Chapter 11/12 Cerebral Asymmetry Flashcards
Define Laterality
idea that the two cerebral hemispheres have separate functions which leads to idea that two different minds control our behaviour
what are the 5 variables that complicate research on laterality
Relative, not absolute
cerebral site as important as understanding function as cerebral side
environmental and genetic factors
range of animal exhibit
we act as though we are single minded
Explain relative, not absolute
although one side can be more important in a function, the other hemisphere is still involved
explain environmental and genetic factors
females and left handers appear to be less asymmetric than right handers and males
explain cerebral site as important as understanding function as cerebral side
best to think of cortical functions as being partially localized and the hemisphere side is just one feature of the localization
explain range of animal exhibit
certain animals (monkeys, songbirds) also have functionally and anatomically asymmetrical brains even though they are not identical to humans
explain we act as though there is a single mind
although each hemisphere is specialized, we normally act as though there is a single cognitive processor
8 major anatomical differences between 2 hemispheres
- RH = larger and heavier while LH has more white matter
- structural differences provide anatomical basis for specialization in language and music
- correlates with asymmetry of thalamus, left is dominant for language in thalamus
- slope of lateral fissure is gentler on LH
- Broca’s area is organized diff on left and right. 1/3 larger on right, left affects grammar
- distribution of nts are asymmetrical
- RH extends further anterior, LH extends posterior. lateral ventricles x5 longer on RH
- thicker cortex in LH, but larger SA in RH
what about neuronal asymmetry in the 2 hemispheres
the more branching points, allow the cell more degrees of freedom with respect to its function
abundant branches in Broca’s area
What about genetic asymmetry in the 2 hemispheres
found genes that are expressed differently in each hemisphere and that epigenetic changes likely influence each hemisphere differently
Applying electrical current to the cortex of a conscious patient has 4 general effects (___ excitatory and ___ inhibitory)
3 excitatory and 1 inhibitory
1. brain has symmetrical and asymmetrical
2. RH has perceptual functions not shared by LH = stimulation of RH produces phenomena (of alterations in patients interpretation of surroundings) much more frequently than LH
3. stimulating L frontal or temporal accelerate speech production
4. stimulation blocks function = inhibitory affect is apparent only when the patient is actively engaged in those behaviours
Explain double dissociation experiment
LH lesions produce deficits in language that are not produced by RH lesions.
Performing spatial tasks are disrupted by RH lesions, but not LH.
Bc RH lesions disturb tasks not disrupted by LH and vise versa, two hemispheres are doubly dissociated
Define commissurotomy
surgical procedure of disconnecting two hemispheres of the corpus callosum (bc of epileptic seizure meds not working)
problems resulting from commissurotomy
the brain cannot join together the two different views of the L and R
What is the interpreter
split-brain patients are presented with two images, asked to select a third image to match the scene. Each hand chooses an option appropriate to the scene, but when asked to explain the choice, answers based on the right hand in terms of right scene
What is the Wada Test
using carotid sodium amobarbital injection
shows 98% of right handers and 70% of left handers show speech disturbance after sodium injection into LH but not after RH
explain asymmetry in visual system
allows for selective presentation of visual info to each hemisphere of the brain
LH better at processing verbal info while RH is better at processing visual faces
explain asymmetry in auditory systems
both hemispheres receive info from both ears
found people remembered more info from right ear than left because it has a shorter path to travel
LH processes language part of music, RH excels with musical stimuli
explain asymmetry in somatosensory system
has crossed nature
found R hand advantage for identifying letters (because would be LH) and L hand advantage for other shapes
explain asymmetry in motor systems
sensory input processing isnt equal on both sides, it is difficult to study motor control differences
what are the two main methods to figure out motor asymmetries
- direct observation
- inference tasks
What is direct observation task for motor asymmetries
watching people move in their everday life
found right side of mouth moves more when talking, therefore left side has more control in this
found use right hand more when talking but left for other things
what is inference tasks for motor asymmetries
doing two complex tasks at once
different sides of the brain handle multitasking differently
each side of the brain seems to have its own strengths in movement
what is the correlation problem with laterality studies about brain function
the behavioural tasks don’t always match with the brain tests.
maybe because behavioural tasks measure more than just which side of the brain in dominant in a task
Define extreme unilateral specialization
suggests each hemisphere has distinct specialized functions
Explain what the thoughts are on how the hemispheres process information differently
left = more analytical and sequential
right = holistic and integrated
What is the interaction model
that both brain hemispheres can handle all functions but typically dont
What are the 3 reasons for the interaction model
- simulation processing = both hemispheres work together but focus on different aspects of processing
- inhibitory interaction = each hemisphere suppresses the function of the other
- Selective attention and analysis = each hemisphere pays attention to different information. If one is overloaded, the other can help
is lateralization of the brain unique to humans
no
