Morphometrical asymmetries and tractography of speech-relevant cortex in relation to language lateralisation and rapid temporal processing

Differences in the functional roles of the left and right cortices for speech-related processes have been known since the findings of Broca [1] and Wernicke [2]. Nearly 100 years later anatomical asymmetries of speech-related cortex was emphasised as a potential substrate to such functional lateralisations [3]. Exploration of associations of anatomical asymmetries and functional lateralisations in speech has since continued, with developing technologies and theoretical insights mutually affording increasingly refined understandings. The present study is another such continuance; we outline and report associations of neuroanatomical (morphometrical) and connective (diffusion tractography) measures of speech-related cortex with differences of participant speech lateralisation and rapid temporal acuity (a hypothesised general auditory ability that contributes to superior speech processing). Review and support of developments in methodological approaches to morphometry and tractography to are also provided. Overall, our study affirms complex and selectively overlapping relationships of anatomy and connectivity (especially in the planum temporale) with behavioural language lateralisation and the processing of rapid temporal acoustics. Implications, limitations, and recommendations are discussed.