ORBITOFRONTAL CORTEX NOTES
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Frontal lobe prefrontal cortex
- Dorsolateral
Last to myelinate
Sleep deprivation
- Orbitofrontal
Like dorsolateral, involved in:
Executive functions
Working memory
Cognitive flexibility
Planning
OFC is considered anatomically synonymous with ventromedial cortex
Named by location: above eye orbits
Characteristics
Least explored
Least understood
Sometimes considered part of limbic system
Vary by person
Considerable individuality
Research Difficulties
OFC is close to sinuses (air filled)
Hard to image (MRI, etc)
Orbitofrontal Functions
Cognitive processing
Decision making
Sensory integration
Affective value of reinforcers
Controls
Social adjustment
Responsibility
Mood
Drive
Extensive connections with other brain regions
Reciprocal connections
Ventral & dorsal visual streams
Auditory-spatial processing
phonetic processing (rostral stream)
auditory-spatial processing (caudal stream)
Phonetic processing
All sense modalities
Visual Processing
both ventral & dorsal streams
integration of spatial and object processing
Connect with hippocampus, cingulate and thalamus
Connect with amygdala (emotional center)
Compares expected with actual
Compare expected reward/punishment with actual reward/punishment
Intuitive judgments
Activated during intuitive coherence judgements
Stimulus-outcome associations
Evaluation of behavior
Encode new expectations about punishment and social reprisal
Conflict resolution
Suppressing negative emotions
Approach-avoidance situations
game of chicken
Damage
Inappropriate displays of anger
Inappropriate responses to anger
Defensive, present self in “angelic light“
Lesions – might feel no regret
Damage causes problems with
decision-making
emotion regulation
reward expectation
ADHD
dysfunction of reward circuitry
controlling motivation
reward
impulsivity
Obsessive-Compulsive
executive functioning
impulse control
Addictions
Dopaminergic activation of reward circuits
Compulsive behavior
Increased motivation take drug
Visual discrimination test
DON’T PRESS BUTTON
OFC damage: gotta press!
Reversal learning
Presented pictures A and B
Learn rewarded for picking A
When rule set, switch
Damage to OFC, stay with A
Disinhibited behavior
Excessive swearing
Hypersexuality
Drug, alcohol & tobacco use
Compulsive gambling
Iowa Gambling Task (Bechara & Damásio)
simulation of decision making
4 virtual decks of cards
goal of game is to earn as much money as possible
choose cards by gut reaction
start with $2000 (monopoly $)
don’t know how many cards in deck (it’s virtual)
deck A and B can win $100 reward but large penalty
deck C and D can win $50 reward but small penalty
Good deck = lose slower
Good deck = win some
After 10 cards
healthy show “stress” reaction
GSR if hover over bad deck
damage to amygdala
never develop GSR
After 40-50 cards
healthy stick to the good decks
OFC damage, stick with bad deck
even though know losing money
Probabilistic Learning
must pass up potential large immediate rewards for small longer- warning cues feel like excitement & pleasure?
Poor social interaction
Faux pas Test
1st used with autism
series of vignettes about social occasions
someone said but should not have said; awkward occurrence
Asked to:
Identify what awkward
Identify why awkward
Identify how would have felt
Identify factual control fact
OFC dysfunction
Understand the story
Can’t judge social awkward
Acquired brain injury have these symptoms:
disinhibited behavior
poor social interaction
excessive swearing
hypersexuality
compulsive gambling
drug, alcohol & tobacco use
low empathy
Alzheimer’s disease
Neurofibrer tangles in orbitofrontal area
Endoplasmic reticulum collapse
Tau protein
Tangles in cell bodies
Neuro-plaque
Brain proteins fold abnormally
Amyloid proteins clump together
Cause plaque between neurons
Causes cell loss
Progressive disease
Symptoms get worse with time
Symptoms
Inappropriate emotional R
Decline in intellect
Confused thinking
Memory loss
Repeated questioning
inappropriate emotional R
Violence
Procedural memory last longer than declarative
Can acquire new skills but not remember learning them
Age related
Likelihood increases with age
Strikes 50% of those over 85
Genetic components
Person with Down’s syndrome (3 copies of chromosome 21)
Always acquire Alzheimer’s in middle age
Early onset: chromosome 1 & 14
Late onset: chromosome 10 & 19
Environmental component
50% no relatives with disease
Yoruba people of Nigeria
high-risk genes
low incidence
Maybe due to diet?
low-calorie, low fat, low salt diet
Treatment to improve memory
Increase glucose & insulin
Acetylcholine activator drugs
Diet rich in antioxidants?
Block Aß42 production, inoculate with small amounts of Aß42
Addiction
involved in development of addictive behavior
dopaminergic activation
reward circuits
addicts show deficits in orbitofrontal, striatal, and thalamic regions
cocaine withdrawal shows increased OFC activity, proportional to drug craving
