The scan-paths of acquired and developmental prosopagnosic subjects during a face memorization task

Abstract

Introduction: The location and sequence of visual fixations can reveal internal estimates of the most informative locations to fixate and the efficiency of perceptual processing at those fixations. Therefore scanpaths can help evaluate subjects with impaired perceptual processing. In prosopagnosia – the impaired ability to recognize faces – there are apperceptive and amnestic variants, linked to occipito-temporal and anterior-temporal lesions respectively, as well as a developmental form. How these variants differ in scanning faces is not well known. Our goal was to compare their scanpaths with the hypothesis that the apperceptive variants would have more abnormalities in scanning behaviour than the amnestic variants. We also assessed a cohort with developmental prosopagnosia to determine if their behaviour resembled the apperceptive or the amnestic variants. Methods: We tracked the visual fixations of 20 control subjects, 8 developmental prosopagnosics, and 8 acquired prosopagnosics (4 apperceptive and 4 amnestic), as they memorized faces. We analyzed their scanpaths with a region of interest analysis, recurrence quantification analysis (RQA) and a ScanMatch analysis. Results: Subjects with the apperceptive variant showed an anomalous preference to fixate the periphery of faces (p< 0.05) compared to the three other groups. They also showed a trend of higher laminarity (p< 0.055) and entropy (p< 0.055) in the RQA suggestive of looking at facial features in more detail and in a more chaotic pattern than controls. The ScanMatch analysis showed that all groups except for the apperceptive variant had sequences of fixations which were more similar when looking at faces of the same identity versus different identities (p< 0.05). Conclusion: Subjects with apperceptive prosopagnosia from occipito-temporal lesions show anomalous scanning that suggests more difficulty processing and using internal features during a face-memorizing task. In contrast, subjects with an amnestic variant and those with the developmental form show more normal scanning behaviour.

Meeting abstract presented at VSS 2018