A failure to stop and attention fluctuations: An evoked oscillations study of the stop-signal paradigm

Objective: It is not always clear whether inhibition or attention deficit underlies a failure to stop a prepared motor response. One possible way to approach this question is to resort to measures of evoked oscillations since functional correlates of different frequency oscillations are relatively well understood. Methods: The present study examined event-related oscillations during a stop-signal task in non-clinical adults. In 25% of trials of an auditory discrimination tasks subjects had to refrain from a prepared motor response. Results: In successful stop trials, the Go N2 peaked later and the Stop N2 peaked earlier than in failed stop trials. Relative to successful, failed stop trials were associated with a larger N1-N2 and Go P3, and a smaller Stop P3 in the central and posterior cortical regions. The latter effect was exclusively determined by evoked delta oscillations, whereas all other frequency bands contributed to enhanced responses in failed comparative to successful stop trials. Conclusions: The sum of presented evidence seems to show that success or failure to stop mostly depends on how the subject prepares for the Go and Stop stimuli in advance. If attention is more directed towards the Stop signal, the stopping succeeds, otherwise it fails. Significance: These data may contribute to understanding the cognitive basis of successful and unsuccessful stopping performance. (C) 2007 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved.