Localized brain metabolic response correlated with potentials evoked by words

Evoked potentials (EPs) measure synaptic current flows that propagate from brain to scalp, Alternatively, positron emission tomography (PET) using fluoro-deoxyglucose (FDG) can measure the increased glucose metabolism supporting this synaptic activation. It is difficult to localize the brain activity-generating EPs from their scalp distribution, because activity originating in different regions tends to produce overlapping scalp topographies. In contrast, FDG-PET provides better spatial resolution for activity throughout the brain, but shows only the total metabolism integrated over a 30-min uptake period. We combined the temporal and psychological resolution of EPs with the spatial resolution of PET to help define when and where in the brain words are encoded for meaning.