Towards a neurobiology of dysfunctional arousal in depression: the relationship between beta EEG power and regional cerebral glucose metabolism during NREM sleep

This study sought to clarify the neurobiological basis of variations in one aspect of central nervous system 'arousal' in depression by characterizing the functional neuroanatomic correlates of beta electroencephalographic (E EG) power density during non-rapid eye movement (NREM) sleep. First, nine h ealthy (n = 9) subjects underwent concurrent EEG sleep studies and [F-18]2- fluoro-2-deoxy-D-glucose ([F-18]FDG) positron emission tomography (PET) sca ns during their first NREM period of sleep in order to generate hypotheses about specific brain structures that show a relationship between increased beta power and increased relative glucose metabolism. Second, brain structu res identified in the healthy subjects were then used as a priori regions o f interest in similar analyses from identical studies in 12 depressed subje cts. Statistical parametric mapping was used to identify the relationship b etween beta power and relative regional cerebral glucose metabolism (rCMRgl u) during NREM sleep. Regions that demonstrated significant correlations be tween beta power and relative cerebral glucose metabolism in both the healt hy and depressed subjects included the ventromedial prefrontal cortex and t he right lateral inferior occipital cortex. During a baseline night of slee p, depressed patients demonstrated a trend toward greater beta power in rel ation to a separate age- and gender-matched healthy control group. In both healthy and depressed subjects, beta power negatively correlated with subje ctive sleep quality. Finally, in the depressed group, there was a trend for beta power to correlate with an indirect measure of absolute whole brain m etabolism during NREM sleep. This study demonstrates a similar relationship between electrophysiological arousal and glucose metabolism in the ventrom edial prefrontal cortex in depressed and healthy subjects. Given the increa sed electrophysiological arousal in some depressed patients and the known a natomical relations between the ventromedial prefrontal cortex and brain ac tivating structures, this study raises the possibility that the ventromedia l prefrontal cortex plays a significant role in mediating one aspect of dys functional. arousal found in more severely aroused depressed patients. (C) 2000 Elsevier Science Ireland Ltd. All rights reserved.