Callosal function in dyslexia: Evoked potential interhemispheric transfer time and bilateral field advantage

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Abstract
Recent research has implicated inefficient interhemispheric communication via the corpus callosum as a factor associated with some forms of dyslexia. This study investigated callosal function in 21 dyslexic participants and 21 controls through measurement of interhemispheric transfer time derived from visual evoked potentials recorded during a letter‐matching task. Interhemispheric collaboration in dyslexia was also explored through measurement of a processing advantage for bilateral versus unilateral visual field presentations. Results revealed faster evoked potential interhemispheric transfer time in normal participants than in dyslexic participants. Letter‐matching performance data yielded no significant group differences in bilateral field advantage, although dyslexic participants made significantly more errors and were slightly slower than controls. The interhemispheric transfer time data support the hypothesis of less efficient callosal function in dyslexic individuals.