Heart rate deceleration reflects expectation violation during reaching

Heart rate (HR) deceleration occurs following movement error and has been interpreted as an autonomic response to adverse behavioral outcomes. However, movement errors not only represent adverse movement outcomes but may also violate expectations. The present study employed a reaching movement paradigm using a robotic manipulandum in male and female human participants to dissociate the contributions of movement outcome and expectation violation to HR responses. We confirmed that HR deceleration occurred following visuomotor perturbations that induce movement errors, consistent with previous studies. However, when contextual cues predicted upcoming movement outcomes, HR deceleration emerged during movement preparation rather than following movement error, suggesting the involvement of expectation in HR responses. Moreover, across varying levels of expectation for different movement outcomes, HR deceleration was associated with unexpected movement outcomes rather than with the negative valence of movement outcomes. By altering target width to permit successful movements despite visuomotor rotations, we further found that HR deceleration was more strongly associated with task error than with sensory prediction error. Together, these findings indicate that HR responses during movement are more closely associated with violations of movement expectation than with movement error itself. These findings provide a new perspective on autonomic responses during sensorimotor processing and suggest that HR may serve as a physiological marker of expectation-related processing during movement.