How the Brain's Overstuffed Filing System Fails

Age is not entirely to blame for forgetfulness.

The reason that some people are absentminded and others have minds like a steel-trap might have more to do with how the brain files memories and makes room for new ones, new research suggests.

The overstuffed file system that collects daily to-do's while keeping track of childhood memories has remained an enigma, especially regarding the mechanism for such mega-bit storage amidst the deluge of incoming bytes.

Every minute, sensory data enters your brain in the form of electrical signals that jet from neuron to neuron via intersections called synapses. Scientists think memories form when this communication between brain cells increases.

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In order to seal in a memory, chatter amongst bystander neurons needs to quiet down. Referred to as long-term depression (LTD), the process is akin to shushing cubicle mates so you can better hear a phone conversation.

"This is a normal process that helps with the sculpting of memory," said Thomas Foster of the McKnight Brain Institute of the University of Florida. "After all, we do not remember everything in perfect detail and we would not want to."

Foster and his colleagues trained aged and young rats to find a hidden platform and climb out of a pool of water, a task the rats learned quickly. They noted which rats showed superior memory and which had sluggish recall.?

Then, the researchers anesthetized the rats and applied a weak electrical signal to their synapses to make them less sensitive and to depress cell-to-cell communication. Both old and young rats with the highest memory scores were more resistant to the electrical interference than the other rats.

The aged animals that showed impaired memories prior to analysis were much more susceptible to the electrical signals and had excessive long-term depression. In human terms, not only would your co-workers get quieter, the caller would too.

"When we see someone we know or perhaps even ourselves becoming more forgetful, we now know that this is not an inevitable process," Foster said.

In excess, the memory-boosting process can actually lead to forgetfulness as too many brain-cell links get weakened or quieted, as is seen during brain aging, the scientists suggest in their study report published this month's online edition of the journal Neurobiology of Learning and Memory.

Further studies of how memory works could help scientists find ways to postpone or alleviate age-related forgetfulness, Foster said.