Extinction

Extinction

Extinction is the decrease in the amplitude/frequency of a CR as a function on non-reinforced presentations of the CS.
i.e. Unlearning, by producing the CS without the US.

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Examples

Basic Shock Extinction

Phelps et al (2004) showed this by pairing CS+ with shock and CS- without. Then after the association had been learned, presenting the stimulus repeatedly without shock, and measured the SCR + amygdala activity to each CS.

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Spider Extinction

Goosens et al (2007) found results suggesting that amygdala hyperactivity (active in fear processing) could be reduced by exposure therapy; extinguishing the spider-fear relationship.

Three Rs of Extinction

Recovery

Spontaneous Recovery refers to the re-emergence of the associative learning, after extinguishing, when measured after a delay.

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Renewal

Renewal is the recovery of responding (learning) when tested in a context different from the one where extinction occurred.

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Reinstatement

Reinstatement is the recovery of responding when tested (in the same context as extinction occurred), after a non-signalled uS is presented.

Drugs to Enhance Extinction

D-Cyloserine is a partial NMDA receptor agonist that appears to enhance extinction.

Example - Ledgerwood et al

See Ledgerwood, Cranney & Richardson's 2003 experiment below.

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Example - Acrophobia (Fear of Heights)

Ressler et al 2004 found that DCS not only enhances rate of extinction, but appears to reduce occurrences of relapse.

Studying subjects with acrophobia treatment; normally it takes 8 sessions to see improvements, but patients given DCS showed improvements after 2 (the control placebo group did not).

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