MDMA (ecstasy) causes lasting damage to the brain's serotonin system. In Dark Agouti rats, a single injection of MDMA at doses of 7.5, 15, or 30 mg/kg reduced the density of serotonin-producing axons throughout the brain 3 and 7 days later. Three days after treatment, a dose-dependent increase in the stress protein Hsp27 appeared in star-shaped glial cells (astrocytes) in several cortical areas and the hippocampus CA1 region, but not in other brain regions like the caudate putamen. The hippocampus CA1 showed both increased Hsp27 and another marker of glial activation (GFAP), suggesting particular vulnerability. High-dose MDMA also triggered Hsp72 in neurons, indicating effects beyond serotonin cells.
Multistable perception—where sensory ambiguity causes spontaneous alternations between two or more perceptual interpretations—occurs across many animal species. This review covers research on visual perceptual rivalry in insects, fish, reptiles, and primates, highlighting binocular rivalry and the Necker cube as examples. Common behavioral indicators of perceptual alternation appear across species. The comparative approach offers insights into how brains suppress conflicting sensory signals and generate shifts in perceptual dominance, suggesting that ambiguous sensation is a fundamental problem that has shaped brain evolution.