Final answer:
Depressant drugs work on the "new" brain by decreasing neurotransmission levels, while stimulant drugs work on the "new" brain by increasing alertness and wakefulness. Psychedelics, however, work more on the "old" brain and can cause hallucinations and perceptual anomalies.
Step-by-step explanation:
Depressant drugs work mostly on the "new" brain by lowering neurotransmission levels, reducing arousal or stimulation in various areas of the brain. Examples of depressant drugs include ethanol (in alcoholic beverages) and opioids such as codeine and heroin. On the other hand, stimulant drugs work on the "new" brain by stimulating the brain, increasing alertness and wakefulness. Examples of stimulant drugs include caffeine, nicotine, cocaine, and amphetamines such as Adderall.
Psychedelics, on the other hand, work more on the "old" brain. They affect neurotransmitter systems and can cause hallucinations and other perceptual anomalies. Examples of psychedelics include LSD, mescaline, nitrous oxide, and psilocybin.