Neuroscience - Neurobiology of Decision-Making

what are decisions a link between?

memory and future actions

describe the 6 stages of the prediction-choice-outcome loop

1. goal

2. prediction

3. decision

4. action

5. outcome

6. monitoring: calculate prediction error to make accurate future predictions

what are 3 features of decision making?

1. avoid harm

2. minimise costs of time, effort and missed opportunities

3. maximise rewards

what do we rely on to make predictions on possible outcomes of decisions?

memory and context

what are some factors to consider before making a decision?

1. difficulty of the action

2. probability of success/failure

3. value of reward

4. missed opportunities

3 biases in DM?

1. choosing default option for ease

2. choosing certain gains over gambles

3. temporal discounting

what is temporal discounting?

choosing lower immediate rewards over higher future rewards - immediate gratification

what are the 2 levels of DM?

1. simple perceptual decisions

2. complex decisions - several factors to be considered

what is evidence accumulation?

evidence is created for each possible outcome and when a threshold is reached the decision is by whichever option first reached it

3 stages of perceptual decision making?

1. detection of sensory evidence

2. integration of evidence over time - can be noisy

3. checking if threshold has been reached

in a perceptual decision-making task, what happens when the threshold is/is not reached?

is reached - elicit decision made

is not reached - accumulate more evidence

where does evidence accumulation happen?

• brain areas for relevant encoding features, e.g., MT/V5 if motion is relevant.

• parietal/dorsal PFC.

• sensorimotor areas

which 2 models show that memory must be durable and flexible for evidence accumulation to occur?

1. homogeneous - all relevant neurons become active at the same time

2. heterogeneous - some neurons activate earlier and pass on activity to slower neurons, causing a wave of activity

what are mental maps?

DM processes rely on internal models of the current task; experiences need to be organised into internal models/maps

what did Tolman find?

rats make mental maps when they encode transitive relations of different locations in a maze, and use this to build up a mental representation

how can mental maps be applied to non-spatial tasks?

applicable to problem-solving, e.g., making dinner = goal → anticipation of outcome → what you value more → decision.

then sequence series for preparing the food → mental map formation through new experiences.

what’s the role of the hippocampus in DM?

• retrieval of LTM content

• new experiences need neuronal activity in hippocampus to be stored in LTM

• when you later make a similar decision, LTM will be re-activated

what did Schuck et al find?

• found 2 areas in the medial frontal cortex that responded to colour patterns.

• researchers could tell that ppts would switch to using colour as their strategy before they even did it.

• based on learned association

what are ‘state spaces’?

kaplan - different cognitive maps for different cognitive tasks

what’s a hidden state?

the point we’re at in solving a complex decision task

what is mental exploration?

evaluation of potential outcomes for different choices

which brain areas help us decide subjective value of a choice/option?

orbitofrontal, medial and ventral areas, as well as deeper brain structures like the thalamus and striatum

what updates the value of an option/choice based on current goals/context?

ventro-medial prefrontal cortex (vmPFC) and ventral striatum

what happens to DM processes in patients with lesions in the OFC-vmPFC?

impaired in simple preference judgements in value-based decision tasks

what happens to behaviour in DM when people suffer vmPFC lesions?

they show inconsistent preferences and a deficient sense of guilt

what were the results of Kalat’s trust game?

people with vmPFC damage do not trust as much, they will give less money to the other person and also won’t return as much if it’s given to them.

what brain structure is associated with exploratory behaviour in DM?

frontal pole

what brain structure is involved in DM but not in value-based paradigms?

lateral PFC

what did carland say people do when making decisions?

maximise reward rate

what makes it harder to determine which choice is the best in a decision?

more options

what is the formula for reward rate maximisation?

(utility x success probability) - cost / deliberation time + handling time + ITI

what does handling time refer to in the formula?

the temporal discounting factor

what does ITI refer to in the formula?

inter-trial interval - how long to wait before the next go

what is the urgency signal?

it pushes the accumulated evidence quicker to make a decision faster, reducing deliberation time

what brain structure controls the urgency signal?

the basal ganglia projections to cognitive/sensorimotor areas

what modulates the urgency signal?

task context - easier decisions means the US acts quicker, more difficult decisions means the US is weaker, as more time should be spent on deciding