Hallucinations have led everyone from shamans to acid gurus to believe they were getting a glimpse into the spirit world. Jack Cowan says they may actually be getting a peek into their own brains. Cowan is the mathematician and neuroscientist featured in the latest episode of Clever Apes, talking about how the patterns in those hallucinations actually reflect the structure and behavior of networks in our heads.

We’ll get to the science in a moment, but it’s worth considering how entwined these hallucinations may be into the human experience. As Cowan mentions, some anthropologists believe that much of cave art is hallucinatory, as demonstrated in this presentation Cowan put together. I’ll leave it to the reader to decide whether these images are conclusive evidence that the cave art is drawn from hallucinatory patterns (seems to me that some are more convincing than others). Anthropologist David Lewis Williams thought so, and even argued that hallucinations must then be a major source of humanity’s spiritual and religious development. So in that sense, they do give insight into the spirit world – if only to suggest that the spirit world originates in the cells of our sensory cortices.

It’s worth noting, also, that hallucinations aren’t confined to the visual world. We can experience audio hallucinations (which may of course be wrapped up in psychedelic music … see Jim DeRogatis’s fine history here), olfactory hallucinations – even tactile hallucinations.

As for those visual patterns: they certainly seem to recur in plenty of places. To see them, eat some magic mushrooms or go have a near-death experience. Of course, you could also just pay half-attention as you’re drifting off to sleep. Or simply press on your eyeballs a little. Totally your call. But the key, Cowan says, is that the brain produces these patterns as it’s passing through a state of instability – whether it’s semi-sleep or a neurochemical imbalance brought on by drugs.

Basically, as excitation ripples through our neural networks, it makes actual patterns in there – often stripes or a regular series of blobs – of firing or resting neurons. Then, because of the way our visual network is designed, those patterns appear to our eyes as spirals, funnels and tunnels, honeycombs or cobwebs. In fact, those four patterns seem to be pretty much it: Our brain architecture is capable of producing only variations on those four themes.

But Cowan points out that the excitations that cause the hallucinations don’t stop in the brain’s sensory areas – they propagate deeper into areas connected with emotions, memory and self-image. That, added to the fact that they are associated with passing from one state into another (sober to tripping, awake to asleep, alive to dead), may contribute to the profundity we often ascribe to them. And perhaps there is something profound there after all: the idea that the same pattern-making mechanisms are at work in our minds as in clouds, or sands worked by the tides. That is pretty deep, man.

And kids, say no to drugs.

Subscribe to our podcast, follow us on Twitter and find us on Facebook.