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No increase in corticospinal excitability during motor simulation provides a platform to explore the neurophysiology of aphantasia

DOI: 10.1093/braincomms/fcae084
Esselaar, M., Holmes, P. S., Scott, M. W., & Wright, D. J. (2024). No increase in corticospinal excitability during motor simulation provides a platform to explore the neurophysiology of aphantasia. Brain Communications, 6(2). doi:10.1093/braincomms/fcae084

Abstract

This scientific commentary refers to ‘Explicit and implicit motor simulations are impaired in individuals with aphantasia’, by Dupont  et al. (https://doi.org/10.1093/braincomms/fcae072) in Brain Communications

Authors

  • Maaike Esselaar2
  • Paul S Holmes2
  • Matthew W Scott2
  • David J Wright2

Understanding Aphantasia: Insights from Motor Simulation Research

Overview/Introduction

Aphantasia is a fascinating condition where individuals are unable to visualize images in their mind's eye. This commentary, based on the research by Dupont et al., delves into how aphantasia affects motor simulations—both explicit and implicit. The study explores the neurophysiological aspects of aphantasia, offering insights into how this condition might alter brain function during tasks that typically involve visualization and imagery.

Methodology

The research primarily utilized Transcranial Magnetic Stimulation (TMS) to investigate corticospinal excitability, which is a measure of how the brain's motor cortex communicates with the spinal cord during motor simulation tasks. The study suggests that TMS can provide valuable insights into the brain's activity patterns in individuals with aphantasia. However, TMS mainly focuses on cortico-cortical and cortico-spinal activity, indicating a need for additional methods like functional MRI (fMRI) to explore other brain areas involved in image generation and maintenance.

Key Findings

  • Corticospinal Excitability: The study found no increase in corticospinal excitability during motor simulations in individuals with aphantasia, suggesting a distinct neural signature.
  • Visual and Kinaesthetic Imagery: Aphantasia may involve disruptions in the brain networks responsible for visual and kinaesthetic imagery, particularly in areas like the posterior occipital cortex, parietal, and temporal networks.
  • Implicit vs. Explicit Imagery: Recent evidence indicates that implicit visual imagery might remain intact in aphantasia, whereas explicit imagery is impaired.

Implications

  • Future Research Directions: The findings highlight the need for further investigation into the neural mechanisms of aphantasia using diverse techniques such as fMRI. This could help identify specific brain areas affected by the condition.
  • Action Observation and Motor Imagery (AOMI): Exploring AOMI, where participants watch movements and imagine kinaesthetic sensations, could offer new insights. This method might reduce the reliance on visual imagery, providing a more accessible way for those with aphantasia to engage in motor simulations.

Limitations

  • Methodological Constraints: The reliance on TMS limits the scope of the study to certain brain activities, suggesting the need for complementary methods like fMRI to gain a more comprehensive understanding.
  • Diverse Aphantasia Sub-types: The study acknowledges that aphantasia might manifest differently across individuals, necessitating personalized approaches in future research.
In conclusion, this commentary sheds light on the unique challenges faced by individuals with aphantasia during motor simulations. By expanding research methodologies and exploring innovative approaches like AOMI, scientists can better understand and address the compl...