Differences in intersaccadic adaptation transfer between inward and outward adaptation

Abstract

Schnier F, Lappe M. Differences in intersaccadic adaptation transfer between inward and outward adaptation. J Neurophysiol 106: 1399 -1410. First published June 15, 2011 doi:10.1152/jn.00236.2011.-Saccadic adaptation is a mechanism to increase or decrease the amplitude gain of subsequent saccades, if a saccade is not on target. Recent research has shown that the mechanism of gain increasing, or outward adaptation, and the mechanism of gain decreasing, or inward adaptation, rely on partly different processes. We investigate how outward and inward adaptation of reactive saccades transfer to other types of saccades, namely scanning, overlap, memory-guided, and gap saccades. Previous research has shown that inward adaptation of reactive saccades transfers only partially to these other saccade types, suggesting differences in the control mechanisms between these saccade categories. We show that outward adaptation transfers stronger to scanning and overlap saccades than inward adaptation, and that the strength of transfer depends on the duration for which the saccade target is visible before saccade onset. Furthermore, we show that this transfer is mainly driven by an increase in saccade duration, which is apparent for all saccade categories. Inward adaptation, in contrast, is accompanied by a decrease in duration and in peak velocity, but only the peak velocity decrease transfers from reactive saccades to other saccade categories, i.e., saccadic duration remains constant or even increases for test saccades of the other categories. Our results, therefore, show that duration and peak velocity are independent parameters of saccadic adaptation and that they are differently involved in the transfer of adaptation between saccade categories. Furthermore, our results add evidence that inward and outward adaptation are different processes.

Mislocalization of stationary and flashed bars after saccadic inward and outward adaptation of reactive saccades

“…Zimmermann and Lappe (2010) showed that visual localization of eccentric targets during fixation was much more susceptible to saccadic adaptation for outward than for inward adaptation. These results, together with those of Schnier and Lappe (2011) and Ethier et al (2008), suggest that there is a stronger modulation of target localization stages after outward than that after inward adaptation of reactive saccades. In this view, target localization stages, located before the sensorimotor transformation, are especially used in the execution of overlap and scanning saccades, leading to a higher amount of transfer to these latter saccade types dependent on whether target localization stages are modulated by saccadic adaptation.…”

“…Transfer from reactive saccades to overlap and scanning saccades is significantly stronger after outward adaptation than that after inward adaptation (Schnier and Lappe 2011). Such a transfer difference was not found for the gap and the memoryguided saccade type, suggesting that the amount by which gain transfer differed between inward and outward adaptation for scanning and overlap saccades seems to be essentially related to the presentation duration of the saccade target.…”

“…Scanning saccade adaptation, in contrast, should lead to clear adaptation of reactive saccades since both involve short-latency neurons. Indeed, the amount of transfer between reactive and overlap saccades depends on the duration of the overlap (Deubel 1999;Schnier and Lappe 2011).…”

“…Furthermore, the corresponding final gain level is lower and less stable after outward adaptation than after inward adaptation (Ethier et al 2008;Golla et al 2008;Hernandez et al 2008;Miller et al 1981 Straube et al 1997;Zimmermann and Lappe 2010). Finally, differences have also been observed in the adjustment of saccade dynamics (peak velocity, duration) between the inward and outward adaptation procedures (Ethier et al 2008;Golla et al 2008;Schnier and Lappe 2011).…”

“…Since there is a stronger adaptation transfer from reactive to long-duration overlap or scanning saccades after outward than after inward adaptation of reactive saccades (Schnier and Lappe 2011), we wondered whether the mislocalization of stationary probes that was observed for inward adaptation of scanning but not reactive saccades (Zimmermann and Lappe 2009), reflecting the asymmetric transfer behavior between both saccade types, may be observed for reactive saccades when outward rather than inward adaptation is performed. In this context we also tested the adaptation-induced localization judgments of flashed and stationary bars during periods of fixation.…”