INFLUENCE OF VISUAL FEEDBACK ON HUMAN ISOMETRIC BITE-FORCE TREMOR

In contrast to recent reports, during an isometric short forceful bite , visual feedback had a significant influence on the force tremor spec trum. The value of a 'half-value frequency', being the frequency f1/2 at which, with increasing frequency, the amplitude of the spectrum for the first time drops to half its initial value, was used as an indica tor for the spectral behaviour. Under visual feedback, the amplitude c ontribution to the force spectrum in the 3-5 Hz frequency range was mu ch larger than after deprivation of visual feedback. Elevations in the frequency range between 3 and 5 Hz in the force spectrum are interpre ted as an expression of a visual feedback loop with a tau between 100 and 200 ms. This is supported by the visual/oral reaction times record ed, which were between 110 and 190 ms.