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Chasing Memory / First of four parts

One man's epic quest for understanding

What happens when we encounter a new experience that enables us to recall it later at will? And what goes wrong when we can't? Gary Lynch has spent decades seeking the answers.

August 19, 2007|Terry McDermott | Times Staff Writer

That reorganization, in turn, strengthened the connection between cells; networks of those neurons with strengthened connections constituted the underpinning of memory.

When Lynch had originally proposed this sort of rapid structural change at synapses, many in the field were skeptical. Eventually, most researchers came around to the view that some sort of structural change occurred, but it was taken more as a matter of faith. Even many who believed the structural rebuilding occurred thought newly synthesized proteins from the cell nucleus had to be sent to the synapse to do it, and they spent an awful lot of time looking for those proteins.

Lynch thought it would take too long for the proteins to be manufactured in the cell nucleus; events were already underway, and the material needed to complete the job was on hand.

Imagine a construction crew framing a building. If the protein synthesis believers were right, the carpenters would have to call a warehouse every time they needed a nail. Lynch proposed that the crew had the nails right there in their belts. This experiment was intended to provide proof.

For The Record
Los Angeles Times Sunday, August 26, 2007 Home Edition Main News Part Page News Desk 2 inches; 81 words Type of Material: Correction
"Chasing memory": The glossary accompanying the Aug . 19 memory article in Section A defined genes as "strings of amino acids that make up an organism's genome, a sort of blueprint from which the organism is built. Individual genes are strings of amino acids; each string contains instructions for building a particular protein." The definition should have said: "Genes: strings of DNA that form a blueprint from which the organism is built. Each gene contains instructions for building a particular protein."

"We're in the penumbra, the shadow land," Lynch said. "And now comes the moment of moments."

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terry.mcdermott@latimes.com

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Glossary of terms

Actin: A protein that forms a critical part of the interior scaffolds that give cells their external shape. Think of the internal tubing that supports a tent. From the outside, you see only the tent's fabric, but its shape is determined by the interior scaffold. Actin changes form slightly and is said to be polymerized once it has formed the scaffold.

Ampakine: A class of drugs designed to enhance communication between brain cells. The drugs, still in development, will enhance almost all cognitive activities if they work as envisioned.

Cerebral cortex: The "gray matter" of the mammalian brain; the topmost part of the human brain wherein complex functions such as memory, learning and thinking are located.

Dendrite: A fiber that extends in bunches from a neuron. Dendrites receive signals from another sort of fiber called an axon. Dendrites and axons meet at the synapse.

Genes: Strings of amino acids that make up an organism's genome, a sort of blueprint from which the organism is built. Each gene contains instructions for building a particular protein.

Hippocampus: A structure near the center of the brain in mammals, including humans, that is involved in memory, learning, timing and spatial awareness, among other functions.

LTP, or long-term

potentiation: The strengthening of connections between brain cells that occurs when they communicate, making subsequent communication more efficient. The communication consists of electrochemical exchanges between two neurons at the synapse, which is where they meet.

Neuron: The most common type of cell in the brain (numbering in the hundreds of millions); LTP occurs between two neurons.

Neurotransmitter: Molecules that are released from an axon across the synapse to a dendrite's receptor. Specific neurotransmitters pair with specific receptors.

Protein: Molecules that perform most of the work within cells. Each protein's composition, and thus function, is dictated by a gene.

Receptor: A molecule on the surface of a cell that acts as a sort of docking station for other molecules, including neurotransmitters.

Synapse: The point where two neurons communicate in the brain. It is actually not a structure but a gap of about 20 nanometers (20 billionths of a meter) across which one neuron sends chemical signals that are received by the other. The chemicals set off cascades of events inside the receiving neuron. There are estimated to be from 100 trillion to 10 quadrillion synapses in a human brain, allowing for immense memory capacity.

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About this series

Today: After decades of work, Gary Lynch, a UC Irvine neuroscientist, prepares a series of experiments he hopes will show how memories form.

Monday: Testing the hypothesis. Things in Lynch's lab go haywire. Tuesday: The lab begins an

unparalleled run of success.

Wednesday: The culmination. Can an actual memory inside the brain be seen?

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