Geometric visual hallucinations—tunnels, spirals, lattices, and cobwebs—are seen under psychedelics, flickering lights, or during sleep transitions. These patterns appear in both eyes and move with them, indicating a brain origin. A theory explains them as arising in the primary visual cortex (V1), modeled as a lattice of interconnected hypercolumns. The lateral connections between hypercolumns are assumed to have symmetries under the Euclidean group E(2). When V1's uniform resting state becomes unstable, spontaneous activity patterns emerge that, when mapped back to the visual field, correspond to the hallucination forms. The results depend on the connectivity details and suggest that the same cortical mechanisms process edges, contours, surfaces, and textures.
Lysergic acid diethylamide (LSD) directly alters immune function when immune cells are exposed to it in a laboratory setting. At a high concentration of 100 microM, LSD suppresses the proliferation of B-lymphocytes, reduces production of the cytokines IL-2, IL-4, and IL-6, and inhibits the induction of cytotoxic T-lymphocytes. In contrast, at lower concentrations between 0.0001 and 0.1 microM, LSD enhances both basal and IL-2-augmented natural killer (NK) cell activity. These differential effects suggest that LSD can directly influence components of the immune system at concentrations potentially reached in the human body.