151
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Phillips GD, Hitchcott PK. Blockade of the acquisition, but not expression, of associative learning by pre-session intra-amygdala R(+) 7-OH-DPAT. Psychopharmacology (Berl) 2009; 203:161-73. [PMID: 18949458 DOI: 10.1007/s00213-008-1382-6] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/28/2008] [Accepted: 10/13/2008] [Indexed: 12/17/2022]
Abstract
RATIONALE Two issues were addressed regarding the effects of amygdala dopamine manipulations on associative learning: first, an apparent contradiction between the effects of post- vs. pre-session dopaminergic manipulations and second, the ability of dopaminergic infusions to affect association formation vs. its expression following extended training. OBJECTIVES The ability of pre-session infusions of a dopamine receptor agonist (R(+) 7-OH-DPAT) to inhibit acquisition of a conditioned approach response was examined and compared with the same manipulation following overtraining. Further experiments extended these findings. MATERIALS AND METHODS Experiment 1 infused pre-session intra-amygdala R(+) 7-OH-DPAT (0, 0.1, 1 nmol) during conditioned approach acquisition. Experiment 2 applied pre-session intra-amygdala R(+) 7-OH-DPAT (0, 0.01, 0.1, 1 nmol) during expression of the same response, once well learned. Experiment 3 required the inhibition of a conditioned approach response following unconditioned stimulus (US) removal. Experiment 4 examined the ability of animals with prior drug experience to acquire a conditioned response to a novel stimulus. RESULTS Experiments 1-3 showed that pre-session amygdala R(+) 7-OH-DPAT impaired acquisition of either excitatory or inhibitory conditioned responding, but was ineffective following overtraining. Drug-induced impairments in acquisition of a specific conditioned stimulus (CS)-US relationship continued well beyond the cessation of drug treatment, but were found not to transfer to an alternate CS in Experiment 4. CONCLUSIONS Pre-session dopamine receptor activation within the amygdala may impair the acquisition, but not expression, of CS-US associations. Enhanced learning reported earlier following post-session dopamine receptor activation may occur indirectly through reduced interference with the consolidation of recent learning.
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Affiliation(s)
- Gavin D Phillips
- Department of Psychology, University of York, Heslington, York, YO10 5DD, UK.
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152
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Esclassan F, Coutureau E, Di Scala G, Marchand AR. Differential contribution of dorsal and ventral hippocampus to trace and delay fear conditioning. Hippocampus 2009; 19:33-44. [PMID: 18683846 DOI: 10.1002/hipo.20473] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Trace conditioning relies on the maintained representation of a stimulus across a trace interval, and may involve a persistent trace of the conditioned stimulus (CS) and/or a contribution of contextual conditioning. The role of hippocampal structures in these two types of conditioning was studied by means of pretraining lesions and reversible inactivation of the hippocampus in rats. Similar levels of conditioning to a tone CS and to the context were obtained with a trace interval of 30 s. Neurotoxic lesions of the whole hippocampus or reversible muscimol inactivation of the ventral hippocampus impaired both contextual and tone freezing in both trace- and delay-conditioned rats. Dorsal hippocampal injections impaired contextual freezing and trace conditioning, but not delay conditioning. No dissociation between trace and contextual conditioning was observed under any of these conditions. Altogether, these data indicate that the ventral and dorsal parts of the hippocampus compute different aspects of trace conditioning, with the ventral hippocampus being involved in fear and anxiety processes, and the dorsal hippocampus in the temporal and contextual aspects of event representation.
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Affiliation(s)
- Frederic Esclassan
- Université de Bordeaux, Centre de Neurosciences Intégratives et Cognitives, C.N.R.S. UMR 5228, Talence, France
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153
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Sweatt JD. Experience-dependent epigenetic modifications in the central nervous system. Biol Psychiatry 2009; 65:191-7. [PMID: 19006788 PMCID: PMC3090137 DOI: 10.1016/j.biopsych.2008.09.002] [Citation(s) in RCA: 243] [Impact Index Per Article: 16.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/02/2008] [Revised: 08/06/2008] [Accepted: 09/03/2008] [Indexed: 10/21/2022]
Abstract
This mini-review describes recent discoveries demonstrating that experience can drive the production of epigenetic marks in the adult nervous system and that the experience-dependent regulation of epigenetic molecular mechanisms in the mature central nervous system participates in the control of gene transcription underlying the formation of long-term memories. In the mammalian experimental systems investigated thus far, epigenetic mechanisms have been linked to associative fear conditioning, extinction of learned fear, and hippocampus-dependent spatial memory formation. Intriguingly, in one experimental system epigenetic marks at the level of chromatin structure (histone acetylation) have been linked to the recovery of memories that had seemed to be "lost" (i.e., not available for recollection). Environmental enrichment has long been known to have positive effects on memory capacity, and recent studies have suggested that these effects are at least partly due to the recruitment of epigenetic mechanisms by environmental enrichment. Finally, an uncoupling of signal transduction pathways from the regulation of epigenetic mechanisms in the nucleus has been implicated in the closure of developmental critical periods. Taken together, these eclectic findings suggest a new perspective on experience-dependent dynamic regulation of epigenetic mechanisms in the adult nervous system and their relevance to biological psychiatry.
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Affiliation(s)
- J. David Sweatt
- Department of Neurobiology and Evelyn F. McKnight Brain Institute, University of Alabama at Birmingham, Birmingham, AL 35294, USA
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154
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Maren S. Pavlovian fear conditioning as a behavioral assay for hippocampus and amygdala function: cautions and caveats. Eur J Neurosci 2009; 28:1661-6. [PMID: 18973583 DOI: 10.1111/j.1460-9568.2008.06485.x] [Citation(s) in RCA: 183] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Pavlovian fear conditioning has become an important model for investigating the neural substrates of learning and memory in rats, mice and humans. The hippocampus and amygdala are widely believed to be essential for fear conditioning to contexts and discrete cues, respectively. Indeed, this parsing of function within the fear circuit has been used to leverage fear conditioning as a behavioral assay of hippocampal and amygdala function, particularly in transgenic mouse models. Recent work, however, blurs the anatomical segregation of cue and context conditioning and challenges the necessity for the hippocampus and amygdala in fear learning. Moreover, nonassociative factors may influence the performance of fear responses under a variety of conditions. Caution must therefore be exercised when using fear conditioning as a behavioral assay for hippocampal- and amygdala-dependent learning.
