By: Keisuke Suzuki, Warrick Roseboom, David J. Schwartzman & Anil K. Seth

In: Nature, Scientific Reports, 7

Date: 22 November 2017

Key Concepts:

• Altered states of consciousness (ASC):
  • Qualitative alteration in the overall pattern of mental functioning.
    • The experiencer feels their consciousness is radically different from “normal”.
  • Not defined by any particular content of consciousness.
    • Covers a wide range of qualitative properties.
    • Temporal distortion, disruptions of the self, ego-dissolution, visual distortions and hallucinations.
  • Causes of ASC.
    • Psychedelic drugs (e.g., LSD, psilocybin).
    • Pathological or psychiatric conditions such as epilepsy or psychosis.
• Difficult to distinguish:
  • The primary causes of altered phenomenology.
  • The secondary effects of other more general aspects of neurophysiology and basic sensory processing.
• Combine virtual reality and machine learning:
  • Isolate and simulate one specific aspect of psychedelic phenomenology: visual hallucinations.
• Deep convolutional neural networks (DCNNs).
  • Successful in object recognition.
  • Surprising similarities with primate human brain.
    • Higher and lower layers of show similar activity patterns.
• Deep dream:
  • “Clamping” certain parts of the neural network.
    • Adjusting the input image until the network settles into a stable state.
  • Meaning, adjusting the image until it fits previously learned categories.
    • Resulting images have hallucinatory qualities.
  • Similarities to the framework of perception as a form of predictive processing.
    • Perceptual content is determined by the exchange of:
      • Top-down perceptual predictions.
      • Bottom-up perceptual prediction errors.
    • Perceptual content is the brain’s “best guess” of the causes of its sensory input.
  • Hallucinations:
    • Imbalances between top-down perceptual predictions (prior expectations or ‘beliefs’) and bottom-up sensory signals.
• Deep dream is similar to the imposition of a strong perceptual prior on incoming sensory data.
  • Deep Dream used to produce biologically realistic visual hallucinations.
    • Feeding this images back to humans in VR.
    • Create a “Hallucination Machine”.
      • Experience is some ways qualitatively similar to psilocybin.
        • Perceptual and imagination dimensions.
        • Patterns, imagery, strange, vivid, and space.
        • Overall intensity and emotional arousal of the experience.
      • Not sufficient to induce temporal distortions.
• Psychedelics may work by influencing [alternating] different levels of processing.
  • Increased influence of the lower levels (less categorization influence of  higher levels).
  • Increased influence of the higher levels (over-emphasis of prediction).