Neuronal and vascular responses due to finger movements were synchronously measured using dc-magnetoencephalography (dcMEG) and time-resolved near-infrared spectroscopy (trNIRS). The finger movements were monitored with electromyography (EMG). Cortical responses related to the finger movement sequence were extracted by independent component analysis from both the dcMEG and the trNIRS data. The temporal relations between EMG rate, dcMEG, and trNIRS responses were assessed pairwise using the cross-correlation function (CCF), which does not require epoch averaging. A positive lag on a scale of seconds was found for the maximum of the CCF between dcMEG and trNIRS. A zero lag is observed for the CCF between dcMEG and EMG. Additionally this CCF exhibits oscillations at the frequency of individual finger movements. These findings show that the dcMEG with a bandwidth up to 8？Hz records both slow and faster neuronal responses, whereas the vascular response is confirmed to change on a scale of seconds. 1. Introduction The methodologies to characterize neurovascular coupling in humans [1] can be separated at least into two categories. The first relies on two sequential measurements of the same subject and infers coupling parameters, the second performs multimodal synchronous measurements of neuronal and vascular effects, and the coupling is observed directly. The second methodology is technically more complicated, but the effect of a subject’s performance changing between two measurements is eliminated. Furthermore it allows to study the coupling on continuous time series, that is, without relying on epoch averages removing the variability between individual epochs. Results from these approaches complement the detailed findings for neurovascular coupling obtained from invasive studies in animals [2]. One possibility to study neurovascular coupling by synchronous measurements was described in [3–5] combining dc-magnetoencephalography (dcMEG) with time-resolved near-infrared spectroscopy (trNIRS) during intermittent finger movements. These synchronous measurements were so far limited to a bandwidth from DC to 0.4？Hz due to the modulation technique used for the dcMEG [4]. With the possibility to obtain unmodulated dcMEG in a magnetically extremely shielded room [6, 7] the bandwidth of the synchronous measurements is considerably increased; that is, slow signal changes close to DC and standard neuronal responses above 1？Hz can be recorded at the same time. To keep in line with earlier literature the term dcMEG is maintained, but it denotes here a bandwidth of the
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