Yale Bulletin and Calendar

October 11-18, 1999

Volume 28, Number 8

Scientists unraveling building blocks of memory

New findings by Yale researchers have brought scientists one step closer to understanding why people have fleeting memories of some events, yet remember other incidents for a lifetime.

The research, which looked at how learning and memory affects the way nerve cells communicate, was published in the Sept. 18 issue of the journal Science by Professor Thomas Carew and co-researcher Carolyn Sherff.

"Our work provides clues into the puzzle of how a nervous system 'decides' to move a memory from a short term state into more permanent storage," explains Carew, professor of psychology and molecular, cellular and developmental biology. "This gives us further insights into the basic building blocks of memory -- insights into the highly conserved cellular and molecular rules that nature has evolved to enable experience to change neurons in a permanent way."

The focus of the study, he says, was a specific set of connections between brain cells. The scientists examined whether different kinds of information coming to different parts of the neuron can interact to induce a long-term memory.

"We asked whether a signal carried by the neurotransmitter serotonin to the neuron which arrives at the cell body (soma) of a neuron or at its synapse will induce a long-term change," Carew says. "We found if the signals coincided, in time a long-term change in the strength of the synapse was induced."

Neurons have the genetic machinery for encoding long-term events located in their nucleus, which is in the soma of the cell. The synaptic outputs are where neurons talk to each other, and these can be located at quite a distance from the soma.

The researchers found the signals arriving at the soma and the synapse had to occur within 15 minutes of each other for a long-term change to occur, explains Carew. In addition, he notes, the signals at the two sites had different molecular requirements: The signal at the synapse required the synthesis of new protein immediately, whereas the signal at the soma needed new protein synthesis too, but not until three hours later.

"It was not previously appreciated that sites quite far away from each other could, in real time, interact and be partners in the induction of long-term changes in the neuron accompanying memory," Carew says. "Now the question is: What is the nature of those signals? What is going on inside the neuron? Who are the proteins and what are they doing?"

The biggest surprise, says Carew, was how easy it was to induce events dependent on protein synthesis locally at the synapse.

"There is no genetic machinery (DNA) at the synapse, so local protein synthesis requires that previously existing messenger RNA already has to be there. This mechanism provides a stockpile of messages from DNA that have already been transcribed (into RNA) and are waiting at the synapse to be translated into proteins locally and rapidly," Carew says.

-- By Jacqueline Weaver

T H I SW E E K ' SS T O R I E S

The Yale Endowment reaches $7.2 billion

'Yale Nursing Matters' magazine debuts at YSN

Yale's Year 2000 Project is preparing campus for the new millennium

As population grows to 6 billion, Yale expert warns of future scarcity

Alumnus actor says of his craft, 'You have to be a sponge'

Yale completes self-study as part of reaccreditation process

Award-winning journalist Roger Simon to visit as Poynter Fellow

Scholar will offer 'personal response to philosophy' in Terry Lectures

Scientists unraveling building blocks of memory

Exhibit features 'treasures' from the Lewis Walpole Library

Symposium pays tribute to noted Brazilian writer Haroldo de Campos

Sneak previews now part of the cinematic fare at Yale Film Society

Seminars examine genocides by Nazis and Cambodians

Yale Concert Band's first show of the season features film scores

Historian is next speaker in book review series

. . . In the News . . .