The 'gap effect' (GE) refers to the widely accepted finding that reaction time (RT) for a saccade or reaching movement is significantly reduced with the introduction of a gap between the disappearance of the central target (CT) and the appearance of one of the possible peripheral targets (PT). The effect has been attributed to two potential mechanisms, an attentional and fixation disengagement and a general warning effect, in both of which premotor areas are thought to be involved. To unveil the role of the Dorsal Premotor cortex (PMd) we recorded neural activity in two macaque monkeys trained in a reaching task formed by two different trials. ?Monkeys were instructed to hold the arm over a CT for a variable amount of time and to move toward a PT, at soon as it appeared. In the 'no-gap' trials, the PT appeared at the same time of the CT disappearance. In the 'gap' trials, the PT appeared 200 milliseconds after the CT offset.

Single unit activity (SUA), local field potentials (LFP) and multiunit activity (MUA) were analyzed. In the time domain, cross-correlation analysis of the LFPs disclosed a significant anticipation of the LFP of the 'gap' trials over the LFP of the 'no-gap' trials, as aligned to PT presentation. In the frequency domain, we found significant GE-related beta and gamma modulation. Conversely, SUA/MUA modulations were observed more time-locked to movement onset. Our findings support a direct involvement of PMd in the neural processes that result in the GE.