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Affiliation(s)
- Stephen Maren
- Department of Psychology and Neuroscience Program, University of Michigan, Ann Arbor, MI 48109-1043, USA.
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155
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Robbins TW, Ersche KD, Everitt BJ. Drug addiction and the memory systems of the brain. Ann N Y Acad Sci 2008; 1141:1-21. [PMID: 18991949 DOI: 10.1196/annals.1441.020] [Citation(s) in RCA: 290] [Impact Index Per Article: 18.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
We review drug addiction from the perspective of the hypothesis that drugs of abuse interact with distinct brain memory systems. We focus on emotional and procedural forms of memory, encompassing Pavlovian and instrumental conditioning, both for action-outcome and for stimulus-response associations. Neural structures encompassed by these systems include the amygdala, hippocampus, nucleus accumbens, and dorsal striatum. Additional influences emanate from the anterior cingulate and prefrontal cortex, which are implicated in the encoding and retrieval of drug-related memories that lead to drug craving and drug use. Finally, we consider the ancillary point that chronic abuse of many drugs may impact directly on neural memory systems via neuroadaptive and neurotoxic effects that lead to cognitive impairments in which memory dysfunction is prominent.
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Affiliation(s)
- T W Robbins
- Behavioural and Clinical Neuroscience Institute, University of Cambridge, Cambridge, UK.
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156
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Stephens DN, Duka T. Review. Cognitive and emotional consequences of binge drinking: role of amygdala and prefrontal cortex. Philos Trans R Soc Lond B Biol Sci 2008; 363:3169-79. [PMID: 18640918 DOI: 10.1098/rstb.2008.0097] [Citation(s) in RCA: 142] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Binge drinking is an increasingly recognized problem within the UK. We have studied the relationship of binge drinking to cognitive and emotional functioning in young adults, and have found evidence for increased impulsivity, impairments in spatial working memory and impaired emotional learning. Since in human studies it is difficult to understand whether such behavioural changes pre-date or are a consequence of binge drinking, we have also studied parallel behaviours in a rodent model, in which rats are exposed to intermittent episodes of alcohol consumption and withdrawal. In this model, and in parallel with our findings in human binge drinkers, and alcoholic patients who have undergone multiple episodes of detoxification, we have found evidence for impairments in aversive conditioning as well as increased impulsivity. These behavioural changes are accompanied by facilitated excitatory neurotransmission and reduced plasticity (long-term potentiation (LTP)) in amygdala and hippocampus. The impaired LTP is accompanied by both impaired associative learning and inappropriate generalization of previously learned associations to irrelevant stimuli. We propose that repeated episodes of withdrawal from alcohol induce aberrant neuronal plasticity that results in altered cognitive and emotional competences.
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Affiliation(s)
- David N Stephens
- Department of Psychology, University of Sussex, Falmer, Brighton, UK.
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157
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Zanoveli JM, Brandão ML. The dorsal periaqueductal and basolateral amygdala are necessary for the expression of conditioned place avoidance induced by semicarbazide stimulation of the dorsal periaqueductal region. Prog Neuropsychopharmacol Biol Psychiatry 2008; 32:1715-21. [PMID: 18687375 DOI: 10.1016/j.pnpbp.2008.07.008] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/31/2008] [Revised: 07/11/2008] [Accepted: 07/12/2008] [Indexed: 11/30/2022]
Abstract
The amygdala is critically involved in the regulation of unconditioned and conditioned reactions to threatening stimuli. It has been suggested that a neural circuit responsible for the production of defensive behavior elicited by the dorsal periaqueductal gray (dPAG) stimulation may project through ascending fibers to forebrain structures such as the basolateral complex of the amygdala (BLA). The present study evaluates the involvement of the dPAG and BLA in the mediation of unconditioned and conditioned responses organized in the dPAG using the open field and the conditioned place aversion (CPA) tests. In both tests, the intra-dPAG injections of semicarbazide (SEM), an inhibitor of the GABA synthesizing enzyme, was used as unconditioned stimulus (US). Using the open field test, we examine the effects of BLA inactivation with the GABA-(A) receptor agonist muscimol (MUS) on the unconditioned fear. We also investigated, through the CPA test, the effects of BLA and/or dPAG inactivation with MUS on the acquisition and the expression of the fear conditioned response. Our results showed that intra-BLA injections of MUS did not change the unconditioned fear elicited by dPAG injections of SEM. As for the CPA test, intra-BLA and intra-dPAG injections of MUS impaired the expression of CPA behavior induced by SEM injections into the dPAG. However, this inactivation of BLA did not impair the acquisition of the CPA behavior induced by injections of SEM into the dPAG. Altogether, these findings suggest that BLA does not participate in the mediation of unconditioned fear induced by dPAG chemical stimulation or in the acquisition of CPA in which aversive stimulation of the dPAG was used as US. In contrast, our results indicate that the activation of the dPAG and BLA is essential to the expression of the conditioned aversive response.
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Affiliation(s)
- Janaina M Zanoveli
- Instituto de Neurociências & Comportamento-INeC, Campus USP, Laboratório de Psicobiologia, Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto, Universidade de São Paulo (USP) 14049-901, Ribeirão Preto, SP, Brazil.
