From ScienceDaily:
The researchers discovered a traveling spike generator that appears to move across the hippocampus — a part of the brain mainly associated with memory — and change direction, while generating brain waves. The generator itself, however, produces no electrical signal.
“In epilepsy, we’ve thought the focus of seizures is fixed and, in severe cases, that part of the brain is surgically removed,” said Dominique Durand, Elmer Lincoln Lindseth Professor in Biomedical Engineering at Case School of Engineering and leader of the study. “But if the focus, or source, of seizures moves — as we’ve described — that’s problematic.”
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The team is also trying to understand what these non-synaptic events do and whether they are relevant to processing neural activity. Because the speed of these waves is close to the speed of sleep and theta waves, the researchers speculate they may be involved in consolidating memory. More.
Here’s the abstract:
Electrical activity in the brain during normal and abnormal function is associated with propagating waves of various speeds and directions. It is unclear how both fast and slow traveling waves with sometime opposite directions can coexist in the same neural tissue. By recording population spikes simultaneously throughout the unfolded rodent hippocampus with a penetrating microelectrode array, we have shown that fast and slow waves are causally related, so a slowly moving neural source generates fast-propagating waves at ~0.12 m/s. The source of the fast population spikes is limited in space and moving at ~0.016 m/s based on both direct and Doppler measurements among 36 different spiking trains among eight different hippocampi. The fact that the source is itself moving can account for the surprising direction reversal of the wave. Therefore, these results indicate that a small neural focus can move and that this phenomenon could explain the apparent wave reflection at tissue edges or multiple foci observed at different locations in neural tissue. (paywall) – M. Zhang, R. S. Shivacharan, C.-C. Chiang, L. E. Gonzalez-Reyes, D. M. Durand. Propagating Neural Source Revealed by Doppler Shift of Population Spiking Frequency. Journal of Neuroscience, 2016; 36 (12): 3495 DOI: 10.1523/JNEUROSCI.3525-15.2016
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