Phonological and orthographic visual word recognition in the two cerebral hemispheres

What is it about?

Studies on the cerebral mechanisms of reading have mostly used Latin-based writing systems and assume that the left, but not the right, cerebral hemisphere is capable of phonological processing. The present study used Hebrew as the test language to examine the effects of phonological and orthographic information in the two hemispheres. In unvoweled Hebrew script, words are read via consonant information alone. We used two naming tasks with an interference paradigm, where phonemically, orthographically, and figurally incorrect vowel information conflicted with the consonant information of words presented in the left, right, or central visual fields. Interference patterns indicated that the left hemisphere automatically transforms graphemes into phonemes (Experiments 1 and 2), whereas the right hemisphere processes vowel diacritics as visual objects (Experiment 1), although it possesses some phonological categories (Experiment 2). The significance of these findings for models of visual word recognition in the cerebral hemispheres is discussed.

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Why is it important?

Although both hemispheres are sensitive to visual and phonological aspects of graphemes, there are clear differences in the relative weights given to these aspects in the two hemispheres. Our results support the hypothesis that each of the hemispheres contributes to normal reading via a different neural network (Peleg et al., 2005). In the LH network, the representations of orthographic, phonological, and semantic information are highly interconnected, whereas in the RH network, orthographic and phonological representations lack connectivity but are connected with semantic representations. Indeed, our results showed that the LH automatically computes graphemes as phonological information, whereas in the RH, graphemes are primarily processed as visual forms. Nevertheless, the RH possesses some phonological information about these graphemes, most probably because it is able to categorize orthographic information according to phonological principles (via semantic/categorical representations).