Voluntary breath holding affects spontaneous brain activity measured by magnetoencephalography.

Spontaneous brain activity was measured by multichannel magnetoencephalography (MEG) during voluntary breath holds. Significant changes in the activity are limited to the alpha rhythm: 0.25 Hz frequency increase and narrowing of the peak. The area of alpha activity shifts slightly toward (fronto-) temporal. The topography of other rhythms is unaffected by breath holding. Electroencephalographic (EEG; 36 channels maximal) recordings generally made simultaneously with the MEG recordings show similar effects. However, EEG was inadequate to reveal the small topographic differences. Systemic hypercapnia caused by a long breath hold is unlikely to play an important role in producing the observed effects.