Introducing the brain: keeping track of the body (Introduction)

by David Turell , Saturday, November 09, 2019, 19:33 (1839 days ago) @ David Turell

We are compartmentalized the brain too much new research shows:

https://www.quantamagazine.org/noise-in-the-brains-vision-areas-encodes-body-movements-...

"At every moment, neurons whisper, shout, sputter and sing, filling the brain with a dizzying cacophony of voices. Yet many of those voices don’t seem to be saying anything meaningful at all. They register as habitual echoes of noise, not signal; as static, not discourse.

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"Now, by analyzing both the neural activity and the behavior of mice in unprecedented detail, researchers have revealed a surprising explanation for much of that variability: Throughout the brain, even in low-level sensory areas like the visual cortex, neurons encode information about far more than their immediately relevant task. They also babble about whatever other behaviors the animal happens to be engaging in, even trivial ones — the twitch of a whisker, the flick of a hind leg.

"Those simple gestures aren’t just present in the neural activity. They dominate it.
The findings are changing how scientists interpret brain activity, and how they design experiments to study it.

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"Kenneth Harris and Matteo Carandini, neuroscientists at University College London, started with a different goal: to characterize the structure of the spontaneous activity in the visual cortex that occurs even when the rodent gets no visual stimulation. They and other members of their joint team at the university’s Cortexlab recorded from 10,000 neurons at once in mice that were free to act as they wanted — to run, sniff, groom themselves, glance around, move their whiskers, flatten their ears and so on — in the dark.

"The researchers found that even though the animals couldn’t see anything, the activity in their visual cortex was both extensive and shockingly multidimensional, meaning that it was encoding a great deal of information. Not only were the neurons chatting, but “there were many conversations going on at the same time,” wrote Marius Pachitariu, a neuroscientist at the Howard Hughes Medical Institute.

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“If we look at the mouse as a whole,” McCormick said, “all of a sudden, that general activity, that swirling kaleidoscope of activity in the brain, starts to make sense.” (He and his lab reported similar findings in a recent preprint.) The activity didn’t just reflect the general state of the mouse’s alertness or arousal, or the fact that the animal was moving. The visual cortex knew exactly what the animal was doing, down to the details of its individual movements.

"In fact, this wasn’t unique to the visual cortex. “Everywhere in the brain, it’s the same story. The movement signals are just really unmistakable,” said Matt Smear, a systems neuroscientist at the University of Oregon who did not participate in the study. It cements the idea that “certain intuitive notions about the brain are probably wrong.”

"Even more striking, the same neurons that encoded sensory or other functional information were the ones explicitly encoding these motor signals. “All of a sudden we’re saying, ‘Wait — maybe the brain isn’t noisy. Maybe it’s actually much more precise than we thought,’” McCormick said.

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"The movement signals therefore aren’t hurting the animal’s ability to process sensory information about the outside world. But scientists still need to explore exactly how those signals might help the brain work better. At its core, this discovery reflects the fact that fundamentally, the brain evolved for action — that animals have brains to let them move around, and that “perception isn’t just the external input,” Stringer said. “It’s modulated at least to some extent by what you’re doing at any given time.”

"Sensory information represents only a small part of what’s needed to truly perceive the environment. “You need to take into account movement, your body relative to the world, in order to figure out what’s actually out there,” Niell said.

“We used to think that the brain analyzed all these things separately and then somehow bound them together,” McCormick said. “Well, we’re starting to learn that the brain does that mixing of multisensory and movement binding [earlier] than we previously imagined.”

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“'People tend to think of movements as being separate from cognition — as interfering with cognition, even,” Churchland said. “We think that, given this work, it might be time to consider an alternative point of view, that at least for some subjects, movement is really a part of the cognition.”

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“'What we think of as being weird or unusual signals,” Niell said, “might start to make sense when you actually let an animal do what it would normally do, and not train the mice to be like little humans.'”

Comment: The brain knows everything going on. Experiment on unconstricted mice. Our brain is more than we knew.