Compelling new research, published in the journal Proceedings of the National Academy of Sciences, is suggesting neuronal activity in the hippocampus prior to the delivery of new information can enhance subsequent memory formation. The discovery points to a kind of "encoding mode" the brain enters in order to learn new information more effectively.
Prior brain imaging studies have effectively homed in on activity in the medial temporal lobe while a person is learning to gauge subsequent memory strength. But this new research set out to investigate whether brain activity prior to the presentation of stimuli could predict the strength of new memories formed.
The study examined 34 patients with epilepsy, measuring neural activity in four brain regions (hippocampus, amygdala, anterior cingulate, and prefrontal cortex) while they completed a word memory task. Each subject was presented with a continuous stream of words. For each word they had to decide whether it was novel or repeated. Initially every word was novel, but eventually most words would repeat.
The big finding from the study is that the cohort seemed to display significantly greater recognition of the repeated words when hippocampal neurons spiked in activity before seeing the words for the first time.
“If a person’s hippocampal neurons were already firing above baseline when they saw or heard a word, their brain was more likely to successfully remember that word later,” says Stephen Goldinger, an author on the new study.
While similar spikes in neural activity were also sporadically observed in the other three brain regions examined in the study before novel words were presented, the specific neuronal activity in those regions did not prove to be predictive of subsequent memory recall. Only when there was a spike in hippocampal neuronal firing, around one second before seeing a new word, did the researchers note heightened subsequent memory recall when the word was eventually repeated.
Spikes in neuronal activity in the hippocampus have traditionally been seen as reflective of general arousal and attention states. However, the researchers behind this new study suggest the observed activity in the experiments is indicative of a more novel state of highly specific brain activity they refer to as an “encoding mode”.
“‘Encoding mode’ is more than simply paying attention to the task at hand,” explains John Wixted, co-lead author on the new study. “It is paying attention to encoding, which selectively ramps up activity in the part of the brain that is the most important for making new memories: the hippocampus.”
Wixted suggests the big new unknown raised by this discovery is whether there is some way to stimulate activity in the hippocampus and trigger this “encoding mode.” If it could be artificially modulated then hypothetically one could significantly amplify memory retention and learning.
“A key question going forward is how to put our brains into ‘encoding mode’ when we wish to do so,” says Wixted. “Since we know, based on earlier research, that people can actively suppress memory formation, it might be possible for people to get their hippocampus ready to encode as well. But how one might go about doing that, we just don’t know yet.”
The new research was published in the journal PNAS.
Source: Arizona State University