Marijuana's effects on the brain are that it changes the way sensory information gets into and is acted on by the hippocampus, which is crucial to learning, memory, and experiences with sensory feelings, as well as emotions and motivations. Neurons in the hippocampus are suppressed by the active ingredient in marijuana, THC. It also can have some effects similar to those of other major drugs. The thing is, all of these effects are effects from regular marijuana use, which is why I tried it once and only once.