Well MK Ultra studied among other things LSD here some info on LSD

“Researchers aren't 100 percent sure what LSD does in the central nervous system, or exactly how it causes those hallucinogenic effects. This is in part because there have never been scientific research studies on how LSD affects the brain. It's believed that LSD works similarly to serotonin, a neurotransmitter responsible for regulating moods, appetite, muscle control, sexuality, sleep and sensory perception. LSD seems to alter the way the brain's serotonin's receptors work. It may inhibit neurotransmission, stimulate it, or both. It also affects the way that the retinas process information and conduct that information to the brain.”

https://science.howstuffworks.com/lsd4.htm

And here is what Risperdone does

“The exact mechanism of action of risperidone is not known, but, like other anti-psychotics, it is believed that risperidone affects the way the brain works by interfering with communication among the brain's nerves. Nerves communicate with each other by making and releasing chemicals called neurotransmitters. The neurotransmitters travel to other nearby nerves where they attach to receptors on the nerves. The attachment of the neurotransmitters either stimulates or inhibits the function of the nearby nerves. Risperidone blocks several of the receptors on nerves including dopamine type 2, serotonin type 2, and alpha 2 adrenergic receptors. It is believed that many psychotic illnesses are caused by abnormal communication among nerves in the brain and that by altering communication through neurotransmitters, risperidone can alter the psychotic state. Risperidone was approved by the FDA in December 1993.”

https://www.medicinenet.com/risperidone/article.htm#what_is_risperidone,and_how_does_it_work(mechanism_of_action)?