Abstract
When and how does the brain make use of contextual information to facilitate visual object perception? We recorded EEG while participants (N=72) learned paired associations between scenes and novel objects from novel object categories. At test, scenes were presented and, after a delay, a matching or mismatching object appeared. We previously showed that varying the amount of scene preview time at test affects the time course of predictive facilitation for the object. Long (2500ms), vs. short (200ms), preparation times induced a latency advance in the LPC and the appearance of a fronto-central N300 match effect. We (N=36) replicated these findings using a parametric, within-subjects design, by randomly varying the scene preview duration (0-2500ms). LPC match effect amplitude increased and latency decreased with increased preparation time, consistent with earlier results. However, graded effects of match (assessed using mismatching objects that were similar to a match, both visually and in terms of their distribution across contexts) were attenuated or absent, suggesting a role for temporal expectation in graded contextual prediction. We next used lateralized presentation with a long scene preview (2500ms; N=36) to explore whether the cerebral hemispheres differentially contribute to visual object prediction. Left visual field/Right Hemisphere (lvf/RH) presentation resulted in an earlier facilitation for the match condition relative to either mismatch type at prefrontal sites compared with right visual field / Left Hemisphere (rvf/LH) presentation. However, rvf/LH but not lvf/RH presentation induced sensitivity to close vs. 'impossible' mismatches at fronto-central sites (onset ~350ms). Findings suggest knowing when and where a visual object will appear helps us to anticipate it, and are consistent with the right hemisphere preactivating a more specific visual representation of the match than the left.
Meeting abstract presented at VSS 2018