Temporal lobe anatomical connectivity

Brain function utilises processing networks to perform specific tasks. These networks require axonal connections (the brain's 'wiring') to allow information transfer between cortical and subcortical areas (the regions where information processing occurs). Knowledge of both the processing regions and the 'wiring pattern' is therefore crucial to allow full understanding of brain function. However, the knowledge of anatomical connections within the human brain is surprisingly poor, despite being an area of active research for over a century. An important reason for this uncertainty is that most methods available for establishing anatomical connection information are invasive and therefore impossible to apply in the living human brain. Whilst some dissection methods are suitable for postmortem investigation they are destructive and provide limited opportunity for the study of multiple tracts in a given brain, making them extremely costly in time and resources. An alternative non-invasive approach to identifying anatomical interconnections is via interpreting the effects of the functional and structural damage caused by lesions (such as those caused by multiple sclerosis or stroke). However, systematic connectivity studies are very difficult when relying on clinical lesion data. Diffusion weighted magnetic resonance imaging (MRI) provides the means for non-invasive systematic analysis of the white matter tracts of the human brain - a process termed tractography. This methodology has been developed over the last half decade to the point where it is being applied to provide new information regarding human brain anatomical connectivity and is therefore helping us establish the brain's 'wiring pattern'. This project will use tractography to establish the patterns of connection within the temporal lobes. The temporal lobes are an important study target as they are involved in much of the information processing capabilities that make the human species unique - for example, they are implicated in the understanding of language. We will study a group of healthy individuals to determine the variability of temporal lobe connections and to assess evidence for dominance of one hemisphere over the other. We will compare these results with established measurements in animal models to define which aspects of temporal lobe connectivity are unique to the human brain. We will make the results available on an online database that will allow the scientific community free access to this new and valuable store of information.

The aim of this study is to establish the degree of cross-species homology in white matter connections within and to/from the temporal lobes. We will use diffusion weighted MRI (DWI) to provide non-invasive probabilistic anatomical connectivity information in the human brain and compare this with connectivity information derived from animal models. High resolution postmortem DWI data will allow 'gold standard' comparison with literature and electronic database information regarding anatomical connectivity. This will be compared with DWI data acquired in vivo in a population of healthy brains to define the degree of population variability in temporal lobe connectivity and the experimental limits of in vivo DWI tractography. Cross-species homology will be investigated via a series of exemplar experiments. A significant additional end point will be the creation of an online database of temporal lobe anatomical connectivity, which will be made available to researchers, forming a unique and valuable resource for the neuroscience community.