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Multisensory subtypes of aphantasia: Mental imagery as supramodal perception in reverse

DOI: 10.1016/j.neures.2023.11.009
Dawes, A. J., Keogh, R., & Pearson, J. (2024). Multisensory subtypes of aphantasia: mental imagery as supramodal perception in reverse. Neuroscience Research, 201, 50–59. doi:10.1016/j.neures.2023.11.009

Abstract

Cognitive neuroscience research on mental imagery has largely focused on the visual imagery modality in unimodal task contexts. Recent studies have uncovered striking individual differences in visual imagery capacity, with some individuals reporting a subjective absence of conscious visual imagery ability altogether ("aphantasia"). However, naturalistic mental imagery is often multi-sensory, and preliminary findings suggest that many individuals with aphantasia also report a subjective lack of mental imagery in other sensory domains (such as auditory or olfactory imagery). In this paper, we perform a series of cluster analyses on the multi-sensory imagery questionnaire scores of two large groups of aphantasic subjects, defining latent sub-groups in this sample population. We demonstrate that aphantasia is a heterogenous phenomenon characterised by dominant sub-groups of individuals with visual aphantasia (those who report selective visual imagery absence) and multi-sensory aphantasia (those who report an inability to generate conscious mental imagery in any sensory modality). We replicate our findings in a second large sample and show that more unique aphantasia sub-types also exist, such as individuals with selectively preserved mental imagery in only one sensory modality (e.g. intact auditory imagery). We outline the implications of our findings for network theories of mental imagery, discussing how unique aphantasia aetiologies with distinct self-report patterns might reveal alterations to various levels of the sensory processing hierarchy implicated in mental imagery.

Authors

  • Alexei Joel Dawes3
  • Rebecca Keogh14
  • Joel Pearson28

Understanding Aphantasia: A Study on Mental Imagery

Overview/Introduction

Aphantasia is a condition where individuals are unable to visualize images in their mind's eye, a phenomenon that has intrigued scientists and the public alike. While most research has focused on visual imagery, mental imagery is often multi-sensory, involving other senses like hearing or smell. This study explores the diversity within aphantasia, revealing that it is not just a single condition but a spectrum with various sub-types.

Methodology

The researchers conducted a detailed analysis using data from two large groups of individuals with aphantasia. They used a multi-sensory imagery questionnaire to gather self-reported data on participants' ability to imagine sensory experiences. To categorize the different types of aphantasia, they employed three clustering algorithms: k-means, Gaussian Mixture Modelling (GMM), and DBSCAN. These algorithms helped identify distinct sub-groups within the aphantasia population based on their imagery capabilities across different sensory modalities.

Key Findings

  • Heterogeneity in Aphantasia: The study found that aphantasia is not uniform. It includes:
  • Visual Aphantasia: Individuals who cannot visualize but can imagine other sensory experiences.
  • Multi-sensory Aphantasia: Individuals who cannot imagine any sensory experiences.
  • Unique Sub-types: Some individuals have selective imagery capabilities, such as being able to imagine sounds but not images.
  • Prevalence: About 30% of individuals with aphantasia experience only visual imagery absence, while 24% report a complete lack of multi-sensory imagery.

Implications

These findings have significant implications for our understanding of mental imagery and cognitive processes:
  • Network Theories of Mental Imagery: The diversity in aphantasia suggests that different neural mechanisms might be responsible for different types of imagery deficits.
  • Cognitive Neuroscience: Understanding these sub-types can help refine theories about how the brain processes sensory information and generates mental imagery.
  • Practical Applications: This research could inform therapeutic approaches for individuals with aphantasia, helping them develop strategies to compensate for their imagery deficits.

Limitations

While the study provides valuable insights, it also has limitations:
  • Self-reported Data: The reliance on self-reported data might introduce biases, as individuals' perceptions of their imagery capabilities can vary.
  • Algorithm Agreement: The clustering algorithms did not always agree, indicating that further research is needed to refine these classifications.
In conclusion, this study sheds light on the complex nature of aphantasia, highlighting the need for a nuanced understanding of mental imagery and its variations across individuals. By exploring these diverse experiences, researchers can gain deeper insights into the work...