A new study on the effects of has helped shed light on which part of the brain is in charge of consciousness.
Scientists have used mice to look into the reactions the major organ has to optical illusions that play on the brain's biases, specifically when it comes to brightness. The researchers, from the , used the neon-colour-spreading illusion - which combines patterns and colours to create overlapping concentric circles - to study visual perception.
Academics have long debated what happens in the brain when it fills in the gaps and perceives the coloured circle as having complete borders. They recently discovered that the illusion also works on mice, with the team using advanced imaging techniques to see how electrical signals move when exposed to the illusions.
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The scientists zoomed in on the visual cortex - a rear section of the brain that receives electrical signals via nerves and processes visual information - and discovered that V1, the surface layer of three, play a fundamental role in interpreting light from the illusion while being tempered by V2, the second layer.
The researchers concluded that the volley between the two - with V1 coming first followed by V2 - shows how consciousness is arranged in the brain. Speaking to , Masataka Watanabe, an associate professor in the department of systems innovation at the University of Tokyo, said the illusion suggests consciousness is a "top-down process".
She said: "The observed relationship between V1 and V2 in processing the illusion implies that consciousness is a top-down process." When scientists refer to top-down processing, they are referring to the way brains interpret surroundings through previous experiences, instead of interpreting the image presented on its own.
The Nature paper concludes that the responses to the illusion were "delayed" compared to normal images, which the researchers said were "in line with the theory that processing illusions requires feedback from higher visual areas (HVAs)". The study abstract adds: "Our findings resolve debates over whether V1 neurons are involved in processing illusions and highlight the involvement of feedback from HVAs."
