Over at motherboard, Brian Anderson ponders the underlying reason for geometric visual hallucinations.
"Acid, DMT, psilocybin, mescaline, ayahuasca, whatever—it's almost no matter. When you dose your head, why do your eyes pick up certain visual stimuli while blotting out others?"
Enter the Void- DMT trip
"researchers found a close relationship between form constants, those geometric patterns regularly observed in altered states of consciousness, and planforms, or the contours of objects seen from above. These results hinged on the "detailed speculation" of lateral connectivity in the visual cortex, brain activity central to our ability to recognize an object, its contours, and how it relates with other objects.
As such, a curious possibility emerged. If "the cortical mechanisms by which geometric hallucinations are generated" are indeed housed in the visual cortex, the researchers wrote, it stands to reason that those very mechanisms responsible for psychedelia's geometric visuals are fundamentally akin to those that allow humans to make sense of contours and edges."
Bonus, Oliver Sacks on hallucinations at TEDTalks.