Figure 5.

Hypercapnia attenuates spontaneous resting MEG fields. A: Spectral power in each of six subjects is plotted against frequency from 5 to 50 Hz. Power is generally greater under normocapnia in most subjects and frequencies, with most variability in the alpha band. During this recording, subjects were resting quietly in a quiet room and may have experienced different levels of alpha activity. The gamma band is indicated by the light gray box. B: Power is averaged across subjects for each frequency band, as indicated. Hypercapnia attenuated power in all bands (theta by 7%, alpha by 15%, beta by 10%, and gamma by 11%) but only the gamma decrease was significant (paired t‐test, two‐tailed P < 0.02). C: Spectral power was measured in 40 sensors at the top of the head (white box) where contamination with EMG was not a concern.