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Task 5: Success, failure, cerebral cortex (Gazzaniga (Brain areas engaged…
Task 5: Success, failure, cerebral cortex
Lee et al.
utilities (costs and benefits associated with action/choice)
reinforcement learning theory
principle of utility maximization
Brain areas:
LPFC: state representation (maintaining the state representation necessary to identify optimal actions in a given environment - Working Memory)
encode the signals related to the animal’s previous choices and their outcomes in multiple trials (appropriate context)
OFC: value representation (encoding and updating utilities associated wit different sensory stimuli + decision-making in social context - reward expectancy [expected outcome])
Lesions
impair ability to adjust decision making strategies when the previously successful choices are no longer advantageous + to make preference judgments consistently
impair the ability to modify behavior when the outcomes of decisions change dynamically + to assign appropriate values to different objects in the environment
loss of social dominance with increased aversion and reduced aggression in threatening situations
medial PFC (ACC): outcome evaluation (possible actions to obtain a reward and their value [action value functions], also outcome related activity required for the animals to update its decision making strategies after committing an error)
Lesion: become less interested in gathering information from social stimuli, such as faces
Gazzaniga
OFC damage = socially inappropriate behavior, less inhibition, lower tolerance of frustration, increased aggression, immaturity, apathy, emotional coldness, imapired goal-directed behavior, diminished regret
self-knowledge - infromation about our characteristics, desires and thoughts, developed through self-perception
self-referential processing
self-reference effect
self: 1. either extremaly deep processing or posseses separate mnemonic cognitive structure
Default network: alertness when doing nothing
Affective node: VMPFC - core region involved in goal-oriented decision making,
deactivating
when engaged
memory node: posterior cingulate cortex
Brain areas engaged in self-referential processing
OFC: insight into one's behavior: spontaneous accurate self-perceptions and positively biased self-views that o not deviate too far from reality
most ventral part of ACC: distinguishing positive self-relevant info from negative : selectively attending to positive info
VMPFC - more activated when we consider future, less activated when are decisions are more shortsighted.
coup-da coup injury - usually OFC
Rushworth et al.
THEORIES
Theory 1:
BRAIN AREAS
LOFC: value assignment
learning values associated with different goals, and ipdating these value representations on the basis of negative/postive outcomes
VMPFC/mOFC: value expectation
reward representatoins, neurons fire proportional to reward epxectations at the time of decision-making, these value expectations are the inputs to dACC/dmPFC where comparison takes place
ACC: value comparison
prominent inverse value difference signal: BOLD signal increases when the difference between the values of potential choices decreases, output of the ACC/dmPFC comparator that determines the pattern of activity seen in th motor system - the response that is ultimately made
Theory 2:
BRAIN AREAS
vmPFC / mOFC: value comparison
weighting the values of the available stimulus options + choosing the one with the highest subjective value
LOFC: value assignment
learning and updating representations of specific types of reward associated with stimuli, and active when new reward cues are learned (during feedback) or when the value of existing stimulus-reward associations changes (in sensory-specific satiety)
ACC: action value comparison
making decisions about actions that have to be performed in order to get rewards, NOT involved in stimulus selection but in action selection (lesions in lOFC or VMPFC/mOFC disrupt stimulus-reward but not action-reward associations) only midsection engaged in action-outcome association and decision making
cmPFC/mOFC - SELECTING REWARD GOAL
activity: the higher the higher the value. represents values of all options that are being presented. value difference signal is the opposite of the ACC/dmPFC inverse value signal: it increases with difference in value between choices ( consists of competitive, inhibitory interactions between the two pools of neurons so that ultimately only one remains active).
vmPFC/mOFC lesions: do not disrupt the updating of value assignments, but they do disrupt value-guided choice especially when the values of potential choices are close
STUDY
Method: Consistent/inconsistent reward mapping task
Results:
lOFC activity reflected not just error-feedback but any feedback, such as the first occurrence of positive feedback for a particular choice, that allowed updating of the association
feedback activity also differed between Consistent and Inconsistent groups - lOFC was learning expectations about particular types of reward rather than just reward per se
vmPFC/mOFC activity simply reflects reward value; its activity is greater when positive outcomes are received regardless of how informative they are
ACC activity varied between the two groups (greater in Consistent mapping group) as a function of how likely they were to select the correct response
ACC activity probably reflects the strength of reward-guided action selection mechanisms because the groups differ in how much they can use reward to guide response selection (it is possible in the Consistent group but not the Inconsistent group)
O'Doherty et al.
sensory-specific satiety (when a food is eaten to satiety its reward value decreases to zero )
single neurons with olfactory responses in the orbitofrontal cortex decrease their responses to the odor of a food eaten to satiety, but much less to other foods not eaten in the meal
LOFC (through amygdala signaling):
stroing and updating stiulus-reward associations
single OFC cells shown to vary their output intensity with the level of satiety for a particular food - doesn’t affect the representation of pleasantness of other foods in the same area
STUDY:
H: investigate the neural basis of the responses to food odors in humans and where in the brain these responses might be modulated by hunger
METHOD: fMRI used to investigate the changes in the representation of a food-related odor after eating the corresponding food to satiety - vanilla and banana
RESULT
humans BOLD activity in the (lateral) orbitofrontal cortex decreases for the odor of a food after having eaten it to satiety, whereas no such decrease is observed for the odor of the food not eaten
decrease of BOLD activity with satiety was also observed in amygdala in some participants - affective value of food
orbito-frontal cortex may thus represent the reward value and affective aspects of olfactory stimuli