Sat, 26 Jul 2008 07:37:02 BST CiteULike: nelmor's serotonin http://www.citeulike.org/user/nelmor/tag/serotonin CiteULike.org en-gb Copyright © 2004-2008 citeulike.org http://www.citeulike.org/user/nelmor/article/2799580 <i>J. Neurosci., Vol. 28, No. 20. (14 May 2008), pp. 5331-5343.</i><br /><br />The dopamine system has been thought to play a central role in guiding behavior based on rewards. Recent pharmacological studies suggest that another monoamine neurotransmitter, serotonin, is also involved in reward processing. To elucidate the functional relationship between serotonin neurons and dopamine neurons, we performed single-unit recording in the dorsal raphe nucleus (DRN), a major source of serotonin, and the substantia nigra pars compacta, a major source of dopamine, while monkeys performed saccade tasks in which the position of the target indicated the size of an upcoming reward. After target onset, but before reward delivery, the activity of many DRN neurons was modulated tonically by the expected reward size with either large- or small-reward preference, whereas putative dopamine neurons had phasic responses and only preferred large rewards. After reward delivery, the activity of DRN neurons was modulated tonically by the received reward size with either large- or small-reward preference, whereas the activity of dopamine neurons was not modulated except after the unexpected reversal of the position-reward contingency. Thus, DRN neurons encode the expected and received rewards, whereas dopamine neurons encode the difference between the expected and received rewards. These results suggest that the DRN, probably including serotonin neurons, signals the reward value associated with the current behavior. 10.1523/JNEUROSCI.0021-08.2008 Reward-Dependent Modulation of Neuronal Activity in the Primate Dorsal Raphe Nucleus Kae Nakamura Masayuki Matsumoto Okihide Hikosaka doi:10.1523/JNEUROSCI.0021-08.2008 J. Neurosci., Vol. 28, No. 20. (14 May 2008), pp. 5331-5343. 2008-05-14T17:09:11-00:00 2008 J. Neurosci. 28 20 5331 5343 dopamine monkeys raphe reward serotonin http://www.citeulike.org/user/nelmor/article/2712965 <i>J. Neurosci., Vol. 28, No. 17. (23 April 2008), pp. 4528-4532.</i><br /><br />Previous animal experiments have shown that serotonin is involved in the control of impulsive choice, as characterized by high preference for small immediate rewards over larger delayed rewards. Previous human studies under serotonin manipulation, however, have been either inconclusive on the effect on impulsivity or have shown an effect in the speed of action-reward learning or the optimality of action choice. Here, we manipulated central serotonergic levels of healthy volunteers by dietary tryptophan depletion and loading. Subjects performed a "dynamic" delayed reward choice task that required a continuous update of the reward value estimates to maximize total gain. By using a computational model of delayed reward choice learning, we estimated the parameters governing the subjects' reward choices in low-, normal, and high-serotonin conditions. We found an increase of proportion in small reward choices, together with an increase in the rate of discounting of delayed rewards in the low-serotonin condition compared with the control and high-serotonin conditions. There were no significant differences between conditions in the speed of learning of the estimated delayed reward values or in the variability of reward choice. Therefore, in line with previous animal experiments, our results show that low-serotonin levels steepen delayed reward discounting in humans. The combined results of our previous and current studies suggest that serotonin may adjust the rate of delayed reward discounting via the modulation of specific loops in parallel corticobasal ganglia circuits. 10.1523/JNEUROSCI.4982-07.2008 Low-Serotonin Levels Increase Delayed Reward Discounting in Humans Nicolas Schweighofer Mathieu Bertin Kazuhiro Shishida Yasumasa Okamoto Saori Tanaka Shigeto Yamawaki Kenji Doya doi:10.1523/JNEUROSCI.4982-07.2008 J. Neurosci., Vol. 28, No. 17. (23 April 2008), pp. 4528-4532. 2008-04-24T13:04:57-00:00 2008 J. Neurosci. 28 17 4528 4532 discounting human reward serotonin http://www.citeulike.org/user/nelmor/article/2191290 <i>Trends in Cognitive Sciences, Vol. 12, No. 1. (January 2008), pp. 31-40.</i><br /><br />5-Hydroxytryptamine (5-HT, serotonin) has long been implicated in a wide variety of emotional, cognitive and behavioural control processes. However, its precise contribution is still not well understood. Depletion of 5-HT enhances behavioural and brain responsiveness to punishment or other aversive signals, while disinhibiting previously rewarded but now punished behaviours. Findings suggest that 5-HT modulates the impact of punishment-related signals on learning and emotion (aversion), but also promotes response inhibition. Exaggerated aversive processing and deficient response inhibition could underlie distinct symptoms of a range of affective disorders, namely stress- or threat-vulnerability and compulsive behaviour, respectively. We review evidence from studies with human volunteers and experimental animals that begins to elucidate the neurobiological systems underlying these different effects. Serotoninergic regulation of emotional and behavioural control processes Roshan Cools Angela Roberts Trevor Robbins doi:10.1016/j.tics.2007.10.011 Trends in Cognitive Sciences, Vol. 12, No. 1. (January 2008), pp. 31-40. 2008-01-03T12:22:35-00:00 2008 Trends in Cognitive Sciences 12 1 31 40 aversive review reward serotonin http://www.citeulike.org/user/nelmor/article/2065864 <i>Neural Netw., Vol. 15, No. 4. (June 2002), pp. 495-506.