Why Does the Brain Predict Sensory Consequences of Oculomotor Commands? Optimal Integration of the Predicted and the Actual Sensory Feedback

Abstract

When the brain initiates a saccade, it uses a copy of the oculomotor commands to predict the visual consequences: for example, if one fixates a reach target, a peripheral saccade will produce an internal estimate of the new retinal location of the target, a process called remapping. In natural settings, the target likely remains visible after the saccade. So why should the brain predict the sensory consequence of the saccade when after its completion, the image of the target remains visible? We hypothesized that in the post-saccadic period, the brain integrates target position information from two sources: one based on remapping and another based on the peripheral view of the target. The integration of information from these two sources could produce a less variable target estimate than is possible from either source alone. Here, we show that reaching toward targets that were initially foveated and remapped had significantly less variance than reaches relying on peripheral target information. Furthermore, in a more natural setting where both sources of information were available simultaneously, variance of the reaches was further reduced as predicted by integration. This integration occurred in a statistically optimal manner, as demonstrated by the change in integration weights when we manipulated the uncertainty of the post-saccadic target estimate by varying exposure time. Therefore, the brain predicts the sensory consequences of motor commands because it integrates its prediction with the actual sensory information to produce an estimate of sensory space that is better than possible from either source alone.

Inside the brain of an elite athlete: the neural processes that support high achievement in sports

“…There is good experimental evidence that forward models enable precise actions that are too fast to rely on the delays that are inherent in sensory feedback [106][107][108] , allow more precise state estimation 109 , and can be updated through learning 26,107 . For example, when you move your hand from one place to another, the brain can estimate its new position before sensory feedback arrives.…”

Spatial constancy mechanisms in motor control

“…Vaziri et al [133] tested reaches to visual targets that were initially on the fovea, but saccadically brought to the periphery, before the reach. The authors manipulated the uncertainty of the post-saccadic peripheral target information by varying the length of target exposure.…”

Control of Predictive Error Correction During a Saccadic Double-Step Task

“…This potentially involves the use of an internal feedback control (Robinson 1968;Scudder 1988), allowing error correction to begin only after the erroneous saccade has occurred. Alternatively, fast on-line error correction may involve a comparison of the spatial location of the goal with the anticipated eye displacement using feedforward control (Bernstein et al 1995;Desmurget and Grafton 2000;Shadmehr and Mussa-Ivaldi 1994;Vaziri et al 2006;Wolpert et al 1995) such that any deviations can be corrected without the delays associated with sensory feedback. In principle, such a mechanism allows for error correction to proceed in parallel with the erroneous saccade, even before the error is committed.…”