EEG Delta, Positron Emission Tomography, and Memory Deficit in Alzheimer’s Disease

Abstract

Quantitative scalp EEG from 32 channels and the cerebral glucose metabolic rate from the 32 underlying cortical positions as assessed by positron emission tomography (PET) with ¹⁸F-2-deoxyglucose (FDG) were obtained on 36 patients with mild to moderate senile dementia of the Alzheimer type and 17 age- and sex-matched normal control subjects. Subjects performed a verbal memory task during uptake of FDG. There were significant correlations between both delta amplitude and metabolic rate and memory performance during FDG uptake. Patients with Alzheimer’s disease had significantly greater left temporal delta amplitude and lower glucose metabolic rates. Both EEG delta in microvolts and metabolic rate had similar diagnostic sensitivity, but PET had fewer false positives among normals. The left amygdala had the highest sensitivity and percent correct diagnosis of any brain area. Temporal lobe EEG delta activity showed higher correlations with hippocampal metabolic rate than metabolic rate directly under the electrode.

Greater Metabolic Rate Decreases in Hippocampal Formation and Proisocortex than in Neocortex in Alzheimer’s Disease

“…Post hoc t tests revealed significant decreases in relative glucose metabolic rate in temporal Brodmann areas 22 and 35-36 and posterior cingulate area 23 in AD patients. In contrast, there was relative sparing of frontal, parietal and occipital areas, with AD patients demonstrating a significant increase in relative glucose metabolic rate in Brodmann areas 4, 10, and 18 as well as auditory cortex (41)(42). Comparison of MRI scans of areas 22 and 18 in the same subjects did not demonstrate significant patientcontrol differences.…”

“…Subjects were instructed on the task before the injection of FDG and were given practice trials to ensure their comprehension. Findings relating FDG uptake and task performance have been reported elsewhere [42].…”

“…All subjects fasted for at least 4 h before PET scanning. After injection of 4-5 mCi of FDG, subjects performed the task for 30 min [42]. Research assistants monitored task performance continuously to ensure that subjects were following instructions.…”

“…However, the cortical volumes assessed by PET were very large compared with the tissue sample counts, and the entire set of Brodmann areas was not sampled systematically. In an attempt to extend this important work, we used a template of Brodmann areas derived from a whole brain histological section atlas [41] to perform a more detailed analysis of a previously reported PET study of AD patients [42]. Our aim was to determine whether neuropathological changes in cytoarchitectural distinct brain regions observed in autopsy studies would be correlated with PET findings in matching brain regions.…”

Functional but not structural subgenual prefrontal cortex abnormalities in melancholia

“…47 Further, in patients with Alzheimer's disease 48 and vascular dementia, 49 inverse relationships between scalp-recorded delta activity and glucose metabolism or blood flow have been reported. In the present study, the inverse relationship between delta activity and glucose metabolism in the subgenual PFC strengthens the interpretation of an inhibitory role of delta.…”