of the brain that controls a given function

hence, studies of laterality are undertaken to determine which side of the brain controls various functions

Question 2

Planum Temporale

Answer 2

an area comprising the anterior and posterior superior temporal planes (aSTP and pSTP), together with auditory cortex (Hesch’s gyrus) within the lateral (Sylvian) fissure

Question 3

Double Dissociation

Answer 3

an experimental technique by which two neocortical areas are functionally dissociated by two behavioral tests

performance on each test is affected by a lesion in one zone but not in the other

Question 4

Commissurotomy

Answer 4

surgical disconnection of the two hemispheres by cutting the corpus callosum

Question 5

Split Brain

Answer 5

a brain in which the two hemispheres are isolated

Question 6

Dichotic-Listening Tasks

Answer 6

an auditory procedure for simultaneously presenting different auditory input to each ear through stereophonics earphones

Question 7

Dichaptic Test

Answer 7

a somatosensory procedure for simultaneously presenting different objects to each hand to determine which is more effective at identifying the objects

Question 8

Apaxia

Answer 8

the inability, in the absence of paralysis or other motor or sensory impairment, to make or copy voluntary movements, especially an inability to make proper use of an object

Question 9

Preferred Cognitive Model

Answer 9

use of one type of though process in preference to another

for example, visuospatial instead of verbal

sometimes attributed to the assumed superior function of one hemisphere over the other

Question 10

Cognitive Set

Answer 10

a tendency to approach a problem with a particular bias in thought

for example, the Gestalt bias stresses the whole, whereas the analytical bias stresses individual components

Question 11

What are characteristics associated with the “left brain”?

Answer 11

analytical
logical
trees
three “R’s”
language
intelligence

dominant?

Question 12

What are characteristics associated with the “right brain”?

Answer 12

holistic
intuitive
forest
artistic
music
emotional intelligence

spare tire

Question 13

What are the anatomical asymmetries?

Answer 13

right hemisphere larger & heavier than left

right hemisphere extends further anteriorly

left hemisphere extends further posteriorly

slope of Sylvain fissure gentler on left hemisphere

temporal lobes have marked asymmetry

Question 14

What is the asymmetry in the temporal lobes on the right and left sides of the brain?

Answer 14

planum temporal: larger in left hemisphere

Heschl’s gyrus: larger in right hemisphere

Question 15

What is a commissurotomy?

Answer 15

surgical procedure of severing corpus callosum (200-250 million nerve fibers)

two hemispheres can no longer communicate

split-brain

sensory information is sent to only one hemisphere

vision example: input from left visual is sent only to right brain and input from right visual field is sent to left brain

Question 16

What is the divided visual field technique?

Answer 16

recall that RVF –> LVC & LVF –> RVC

bilateral presentation

unilateral presentation

perceptual asymmetries (RT & Errors)

Question 17

What is the Chimeric Face test?

Answer 17

differences may relate to laterality of face processing

Question 18

What is confabulation in split brain patients?

Answer 18

spontaneous production of false memories: events which never occurred, actual events displaced in space or time

may be elaborate, detailed, bizarre, or mundane (e.g., had eggs for breakfast)

not lying deliberately or trying to mislead; low levels of awareness

Question 19

What is the Wada Technique?

Answer 19

surgery planning

sodium amobarbital

blood supply is unilateral

one hemisphere is anesthetized

contralateral paralysis

speech output test

Question 19

What is dichotic presentation?

Answer 19

contralateral dominance

more connections, more rapidly conducting

ipsilateral suppression

Question 20

What is direct access theory?

Answer 20

input hemisphere processes the information

perfomance varies

Question 21

What is the activating - orientating model?

Answer 21

attentional bias leads to information saliency

Question 21

What is callosal relay model?

Answer 21

information is transferred to best side, which degrades performance

Question 22

What is the spatial frequency hypothesis?

Answer 22

lower frequency: need to look at things overall, not the details
higher frequency: need to look at the details, not the bigger picture

low frequency = right hemisphere (more global aspects)
high frequency = left hemisphere (more details)

right hemisphere has specialized area that makes facial recognition more efficient

Question 23

What is the relative spatial frequency?

Answer 23

the threshold shifts

relative to other frequencies in a given context (lower vs. higher range)

Question 24

What is absolute spatial frequency?

Answer 24

is there a specific range?

doesn’t matter the context, only number

Question 25

What are the hemispheric differences in auditory processing of pitch?

Answer 25

dichotic listening task: hear tones in either ear, not at the same time, randomized which ear, need to press button when they hear a target tone

left hemisphere = higher frequencies
right hemisphere = lower frequencies

range is not absolute, more relative

Question 26

In what way do different modes of processing rely on different hemispheres?

Answer 26

left hemisphere = function
right hemisphere = appearance

Question 27

What is global versus local processing?

Answer 27

left hemisphere = details

right hemisphere = overall, big picture

Question 28

What is the transfer of sensory information between hemispheres?

Answer 28

when an image is projected to the left visual field: first goes to right then quickly crosses over, some delay

when an image is projected to the right visual field: first goes to left then quickly crosses over, some delay

demonstrates that it takes time to cross over