From Scientific American:
Zeroing in on a group of cells in a high layer of the cortex, a team of researchers from Mount Sinai School of Medicine, Columbia University and the New York State Psychiatric Institute may finally have found the cause of the swirling textures, blurry visions and signal-crossing synesthesia brought on by hallucinogenic drugs like LSD, peyote and “‘shrooms.” The group, which published its findings in this week’s issue of Neuron, may have settled a long-simmering debate over how psychedelic drugs distort human perception.
After testing many candidate regions, the researchers localized the effects of hallucinogens to the pyramidal neurons in layer V of the somatosensory cortex, a relatively high-level region known to modulate the activity of other sections in the cortex and subcortical areas. Using what he calls an “imperfect but usual analogy,” Stuart Sealfon, a neurologist at Mount Sinai Hospital in New York City likens the receptors to a lock into which both hallucinogenic and nonhallucinogenic keys fit.
More here.