Amblyopic deficits in structure-from-motion processing

Abstract

Amblyopia is known to include striate deficits (e.g. Barnes et al., 2001; Movshon et al., 1987), but less is known about whether extra-striate mechanisms are additionally impacted (e.g. Barnes et al., 2001; Kiorpes, 1998; Simmers, 2006). To tap into extra-striate processing, we tested amblyopic and control observers on a structure-from-motion (SFM) task, which requires integration of local elements to perceive the global structure. Subjects were monocularly presented with a 2-IFC shape discrimination task, indicating whether two consecutive SFM stimuli represented the same or different shapes. Two interleaved 3-down-1-up staircases were used to determine the threshold amount of depth necessary to distinguish the shapes. Preliminary data with 10 amblyopic and 10 control subjects indicates that amblyopes need more depth information to reliably discriminate shape identities (t(38) = 2.5, p = .02), and that this deficit was present for both the amblyopic and fellow-fixing eyes (t(9) = 1.22, p = .26). These results suggest that amblyopic observers experience a deficit in SFM processing. Future work will adapt this task to incorporate band-pass local elements, which will enhance our ability to control for low-level contributions to this task, and help differentiate whether deficits in this task are specific to high-level neural processing mechanisms, or whether these deficits are adequately accounted for by existing known low-level deficits.

Acknowledgments

Supported by CIHR Grant No. MT10818 awarded to Robert Hess.