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158
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Ortiz JP, Close LN, Heinricher MM, Selden NR. Alpha(2)-noradrenergic antagonist administration into the central nucleus of the amygdala blocks stress-induced hypoalgesia in awake behaving rats. Neuroscience 2008; 157:223-8. [PMID: 18822354 DOI: 10.1016/j.neuroscience.2008.08.051] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2008] [Revised: 08/12/2008] [Accepted: 08/13/2008] [Indexed: 01/03/2023]
Abstract
Stress-induced hypoalgesia (SIH) is an adaptive behavioral phenomenon mediated in part by the amygdala. Acute stress increases amygdalar noradrenaline levels and focal application of alpha(2)-adrenoceptor agonists in the central nucleus of the amygdala (CeA) is antinociceptive. We hypothesized that alpha(2)-adrenoceptor antagonist administration into the CeA may block SIH. Bilateral microinjections of drug or saline via chronically implanted CeA cannulae were followed by either a period of restraint stress or rest. The nocifensive paw-withdrawal latency (PWL) to a focused beam of light was measured. PWLs were longer in restrained rats, constituting SIH. Microinjection of the alpha(2)-adrenoceptor antagonist idazoxan into the CeA prior to restraint blocked SIH. Idazoxan administration in unrestrained rats had no effect. Microinjection of the alpha(2)-adrenoceptor agonist clonidine in unrestrained rats caused dose dependent hypoalgesia, mimicking the effects of environmental stress. alpha(2)-Adrenoceptor function in the CeA is necessary for restraint-induced SIH.
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Affiliation(s)
- J P Ortiz
- Department of Neurological Surgery, Oregon Health & Science University, 3303 Southwest Bond Avenue, Portland, OR 97239, USA
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159
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Ruskin DN, LaHoste GJ. Reduced-volume cues effectively support fear conditioning despite sleep deprivation. Physiol Behav 2008; 96:64-6. [PMID: 18775445 DOI: 10.1016/j.physbeh.2008.08.014] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2007] [Revised: 07/23/2008] [Accepted: 08/15/2008] [Indexed: 11/19/2022]
Abstract
Sleep deprivation impairs contextual but not cued learned fear, and it has been suggested that this pattern reflects an insensitivity of the amygdala to sleep loss. The lack of effect of sleep deprivation on cued conditioning, however, might simply be due to the strong attention drawn by the typically loud cue tone. We reduced tone volume from our standard 80 dB to either 70 or 60 dB, to test if reduced cue volume allowed effects of sleep deprivation to be detected. Using the platform-over-water method, male C57BL/6 mice were sleep-deprived for 24 h; control mice were moved to novel cages for 24 h. Mice then underwent fear conditioning with a standard "delay" protocol, and were tested for contextual and cued learning the next day. A control group received no footshock during conditioning. In the cue test, and for both cue volumes, SD had no effect on freezing to the tone, which was very robust in conditioned mice regardless of sleep treatment. As expected, freezing to the tone in the no-shock groups was essentially absent. Also, freezing prior to the tone was low in all mice. At the lowest volume, the tone was only ~10 dB above background noise. 24 h sleep deprivation, however, blocked contextual fear in the same mice. These results support a pattern of sleep deprivation sparing amygdaloid function but impairing hippocampal function.
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Affiliation(s)
- David N Ruskin
- Department of Psychology, University of New Orleans, New Orleans, Louisiana, USA.
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160
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Ammassari-Teule M, Passino E, Restivo L, De Marsanich B. Fear conditioning in C57/BL/6 and DBA/2 mice: variability in nucleus accumbens function according to the strain predisposition to show contextual- or cue-based responding. Eur J Neurosci 2008. [DOI: 10.1111/j.1460-9568.2000.01333.x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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161
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Abstract
Emotion plays a critical role in many contemporary accounts of decision making, but exactly what underlies its influence and how this is mediated in the brain remain far from clear. Here, we review behavioral studies that suggest that Pavlovian processes can exert an important influence over choice and may account for many effects that have traditionally been attributed to emotion. We illustrate how recent experiments cast light on the underlying structure of Pavlovian control and argue that generally this influence makes good computational sense. Corresponding neuroscientific data from both animals and humans implicate a central role for the amygdala through interactions with other brain areas. This yields a neurobiological account of emotion in which it may operate, often covertly, to optimize rather than corrupt economic choice.
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Affiliation(s)
- Ben Seymour
- Wellcome Trust Centre for Imaging Neuroscience, University College London, 12 Queen Square, London WC1N3BG, UK.
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162
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Ito R, Robbins TW, Pennartz CM, Everitt BJ. Functional interaction between the hippocampus and nucleus accumbens shell is necessary for the acquisition of appetitive spatial context conditioning. J Neurosci 2008; 28:6950-9. [PMID: 18596169 PMCID: PMC3844800 DOI: 10.1523/jneurosci.1615-08.2008] [Citation(s) in RCA: 155] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2008] [Revised: 05/27/2008] [Accepted: 05/27/2008] [Indexed: 01/06/2023] Open
Abstract
The nucleus accumbens (NAc) has been implicated in a variety of associative processes that are dependent on the integrity of the amygdala and hippocampus (HPC). However, the extent to which the two subregions of the NAc, the core and shell, form differentiated circuits within the amygdala- and hippocampal-ventral striatal circuitry remains unclear. The present study investigated the effects of selective excitotoxic lesions of the nucleus accumbens shell or core subregion on appetitive elemental cue and context conditioning, shown previously to be dependent on the basolateral amygdala and hippocampus, respectively. Rats were trained sequentially to acquire discrete conditioned stimulus-sucrose conditioning, followed by spatial context-sucrose conditioning in a place preference apparatus characterized by three topographically identical chambers, the chambers being discriminable only on the basis of path integration. NAc shell lesions selectively impaired the acquisition of conditioned place preference and the use of spatial information to retrieve information about a discrete cue, whereas, as expected, NAc core lesions attenuated the acquisition of cue conditioning compared with sham rats. In a subsequent experiment, disconnection of the HPC from the NAc shell using unilateral asymmetric lesions of each structure resulted in a pattern of impairment in place conditioning and context-dependent cue retrieval similar to that produced by NAc shell lesions. These data not only suggest that the NAc core and shell subregions subserve distinct associative processes but also that the NAc shell and HPC are important functional components of a limbic corticostriatal network involved in spatial context conditioning.
