Transcript Document

Inhibitory Pavlovian Conditioning
Stimuli can become conditioned to signal the absence
of a US— such learning is called Inhibitory Conditioning
CS+ = excitatory CS = CS
CS- = inhibitory CS = CS
US
no US
Inhibitory Conditioning only occurs if there is an
excitatory context
Procedures for Inhibitory Conditioning
Conditional (standard)
• On some trials:
CS+ 1 US
On other trials:
CS+/CS- 1 no US
• Whether the CS+ is followed by the US is
conditional on the presence of the CS-.
Explicitly unpaired/Negative contingency
p(US/CS-) < p(US/no CS)
• On some trials:
US alone
On other trials:
CS- alone
• The CS- occurs on different trials than the
US, which is not signalled by a specific
CS+.
Differential procedure
• On some trials:
CS+ 1 US
On other trials:
CS- 1 no US
• The CS- occurs on different trials than the
CS+ and US.
• The background cues provide the excitatory
context
Backward conditioning
US 1 CS
If the US comes on before the CS, then the CS actually
signals the absence of the US
(because the US has already happened).
Trace or Long-Delay conditioning
CS
US
The CS comes on but there is a long interval before the
US is delivered. The CS essentially signals a period when
the US is absent
Measuring Conditioned Inhibition
Once an animal learns that a stimulus signals the absence
of the US, what does it do with this information?
What is the behavior?
With excitatory conditioning, the CS comes to elicit certain
behaviors (i.e., salivation, eyeblink, keypecking)
The identification of a conditioned inhibitory response can
be more difficult
Measuring Conditioned Inhibition
• Directed Behavior Test
• Summation Test
• Retardation of Acquisition Test
Directed Behavior Test
• Sometimes inhibition can be measured
directly by just presenting the CS• but only if conditioned behavior varies
above and below a baseline level (e.g., heart
rate, blood pressure, temperature).
• If CS+/US resulted in increase in behavior,
inhibition would be evident if the behavior
decreased on presentation of CS-.
• Subjects can also approach a CS+ and avoid
a CS-
If the CR is not bidirectional,
Summation (or Compound Stimulus) Test
present the CS- in combination with a new
CS+ that signals the US
conditioned inhibition is indicated if the
CR to CS+ is less when CS- is present
than when CS+ is presented alone.
Summation Test (Cole, Barnet, & Miller, 1997)
Training:
On some trials:
Light
On other trials:
Light + Noise
On yet other trials: Clicker
Shock
No Shock
Shock
Test:
The time it took the rats to complete 5 seconds of
drinking was measured in the presence of:
►the light (conditioned excitor)
►the clicker (conditioned excitor)
►the light + noise (conditioned inhibitor)
►the clicker + noise (conditioned inhibitor)
Results:
Light = conditioned excitor
Clicker = conditioned excitor
Noise = conditioned inhibitor
Clicker
Text p.85
Clicker Clicker
Light
& Noise & Buzzer
Light &
Noise
The important test was Clicker alone vs Clicker + Noise
The rats feared the clicker alone (the rats took longer
to drink), but the presence of the noise (which had
signalled no shock when paired with the light and had
never been paired with the clicker) reduced the fear
elicited by the clicker.
The excitatory effect of the clicker (expect shock;
fear) and the inhibitory effect of the noise (do not
expect shock; reduced fear) summate, and produce a
reduced conditioned fear response.
Retardation-of-Acquisition Test
If the CS- is a conditioned inhibitor for a
particular US, it should:
Be harder than a neutral stimulus to turn into a
conditioned excitor (i.e., a CS+)
That is, learning that the stimulus now
predicts the US should be retarded relative to
controls that did not have the CS previously
conditioned as an inhibitor.
Example of Retardation of Acquisition Test
Conditioned Inhibition Group
On some trials:
Light
On other trials:
Light + Noise
Shock
No Shock
Control Group
Light
On a test:
All groups get
Noise
Shock
Shock
Compare strength of conditioning for
conditioned inhibition and control groups
Conditioned Inhibition Group should
take longer to acquire a CR than the
Control Group.
Lick Suppression Test
Noise was previously
trained as a CI in the
CI group
Mean
Time
Noise previously
received no training in
the Control group
CI
Group
Control
Group
Comparison of CE and CI
Excitation is quicker and easier to get than inhibitory
conditioning
-US is a more salient event than no-US
Extinction is different with CS+ versus CS-can’t simply give CS by itself
What can reduce/extinguish a CI?
-presentation of the US
-even if given randomly; not necessary to have
CS-US pairings
-change from a negative contingency to a ‘0’ contingency
(i.e., no predictive relationship)