How Not Having A Mind’s Eye Affects Long-Term Memory

People who are unable to generate any mental imagery are less capable of recalling key events from their life history, new research has revealed. After scanning the brains of volunteers with aphantasia – a condition characterized by a lack of a “mind’s eye” – the study authors found that this impaired autobiographical memory is underscored by abnormal connectivity between the hippocampus and the visual cortex.

It’s thought that around one in 50 people may have some degree of aphantasia, meaning they struggle to form images in their imagination. While the phenomenon is still poorly understood, it’s likely to be mediated in some way by the hippocampus, which plays a key role in generating mental images.

Interestingly, the hippocampus is also one of the brain’s major memory hubs. This led the study authors to wonder whether an inability to imagine places, people, or events from the past might also result in poorer autobiographical memory among aphantasics.

To investigate, the researchers recruited 14 people with aphantasia and 16 non-aphantasic controls and asked them to recall events from five different periods of their lives: early childhood, adolescence, early adulthood, middle age, and the past year. “We found that people with aphantasia have more difficulty recalling memories,” explained study author Merlin Monzel in a statement. “Not only do they report fewer details, but their narratives are less vivid and their confidence in their own memory is diminished.” 

“This suggests that our ability to remember our personal biography is closely linked to our imagination,” he said.

Intriguingly, aphantasic participants often explained that they knew how a particular place “felt”, but could not recreate that space in front of their mind’s eye. For instance, one individual described the experience by saying “I can put my consciousness in my kitchen at home and feel all around but there is no visual image attached to this feeling.”

During the next phase of the study, the researchers used functional magnetic resonance imaging (fMRI) to observe the brain activity of participants as they attempted to recall life events. “This showed that the hippocampus, which plays an important role in recalling vivid, detailed autobiographical memories, is less activated in people with aphantasia,” said study co-author Pitshaporn Leelaarporn.

More specifically, she explained that “the connectivity between the hippocampus and the visual cortex correlated with the imagination in people without aphantasia, whereas there was no correlation in those affected.” In other words, reduced connectivity between these two brain regions may be responsible for the lack of mental imagery in aphantasics, and may also contribute to a decreased ability to recall life events.

“Our results indicate that visual mental imagery is essential for detail-rich, vivid [autobiographical memory], and that this type of cognitive function is supported by the functional connection between the hippocampus and the visual-perceptual cortex,” conclude the study authors.

Based on this observation, they speculate that offering training in visual imagination may help people suffering from Alzheimer’s and other memory-related disorders to improve their long-term recall. Whether or not this truly is the case is something that future studies will need to assess.

The study is published in the journal eLife.

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