Influence of grasp context-dependent uncertainty on sensorimotor integration during object manipulation is independent of stimulus history.

Anticipatory control during dexterous object manipulation has been shown to operate around a dichotomy of largely feedback-based or feedforward grip force modulation, depending on whether the choice of contact points is allowed or not. This study explores how a binary uncertainty prior to movement onset about the grasp context affects the balance of these predictive mechanisms in sensorimotor integration. We probed predictive control through a manipulation task requiring anticipatory moment compensation to minimise object roll for an asymmetrical weight distribution. Our previous work had shown that such pre-movement uncertainty about the grasp context elicited kinetic signatures during the loading phase, insofar as altering the normative relative contribution of feedforward vs. feedback force control. Building on these findings, in this paper we analysed the role of the distribution of prior stimuli on the influence of this uncertainty within the framework of motor planning. Despite our expectations that participants would modulate their reliance on sensory feedback based on stimulus history, the findings showed evidence against such history-dependent modulation. This outcome suggests two possibilities, that the participants either refrained from internalising the temporal structure of the uncertainty, or they dissociated learning of the stimulus structure from sensorimotor integration to avoid motor errors.