A transcranial magnetic stimulation study on response activation and selection in spatial conflict

Area of Science:

• Cognitive Neuroscience
• Neuroscience
• Experimental Psychology

Background:

• The Simon effect demonstrates how irrelevant spatial information influences response selection in choice reaction tasks.
• Cognitive models propose automatic response activation by spatial cues, interfering with task-controlled response selection.

Purpose of the Study:

• To investigate the role of the dorsal premotor cortex (PMd) in response activation and selection during spatial conflict.
• To determine the temporal dynamics of PMd involvement in the Simon task.

Main Methods:

• Single-pulse transcranial magnetic stimulation (TMS) applied to the bilateral PMd during a Simon task.
• TMS delivered at different stimulus onset asynchronies (SOAs): early (160 ms) and late (220, 250 ms).

Main Results:

• Early TMS (160 ms SOA) suppressed the Simon effect by delaying corresponding trials.
• Late TMS (220, 250 ms SOA) amplified the Simon effect by delaying non-corresponding trials.

Conclusions:

• The dorsal premotor cortex (PMd) is critically involved in both automatic response activation and controlled response selection during spatial conflict.
• The PMd's function shifts temporally, mediating initial spatial cue processing and later response selection processes.