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Decision mechanisms for attention

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Title: Decision mechanisms for attention


1
Decision mechanisms for attention Jacqueline
Gottlieb Department of Neuroscience The Kavli
Institute for Brain Research Columbia University
Simon Kelly
Himanshu Mhatre
Nico Foley
2
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?
3
Target selection
LIP
FEF
MT
V4
V1
SC
Spatial receptive field.
Itti and Koch, 2000
Little feature selectivity.
How does this signal arise?
Selective responses to stimuli that are likely to
attract attention.
Why 2 areas?
4
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)
5
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
6
What do we get from observing a stimulus?
Pleasure (or displeasure)
Information
7
Pavlovian learning
Positive
Negative
Attention is independent of valence (salience)
Attention depends on valence (emotional effect)
OR
8
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
9
A saccade target appears
Peck, Jangraw et al., 2009
10
Impairment at the RC- location
RC
RC-
More errors, lower reward
Peck, Jangraw et al., 2009
11
Increases with training!
RC-
RC
Incongruent
Congruent
Incongruent
Congruent
Peck, Jangraw et al, 2009
12
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
13
Reducing uncertainty
2 antagonistic systems?
14
Two attentional systems?
Selects uncertain cues
Selects reliable cues
Amygdala, substantia nigra, parietal lobe
Frontal lobe
LIP?
FEF?
Based on experiments in rats. Very different
definition of attention.
Still, could it be true in monkeys?
15
Two categories of salience?
Not purely sensory, but obligatory
Novelty, uncertainty, surprise, emotion (?)
Reward, goals (?)
16
Parietal neurons are sensitive to uncertainty
50 reward
Dual influence of uncertainty and reward
100 reward (RC)
0 reward (RC-)
17
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)
18
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?
19
The value of information
Black cue 100 validity
reward
Green cue 80 validity
Blue cue 55 validity
3 Informative cues with different validities
reward
20
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 gtgt yellow gtgt 100
Green gtgt red gtgt 80
Blue gtgt cyan gtgt 55
E(R)
Redundant
Informative
Consistent pairing matched for E(R) with
informative cues
Informative cue increases future reward
21
Reward modulates only the informative cues
Informative
Uninformative
100
100
80
80
Cue on
Go
77 significant
14 significant
55
55
22
Is it D(E(R))?
Redundant
Informative
D(E(R))
0.22
0.00
p(R)1.0
fixation
E(R)1.0
E(R)1.0
0.02
0.00
p(R)0.8
E(R)0.8
E(R)0.8
E(R)0.78
0.00
-0.23
p(R)0.55
E(R)0.55
E(R)0.55
23
Possibly D(E(R))
100
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.
80
Uninformative
55
Normalized firing rate
NOT entropy! 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!
0.000 bits
0.072 bits
DE(R)
24
Attention is the system that satisfies the
brains 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)
25
Eyes are windows to the soul.
Lets give them due respect!
26
Identifying predictors is fiendishly difficult.
Pavlovian mechanisms may provide a fast (and
fallible) heuristic.
27
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.
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