Asymmetrical Ability
Oliver Sacks (5 May 1995, p. 621) suggests that the development of exceptional musical abilities in individuals with neurodevelopmental disorders such as autism and William syndrome constitutes a "savant" talent and as such might represent a "neuromodule." He speculates that the exaggerated leftward asymmetry of the planum temporale area of the brain recently reported in a group of professional musicians by Gottfried Schlaug et al. (Reports, 3 Feb., p. 699) may reflect the neuromorphological substrate of such a neuromodule.
In fact, we have already carried out analyses of the planum temporale in individuals with Williams syndrome. The surface area of the left and right planum temporale of four subjects was measured with magnetic resonance images (MRI) using the same anatomical criteria employed by Schlaug et al. The planum temporale asymmetry for these individuals with Williams syndrome was on par with that of the group of musicians studied by Schlaug et al. (mean, -0.34; standard deviation, 0.14).
Three of the four individuals with Williams syndrome had greater asymmetry than that of the musicians, but less than that of musicians with perfect pitch. In contrast, five normal control subjects had an asymmetry coefficient that was consistent with the nonmusician control group in the study by Schlaug et al. study (mean, -0.23, standard deviation, 0.24). In addition, subjects with Williams syndrome did not differ from normal subjects in planum temporale surface area (1000.8 versus 962.1 square millimeters, respectively), despite significant overall reduction of cerebral volume reported in subjects with Williams syndrome (1), suggesting disproportionate growth of the entire posterior supratemporal region.
These preliminary data suggest that disproportionate growth, and perhaps exaggerated asymmetry, occur in the posterior supratemporal region in individuals with Williams syndrome. However, establishing whether this asymmetry is a source of musical ability will have to await more detailed analyses. Also, the fact that individuals with Williams syndrome typically possess exceptional language abilities relative to other cognitive domains and despite mental retardation (2) introduces the possibility that planum temporale asymmetry is related to linguistic abilities rather than, or as well as, musical abilities.