Do Psychedelics Produce Illusions By Inducing Night Vision?
Some of the mechanisms behind darkness adaptation overlap with illusory motion. These mechanisms may be tied to the mechanisms of psychedelic drugs. It may be that psychedelics amplify an endogenous night vision system, which causes certain visual distortions like illusory motion. Here is the evidence behind this possibility.
Most of you have probably heard that there are rods and cones in the eye. The rods deal with light levels, also known as luminance (which is basically brightness levels). The rods do not deal with color perception. Color perception is driven by the cones in the eye. The connection between psychedelics and illusory motion focuses on the mechanisms underlying rod-based perception.
The rods and cones send signals that travel through distinct visual systems, namely the dorsal and ventral streams respectively. The dorsal stream moves up the visual cortex and into the parietal lobe. This stream deals with “where” information like depth, location, and movement. This stream is non-colored. The other system, known as the ventral stream, moves from the visual cortex towards the temporal lobe. This stream deals with “what” information, such as object identification. This stream is colored.
Since we are focusing on the rods, we will focus on the dorsal stream which deals with location and motion perception. Location and motion are key here since psychedelic visuals involve modifications to both of these. People on psychedelics experience illusory motion. To see an example of an image that induces sober illusory motion, just look below! This is the rotating snake illusion.
