A TMS investigation of the Perruchet effect (2)

In the Perruchet effect a single stimulus (the conditioned stimulus, CS) is paired with a second stimulus (the unconditioned stimulus, US) on half the trials and on the other half the trials the US is not presented. Conditioned responding to the CS is typically found to dissociate from conscious expectancy for the US. The Perruchet effect is hypothesised to develop due to the uncertainty of the situation in this task. To test whether this was true, uncertainty was manipulated by contrasting participants who were presented an entirely predictable sequence of trials against participants who were presented with a random sequence of trials, which promoted uncertainty. In order to study this, transcranial magnetic stimulation (TMS) was applied in this experiment to correlate changes in corticospinal excitability to motor performance and conscious expectancy. This experiment acted as a control experiment for ‘Per_TMS’.