Exploring cortico-striatal connectivity across different domains of cognition combining TMS and fMRI

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Together, the frontal portion and the deep nuclei of the brain are involved in the control of movement as well as mental processes such as making decisions. These structures are often affected in different neurological and psychiatric disorders, including Parkinson's disease and schizophrenia. Our laboratory has developed tasks to tease apart the role of individual structures in these regions, using techniques such as functional magnetic resonance imaging (MRI). In particular, we were able to separate the functions of two sub-regions of the frontal lobe and the caudate nucleus (a deep structure of the brain) that are involved in executive processes. We have also developed tasks to distinguish the function of a more posterior region of the frontal lobe and the putamen, another deep brain structure, in the execution of movements. Until now, however, we have not been able to investigate how these different regions interact with each other during the performance of our mental and motor tasks. In the context of this proposal, we will be using a novel technique, transcranial magnetic stimulation (TMS), which allows us to stimulate or hinder the activity of specific portions of the outer brain during a short period of time, and investigate its effects on brain activity using functional MRI. In particular, we will investigate the effect of the stimulation of various regions of the frontal lobe on the patterns of activity observed in the deep structures of the brain while participants are either at rest, or while performing specific mental or motor exercises. The proposed mixture of TMS and functional MRI in the study of frontal lobe and deep brain structure interactions in healthy individuals is unique in Canada, and is invaluable in understanding the relationships and communication between these different regions. In the future, we will perform similar experiments with patients with Parkinson's disease, and apply our knowledge of processes in healthy participants in order to better understand the neural origins of the disease.