Distinct contributions of motor imagery and execution to history-dependent biases in reaching

The recent movement history shapes motor performance, that is, previous movements can affect current movement characteristics such as trajectory shape. History effects are commonly attributed to carryover of motor-related activity. However, action execution entails sensory feedback; therefore, an alternative is that history effects stem from the sensory information produced by previous movements. To dissociate motor and sensory contributions, we assessed whether history effects emerge from imagined movements, which involve movement planning but not sensory feedback. Overt reaches around an obstacle led to systematic adjustment of the initial reach direction of following reaches - a hallmark of motor history. Imagined reaches around obstacles induced similar biases, albeit with smaller magnitude, presumably due to the need to inhibit overt execution during imagery. By contrast, execution but not imagery induced biases in late, feedback-related measures, suggesting that these history effects depended on sensory rather than motor aspects of the movement history. Thus, motor and sensory signals make distinct and complementary contributions to movement history: recent motor states shape feedforward planning, whereas recent sensory states shape feedback-related movement refinement.