Problem 6 Flashcards
Adaptive decision making
Involves selecting the most valuable option
–> typically by taking an action, which ofc involves value comparison
OFC
Plays a critical role in value based choices between stimuli, but not actions
–> learning stimulus-value
dACC
Plays a critical role in value based choices between actions
–> learning action-value
- WHICH outcome is expected from a particular action ?
- Is this action WORTH executing, based on the value + cost of the outcome
THUS: lesions will lead to reward-guided action selection deficits
What do the findings that action value vs stimulus value learning is controlled by different brain regions mean for decision making processes in general ?
That stimulus-values represented in the OFC are not necessary for generating action-values in the dACC and vice versa
–> while they may interact, there is no link between these forms of adaptive decision making choices
It is argued that the ACC, like the lateral PFC is involve in executive control.
How profound is that involvement though?
ACC is only activated when there is
- change in response
- conflict between possible responses
BUT: not active when only the stimulus selection is at issue
–> lesions here, thus only cause little disruption of WM
What do patients with ACC lesions show ?
What is consequently the main role of the ACC ?
- Inability to correct ones own mistakes/ learning from them
- ACC is involved in performance monitoring for mistakes
Event related negativity
ERN
- Can be recorded after an erroneous response occurred
- -> immediate corrective signal - Reflects the importance a subject places on avoiding mistakes
–> ERN increases with emphasized accuracy, thus has an evaluative role
THUS: since it predicts the nonoccurrence of a reward, there is decreased phasic dopamine release
Activity of the ACC is associated with…
- Reductions in reward
- Error detection
–> lesions lead to disrupted reward-related action selection
Why does response conflict elicit SFG activity even when it does not lead to an error response ?
Activation of the SFG shows how the need for cognitive control is detected before mistakes are made
Activity of the caudal Superior frontal gyrus (cSFG) is associated with …
- Changing response sets
- Response conflict
–> thus representations of more than one response are co-activated
BUT: must not necessary lead to an error response
The ACC works in conjunction with another brain substrate to mediate cost benefit decisions.
Name the brain region.
Ventral striatum
–> involved in reward processing
What neural structures generate ERN signals ?
dACC, but also surrounding pMFC and
- rACC
- dlPFC + vlPFC
- lateral parietal cortex
BUT: dACC/pMFC are principal generators of the ERN signal
–> thus key part of error-processing system
What happens if a person makes an error without being aware of it ?
How does it show in ERN signaling ?
There is no ERN signal
–> subjects will have lower expectations for a correct response to degraded stimuli, thus personal investment is lower
AND: ERN signal reflects the effort a person puts in responding correctly
Error positivity
Pe
Generated by parietal cortex
–> follows the ERN
How can obsessive compulsive disorder be related to ERN ?
OCD patients have a defect in their error monitoring systems
–> confirmed by larger ERNs in OCD patients
THUS: abnormalities in performance monitoring may establish a vulnerability for OCD
Can error processing be segregated functionally ?
Yes, it can be segregated into cognitive vs emotional activity in the ACC/pMFC
- cognitive
- -> dACC - emotional processing of error response
- -> rACC
BECAUSE: rACC exchanges more projections to limbic regions like amygdala
What is cognitive conflict ?
Cognitive conflict occurs when a strong response tendency competes with + must be overcome by the intended response
ex.: saying the front color of a word which itself depicts a different color, such as RED printed in green letters
–> stroop effect
Conflict theory
Suggests that the
- dACC monitors for the presence of cognitive conflict
- dACC passes a signal to the lateral PFC to increase cogntive control when conflict is high
–> errors generate a high conflict when the stronger but UNDESIRED response reaches a sufficient threshold to command an actual response
Fucntional imaging studies attempted to separate conflict processing + error processing.
What are the findings?
- Conflict-related foci
- -> Brodmann areas 6/8, thus pre-SMA - Error-related foci
- -> Brodmann ares 24/32, thus dACC
How are the DA neurons inhibited when expected rewards do not occur ?
VTA + SN receive inhibitory neurons from the habenula
–> these in turn inhibit DA neurons
THUS: increased habenula activity for error occurrence
Habenula/
Habenular complex
Refers to a structure of the dorsal medial thalamus that inhibits the midbrain nuclei
–> lesions lead to increased DA in NAC, striatum + PFC
Results from the Ullsperger study showed that the ventral striatum ONLY activated when positive feedback occurs.
In contrast, what did they find about the role of the habenular complex ?
Habenular complex is most active, thus inhibits DA release, when
- an error is made
- negative feedback received
- Correct responses were NOT followed by positive feedback
What is the inhibitory function of the habenular complex based on ?
On its integration of reward expectancy + the actual occurrence of reward or punishment
Rostral cingulate motor area (rCMA)
Decreased DA release results in higher activity here, thus involved in
neurons only respond when reduced reward leads to a change in behavior
–> reacts to errors that are followed by negative feedback
pre-SMA
–> part of SFG
Is activated by errors in general, even without negative feedback
–> thus preferentially engaged by response conflict or uncertainty
