Reduced Visual Imagery Impairs Autobiographical Memory Retrieval in Aphantasia

Core Concepts

Reduced or absent visual imagery in aphantasia is associated with impaired retrieval of detail-rich autobiographical memories, reflected by decreased hippocampal activation and altered functional connectivity between the hippocampus and visual-perceptual cortices.

Abstract

The study examined the neural correlates of autobiographical memory (AM) retrieval in individuals with aphantasia, a condition characterized by reduced or absent voluntary visual imagery. Key findings: Aphantasics reported fewer internal details (e.g., emotional, perceptual) during AM retrieval compared to controls, despite no differences in external details. Aphantasics showed decreased activation in the hippocampus and increased activation in visual-perceptual cortices during AM retrieval. Controls exhibited strong negative functional connectivity between the hippocampus and visual cortex during AM retrieval, which predicted better visualization abilities. This connectivity was absent in aphantasics. Resting-state functional connectivity between the hippocampus and visual cortex positively correlated with visualization abilities in controls, but negatively in aphantasics. These results suggest that the deficits in AM retrieval associated with aphantasia are reflected by altered interactions between the hippocampus and visual-perceptual regions. The findings support the idea that visual imagery plays a crucial role in the construction of detail-rich autobiographical memories, and that this process is supported by the functional connection between the hippocampus and visual cortex.

Stats

"Aphantasics reported less internal events, less emotional details, less perceptual details, and less details regarding time and place compared to controls." "Controls displayed a stark negative correlation between functional connectivity of the right hippocampus and left visual-perceptual cortices during AM retrieval, whereas aphantasics did not." "Resting-state functional connectivity between the right hippocampus and right visual-perceptual cortex positively correlated with visualization abilities in controls, but negatively in aphantasics."

Quotes

"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." "One potential mechanism of aphantasia-related AM deficits is that the heightened activity of the visual-perceptual cortices observed in our and previous work hinders aphantasics to detect weaker imagery-related signals." "In aphantasia, it is hypothesized that this top-down hierarchy is disrupted and therefore, the hippocampus can no longer initiate the retrieval and incorporation of visual-perceptual details in one coherent mental event."

Key Insights Distilled From

Hippocampal-occipital connectivity reflects autobiographical memory deficits in aphantasia

by Monzel,M., L... at www.biorxiv.org 08-13-2023

https://www.biorxiv.org/content/10.1101/2023.08.11.552915v4

Deeper Inquiries

How do the spatial cognition and scene construction abilities of aphantasics compare to individuals with hippocampal damage?

Individuals with aphantasia and those with hippocampal damage exhibit similarities in their deficits related to episodic memory retrieval. Both groups tend to report fewer internal details, including emotional and temporal details, during memory recall. However, a key difference lies in spatial cognition. While individuals with hippocampal damage typically struggle with spatial orientation and scene construction due to the crucial role of the hippocampus in spatial navigation, aphantasics do not report difficulties in spatial orientation. Aphantasics may have intact spatial cognition processes, as they can describe the feeling of the space around them even though they cannot visualize it in their mind's eye. This distinction suggests that the deficits in aphantasia may be more specific to visual imagery and the population of visual details in memory rather than spatial cognition per se.

What are the potential mechanisms underlying the increased activation in the visual-perceptual cortices of aphantasics during autobiographical memory retrieval?

The increased activation in the visual-perceptual cortices of aphantasics during autobiographical memory retrieval may be attributed to several potential mechanisms. One possible explanation is that the heightened activity in these regions hinders aphantasics from detecting weaker imagery-related signals, leading to difficulties in constructing visual details during memory recall. This hyperactivity in the visual-perceptual cortices may create a noisy signal environment, making it challenging for aphantasics to populate their memories with vivid visual imagery. Additionally, the increased activation in these regions could reflect compensatory mechanisms, where the brain attempts to enhance visual processing to make up for the lack of voluntary sensory imagery experienced by aphantasics. Overall, the heightened activity in the visual-perceptual cortices of aphantasics during memory retrieval may be a result of altered neural processing related to visual imagery deficits.

Could neuroscientific interventions targeting the functional connectivity between the hippocampus and visual cortex be used to enhance autobiographical memory retrieval in aphantasia?

Neuroscientific interventions targeting the functional connectivity between the hippocampus and visual cortex hold promise for enhancing autobiographical memory retrieval in aphantasia. By modulating the interaction between these key brain regions, it may be possible to improve the integration of visual-perceptual details into memory recall processes. For individuals with aphantasia, strengthening the functional connectivity between the hippocampus and visual cortex could potentially facilitate the retrieval and incorporation of visual details into autobiographical memories. This intervention could help bridge the gap in visual imagery deficits experienced by aphantasics, leading to more vivid and detail-rich memory recall experiences. Further research and clinical trials are needed to explore the efficacy and safety of such interventions in enhancing autobiographical memory retrieval in individuals with aphantasia.