DC-magnetoencephalography and time-resolved near-infrared spectroscopy combined to study neuronal and vascular brain responses.
The temporal relation between vascular and neuronal responses of the brain to external stimuli is not precisely known. For a better understanding of the neuro-vascular coupling changes in cerebral blood volume and oxygenation have to be measured simultaneously with neuronal currents. With this motivation modulation dc-magnetoencephalography was combined with multi-channel time-resolved near-infrared spectroscopy to simultaneously monitor neuronal and vascular parameters on a scale of seconds. Here, the technique is described, how magnetic and optical signals can be measured simultaneously. In a simple motor activation paradigm (alternating 30 s of finger movement with 30 s of rest for 40 min) both signals were recorded non-invasively over the motor cortex of eight subjects. The off-line averaged signals from both modalities showed distinct stimulation related changes. By plotting changes in oxy- or deoxyhaemoglobin as a function of magnetic field a characteristic trajectory was created, which was similar to a hysteresis loop. A parametric analysis allowed quantitative results regarding the timing of coupling: the vascular signal increased significantly slower than the neuronal signal.
Sander
T H
TH
Physikalisch-Technische Bundesanstalt, Abbestr. 2-12, 10587 Berlin, Germany. tilmann.sander-thoemmes@ptb.de
Liebert
A
A
Mackert
B M
BM
Wabnitz
H
H
Leistner
S
S
Curio
G
G
Burghoff
M
M
Macdonald
R
R
Trahms
L
L
D001921:Brain / Q000098:blood supply* / Q000502:physiology*; D006801:Humans; D015225:Magnetoencephalography / Q000379:methods*; D009474:Neurons / Q000502:physiology*; D019265:Spectroscopy, Near-Infrared / Q000379:methods*; D013997:Time Factors