Genes 2 Brains 2 Mind 2 Me

Image via Wikipedia Brain images with red and yellow splotches of activity are now ubiquitous in the psychology literature and well on their way, via neuromarketing, to bamboozling consumers everywhere (eg. this splotch shows that 2/3 people really do prefer Pepsi !). When inappropriately used, fMRI methods can devolve quickly into a high-tech form of phrenology with concomitant hucksters (not unlike recent reports of consumer fraud in genetic testing) and, despite its ubiquity and potentcy as a research tool, the molecular basis for the fMRI signal has remained somewhat mysterious. Generally, when neurons fire, local blood-flow increases and the paramagnetic form of deoxyhemoglobin can be distinguished from the nonmagnetic oxygenated form using the electromagnetic scannner. Hence, splotches that indicate more blood flow (or Brain Oxygen Level Dependent – BOLD reponse) can be a proxy for neural activity. The connection between neuronal firing and blood flow, however, is not necessarily simple nor easily ignored. Amazingly, a recent report from Takano and colleagues, “Astrocyte-mediated control of cerebral blood flow” (DOI) shows that a single master regulatory gene, cyclooxygenase-1 (COX-1) is sufficient to regulate blood flow in response to neural activity. Takano and a team led by Maiken Nedergaard show that astrocytes have their hands wrapped around neural synsapses and their feet wrapped around capillaries. When the astrocytes sense synaptic firing (glutamate spillover) they signal to the capillaries and contractile pericyte cells to relax and vasodilate. Using a series of pharmacologic blockers, the team tested a number of candidate regulatory pathways and found that only COX-1 blockade affected vasodilation in response to neural activity. The work of this research team greatly improves the understanding of the fMRI method and provides a well constrained framework through which to understand fMRI data and, moreover, the interplay between brain imaging and genetic data. Hopefully the basic research will stay one step ahead of the hucksters.