cgs 2301 - hemispheres

lateralization

the idea that some brain functions are specialized to either the left or ride side of the brain

left brain

logical, calculating, lingustic

right brain

emotional, holistic, intuitive

damage to left hemisphere?

pessimistic, overly emotional, overly noticing even nonserious problems

damage to right hemisphere?

optimistic, unemotional, anosognosia (oblivious to serious injury/illness/disability)

lateralized left brain function

language, broca and wernicke’s areas

lateralized right brain function

faces, visual motor tasks

contralateral

• left hemisphere → right side of body, right visual field

• right hemisphere → left side of body, left visual field

localization

specific brain regions are responsible for specific functions

evidence of localization (3)

• selective amnesia

• aperceptive amnesia

• associative amnesia

selective anmnesia

selective memory loss, can’t remember certain specific details

aperceptive amnesia

• vision intact

• impaired recognition of shapes/forms

• diffuse and widespread damage

• ex: in the video, the woman can’t mimic the shapes drawn

associative amnesia

• vision intact

• shapes/forms intact

• recognition impaired (perception is correct but deeper association with label is severed)

• scope of deficit varies

• ex: could perfectly mimic drawing but wouldn’t be able to say what it is

localized vs lateralized

contiguous (bordering) area controls the task

dyscalculia

can’t do simple math calculations

alexia

can’t read

note: alexia is caused by brain damage vs dyslexia which is a developmental disorder caused by genetics/environment

agraphia

can’t write

broca’s aphasia

can’t produce language

note: broca sounds like “boca” = mouth in spanish → you can’t produce language w your mouth

wernicke’s aphasia

can’t comprehend language

decussation

crossing of nerve fibers from one side of CNS to other side

areas of decussation (4)

• corpus callosum

• optic chiasm

• super olivary complex

• spinal cord

corpus callosum

• bridge of ~200 mil fibers

• connects left and right hemispheres

• severed in split brain patients

optic chiasm

• vision

• left visual field info → right visual cortex

• right visual field info → left visual cortex

superior olivary complex

• auditory pathways

• a bunch of subcortical areas

• decussation in superior olivary complex after cochlear nucleus (so not complete crossover)

auditory pathway

auditory nerve → cochlear nuclei → superior olivary nucleus → inferior colliculus → medial geniculate nucleus of thalamus → auditory cortex

mnemonic: Manny Is Super Cute (medial → inferior → superior → cochlea) (it’s backwards tho rip)

spinal cord

• pain and temperature

• touch and vibration

• motor output

• multiple points of decussation

what do split brain patients have?

severed corpus callosum

what can a severed corpus callosum tell us?

• verbal, verbal, and tactile info transfer

• emotion

• motor coordination

• how do the hemispheres exist independently?

who conducted the verbal, verbal, and tactile info transfer experiment in split brain patients?

Roger Sperry and Michael Gazzaniga

part 1: patient is shown cup in the right visual field

when asked what they saw, the patient said a cup

part 2: patient was shown a spoon in the left visual field

when asked what they saw, the patient said they didn’t know

part 3: spoon was shown again in the left visual field

• when asked what they saw the patient still didn’t know

• however when asked to find the object they saw from a bag of objects, they picked the spoon

who conducted the emotional info transfer experiment in split brain patients?

• Gazzaniga and LeDoux (1978)

• patient PS

part 1: patient is shown emotionally charged word (ex: DEVIL) to left hemisphere

• when asked if the word was good or bad, the patient said bad

• when asked what the word was, the patient said devil

part 2: patient is shown emotionally charged word (ex: DEVIL) to right hemisphere

• patient said word is bad

• however didn’t know what the word was

motor coordination (1930s)

Kurt Goldstein

alien hand phenomenon

• middle-aged woman with suicidal tendencies

• would try to strangle herself with her left hand.

• would fight off her left hand with her right.

• autopsy revealed CC lesion.

• right hemisphere (more emotional?) tried to commit suicide - left hemisphere not aware of this intention.

implications

• what does this say about the will and self?

• are there two of us?