Thu, 21 Aug 2008 14:04:49 BST CiteULike: nelmor's Paton http://www.citeulike.org/user/nelmor/author/Paton CiteULike.org en-gb Copyright © 2004-2008 citeulike.org http://www.citeulike.org/user/nelmor/article/1679005 <i>Neuron, Vol. 55, No. 6. (20 September 2007), pp. 970-984.</i><br /><br />Summary Animals and humans learn to approach and acquire pleasant stimuli and to avoid or defend against aversive ones. However, both pleasant and aversive stimuli can elicit arousal and attention, and their salience or intensity increases when they occur by surprise. Thus, adaptive behavior may require that neural circuits compute both stimulus valence--or value--and intensity. To explore how these computations may be implemented, we examined neural responses in the primate amygdala to unexpected reinforcement during learning. Many amygdala neurons responded differently to reinforcement depending upon whether or not it was expected. In some neurons, this modulation occurred only for rewards or aversive stimuli, but not both. In other neurons, expectation similarly modulated responses to both rewards and punishments. These different neuronal populations may subserve two sorts of processes mediated by the amygdala: those activated by surprising reinforcements of both valences--such as enhanced arousal and attention--and those that are valence-specific, such as fear or reward-seeking behavior. Expectation Modulates Neural Responses to Pleasant and Aversive Stimuli in Primate Amygdala Marina Belova Joseph Paton Sara Morrison Daniel Salzman doi:10.1016/j.neuron.2007.08.004 Neuron, Vol. 55, No. 6. (20 September 2007), pp. 970-984. 2007-09-20T13:17:19-00:00 2007 Neuron 55 6 970 984 amygdala aversive expectation reward http://www.citeulike.org/user/nelmor/article/675037 <i>Current Opinion in Neurobiology, Vol. 15, No. 6. (December 2005), pp. 721-729.</i><br /><br />Sensory cues in the environment can predict the availability of reward. Through experience, humans and animals learn these predictions and use them to guide their actions. For example, we can learn to discriminate chanterelles from ordinary champignons through experience. Assuming the development of a taste for the complex and lingering flavors of chanterelles, we therefore learn to value the same action -- picking mushrooms -- differentially depending upon the appearance of a mushroom. One major goal of cognitive neuroscience is to understand the neural mechanisms that underlie this sort of learning. Because the acquisition of rewards motivates much behavior, recent efforts have focused on describing the neural signals related to learning the value of stimuli and actions. Neurons in the basal ganglia, in midbrain dopamine areas, in frontal and parietal cortices and in other brain areas, all modulate their activity in relation to aspects of learning. By training monkeys on various behavioral tasks, recent studies have begun to characterize how neural signals represent distinct processes, such as the timing of events, motivation, absolute (objective) and relative (subjective) valuation, and the formation of associative links between stimuli and potential actions. In addition, a number of studies have either further characterized dopamine signals or sought to determine how such signaling might interact with target structures, such as the striatum and rhinal cortex, to underlie learning. Beetles, boxes and brain cells: neural mechanisms underlying valuation and learning Daniel Salzman Marina Belova Joseph Paton doi:10.1016/j.conb.2005.10.016 Current Opinion in Neurobiology, Vol. 15, No. 6. (December 2005), pp. 721-729. 2006-05-30T15:53:13-00:00 2005 Current Opinion in Neurobiology 15 6 721 729 learning reinforcement-learning review value http://www.citeulike.org/user/nelmor/article/506468 <i>Nature, Vol. 439, No. 7078. (16 February 2006), pp. 865-870.</i> The primate amygdala represents the positive and negative value of visual stimuli during learning Joseph Paton Marina Belova Sara Morrison Daniel Salzman doi:10.1038/nature04490 Nature, Vol. 439, No. 7078. (16 February 2006), pp. 865-870. 2006-02-15T19:40:49-00:00 2006 Nature 439 7078 865 870 amygdala aversive reward