La fatigue induite de la voie magnocellulaire ralentit la discrimination de lettres miroirs

Details

Supervisors

Vannuscorps, Gilles ; Houbben, Marie

Faculty

Faculté de psychologie, logopédie, sexologie et des sciences de la famille

Degree label

Master [120] en sciences psychologiques, à finalité spécialisée

Abstract

enMirror-image confusion is well documented in typical development, acquired neurological conditions, and developmental dyslexia. Recent case studies (e.g., Davida; Vannuscorps et al., 2021, 2022, 2026) suggest this confusion may stem from an imbalance between the magnocellular (M) and parvocellular (P) visual pathways, whereby parvocellular-favoring stimulation excessively inhibits the magnocellular contribution otherwise required for correct orientation resolution. This study tested this hypothesis experimentally in 50 neurotypical adults by transiently fatiguing the magnocellular pathway via Fast Flicker Adaptation (FFA) during a lexical decision task containing either mirror-reversed (b/d) or phonological errors, under control versus FFA visual conditions (2×2 within-subject design). Accuracy showed no interaction between visual condition and error type; reaction times showed only a non-significant trend in the expected direction. The inverse efficiency index revealed a significant interaction (p = .014), with a numerically larger FFA cost for mirror than phonological errors, though pairwise comparisons did not survive correction. These findings offer partial but theoretically convergent support for a causal contribution of the magnocellular pathway to mirror-image discrimination in neurotypical adults. Methodological limitations and directions for future research are discussed.