Role of post-trial visual feedback on unintentional force drift during isometric finger force production tasks

Force produced during an isometric finger force production task tends to drift towards a lower magnitude when visual information is occluded. This phenomenon of drift in force without one’s awareness is called unintentional drift. The present study used epilogue, a particular case of post-trial visual feedback, and compared the unintentional drift for two conditions, i.e., with and without the epilogue. For this purpose, fourteen healthy participants were recruited for the experiments and were instructed to produce fingertip forces using four fingers of the right hand with the target line at 15% MVC. A trial lasted for sixteen seconds, where for the initial eight seconds, there is visual feedback followed by the visual occlusion period. The results showed a significant reduction in unintentional drift for the condition involving epilogue when compared to no epilogue. This reduction in drift is due to the shift in the referent configuration parameter by the phenomenon of RC back coupling. Further, we also claim that there might be a distribution of λs or RCs, based on the history of tuning of the control parameter by the central controller. This distribution of λs selected by the central controller in a redundant environment based on the epilogue resulted in a reduction of unintentional drift.