The cortical origin of visual hallucinations

Geometric patterns of spirals, honeycombs and checker-boards are common themes in visual hallucinations. They are thought to originate from the neural circuitry of the primary visual cortex -- the region of the brain which processes visual shapes.

Geometric visual hallucinations.  A-D: LSD flashbacks painted by Oster (1970).  E-F: Hallucinations by THC intoxication (Siegel & Jarvik, 1975).  G: Hallucinations by occular pressure (Tyler, 1978).  H: Migraine aura (Richards, 1971). Adapted from Billock & Tsou (2012)
Our collaborators at the University of New South Wales devised a clever method for objectively measuring the visual hallucinations seen in stroboscopic flicker. In particular, they measured the spatial wavelength and speed of illusory blobs that appear to race around a ring-shaped stimulus when it is flickered at 10-20 Hz. As part of this study, we constructed a mathematical model of the visual cortex that reproduces much of the perceptual behaviour of the hallucinations.


Journal paper
Pearson J, Chiou R, Rogers S, Wicken M, Heitmann S, Ermentrout GB (2016) Sensory dynamics of visual hallucinations in the normal population. eLife Vol 5. e17072.

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