Central Tremor Oscillators – a Directionality Study

This study investigates the relation of causality between the two central putative oscillators of the bilateral postural hand tremor. For this, we used a photic driving paradigm that induced at the visual cortical level a specific oscillatory activity. Having the particular functional relation between the hand motor system and the visual system, we assumed that changes in the last one were reflected in the central tremor oscillatory activity too. The stimuli frequencies were particularly chosen out of the alpha frequency band (7 Hz, 19 Hz), thus preventing the cortical driven oscillations to interfere with the spontaneous cortical rhythm. Physiological postural hand tremor was recorded bilaterally while the visual stimuli were delivered – either concurrently, either alternatively –, in the two visual hemifields. To track the causal functional interdependence between the two tremor central oscillators accompanying the corresponding changes induced in the cognitive state, we applied the partial directed coherence analysis