Top-down attentional control resilience reveals time-sensitive transcranial magnetic stimulation effects.

Abstract

The frontal eye fields (FEFs) are critically involved in voluntary shifts of attention by sending top-down signals to posterior cortices to modulate local alpha-band activity. However, the exact temporo-spatial dynamics of this process are still unclear. Here, we investigated how covert shifts of attention and associated modulations of posterior alpha power are affected after FEF inhibition by transcranial magnetic stimulation (TMS). Neither right nor left FEF disruption impaired attention task performance. This absence of behavioral effects seems to be related to the here employed long cue-target intervals, giving the attention system sufficient time to compensate (across trials) for the TMS insult. Alpha power modulation was quantified both in the entire cue-target interval, and in two additional time windows: after cue presentation (early) and before target appearance (late). TMS effects on alpha power clearly differed across time windows, being strongest in the early time window. The reduced TMS effect in the late window might reflect recovery/compensation employed by the attention system, possibly explaining the lack of TMS-induced behavioral effects. These results are in line with a central role of the FEF in the control of visuospatial attention and support the notion of compensation mechanisms in cognitive brain systems in the temporal domain.