Arvid Carlsson (1923-2018) was a Swedish pharmacologist and neuroscientist who won the Nobel Prize in Physiology or Medicine in 2000 for his discoveries concerning signal transduction in the nervous system. He is best known for his research on neurotransmitters, particularly dopamine, and their impact on Parkinson's disease and schizophrenia. Carlsson's work significantly contributed to the development of treatments for these neurological disorders, revolutionizing the understanding of how chemicals in the brain influence behavior and mental health. He made pioneering advancements in psychopharmacology, leaving a lasting legacy in the field of neuroscience.