After four years of extensive lab testing and data analysis, researchers have found that the ACC (anterior cingulate cortex) plays a greater role in long-term memory retrieval than previously thought. Existing research has well established the process of consolidation -- the transference of memory dependence from the hippocampus to the ACC -- but what is not known is what happens when a person recalls that consolidated memory at a later date.

Animals are re-exposed to multiple environments at different retention intervals. During remote recall, ACC-CA1 theta coherence increases, with the ACC leading area CA1. ACC theta regulates unit spike timing, gamma oscillations, and ensemble and single-neuron information coding in CA1. Over the course of consolidation, the strength and prevalence of ACC theta modulation grow, leading to richer environmental context representations in CA1.

The research shows that brain waves between the ACC and the hippocampus become synchronized, with the ACC strongly influencing its counterpart when a memory is being recalled after a period of about two weeks. In long-term memory retrieval, their study finds that the hippocampus -- which is active when the memory first arrives in the brain -- becomes like the wooden toy Pinnochio, and now needs the ACC to operate its strings.

"This is a new mechanism for memory retrieval and a significant advancement in our understanding of how we recall the past," the senior author said. "It's very exciting because it opens up new windows into understanding how our brains process and access older memories, and could have implications for future studies."

The research was published in Cell Reports and the senior author believes it could have future implications for the treatment of Alzheimer's disease and other forms of dementia.

As patients transition from mild cognitive impairment to Alzheimer's, losing the ability to recall long-term memories is one of the hallmark symptoms.

"Our research opens up potential new avenues to explore why certain dementias and disorders lead to problems recalling long-term memories, which could help pave the way for future treatments that might be able to restore this ability to afflicted individuals," the senior author said.

https://www.cell.com/cell-reports/fulltext/S2211-1247(19)30560-1

http://sciencemission.com/site/index.php?page=news&type=view&id=publications%2Facc-theta-improves&filter=22