Líf - og heilbrigðisvísindaráðstefna Háskóla Íslands 2021

The inseparability of visual processes in dyslexia and the inseparability of visual categories in prosopagnosia

Main author: Bahareh Jozranjbar
Institution or Company: University of Iceland

Co-Authors, Institution or Company:
Heiða María Sigurðardóttir, University of Iceland. Árni Kristjánsson, University of Iceland. Randi Starrfelt, University of Copenhagen, Copenhagen, Denmark. Christian Gerlach, University of Southern Denmark, Odense, Denmark.

Introduction: The selectivity of developmental prosopagnosia and dyslexia for stimulus category (faces or words), or process (featural or configural processing), is a subject of controversy. By manipulating featural and configural information in faces and houses, we investigated whether people with developmental prosopagnosia or dyslexia are disadvantaged in recognizing certain object classes or utilizing particular visual processing mechanisms.

Methods: Dyslexic and typical readers were tested in a delayed matching paradigm and individuals with prosopagnosia and matched controls on a simultaneous matching task.

Results: We used Representational Similarity Analysis (RSA) to correlate individual responses within each group and evaluate the similarity of these correlation matrices (reference models) with predicted data patterns (conceptual models). The reference models are correlation matrices of the accuracy of featural and configural processing of faces and houses with various difficulty levels. We created three conceptual models based on possible patterns for categories, processes, and task difficulty. RSA on behavioral data from the control groups revealed that processes were clearly separable as were responses to different stimulus categories. In comparison, dyslexic readers appeared to rely on a single visual process regardless of whether features or configurations were task-relevant, and the prosopagnosia group did not perform differently based on stimulus category.

Conclusions: We speculate that some dyslexic readers’ reading deficits reflect their dependence on a single process for object recognition. In contrast, the inseparability of visual categories in individuals with prosopagnosia suggests that their recognition problem is not category-selective.


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