Hancock, R. & Bever, T.
University of Arizona
Five decades of experimental, clinical and neuroimaging results demonstrate the cognitive and scientific importance of differentiating right-handed subjects with familial sinistrality (FS+) from those without (FS-). We present new fMRI and EEG evidence that lexical processing is faster and more bilaterally organized in FS+ subjects than in FS- subjects, while there is little difference in syntactic processing. P600 amplitudes are also mediated by familial sinistrality in a word probe task, suggestive of a sequential/lexical vs integrative/syntactic processing distinction. We suggest a neurocomputational model of dynamic instability in the corticostriatal loop as an explanation for this genetically-linked variability in language processing and other cognitive traits linked to personal and familial sinistrality. Preliminary data from non-linguistic behavioral and EEG studies support this model, revealing that FS+ subjects switch between bistable visual percepts (e.g. Necker cube perspectives) more rapidly than FS- subjects, and also show reduced alpha power suppression and make more commission errors in a go-nogo task, two measures thought to be linked to chemical disregulation of the corticostriatal system.