Decision-making

Question 1

Define a decision.

Answer 1

Commitment to a proposition. The process of selecting an action based on evidence, prior knowledge and/or belief.

Question 2

What did Shall, 2005 say about decision-making?

Answer 2

‘Decision refers to the deliberation preceding an action (as opposed to choice)’.

Question 3

What is the general sequence of events involved in decision-making?

Answer 3

Sensory input, decision making, motor output.

Question 4

What are random decisions associated with in terms of neuronal activity?

Answer 4

Consistent bias in the activity of the relevant sensory neurons.

Basically what the neurons are normally doing, go with that.

Question 5

Define motion coherence.

Answer 5

When objects are all moving together in the same direction at the same speed.

Question 6

As motion coherence increases, what happens to reaction time? Why?

Answer 6

It decreases. It takes time for our brains to accumulate evidence to make a decision. It is easier to do this if all the objects are moving coherently.

Question 7

What are the 2 main brain areas associated with decision-making?

Answer 7

1. The middle temporal area (area MT)

2. The lateral intraparietal area (area LIP)

Question 8

What does the area LIP do?

Answer 8

Sensorimotor integration.

Question 9

Harder decisions are faster and more accurate. True or false?

Answer 9

False - harder decisions take longer as you must accumulate more evidence, which generally makes them less accurate.

Question 10

How do we know that area LIP neurons are not purely sensory?

Answer 10

Activity builds slowly, and even after the stimulus is removed the activity continues. This activity can be used to predict the time and direction of a subsequent movement, even when sensory information is no longer available.

Question 11

How do we know that area LIP neurons are not purely motor? Give 2 reasons.

Answer 11

1. Choice-dependent differences in activity emerge early in the response. If they were purely motor neurons there would be only one outcome.
2. The rate of response build-up depends on the strength of the stimulus.

Question 12

Neuronal activity in the prefrontal cortex is associated with confidence in one’s decision. How was this shown in experiments with monkeys by Kiani and Shadlen in 2009?

Answer 12

Monkey gets no reward for incorrect decision.

Monkey gets reward for correct decision.

Monkey gets smaller reward for choosing a ‘safe option’.

Thus can assume if they don’t go for the safe option, they are confident with their decision.

Was found that there was increased activity in the prefrontal cortex when the monkey did not choose the safe option.

Question 13

Why does decision-making serve as a good model for higher brain function?

Answer 13

Decisions take time.

Question 14

We can more easily understand decision making for manipulating the difficulty of the decision. How might this be achieved?

Answer 14

Adding noise to a stimulus, making it less easy to understand.

Question 15

Evidence used to make decisions is accumulated over time. True or false?

Answer 15

True, particularly for humans and other higher animals.

Question 16

What does the ‘accumulation of evidence model’ indicate about safe, slow decisions?

Answer 16

A higher threshold value of evidence accumulation is met.

Question 17

Under the ‘accumulation of evidence model’ risky, faster decisions are always made at a low threshold value of accumulated evidence. True or false?

Answer 17

False. Fast, risky decisions are often made with low evidence. However they can also be made when there is consistent bias in neuronal activity.

Question 18

Decisions are context dependent. True or false?

Answer 18

True.

Question 19

It is thought that decision-making involves competition between separate reflexes. True or false?

Answer 19

False: it is unclear whether decision-making involves competition between reflexes or an evolving state of a singular neuronal network.