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Affiliation(s)
- Rutsuko Ito
- Department of Experimental Psychology, University of Cambridge, Cambridge CB2 3EB, United Kingdom.
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163
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Treves A, Tashiro A, Witter MP, Moser EI. What is the mammalian dentate gyrus good for? Neuroscience 2008; 154:1155-72. [PMID: 18554812 DOI: 10.1016/j.neuroscience.2008.04.073] [Citation(s) in RCA: 197] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2008] [Revised: 04/12/2008] [Accepted: 04/28/2008] [Indexed: 01/01/2023]
Abstract
In the mammalian hippocampus, the dentate gyrus (DG) is characterized by sparse and powerful unidirectional projections to CA3 pyramidal cells, the so-called mossy fibers (MF). The MF form a distinct type of synapses, rich in zinc, that appear to duplicate, in terms of the information they convey, what CA3 cells already receive from entorhinal cortex layer II cells, which project both to the DG and to CA3. Computational models have hypothesized that the function of the MF is to enforce a new, well-separated pattern of activity onto CA3 cells, to represent a new memory, prevailing over the interference produced by the traces of older memories already stored on CA3 recurrent collateral connections. Although behavioral observations support the notion that the MF are crucial for decorrelating new memory representations from previous ones, a number of findings require that this view be reassessed and articulated more precisely in the spatial and temporal domains. First, neurophysiological recordings indicate that the very sparse dentate activity is concentrated on cells that display multiple but disorderly place fields, unlike both the single fields typical of CA3 and the multiple regular grid-aligned fields of medial entorhinal cortex. Second, neurogenesis is found to occur in the adult DG, leading to new cells that are functionally added to the existing circuitry, and may account for much of its ongoing activity. Third, a comparative analysis suggests that only mammals have evolved a DG, despite some of its features being present also in reptiles, whereas the avian hippocampus seems to have taken a different evolutionary path. Thus, we need to understand both how the mammalian dentate operates, in space and time, and whether evolution, in other vertebrate lineages, has offered alternative solutions to the same computational problems.
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Affiliation(s)
- A Treves
- Kavli Institute for Systems Neuroscience and Centre for the Biology of Memory, Norwegian University for Science and Technology, Trondheim, Norway.
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164
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Exposure to tetrabromobisphenol A (TBBPA) in Wistar rats: Neurobehavioral effects in offspring from a one-generation reproduction study. Toxicology 2008; 246:45-54. [DOI: 10.1016/j.tox.2008.01.007] [Citation(s) in RCA: 89] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2007] [Revised: 01/09/2008] [Accepted: 01/10/2008] [Indexed: 11/24/2022]
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165
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Ruskin DN, Lahoste GJ. Aspects of learned fear related to the hippocampus are sleep-dependent. Behav Brain Res 2008; 191:67-71. [PMID: 18423642 DOI: 10.1016/j.bbr.2008.03.011] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2007] [Revised: 02/22/2008] [Accepted: 03/10/2008] [Indexed: 12/26/2022]
Abstract
Reduced sleep interferes with contextual but not cued learned fear, and it was suggested that this selectivity reflects underlying neural substrates. The apparent lack of contextual fear in sleep-deprived animals, however, could be secondary to hyperactivity. Also, changing the parameters of cued conditioning can change the neural pathways involved, such that some types of cued fear might be sensitive to sleep loss. To address these issues, we measured fear expressed with conditioned defecation as well as behavior, and used a trace cued learning paradigm. Using the platform-over-water method, male Sprague-Dawley rats were continuously sleep-deprived for 3 days, or for 20 h/day for 3 days. Animals then underwent fear conditioning, and were tested for learning the next day. Sleep-deprived or -restricted animals showed a lack of contextual fear at testing, as conditioned freezing and defecation were minimal. Sleep deprivation also blocked cued fear after trace conditioning. Therefore, reduced sleep impairs contextual learning, and impairs cued learning only when the hippocampus is involved. The data support a model in which sleep loss interferes with hippocampal function while sparing amygdala function.
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Affiliation(s)
- David N Ruskin
- Applied Biopsychology Program, Department of Psychology, University of New Orleans, New Orleans, LA, USA.
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166
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Rana SA, Parker LA. Differential effects of neurotoxin-induced lesions of the basolateral amygdala and central nucleus of the amygdala on lithium-induced conditioned disgust reactions and conditioned taste avoidance. Behav Brain Res 2008; 189:284-97. [PMID: 18299156 DOI: 10.1016/j.bbr.2008.01.005] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2007] [Revised: 01/04/2008] [Accepted: 01/08/2008] [Indexed: 11/29/2022]
Abstract
When rats are intraorally exposed to saccharin solution that has previously been paired with lithium chloride (LiCl), they display Pavlovian conditioned disgust reactions. When exposed to LiCl-paired saccharin solution by bottle, they display suppressed instrumental approach to the bottle resulting in suppressed consumption. The present experiments demonstrated that while neither neurotoxin-induced lesions of the basolateral amygdala (BLA) nor the central nucleus of the amygdala (CeA) attenuated the display of Pavlovian conditioned disgust reactions, lesions of the BLA (but not the CeA) attenuated instrumental conditioned avoidance of the taste. The results are discussed in light of current models of the role of the amygdala in aversive learning.
