The role of discrepant retinal motion during walking in the realignment of egocentric space

Abstract

Visually guided action relies on accurate perception of egocentric direction. Unfortunately, perceived direction easily becomes misaligned. How is this problem overcome? One theory (R. Held & S. J. Freedman, 1963) is that during self-movement the observer uses the relationship between anticipated and experienced sensory feedback as a source of information to maintain alignment. However, data supporting this theory is equivocal, and recent evidence appears contradictory. We reexamined the issue. We injected an error into perceived visual direction and then assessed realignment after a period of walking toward a target. We manipulated the sensory information available (presence of retinal motion, Experiment 1; presence of peripheral motion, Experiment 2) and found that as the amount of retinal motion was reduced (Experiments 1 and 2), realignment of perceived visual direction decreased. When we then (Experiment 3) removed the discrepancy between anticipated and experienced retinal motion, no realignment was observed. Our results provide evidence that a discrepancy between anticipated and experienced sensory feedback is an important source of information for the alignment of egocentric space, with retinal motion having a particular role in driving a realignment of perceived visual direction.

Neither the richness of optic flow, nor the precision of heading judgements, predicts walking trajectories

“…The reduction from the first to fourth trial was, in order of magnitude, 3.02° (SD = 3.19°) in the Cloud environment, 1.99° (SD = 4.23°) in the Room, 1.33° (SD = 3.26°) in the Outline and 1.28° (SD = 3.29°) in the Line environment. This ordering ( Line < Outline < Room < Cloud ) does reflect the richness of optic flow across environments and is compatible with earlier work (Herlihey & Rushton, 2012).…”

“…Before concluding, it is important to look further. Richness of optic flow may prove a good predictor of trajectory over a longer time frame: Exposure to discrepant visual feedback (as happens in our experiment) leads to a process of adaptation, either of perception ( Rushton & Salvucci, 2001;Herlihey & Rushton, 2012), and/or of perceptual-motor mappings (Bruggeman et al, 2007). Such an adaptation would change the trajectories taken.…”

“…We first examined the target-heading angles for the early (6 ± 0.25m from the target) part of the trajectories ( Figure 5). Changes in the early measure indicate adaptation (as for example would result from changes in perceived egocentric straight-ahead, Herlihey & Rushton, 2012). The mean target-heading angle of the early part of the trajectory reduces from the first to the fourth trial in all environments [all Bonferroni-corrected ps < 0.05], indicating adaptation.…”

Influence of optic flow on the control of heading and target egocentric direction during steering toward a goal

“…Accordingly, the effect of optic flow observed in previous walking studies could be due to the shifted perceived target egocentric direction rather than the use of heading. Indeed, it has been shown that after walking for a period of time with prism glasses that displaced heading specified by optic flow away from the straight-ahead, observers perceived their straight-ahead to be biased toward the displaced heading (Held and Bossom 1961;Herlihey and Rushton 2012;Morton and Bastian 2004;Redding and Wallace 1985). With the use of a visual control of steering task, Li et al (2012) also found that the longer one steers toward a target with displaced heading, the larger the shift of the perceived straight-ahead.…”

The effect of prism adaptation on state estimates of eye position in the orbit

“…There has been a finding of a larger OLP after-effect compared to SAP after-effect following a full decay of the VSA after-effect (Hatada, Rossetti, & Miall, 2006), and observations of greater OLP after-effects compared to combined VSA and SAP after-effects (e.g., Welch, Choe, & Heinrich, 1974). Reports from studies finding no visual after-effect in healthy people have also accumulated (Bornschlegl et al, 2012;Harris, 1963;Herlihey & Rushton, 2012;Michel, Gaveau, Pozzo, & Papaxanthis, 2013;Morton & Bastian, 2004;Newport, Preston, Pearce, & Holton, 2009). The lack of observable visual after-effect in many studies alongside the pattern of deviations from linear additivity suggest that there might be an issue with how the VSA after-effect has previously been measured, or how the visuomotor change is understood.…”