Hallucinogen mescaline changed how awake rats’ brains handled incoming signals. In a new study in Neuroscience Bulletin, Noah Cavallaro and colleagues found reduced cerebellar activity and stronger links to memory and sensory regions after the drug.
The first experiment involved 24 adult rats, split evenly by sex at 12 females and 12 males. Half received mescaline and half got a control solution, while their brains were scanned with functional magnetic resonance imaging after the animals had been gradually accustomed to the scanner without anesthesia.
Noah Cavallaro on the hippocampus
Cavallaro, a pharmaceutical scientist and the study’s first author, said the hippocampal connection was particularly striking. He described a possible filtering failure: if the cerebellum stops screening input while connections to memory, sensory relay, and body-sense regions rise, raw sensory and internal signals can reach places that normally get a processed signal.
Mescaline reduced activity within parts of the cerebellum and strengthened communication between its deep nuclei and the hippocampus, thalamus, somatosensory cortex, and midbrain. Under normal conditions, the hippocampus and cerebellar nuclei had essentially no functional connection, but after mescaline the cerebellar nuclei connected to seven of nine hippocampal subregions.
Neuroscience Bulletin rat scans
The rats were exposed to almond scent in the first experiment. Control rats showed a clear brain response to the smell, while rats given mescaline showed almost no response. That pattern fits the study’s idea that the drug may alter how the brain responds to incoming sensory information.
The cerebellum is usually linked to movement and balance, yet this study ties it to sensory filtering, memory, and altered perception under mescaline. Cavallaro’s explanation points to a specific network shift rather than a broad shutdown: less local cerebellar activity, but more communication with regions that handle memory, relay, and bodily sensation.
16-rat prepulse test
In a separate experiment involving 16 rats, the team tested prepulse inhibition. The study does not report those results here, leaving the cerebellar imaging findings as the clearest readout from the new work.
For now, the strongest takeaway is narrow and practical: the brain map suggests mescaline does not simply act as a general stimulant or blocker. It appears to redirect filtered input through a specific network, and the hippocampal link is the one Cavallaro called out first.
