Introducing the brain: memory formation (Introduction)

by David Turell , Tuesday, March 08, 2022, 00:35 (773 days ago) @ David Turell
edited by David Turell, Tuesday, March 08, 2022, 00:47

New studies on epileptic patients with implants:

https://www.newscientist.com/article/2311077-special-brain-cells-may-signal-when-to-sta...

"A newly discovered kind of brain cell involved in memory formation seems to mark the boundary between distinct events as we experience them.

"The neurons, which have been called boundary cells, fire when new events happen, such as if we see someone walking into a room.

"The cells were discovered in people with epilepsy who had electrodes put into their brain before surgery, by asking them to watch films showing sequences of events.

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"In the latest study, Rutishauser’s team asked 19 such people to watch carefully constructed film sequences while the recording took place, listening to about 30 cells per person.

"About 7 per cent of the neurons were boundary cells, whose firing peaked when new things happened. “They don’t say anything about the memory content, they just say there is a boundary,” says Rutishauser. He speculates that activity in these cells signals that the brain should begin to form a new memory, like starting a new folder.

"When people were tested later by showing them pictures from the films, they were better at remembering scenes from straight after a boundary than those that had happened a few seconds later.

"The findings “make a lot of sense”, says Rodrigo Quian Quiroga at the University of Leicester, UK. “They suggest a mechanism by which the hippocampus is signalling what scenes to put together and what scenes not to put together.”

"Boundary cells haven’t been seen before because previous work in people with electrodes implanted before epilepsy surgery used memory tests involving words or still pictures, not films, says Rutishauser."

Comment: the hippocampus is the memory control center, but memory gets scattered all around the brain shown previously here. second article with more richer info.

https://www.sciencealert.com/neuroscientists-find-two-types-of-brain-cells-that-help-us...

"Similar to how we perceive objects and entities in the world, our memories have clear boundaries, and in the new study, neuroscientists ask if the neurophysiological formation of memories reflects the discrete character of memories in our conscious experience.

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"With their consent, epilepsy patients often take part in neuroscientific studies due to these useful intracranial electrodes. They allowed investigators to record the activity of individual neurons while patients viewed film clips with 'cognitive boundaries'.

"While these boundaries in our daily lives may be nuanced and less obvious, scientists, for research purposes, focused on what they called 'hard' and 'soft' boundaries.

"'An example of a soft boundary would be a scene with two people walking down a hallway and talking, and in the next scene, a third person joins them, but it is still part of the same overall narrative," said Ueli Rutishauser, a neurosurgeon at Cedars-Sinai hospital, interim director of the Center for Neural Science and Medicine, and co-author of the study.

"'The difference between hard and soft boundaries is in the size of the deviation from the ongoing narrative. Is it a totally different story, or like a new scene from the same story?"

Researchers were able to find two types of cells that responded to these cognitive boundaries: 'boundary cells', that responded to both soft boundaries and hard boundaries, and 'event cells' that responded solely to hard boundaries.

"Rutishauser and his team believe that when the activity of event and boundary cells peak, after a hard boundary when both cells fire, the brain enters the state of initiating a new memory.

"'A boundary response is kind of like creating a new folder on your computer," said Rutishauser.

"'You can then deposit files in there. And when another boundary comes around, you close the first folder and create another one."

"When the brain needs to revisit a memory, it uses the peaks of neural activity at these boundaries to find the right folder.

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"'Together, these findings suggest that boundary and event cells play two roles in episodic memory; they structure memories during encoding, and they serve as markers for periods of time that are later reinstated," say the authors.

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"...event cells appear to help us establish the temporal order of our memories, whereas the boundary cells are more involved in recognizing the content of memories."

Comment: second story richer. It shows our brain is designed with neurons with specific functions for future use.