Australasian Science: Australia's authority on science since 1938

The Brain Is Strobing, Not Constant

A University of Sydney team has provided new evidence that sensory oscillations are a general feature of human perception.

It’s been known for some time that our visual perception is cyclical, but this is the first time it has been demonstrated for hearing, with the study published in Current Biology showing that sensitivity for detecting weak sounds is not constant but fluctuates through peaks and troughs at the rate of about six per second. “These findings are important as humans make decisions at the rate of about one-sixth of a second, which is in line with these auditory oscillations,” explained co-author Prof David Alais.

The study found a variation of oscillation between the two ears, with first one ear at peak sensitivity and then the other. The oscillation is so fast that we are normally unaware of it.

Why should the brain sample information in this cyclical fashion? One idea favoured by the authors of the study is that it reflects the action of attention, which appears to sample neural activity in rapid bursts.

When we peruse a scene, not all parts are equally important: some receive more attention than others and are prioritised in processing. This concentrates limited cognitive resources on specific items of interest rather than diluting resources over the entire space.

Similarly, oscillating attention would produce a similar result over time, with resources concentrated into small temporal epochs instead of being sustained in a uniform but superficial allocation. The strobing approach to attention would bind together relevant information at regular time points and allow new groupings of information to reassemble at other moments.

The research team will next focus its attention on how the sense of touch might make use of neural oscillations.