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Michael Aicken, Justin Williams, Mark Mon-Williams; The role of serotonin in visuomotor activity. Journal of Vision 2004;4(8):415. doi: 10.1167/4.8.415.
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Serotonin is involved in various aspects of brain function including sleep, appetite, mood and cognition. Several disease states characterised by abnormal central serotonin levels are also associated with impaired visuomotor skills (e.g. depression). This study is the first to look specifically at the effect of lowered central serotonin levels on skilled motor performance. In order to study the role of the serotonergic system in motor performance we reduced central serotonin levels through L-tryptophan depletion in healthy volunteers. Acute tryptophan depletion (ATD) was achieved by participants consuming a 100g amino acid drink? a paradigm that is known to create alterations in a variety of cognitive functions. A prehension paradigm used previously in normal adults was used to investigate the extent to which prehension was altered by ATD. Blood tests and a selection of cognitive tests were used to quantify the established effect of the ATD procedure. The present experiment used unimanual (a well rehearsed task) and bimanual reach-to-grasps (a more complex task involving selective attention) in order to investigate motor performance in 8 healthy, right handed males in a double-blind, placebo-controlled crossover design. In our prehension paradigm, one hand (fixed) always moved to the same object at a fixed distance while the other hand (variable) moved to objects of different width (3,5,7cm) and grip surface size (1,2,3cm) placed at different distances (20, 30, 40cm) over 280 trials. Previously, adults were found to exhibit simultaneous coordination of both arms during an initial phase of bimanual prehension, followed by a sequential completion phase. Variables such as total movement time, peak speed and maximum grip aperature were considered as well as quantification of the extent to which both arms behaved in synchrony during a state of tryptophan depletion. The results of this study provide an insight into the role of serotonin in bimanual coordination tasks.
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