When did the horse cross the road?: sequential effects in the go/no-go variable foreperiod paradigm

Timing is important to everyday functioning; performing the right action at the wrong time can be just as ineffective as performing the wrong action entirely. 'Inhibition' has been propsed to allow us to perform the correct response at the right time, and to stop that response completely if necessary. This thesis focuses on one theory linking inhibition and temporal expectancy, the 'trace-conditioning model' proposed by Los and van den Heuvel (2001). The trace-conditional model posits that imperative time points have associated traces which are reinforced/extinguished by inhibition based on events at that time point. Traces are proposed to explain the asymmetrical sequential foreperiod effect; a prior trial with a long foreperiod slows current short imperative reaction times, while a short imperative in the prior trial does not affect current trial long imperative reaction times. To further elaborate on how traces are controlled, I have performed three behavioural and one transcranial magnetic stimulation (TMS) experiment utilising varieties of the go/no-go variable foreperiod experiment as described by Los (2013). Each behavioural experiment manipulated the foreknowledge of an upcoming event, while the TMS experiment repeated Los’ study with the addition of a single TMS pulse 100ms after the short imperative time. By manipulating the foreknowledge of an upcoming event, I examined how trace-conditioning may interact with explicit information provided by cueing. TMS was applied to determine if corticospinal excitability was affected by prior trial dynamics. The behavioural experiments suggest that, while prior trial response effects were attenuated given response foreknowledge, temporal trace effects were not attenuated unless both response and temporal foreknowledge were provided. TMS results indicate prior trial timing, mediated by the current trial type, affected motor cortex excitability. I argue that these findings indicate a separation between response and temporal traces.