Perception is highly selective; the brain constantly decides what information is important enough to reach our consciousness. An international team of researchers has now shed light on brain activities associated with subjective perceptual shifts, finding characteristic patterns of brain waves in the prefrontal cortex. Their findings could contribute to refining our understanding of consciousness.

What we see is not what we perceive: a large part of the sensory information that constantly arrives through our senses is never consciously processed. Complex mechanisms in the brain filter the incoming sensory information and shape the representation of the world in our minds. The phenomenon of binocular rivalry provides a prime example for this: when a rose is presented to the left eye and an apple to the right eye (which can be achieved via a setup of mirrors), we cannot perceive both objects at the same time. Rather, sometimes we see the rose, while at other times we become conscious of the apple. This perceptual switch happens spontaneously, unprompted by external stimuli. This raises the question of what intrinsic mechanism in the brain underlie them.

Researchers have now uncovered some of the inner workings of conscious perceptions. Interestingly, the perceptual switches can be predicted from the pattern of brain waves in the prefrontal cortex, a brain area implicated in complex behavior such as decision-making and problem-solving. Brain waves are a normal activity of the healthy brain; they result from synchronized activities of larger ensembles of neurons. Beta waves, for example, are oscillations typically associated with active thinking and concentration, while certain slower waves are linked to sleep or rest.“We found typical patterns in low-frequency (1 to 9 Hertz) and beta waves (20 to 40 Hertz) just before the perceptual switches occurred”, says Abhilash Dwarakanath, previously a member of Nikos Logothetis’ Department for Physiology of Cognitive Processes at the Max Planck Institute for Biological Cybernetics in Tübingen and now a researcher at NeuroSpin, Paris. Together with Vishal Kapoor, likewise a former member of Logothetis’ team and now a principal investigator at the International Center for Primate Brain Research in Shanghai, Dwarakanath led the efforts to interpret the data obtained from electrophysical recordings of macaque monkeys.

Read More: How the brain decides what we perceive