Perisaccadic Compression Correlates with Saccadic Peak Velocity: Differential Association of Eye Movement Dynamics with Perceptual Mislocalization Patterns

Objects flashed around the onset of a saccadic eye movement are grossly mislocalized. Perisaccadic mislocalization has been related to a spatiotemporal misalignment of an extraretinal eye position signal with the corresponding saccade. Two phenomena have been observed: a systematic shift of perceived positions in saccade direction and an additional compression toward the saccade target. At present, it is unclear whether these two components of mislocalization are mediated by distinct mechanisms and how extraretinal signals may contribute to either of them. Moreover, the pattern and strength of perisaccadic mislocalization varies considerably across studies and even between subjects tested under identical conditions. Here, we investigated whether interindividual differences in saccade parameters are related to differences in mislocalization. We found that the individual strength of perceptual compression selectively correlates with the peak velocity of corresponding saccades. Other saccade parameters did not correlate with compression. No correlation was found between the shift component of perisaccadic mislocalization and any saccade parameter. This dissociation suggests that shift and compression components are, at least partially, mediated by distinct mechanisms. Because neuronal activity in the superior colliculus and downstream oculomotor areas has been shown to correlate with saccadic peak velocity, our findings support the notion that a reafferent extraretinal signal associated with saccadic motor commands may contribute to perisaccadic compression of perceived positions.