Back to all research

Hippocampal-occipital connectivity reflects autobiographical memory deficits in aphantasia

DOI: 10.7554/elife.94916.3
Monzel, M., Leelaarporn, P., Lutz, T., Schultz, J., Brunheim, S., Reuter, M., & McCormick, C. (2024). Hippocampal-occipital connectivity reflects autobiographical memory deficits in aphantasia. eLife, 13. doi:10.7554/eLife.94916.3

Abstract

Aphantasia refers to reduced or absent visual imagery. While most of us can readily recall decade-old personal experiences (autobiographical memories, AM) with vivid mental images, there is a dearth of information about whether the loss of visual imagery in aphantasics affects their AM retrieval. The hippocampus is thought to be a crucial hub in a brain-wide network underlying AM. One important question is whether this network, especially the connectivity of the hippocampus, is altered in aphantasia. In the current study, we tested 14 congenital aphantasics and 16 demographically matched controls in an AM fMRI task to investigate how key brain regions (i.e. hippocampus and visual-perceptual cortices) interact with each other during AM re-experiencing. All participants were interviewed regarding their autobiographical memory to examine their episodic and semantic recall of specific events. Aphantasics reported more difficulties in recalling AM, were less confident about their memories, and described less internal and emotional details than controls. Neurally, aphantasics displayed decreased hippocampal and increased visual-perceptual cortex activation during AM retrieval compared to controls. In addition, controls showed strong negative functional connectivity between the hippocampus and the visual cortex during AM and resting-state functional connectivity between these two brain structures predicted better visualization skills. Our results indicate that visual mental imagery plays an important role in detail-rich vivid AM, and that this type of cognitive function is supported by the functional connection between the hippocampus and the visual-perceptual cortex.

Authors

  • Merlin Monzel23
  • Pitshaporn Leelaarporn1
  • Teresa Lutz1
  • Johannes Schultz1
  • Sascha Brunheim1
  • Martin Reuter15
  • Cornelia McCormick1

Understanding Aphantasia and Its Impact on Memory

Overview/Introduction

Aphantasia is a unique condition where individuals have little to no ability to visualize mental images. This study explores how aphantasia affects the ability to recall autobiographical memories (AM), which are personal past experiences often recalled with vivid imagery. The research specifically investigates whether the brain's connectivity, particularly involving the hippocampus, differs in individuals with aphantasia compared to those without.

Methodology

  • Participants: The study involved 14 individuals with congenital aphantasia and 16 control participants matched demographically.
  • Tasks: Participants completed an autobiographical memory task while undergoing fMRI scans to observe brain activity. They were also interviewed to assess their ability to recall episodic (personal events) and semantic (general knowledge) memories.
  • Measurements: Memory details were categorized into internal (e.g., emotions, sensory details) and external (e.g., factual information) details. Participants' confidence in their memories was also rated.

Key Findings

  • Memory Recall: Individuals with aphantasia reported more difficulties in recalling autobiographical memories, had lower confidence in their memories, and provided fewer internal and emotional details than controls.
  • Brain Activity: During memory retrieval, aphantasics showed decreased activation in the hippocampus and increased activation in the visual-perceptual cortex compared to controls.
  • Functional Connectivity: Controls exhibited strong negative connectivity between the hippocampus and visual cortex, which was linked to better visualization skills. This connectivity was notably absent in aphantasics.

Implications

  • Role of Visual Imagery: The study highlights the importance of visual mental imagery in creating vivid and detailed autobiographical memories. The functional connection between the hippocampus and visual cortex appears crucial for this process.
  • Potential Interventions: Understanding these neural mechanisms opens avenues for exploring interventions that might enhance memory retrieval in individuals with aphantasia by potentially boosting visual imagery capabilities.

Limitations

  • Directionality of Connectivity: The study's fMRI data cannot determine the direction of connectivity between the hippocampus and visual cortex, leaving open questions about the exact nature of their interaction.
  • Control Task: Differences in brain activity could also be influenced by factors unrelated to memory or imagery, such as the emotional relevance of the tasks.
In conclusion, this research provides valuable insights into how aphantasia affects memory retrieval and the underlying neural processes, offering a foundation for future studies and potential therapeutic strategies.