Blind imagination: The behavioural and neural signatures of aphantasia.

Visual imagery is fundamental to everyday functioning. It enables us, for example, to visualize the face of a loved one many miles away or to imagine the Northern Lights on a beautiful summer's night. Furthermore, imagery is typically thought to be a core component for many important everyday activities such as recollecting memories from the past or imagining future events. Imagery is also considered important for navigating around our environment, making moral judgements and for creative problem solving to give just a few examples. Despite its importance, it has become increasingly clear that some people have a complete absence of visual imagery although it is only recently that this phenomenon, now known as aphantasia, has been recognised. This lack of attention is surprising given that around 4% of the population are estimated to have aphantasia and means that the condition is currently poorly understood. Our work indicates that people with aphantasia have normal levels of intelligence and general cognitive functioning but less detailed memories from the past and a profound deficit at imagining future events. Nevertheless, there is currently little work investigating whether an absence of imagery impacts other important everyday tasks. Greater understanding of this would not only help to characterise aphantasia better but more generally provide new insight into the extent to which visual imagery really is important for everyday functioning, a question that has received intense debate over recent decades. The neural underpinnings of aphantasia are also currently poorly understood. We have provided preliminary evidence that the visual imagery brain network functions differently in people with aphantasia but a more comprehensive investigation is needed. In this project, we will recruit 64 people with aphantasia and compare them with 64 controls who have normal levels of imagery. Groups will be matched on age and gender. Participants will complete a set of imagery questionnaires to establish their visual imagery deficits and to assess whether problems extend to other imagery domains (e.g. smell or sound). Participants will then complete a series of tasks important for everyday functioning that have not been systematically investigated in aphantasia. This will include tests of spatial navigation, problem solving, moral judgements and social and emotional reasoning. We will also investigate whether transcranial direct current stimulation (tDCS), which modulates brain activity, can elicit imagery in people with aphantasia and whether any such effects extend to improved performance on future imagination. Lastly, we will use brain imaging to understand better the neural basis of aphantasia. This will include measuring brain activity whilst participants recollect memories from the past and mentally rotate objects - activities that typically require mental imagery. We will also measure whether there are differences in brain regions and how these measures are associated with performance on the other tasks we will administer. In summary, this project aims to provide the most comprehensive examination to date of aphantasia, including whether: 1) it affects important functions where visual imagery is typically involved; 2) improved imagery in aphantasia can be elicited through tDCS; 3) there are any brain differences in aphantasics. This project should benefit people with aphantasia who are keen to understand more about the condition as well as, in the medium-term, help optimise alternative strategies for completing tasks, for example in educational settings, where imagery is important, and additionally potentially inform future treatments.