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Foraging, Learning & Genes “Optimal Foraging” Behavior adjusts to environment Diet: Density of preferred prey Risk-sensitivity: (Expected – Required) Intake Seek general predictions/understanding Foraging, Learning & Genes Mechanisms: Intrinsic Constraints on Behavior Genes, nervous system, physiology Diverse among species (vs generality) Initial integration Foraging, Learning & Genes Positive & Negative Reinforcement Reinforcement: value, penalty Currency of fitness (?) Positive: Increases frequency of behavior Negative: Decreases frequency of behavior “Once burned, twice shy” Some people slow to learn from penalty Klein, T.A. et al. (2007) Genetically determined differences in learning from errors. Science 318: 1642-1645. Klein et al. (2007) D2 receptor Protein on surface of human brain cells Activate by neurotransmitter dopamine A1: allelic variant of gene Single base-pair difference from “normal” Klein et al. (2007) A1: allelic variant of gene Reduces D2 density by 30% Linked to “insensitivity of consequences of selfdestructive behavior” (?) Learning from errors Klein et al. (2007) Learning: reinforcement outcomes Performance-monitoring system posterior medial frontal cortex has rostral cingulate zone (RCZ) RCZ: learning form errors Hypothesis: midbrain sends dopamine signal to RCZ Outcome better or worse than expected Enables associative learning Klein et al. (2007) 26 healthy German males 12: A1 allele (reduced D2 density) Chose between pairs of ideograms “Reward or punishment” resulted Functional magnetic resonance imaging RCZ & hippocampus Klein et al. (2007) Learned to choose high Pr[reward] over low Pr Post-test: Avoid lower of low Pr[reward] A1: Same response to positive reinforcement Reduced learning via negative reinforcement Klein et al. (2007) Klein et al. (2007) Klein et al. (2007) See genetic difference associated with difference brain activity & avoidance learning D2 receptor important “reward learning” Genetic variation for choice behavior Risk-sensitivity Reward amounts, scaled to requirements Effects of mean and variance on choice Variance in delay (time) to obtain given reward Different problem; more complex Behavioral Ecology & Microeconomics Intersect Neuroeconomics, Risk & Brain Objective value of reward (x) Subjective value of reward, “utility” (U) U(x) nonlinear; necessary for risk-sensitivity Neuroeconomics, Risk & Brain Neuroeconomics, Risk & Brain McCoy, A.N. & Platt, M.L. 2005. Risk-sensitive neurons in macaque posterior cingulate cortex. Nature Neuroscience 8:1220-1227. Posterior cingulate cortex (CGp) Limbic area: integrates Link reward to with spatial attention (visual) McCoy, A.N. & Platt, M.L. (2005) 2 Adult rhesus macaques Choose between 2 visual targets Fruit juice reward; certain and variable Ecological validity? Recorded activity single neurons in CGp McCoy, A.N. & Platt, M.L. (2005) McCoy, A.N. & Platt, M.L. (2005) Risk-prone for reward amounts, fruit juice U(x) = Mean reward + c Risk Risk: Coefficient of variation McCoy, A.N. & Platt, M.L. (2005) Posterior cingulate neurons Risk-prone Strongest signals when eye movements go to symbol for variable reward