Although sporadic, a steady stream of research has focused on the noted differences in the size and shape of the dyslexic corpus callosum (CC). The CC is a central nerve bundle that allows communication between the right and left lobes of the brain. Because it is so integrally involved in interhemispheric communication, researchers believe that any significant malformities of the CC could lead to serious disruptions in the processing of sensory information.
The evidence implicating the CC, however, is often conflicting and confusing. One study, for example, reports that children with dyslexia have abnormalities in the corpus callosum. The results, however, show no particular trend -- many of the dyslexic children had either an undersized or oversized corpus callosum (Njiokiktjien et al.,1994). Other studies which have found that the anterior region of the genu of the corpus callosum in dyslexics is significantly smaller than normal (Hynd et al., 1995), are only followed by studies which show that the posterior region is significantly larger and the only CC region affected (Rumsey et al., 1996).
In addition to possible size differences, other experimental evidence suggests that dyslexics have a thicker corpus collosum. This research suggests that increased thickness prevents neurons from making the appropriate connections across the CC, inhibiting right hemispheric competence and impairing reading abilities (Njiokiktjen et al., 1993). Analyzing this information, it becomes clear that researchers studying the corpus callosum have been left in a precarious position. While at once they face evidence too interesting to ignore, they are also left only with results still too rudimentary to draw conclusions.
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