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Tuesday, December 25, 2007

How does memory stick

How can we remember things facts even whole scenes. The most important part of the brain for memory is the hippocampus. This hippocampus exists of neurons or brain cells. These brain cells communicate with their neighbors by sending a chemical burst from the tips of these spines, across a space called the synapse to the tip of a spine on the next cell. If the chemical bath is strong enough, the receiving spine bulges forward — strengthening the connection between the spines. This is thought to be the fundamental process underlying learning.

In a recent article in Scientific American: Signaling Neurons Make Neighbor Cells "Want In", a recent discovery about memory is explained.

A new discovery about the function of neurons could help scientists understand how the brain assembles information during learning and memory formation.

Scientists have found that when electrical impulses are passed from one neuron to another, they not only strengthen the synapse (connection) between them, but they also give a boost to neighboring synapses, priming them to learn more quickly and easily.

In The New York Times:Brain Cells, Doing Their Job With Some Neighborly Help, it is explained how the researchers can watch a synaps in action.
The ability to watch a synapse in action is itself a scientific accomplishment. The average human brain has about 100 billion neurons, and about 1,000 times that many synapses. To zero in on a single one, the researchers used mice that were genetically engineered so their brains produced a fluorescent protein that glowed only in specific cells of the hippocampus. Peering through a high-powered microscope at a slice of this tissue, the researchers could zero in on a single synapse.

In another article in Scientific American:Sleep, Attention, and Memory it is explained why sleep is so important for memory and the hippocampus.
For years scientists have known that sleep is necessary to focus attention on a task, whether you're trying to learn something or not. Specifically, sleep deprivation leads to reduced activation of attentional networks in the frontal and parietal lobes across a range of cognitive tasks. In addition, executive function tasks, thought to be mediated by prefrontal cortex, show greater deficits after a night of sleep deprivation than do other cognitive tasks, such as perceptual and memory tests.

They showed that if you are sleep-deprived there is significantly less activity in the hippocampus.
Moreover if you are well rested there is a stronger coupling between the hippocampi and other structures normally associated with episodic memory processing, including other areas in the medial temporal lobe. If your not well rested the hippocampus will need a tighter coupling with basic alertness networks in the brainstem and thalamus. In order to remember things the not well rested sleepy subjects required activation of the hippocampus together with basic arousal circuits.

Not well rested subject need to crank up their arousal circuits along with their hippocampi. They seem to do so at the expense of other circuits that are normally involved in encoding new memories.

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