Effect of Muscimol on BOLD and Local Neuronal Activity in Awake Animals

Daniil P. Aksenov^1,2, Limin Li^1,2, Gheorghe Iordanescu^1,2, Xiaomu Song^1,2, Alice Wyrwicz^1,2

Many questions remain about the relationship between the local cellular metabolic and hemodynamic changes measured by fMRI and the underlying neuronal electrical activity. In this study we examined the effect of neuromediators on BOLD and neuronal activity. Simultaneous fMRI and electrophysiological measurements of whisker stimulation were performed before and after localized injection of the GABA agonist muscimol into the somatosensory cortex. The drug injection affected both neuronal activity and BOLD signal. However, surprisingly, the large reduction in single-unit activity produced by muscimol was accompanied by a relatively small change in BOLD response in the whisker barrel cortex.