Transcript Inhibition - University of Colorado Boulder

Inhibition
Chris Jung
Department of Integrative Physiology
09/23/08
Outline
• Prefrontal Neurons Coding Suppression of
Specific Saccades
– Hasegawa RP, Peterson BW, and Goldberg ME
• The role of inhibitory control in forgetting
unwanted memories: A consideration of three
methods.
– Anderson MC
• In Opposition of Inhibition
– MacLeod CM, Dodd MD, Sheard ED, Wilson DE, and
Bibi U
Prefrontal Neurons Coding
Suppression of Specific Saccades
Hasegawa, R.P., Peterson, B.W., &
Goldberg, M.E. (2004).
Neuron, 43, 415-425.
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Introduction
Methods
Results
Conclusions
Introduction
• Monkey and humans that do not avoid
looking at something can be seen as
socially offensive, unacceptable.
Introduction
• Eye fixation is an active process
• Two mechanisms have been proposed:
– An inhibition of the saccadic system by the fixation
system
• When fixation occurs, the threshold for evoking saccades
increases by electrical stimulation from the frontal eye field
(FEF) and the superior colliculus, which are apart of the
fixation system
– Some neurons of the FEF are activated if a stimulus
is present to cancel the saccade such as in a “go/no
go task”
Methods
• Caudal part of dorsolateral prefrontal
cortex
• Match/Non Match Task
Figure 1
Sample Period:
3 Different Responses
• Look neurons
– Enhanced
response if the
monkey knew a
priori of a saccade
target
– 10% of samples
Sample Period:
3 Different Responses
• Don’t look neurons
– Enhanced
response if the
monkey knew a
priori of a nonsaccade target, or
to avoid looking at
the original
stimulus
– 10% of sample
Sample Period:
3 Different Responses
• Pure visual
neurons
– No difference
between tasks
– 80% of sample
Delay Period:
3 Different Responses
• Look neurons 53%
– Greater activity if the stimulus was to saccade
to the original sample stimulus
• Don’t look neurons 19%
– Greater response if the stimulus was to not
look where the sample stimulus was
• Memory neurons 28%
– Responded equally to both stimuli
– Believed to be working memory
Conclusions
• The authors report to have located
neurons that help to plan a behavior or
suppress it, whether immediately or during
the delay.
• Temporal progression
– Neurons often switched functions during the
different phases of the test
The role of inhibitory control in forgetting
unwanted memories: A consideration of
three methods
Anderson, M.C. (2005).
In C. MacLeod & B. Uttl (Eds.) Dynamic Cognitive
Processes (pp. 159-190). Tokyo: Springer-Verlag.
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Central claim
Retrieval-induced forgetting
Directed forgetting
Conlusions
Central claim:
• Humans can control
memory by
overriding prepotent
responses to
unwanted memories
Figure 1
Within-Category Retrieval-Induced
Forgetting Study
Figure 2
Retrieval-Induced Forgetting
• Inhibition or response competition theory of
interference?
• Response competition theory of interference
– Target will suffer because increased competition
from the alternative response is strengthened
– Practiced items become so strongly linked to the
practice cue that they block other examples
Retrieval-Induced Forgetting
• Inhibition or response competition theory of
interference?
• Inhibition
– Recall specific
• Retrieval practice impairs the delayed recall of
competing items
– Cue independence
• Retrieval induced forgetting when novel cues are used
Directed Forgetting
Roach--Ordeal
Directed Forgetting
• Dorsolateral prefrontal cortex
• Lateral premotor cortex
Conclusions
• Controlled inhibition may be recruited for
our goals, regardless if the goals are to
forget (Flexible inhibition hypothesis)
• Can help to explain the directed forgetting
and retrieval induced forgetting
In Opposition of Inhibition
MacLeod, C. M., Dodd, M. D., Sheard, E. D.,
Wilson, D. E., & Bibi, U. (2003).
In B. H. Ross (Ed.), The Psychology of Learning
and Motivation, Vol. 43 (pp. 163-214). San
Diego, CA: Academic Press.
• Problem
• Examples
• Proposed Solution
The Main Problem:
“…the concept of inhibition at the cognitive
level cannot derive directly from the
concept of inhibition at the neural level.”
• The term “inhibition” is too flexible of a
term
Negative Priming
• They report:
– No conclusive evidence that inhibition can
explain negative priming.
RED
GREEN
• Automatic memory retrieval
– If there is disagreement between the task at
hand and a recent memory, this will take
longer because you need to resolve the
conflict
Inhibition of Return
Inhibition of Return
Inhibition of Return
• Inhibition of Return
– Past researchers have concluded that there is
an inhibitory mechanism to look towards the
area of a stimuli that was already presented
• Attentional Momentum Hypothesis
– MacLeod et al. believe that attention can be
more easily and faster oriented in a direction
of a location in which it already has been
rather than shifting to another location
• Inhibition is too broad of a term
• The terms “interference”, “selective rehearsal”
should be used instead depending on the task
• Inhibition has been labeled as below baseline
performance.
• For a decrement in baseline performance, the
term “cost” should be used.
• For an increment in baseline performance, the
term “benefit” should be used.
• Two mechanisms that are inhibition free:
– Automatic memory retrieval
• If there is disagreement between the task at hand
and a recent memory
– Conflict resolution