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Affiliation(s)
- Shadna A Rana
- Department of Psychology, Wilfrid Laurier University, Waterloo, ON, Canada
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167
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D'Hanis W, Linke R, Yilmazer-Hanke DM. Topography of thalamic and parabrachial calcitonin gene-related peptide (CGRP) immunoreactive neurons projecting to subnuclei of the amygdala and extended amygdala. J Comp Neurol 2007; 505:268-91. [PMID: 17879271 DOI: 10.1002/cne.21495] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Injections of calcitonin gene-related peptide (CGRP) into the amygdala evoke fear-related behaviors and antinociceptive effects. In the present study we therefore characterized CGRP-containing amygdaloid afferents by injecting the retrograde tracer FluoroGold (FG) into subnuclei of the amygdala and adjacent divisions of the extended amygdala, namely, the lateral (LA) and central (CE) amygdaloid nuclei, interstitial nucleus of the posterior limb of the anterior commissure (IPAC), and the amygdalostriatal area (AStr). The distribution of retrogradely FG-labeled neurons and colocalization of CGRP-immunoreactivity with FG-labeling were mapped in the posterior paralaminar thalamic complex and parabrachial nuclei. The analysis of the posterior thalamus revealed that about 50% of CGRP-containing neurons projected to the AStr, the projections originating in the medial part of the medial geniculate body, posterior intralaminar nucleus, parvicellular subparafascicular nucleus, and peripeduncular nucleus. However, the percentage of CGRP-containing thalamic neurons projecting to the adjacent LA, medial part of the CE, and ventrocaudal part of the caudatoputamen rapidly dropped to 3-9%. There were no double-labeled cells after injections into the lateral and capsular parts of the CE and the IPAC. Thus, the AStr received the heaviest CGRP-containing projection from the posterior thalamus. CGRP-containing parabrachial neurons projected to the AStr and lateral, capsular, and medial parts of the CE, the projections originating in the external, crescent, and central parts of the lateral parabrachial nucleus and external part of the medial parabrachial nucleus. The results demonstrate a distinct projection pattern of CGRP-containing thalamic and parabrachial neurons to subnuclei of the amygdala and extended amygdala.
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Affiliation(s)
- W D'Hanis
- Institute of Anatomy, Medical Faculty, Otto-von-Guericke University, D-39120 Magdeburg, Germany
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168
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Lee AW, Brown RE. Comparison of medial preoptic, amygdala, and nucleus accumbens lesions on parental behavior in California mice (Peromyscus californicus). Physiol Behav 2007; 92:617-28. [PMID: 17610916 DOI: 10.1016/j.physbeh.2007.05.008] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2006] [Revised: 05/31/2006] [Accepted: 05/07/2007] [Indexed: 11/21/2022]
Abstract
We have previously shown that medial preoptic area (MPOA) lesions disrupt parental behavior in both male and female California mice (P. californicus). In the present study, we compare the effects of lesions in the MPOA, with those in the basolateral amygdala (BA) and nucleus accumbens (NA) on male and female parental behaviors in the biparental California mouse. A male or multiparous female from each male-female pair was given an electrolytic or sham lesion in the MPOA, BA, or NA and tested for parental responsiveness. Since female P. californicus show postpartum estrus, they were likely pregnant during parental testing. MPOA lesions produced deficits in both male and female parental behaviors, and BA lesions disrupted male, and to a lesser extent, female parental behavior. NA lesions produced mild effects on pup-retrieval in males and no effect on parental behavior in females. However, NA lesions incompletely destroyed the NA shell, the region most relevant for maternal behavior in rats, and should be investigated further. These results support a role for the MPOA and BA in both male and female parental behaviors.
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Affiliation(s)
- Anna W Lee
- Psychology Department, Dalhousie University, Halifax, NS, Canada B3H 4J1.
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169
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Gilbertson MW, Williston SK, Paulus LA, Lasko NB, Gurvits TV, Shenton ME, Pitman RK, Orr SP. Configural cue performance in identical twins discordant for posttraumatic stress disorder: theoretical implications for the role of hippocampal function. Biol Psychiatry 2007; 62:513-20. [PMID: 17509537 PMCID: PMC2768050 DOI: 10.1016/j.biopsych.2006.12.023] [Citation(s) in RCA: 79] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/14/2006] [Revised: 12/21/2006] [Accepted: 12/25/2006] [Indexed: 10/23/2022]
Abstract
BACKGROUND A significant subgroup of individuals with posttraumatic stress disorder (PTSD) exhibits chronic, unremitting symptomatology that has also been associated with smaller hippocampal volume. The hippocampus plays a significant role in configural processing of contextual cues that facilitates context-appropriate extinction of conditioned fear. We test the hypothesis that hippocampus-based configural processing deficits are a pre-existing vulnerability factor for unremitting forms of PTSD. METHODS Participants included male monozygotic twin pairs who were discordant for combat trauma. In 18 twin pairs the combat-exposed brother developed unremitting PTSD, whereas in 23 pairs the combat-exposed brother never developed PTSD. Participants were compared in the capacity to solve allocentric spatial processing tasks, and this performance was examined for its relationship to the severity of PTSD symptomatology and hippocampal volume. RESULTS Although not completely differentiated from overall IQ, PTSD combat veterans demonstrated significantly impaired performance in configural processing relative to non-PTSD combat veterans. Despite having neither combat-exposure nor PTSD, the unexposed co-twins of combat veterans with PTSD displayed the same decrements as their brothers. Deficits were significantly related to PTSD severity and hippocampal volume. CONCLUSIONS The current study provides the first evidence that the relevance of the hippocampus in PTSD might be related to pre-existing configural cue processing deficits that predispose individuals to develop unremitting forms of the disorder.
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170
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Turnock M, Becker S. A neural network model of hippocampal-striatal-prefrontal interactions in contextual conditioning. Brain Res 2007; 1202:87-98. [PMID: 17889839 DOI: 10.1016/j.brainres.2007.06.078] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2007] [Accepted: 06/20/2007] [Indexed: 11/26/2022]
Abstract
The hippocampus is thought to be critical for encoding contextually bound memories and setting the context for ongoing behavior. However, the mechanisms by which the hippocampal-cortical system controls behavior are poorly understood. We propose a computational model in which the hippocampus exerts contextual control over motivated behavior by gating prefrontal cortex inputs to the nucleus accumbens. The model integrates the episodic memory functions of the hippocampus, the prefrontal role in representing the motivational stimuli and cognitive control, and the role of striatal regions in conditioned learning within a single theoretical framework. Simulation results are consistent with the hypothesis that hippocampal-prefrontal interactions may act as the neural substrate that allows contextual cues to override conditioned responses at the level of the nucleus accumbens. Prefrontal and hippocampal input overrides the predominant CS-US association if the context is inconsistent, and promotes flexible selection of previously learned associations and behaviors. Simulated transection of the fornix, effectively eliminating hippocampal and prefrontal influence over the nucleus accumbens, abolishes normal contextual modulation of behavior. The model is consistent with a wide range of empirical data.
