Abstract
Stimulus-driven actions are preceded by preparatory brain activity that
can be expressed by event-related potentials (ERP). Literature on this
topic has mainly focused on simple actions, such as the finger keypress,
finding activity in frontal, parietal, and occipital areas detectable up
to two seconds before the stimulus onset. However, little is known about
the preparatory brain activity when the action complexity increases, and
specific brain areas designated to achieve movement integration
intervene. The main aim of this paper is to identify the time course of
preparatory brain activity associated with actions of increasing
complexity using ERP analysis and a visuomotor discrimination task.
Motor complexity was manipulated by asking nineteen volunteers to
provide their response by simply pressing a key or by adding to the
keypress arm extensions (reaching) alone, or in combination with a
standing step (involving the whole body). Results showed that these
actions of increasing levels of complexity appear to be associated with
different patterns of preparatory brain activity. Specifically, the
simple keypress was characterized by the largest motor excitatory
preparation in premotor areas paralleled by the largest prefrontal
inhibitory/attentional control. Reaching presented a dominant parietal
preparation confirming the role of these integration areas in reaching
actions toward a goal. Stepping was characterized by localized activity
in the bilateral dorsomedial parieto-occipital areas attributable to
sensory readiness, for the approaching stimulus. In conclusion, the
brain is able to optimally anticipate any stimulus-driven action
modulating the activity in the brain areas specialized in the
preparation of that action type.