Aphantasia linked to abnormal brain responses to imagined and observed actions

In a study published in Brain Communications, researchers have found evidence that individuals with aphantasia, a condition where people struggle to create mental images, exhibit significant differences in brain activity related to motor simulations compared to those without this condition. The study found that people with aphantasia do not show the expected increase in brain activity that typically occurs when imagining or observing movements, which contrasts sharply with individuals who can easily generate mental images.

Aphantasia is a condition where individuals are unable to generate voluntary mental images—a function most people perform effortlessly, such as picturing a beach scene or visualizing a loved one’s face. For those with aphantasia, the mind’s eye is essentially blind, impacting not just visual imagination but potentially other sensory simulations as well.

While the phenomenon has been acknowledged in psychological literature for some time, it was formally named and described in more detail in recent years. Aphantasia varies widely among affected individuals; some report a total lack of visual imagery, while others may have specific deficits in imagining sounds, smells, or tactile sensations.

Research into aphantasia has predominantly concentrated on visual and auditory domains, exploring how this condition affects everyday tasks such as recognizing faces, navigating memories, and engaging with artistic or creative endeavors. Studies have used both subjective reports of imagery vividness and objective measures like brain imaging to investigate these impacts.

Early findings suggested that while aphantasics might lack visual imagination, they can often compensate through other cognitive pathways, relying more on factual knowledge or verbal reasoning to perform tasks typically aided by imagery.

The latest study was motivated by a need to understand how aphantasia affects motor cognition, specifically the ability to perform motor simulations — imagining or planning movements without executing them.

“We were interested in testing individuals with aphantasia in order to shed light on the neurophysiological relationship between different covert actions, especially motor imagery, a central research topic for our team,” explained study author Florent Lebon, a professor at the University of Burgundy. “Covert actions are mental processes that help individuals to perform subsets of actions that are not visible, because they are not executed. Covert actions include, to name the most important, imagery, language, observation and action preparation.”

“These mental phenomena have intrigued and still intrigue philosophers, psychologists, and neuroscientists, as they are complex and introspective processes, which play a major role in human cognition When we learned of this population with a reported imagery impairment, we were motivated to investigate the excitability of their motor system during covert actions such as motor imagery and reading sentences about actions.”

To investigate the impact of aphantasia on motor simulations, the researchers recruited 34 right-handed participants, split equally into two groups based on their ability to generate mental images. This included 17 aphantasics and 17 phantasics (individuals who can generate mental images). Participants were recruited through a mailing list at the University of Bourgogne and an aphantasics association in Dijon.

The participants first completed a series of questionnaires designed to measure their capacity for visual and motor imagery. The Vividness of Movement Imagery Questionnaire (VMIQ-2) was used to assess how vividly participants could imagine motor actions in different modalities, such as external visual imagery (seeing the movement as an observer), internal visual imagery (seeing the movement in the first person), and kinesthetic imagery (feeling the movement).

Another questionnaire, the Spontaneous Use of Imagery Scale (SUIS), measured how often participants engaged in visual mental imagery in daily activities. These self-report measures aimed to capture the subjective experience of imagery and its application in everyday life.

Participants with aphantasia reported significantly lower vividness in their ability to imagine motor actions across all modalities — external visual, internal visual, and kinesthetic — compared to the phantasics. Furthermore, their scores on the Spontaneous Use of Imagery Scale indicated that aphantasics use mental imagery less frequently in daily life than their counterparts.

One week after the behavioral tests, the participants returned for the neurophysiological session. During this session, the researchers measured corticospinal excitability using transcranial magnetic stimulation (TMS). This technique allows for the indirect measurement of brain activity in specific areas related to motor control by applying magnetic pulses to the scalp and recording the muscle responses in the hand.

Participants underwent TMS both at rest and while engaged in different motor simulation tasks: imagining movements (both visually and kinesthetically) and observing movements on a video screen. The setup included surface electrodes placed on the index finger muscle to record responses, and a figure-eight coil to deliver TMS pulses precisely timed to the tasks.

The researchers found evidence that aphantasia was related to altered brain function. For phantasics, there was a notable increase in corticospinal excitability when they engaged in kinesthetic motor imagery and while observing actions, indicating normal motor cortex activation as expected in motor simulation. This contrast was stark in aphantasics who showed no such increase in brain activity, suggesting a fundamental neural difference in processing or generating motor simulations.

These findings not only confirm the challenges aphantasics face in generating mental simulations but also highlight the neural basis of these difficulties. This insight extends the understanding of aphantasia beyond a simple inability to “see” mentally, illustrating a more complex disruption in the cognitive processes that support the simulation of actions and sensory experiences.

“In the general population, individuals vary in their ability to visualize objects or imagine moving,” Lebon told PsyPost. “Our study shows a real neurophysiological difference within the motor system for aphantasics as compared to individuals with a normal capacity to imagine, and this difference does not seem to reflect any differences in strategy or cognitive effort.”

“Strong deficits in imagery ability, as seen in aphantasics, might impair other cognitive processes, such as observation or action language. For example, the inability to imagine would impact the capacity of deep-level reading comprehension, i.e., selecting words that best fit the context of sentences, especially in descriptions of physical relationships, positions, and visual displays. However, this inability may be compensated by other strategies to understand a text.”

Interestingly, the researchers not only observed differences between aphantasics and phantasics, but among the aphantasics as well.

“We were surprised by the different profiles of individuals in their capacity to imagine actions,” Lebon said. “There are different modalities to imagine an action. For example, you can visualize what your arm looks like when you hit a ball with a tennis racket (visual imagery) or you can imagine what your arm and body feel like during this action (kinesthetic imagery).”

“We found that some individuals with aphantasia are unable to both visualize and feel the movement (complete aphantasia) while others are able to feel the movement but unable to visualize it. Therefore, this condition may affect all sensorimotor modalities or just specific ones. At the moment, there is no evidence to explain these differences.”

More research is needed to understand whether different strategies or motivations might influence the ability of aphantasics to engage in motor simulations. Future studies could also explore whether interventions, such as neurostimulation or behavioral therapy, might help aphantasics improve their simulation abilities.

“The inability to visualize objects or action may alter specific cognitive processes; however, the brain has the ability to generate other strategies in order to reach a goal (understand others’ actions, follow a story),” Lebon explained. “At the moment, we don’t know whether imagery abilities are stable within individuals or whether they can evolve.”

“We would like to determine whether it is possible to help aphantasics improve their ability to imagine, by means of safe neurostimulation techniques as well as behavioral therapies. Determining whether re-activating a specific altered circuit would benefit different cognitive processes in humans will lead to a better understanding of motor cognition but also to potential advances in clinical applications.”

“We have applied for international grants to keep working on this topic with aphantasics, but also with hyperphantasics (individuals with a super ability to imagine),” Lebon continued. “In the near future, we intend to test children and students at the Sport Science Faculty of Dijon to determine whether the ability to imagine actions would predict motor learning but also general learning (science, general knowledge).”

The study, “Explicit and implicit motor simulations are impaired in individuals with aphantasia,” was authored by William Dupont, Charalambos Papaxanthis, Carol Madden-Lombardi, and Florent Lebon.

Reference

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