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Résumé - LSD: Visual Hallucinations and Cortical Modeling (1)

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Introduction

Background

Visual hallucinations induced by LSD often involve geometric patterns and form constants, which are subjective visual experiences commonly reported across individuals. These patterns are thought to be related to the organization and hyperstimulation of the visual cortex.

Problem Statement and Study Significance

• Despite the long-standing interest in this phenomenon, there is a lack of up-to-date research and quantitative models explaining these visual hallucinations. In fact, we don’t really know what causes these patterns. Understanding the interactions between psychedelic drugs and the brain can provide valuable insights into neural processes and potentially inform therapeutic applications, particularly in the context of self-medication (e.g., Brain cancer patients) and psychological interventions (e.g., CBT).
• The study will focus on developing a quantitative computational model to simulate LSD-induced visual hallucinations, particularly geometric patterns known as 'form constants'.

Literature Review

Current State of Knowledge

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Existing models

Existing Theoretical and Neuronal Models of Visual Hallucinations

.. certain models have attempted to explain the complex phenomena observed during psychedelic experiences, though not … . One notable approach is the Computational (Neuro)phenomenology Model, which employs deep neural networks to simulate visual hallucinations (Suzuki et al., 2024). This model identifies three key dimensions of hallucinations: realism, dependence on sensory input, and complexity (Suzuki et al., 2024). While not specifically designed for LSD-induced hallucinations, its framework provides a promising foundation for adaptation to psychedelic-specific experiences.

Another relevant model is the Three-Module Perception Model proposed by Nara et al. (2022). This model suggests that visual hallucinations arise from instabilities in the interactions between memory, perception, and collective field modules (Nara et al., 2022). It suggests that inconsistencies between top-down and bottom-up information can lead to the emergence of mismatched perceiving attractors, potentially explaining the mechanism behind hallucinatory experiences (Nara et al., 2022). In other words, explaining why patients see things that aren't there.

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Form Constants and Geometric Patterns in Subjective Experiences

The study of geometric patterns in psychedelic experiences dates back to 1926 with Heinrich Klüver's seminal work on mescaline-induced hallucinations (Wikipedia contributors, 2024). Klüver identified four types of recurring geometric patterns, known as form constants:

1. Lattices (including honeycombs, checkerboards, and triangles)
2. Cobwebs
3. Tunnels
4. Spirals

These patterns are not unique to mescaline and have been reported across various psychedelic substances, including LSD. The neurophysiological basis for these form constants is believed to be related to the organization of the visual system, particularly the mapping between retinal patterns and the columnar organization of the primary visual cortex (Bressloff et al., 2002; Wikipedia contributors, 2024).

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