Movement Preparation: Neuroimaging Studies

Abstract

Our interactions with the external environment involve a continuous transformation of sensory stimuli into behavioural responses. Eventually, the neural codes of stimuli and responses need to be merged. Several solutions have been proposed to account for spatial visuomotor transformations (Burnod et al. 1999; Jeannerod et al. 1995; Soechting & Flanders 1992). However, these conceptual frameworks might be inadequate to explain our ability to act according to arbitrary visuomotor associations. In this particular category of sensorimotor transformations, behaviour is guided by rules rather than objects or places (Passingham & Toni 2001; White & Wise 1999). The flexibility of these stimulus-response relationships is vast, allowing us to transcend the domain of spatially or temporally congruent associations. Such flexibility suggests that arbitrary associations can be best established and accessed through manipulation of high level representations of stimuli and responses (Passingham, Toni, & Rushworth 2000; Toni & Passingham 1999), since these internal states of an agent are not tied to a particular sensory or effector system (Markman & Dietrich 2000). For instance, movement representations are considered to be independent from the performance of an actual motor act, or from the presence of a response’s target and sensory instructions (Jeannerod 1997). Since we can act according to arbitrary rules, the general mechanisms underlying sensorimotor transformations do not need to be constrained in spatial or temporal frameworks.