Summary: Forming long-term memories demands a large and sustained supply of energy in neurons. New research shows that modestly extending mitochondrial calcium retention — by reducing the activity of the LETM1 protein that exports calcium — can safely prolong ATP production and substantially improve long-term memory formation after a single training session in both fruit flies and mice.
Neurons rely on ATP produced by mitochondria to support the biochemical processes of memory consolidation. When neurons are active, calcium rises inside the cell and a fraction of that calcium is taken up by mitochondria. Mitochondrial calcium stimulates the Krebs cycle and increases ATP synthesis, matching energy supply to neuronal demand.
Key Facts
- Energy and memory are linked: Long-term memory consolidation is metabolically expensive. Increasing ATP production in neurons enhances the capacity to form durable memories.
- Role of LETM1: LETM1 is a mitochondrial inner-membrane protein that helps export calcium from the mitochondrial matrix. Reducing LETM1 expression slows calcium efflux, lengthening the period during which mitochondria produce extra ATP.
- Single-session memory formation: In both Drosophila and mice, this controlled metabolic boost enabled animals to form long-term memories that persisted beyond 24 hours after only one learning trial — a result normally requiring repeated training.
- Specific effect on long-term memory: Middle-term memory was not improved, indicating the extra energy specifically benefits the energetically demanding process of permanent consolidation.
- Conserved mechanism: LETM1 is present across eukaryotes, suggesting this metabolic strategy for optimizing memory may be evolutionarily conserved and potentially relevant to humans.
Source: Paris Brain Institute
The brain is one of the body’s most energy-intensive organs. Every time we think, plan, or form new memories, neurons fire and consume ATP produced by mitochondria. The brief influx of calcium following neuronal activity accelerates mitochondrial metabolism, increasing ATP production to meet these demands.
“The entry and exit of calcium within mitochondria allow energy production to be finely tuned to the demands of brain activity,” explains Jaime de Juan-Sanz, head of the PreSyn team at the Paris Brain Institute.
Previous work largely examined how decreased neuronal energy impairs synaptic transmission. This collaborative study — involving teams at the Paris Brain Institute, ESPCI Paris, Hospital del Mar Research Institute (Barcelona), the Institute of Science and Technology (Vienna), and the Max Planck Florida Institute for Neuroscience — took the opposite approach: could modestly increasing mitochondrial calcium and ATP production boost brain function beyond baseline?
How the team retained mitochondrial calcium
The researchers targeted LETM1, a mitochondrial protein that mediates Ca2+ export. By partially knocking down LETM1 in neuronal models and in specific memory circuits of live animals, they slowed mitochondrial calcium extrusion after stimulation. This prolonged metabolic stimulation without producing toxic calcium overload, resulting in an extended window of elevated ATP production.
“What makes this approach particularly interesting is that it amplifies a physiological signal without pushing mitochondria into harmful calcium levels,” says Jaime de Juan-Sanz.
Behavioral experiments showed clear benefits. In fruit flies, a single pairing of an odor with a mild punishment normally yields only short-lived avoidance lasting a few hours. When LETM1 expression was reduced in mushroom body neurons — the center for olfactory memory — a single training session produced a memory that lasted more than 24 hours. Similar Pavlovian-style conditioning in mice produced comparable improvements in long-term memory retention.
Selective enhancement of consolidation
Importantly, the manipulation did not enhance middle-term memory, which indicates the extra mitochondrial energy is deployed specifically for the demanding biochemical processes required to stabilize memories permanently. The effect’s presence in both flies and mice suggests an evolutionarily conserved mechanism that shapes higher brain functions by tuning mitochondrial metabolism.
Implications and limits
These results imply that slightly increasing the energy available to neurons can enhance certain aspects of long-term memory. The findings raise the possibility that controlled metabolic boosts could one day improve cognitive endurance or help conditions where energy supply or mitochondrial function is compromised.
However, practical application is distant. The current study used genetic tools to reduce LETM1, and LETM1 dysfunction is linked to human disorders such as Wolf-Hirschhorn syndrome. Any therapeutic strategy would need precise control to avoid harmful side effects. Future work should develop tools that can modulate mitochondrial calcium with high spatiotemporal precision — for example, optogenetic approaches — to assess how far memory consolidation can be safely enhanced.
Key Questions Answered:
A: Not at present. This research relied on genetic manipulation to inhibit LETM1. While it demonstrates that the brain has an untapped capacity for optimization, there is no safe, proven pill or supplement that replicates these effects in humans today.
A: Consolidating a memory into a long-term trace requires sustained biochemical effort and ATP. Repetition signals that an experience is important, triggering repeated metabolic investment. The study shows that supplying extra mitochondrial energy can substitute for repeated reinforcement in certain contexts.
A: Potentially. If safe methods to boost neuronal energy are developed, they might benefit conditions where impaired energy metabolism contributes to memory loss. More research is needed to explore therapeutic possibilities and safety.
Editorial Notes:
- Edited by a Neuroscience News editor.
- Journal paper reviewed in full.
- Additional context provided by staff.
About this memory research news
Author: Marie Simon
Source: Paris Brain Institute
Contact: Marie Simon – Paris Brain Institute
Image: Image credited to Neuroscience News
Original Research: Open access. “Mitochondrial Ca2+ efflux controls neuronal metabolism and long-term memory across species” by Anjali Amrapali Vishwanath et al., published in Nature Metabolism. DOI: 10.1038/s42255-026-01451-w
Abstract
Mitochondrial Ca2+ efflux controls neuronal metabolism and long-term memory across species
Across species, forming long-term memories increases metabolic activity in stimulated neurons to meet energetic demands. While reduced neuronal metabolism impairs brain performance, whether expanding neuronal metabolic capacity can boost brain function has been unclear. This study shows that reducing the mitochondrial Ca2+ exporter Letm1 favors Ca2+ retention in the mitochondrial matrix of neurons, over-activating mitochondrial metabolism in central memory circuits and improving long-term memory storage in training paradigms where wild-type animals fail to remember. These findings reveal an evolutionarily conserved mechanism by which mitochondrial metabolism in neurons shapes higher brain functions like long-term memory.