Aphantasia is the suggested name for a condition where one does not possess a functioning mind's eye and cannot voluntarily visualize imagery. The phenomenon was first described by Francis Galton in 1880 but has since remained largely unstudied. Interest in the phenomenon renewed after the publication of a study in 2015 conducted by a team led by Professor Adam Zeman of the University of Exeter, which also coined the term aphantasia. Research on the condition is scarce. Further studies are planned.
The phenomenon was first described by Francis Galton in 1880 in a statistical study about mental imagery, describing it as a common phenomenon among his peers. However, it remained largely unstudied until 2005, when Professor Adam Zeman of the University of Exeter was approached by MX, a man who seemed to have lost the ability to visualize after undergoing minor surgery. Following the publication of MX's case in 2010, Zeman was approached by a number of people reporting a lifelong inability to visualise. In 2015, Zeman's team published a paper on what they termed "congenital aphantasia", sparking a renewed interest in the phenomenon now known simply as aphantasia.
In April 2016 an essay by Blake Ross, co-creator of Firefox was published on Facebook, describing his own aphantasia and his realization that not everyone experiences it. The essay gained wide circulation on social media and in a variety of news sources. 
In December 2017, the book Aphantasia: Experiences, Perceptions, and Insights was published by Alan Kendle with a foreword by Zeman. It contains a collection of insights from various contributors detailing their lives with aphantasia.
In the original paper by Professor Adam Zeman, the Vividness of Visual Imagery Questionnaire (VVIQ) is used to evaluate the quality of the mental image. This questionnaire invites the person to visualize a series of images (a relative, a rising sun, a shop they know, etc.) and rank how vivid the image is, from "perfectly clear and lively as real seeing" (5 points) to "no image at all, you only know that you are thinking of the object" (1 point). It is categorized as aphantasia if they score a total of 30 or less across 16 questions.
In the same paper, it was identified that aphantasia characterizes only voluntary visualizations; the aphantasiacs were still able to have involuntary visualizations (i.e. dreams).
Another study posited that frontal engagement driving feedback connections activates sensory representations in the visual cortex; people suffering from aphantasia could have a deficit with these feedback connections such that the visual cortex cannot be activated to produce an image.
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