Acid: Common street name for LSD.

Angel dust: Common street name for PCP.

Cerebral cortex: Region of the brain responsible for cognitive functions including reasoning, mood, and perception of stimuli.

Dissociative anesthetic: Compound, such as phencyclidine or ketamine, that produces an anesthetic effect characterized by a feeling of being detached from the physical self.

DXM: Common street name for dextromethorphan.

Flashback: Slang term for HPPD (see below).

Glutamate: A neurotransmitter associated with pain, memory, and response to changes in the environment.

Hallucinogen: A drug that produces hallucinations - distortion in perception of sights and sounds - and disturbances in emotion, judgment, and memory.

HPPD: Hallucinogen persisting perception disorder; the spontaneous and sometimes continuous recurrence of perceptual effects of LSD long after an individual has ingested the drug.

Ketamine: Dissociative anesthetic abused for its mind-altering effects and sometimes used to facilitate sexual assault.

Locus ceruleus: Region of the brain that receives and processes sensory signals from all areas of the body.

Neurotransmitter: Chemical compound that acts as a messenger to carry signals or stimuli from one nerve cell to another.

NMDA: N-methyl-D-aspartate, a chemical compound that reacts with glutamate receptors on nerve cells.

PCP: Phencyclidine, a dissociative anesthetic abused for its mind-altering effects.

Persistent psychosis: Unpredictable and long-lasting visual disturbances, dramatic mood swings, and hallucinations experienced by some LSD users after they have discontinued use of the drug.

Robo: Common street name for dextromethorphan.

Serotonin: A neurotransmitter that causes a very broad range of effects on perception, movement, and the emotions by modulating the actions of other neurotransmitters in most parts of the brain.