DISSOCIATION OF TARGET SELECTION AND SACCADE PREPARATION USING PRO - AND ANTISACCADE VISUAL SEARCH

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Choice, decision and action investigated with
visually guided saccades. Jeffrey D.
Schall With Leanne Boucher, Gordon Logan Tom
Palmeri
NEUROBIOLOGY OF DECISION-MAKING, CSHL, May 2005
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Definitions

• Choice action in the context of alternatives
  to satisfy a goal, desire or preference
• Action movements with consequences that can be
  explained by referring to preferences, goals and
  beliefs
• Decision deliberation when alternatives are
  vague, payoffs are unclear and habits are reversed

I look forward to playing and hopefully I can
get to that point where I can make that
decision. Michael Jordan on his anticipated
return to professional basketball. Associated
Press, 19 July 2001.
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Further defining decision

• Distinguish two uses of decision
• As characteristic of behavior (e.g., Decision
  Theory)
• But measures of outcome do not specify mechanism
• As process producing behavior
• Mechanism with particular architecture
• Decision as process has two distinct meanings
• Decide to -- Alternative actions (can be
  identified with choosing)
• Decide that -- Alternative categories (not
  identified with choosing)

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Necessity of formal linking propositions

• The properties of neurons do not reveal function
  
• Formal (computational) theories of performance
  explain function
• But distinct models cannot be distinguished from
  behavior testing, e.g., diffusion or race
• Properties of neurons might provide constraints
  to distinguish between models
• if and only if the neural activity measured is
  the instantiation of the cognitive process in
  question, which constitutes a linking proposition

Teller DY. 1984. Vision Research
241233-1246 Schall JD. 2004. Ann Rev Psychol
5523-50
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Linking propositions for decision making
Hanes Schall (1996) described neural activity
that looked like an accumulator.
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Linking propositions for decision making
RT Decision time Residual time Residual time
Encoding time Preparation time
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Countermanding task
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Countermanding performance
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Countermanding paradigm Race model
GO
GO
STOP
Logan, G.D. Cowan, W.B. (1984) On the ability
to inhibit thought and action A theory of an act
of control. Psychological Review 91295-327.
Hanes DP and Schall JD (1995) Countermanding
saccades in macaque.Visual Neuroscience 12929-937
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Saccades are produced by a distributed network
Munoz DP, Schall JD (2003) Concurrent distributed
control of saccade initiation in the frontal eye
field and superior colliculus. In The Oculomotor
System New Approaches for Studying Sensorimotor
Integration. Edited by WC Hall, AK Moschovakis.
CRC Press, Boca Raton, FL. Pages 55-82.
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Countermanding physiology
STOP
SSRT
STOP
SSRT
No stop trials
No stop trials
Non-canceled trials
Canceled trials
Hanes, D.P., W.F. Patterson, J.D. Schall (1998)
The role of frontal eye field in countermanding
saccades Visual, movement and fixation activity.
Journal of Neurophysiology 79817-834.
Pare M, Hanes DP (2003) Controlled movement
processing superior colliculus activity
associated with countermanded saccades. Journal
of Neuroscience 236480-6489.
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Mapping the race model onto neural processes
1 - The race model of countermanding performance
assumes that the GO and the STOP processes have
independent finish times (Logan Cowan, 1984).
2 Saccades are produced by a network of
interacting neurons.
Paradox How can a network of interacting
neurons produce behavior that looks like the
outcome of race between independent processes?
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Mapping the race model onto neural processes
Explore properties of simple network of GO and
STOP units.
Constrained by the characteristics of
countermanding behavior and by the form of
activation of neurons
L.Boucher, G.D.Logan, T.J.Palmeri, J.D.Schall. An
interactive race model of countermanding
saccades. Program No. 72.10. 2003 Abstract
Viewer/Itinerary Planner.
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Complete independence
STOP
GO
L.Boucher, G.D.Logan, T.J.Palmeri, J.D.Schall. An
interactive race model of countermanding
saccades. Program No. 72.10. 2003 Abstract
Viewer/Itinerary Planner.
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Complete independence
STOP
GO
Reproduces countermanding behavior
L.Boucher, G.D.Logan, T.J.Palmeri, J.D.Schall. An
interactive race model of countermanding
saccades. Program No. 72.10. 2003 Abstract
Viewer/Itinerary Planner.
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Complete independence
STOP
GO
but does not produce correct activations.
The GO process is never interrupted!
L.Boucher, G.D.Logan, T.J.Palmeri, J.D.Schall. An
interactive race model of countermanding
saccades. Program No. 72.10. 2003 Abstract
Viewer/Itinerary Planner.
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Key insight the inhibition of STOP on GO cannot
be uniform and instantaneous it must be late and
potent
STOP
GO
?t
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Delayed potent STOP
STOP
GO
?t
STOP
SSRT
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Delayed potent STOP
STOP
GO
Reproduces countermanding behavior
?t
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Delayed potent STOP
STOP
GO
and reproduces neural activation
?t
The GO process is not modulated in non-canceled
trials
The GO process is modulated within SSRT in
canceled trials
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Specific conclusions
Countermanding performance is produced by pool of
neurons the prepare movements (GO process) and
pool of neurons that interrupt preparation (STOP
process). The STOP process is composed of an
early (afferent) stochastic stage and a late
potent interruption stage.
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General conclusions
Redundant but distinct models cannot be
distinguished based on behavior data (Moore,
1956, in Automata Studies, ed. CE Shannon, J
McCarthy. Princeton Univ. Press) Properties of
neurons can distinguish between alternative
architectures but only if neurons instantiate
the processes in question. GO process identified
with pool of movement neurons. STOP process
identified with pool of movement inhibition
neurons.
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General conclusions continued
Stochastic response preparation process necessary
to explain countermanding performance. If so,
response preparation must be more or less
stochastic during all tasks. Therefore, the
proper form of response preparation variability
must be incorporated into sequential sampling
models of perceptual or memory decisions. This
and much other evidence indicates that RT is the
expression of at least two distinct but not
necessarily discrete stages of processing
encodingcategorization (decide that) and
response preparation (decide to).
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General conclusions continued
"Since we cannot break up the reaction into
successive acts and obtain the time of each act,
of what use is the reaction time?" R.S.
Woodworth (1938) in Experimental Psychology
quoted in Luce (1986)
It is possible now to determine the duration of
intermediate stages with invasive measures of
neural states. However, this depends on proper
linking propositions. Information about process
durations and transitions is necessary to
elucidate how stimulus ambiguity, prior
probability and reward history influence choices.
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An empirical basis for distinguishing between
choosing and deciding
It is deciding when anterior cingulate cortex is
engaged.
Rees et al. Nature Neuroscience 3, 716 - 723
(2000)
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Fixation cell activity from FEF SC
SSRT
Stop Signal
SSRT
Stop Signal
Activation (Spikes/sec)
100
400
200
0
400
200
0
Time from target (ms)
Time from target (ms)
Hanes, D.P., W.F. Patterson, J.D. Schall (1998)
The role of frontal eye field in countermanding
saccades Visual, movement and fixation activity.
Journal of Neurophysiology 79817-834.
Pare M, Hanes DP (2003) Controlled movement
processing superior colliculus activity
associated with countermanded saccades. Journal
of Neuroscience 236480-6489.