Combining noninvasive brain stimulation and neuroimaging to study human brain biology

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There are theories about how the brain works, but without having a way to change brain activity, we do not really know how to test those theories. We need tools for changing the function of the brain and seeing how that affects the behaviours to test those theories. Such tools are common in animal models (e.g., optogenetics), but not in human neuroscience. An approach that could test theories, noninvasively, on human causal brain-behaviour relationships would become fundamental in neuroscience. Transcranial current stimulation (tCS) combined with neuroimaging could become such cardinal tool. Previous studies reported that tCS can modulate human behaviours in vivo. However, due to its noninvasive quality, tCS alone does not show how it stimulates the brain when it modulates behaviours. We thus need to combine tCS with neuroimaging, such as magnetic resonance imaging (MRI), to develop methods that will reliably modulate specific brain networks. ******Our long-term NSERC supported program entails achieving the development of such brain tool that will permit testing theories on brain function, establishing brain-behavioural relationships. ******Thanks to previous Discovery grant, we developed an approach combining simultaneously tCS/resting state MRI. This method captures, in real time, the cause and effect evidence of tCS modulating the brain. As an example, we delivered tCS over the dorsolateral prefrontal cortex in healthy adults during resting state functional MRI (fMRI) as well as during MR spectroscopy. tCS modulated resting state functional connectivity, strengthening connectivity in the fronto-parietal network. Also, tCS elevated striatal glutamate and prefrontal NAA levels during stimulation. This work is among the first demonstrations that tCS modulates human brain substrates during MR acquisition which was published in a top journal in the field of brain biology and a Press Release (Hone-Blanchet, Edden, Fecteau, 2016 Biological Psychiatry).******The aim of this proposal is to pursue the development of this NSERC supported brain tool. We will develop methods that will reliably modulate specific networks (e.g., fronto-parietal, fronto-striatal network). In order to achieve this, we will develop methods combining simultaneously and subsequently tCS and MRI. We will investigate the main tCS types (direct current, tCDS; alternating current, tACS, random noise, tRNS) and MRI methods (fMRI, MRS, structural, tractography).