Problem 7 Flashcards
Extensionality
Logical consistency across decisions regardless of the manner in which available choices are presented is central to rational decision making
Framing effect
Human choices are sucebtible to the way in which objects are presented/framed
ex.: 75% lean meat is usually preferred over 25% fat meat, even though they are the same, just framed differently.
Martino et al investigated the neurobiological basis of the framing effect by means of fMRI.
Explain their financial decision-making task
Particpants recevied a message saying they would receive 50$
- Subjects had to choose between “sure” option vs “gamble option
- These 2 options were presented in 2 different frames
“sure” option
–> keep 20 out of 50 (Gain frame) vs lose 30 (Loss frame)
“gamble” option
–> 40% of winning vs 60% of losing
What was the result of martinis financial decision making task ?
Participants were
- Loss aversive in the Gain frame
- Risk seeking in the Loss frame
AND: participants seemed highly unaware of the biasing effect
It is hypothesized that the framing effect is driven by an affect heuristic that is underwritten by an emotional system.
How was this confirmed by the financial decision making task ?
There was significant activation in the bilateral amygdala when making decisions based on heuristics
–> thus plays a central role in mediating the frame effect
Imagine you usually take your car to work but today you decide to use the ferry.
Which brain part is activated when we make decisions that are different to our general behavioral tendencies. ?
The ACC
Decreased susceptibility to the framing effect and thus enhanced rationality in decision making is related to which brain region ?
Orbital + medial PFC
–> specifically right OFC + vmPFC
= OMPFC
Elaborate on the role of the amygdala in decision making.
- Value-related precision + learning both negative/positive outcomes
- Mediation of decision biases that come from value-related prediction
- Detection of emotionally relevant info present in contextual + social-emotional cues
AND now added: It processes the type of contextual positive or negative emotional info that is communicated by the frame
What is the role of the OMFC in decision making ?
- Incorporates inputs from the amygdala
- Represents the motivational value of stimuli
=> allows it to integrate + evaluate the incentive value of predicted outcomes to guide future behavior
Lesions to the OMPFC will lead to … ?
Impairments in decision making
–> inability to adapt behavioral strategies according to the consequences of decision
THUS: impulsivity
What is the primary contribution of the amygdala-vmPFC interactions according to Hampton et al ?
Computing expected reward values
–> once established, these are then used to generate behavioral decision
Behavioral choice
Whether to maintain current choices or switch choices
- -> 1. posterolateral OFC
2. Anterior insula
3. ACC
BUT: these signals are reduced in subjects with amygdala lesions
Computation of expected reward value
How much money one expects to earn or lose based on the choice one made
–> done by vmPFC
Value of the outcomes
Actual monetary gain or loss at the end of the decision making process
The production of signals in
- OFC
- ACC
that are related to behavioral choice directly rely on input from …. ?
Amygdala
Reversal learning
Requires a subject to flexibly adjust their behavior when the reward-related contingencies that they have previously learned are reversed
How does the decision making process work in reversal learning ?
- vmPFC computes expected reward
- These signals are used to determine whether to
a) maintain choice
b) switch
On what basis did Hampton et al conclude on the functional significance of the interactions between the amygdala + vmPFC ?
Neural representations on the expected reward in OMPFC/vmPFC depend on input from the amygdala
–> if amygdala is lesioned these signals in mPFC are abnormal
THUS: these signals can no longer be used appropriately to generate behavioral decisions
Location of the amygdala in primates
In anterior temporal lobe towards its medial side
–> almond shaped; part of telencephalon
Positive vs negative reinforcement
Something one works to obtain or avoid
- Misconception:
Amypdala funcitons primarily in negative affect
Amygdala encodes positive values AS OFTEN as negative ones
–> role of the amygdala for positive emotions is at least as important as its role for negative ones
Evidence from rat + money studies that amygdala also encodes postive affect ?
Anticipatory period
–> visual properes of food served as CS predicting its availability
Consummatory period
–> actual access to food
Bilateral lesioned monkeys showed:
- No CS-induced cardiovascular response during anticipator period
- Intact motor response during anticipatory + cardiovascular response during consummatory period
Evidence from human amygdala
Amygdala lesioned Participants vs healthy ones were presented abstract images paired with high media or low probability of food reward
Control
–> preference for images with high reward probability
Lesion
–> no preference displayed
THUS:
- Misconception
Amygdala is critical for reward processing
It is essential for linking objects with the current value of reward
BUT: not for stimulus-reward association per se
–> it provides a value signal, but once it is learned, the amygdala is not needed anymore (=conditional role)
Stimulus reward associations test
Used to assess reward processing
- Object reversal learning
- Win-stay, lose-shift
Object reversal learning
One stimulus is associated with reward, the other not
–> once learned the associations are switched
THUS: one needs to establish + re-establish stimulus reward association
Win-stay, lose-shift
One of 2 stimuli is associated with reward in a single acquisition trial
–> ought to return to stimulus that is associated with the reward + avoid the other one on the next/subsequent trial
How does the amygdala enhance sensory processing in the rhinal cortex ?
If the BLA activity shortly precede the rhinal activity, it is much more correlated
–> increased rhinal cortex transmission leads to enhanced processing + storage of emotions memories
Inferior temporal + Perirhinal cortex
IT/PRh
Sensory areas
–> interaction with frontal cortex is important for the implementation of visually guided movements
Object reversal learning depends on … ?
OFC + rhinal cortex
Name the 2 routes to OFC subserve reward based decisions
- IT/PRh-OFC
- -> processes visually guided info - Amygdala-OFC
- -> processes affective info
