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Reliable and predictive non-perceptual representations in primary visual cortex during attempts at visual imagery in aphantasia

DOI: 10.1167/jov.23.9.5060
Zhang, X., Chang, S., Pearson, J., & Meng, M. (2023). Reliable and predictive non-perceptual representations in primary visual cortex during attempts at visual imagery in aphantasia. Journal of Vision, 23(9), 5060. doi:10.1167/jov.23.9.5060

Abstract

Visual imagery is an important function of the human brain, and previous research on visual imagery reported that imagined stimuli can be decoded in early visual areas, while some other studies claimed that visual imagery generation relied more on higher-level cortical regions. Using fMRI the current study used multi-voxel decoding of attempts at generating visual mental imagery in early visual areas in individuals with aphantasia (lack the ability to voluntarily generate visual imagery). Participants with aphantasia (N = 14) and control (N = 18) groups were asked to generate mental imagery of Gabor patches of different orientations in the left or right visual field. We found that, activation patterns in the V1 and V2 of both aphantasic and control groups could be used to decode the imagined stimuli. However, for aphantasia, the patterns in early visual areas during imagery could not be used to decode the patterns during passively perceiving the same stimuli, whereas accuracies of this cross-task decoding for the control group were significant. These results suggest that aphantasic individuals, are not able to generate neural representations corresponding to perceptual sensory information in the early visual areas via voluntary visual imagery. Consistent with this notion, averaged BOLD activity in the early visual areas of the aphantasic individuals were also atypical during visual imagery, whereas during visual perception a typical contralateral visual field effect was found although slightly weaker than in the control group. For the first time, the current study reports that those with aphantasia do indeed have reliable and predictable neural patterns in early visual cortex during attempts at visual imagery, however these representations diverge from perceptual representations in the same individuals.

Authors

  • Xinyu Zhang3
  • Shuai Chang4
  • Joel Pearson28
  • Ming Meng4

Understanding Visual Imagery and Aphantasia

Overview/Introduction

Visual imagery is the ability to create pictures in our minds, a function that plays a crucial role in how we think and remember. However, some people experience aphantasia, a condition where they cannot voluntarily generate mental images. This study explores how individuals with aphantasia process visual imagery compared to those who can visualize normally. By using advanced brain imaging techniques, researchers aimed to uncover the differences in brain activity between these groups.

Methodology

  • Participants: The study involved two groups: 14 individuals with aphantasia and 18 without (control group).
  • Task: Participants were asked to imagine Gabor patches (a type of visual pattern) in different orientations in either the left or right visual field.
  • Technique: Functional Magnetic Resonance Imaging (fMRI) was used to monitor brain activity, focusing on early visual areas known as V1 and V2.

Key Findings

  • Decoding Imagined Stimuli: Both groups showed distinct brain activation patterns in the V1 and V2 areas when imagining the stimuli. This means that even those with aphantasia have some form of neural activity when attempting visual imagery.
  • Differences in Perception and Imagery: For the control group, the brain patterns during imagery could predict the patterns during actual perception of the stimuli. However, this was not the case for the aphantasia group, suggesting a disconnect between imagined and perceived images in their brains.
  • Atypical Brain Activity: While aphantasic individuals showed atypical brain activity during imagery tasks, their brain activity during actual visual perception was more typical, albeit slightly weaker than the control group.

Implications

  • Understanding Aphantasia: This study provides new insights into how aphantasia affects brain function, showing that while these individuals can generate some brain activity during imagery, it does not align with how they perceive real images.
  • Potential for Future Research: The findings open up new avenues for exploring how different brain regions contribute to visual imagery and perception, which could lead to better understanding and support for individuals with aphantasia.

Limitations

  • Sample Size: The study involved a relatively small number of participants, which may limit the generalizability of the findings.
  • Complexity of Imagery: The study focused on simple visual patterns, so further research is needed to see if these findings apply to more complex imagery.
In summary, this research sheds light on the unique ways in which individuals with aphantasia process visual information, highlighting both the capabilities and limitations of their mental imagery.