</i> Metalearning and neuromodulation Kenji Doya doi:10.1016/S0893-6080(02)00044-8 Neural Netw., Vol. 15, No. 4. (June 2002), pp. 495-506. 2007-12-06T08:50:56-00:00 2002 Neural Netw. 0893-6080 15 4 495 506 Elsevier Science Ltd. acetylcholine dopamine learning model serotonin theory http://www.citeulike.org/user/nelmor/article/1704404 <i>J Comp Neurol, Vol. 243, No. 3. (15 January 1986), pp. 363-380.</i><br /><br />The intranuclear organization of divergently projecting neurons of the midbrain raphe in the rat was studied by using double retrograde axonal tracing. Paired injections of the tracers N-[acetyl-3H] WGA and horseradish peroxidase were made within known projection targets of the midbrain raphe (caudate-putamen, amygdala, hippocampus, substantia nigra, and locus coeruleus). After injections of either tracer in the aforementioned targets, retrograde labeled neurons were found mainly ipsilaterally and within midline portions of the dorsal raphe nucleus, its caudal B6 portion, and within the linear and superior central nuclei of the median raphe complex. There are discrete intranuclear distributions of raphe neurons that project to these forebrain and brainstem sites, and there is an overall rostrocaudal topographic order within the raphe with neurons projecting to the neostriatum, amygdala, and substantia nigra residing most rostrally and neurons projecting to the hippocampus and/or locus coeruleus occupying caudal portions of the B6 and superior central nuclei. Such distributions of projection neurons suggest the existence of an "encephalotopic" intranuclear organization within the raphe; that is, each central nervous system structure that receives midbrain raphe projections has its own unique representation within a topographically distinct portion of one or more of the raphe subgroups. These findings suggest an overall functional organization within the midbrain raphe nuclear complex whereby rostral portions are associated with the basal ganglia and related nuclei, and caudal portions relate to the limbic system. An intermediate representation of amygdala-projecting raphe neurons functionally conjoins the two. Collateralized neurons are found within complex zones of overlap in the topographically organized distributions of raphe neurons projecting to functionally related structures. The organization of divergent axonal projections from the midbrain raphe nuclei in the rat. H Imai DA Steindler ST Kitai doi:10.1002/cne.902430307 J Comp Neurol, Vol. 243, No. 3. (15 January 1986), pp. 363-380. 2007-09-28T09:18:25-00:00 1986 J Comp Neurol 0021-9967 243 3 363 380 amygdala anatomy raphe serotonin snc striatum http://www.citeulike.org/user/nelmor/article/1610336 <i>Brain Res, Vol. 243, No. 1. (8 July 1982), pp. 49-58.</i><br /><br />Similar to other afferents to rat caudate-putamen, stimulation of the dorsal raphe nucleus evokes a series of 3 responses which can be recorded intracellularly. An initial depolarization is followed by a long-lasting inhibition which is, in turn, terminated by another period of depolarization. Pharmacological manipulations demonstrate that the initial depolarizing potential is serotonergic. Depletion of serotonin by means of prior treatment with para-chlorophenylalanine leads to a reduction in the amplitude of the depolarization which can be evoked by maximal stimulation of dorsal raphe. Neither the long-lasting hyperpolarization nor the late excitation which follow the initial depolarization is affected. Replacement of serotonin in levels by injection of 5-hydroxytryptophan results in a restoration of the amplitude of the depolarizing response. The latency of the initial depolarization is, however, unchanged in serotonin-depleted animals. This together with the observation in some cells of a component of the initial depolarization resistant to para-chlorophenylalanine treatment, suggests that there is a non-serotonergic excitation which precedes that mediated by serotonin. Serotonergic excitation from dorsal raphe stimulation recorded intracellularly from rat caudate-putamen. MR Park JA Gonzales-Vegas ST Kitai Brain Res, Vol. 243, No. 1. (8 July 1982), pp. 49-58. 2007-08-31T07:37:35-00:00 1982 Brain Res 0006-8993 243 1 49 58 anatomy physiology raphe serotonin striatum http://www.citeulike.org/user/nelmor/article/1598210 <i>(18 April 1989)</i> Drugs as Tools in Neurotransmitter Research (Neuromethods) Alan Boulton Glen Baker (18 April 1989) 2007-08-28T09:41:12-00:00 1989 Humana Press acetylcholine dopamine drugs nicotine physiology serotonin http://www.citeulike.org/user/nelmor/article/1023635 <i>Neuropsychopharmacology, Vol. aop, No. current.</i> Endogenous Serotonin Excites Striatal Cholinergic Interneurons via the Activation of 5-HT 2C, 5-HT6, and 5-HT7 Serotonin Receptors: Implications for Extrapyramidal Side Effects of Serotonin Reuptake Inhibitors Paola Bonsi Dario Cuomo Jun Ding Giuseppe Sciamanna Sasha Ulrich Anne Tscherter Giorgio Bernardi James Surmeier Antonio Pisani doi:10.1038/sj.npp.1301294 Neuropsychopharmacology, Vol. aop, No. current. 2007-01-03T21:16:49-00:00 Neuropsychopharmacology 0893-133X aop current Nature Publishing Group acetylcholine serotonin striatum tan http://www.citeulike.org/user/nelmor/article/1017908 <i>Neuropsychopharmacology, Vol. aop, No. current.</i> Increased Expression of 5-HT6 Receptors in the Rat Dorsomedial Striatum Impairs Instrumental Learning Ellen Mitchell Timothy Sexton John Neumaier doi:10.1038/sj.npp.1301284 Neuropsychopharmacology, Vol. aop, No. current. 2006-12-28T00:49:12-00:00 Neuropsychopharmacology 0893-133X aop current Nature Publishing Group gene-transfer learning rats serotonin striatum