A new perspective published in Nature Reviews Neuroscience suggests that acetylcholine, a key chemical messenger in the brain, may play a central role in how the hippocampus learns to predict future events.
Researchers propose that acetylcholine release in the hippocampus could function as a signal for “state transition prediction errors”, differences between what the brain expects to happen and what actually occurs. This framework may provide a unifying explanation for acetylcholine’s previously separate roles in novelty detection, uncertainty processing, memory formation and attention.
The authors suggest that hippocampal theta sequences, patterns of neural activity linked to memory and navigation, may help generate these prediction signals. In this view, acetylcholine could regulate changes in neural connections, allowing the brain to refine its internal model of the world.
“Acetylcholine has been linked to so many different brain functions — novelty, attention, uncertainty, memory — that it has been hard to see what ties them together. We propose they are all the same underlying computation: acetylcholine signals when the world doesn’t unfold the way the brain predicted, prompting it to update its internal model. This might explain how we remember things that surprised us but forget the mundane — like whether we remembered to lock the door this morning. This change in perspective could reshape how we understand memory, and what starts to fail early in Alzheimer’s disease,” said Will de Cothi, lead author of the perspective and a researcher in the Barry Lab, UCL Department of Cell and Developmental Biology.
The proposal builds on predictive models of brain function, where neural systems are understood as continuously forecasting environmental changes and updating those predictions through experience. The researchers compare acetylcholine’s proposed role in structural learning with dopamine’s established role in reward prediction and value learning.
The perspective highlights a possible new way to understand how chemical signalling, neural circuits and memory interact, while pointing to future experiments needed to test whether acetylcholine truly serves as a predictive learning mechanism in the hippocampus.