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fMRI and MEG

Magnetic Resonance Imaging (MRI) is a noninvasive medical imaging technique utilizing magnetic properties of atoms to register their spatial distribution inside the human body. The measurements result in sequences of two-dimensional images representing slices or sections through the head or body.

MagnetoEncephaloGraphy (MEG) is a non-invasive technique to measure the temporal variation of the magnetic field generated inside the head at the scalp (Fig. 1). These extraordinarily weak biomagnetic fields can be detected using Superconducting QUantum Interference Devices (SQUIDs) which need to be cooled using liquid helium. Measurements are performed inside a magnetically shielded room to suppress external perturbations due to cars, elevators, etc.

Each method by itself permits a detailed description of spatial (MRI/fMRI) or temporal (MEG) cerebral activation. However, each modality suffers from constraints. The spatial resolution of fMRI is high but the temporal resolution is limited due to haemodynamics (seconds). On the other hand, MEG has a high temporal resolution (milliseconds), but a limited spatial resolution. These limitations can be overcome by performing measurements using both modalities.

The advantages of both methods are combined in a present study examining the question whether the human brain follows a daily pattern of sequential phases in cognition. The master circadian pacemaker, the suprachiasmatic nuclei (SCN), emits signals that trigger organ-specific oscillators and, therefore, constitutes a basic biological process which enables organisms to anticipate daily environmental changes by adjusting behavior, physiology, and gene regulation. The SCN beats time for every cell in the human organism and, hence, for all human activities in the course of the day. While both the molecular basis of the circadian oscillation and its repercussions on peripheral physiological functions have been investigated in much detail, research on circadian regulation of central information processing is rare. On the other hand, there is mounting evidence that the circadian clock also controls the diurnal variation in higher cognitive functions.

fMRT&MEGAbb.1: Neuromagnetische Feldverteilung

Additional Information

Contact Person

Prof. N. Jon Shah, PhD

Frank Boers, Dipl.-Ing.

Jürgen Dammers, PhD

Andrea Muren