The effect of switching between sequential and repetitive movements on cortical activation

We used whole-head functional magnetic resonance imaging (fMRI) to investig ate the effect of switching between different sequential and repetitive mov ements in the context of conditional and fixed tasks. Four different moveme nt tasks were applied: (1) unpredictable switching between two movement seq uences comprising six submovements each according to visual cues (SEQ=VC); (2) unpredictable switching between repetitive movement of one finger accor ding to visual cues (REP-VC); (3) performance of the same sequential moveme nts used for SEQ-VC but in a fixed mode triggered by a visual stimulus (SEQ -FIX); (4) performance of the repetitive movements used for REP-FM but in a fixed mode by a visual stimulus (REP-FIX). The statistical group analysis of the hemodynamic responses revealed the following results: (1) the:SEQ-VC compared to the SEQ-FM condition (switching between movement:sequences) en gendered stronger activations in the left rostral supplementary motor area (pre-SMA), bilaterally in the posterior parietal lobule, the left ventral p remotor area, and the visual cortices; (2) the REP-VC compared to the REP-F IX condition (switching between repetitive movements) only revealed stronge r activation in extra-striate areas. We hypothesize that during switching o f movement sequences higher motor control aspects are involved including mo vement selection, updating of motor plans, as well as recalling and restori ng motor plans. The repetitive movements are too simple in order to evoke a dditional activations in the medial and lateral premotor areas, as well as in parietal areas, (C) 2000 Academie Press.