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Affiliation(s)
- Matthew Turnock
- Department of Psychology, Neuroscience and Behaviour, McMaster University, Building 34, Room 312, 1280 Main Street West, Hamilton, Canada ON L8S 4K1
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171
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Ortiz JP, Heinricher MM, Selden NR. Noradrenergic agonist administration into the central nucleus of the amygdala increases the tail-flick latency in lightly anesthetized rats. Neuroscience 2007; 148:737-43. [PMID: 17706366 PMCID: PMC2645807 DOI: 10.1016/j.neuroscience.2007.07.003] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2007] [Revised: 06/28/2007] [Accepted: 07/13/2007] [Indexed: 11/22/2022]
Abstract
The amygdala is a medial forebrain structure with an established role in nociceptive modulation, including the expression of stress-induced hypoalgesia (SIH). Projections from the locus coeruleus increase levels of noradrenaline in the amygdala during acute stress. alpha(2)-Noradrenergic receptor agonists have significant clinical utility as analgesic agents. We therefore hypothesized that alpha(2)-noradrenergic activation of the amygdala may result in behaviorally measurable hypoalgesia. Lightly anesthetized rats underwent microinjection of the alpha(2)-noradrenergic agonist clonidine into the amygdala and intermittent measurement of thermal nociception using the tail-flick latency (TFL). Bilateral microinjection of clonidine into the central nucleus of the amygdala (CeA) resulted in a significant, dose-dependent increase in TFL. This effect was blocked by systemic pre-treatment with the alpha(2)-antagonist yohimbine or by local pre-injection of the alpha(2)-antagonist idazoxan but not by local pre-injection of the alpha(1)-antagonist WB-4101. When injected alone, no antagonist resulted in a significant change in TFL compared with baseline. Clonidine injection into the amygdala but outside the CeA, including the basolateral nucleus of the amygdala, did not significantly alter TFL. These results demonstrate that anatomically and pharmacologically specific activation of alpha(2)-receptors in the CeA in lightly anesthetized rats results in behaviorally measurable antinociception.
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Affiliation(s)
- J P Ortiz
- Department of Neurological Surgery, Oregon Health & Science University, Mail code: CH8N, 3303 Southwest Bond Avenue, Portland, OR 97239, USA
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172
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Calandreau L, Jaffard R, Desmedt A. Dissociated roles for the lateral and medial septum in elemental and contextual fear conditioning. Learn Mem 2007; 14:422-9. [PMID: 17554087 PMCID: PMC1896092 DOI: 10.1101/lm.531407] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Extensive evidence indicates that the septum plays a predominant role in fear learning, yet the direction of this control is still a matter of debate. Increasing data suggest that the medial (MS) and lateral septum (LS) would be differentially required in fear conditioning depending on whether a discrete conditional stimulus (CS) predicts, or not, the occurrence of an aversive unconditional stimulus (US). Here, using a tone CS-US pairing (predictive discrete CS, context in background) or unpairing (context in foreground) conditioning procedure, we show, in mice, that pretraining inactivation of the LS totally disrupted tone fear conditioning, which, otherwise, was spared by inactivation of the MS. Inactivating the LS also reduced foreground contextual fear conditioning, while sparing the higher level of conditioned freezing to the foreground (CS-US unpairing) than to the background context (CS-US pairing). In contrast, inactivation of the MS totally abolished this training-dependent level of contextual freezing. Interestingly, inactivation of the MS enhanced background contextual conditioning under the pairing condition, whereas it reduced foreground contextual conditioning under the unpairing condition. Hence, the present findings reveal a functional dissociation between the LS and the MS in Pavlovian fear conditioning depending on the predictive value of the discrete CS. While the requirement of the LS is crucial for the appropriate processing of the tone CS-US association, the MS is crucial for an appropriate processing of contextual cues as foreground or background information.
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Affiliation(s)
- Ludovic Calandreau
- Centre de Neurosciences Intégratives et Cognitives CNRS 5228, Université de Bordeaux I, 33405 Talence, France
| | - Robert Jaffard
- Centre de Neurosciences Intégratives et Cognitives CNRS 5228, Université de Bordeaux I, 33405 Talence, France
| | - Aline Desmedt
- Centre de Neurosciences Intégratives et Cognitives CNRS 5228, Université de Bordeaux I, 33405 Talence, France
- Corresponding author.E-mail ; fax 33-5-40008743
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173
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Lopez-Fernandez MA, Montaron MF, Varea E, Rougon G, Venero C, Abrous DN, Sandi C. Upregulation of polysialylated neural cell adhesion molecule in the dorsal hippocampus after contextual fear conditioning is involved in long-term memory formation. J Neurosci 2007; 27:4552-61. [PMID: 17460068 PMCID: PMC6673006 DOI: 10.1523/jneurosci.0396-07.2007] [Citation(s) in RCA: 72] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2006] [Revised: 03/17/2007] [Accepted: 03/17/2007] [Indexed: 12/20/2022] Open
Abstract
The role of the hippocampus in pavlovian fear conditioning is controversial. Although lesion and pharmacological inactivation studies have suggested a key role for the dorsal hippocampus in contextual fear conditioning, the involvement of the ventral part is still uncertain. Likewise, the debate is open with regard to the putative implication of each hippocampal subdivision in fear conditioning to a discrete conditioned stimulus. We explored the potential existence of dissociations occurring in the dorsal versus ventral hippocampus at the cellular level while dealing with either contextual or cued fear conditioning and focused in a molecular "signature" linked to structural plasticity, the polysialylated form of the neural cell adhesion molecule (PSA-NCAM). We found an upregulation of PSA-NCAM expression in the dorsal (but not ventral) dentate gyrus at 24 h after contextual (but not tone) fear conditioning. Specific removal of PSA through microinfusion of the enzyme endoneuraminidase-N in the dorsal (but not ventral) hippocampus reduced freezing responses to the conditioned context. Therefore, we present evidence for a specific role of PSA-NCAM in the dorsal hippocampus in the plasticity processes occurring during consolidation of the context representation after "standard" contextual fear conditioning. Interestingly, we also found that exposing animals just to the context induced an activation of PSA-NCAM in both dorsal and ventral dentate gyrus. Altogether, these findings highlighting the distinctive occurrence of these neuroplastic processes in the dorsal hippocampus during the standard contextual fear-conditioning task enlighten the ongoing debate about the involvement of these hippocampal subdivisions in pavlovian fear conditioning.
