Garret D. Stuber,1 Marianne Klanker,2 Bram de Ridder,1 M. Scott Bowers,1 Ruud N. Joosten,2 Matthijs G. Feenstra,2 Antonello Bonci1,3* Using sensory information for the prediction of future events is essential for survival. Midbrain dopamine neurons are activated by environmental cues that predict rewards, but the cellular mechanisms that underlie this phenomenon remain elusive. We used in vivo voltammetry and in vitro patch-clamp electrophysiology to show that both dopamine release to reward predictive cues and enhanced synaptic strength onto dopamine neurons develop over the course of cue-reward learning. Increased synaptic strength was not observed after stable behavioral responding. Thus, enhanced synaptic strength onto dopamine neurons may act to facilitate the transformation of neutral environmental stimuli to salient reward-predictive cues. 1 Ernest Gallo Clinic and Research Center, Department of Neurology, University of California, San Francisco, Emeryville, CA 94608, USA. 2 Netherlands Institute for Neuroscience, an Institute of the Royal Netherlands Academy of Arts and Sciences, Amsterdam, Netherlands. 3 Wheeler Center for the Neurobiology of Drug Addiction, University of California, San Francisco, San Francisco, CA 94143, USA. * To whom correspondence should be addressed. E-mail: antonello.bonci@ucsf.edu Read the Full Text -------------------------------------------------------------------------------- The editors suggest the following Related Resources on Science sites: In Science Signaling EDITORS' CHOICE Neuroscience Dopaminergic Synapse Plasticity Peter Stern (23 September 2008) Sci. Signal. 1 (38), ec332. [DOI: 10.1126/scisignal.138ec332] | Abstract »

Daphna Shohamy1, 3, , and Anthony D. Wagner1, 2 1Department of Psychology, Stanford University, Jordan Hall Bldg. 420, Stanford, CA 94305-2130, USA 2Neuroscience Program, Stanford University, Jordan Hall Bldg. 420, Stanford, CA 94305-2130, USA 3Department of Psychology, Columbia University, Schermerhorn Hall, New York, NY 10027, USA Accepted 19 September 2008. Published: October 22, 2008. Available online 19 October 2008. References and further reading may be available for this article. To view references and further reading you must purchase this article. Summary Decisions are often guided by generalizing from past experiences. Fundamental questions remain regarding the cognitive and neural mechanisms by which generalization takes place. Prior data suggest that generalization may stem from inference-based processes at the time of generalization. By contrast, generalization may emerge from mnemonic processes occurring while premise events are encoded. Here, participants engaged in a two-phase learning and generalization task, wherein they learned a series of overlapping associations and subsequently generalized what they learned to novel stimulus combinations. Functional MRI revealed that successful generalization was associated with coupled changes in learning-phase activity in the hippocampus and midbrain (ventral tegmental area/substantia nigra). These findings provide evidence for generalization based on integrative encoding, whereby overlapping past events are integrated into a linked mnemonic representation. Hippocampal-midbrain interactions support the dynamic integration of experiences, providing a powerful mechanism for building a rich associative history that extends beyond individual events. Author Keywords: SYSNEURO; SIGNALING; SYSBIO

The owl can discriminate changes in the location of sound sources as small as 3 degrees and can aim its head to within 2 degrees of a source. A typical neuron in its midbrain space map has a spatial receptive field that spans 40 degrees?a width that is many times the behavioural threshold. Here we have quantitatively examined the relationship between neuronal activity and perceptual acuity in the auditory space map in the barn owl midbrain. By analysing changes in firing rate resulting from small changes of stimulus azimuth, we show that most neurons can reliably signal changes in source location that are smaller than the behavioural threshold. Each source is represented in the space map by a focus of activity in a population of neurons. Displacement of the source causes the pattern of activity in this population to change. We show that this change predicts the owl?s ability to detect a change in source location.

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