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Theodora Vahine, Stephanie Mathey, Jean-Noel Foulin, Sandrine Delord; Dissociation between magnocellular and parvocellular processing in visual word recognition. Journal of Vision 2016;16(12):1417. doi: 10.1167/16.12.1417.
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© 2017 Association for Research in Vision and Ophthalmology.
The objective was to test whether the parvocellular/magnocellular (P/M) dissociation found for visual objects also holds for word materials using the orthographic neighborhood (ON) effect in two lexical decision task experiments. Hermit words (i.e., with no ON) would have faster access to the lexicon than words with ON (i.e., word –acteur– with one higher frequency orthographic neighbor –auteur). In such letter substitution neighborhood, letter identity should be the critical dimension, conveyed by the P system. Spatial frequency (SF) filtering of the target (Experiment 1) and isoluminant stimuli (Experiment 2) were used to bias visual processing toward P (medium to high SF filtering or isoluminant colors) or M system (low SF filtered or grey low contrast). Experiment 1 results replicated the main inhibitory effect of ON on lexical decision latencies. A main effect of filtering was also observed, with shorter response times (RTs) for non-filtered control words, longer RTs for band-passed filtered words, and even longer RTs for low-passed filtered words. However, these two factors did not interact. Experiment 2 results replicated the main inhibitory effect of ON, and a main effect of isoluminant condition was found with longer RTs for the isoluminant words than for the low contrast grey words. Furthermore, an interaction between ON and isoluminant conditions was observed, with the ON effect found in the isoluminant condition only. Taken together, these results are consistent with the hypothesis of dissociation between the two visual systems for orthographic activation in visual word recognition processes. When letter identity is the relevant information, lexical access depends mainly on P visual processing. Comparison between the experiments also shows that isoluminant stimuli should provide a better P/M dissociation than SF filtering.
Meeting abstract presented at VSS 2016
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