Figure 1. Recalibration of internal sensory predictions.

Sensory afference can result both from external events (exafference) and, as this figure illustrates, from our own actions (reafference) [1]. According to the comparator model, the nervous system establishes the cause of the sensory afference by comparing the actual sensory input with the predicted sensory input [2], [3]. To this end, the sensorimotor system predicts the sensory input which will result from one’s actions on the basis of internal action-related information, such as corollary discharge [5] of the motor command. This prediction is computed by a forward model [6], [7] which additionally takes into account the current state of the motor system and the sensory system [34], [64]. The nervous system then makes a comparison between the actual sensory input and the predicted sensory input. In case of a match, the sensory afference should be interpreted as internally caused. Otherwise, in case of a mismatch, the difference between the actual and the predicted input should be interpreted as externally caused. This difference between the actual and the internally predicted sensory consequences of one’s actions constitutes a prediction error. However, such errors arise not only from external influences. Prediction errors can also result from internal changes, i.e. changes within the sensorimotor system such as growth, fatigue or disease. Thus, one’s internal sensory predictions need continuous recalibration. As previous research suggests [16], [43], [65], this recalibration should compensate only for those prediction errors which result from internal causes. However, internally and externally caused prediction errors do not differ per se. Addressing this issue, we here demonstrate that the recalibration of internal sensory predictions by prediction errors depends on the attribution of the prediction error to internal causes. Figure adapted from Wolpert and Miall, 1996 [66].