Neural prediction of complex accelerations

40 41 To successfully intercept or avoid moving objects, we must compensate for the sensorimotor 42 delays associated with visual processing and motor movement. While straightforward in the 43 case of constant velocity motion, it is unclear how humans compensate for accelerations, as 44 our visual system is relatively poor at detecting changes in velocity. Work on free falling 45 objects suggests that we are able to predict the effects of gravity, but this represents the most 46 simple, limiting case in which acceleration is constant and motion linear. Here, we show that 47 an internal model also predicts the effects of complex, varying accelerations when they result 48 from lawful interactions with the environment. Participants timed their responses with the 49 arrival of a ball rolling within a tube of various shapes. The pattern of errors indicates that 50 participants were able to compensate for most of the effects of the ball’s acceleration (~ 85 51 %) within a relatively short practice (~ 300 trials). Errors on catch trials in which the ball’s 52 velocity was unexpectedly maintained constant, further confirmed that participants were 53 expecting the effect of acceleration induced by the shape of the tube. A similar effect was 54 obtained when the visual scene was projected upside down, indicating that the mechanism of 55 this prediction is flexible and not confined to ecologically valid interactions. These findings 56 demonstrate that the brain is able to predict motion on the basis of prior experience of 57 complex interactions between an object and its environment. 58 59