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This Article Full Text Full Text (PDF) All Versions of this Article: 101/5/2649    most recent 91121.2008v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Meftah, E.-M. Articles by Chapman, C. E. Search for Related Content PubMed PubMed Citation Articles by Meftah, E.-M. Articles by Chapman, C. E.

Instructed Delay Discharge in Primary and Secondary Somatosensory Cortex Within the Context of a Selective Attention Task

¹Groupe de recherche sur le système nerveux central, Département de physiologie and ²École de réadaptation, Faculté de médecine, Université de Montréal, Montreal, Quebec, Canada

Submitted 7 October 2008; accepted in final form 10 February 2009

The neuronal mechanisms that contribute to tactile perception were studied using single-unit recordings from the cutaneous hand representation of primate primary (S1) and secondary (S2) somatosensory cortex. This study followed up on our recent observation that S1 and S2 neurons developed a sustained change in discharge during the instruction period of a directed-attention task. We determined the extent to which the symbolic light cues, which signaled the modality (tactile, visual) to attend and discriminate, elicited changes in discharge rate during the instructed delay (ID) period of the attention task and the functional importance of this discharge. ID responses, consisting of a sustained increase or decrease in discharge during the 2-s instruction period, were present in about 40% of the neurons in S1 and S2. ID responses in both cortical regions were very similar in most respects (frequency, sign, latency, amplitude), suggesting a common source. A major difference, however, was related to attentional modulation during the ID period: attentional influences were almost entirely restricted to S2 and these effects were always superimposed on the ID response (additive effect). These findings suggest that the underlying mechanisms for ID discharge and attention are independent. ID discharge significantly modified the initial response to the standard stimuli (competing texture and visual stimuli), usually enhancing responsiveness. We also showed that tactile detection in humans is enhanced during the ID period. Together, the results suggest that ID discharge represents a priming mechanism that prepares cortical areas to receive and process sensory inputs.