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Affiliation(s)
| | - Marie-Françoise Montaron
- Neurogenesis and Pathophysiology Laboratory, Bordeaux Neuroscience Research Center, Institut National de la Santé et de la Recherche Médicale 862 and University of Bordeaux 2, Bordeaux Cedex 33077, France
| | - Emilio Varea
- Brain Mind Institute, Swiss Federal Institute of Technology, CH-1015 Lausanne, Switzerland
| | - Genevieve Rougon
- Centre National de la Recherche Scientifique Unité Mixte de Recherche 6216, Université de la Méditerranée, Institut de Biologie du Développement de Marseille-Luminy Case 907, Marseille Cedex 13288, France
| | - Cesar Venero
- Psychobiology Department, Universidad Nacional de Educacion a Distancia, 28040 Madrid, Spain, and
| | - Djoher Nora Abrous
- Neurogenesis and Pathophysiology Laboratory, Bordeaux Neuroscience Research Center, Institut National de la Santé et de la Recherche Médicale 862 and University of Bordeaux 2, Bordeaux Cedex 33077, France
| | - Carmen Sandi
- Brain Mind Institute, Swiss Federal Institute of Technology, CH-1015 Lausanne, Switzerland
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174
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Yamazaki Y, Jia Y, Wong JK, Sumikawa K. Chronic nicotine-induced switch in Src-family kinase signaling for long-term potentiation induction in hippocampal CA1 pyramidal cells. Eur J Neurosci 2007; 24:3271-84. [PMID: 17156388 DOI: 10.1111/j.1460-9568.2006.05213.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Here, we show that chronic nicotine exposure induces changes in Src signaling for the modulation of N-methyl-D-aspartate receptor (NMDAR) function and LTP induction in CA1 pyramidal cells. Activation of muscarinic receptors normally potentiates NMDAR responses in pyramidal cells via a Gq/protein kinase C (PKC)/proline-rich tyrosine kinase 2/Src signaling cascade. However, muscarinic, PKC and Src stimulation had no effect on NMDAR responses after chronic nicotine treatment. The lack of effect was apparently due to enhanced tyrosine phosphorylation, and therefore further stimulation of the signaling cascade caused no effect on NMDAR responses. Interestingly, another Src-family kinase potentiated NMDAR responses after, but not before, chronic nicotine treatment. In control pyramidal cells, Src inhibitor peptides prevented tetanus-induced long-term potentiation (LTP). Conversely, in chronic nicotine-exposed cells, the inhibitor was ineffective in blocking tetanus-induced LTP. Furthermore, in control pyramidal cells, applying exogenous Src and administration of an endogenous Src-family kinase activator increased alpha-amino-3-hydroxy-5-methylisoxazole-4-propionate receptor (AMPAR)-mediated responses. This increase was blocked by Src inhibitor peptides and occluded tetanus-induced LTP, as reported previously. In contrast, in chronic nicotine-treated pyramidal cells, applying exogenous Src had no effect on AMPAR-mediated responses and a tetanus-induced LTP. Interestingly, however, administration of an endogenous Src-family kinase activator enhanced AMPAR-mediated responses, which occluded tetanus-induced LTP. This enhancement was not prevented by co-application of Src inhibitor peptides. Thus, it appears that chronic nicotine exposure recruits another member of the Src-family for the regulation of NMDAR function and LTP induction. The nicotine-induced distinct signaling cascades may be involved in long-lasting memories of nicotine misuse.
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Affiliation(s)
- Yoshihiko Yamazaki
- Department of Neurobiology and Behavior, University of California, Irvine, CA 92697-4550, USA
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175
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Calandreau L, Trifilieff P, Mons N, Costes L, Marien M, Marighetto A, Micheau J, Jaffard R, Desmedt A. Extracellular hippocampal acetylcholine level controls amygdala function and promotes adaptive conditioned emotional response. J Neurosci 2007; 26:13556-66. [PMID: 17192439 PMCID: PMC6674713 DOI: 10.1523/jneurosci.3713-06.2006] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Ample data indicate that tone and contextual fear conditioning differentially require the amygdala and the hippocampus. However, mechanisms subserving the adaptive selection among environmental stimuli (discrete tone vs context) of those that best predict an aversive event are still elusive. Because the hippocampal cholinergic neurotransmission is thought to play a critical role in the coordination between different memory systems leading to the selection of appropriate behavioral strategies, we hypothesized that this cholinergic signal may control the competing acquisition of amygdala-mediated tone and contextual conditioning. Using pavlovian fear conditioning in mice, we first show a higher level of hippocampal acetylcholine release and a specific pattern of extracellular signal-regulated kinase 1/2 (ERK1/2) activation within the lateral (LA) and basolateral (BLA) amygdala under conditions in which the context is a better predictor than a discrete tone stimulus. Second, we demonstrate that levels of hippocampal cholinergic neurotransmission are causally related to the patterns of ERK1/2 activation in amygdala nuclei and actually determine the selection among the context or the simple tone the stimulus that best predicts the aversive event. Specifically, decreasing the hippocampal cholinergic signal not only impaired contextual conditioning but also mimicked conditioning to the discrete tone, both in terms of the behavioral outcome and the LA/BLA ERK1/2 activation pattern. Conversely, increasing this cholinergic signal not only disrupted tone conditioning but also promoted contextual fear conditioning. Hence, these findings highlight that hippocampal cholinergic neurotransmission controls amygdala function, thereby leading to the selection of relevant emotional information.
