Tracking functions of cortical networks on a millisecond timescale

The human cerebral cortex, consisting of six layers and billions of neurons and synapses, processes sensory input from numerous sensory receptors. Non invasive magnetoencephalographic (MEG) recordings provide a view through th e skull to electrophysiological signals of the cortex on a millisecond time scale. For example, magnetic somatosensory evoked fields (SEFs) to a given peripheral somatosensory stimuli, reflect sequential activation of an exten sive cortical network. Several cortical areas contributing to the SEFs can be evaluated in time and space by using source modeling. This brief review focuses on MEG studies of the human somatosensory networks with a special e mphasis on tactile stimulation. (C) 2000 Elsevier Science Ltd. All rights r eserved.