Wow! The real bird/rabbit illusion!


This picture above (I am unable to find the original source) has turned out to be my most viewed tweet. I believe it to be a kookaburra bird, but I am not an expert ornithologist. The striking feature of this photo is that, with a small effort, you can also see a rabbit (if you choose to perceive the beak of the bird as the ears of a rabbit!). Obviously one percept is in rivalry with the other, so you will either see a bird or a rabbit but never both of them.

This reminds me of the 100-year-old optical illusion used by Joseph Jastrow to demonstrate that perception is a product of our mental activity. What happens in the brain when we perceive this kind of bistable stimuli?

Three years ago, Tomohiro Ishizu and Semir Zeki published an interesting article in Neuroimage in which they presented the results of an fMRI investigation on bistable images such us the bird-rabbit. What did they found? Interestingly, the brain seems to adopt similar strategies when faced with unstable stimuli that offer a transition between objects belonging to the same category (e.g. face–face) or different categories  (e.g. face–body). Therefore, the authors suggested the existence of a “common reversal-related neural circuitry, which includes fronto-parietal cortex and primary visual cortex”.

Additional brain areas (ACC and the STG) were also recruited in cross-categorical reversals alone that required more radical action selection processes. These results cannot give a definitive answer about the many questions that unstable or bistable images trigger. Moreover, this kind of endeavour is not trivial as it may shed light on the how the brain resolves sensory conflicts. For now, we know that primary perceptual areas provide signals to the brain suggesting that the conflict between the two interpretation is perceptually driven. Higher areas, instead, seem to be suppressed indicating the conflict is strictly perceptual. Further work, the authors suggest, should explore the complexity of cognitively unstable stimuli. Let’s wait for further results and meanwhile enjoy these beautiful and intriguing images.

This or that brain area? The neural correlates of beauty

This is my very first post in a blog. In my posts, I will aim at publishing news or comment recent research or publications mainly related to the field of neuroaesthetics. 

In the article that I recently published in Behavioural Sciences, I discussed the role of two main areas that seem equally involved in the experience of beauty: the middle orbitofrontal cortex (mOFC) and the dorsolateral prefrontal cortex (dLPFC). It may seems pointless to discuss the role of one or the other brain structure in such a complex domain of study, particularly because at the present time we are looking at the brain areas as network rather than in isolation.

Nonetheless, the neuroimaging literature in the field of aesthetics seems to be divided in two “schools”: one consistently producing results highlighting OFC’s role and the other the importance of the prefrontal cortex. I therefore decided to discuss the role that these two brain structures have in aesthetics as well as in other cognitive domains.

Who is the winner? The result of my research argues that the aesthetic experience results from the activity of the mOFC. As this paper is open access (you can download the article by clicking on the image below), I leave it to you to consider whether the conclusions I reached are sound and reasonable.