Scientists have found why we remember the smallest of details of an episode even after a long period of time.
"Our finding explains, at least partially, why seemingly irrelevant information like the color of the shirt of an important person is remembered as vividly as more significant information such as the person's impressive remark when you recall an episode of meeting this person," said Susumu Tonegawa at MIT's Picower Institute of Learning and Memory.
One theory is that memory traces are distributed throughout the brain as biophysical or biochemical changes called engrams.
The MIT study explored neurons' branch-like networks of dendrites and the multiple synapses within them.
Neurons sprout dendrites that transmit incoming electrochemical stimulation to the trunk-like cell body.
The MIT researchers found that a minor detail's memory may get linked to long-term memory if two synapses on a single dendritic arbor are stimulated within an hour and a half of each other.
"A synapse that received a weak stimulation, the kind that would normally accompany a short-term memory, will express a correlate of a long-term memory if two synapses on a single dendritic branch were involved in a similar time frame," said Arvind Govindarajan, assistant director of the RIKEN/MIT Center for Neural Circuit Genetics.
This occurs because the weakly stimulated synapse can steal or hitchhike on a set of proteins synthesized at or near the strongly stimulated synapse.
"Not all irrelevant information is recalled, because some of it did not stimulate the synapses of the dendritic branch that happens to contain the strongly stimulated synapse," concluded Picower Institute postdoctoral associate Inbal Israely.
The work is slated to appear in the Jan. 13 issue of Neuron.