Between two competing views, an agreement has been reached in general with regard to the synaptic origin of BOLD signals [17]. Hemodynamic responses are driven by metabolic energy demands, nearly all of which are imposed by synaptic activity instead of action potential firing [45, 46]. The observed correlation between the BOLD signal and the neuronal spiking rate [36, 37] might be owing to the fact that the pre-synaptic neuronal spiking activity is sometimes correlated with the synaptic current, as previously discussed in this review and elsewhere [46, 47]. However, when LFP and MUA are disassociated, the BOLD response is primarily correlated with LFP [41, 42].
