William Brandler

Will

The Genetics and Evolution of Cerebral Asymmetry

Approximately 90% of individuals are right-handed and there are no 
known populations in the world in which left-handers are the 
majority. Some other great apes show individual laterality for tool 
use, but there is no collective population bias. In most cases where 
individual apes show laterality, half the population favour the left 
hand, and half favour the right. So it would appear that a population 
bias in handedness is unique to humans among the great apes.

Handedness is correlated with cerebral asymmetries and right-
handedness implies a dominance of the left hemisphere for motor 
function. It has been proposed that handedness emerged as a 
consequence of the evolution of language. Functional brain imaging 
studies have shown a weak correlation between handedness and cerebral 
dominance for language; with 96% of strong right-handers, compared to 
73% of strong left-handers, showing left-hemisphere dominance for 
language. Also, there is suggestive evidence from structural brain 
imaging studies indicating that there may be atypical cerebral 
asymmetry in patients with neurodevelopmental disorders such as 
specific language impairment (SLI) or dyslexia.

Understanding the genetic basis of handedness can help define the 
relationships between handedness, language, cerebral asymmetry, and 
neurodevelopmental disorders. It may also offer us insights into 
human evolution, particularly with respect to language. It is with 
this in mind that we are performing a genome-wide association study 
for handedness in a sample of dyslexic children.

My DPhil is funded by the NDM Prize Studentship.

Publications

PCSK6 is associated with handedness in individuals with dyslexia. (2010) Scerri TS, Brandler WM, Paracchini S, Morris AP, Ring SM, Talcott JB, Stein J, Monaco AP. Hum Mol Genet. Nov 9. PMID: 21051773 [Epub ahead of print]