Hand Motor Preparation Research Articles

How Embodied Is Perceptual Decision Making? Evidence for Separate Processing of Perceptual and Motor Decisions

The extent to which different cognitive processes are "embodied" is widely debated. Previous studies have implicated sensorimotor regions such as lateral intraparietal (LIP) area in perceptual decision making. This has led to the view that perceptual decisions are embodied in the same sensorimotor networks that guide body movements. We use event-related fMRI and effective connectivity analysis to investigate whether the human sensorimotor system implements perceptual decisions. We show that when eye and hand motor preparation is disentangled from perceptual decisions, sensorimotor areas are not involved in accumulating sensory evidence toward a perceptual decision. Instead, inferior frontal cortex increases its effective connectivity with sensory regions representing the evidence, is modulated by the amount of evidence, and shows greater task-positive BOLD responses during the perceptual decision stage. Once eye movement planning can begin, however, an intraparietal sulcus (IPS) area, putative LIP, participates in motor decisions. Moreover, sensory evidence levels modulate decision and motor preparation stages differently in different IPS regions, suggesting functional heterogeneity of the IPS. This suggests that different systems implement perceptual versus motor decisions, using different neural signatures.

Posterior and Anterior Contribution of Hand-Movement Preparation to Late CNV

Abstract The late part of the Contingent Negative Variation (CNV) is assumed to be a composite potential, reflecting both movement preparation and several other processes. To assess the contribution of hand-motor preparation to overall CNV, three S1-S2 experiments were performed. Replicating earlier results that have been interpreted as demonstrating hand-motor preparation, experiment 1 showed that CNV gets larger centro-parietally under speed instruction. Experiments 2 and 3 compared preparation for hand responses (key-press) to preparation for ocular responses (saccades) varying the effector system either between blocks (exp. 2) or between trials (exp. 3) and also comparing these preparation situations to no preparation (exp. 3). Hand-motor preparation was reflected in CNV getting larger fronto-centrally, with this topography being significantly different from the effect in experiment 1. Thus, two different kinds of motor preparation appear to be reflected by CNV. One kind may consist of assembling and maintaining the stimulus-response links appropriate to the expected S2 patterns, the other is for activating the hand-motor area. These two motor contributions to CNV might reflect the two aspects of the parieto-frontal motor system.