Perisaccadic mislocalization as optimal percept

Abstract

The spatially uniform mislocalization of stimuli flashed around the onset of fast eye-movements (perisaccadic shift) has previously been explained by an inaccurate internal representation of current eye position. However, this hypothesis does not account for the observation that continuously presented stimuli are correctly localized during saccades. Here we show that the two findings are not mutually exclusive. The novelty of our approach lies in our interpretation of the extraretinal signal which, in contrast to other models, is not considered an (erroneous) estimate of current eye-position. Based on the reafference principle, our model assumes that the extraretinal signal is optimal in that it accurately predicts the neural representation of the retinal position of a continuously present stimulus. Perisaccadic shift arises as a consequence of maintaining stable perisaccadic position estimates for continuously present stimuli under the physiologically plausible assumption of temporal low-pass filtering in the afferent visual pathway. Consequently, our model reconciles the reafference principle with the finding of perisaccadic shift.

A Computational Model for the Influence of Corollary Discharge and Proprioception on the Perisaccadic Mislocalization of Briefly Presented Stimuli in Complete Darkness

“…However, we show that the more plausible assumption of perceptual decision making by a neural integration process instead of time averaging in previous models lessens the influence of the late trace of the stimulus persistence, since neural integration depends on the temporal order within the activity trace. By switching off the CD signal in our model, we show that with reafferent eye position information alone no mislocalizations earlier than 50 ms before saccade onset can be achieved, which is also the earliest possible mislocalization in the model of Teichert et al (2010), even with slow temporal dynamics. Thus, we conclude that corollary discharge plays an essential role in explaining perisaccadic shift.…”

“…Since previous models claimed that perisaccadic shift can be explained without an anticipatory eye position signal (Pola, 2004;Teichert et al, 2010), we also tried to achieve the earliest possible mislocalizations without CD by shifting the updating of the proprioceptive signal to the earliest possible, although not plausible, time, which is immediately after saccade offset (data not shown). Indeed, this shifted the positive mislocalizations to start ϳ50 ms before saccade onset, which is also the earliest time that mislocalizations started in the previous models by Pola (2004) and Teichert et al (2010). An earlier misperception could only be achieved by a more pronounced visual latency or a longer (untypical) accumulation time in the decision neurons.…”

“…While early models (Dassonville et al, 1992) took a static account, deducing the extraretinal signal from behavioral data and interpreting it as a sluggish eye position estimate, Pola (2004) and Teichert et al (2010) introduced a realistically modeled retinal signal and temporal integration and, as a consequence, concluded that an anticipatory extraretinal signal is not necessary to explain the data. However, these models struggle with early onsets of mislocalization as well as with newer findings that show a saturation of mislocalization for larger saccade amplitudes (Van Wetter and Van Opstal, 2008).…”

“…Corollary discharge is hypothesized to mediate perisaccadic suppression as well as predictive remapping of visual receptive fields to anticipate the effects of saccadic eye movements (Wurtz, 2008), but so far only little work demonstrated its relevance for performing particular tasks (e.g., double step) (Sommer and Wurtz, 2008). The model of Teichert et al (2010) and similarly the one of Pola (2004) suggest that such anticipatory extraretinal signals are not required to explain the data of perisaccadic shift. However, we show that the more plausible assumption of perceptual decision making by a neural integration process instead of time averaging in previous models lessens the influence of the late trace of the stimulus persistence, since neural integration depends on the temporal order within the activity trace.…”

“…Pola (2004) proposed a more elaborate model accounting for delay and visual persistence and concluded that the extraretinal signal may only change after saccade onset. Similarly, imposing the additional constraint of no mislocalization for continuously visible stimuli, Teichert et al (2010) proposed that reafferent position information is sufficient to explain perisaccadic shift.…”