Drawing a blank Image Source/Getty

Picture, for a moment, a sunny beach: shimmering blue water, waves rolling on to the shore, colourful umbrellas dotted along the sand.

For some people, this act is impossible; they are unable to “see” anything in their minds. The condition, known as aphantasia, affects about 2 per cent of people but remains largely mysterious.

Now there is a glimmer of progress in understanding it, with the discovery that electrically stimulating the brain can alter the strength of our mental imagery. Although it’s not yet clear if this will benefit people with aphantasia, it could potentially be used to boost memory, navigational ability and creativity in people who don’t have aphantasia – or to turn down mental imagery in those haunted by dark, intrusive thoughts.


The first detailed study of aphantasia was published in 2015, but it wasn’t clear whether people with aphantasia are unable to form mental images to begin with, or whether the conscious brain is somehow blocking access to them. Neither did we know if the strength of mental imagery can be changed.

Test of the mind’s eye

To investigate, Joel Pearson at the University of New South Wales in Sydney and his colleagues first developed an objective test of how strong the mind’s eye is. They exploited a phenomenon called binocular rivalry, in which people perceive only one image despite their left and right eye being shown different images at the same time.

The effect can be influenced with suitable priming: for instance, asking someone to imagine the colour red before showing a red image to one eye and a green image to the other simultaneously.

Pearson found that people who don’t have aphantasia perceived the primed red image about 60 to 95 per cent of the time, and that those who self-report a stronger ability to conjure up mental images are more likely to perceive the red. However, when they tested 15 people with aphantasia, they perceived the red image about half the time – no more than predicted by chance.

This suggests that people with aphantasia are unable to create mental images in the first place, says Pearson: “If the image was there in the visual cortex, we should see priming, independent of the individual’s awareness of that image.”

Next, the researchers took fMRI scans of brain activity in 31 people without aphantasia during rest. Those with stronger visual imagery had lower activity in the visual cortex and higher activity in the prefrontal cortex – also known as the brain’s command centre. It exerts control over other brain areas, including the visual cortex.

“The visual cortex is like a sketch pad; it’s where you create images,” says Pearson. “If there’s too much activity and noise, it’s like sketching on a dirty piece of paper: it’s hard to see the drawing.”

Higher activity in the prefrontal cortex, on the other hand, may enhance visualisation because it controls the visual cortex, he says.

The researchers also showed it was possible to manipulate the strength of visual imagery – as measured by the binocular rivalry tests – in people without aphantasia using a technique called transcranial direct current stimulation (tDCS). It involved attaching electrodes to their scalps to deliver weak currents to the visual and prefrontal cortices, turning activity up or down depending on which way the current flows.

Pearson is now planning to test whether tDCS can spark mental imagery in people with aphantasia, enabling them to see with their minds for the first time.

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The team also plans to explore whether boosting mental visualisation has any wider benefits – such as helping students remember their class notes.

It could also alter moral judgement. Part of a classic thought experiment asks people whether they would push a fat man to off a bridge on to railway tracks, killing him but also blocking a runaway carriage that threatens to kill five people. Individuals with stronger mental imagery are more likely to save the fat man because they clearly visualise the act of having to push him to his death.

Another question Pearson is planning to tackle is whether reducing mental imagery could diminish visual hallucinations in people with schizophrenia, or provide relief from intrusive flashbacks for people with post-traumatic stress disorder.

Sergio Della Sala at the University of Edinburgh, UK, says the results are thought-provoking, but it may take time for them to be translated into clinical benefits. “It may be hard to target a single cognitive process or modify an individual behaviour by applying a generalised current [using tDCS],” he says.

However, Pearson is optimistic that studying aphantasia patients will continue to unearth clues that could benefit us all. “I think there will be a silver lining to all this,” he says.

Journal reference: bioRxiv, DOI: 10.1101/093690

Reference: PsyArXiv preprint