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Stronger adaptation of middle-to-late ERP components to object silhouette images before versus after object priming in Aphantasia

DOI: 10.1167/jov.24.10.714
SINGTOKUM, N., Benjasupawan, K., Poungtubtim, C., Chunamchai, S., & Chunharas, C. (2024). Stronger adaptation of middle-to-late erp components to object silhouette images before versus after object priming in aphantasia. Journal of Vision, 24(10), 714. doi:10.1167/jov.24.10.714

Abstract

A 2024 study by Singtokum and colleagues used EEG to investigate how aphantasia affects involuntary visual processing, focusing on a patient (NP) who suddenly lost her ability to generate mental images. The researchers noted that while NP performed normally on most neuropsychological tests, she struggled specifically with identifying objects from their silhouettes, especially from unusual angles. The study used a clever experimental design where participants viewed triplets of images (silhouette-object-silhouette) while performing an unrelated task of detecting tilted images. By comparing brain responses to silhouettes before and after seeing the full object, researchers could measure how object recognition affected subsequent processing. NP showed significantly larger differences in brain activity (ERP components) between pre- and post-silhouette presentations compared to controls, particularly between 300-800ms after stimulus onset. These differences were observed across occipital, frontal, and parietal brain regions. The findings suggest that aphantasia may involve impairment in top-down processing that affects not just voluntary mental imagery but also involuntary visual processing. This provides new insights into how aphantasia impacts visual recognition and suggests the condition may involve broader changes in visual processing than previously thought.

Authors

  • NITHIT SINGTOKUM1
  • Kanyarat Benjasupawan1
  • Chattarin Poungtubtim1
  • Sedthapong Chunamchai1
  • Chaipat Chunharas1

Understanding Aphantasia and Visual Processing

Overview/Introduction

A recent study conducted by Singtokum and colleagues in 2024 delves into the intriguing world of aphantasia—a condition where individuals are unable to generate mental images. This research focuses on a unique case of a patient, referred to as NP, who suddenly lost her ability to visualize images in her mind. The study aims to understand how aphantasia affects involuntary visual processing, particularly in recognizing objects from silhouettes.

Methodology

The researchers employed a novel experimental approach using EEG (electroencephalography) to monitor brain activity. Participants, including NP and a control group, were shown sequences of images: a silhouette, the actual object, and then another silhouette. During this task, they were asked to focus on identifying tilted images, which was unrelated to the main study focus. This clever setup allowed the researchers to observe how seeing the full object influenced the brain's processing of the subsequent silhouette.

Key Findings

  • Brain Activity Differences: NP exhibited significant differences in brain activity, specifically in ERP (event-related potential) components, when comparing responses to silhouettes before and after viewing the full object.
  • Timing of Differences: These differences were most pronounced between 300-800 milliseconds after the stimulus appeared.
  • Affected Brain Regions: The changes in brain activity were noted across several areas, including the occipital, frontal, and parietal regions.
  • Top-Down Processing Impairment: The study suggests that aphantasia may involve broader impairments in top-down processing, affecting both voluntary and involuntary visual recognition.

Implications

This research provides new insights into the nature of aphantasia, suggesting it is not just a simple inability to visualize but may involve more extensive changes in how the brain processes visual information. Understanding these mechanisms could lead to better support and strategies for individuals with aphantasia, potentially improving their ability to recognize and interact with visual stimuli in daily life.

Limitations

While the study offers valuable insights, it focuses on a single patient, which may limit the generalizability of the findings. Further research involving a larger group of individuals with aphantasia is needed to confirm these results and explore the condition's broader implications.
In summary, this study sheds light on the complex nature of aphantasia, highlighting its impact on both voluntary and involuntary visual processing. By exploring the brain's response to visual stimuli, researchers are uncovering the intricate ways in which this condition affects perception and recognition.