The behavioural and electrophysiological effects of visual task difficulty and bimanual coordination mode during dual-task performance.

The difficulty of a visual three stimulus and a bimanual coordination task was manipulated by varying discrimination difficulty (easy, hard) and coordination mode (in-phase, anti-phase) respectively. Electroencephalographic activity was recorded from 32 sites whilst participants (n = 16) completed four dual-task conditions in counterbalanced order. Longer reaction time and lower accuracy were found for the hard relative to the easy visual task and, for the hard visual task, accuracy was lower under anti-phase relative to in-phase conditions. Amplitude and latency of event-related potential components P3a and P3b were recorded and measured. There was a reduction in P3b amplitude and increase in P3a amplitude for the hard visual task overall and a further reduction in frontal P3b amplitude under the more demanding anti-phase condition. For the easy visual task, however, P3b and P3a amplitude were greater under the anti-phase relative to in-phase coordination condition at left hemisphere frontal sites. These findings suggest that the attentional cost of stabilising anti-phase bimanual coordination is largely associated with top-down automatic processes subserved by the frontal attentional network.