Event-related potentials correlate with task-dependent glucose metabolism

Abstract

Cognitive processing is associated with brain electrical activity that is reflected in event-related potentials (ERP). ERP during a target detection task, and regional cerebral glucose metabolism (CMRglc) measured simultaneously, may be influenced by the same neurophysiologic processes. We tested the hypothesis that ERP factors could be directly correlated with CMRglc to derive functional brain maps of brain activity at 120, 160, 200, 280, and 400 ms following stimulus presentation in a target detection task. We controlled for the potential confounding effects of age, sex, and task accuracy, and correlate target-related and nontarget-related ERP separately. Increases and decreases in CMRglc at each time point were identified with statistical parametric mapping (P < 0.001, uncorrected). The 120- and 160-ms maps were the same for target and nontarget processing, while maps for 280 and 400 ms clearly distinguished between targets and nontargets. Extrinsic (early) cognitive processes that depend mainly on stimulus characteristics show less variation based on stimulus meaning (i.e., letter vs shape; target vs nontarget) than later (intrinsic) cognitive processes. These early effects are lateralized to the left hemisphere, for negative ERP factors, and positive ERP-PET correlations are more likely than negative ERP-PET correlations. Thus, brain areas related to task processing impact both ERP and CMRglc measures, suggesting a shared neurophysiologic mechanism for negative ERP factors and increased CMRglc. Direct statistical analysis of these two measures using statistical parametric mapping provides high spatial and temporal resolution in multisubject experiments, while requiring only a single (18)FDG PET scan per subject.