The unusual symmetry of musicians: musicians have equilateral interhemispheric transfer for visual information.

Previous behavioural research has shown that spatial attention is bilaterally represented in musicians, possibly reflecting more equal neural development between the hemispheres. We investigated this theory electrophysiologically with another measure that has shown asymmetry, interhemispheric transfer time (IHTT). Sixteen right-handed musicians and 16 matched non-musicians responded to stimuli presented to the left and right visual fields while 128-channel EEG was recorded. IHTT was calculated by comparing the latencies of occipital N1 components between hemispheres. Non-musicians showed significantly faster IHTT in the right-to-left direction than in the left-to-right direction and a shorter N1 latency in the left than in the right hemisphere. In contrast, the musician group showed no directional difference between hemispheres in IHTT, and no hemispheric difference in latency. These results indicate that musicians have more bilateral neural connectivity than non-musicians, reflected in an unusual lack of asymmetry. It is suggested that plastic developmental changes caused by extended musical training in childhood result in equally efficient connections to both hemispheres.