title: Dopamine Neurons Encoding Long-Term Memory of Object Value for Habitual Behavior.
abstract: Dopamine neurons promote learning by processing recent changes in reward values, such that reward may be maximized. However, such a flexible signal is not suitable for habitual behaviors that are sustained regardless of recent changes in reward outcome. We discovered a type of dopamine neuron in the monkey substantia nigra pars compacta (SNc) that retains past learned reward values stably. After reward values of visual objects are learned, these neurons continue to respond differentially to the objects, even when reward is not expected. Responses are strengthened by repeated learning and are evoked upon presentation of the objects long after learning is completed. These "sustain-type" dopamine neurons are confined to the caudal-lateral SNc and project to the caudate tail, which encodes long-term value memories of visual objects and guides gaze automatically to stably valued objects. This population of dopamine neurons thus selectively promotes learning and retention of habitual behavior.
authors.affiliation: Laboratory of Sensorimotor Research, National Eye Institute, National Institutes of Health, Bethesda, MD 20892, USA; Center for Neuroscience Imaging Research (CNIR), Institute for Basic Science (IBS), Suwon 440-746, Republic of Korea; Department of Biomedical Engineering, Sungkyunkwan University, Suwon 440-746, Republic of Korea. Electronic address: hyoung.f.kim@gmail.com.
authors.forename: Hyoung F
authors.initials: HF
authors.lastname: Kim
authors.affiliation: Laboratory of Sensorimotor Research, National Eye Institute, National Institutes of Health, Bethesda, MD 20892, USA.
authors.forename: Ali
authors.initials: A
authors.lastname: Ghazizadeh
authors.affiliation: Laboratory of Sensorimotor Research, National Eye Institute, National Institutes of Health, Bethesda, MD 20892, USA; Intramural Research Program, National Institute on Drug Abuse, National Institutes of Health, Bethesda, MD 20892, USA.
authors.forename: Okihide
authors.initials: O
authors.lastname: Hikosaka
mesh_terms: D000818:Animals; D001479:Basal Ganglia / Q000502:physiology; D001522:Behavior, Animal; D004298:Dopamine / Q000378:metabolism*; D006184:Habits; D008253:Macaca mulatta / Q000502:physiology*; D008297:Male; D057567:Memory, Long-Term; D009474:Neurons / Q000166:cytology* / Q000502:physiology; D009799:Ocular Physiological Phenomena
chemical_list: D004298:Dopamine