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Decoding sound content in the early visual cortex of aphantasic participants

DOI: 10.1016/j.cub.2024.09.008
Montabes de la Cruz, B. M., Abbatecola, C., Luciani, R. S., Paton, A. T., Bergmann, J., Vetter, P., Petro, L. S., & Muckli, L. F. (2024). Decoding sound content in the early visual cortex of aphantasic participants. Current Biology, 34(21), 5083–5089.e3. doi:10.1016/j.cub.2024.09.008

Abstract

A 2024 study by Montabes de la Cruz and colleagues investigated how the early visual cortex (EVC) processes sound information in people with aphantasia compared to sighted and blind individuals. The researchers used fMRI to measure brain activity while 23 blindfolded aphantasic participants listened to different auditory scenes (forest, crowd, and traffic). The study found that aphantasic participants showed reduced sound decoding in early visual areas compared to both blindfolded sighted (control) and blind participants. While some sound decoding was possible in specific regions (peripheral V1 and foveal V3), it was generally attenuated across the visual cortex in aphantasic individuals. This finding suggests that aphantasia may be associated with decreased feedback connectivity specific to the early visual cortex, affecting not just visual imagery but also how auditory information is processed in visual areas. The researchers found a hierarchy of feedback connectivity strength: blind participants showed the strongest connectivity, followed by sighted controls, with aphantasic individuals showing the weakest. These results contribute to our understanding of aphantasia's neural basis, suggesting it may involve broader changes in how the visual cortex processes multi-sensory information, rather than just affecting visual imagery alone.

Authors

  • Belén M. Montabes de la Cruz1
  • Clement Abbatecola1
  • Roberto S. Luciani1
  • Angus T. Paton1
  • Johanna Bergmann4
  • Petra Vetter1
  • Lucy S. Petro1
  • Lars F. Muckli1

Understanding How Aphantasia Affects Sound Processing in the Brain

Overview/Introduction

A recent study led by Montabes de la Cruz and colleagues explored how people with aphantasia process sound information differently in their brains compared to sighted and blind individuals. Aphantasia is a condition where individuals cannot visualize images in their mind. The researchers aimed to understand if this condition also affects how the brain processes sounds, particularly in the early visual cortex (EVC), which is typically responsible for processing visual information.

Methodology

  • Participants: The study involved 23 blindfolded participants with aphantasia.
  • Procedure: Participants listened to various auditory scenes, such as sounds from a forest, a crowd, and traffic, while their brain activity was measured using functional magnetic resonance imaging (fMRI).
  • Analysis: The researchers used advanced techniques to analyze brain activity patterns, focusing on the EVC and other brain regions to see how well these areas could decode sound information.

Key Findings

  • Reduced Sound Decoding: Aphantasic participants showed less ability to decode sound information in their early visual areas compared to both sighted and blind participants.
  • Specific Brain Regions: Some sound decoding was possible in specific regions like the peripheral V1 and foveal V3, but overall, it was weaker in aphantasic individuals.
  • Feedback Connectivity: The study found that the strength of feedback connections to the EVC was weakest in aphantasic individuals, stronger in sighted controls, and strongest in blind participants.

Implications

  • Broader Understanding of Aphantasia: These findings suggest that aphantasia might not only affect visual imagery but also how the brain processes multi-sensory information, indicating a broader neural basis for the condition.
  • Potential for New Interventions: Understanding these neural differences could lead to new ways to support individuals with aphantasia, potentially improving their sensory processing capabilities.

Limitations

  • Sample Size: The study involved a relatively small number of participants, which may limit the generalizability of the findings.
  • Specificity to EVC: The reduced feedback connectivity observed may be specific to the EVC, and further research is needed to determine if other brain areas are similarly affected.
In summary, this study sheds light on the unique ways in which aphantasia affects brain function, particularly in processing sounds, and opens up new avenues for understanding and potentially addressing this condition.