The effect of a serotonin-induced dissociation between spiking and perisynaptic activity on BOLD functional MRI.
The relationship of the blood oxygen-level-dependent (BOLD) signal to its underlying neuronal activity is still poorly understood. Combined physiology and functional MRI experiments suggested that local field potential (LFP) is a better predictor of the BOLD signal than multiunit activity (MUA). To further explore this relationship, we simultaneously recorded BOLD and electrophysiological activity while inducing a dissociation of MUA from LFP activity with injections of the neuromodulator BP554 into the primary visual cortex of anesthetized monkeys. BP554 is a 5-HT1A agonist acting primarily on the membrane of efferent neurons by potassium-induced hyperpolarization. Its infusion in visual cortex reliably reduced MUA without affecting either LFP or BOLD activity. This finding suggests that the efferents of a neuronal network pose relatively little metabolic burden compared with the overall presynaptic and postsynaptic processing of incoming afferents. We discuss implications of this finding for the interpretation of BOLD activity.
Rauch
Alexander
A
Max Planck Institute for Biological Cybernetics, Spemannstrasse 38, D-72076 Tübingen, Germany. arauch@tuebingen.mpg.de
Rainer
Gregor
G
Logothetis
Nikos K
NK
D000818:Animals; D008253:Macaca mulatta; D008279:Magnetic Resonance Imaging; D008297:Male; D010100:Oxygen / Q000097:blood*; D010775:Photic Stimulation; D010879:Piperazines / Q000494:pharmacology; D012701:Serotonin / Q000494:pharmacology*; D013569:Synapses / Q000187:drug effects*
D010879:Piperazines; D012701:Serotonin; C062718:BP 554; D010100:Oxygen