Recent advances in MEG studies of the human somatosensory cortex: noninvasive monitoring of cortical plasticity

Abstract

There have been converging lines of evidence that horizontal collateral fibers of pyramidal cells and inhibitory interneurons in the cortex play important roles in cortical plasticity. In this review article, I will present data suggesting that the activity of the two above neural elements can be recorded noninvasively with magnetoencephalography (MEG). First, I will discuss that fast-spiking GABAergic inhibitory interneurons in area 3b generate somatic high-frequency oscillations (300–900 Hz) to an electrical stimulation of the median nerve. Second, I will describe that horizontal fibers of the pyramidal neurons in area 3b mediate sequential activation of pyramidal cells in layer 3, which is visualized by the dynamic movement of equivalent current dipole (ECD) sources of N20m primary response. These results suggest that the process of cortical reorganization can be monitored by measuring MEG in real time. Finally, I will stress that the above findings were made possible for the first time noninvasively by magnetic recordings, opening up a new area of brain research.