Spring Break
Neurotransmitter pathway affects emotional memories
Issue date: 11/1/07
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How is that you can remember, in detail, your first day of school, but can't recall what you ate for breakfast this morning? New research from a group at Hopkins may provide the answer. Their study, published last month in Cell, shows that emotion enhances memory by means of a single molecule, norephineprhine, whose concentration in the brain increases during stressful situations.
Because the brain's memory-storage capabilities are finite, distinguishing between significant and insignificant memories is a biological necessity. Evolutionarily advantageous information should be given priority over less relevant facts - for example, the color of a poisonous berry compared to the color of a stranger's eyes.
It has been well-established that stress is a key factor enhancing learning and, subsequently, memory. (Once the vomiting and hallucinations are over, you'll likely remember that berry's color.) In some cases, the relationship between stress and memory can go awry, as in post-traumatic stress disorder. Generally though, it's effective in filtering out most of the trivial information that assails us each day.
At the cellular level, memory is nothing more than a strengthening, over time, of certain connections between neurons. Termed long-term potentiation, or LTP, there are various ways this can happen.
The most well-understood version occurs when a given neuron becomes more sensitive to signals - in the form of molecules called neurotransmitters - sent by a neighboring neuron. Primarily this involves increasing the number of neurotransmitter-specific receptors present at the synapse, the junction between two neurons where neurotransmitters are released and received.
Many scientists have hypothesized that stress somehow causes more receptors to be brought to the synapse during LTP and hence boosts retention of emotional memories. Nonetheless, until now the exact molecular mechanism has remained a mystery.
Several pathways have been proposed, and, while differing in their details, all start with one molecule: norepinephrine (NE). During stressful situations, neurons in the brainstem release NE into several other areas of the brain, including the hippocampus, the center of memory formation.
Because the brain's memory-storage capabilities are finite, distinguishing between significant and insignificant memories is a biological necessity. Evolutionarily advantageous information should be given priority over less relevant facts - for example, the color of a poisonous berry compared to the color of a stranger's eyes.
It has been well-established that stress is a key factor enhancing learning and, subsequently, memory. (Once the vomiting and hallucinations are over, you'll likely remember that berry's color.) In some cases, the relationship between stress and memory can go awry, as in post-traumatic stress disorder. Generally though, it's effective in filtering out most of the trivial information that assails us each day.
At the cellular level, memory is nothing more than a strengthening, over time, of certain connections between neurons. Termed long-term potentiation, or LTP, there are various ways this can happen.
The most well-understood version occurs when a given neuron becomes more sensitive to signals - in the form of molecules called neurotransmitters - sent by a neighboring neuron. Primarily this involves increasing the number of neurotransmitter-specific receptors present at the synapse, the junction between two neurons where neurotransmitters are released and received.
Many scientists have hypothesized that stress somehow causes more receptors to be brought to the synapse during LTP and hence boosts retention of emotional memories. Nonetheless, until now the exact molecular mechanism has remained a mystery.
Several pathways have been proposed, and, while differing in their details, all start with one molecule: norepinephrine (NE). During stressful situations, neurons in the brainstem release NE into several other areas of the brain, including the hippocampus, the center of memory formation.
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