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Sarah Cook, Colin Flowers, Mary Peterson; Dichoptic Masking Interferes with Feedback to Early Visual Areas when Part- and Whole-Familiarity Conflict . Journal of Vision 2016;16(12):1172. doi: 10.1167/16.12.1172.
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The perirhinal cortex (PRhC) is sensitive to the congruency of configuration familiarity and part familiarity; it modulates part-familiarity responses in early visual areas (EVA), facilitating them when familiar parts are arranged in familiar configurations (Fam-configurations), and inhibiting them when they are re-arranged into novel configurations (PR-configurations; Barense, et al, 2012). Whereas control participants reported seeing Fam-configurations as figures more often than matched PR-configurations, PRhC–damaged patients reported seeing the latter as figure just as often as the former. Without PRhC modulation their figure reports were based on part-familiarity alone. Using dichoptic masking, we interfered with visual processing in healthy participants and examined part- and configuration-familiarity based figure assignment. Three types of displays were shown for 40 ms, followed by a 40ms ISI, then by either a 20-ms or 200-ms mask: critical regions depicted Fam-configurations, PR-configurations, or control inverted PR-configurations (iPR-configurations). The different mask durations differentially affected figure reports for PR-configurations only. With the 200-ms mask, participants saw PR-configurations as figure as often as Fam-configurations and more often than iPR-configurations (p < .05). This is the pattern expected if the mask interfered with inhibitory feedback from the PRhC, leaving part-familiarity responses in the EVA intact. Thus, dichoptic masking can interfere with feedback from higher-level brain regions. With the 20-ms mask, the pattern of responses differed (p< .01): figure reports for PR-configurations did not exceed chance, whereas both Fam-configurations and iPR-configurations were seen as figure substantially more often (ps < .03), with the former greater than the latter (p < .07). Either the offset transient of the 20-ms mask or the 60-ms stimulus termination asynchrony (STA) interfered with part-familiarity responses in EVA. Consequently, noisy part-familiarity signals were sent forward. Results suggest inhibitory feedback reduces noisy signals more than facilitatory feedback enhances them. Future research will vary mask duration to elucidate these effects.
Meeting abstract presented at VSS 2016
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