Stevens, T. & Monsell, S.
School of Psychology. University of Exeter. Exeter, UK.
Imaging studies suggest that the right intraparietal sulcus (rIPS) is activated during advance preparation for a task-switch, but little or no rIPS activation is seen in experiments that do not allow time for preparation. We examined the role of rIPS using TMS with a task-cuing paradigm. The tasks were to classify the colour or the shape of a stimulus with a left or right key press. An auditory task cue preceded the stimulus by an interval of 100 ms (short CSI) or 750 ms (long CSI). In Experiment 1, we applied 3 TMS pulses at 20 Hz over rIPS, or over a control site, from 250 ms before the stimulus onset: i.e. during preparation with a long CSI, or before the cue with a short CSI. When the control site was stimulated, the usual reduction in behavioural switch cost with increasing CSI was observed. Stimulation of rIPS significantly attenuated this reduction. In Experiment 2, TMS applied 300 ms after stimulus onset had no impact on switch costs. This result suggests that rIPS plays a critical role in advance task-set preparation rather than in task-set reconfiguration more generally.