eric nestler, through research on mice, his work his illuminated the molecular basis of drug addiction. he is chair of the department of neuroscience and director of the brain institute at mount sinai medical center here in new york. and once again, my co-host is dr. eric kandel. he is a nobel laureate, as you know by now. also a professor at columbia university and a howard hughes medical investigator and, as you also know, a great friend of this series and the man who has helped us once this miraculous organ. welcome. >> pleasure to be here as always. >> so as we go through this, as we have been gone from understanding visual perception and understanding the developing brain and the aging brain and now we come to emotion. tell me what we mean and how does the brain connect to emotion? >> well, as always, you outlined it extremely well. emotions are a family of subjective experiences, states of readiness that we all experience in response to significant people and situations in our lives and emotions are designed to enhance our opportunity for happiness and decrease our exposure to mi