Transcranial direct current stimulation (tDCS) applied to the left dorsolateral premotor cortex (dPMC) interferes with rhythm reproduction.

Movement timing in the sub-second range engages a brain network comprising cortical and sub-cortical areas. The present study aims at investigating the functional significance of the left dorsolateral premotor cortex (dPMC) for precise movement timing as determined by sensorimotor synchronization and rhythm reproduction. To this end, 18 healthy volunteers performed an auditorily paced synchronization-continuation task with the right hand. A simple reaction time task served as control condition. Transcranial direct current stimulation (tDCS) was applied over the left dPMC in order to modulate cortical excitability either with anodal or cathodal polarity or as sham stimulation. TDCS was applied for 10 minutes, respectively on separate days. For the continuation task the analysis revealed significantly smaller inter-tap intervals (ITIs) following cathodal tDCS suggesting movement hastening as well as a trend towards larger ITIs following anodal stimulation suggesting movement slowing. No significant effect was found following sham stimulation. Neither for synchronization nor for reaction time tasks significant polarity-specific effects emerged. The data suggest the causal involvement of the dPMC in temporally precisereproduction of isochronous rhythms rather than sensorimotor synchronization. The present findings support the hypothesis that different cortical brain areas within the motor-control-network distinctively contribute to movement timing in the sub-second range.

Serotonin-induced platelet intracellular Ca2+ response in patients with anorexia nervosa.

INTRODUCTION: Serotonin (5-HT) is involved in the regulation of food intake. In anorexia nervosa there is a disturbance in 5-HT function. The stimulation of 5-HT(2)-receptors in platelets is a useful peripheral model to investigate the cascade of signal transduction and neuronal functioning. METHODS: 25 anorexic female patients between the ages of 11 and 18 years with a mean body mass index (BMI) of 13.9+/-1.3 kg/m(2) participated in this study. The 21 healthy female controls revealed a mean BMI of 20.5+/-2.7 kg/m(2). 5-HT stimulated intracellular Ca(2+) response of the platelets was obtained using the Fura-2 method at the time of admission, during therapy and when the target BMI was reached. RESULTS: We found a significant (p<0.01) decrease in 5-HT-induced Delta[Ca(2+)](i) at admission and a significant (p<0.05) increase of Delta[Ca(2+)](i) during treatment in patients with anorexia nervosa. Anorexic patients with and without comorbid depression had a comparable Ca(2+) release. However, low and high Ca(2+) responders showed a different course of Delta[Ca(2+)](i). The treatment with antidepressants led to a significant increase of Delta[Ca(2+)](i) in those patients with concomitant depression. DISCUSSION: Since the course of Delta[Ca(2+)](i) is not related to BMI or the presence of comorbid depression, we conclude that serotonergic transmission or signaling pathways could be disturbed in patients suffering from anorexia nervosa. One inference of this preliminary study is that administration of antidepressants may be more effective in patients with concomitant depression.