Evaluation of the Severity of Dementia Using Expectation Control Function

The results of an animal experiment without anesthesia suggested the presence of expectation control in which sympathetic nerve tone increases at rest immediately before behaviors to prepare for the subsequent behavior. We investigated whether such function is present in humans in their daily living and whether patients with dementia could be differentiated from healthy adults based on this finding. Using a Holter electrocardiograph with an acceleration sensor, electrocardiograms (ECG) and behavioral states were recorded. The total recorded ECG was divided by 20 sec, and high (HF, 0.15–0.4 Hz) and low (LF, 0.03–0.15 Hz) frequency components were extracted by frequency analysis of the RR interval. We used the HF component, L/H ratio, and RR interval as the index grade of parasympathetic/sympathetic nerve tone. The mean value of each parameter was calculated and compared between the time zone during which resting persisted for 1 min or more (3 intervals) and that during which behaviors occurred immediately after a 1-min rest. In 32 patients with dementia, Holter ECG and behaviors were serially recorded, and the time zone during which intentional behaviors occurred was detected. RR interval and HF component decreased and L/H increased. Increasing in sympathetic nerve tone was observed at rest condition immediately before intentional behaviors, suggesting a presence of expectation control function. The expectation control mechanism will present inhumans and involved in this function by severity of dementia. This parameter may be useful for objectively evaluating the severity of dementia.