Serge CHARPAK, Institut de la Vision, Sorbonne Université, Paris has given a talk on Zoom on November 21th.
https://www.institut-vision.org/fr/departement-traitement-information-visuelle.html
Short abstract:
In the brain grey matter, synaptic activation produces a local increase of blood flow with a delay of about one second. For more than 20 years, a continuous controversy has suggested that prior to the increase of blood flow, the oxidative metabolism triggered by postsynaptic potentials and firing results in a rapid decrease of tissue oxygenation. The oxygen initial dip has initially raised the hope that it could be used to improve the spatial resolution of BOLD fMRI. It than faded away as the dip seemed to depend on the animal observed and the experimental conditions. I will describe our approach to track the oxygen initial dip using two-photon fluorescence and phosphorescence microscopy in the rodent olfactory system. I will show the conditions under which synaptic activation by a selective odor can generate the O2 dip in the rodent olfactory bulb.