40 Hz audiovisual stimulation: Can a sensory rhythm rewire the ageing brain?

Why does the brain lose its rhythm as we age? It is a question of timing as much as biology. We typically view the ageing mind as a machine in inevitable decline, where parts wear out and the static takes over. But what if the machinery is largely intact, simply waiting for a specific frequency to restart the production line?

New research suggests this might be the case, at least in mice. The focus is on 40 Hz audiovisual stimulation, a non-invasive technique involving flickering lights and rhythmic sounds. While it sounds like a disco effect, the biological impact is precise. In models of Alzheimer’s, this frequency has previously shown promise in clearing proteins associated with the disease. Now, we are seeing it might do something even more constructive: build new brain cells.

The mechanics of 40 Hz audiovisual stimulation

In this study, scientists looked at the dentate gyrus of middle-aged mice. In a standard ageing brain, neurogenesis—the birth of new neurons—sputters to a halt. The control animals confirmed this grim reality; their few newborn cells were stunted, failing to grow or connect. They were ghosts in the machine.

The treated mice, however, told a different story. The sensory stimulation appeared to shift the chemical balance, encouraging neural progenitor cells to proliferate. More importantly, these cells did not just appear; they survived. They grew complex dendritic trees and developed axons with large mossy terminals. This is the difference between planting a seed and watching a forest take root.

The study measured increased spiking capacity and synaptic activity, proving these new neurons were not just structural ornaments but functional members of the circuit. The researchers identified TrkB signalling as the molecular driver behind this remodelling. While we must be careful not to conflate a mouse’s hippocampus with human complexity, the findings are striking. They suggest that the healthy ageing brain retains a plasticity we assumed was lost, accessible perhaps not through a pill, but through the eyes and ears.