THE ESSENTIAL
- Aphantasia was first described in 1880. But specialists really started to take an interest in this neurological disorder in 2015.
2 to 5%. This is the share of the population that would suffer from aphantasia, according to estimates. This neurological disorder results in an inability to represent a mental image. Clearly, patients affected by this pathology are not able to visualize faces, landscapes or even animals in their heads. In a study published in the scientific journal eLiferesearchers from the University of New South Wales (UNSW Sydney) in Australia reported that this condition might potentially be detected through analysis of the pupillary response to light.
“The pupillary response to light is an important automatic physiological response that optimizes light reaching the retina. Recent work has shown that the pupil also adjusts in response to illusory brightness and a range of cognitive functions. it is unclear what exactly drives these endogenous changes”, they wrote in the works.
An analysis of pupillary reactions
For the purposes of their study, the scientists recruited 60 people. First, they assessed their pupillary reflex. For this, the authors asked them to wear special glasses in order to follow their eye movements and the size of their pupils. Then, the volunteers were exposed to bright or dark shapes on a gray background, which caused pupillary constriction in response to bright shapes and pupillary dilation in response to dark shapes.
In order to test their visual imagery, namely the ability of their mind to visualize images, the team asked the participants to imagine the same light or dark shapes that they observed during the previous experiment. Adults had to do this with their eyes open, so their pupils might be tracked.
Dilation of the pupils, a clue to detect aphantasia
According to the results, 42 volunteers had standard visual imagination skills and 18 people suffered from aphantasia. According to the researchers, the pupils of people with this neurological disorder did not react when asked to imagine dark and light shapes, whereas those of non-aphantasic adults did. “Our results provide evidence that pupillary light response indexes the sensory strength of visual imagery. This work also provides the first physiological validation of aphantasia,” can we read in the study.
