Hyperventilation-induced human cerebral magnetic fields non-invasively monitored by multichannel 'direct current' magnetoencephalography.
Self-paced hyperventilation (HV) induces slow cerebral magnetic field changes which were monitored and mapped continuously over 15 min using 49-channel DC-coupled ('direct current') magnetoencephalography (DC-MEG) based on a modulation technique. In nine/nine healthy subjects HV caused an increase (range: 1.1-6.2 pT) of the mean global DC-MEG field strength which slowly decayed after HV termination (mean time constant: 2 min). The complex HV-related field patterns were distinctly different from mainly dipolar somatosensory evoked field maps (N20m) in four/four subjects. Thus, current sources in the primary somatosensory cortex need not regularly dominate DC-field changes as had been previously considered. Rather, DC-MEG enabled the monitoring of a widely distributed HV-induced enhanced cortical excitability which may serve as model to study epileptic or post-anoxic cerebral hyperexcitability.
Carbon
M
M
Neurophysics Group, Department of Neurology, Klinikum Benjamin Franklin, Freie Universität, Berlin, Germany. carbon@ukbf.fu-berlin.de
Wübbeler
G
G
Trahms
L
L
Curio
G
G
D000328:Adult; D004558:Electric Stimulation; D004569:Electroencephalography; D005073:Evoked Potentials, Somatosensory / Q000502:physiology; D005260:Female; D006801:Humans; D006985:Hyperventilation / Q000503:physiopathology*; D016857:Hypocapnia / Q000503:physiopathology; D015225:Magnetoencephalography; D008297:Male; D013003:Somatosensory Cortex / Q000502:physiology*