Introducing the brain: studies on memory (Introduction)

by David Turell , Thursday, May 23, 2024, 21:33 (32 days ago) @ David Turell

Resting ripples:

https://www.quantamagazine.org/electric-ripples-in-the-resting-brain-tag-memories-for-s...

"New studies from his lab and others have suggested that the brain tags experiences worth remembering by repeatedly sending out sudden and powerful high-frequency brain waves. Known as “sharp wave ripples,” these waves, kicked up by the firing of many thousands of neurons within milliseconds of each other, are “like a fireworks show in the brain,” said Wannan Yang, a doctoral student in Buzsáki’s lab who led the new work, which was published in Science in March. They fire when the mammalian brain is at rest, whether during a break between tasks or during sleep.

"Sharp wave ripples were already known to be involved in consolidating memories or storing them. The new research shows that they’re also involved in selecting them — pointing to the importance of these waves throughout the process of long-term memory formation.

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"In the late 1980s, researchers discovered that they could induce neurons to make stronger interconnections, linked to learning and memory, by artificially stimulating them to fire in rapid bursts. To Buzsáki, those bursts sounded a lot like his waves. In 1989, he first hypothesized that sharp wave ripples might be part of the brain’s mechanism for forming and consolidating memories.

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Buzsáki and other scientists discovered that the ripples seemed to replay brain activity from an animal’s experience, such as running through a maze — except that the replay ripples oscillated 10 to 20 times faster than the original signals. One 2002 paper, which “made sharp wave ripples very famous,” said Hiroaki Norimoto, a professor of neuroscience at Nagoya University in Japan, found that sharp wave ripples reactivate a sequence of neuronal activity.

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"In 2009 and 2010, two papers, including one led by Zugaro, showed that sharp wave ripples were involved in consolidating memories to endure over the long term. When researchers suppressed or disrupted the ripples, rats performed worse on memory tasks. “When you destroy them, then the animal no longer remembers,” Zugaro said. Later studies showed that elongating or creating more ripples improved rats’ memory.

"It became clear that the ripples were playing repeatedly to cement a memory. “The brain is rehearsing,” said Lila Davachi, a professor of psychology at Columbia University. “Even in these moments of wakeful rest, your brain continues to rehearse and replay the past.”

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"Sometimes the things we remember seem random or irrelevant, and surely different from what we’d select if given the choice. “There is a sense that the brain prioritizes based on ‘importance,’” Frank said. Because studies have suggested that emotional or novel experiences tend to be remembered better, it’s possible that internal fluctuations in arousal or the levels of neuromodulators such as dopamine or adrenaline and other chemicals that affect neurons end up selecting experiences, he suggested."

Comment: This is an extraordinary paper as it describes a brain as an organ that runs its own show. It actually decides what to record with what degree of importance to ascribe to it!! We own this brain, but unless we are consciously studying something to remember it is off on its own with rambling memories. Only design can create this.