Exam 2- Lecture 4

Question 1

Left brain vs right brain

Answer 1

Cognition

left: language
right: visuospatial processing

Personality

left: verbal, analytic, dominant, copywriter
right: artistic, the instantaneous, “flash-of-insight”, art director

Question 2

Political brain

Answer 2

Democrats
-activity in left posterior insula
Republicans
-activity in right amygdala

Question 3

Corpus callosum

Answer 3

Major pathway between hemispheres
Major fiber tract for inter hemispheric communication
Transcallosal info transformation takes time (20 ms delay)

Question 4

Homotopic projections

Answer 4

Most common in association areas

Question 5

Heterotopic projections

Answer 5

Mirror ipsilateral projections; fewer in number

Question 6

When language and speech systems in Lh are down

Answer 6

Impaired naming

Intact recognition in the match-to-sample task

Question 7

When CC is cut or disrupted

Answer 7

Each hemisphere still gets contralateral sensory input (e.g., info from left visual field goes to right hemisphere

Motor cortex in each hemisphere still controls contralateral effectors (e.g., commands from left M1 control right hand)

BUT hemispheres CANNOT communicate

Provides opportunity to present info to only one hemisphere and see if it gets processed

Question 8

Split brain patients

Answer 8

Surgery for epilepsy (cut CC to prevent seizures from jumping to other hemisphere)

Perform visual search task twice as fast as normal
-suggests that each hemisphere has its own mind

Question 9

Spatial task in RH

Answer 9

Coordination of motor plans disrupted in split-brain patient, resulting in competition

Spatial figure construction task in perfect with left hand (RH) but fails with right hand (LH)

Question 10

Language in LH

Answer 10

Special apparatus

• focus on center, one word presented on each side of screen
• > Word on right screen
• ->to LH (speech), when asked say only saw word on right side
• > Word on left screen
• ->to RH (process stimulus), when asked to pick up object, pick object from left side (visuospatial task)

Question 11

Posterior CC cut

Answer 11

Transfer of sensory (visual, tactile, and auditory) info disrupted, but higher-level (semantic) info can still be transferred

Opposed to full CC cut -> no (or close to no) data transfer

Question 12

Semantic/conceptual relationship in LH

Answer 12

Task: pointing to a pic that best depicts to sequentially presented words when they are casually related (making inferences, LH function)

Results:
RH (left hand) unable to preform
LH (right hand) OK

Question 13

LH

Answer 13

Relational
Semantic relationship
Interpreter

Question 14

Split brain study contributions

Answer 14

Functional specifications
LH: language production, analytic
RH: visual-spatial processing and action

Each hemisphere can function independently (to some degree)
-even double cognitive capacity

No cross-hemisphere communication, with some residual cross-task via subcortical pathway

Question 15

Limitations to split brain studies

Answer 15

Patients not “normal” prior to study
Findings are from a handful of patients
Brain imaging studies show that both hemispheres contribute to all functions but to a different degree

Question 16

How to study hemispheric specialization theories in normal cognition to test theories

Answer 16

Visual hal-field presentation without eye movements
-short exposure duration (under 200 ms) or fixation monitoring (no eye movement)

Which visual-field yields a faster/more accurate response?

• LH or RH advantage
• effects are very small (e.g., 20 ms)

Conclusion:
LH or RH dominance

Interpretation:
LH or RH has better access to the info/process required for the task

Question 17

Global vs local processing

specialization in ventral stream

Answer 17

Global letter captures attention

RH better at global level (low spatial freq info; perception of whole)
LH better at local level (high spatial freq; perception of details)
but either can do task

Double disassociation

Local level based on HIGH spatial frequencies
Global level based on LOW spatial frequencies

Question 18

Categorical vs coordinate reps

specialization in dorsal stream

Answer 18

Categorical (LH- abstract, top/bellow, left/right- verbal terms)
-specify the RELATIVE position between objects or between object and viewer

Coordinate (RH- specific metric, relative distance- visual-spatial)
-specify the EXACT positions and distances between objects or between objects and viewers

Functional asymmetry in dorsal pathway