Brain potentials related to voluntary hand tracking, motivation and attention.

While there are many behavioural studies available investigating human hand tracking performance, there are none that include recording of cerebral potentials. Sixteen subjects tracked a visual or a tactile target by moving a stylus with their right hand. They voluntarily started the stimulus, which moved for 1 s in a first random direction, then for 1's in another direction. The stimulus was given to the left field of vision or tactually to the left palm. Tracking was compared to no-tracking controls. The voluntary initiation was preceded by a Bereitschaftspotential (BP), the change in direction by a contingent negative variation (CNV). Both BP and CNV showed a characteristic right hemispheric parietooccipital (visual task) or centro-parietal asymmetry (tactile task) due to the attention paid to the expected stimulus event ("directed attention potential", DAP). While the DAP outlasted stimulus onset by 0.2 s, fronto-midline areas switched already to positivity 100 ms prior to stimulus onset and more than 300 ms prior to the change in direction. Large P300-like components were elicited by stimulus onset and change in direction.