PT  - JOURNAL ARTICLE
AU  - Kimura, Tomoaki
AU  - Ozaki, Isamu
AU  - Hashimoto, Isao
TI  - Impulse Propagation along Thalamocortical Fibers Can Be Detected Magnetically outside the Human Brain
AID  - 10.1523/JNEUROSCI.3022-08.2008
DP  - 2008 Nov 19
TA  - The Journal of Neuroscience
PG  - 12535--12538
VI  - 28
IP  - 47
4099  - http://www.jneurosci.org/content/28/47/12535.short
4100  - http://www.jneurosci.org/content/28/47/12535.full
SO  - J. Neurosci.2008 Nov 19; 28
AB  - Orchestrating cortical network activity with synchronous oscillations of neurons across distant regions of the brain underlies information processing in humans (Knight, 2007) and monkeys (Saalmann et al., 2007; Womelsdorf et al., 2007). Frequencies of oscillatory activities depend, to a considerable extent, on the length and conduction velocity of the tracts connecting the neural areas that participate in oscillations (Buzsáki, 2006). However, the impulse propagation along the fiber tracts in the white matter has never been visualized in humans. Here, we show, by recording magnetoencephalogram (MEG) following median nerve stimulation, that a magnetic field component, we labeled “M15,” changes dynamically within 1.6–1.8 ms before the onset of magnetic M20 response generated from the primary somatosensory cortex. This new M15 component corresponds to the intracellular depolarizing action current in the thalamocortical fibers propagating with the mean conduction velocity of 29 m/s. The findings challenge the traditional view that MEG is blind to the activity of deep subcortical structures. We argue that the MEG technique holds the promise of providing novel information in impulse transmissions along not only the thalamocortical pathway but also other fiber tracts connecting distant brain areas in humans.