How does brain process colour and shape?

We are surrounded by so many colours and shapes that we can distinguish visually but have you ever wondered how our brain interprets them?

A recent study has shown that there are neurons that respond selectively to particular combinations of colour and shape.

The study was published in the journal 'Science'.

"New genetic sensors and imaging technologies have allowed us to more thoroughly test the link between visual circuits that process colour and shape. These findings provide valuable insight about how visual circuits are connected and organised in the brain," said Edward Callaway, senior author of the study.

Similar to a digital camera sensor, light-sensitive cells in the eye (photoreceptors) detect wavelengths of light within specific ranges and at particular locations. This information then travels through the optic nerve to neurons in the visual cortex that interprets the information and begins to decipher the contents of the picture.

"The goal of our study was to better understand how the visual system processes the colours and shapes of visual stimuli. We wanted to apply new imaging techniques to answer these longstanding questions about visual processing," said Anupam Garg, Study's co-first author.

The researchers used imaging technology combined with genetically expressed sensors to study the function of thousands of individual neurons involved in processing colour and shape in the primary visual cortex.

During long recording periods, roughly 500 possible combinations of colour and shape were tested to find the stimulus that best activated each visually-responsive neuron.

The team found that visual neurons selectively responded to colour and shape along a continuum--while some neurons were only activated by either a specific colour or shape, many other neurons were responsive to a particular colour and shape simultaneously, contrary to long-held notions about how visual processing works.

"Our brain encodes visual information efficiently using circuits that are smartly designed. Contrary to what is taught in the classroom--that colour and form are processed separately in the early visual cortex and then integrated later by unknown mechanisms--the brain encodes colour and form together in a systematic way," said Peichao Li, another co-first author of the study.

"This discovery lays a foundation for understanding how neural circuits make the computations that lead to colour vision. We look forward to building on these findings to determine how the neurons in the visual cortex work together to extract colours and shapes," said Callaway.