Lecture 4: Cerebral Asymmetry Flashcards
Laterality
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
Planum Temporale
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
Double Dissociation
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
Commissurotomy
surgical disconnection of the two hemispheres by cutting the corpus callosum
Split Brain
a brain in which the two hemispheres are isolated
Dichotic-Listening Tasks
an auditory procedure for simultaneously presenting different auditory input to each ear through stereophonics earphones
Dichaptic Test
a somatosensory procedure for simultaneously presenting different objects to each hand to determine which is more effective at identifying the objects
Apaxia
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
Preferred Cognitive Model
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
Cognitive Set
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
What are characteristics associated with the “left brain”?
analytical
logical
trees
three “R’s”
language
intelligence
dominant?
What are characteristics associated with the “right brain”?
holistic
intuitive
forest
artistic
music
emotional intelligence
spare tire
What are the anatomical asymmetries?
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
What is the asymmetry in the temporal lobes on the right and left sides of the brain?
planum temporal: larger in left hemisphere
Heschl’s gyrus: larger in right hemisphere
What is a commissurotomy?
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
What is the divided visual field technique?
recall that RVF –> LVC & LVF –> RVC
bilateral presentation
unilateral presentation
perceptual asymmetries (RT & Errors)
What is the Chimeric Face test?
differences may relate to laterality of face processing
What is confabulation in split brain patients?
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
What is the Wada Technique?
surgery planning
sodium amobarbital
blood supply is unilateral
one hemisphere is anesthetized
contralateral paralysis
speech output test
What is dichotic presentation?
contralateral dominance
more connections, more rapidly conducting
ipsilateral suppression
What is direct access theory?
input hemisphere processes the information
perfomance varies
What is the activating - orientating model?
attentional bias leads to information saliency
What is callosal relay model?
information is transferred to best side, which degrades performance
What is the spatial frequency hypothesis?
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
What is the relative spatial frequency?
the threshold shifts
relative to other frequencies in a given context (lower vs. higher range)
What is absolute spatial frequency?
is there a specific range?
doesn’t matter the context, only number
What are the hemispheric differences in auditory processing of pitch?
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
In what way do different modes of processing rely on different hemispheres?
left hemisphere = function
right hemisphere = appearance
What is global versus local processing?
left hemisphere = details
right hemisphere = overall, big picture
What is the transfer of sensory information between hemispheres?
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
