Saron and Davidson (1989) and (Patston et al., 2007) observed faster transfer from right-to-left hemisphere for similar stimuli. The microstructural underpinnings of these IHTT asymmetries are unclear and represent a point of contention in the literature. Marzi (1991), for example, has argued that these asymmetries are underpinned by differences in the number of corpus axons projecting from the left hemisphere to the right and vice versa. In contrast, both Braun (1992) and Nowicka, Grabowska and Fersten (1996) have suggested that while both hemispheres contain comparable numbers of fast and slow-conducting callosal fibers, the brain has evolved to ensure “the fast transmission of information to the hemisphere which is more efficient in its processing [of the particular stimulus]” (Nowicka, Grabowska and Fersten, 1996, p147). Regardless of their physiological bases, the asymmetric IHTTs observed in the present study provide further evidence that cerebral lateralization is not limited to language-related functions, but instead occurs in a variety of sensorimotor and cognitive processes.
