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Neural dynamics of perceptual inference and its reversal during imagery

DOI: 10.7554/elife.53588
Dijkstra, N., Ambrogioni, L., Vidaurre, D., & van Gerven, M. (2020). Neural dynamics of perceptual inference and its reversal during imagery. eLife, 9. doi:10.7554/eLife.53588

Abstract

After the presentation of a visual stimulus, neural processing cascades from low-level sensory areas to increasingly abstract representations in higher-level areas. It is often hypothesised that a reversal in neural processing underlies the generation of mental images as abstract representations are used to construct sensory representations in the absence of sensory input. According to predictive processing theories, such reversed processing also plays a central role in later stages of perception. Direct experimental evidence of reversals in neural information flow has been missing. Here, we used a combination of machine learning and magnetoencephalography to characterise neural dynamics in humans. We provide direct evidence for a reversal of the perceptual feed-forward cascade during imagery and show that, during perception, such reversals alternate with feed-forward processing in an 11 Hz oscillatory pattern. Together, these results show how common feedback processes support both veridical perception and mental imagery.

Authors

  • Nadine Dijkstra2
  • Luca Ambrogioni1
  • Diego Vidaurre1
  • Marcel van Gerven1

Understanding How Our Brain Processes Perception and Imagination

Overview/Introduction

Our brain processes visual information in a fascinating way. When we see something, our brain processes this information from simple to complex forms. But what happens when we imagine something without actually seeing it? Scientists have long thought that our brain might work in reverse, starting with complex ideas and breaking them down into simpler forms to create mental images. This study explores this idea and provides new insights into how our brain processes both real and imagined visuals.

Methodology

To investigate this, researchers used a technique called magnetoencephalography (MEG), which measures brain activity, along with machine learning. They studied 25 participants who were asked to imagine images of faces and houses after seeing them. The researchers used machine learning to analyze the brain's activity patterns during both perception (seeing) and imagery (imagining).
  • Participants: 25 individuals with normal vision
  • Task: Participants viewed images of faces and houses, then imagined them
  • Tools: MEG to record brain activity, machine learning to analyze data

Key Findings

The study revealed several key insights into how our brain processes visual information:
  • Reversal During Imagery: When imagining, the brain's processing order is reversed compared to when actually seeing something. This means that during imagination, the brain starts with complex ideas and works backward to simpler forms.
  • Oscillatory Pattern: During perception, the brain alternates between processing information forward and backward in a rhythmic pattern, aligning with an 11 Hz frequency.
  • Feedback Processes: Both perception and imagination rely on feedback processes, where the brain revisits and updates information.

Implications

These findings have significant implications for understanding how the brain works:
  • Mental Imagery: The study provides evidence that imagining uses a different processing order than seeing, which could impact how we understand and treat conditions involving visual processing or imagination.
  • Predictive Processing: The results support theories that our brain constantly predicts and updates information, which could influence future research in neuroscience and psychology.

Limitations

While the study provides valuable insights, there are some limitations:
  • Sample Size: The study involved a relatively small number of participants, which may limit the generalizability of the findings.
  • Complexity of Brain Activity: The brain's processing is highly complex, and while the study sheds light on certain aspects, there is still much to learn about how perception and imagination work together.
In conclusion, this research enhances our understanding of the brain's dynamic processes during perception and imagination, highlighting the intricate ways in which our brain interprets and rei...