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Decision mechanisms for attention Jacqueline Gottlieb Department of Neuroscience The Kavli Institute for Brain Research Columbia University Simon Kelly Himanshu Mhatre Nico Foley “Attention is a gain modulation of a sensory response, driven by top-down feedback.” The feedback comes from frontal and parietal areas. How is this feedback generated? Target selection FEF LIP MT V4 SC Spatial receptive field. Little feature selectivity. Selective responses to stimuli that are likely to attract attention. V1 Itti and Koch, 2000 How does this signal arise? Why 2 areas? A possible answer: reward High reward target Low reward target Sugrue et al., Science, 2005 Neurons encode “action value” The value is determined by E(R) Limited explanatory power In natural behavior, attention and eye movements are not directly rewarded Attentional decisions are endogenous, even when they support behavioral goals. LIP/FEF neurons encode covertly attended objects. We attend to salient distractors that can only reduce our foreseeable reward. LIP neurons respond strongly to unrewarded distractors. The salience map in LIP selects stimuli, not actions Gottlieb and Balan, TICS ,2010 What do we get from observing a stimulus? Pleasure (or displeasure) Information Pavlovian learning Positive Negative Attention is independent of valence (“salience”) OR Attention depends on valence (emotional effect) Attention depends on stimulus value A cue announces the reward of the trial Good news attract attention RC+ (reward) RC- (no reward) Bad news repel attention Peck, Jangraw et al., 2009 A saccade target appears Peck, Jangraw et al., 2009 Impairment at the RC- location Vertical eye position RC+ RC- More errors, lower reward Horizontal eye position Peck, Jangraw et al., 2009 Increases with training! RCIncongruent Congruent Peck, Jangraw et al, 2009 What do we get from observing a stimulus? Pleasure (or displeasure) Stimulus (Pavlovian) value biases attention Automatic, potentially maladaptive Information Reduction of uncertainty I. Reliable predictors II. Novel or uncertain predictors Reducing uncertainty 2 antagonistic systems? Two attentional systems? Selects reliable cues Frontal lobe FEF? Selects uncertain cues Amygdala, substantia nigra, parietal lobe LIP? Based on experiments in rats. Very different definition of “attention”. Still, could it be true in monkeys? Two categories of salience? Not purely sensory, but obligatory Novelty, uncertainty, surprise, emotion (?) Reward, goals (?) FEF LIP MT V4 V1 SC Parietal neurons are sensitive to uncertainty 50% reward Dual influence of uncertainty and reward Reward probability 100% reward (RC+) 0% 75 Firing rate (sp/s) 50% 100% 0% reward (RC-) 0 0 Cue on 300 Time (ms) 600 900 Parietal neurons are sensitive to novelty Familiar vs. novel patterns Large, early effect of novelty Novel RC+ (100%), RC- (0%) Familiar RC+ (100%), RC- (0%) Reducing uncertainty I. Reliable predictors Predictive stimuli reduce uncertainty Increase the reward of a future action. ! Is it simply expected reward... …or sensitive to new information? The value of information Black cue: 100% validity Green cue: 80% validity reward Blue cue: reward 55% validity 3 Informative cues with different validities Uninformative cues Uninformative stimuli are necessary to obtain the reward. They bring no new information; the monkey has already obtained all the information through the first cue. Black >> yellow >> 100% Green >> Blue >> Informative red >> 80% cyan >> 55% Redundant E(R) Consistent pairing: matched for E(R) with informative cues Reward modulates only the informative cues Informative Normalized response 100% Uninformative 100% 80% 80% Cue on Go 77% significant 55% Cue on Go 14% significant 55% Is it D(E(R))? Informative Redundant D(E(R)) +0.22 fixation E(R)=1.0 +0.02 0.00 p(R)=1.0 E(R)=1.0 0.00 p(R)=0.8 E(R)=0.8 E(R)=0.8 E(R)=0.78 -0.23 E(R)=0.55 0.00 E(R)=0.55 p(R)=0.55 Normalized firing rate 100% 55% 80% Uninformative Possibly D(E(R)) A modulation! Neurons DO respond to the uninformative cues. This may indicate that neurons encode a “visual prediction error” that occurs by default and is modulated by expected reward. NOT entropy! 0.000 bits 0.072 bits DE(R) Uninformative stimuli bring less information but elicit a higher response than the 55% cues. It is not the information per se! It is its utility to the organism. After all, attention MUST be selective! Attention is the system that satisfies the brain’s demand for information. It is controlled by decision variables related to active learning. These variables prioritize *reliable predictors that we can learn from *novel/uncertain/surprising stimuli that we can learn about. Two computations may identify such stimuli: *prediction errors (reward and sensorimotor) *direct Pavlovian associations (fast but fallible) Eyes are windows to the soul. Let’s give them due respect! Identifying predictors is fiendishly difficult. Pavlovian mechanisms may provide a fast (and fallible) heuristic. William James, Lectures to teachers, 1899 To keep [your students] where you have called them, you must make the subject too interesting for them to wander again. And for that there is one prescription […] […]the subject must be made to show new aspects of itself; to prompt new questions; in a word, to change. From an unchanging subject the attention inevitably wanders away.