Lecture 9: neruobiology of simple decisions

Question 1

What model makes SPRT more relevant to cog psych?

Answer 1

Drift diffusion model (DDM)

Question 2

Describe the drift diffusion model

Answer 2

Beginning with starting point and continuoysly accumulate evidence over time until a criterion is reached

Question 3

DDM as a process model of decision making

Answer 3

the accumulated evidence at a time.

• Drift: mean direction of evidence
• diffusion: time it takes to reach one criterion

Question 4

DDM - model component 1

Answer 4

separation of decision criterion:

• distance/seperation between binary decision
• amount of evidence needed
• speed accuracy trade off

Question 5

DDM - model component 2

Answer 5

drift rate:

• average speed of accumulation
• represetns quality of info (signal strength)
• if theres low amount of evidence, takes long time to get to the criteria

Question 6

DDM - Model component 3

Answer 6

starting point

- starting point not always in the middle of the two choices - could be bias

Question 7

DDM - model component 4

Answer 7

Non decision time, other stages like detection and execution - RT = decision time and non decision time

Question 8

Does accumulated framework actually work? Study

Answer 8

Zhang and Rowe 2014 - Tested using random dot motion and RT in detection coherent motion direction: when asked to be faster, there was a cost of accuracy (speed-accuracy trade off) - links to the separation component of DDM

Question 9

Experiment: effects of alcohol

Answer 9

Van Ravenzwaajj 2012
P conducted random-dot stimulation and completed with alcohol (moderate and high), placebo
- Drift rate decreases more alcohol
Non decision time increases with alcohol

Question 10

where is the accumulated evidence encoded?

Answer 10

Process random dot in the MT/V5 areas as MT neuronal activity is selective to directed motion

Question 11

where is the encoding of accumulated evidence (predictions): if there are sections of brain responsible for accumulating evidence:

Answer 11

• should see activity of neurone increase/decrease over time
• stronger evidence = faster changes
  activity terminates at the same level

Question 12

Evidence to support the neurological basis of DDM (where evidence encoded)

Answer 12

Gold and shadlen (2007) used monkeys and random dot patterns varying the %, Found that MT neruones signal evidence and LIP neruones accumulate evidence over time. - can go more in-depth on the word doc.

Question 13

Reserach: Is LIP the only area that accumulates evidence?

Answer 13

Kim and Shadlen 1999- similar patterns also found in neurones in dorsolateral prefrontal cortex (DLPFC)