Attention effects on sensory gating--intracranial and scalp recordings

The function of sensory gating is usually studied in paired-click experiments and quantified by the decrease of the event-related potential (ERP) component P50 and other ERP components from the 1st to the 2nd stimuli. The impact of attention on these gating measures is still not fully resolved. In the current study, the impact of attention on sensory gating was studied by scalp and intracranial recordings. The study sample consisted of epilepsy and tumor patients undergoing presurgical evaluation by means of implanted electrodes. In the unattend condition, patients had no overt task. In the active condition, patients had to count simultaneously trials with paired clicks, as well as interspersed trials with single clicks. The ERPs in the active condition were characterized by an underlying negativity both for scalp and neocortical recordings, reaching their maximum at the N100 latency of the 2nd stimulus. A time-frequency analysis revealed that this attention effect comprised only low frequency signals (<3 Hz). In line with that, P50 amplitude and P50 gating were unaffected by attention when data were filtered from 10 to 50 Hz. In addition, attention effects were revealed for intrahippocampal ERP components and for induced high frequency neocortical gamma band activity. Findings indicate that N100 and P200 gating measures can potentially be affected by attention and have to be interpreted carefully when studying clinical populations.