Why dreams are hard to remember.

I remember my dreams pretty well. Last night, in fact, I dreamt of San Pedro. It all seems like yesterday, not far away... tropical the island breeze, all of nature wild and free....

By listening in on the chatter between neurons in various parts of the brain, researchers from the California Institute of Technology (Caltech) have taken steps toward fully understanding just how memories are formed, transferred, and ultimately stored in the brain--and how that process varies throughout the various stages of sleep.

Their findings may someday even help scientists understand why dreams are so difficult to remember.

Scientists have long known that memories are formed in the brain's hippocampus, but are stored elsewhere--most likely in the neocortex, the outer layer of the brain. Transferring memories from one part of the brain to the other requires changing the strength of the connections between neurons and is thought to depend on the precise timing of the firing of brain cells.

"We know that if neuron A in the hippocampus fires consistently right before neuron B in the neocortex, and if there is a connection from A to B, then that connection will be strengthened," explains Casimir Wierzynski, a Caltech graduate student in computation and neural systems, and first author on the Neuron paper. "And so we wanted to understand the timing relationships between neurons in the hippocampus and the prefrontal cortex, which is the front portion of the neocortex."

More here.