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posted by martyb on Wednesday December 01 2021, @11:07AM   Printer-friendly
from the perchance-to-dream? dept.

Biomedical engineers find neural activity during rest is highly organized:

UNIVERSITY PARK, Pa. — When mice rest, individual neurons fire in seconds-long, coordinated cascades, triggering activity across the brain, according to research from Penn State and the National Institutes of Health. Previously, this was thought to be a relatively random process — single neurons firing spontaneously at random times without external stimulations.

The finding, published Nov. 18 in the Proceedings of the National Academy of Sciences, was made in rodents, but may have implications for better understanding neural activity in humans — especially in elucidating cognitive decline, according to first author Xiao Liu, assistant professor of biomedical engineering and faculty co-hire in the Institute of Computational and Data Sciences.

During rest, the brain appears to restore itself: the hippocampus consolidates memories, while cerebrospinal fluid washes through neural tissue, refreshing the mind. The mechanisms of the apparent tidying and cleaning are not well understood, however.

“Single neurons fire in a highly organized manner as seconds-long cascade events in the resting state,” Liu said. “It’s not random noise. We expected to find neurons firing with some organization during the resting state, but we didn’t expect such a highly organized pattern of activity with the involvement of so many neurons.”

The researchers analyzed a public dataset collected by the Allen Institute. Allen Institute scientists recorded neuronal “spikes” — electrical impulses to transmit information across the brain — of hundreds of neurons in resting and active rodents. They also measured pupil changes and body movements. Overall, Penn State researchers focused their analyses on the individual dynamics of about 10,000 neurons from 44 different brain regions in 14 rodents.

The rodents were analyzed during periods of rest, when their bodies were still; however, it was not known whether the animals were sleeping or simply resting, as they sleep with their eyes open, according to the researchers.

Liu and his team analyzed the frequency of spontaneous spiking activity in fixed time intervals at low frequency. They observed that 70% of the recorded neurons, regardless of brain region or origin, participated in recurring, sequenced cascades of global brain activity lasting five to 10 seconds. The cascade was typified by sequential activations from a group of neurons more active during rest to another group that exhibited more intense spiking during active movement.

Journal Reference:
Xiao Liu, David A. Leopold, Yifan Yang. Single-neuron firing cascades underlie global spontaneous brain events [$], Proceedings of the National Academy of Sciences (DOI: 10.1073/pnas.2105395118)


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  • (Score: 0) by Anonymous Coward on Wednesday December 01 2021, @05:45PM

    by Anonymous Coward on Wednesday December 01 2021, @05:45PM (#1201191)

    The same thing we do every night, Pinky. Now that we got help from our bat friends...

  • (Score: 2) by JoeMerchant on Wednesday December 01 2021, @07:43PM (2 children)

    by JoeMerchant (3937) on Wednesday December 01 2021, @07:43PM (#1201236)

    My understanding (limited, as is the best understanding of the premier experts in the field) of brain activity is, basically, chaos good, monotonic repetitive activity bad. Even heart rate is expected to vary, not only with lung tidal volume but also due to other interactions. Lack of heart rate variability is associated with diabetes and other not so good conditions. Extreme repetitive activity in the brain is, of course, a hallmark of epileptic seizures, not only grand-mal seizures with spasticity, foaming at the mouth, etc. but also absence seizures which can present as a complete lack of responsiveness, or partial loss of cognitive function during the seizure activity.

    So, these (normal?) mice have organized rhythmic brain waves during rest. It would be more surprising if there were no activity at all, but in a simple system there may not be enough interaction to breed large scale chaotic activity.

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    • (Score: 2) by Immerman on Wednesday December 01 2021, @10:48PM (1 child)

      by Immerman (3985) on Wednesday December 01 2021, @10:48PM (#1201297)

      Aren't most non-REM stages of human sleep characterized by large-scale rhythmic brain waves? Presumably it's either accomplishing something, or is the result of core neural paths (loops?) in "idle mode".

      As I recall, brain cells shrink slightly when in (non-REM) sleep, allowing cell wastes to get squeezed out from between cells and along the outside of veins by your pulse. Which is necessary since the lymphatic (waste disposal) system doesn't extend into the brain - perhaps because of space constraints, or to reduce potential infection paths.

      It wouldn't surprise me at all to learn that the electrical activity during different stages of sleep performs some similar function. Perhaps restoring baseline neurotransmitter balances in the synapses? Re-balancing oscillator circuits? I don't know enough to do more than speculate wildly,

      • (Score: 2) by JoeMerchant on Thursday December 02 2021, @01:16AM

        by JoeMerchant (3937) on Thursday December 02 2021, @01:16AM (#1201331)

        I worked with a neurologist with a PhD in neuroscience from Harvard. While he, and his colleagues, know a lot about the brain, a lot more than the average bear, he would be the first to tell you that he and his colleagues are still mostly pulling the big conclusions out of their asses. The data is sparse, the variability is high, and most of what they know they have learned from the seriously diseased population.

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