According to a theoretical physics paper published in Physical Review Letters, biological memory operates on a strict energy budget that forces organisms to switch abruptly between utilizing past information and ignoring it entirely. Kobayashi found that when environmental resources are scarce, the optimal strategy for an organism is to discard memory processing and rely solely on immediate sensory input.
The Energy Cost of Storing Information
Storing information requires a constant supply of metabolic energy, whether that data sits in a complex human brain, a bacterial signaling network, or cellular proteins. According to Tottori and Kobayashi, the biological bill for memory must be paid constantly. Their mathematical model charges organisms for two distinct factors: the distance an estimate lands from the actual truth, and the metabolic work required to maintain that memory against internal noise.
Turning fleeting sensory impressions into lasting memories demands significant energy surges at neural synapses. Because mitochondria supply this fuel unevenly across brain tissue, different anatomical regions afford varying levels of retention. When resources fall below a critical threshold, the optimal amount of memory storage drops to zero. According to Tottori, resources dictate an abrupt shift rather than a gradual transition.
“When resources are scarce, the best strategy is to ignore memory and react only to current information. But once enough resources become available, remembering suddenly becomes worthwhile, causing an abrupt shift to a memory-based strategy.”
Takehiro Tottori, Institute of Industrial Science and RIKEN
How Environmental Uncertainty Drives Memory Use
The model reveals that memory pays off best when senses operate under moderate unreliability. If incoming data is completely crisp, internal memory adds nothing that current readings do not already provide. Conversely, if signals are hopelessly noisy, storing them merely fills internal pathways with garbage. Tottori and Kobayashi found that energy availability, memory pricing, and internal noise collapse into a single ratio that dictates this operational boundary.
Did You Know?
Biological computation is distributed unevenly across lifeforms. While some systems get by on reflexes, human brains operate close to the physical limits of their available energy supply.
This mathematical threshold matches experimental data from human subjects. A 2022 study tracking volunteers making inferences under varying levels of uncertainty showed that participants leaned heavily on working memory during moderate uncertainty while abandoning it at both extremes. Furthermore, volatile environments that change rapidly push both models and human subjects toward memoryless strategies.
Neural Circuitry and Evolutionary Implications
While the mathematical model assumes simplified Gaussian noise and quadratic costs, its implications stretch deep into evolutionary biology. Memory-based estimation in the model closely resembles coherent feed-forward loops, which pair fast direct pathways with slow indirect ones. These structural loops appear overrepresented in actual gene networks and neural circuits.
According to Tetsuya J.
“These results help explain why organisms do not always use memory, even when it could in principle improve their decisions. Whether memory is useful depends not only on the resources available, but also on environmental uncertainty.”
Tetsuya J. Kobayashi, University of Tokyo
Reflex-driven organisms survive on minimal energetic investment, whereas memory-hungry brains evolved specifically where environments were uncertain enough to reward the high cost of holding onto the past.
Frequently Asked Questions
Why is biological memory considered energetically expensive?
Maintaining information over time requires constant cellular work and synaptic energy supplied by mitochondria, imposing a metabolic cost regardless of whether the memory is stored in a brain, bacteria, or single-cell proteins.
Do humans really abandon working memory under high uncertainty?
Yes. Experimental data from 2022 shows that human volunteers lean on working memory during moderate uncertainty but abandon it when signals are either excessively crisp or hopelessly noisy.
What determines whether an organism uses memory?
According to the research by Tottori and Kobayashi, memory utility is governed by a strict ratio between available metabolic resources, the cost of holding information, and the level of environmental volatility.
Explore More: Dive deeper into biological discoveries and evolutionary science by exploring our latest research updates on Earth.com, or download the EarthSnap app to track environmental changes in real time.
Worth a look