Answering a Century-Old Question: How do Brain Oscillations Emerge?

Amazing stuff!

"Key points

• Waves of synchronized, coordinated neuronal activity have been observed and studied in the brain for over a century.
• Gamma waves are altered in people with neurodevelopmental disorders, schizophrenia, and bipolar disorder, as well as neurodegenerative diseases.
• Yale researchers have now identified where gamma activity emerges and how it links to behavior.
• The findings could inform an interpretable early biomarker for Alzheimer’s disease.

... Pursuing this idea, the researchers recorded brain activity in 16 different sites in the visual cortex—the part of the brain that processes sight—in order to get a much more detailed look at the spatial and timing aspects of gamma activity. Then they broke down that data into individual events, much like one peak-trough-peak cycle of a wave.

If the gamma activity really was an oscillation, then putting each of these individual events together should look like a continuous wave that’s rolling through each of the spots where the researchers recorded.

“But it turned out that these events can happen together, or in little bursts, or all by themselves,” ... “They’re not happening in a long sequence.” ..."

From the abstract:

"Cognitive processes underlying behaviour are linked to specific spatiotemporal patterns of neural activity in the neocortex. These patterns arise from synchronous synaptic activity and are often analysed as oscillations, but may also display aperiodic dynamics that are not well detected.

Here we develop a novel analytical method decomposing patterned activity into discrete network events and use this approach to track gamma activity (30–80 Hz) in the mouse visual cortex (V1). We find that the gamma event rate varies with arousal and individual events can cluster in brief oscillatory bouts but also occur in isolation.

Individual events synchronize neural firing across layers and promote enhanced visual encoding.

V1 gamma events are evoked by patterned input from the dorsal lateral geniculate nucleus (dLGN) and suppressed by optogenetic modulation of the dLGN, suggesting that they support thalamocortical integration of visual information.

In behaving mice, the gamma event rate increases steadily before visually cued behavioural responses, predicting trial-by-trial performance. Suppressing V1 gamma events impairs visual detection performance, whereas evoking them elicits a behavioural response.

This relationship between gamma events and behaviour is sensory modality specific and rapidly modulated by changes in task objectives. Gamma events thus support a flexible encoding of visual information according to behavioural context."

Answering a Century-Old Question: How do Brain Oscillations Emerge? < Yale School of Medicine

Flexible perceptual encoding by discrete gamma events (open access)

Fig. 1: CBASS links state-dependent changes in gamma (30–80 Hz) activity to defined network events.