Time-frequency analysis of slow cortical activity and cardiovascular fluctuations in a case of Alzheimer's disease.

The dynamics and relationship of slow cortical activity (amplitude modulation of electroencephalograph at 0.02-0.05 Hz) and cardiovascular fluctuations (0.01-0.05 Hz range) was studied by time-frequency mapping (modified Wigner distribution) in a patient with Alzheimer's disease. The amplitude modulating at rest basal alpha and theta activity (lead Oz) was exaggerated compared with control subjects. Fluctuations at respiratory and nonrespiratory (0.01-0.05 Hz) frequencies in R-R intervals and blood pressure were present and within normal range. Spontaneous hypotension (by 20 to 80 mmHg lasting 15-20 s) accompanied by cardioacceleration occurred repeatedly in the supine position and during hyperventilation. Slow cortical activity and nonrespiratory fluctuations (0.01-0.05 Hz) in blood pressure increased concurrently with hypotensions. No signs of peripheral autonomic dysfunction or malfunction of baroreceptors were observed and the vasomotor instability appeared to be of central origin. The results suggested that slow cortical activity was functionally related to the central autonomic nervous system and reflected cortico-thalamo-brainstem interaction.