41 - Cerebral Cortex

Question 1

Unimodal cortices

Answer 1

Somatosensory/Motor
Visual
Auditory

Question 2

Association Cortex

Answer 2

Combines signals from primary sensory and motor modalities to create emergent psychological properties such as:
Memory
Planning
Spatial Analysis
Language & reading (Language associates arbitrary auditory, visual or tactile symbols with concrete or abstract objects and actions

Question 3

Frontal Lobe Functions

Answer 3

Behavioral Planning
Working Memory
Response Inhibition
Affective Processing (Assigning Value)
Expressive Language

Question 4

Parietal Lobe

Answer 4

Attention
Spatial Location
Body Image (Knowing your limbs are yours)
Transfer of sensory information to the motor system

Question 5

Temporal Lobe

Answer 5

Declarative Memory
Emotional Processing
Receptive Language

Question 6

Functions of the Frontal Association Cortex

Answer 6

Motor planning - The antisaccade task
Speech production
Working memory
Suppression of stimulus-bound behavior
Must be studied with complicated paradigms (beyond simple sensory or motor deficits)
Delayed Response Task = Example

Question 7

Functions of the Prefrontal Cortex

Answer 7

Working memory
Planning of behavior over long periods of tiem
Response inhibition
Complex problem solving, the Wisconsin card sort task
Expressive aspects of language
Associating value

Question 8

Perseveration

Answer 8

Ask for a different tactic, and they can’t change it with the rules!!!!!!!

Question 9

Frontal signs at the bedside

Answer 9

Emergence of primitive reflexes that adults supress (Grasp reflex, suck reflex, root reflex)
Perseveration - Repetition of one complicated behavior rather than changing strategy
Failure to suppress inappropriate responses to sensory stimuli (antisaccade task or blink response to a glabellar tap)

Question 10

Psychiatric aspects of frontal function

Answer 10

Schizophrenia - Depresed frontal function by PET and fMRI criteria. Sometimes do poorly on tasks designed to examine frontal function. Sometimes their first-order relatives do poorly too!!!
Depression - Left frontal strokes correlate with higher frequency of depression than with posterior strokes.

Question 11

Parietal neurons

Answer 11

Respond to SALIENT objects in the visual field, not all objects.
Objects can be made salient from bottom-up or top-down criteria
Respond more intensely to attended objects than to unattended objects

Question 12

Bottom-Up Criteria (involuntary attention)

Answer 12

Big
Bright
Moving
Blood

Question 13

Top-Down Criteria (voluntary attention)

Answer 13

Something that has been made interesting to you.

Question 14

Right Parietal Lesions

Answer 14

Neglect left half of objects and space.

Question 15

Which is worse? Right parietal lesion or left?

Answer 15

“Left parietal patients have more language than space in the left fields” and the right side can compensate for left spacial deficits.

Question 16

Left parietal stroke patient

Answer 16

Spacial deficits, then recovers

Question 17

Right parietal stroke patient

Answer 17

May never recover

Question 18

Paralyze the abducens nerve

Answer 18

The world “jumps to the right” when you try to move your eyes left. There is feedback from motor neurons into the visual system to try and construct spatial relationships in the world

Question 19

Parietal neurons

Answer 19

Remap their receptive fields around the time of every saccade (which is why eye movements don’t bother us)

Question 20

Parietal cortex sends spatially accurate visual information to the premotor cortex, interpreting

Answer 20

Where objects are in space
How big they are
What is their orientation

Question 21

Parietal Signs at the Bedside

Answer 21

Apraxia - Inability to conceptualize or mimic a movement
Constructional Apraxia - They cannot duplicate block designs, and have great difficulty copying drawings.
Optic Ataxia - Difficulty reaching to objects in space or finding them with saccades
Extinction - Neglect of a stimulus in the affected field (visual, tactile or auditory) when presented simultaneously with an equivalent stimulus in the normal field.
Anosognosia - Patients to not recognize contralateral (usually left) limb as a part of their own body
Spatial Distortion
Denial of Illness

Question 22

Cancelation task - Parietal

Answer 22

Start on the right, stop at the midline

Question 23

Temporal Lobe and Limbic Cortex

Answer 23

Hippocampus - Declarative Memory
Amygdala - Emotional processing and fear
Rhinal cortex - Associating motivational value to visual objects
Temporal neocortex - mostly unimodal (auditory and visual)

Question 24

Remove Hippocampus and Amygdala

Answer 24

Can’t remember any fact for more than 45 seconds.
Can learn motor skills that require practice, but never “remembered” practice. Almost like Groundhog day if you play all the characters at once.

This is approximated in Herpes Encephalitis and Korsikoff (thiamine deficiency)

Question 25

Temporal signs at the bedside

Answer 25

Korsakoff’s syndrome - Requires bilateral destruction of the output of the hippocampus - fornix & mammilary body
Temporal deficits are more often behavioral (Difficulty relating to others, sexual problems, emotional problems)
Damaged hippocampus often evokes seizures (auras, visual illusions, produce complex behavioral automatisms)

Question 26

Dominance

Answer 26

The hemisphere with speech (usually the left)

Question 27

Left-dominant subjects

Answer 27

The right hemisphere does more spatial analysis

Question 28

Children who have strokes in their dominant hemisphere before the age of 2

Answer 28

Develop normal speech, but lose some spatial ability as judged by psychometric spatial tasks.

Question 29

Interhemispheric communication

Answer 29

Primary sensory modalities are contralateral.

Information from one hemi-visual field or one side of the body reaches the ipsilateral cortex through the corpus callosum.

Patients with severe epilepsy can be sometimes helped by section of the corpus callosum.

Question 30

Patients with Callosal Section

Answer 30

Entire right hemisphere is disconnected from the speech area
Stimuli in the left visual field and the left side of the body only go to the right hemisphere
Stimuli in the right visual field and the right side of the body only go to the left hemisphere
Left hemisphere doesn’t know about info in the right hemisphere

Question 31

Right hemisphere

Answer 31

Can’t read!!!!!
Flash a word in the left hemisphere, you’ll be affected by it, but you won’t be able to read it. Flash in the right, and you can read it.

Question 32

Alexia without agraphia

Answer 32

Lesion that wipes out left visual field and corpus callosum
All you can see is in the left visual field
That info can’t get to the speech area
Subject can’t read
Can’t name colors
Can MATCH colors
Can name scissors because there is a motor association
Can write
Can’t read what they’ve written