New research suggests that the formation of memory may be the result of pairing stimulation in a certain region of the brain with a sensory experience.
A team of scientists from the University of California found that by activating the nucleus basalis — a neuron-filled part of the brain believed to modulate the brain's interpretation of sensory information — while playing a particular sound, they could alter the neuronal response to the tones in rats. They said this finding may be a key to understanding memory formation.
Previous research has shown that the sensory cortex, the part of the brain responsible for receiving and interpreting information from the senses, has a plastic quality, which allows it to reorganize itself in response to important experiences.
"In this way, cortical representations of the sensory environment can incorporate new information about the world, depending on the relevance of value of particular stimuli," the study explained.
For their experiment, the researchers played tones of different frequencies in a "pseudo-random" sequence to adult rats. The cortical neurons reacted equally to all the tones. Then, they played a tone repetitively for two to five minutes and electrically stimulated the nucleus basalis.
The scientists said the stimulation caused a reduction in the inhibition of nerve cells in the rats' auditory cortex and reshaped it to be more sensitive to the particular tone.
"Although nucleus basalis was stimulated only for a few minutes, reorganization of synaptic tuning curves progressed for hours thereafter: inhibition slowly increased in an activity-dependent manner to rebalance the persistent enhancement of excitation, leading to a retuned receptive field with new preference for the paired stimulus," the report said.
These changes may lead to further understanding how sensory memories are formed, the scientists said.
The period of sensitivity, the report explained, "may be a fundamental mechanism for receptive field plasticity, and could serve as a memory trace for stimuli or episodes that have acquired new behavioural significance."
The research will be published in this week's edition of the journal Nature.
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