The Reward Factor in the Control of Action:
A Neurophysiological Theory
Johan LauwereynsVictoria University of Wellington,
New Zealand
• How does the brain incorporate reward value in the control of action?
• How does the brain incorporate reward value in the control of action?
• Studied in monkeys using saccadic eye movement tasks
with asymmetrical reward schedule
Biased Saccade Task (BST)
Biased Saccade Task (BST)
Biased Saccade Task (BST)
Biased Saccade Task (BST)
Biased Saccade Task (BST)
Biased Saccade Task (BST)
Biased Saccade Task (BST)
Target position =
unpredictable
Biased Saccade Task (BST)
Reward association = known
Biased Saccade Task (BST)
Biased Saccade Task (BST)
Biased Saccade Task (BST)
Biased Saccade Task (BST)
No escape!
Biased Saccade Task (BST)
Biased Saccade Task (BST)
Biased Saccade Task (BST)
Saccade-related brain areas (macaque monkey)
FEF: frontal eye fieldSEF: supplementary eye fieldLIP: area LIP of parietal cortexCD: caudate nucleusSNr: substantia nigra pars reticulataSC: superior colliculusClbm: cerebellumSG: brainstem saccade generators
DA neuron responds to Reward & Reward Predictor
SignalNoise
Neuronal activity
Noise
Noise
Signal +
Signal +
Improved discrimination
Improved discrimination:Synergistic, multiplicative
• Sensory properties
• Non-linearly enhanced by reward
Response = Input * Reward Gain
Prefrontal cortex, parietal cortex
Superior colliculus
General increase
General increase:Prospective, additive
• Bias in anticipatory activity
• Linearly enhances sensory activity
Response = Input + Reward Bias
Prefrontal cortex, basal ganglia
Superior colliculus
Improved discrimination & General increase
Combination of both mechanisms
• Seen in all areas• Loops between FC, BG and SC• But most common in Superior Colliculus
Response = (Input * Reward Gain) + Reward Bias
On toward the oculomotor plant
Dopamine
DopamineExcitation
DopamineExcitation
Disinhibition
Synergistic,multiplicative
DopamineExcitation
Disinhibition
Prospective, additive
Synergistic,multiplicative
DopamineExcitation
Disinhibition