Re: What electrochemical changes occurs in the brain cells after learning ?

Behrouz,

You have asked a question to which there is no easy answer. This is an active area of study for many researchers. It was once theorized that perhaps each memory was stored in a single distinct brain cell, but that is now known not to be true. Current theory holds that memories are essentially spread out through a network of interconnected neural cells. Each cell within this network contributes in a small manner to the storage of many memories. It is known that short-term memories are stored in an area of the brain called the prefrontal cortex. Long-term memories are stored in a part of the brain called the hippocampus. In general, individual memories are distributed throughout large regions of the brain, rather than localized in any one place.

As to how the memories are stored, that is another difficult question. Signals are transferred from one neural cell to another by a combination of electrical and chemical impulses. Within a single cell, the signal is transferred as an electrical signal. But at a synapse (the connection between two different neural cells) the cell releases a chemical, called a neurotransmitter, that crosses the small gap between the cells. A receptor on the second cell receives the chemical signal and converts it into an electrical impulse that can continue on within that second cell.

Some physical changes do occur in the brain as a memory is stored. As an individual performs a certain task (either a physical task such as shooting a basketball at a hoop, or a more intellectual task such as solving a math problem) new connections between the neural cells involved in learning that task are formed. So every time the task is repeated, there are more connections made within the neural network, and the brain gets better at performing that task. This is why you improve at something the more you practice doing it. It is also believed that memories are stored in part by slight changes in the strength of the connections (synapses) within the neural network. (If you are interested in this aspect, I would suggest looking up "long-term potentiation" on MadSci or by using your favorite web search engine.) Everyone's brain is continually undergoing these types of changes, and this is referred to as "neural plasticity." It has also been theorized that continual cycling of electrochemical signals throughout this network might be necessary to hold a memory.

These are simplified explanations of very complex biochemical processes, some of which are not fully understood yet. If you are interested in current research in this area, here are a few scientists who do research in this area:

H. Sebastion Seung and others at the Department of Brain and Cognitive Sciences, MIT
http://web.mit.edu/bcs/seung.html

Joe Tsien at Princeton
http://www.molbio.princ eton.edu/faculty/tsien.php

Also, I found this webpage with a detailed neurobiological explanation of memory from Jeffrey Clothier, MD
ht tp://www.uams.edu/department_of_psychiatry/syllabus/MEMORY/Mem97.htm