Dopamine gating of glutamatergic sensorimotor and incentive motivational input signals to the striatum

Dopamine (DA) neurons of the substantia nigra (SN) and ventral tegmental area (VTA) respond to a wide category of salient stimuli. Activation of SN and VTA DA neurons, and consequent release of nigrostriatal and mesolimbic DA, modulates the processing of concurrent glutamate inputs to dorsal and ventral striatal target regions. According to the view described here, this occurs under conditions of unexpected environmental change regardless of whether that change is rewarding or aversive. Nigrostriatal and mesolimbic DA activity gates the input of sensory, motor, and incentive motivational (e.g. reward) signals to the striatum. In light of recent single-unit and brain imaging data, it is suggested that the striatal reward signals originate in the orbitofrontal cortex and basolateral amygdala (BLA), regions that project strongly to the striatum. A DA signal of salient unexpected event occurrence, from this framework, gates the throughput of the orbitofrontal glutamate reward input to the striatum just as it gates the throughput of corticostriatal sensory and motor signals needed for normal response execution. Processing of these incoming signals is enhanced when synaptic DA levels are high, because DA enhances the synaptic efficacy of strong concurrent glutamate inputs while reducing the efficacy of weak glutamate inputs. The impairments in motor performance and incentive motivational processes that follow from nigrostriatal and mesolimbic DA loss can be understood in terms of a single mechanism: abnormal processing of sensorimotor and incentive motivation-related glutamate input signals to the striatum

Principles of Behavioral Neuroscience

How does brain activity give rise to sleep, dreams, learning, memory, and language? Do drugs like cocaine and heroin tap into the same neurochemical systems that evolved for life's natural rewards? What are the powerful new tools of molecular biology that are revolutionizing neuroscience? This undergraduate textbook explores the relation between brain, mind, and behavior. It clears away the extraneous detail that so often impedes learning, and describes critical concepts step by step, in straightforward language. Rich illustrations and thought-provoking review questions further illuminate the relations between biological, behavioral, and mental phenomena. With writing that is focused and engaging, even the more challenging topics of neurotransmission and neuroplasticity become enjoyable to learn. While this textbook filters out non-critical details, it includes all key information, allowing readers to remain focused and enjoy the feeling of mastery that comes from a grounded understanding of a topic, from its fundamentals to its implications.</jats:p

NMDA receptor-dependent plasticity in the nucleus accumbens connects reward-predictive cues to approach responses

AbstractLearning associations between environmental cues and rewards is a fundamental adaptive function. Via such learning, reward-predictive cues come to activate approach to locations where reward is available. The nucleus accumbens (NAc) is essential for cued approach behavior in trained subjects, and cue-evoked excitations in NAc neurons are critical for the expression of this behavior. Excitatory synapses within the NAc undergo synaptic plasticity that presumably contributes to cued approach acquisition, but a direct link between synaptic plasticity within the NAc and the development of cue-evoked neural activity during learning has not been established. Here we show that, with repeated cue-reward pairings, cue-evoked excitations in the NAc emerge and grow in the trials prior to the detectable expression of cued approach behavior. We demonstrate that the growth of these signals requires NMDA receptor-dependent plasticity within the NAc, revealing a neural mechanism by which the NAc participates in learning of conditioned reward-seeking behaviors.</jats:p