Experimental increase of blood glucose alters resting state EEG measures of excitation-inhibition balance.

Walker, Christopher P; Buse, John; Frohlich, Flavio

NEW FINDINGS What is the central question of this study? Glucose is the dominant energy source for the brain. However, little is known about how glucose metabolism impacts the coordination of network activity in the brain in healthy adults. What is the main finding and its importance? We demonstrate that both alpha oscillations and the aperiodic signal components of resting electroencephalography are both modulated by experimentally elevated blood glucose levels. Our findings suggest that glucose increases measures associated with excitation-inhibition (E:I) balance, but that the effect on alpha oscillations may plateau at a certain level. Understanding the relationship between glucose consumption and E:I balance is critical to developing our understanding of how metabolism shapes human brain activity. ABSTRACT Brain network oscillations can broadly be divided into periodic and aperiodic signal components which are sensitive to state-dependent changes in network coordination and excitation to inhibition (E:I) balance. We sought to address whether the brain's dominant energy source, glucose, is implicated in regulating network activity and excitability. We conducted an experimenter-blind, crossover study of the effect of blood glucose level (BGL) on the resting electroencephalography (EEG) frequency spectrum. Participants consumed a glucose drink (75 g glucose) or an equivalent volume of water on two separate visits. EEG data were sampled before and up to three hours after the drink. We found the experimentally induced changes in BGL exhibited an inverted u-shaped relationship with changes in the individual alpha frequency peak, whereas the slope of the aperiodic signal component of the frequency spectrum showed a positive linear association suggestive of greater excitation. By contrast, peak alpha power-typically associated with top-down inhibitory processes-was negatively associated with changes in BGL. Collectively these results suggest that high BGL alters brain network coordination in the form of alpha oscillations and measures associated with E:I balance. This article is protected by copyright. All rights reserved.