Decision Making & Reward

Question 1

Decision Factors

Answer 1

Memory, Learning, Stochasticity (Randomness), and Conscious Will

Question 2

Saccadic decision making circuit

Answer 2

MT to LIP
LIP to SC and FEF
FEF to SC
SC to oculomotor neurons

Question 3

MT

Answer 3

• MT/V5 - middle temporal area. -extrastriate visual area
• connections primarily from V1 and V2
• motion sensitive neurons with large receptive fields and preferred velocities (direction and speed)
• neurons encode for instantaneous strength of motion in preferred direction

Question 4

LIP

Answer 4

lateral intraparietal area - receives input from extrastriate cortices, including MT

• major projections to FEF and SC topographically organized code for direction and amplitude of saccades pre-saccadic and peri-saccadic neural activity associated with preferred saccades
• proposed covert psychological processes in sensorimotor processing: attention, motor planning, and decision

Question 5

FEF

Answer 5

Frontal Eye Field - located in posterior to the arcuate sulcus in prefrontal cortex

• motor function: microstimulation elicits saccades, pre- and peri-saccadic activity
• direct innervation of superior colliculus and other brainstem eye movement centers
• visual function: convergence of extrastriate input (MT, LIP, TEO)
• stereotyped activity with saccade to target in response field: initial burst of activity at target onset, then low rate into slow ramping activity to a pre-saccadic burst

Question 6

SC

Answer 6

Superior Colliculus - located in the dorsal midbrain
inputs include retinal, striate and extrastriate, and motor inputs from FEF and LIP
-outputs to multiple brainstem areas involved in oculomotor control
-retinotopic map of visual space organized into response fields, coding for saccade amplitude and direction
-electrical stimulation produces conjugate contralateral saccades

Question 7

perceptual decision making

Answer 7

Newsome used relationship between MT firing rate and coherence to look for evidence of a decision process- found that firing rate and behavioral performance increase with coherence, and concluded that MT was contributing to the decision process and behavior can be predicted by and is a function of the firing rate of MT

Question 8

Integrative post-sensory processing in LIP

Answer 8

1. Gradually rising activity predicts subsequent saccade towards or away from MF
2. Rate of rise of decision-coding activity dependent on strength of motion stimulus
3. At 0% coherence, despite no sensory signal above noise, neural activity is correlated with the monkey’s subsequent choice

Question 9

perceptual decisions

Answer 9

closely related to the processes of recognition – “snap” decisions by which we classify what kind of thing we are seeing (or hearing, or feeling, or …) and then take the appropriate action – If that pedestrian is walking out into the street, I will apply my brakes; if she is standing still, I will continue driving past the crosswalk.

Question 10

value-based decisions

Answer 10

the purview of neuroeconomics – Out of the (seemingly) hundreds of choices on the shelves, which bottle of red wine will I select to purchase and bring home to enjoy with dinner?

Question 11

choice of action selection in decision making

Answer 11

FEF contains neurons that control gaze. Monkeys were placed through a saccade task and showed variability in response times. Faster response times spiked more steeply. Schall found that a certain threshold needs to be reached before a saccade is fired and whichever neuron firing for whichever direction reaches the threshold first determines the saccade

Question 12

two classes of variables in decision making

Answer 12

-Current sensory information
-Stored representation of environmental
contingencies (expected gains/losses)

Question 13

expected utility/gain

Answer 13

Probability of Reinforcement x

Magnitude of Reinforcement

Question 14

reward

Answer 14

• A pleasurable event that follows a specific behavior.
• Can be primary (eg, food, sex) or secondary (eg, money).
• The brain uses rewards to learn, choose and prepare/execute goals.

Question 15

the function of reward

Answer 15

1) Elicit approach behavior (either through innate mechanisms or learning).
2) Increase the frequency and intensity of a behavior that leads to a reward (learning).
3) Induce subjective feelings of pleasure (hedonia) and positive emotional states.

Question 16

Dopamine system anatomy

Answer 16

two main nuclei:
substantia nigra - projects to striatum (involved in motor control)
-ventral tegmental area - projects to prefrontal cortex

Question 17

dopamine and reward

Answer 17

• Many rewards seem to lead to release of dopamine (DA) in the striatum.
• Dopamine is released during basic drives (i.e., hunger, sex).
• DA is released in the rat Nacc right before and during copulation, but not afterwards.
• DA is released in the human caudate nucleus when presented with food stimulation in a food-deprived state.
• DA is released in both NAcc and caudate when participants are playing video games for money.

Question 18

reward prediction error

Answer 18

-Dopamine neurons are active when drop of liquid is delivered outside any behavioral task.
-Earliest predictor of reward signals dopamine response instead of fully predicted reward.
-Dopamine neurons will be depressed at the time of the predicted reward if it fails to occur.
-DA provides an error prediction signal to aid in goal-directed behavior.
DA response = reward occurred - reward predicted