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Affiliation(s)
- Ludovic Calandreau
- Centre National de la Recherche Scientifique, Unité Mixte de Recherche 5106, Laboratoire de Neurosciences Cognitives, 33405 Talence, France
| | - Pierre Trifilieff
- Centre National de la Recherche Scientifique, Unité Mixte de Recherche 5106, Laboratoire de Neurosciences Cognitives, 33405 Talence, France
| | - Nicole Mons
- Centre National de la Recherche Scientifique, Unité Mixte de Recherche 5106, Laboratoire de Neurosciences Cognitives, 33405 Talence, France
| | - Laurence Costes
- Centre National de la Recherche Scientifique, Unité Mixte de Recherche 5106, Laboratoire de Neurosciences Cognitives, 33405 Talence, France
- Institut National de la Recherche Agronomique, Unité Mixte de Recherche 1244, Institut François Magendie, 33077 Bordeaux cedex, France, and
| | - Marc Marien
- Centre de Recherche Pierre Fabre, Division de Neurobiologie I, 81106 Castres, France
| | - Aline Marighetto
- Centre National de la Recherche Scientifique, Unité Mixte de Recherche 5106, Laboratoire de Neurosciences Cognitives, 33405 Talence, France
| | - Jacques Micheau
- Centre National de la Recherche Scientifique, Unité Mixte de Recherche 5106, Laboratoire de Neurosciences Cognitives, 33405 Talence, France
| | - Robert Jaffard
- Centre National de la Recherche Scientifique, Unité Mixte de Recherche 5106, Laboratoire de Neurosciences Cognitives, 33405 Talence, France
| | - Aline Desmedt
- Centre National de la Recherche Scientifique, Unité Mixte de Recherche 5106, Laboratoire de Neurosciences Cognitives, 33405 Talence, France
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176
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Yamazaki Y, Fujii S, Jia Y, Sumikawa K. Nicotine withdrawal suppresses nicotinic modulation of long-term potentiation induction in the hippocampal CA1 region. Eur J Neurosci 2007; 24:2903-16. [PMID: 17156213 DOI: 10.1111/j.1460-9568.2006.05160.x] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
We have previously reported that acute and chronic nicotine exposure lower the threshold for long-term potentiation (LTP) induction in the rat hippocampal CA1 region, and acute application of nicotine in the chronic-nicotine-treated hippocampus further reduces the threshold. However, it is unknown how withdrawal from chronic nicotine exposure affects the induction of LTP. Here, we show that, following nicotine withdrawal, the threshold for LTP induction fluctuates before returning to the basal level and acute nicotine is no longer effective in lowering the threshold at 4 days after withdrawal. Chronic nicotine-induced enhancement of N-methyl-d-aspartate receptor responses slowly diminishes and returns to the control level by 8 days of withdrawal. In 4-day-withdrawn hippocampi, there is functional up-regulation of postsynaptic alpha7 nicotinic acetylcholine receptors (nAChRs) on interneurons in the stratum radiatum, whereas the release of gamma-aminobutyric acid from their terminals is reduced. In both control and chronic nicotine-exposed hippocampi, acute nicotine depresses monosynaptic inhibitory postsynaptic currents recorded in pyramidal cells but has almost no effect at 4 days of withdrawal. The lack of effect is due, at least in part, to the loss of a presynaptic nicotine effect. These withdrawal-induced changes are accompanied by decreases in normal nicotine-induced enhancement of N-methyl-d-aspartate receptor responses, which may be responsible for the lack of acute nicotine-mediated facilitation of LTP induction in 4-day-withdrawn hippocampi. These withdrawal-induced changes may contribute to the cellular basis of unpleasant withdrawal symptoms and, thus, nicotine dependence.
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Affiliation(s)
- Yoshihiko Yamazaki
- Department of Neurobiology and Behavior, University of California, Irvine, CA 92697-4550, USA
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177
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El-Ghundi M, O'Dowd BF, George SR. Insights into the Role of Dopamine Receptor Systems in Learning and Memory. Rev Neurosci 2007; 18:37-66. [PMID: 17405450 DOI: 10.1515/revneuro.2007.18.1.37] [Citation(s) in RCA: 120] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
It is well established that learning and memory are complex processes involving and recruiting different brain modulatory neurotransmitter systems. Considerable evidence points to the involvement of dopamine in various aspects of cognition, and interest has been focused on investigating the clinical relevance of dopamine systems to age-related cognitive decline and manifestations of cognitive impairment in schizophrenia, Alzheimer's disease, Parkinson's disease and other neurodegenerative diseases. In the past decade or so, in spite of the molecular cloning of the five dopamine receptor subtypes, their specific roles in brain function remained inconclusive due to the lack of completely selective ligands that could distinguish between the members of the D1-like and D2-like dopamine receptor families. One of the most important advances in the field of dopamine research has been the generation of mutant mouse models permitting evaluation of the dopaminergic system using gene targeting technologies. These mouse models represent an important approach to explore the functional roles of closely related receptor subtypes. In this review, we present and discuss evidence on the role of dopamine receptors in different aspects of learning and memory at the cellular, molecular and behavioral levels. We compare evidence using conventional pharmacological, lesion or electrophysiological studies with results from mice with targeted deletions of different subtypes of dopamine receptor genes. We particularly focus on dopamine D1 and D2 receptors in an effort to delineate their specific roles in various aspects of cognitive function. We provide strong evidence, from our own recent work as well as others, that dopamine is part of the network that plays a very important role in cognitive function, and that although multiple dopamine receptor subtypes contribute to different aspects of learning and memory, the D1 receptor seems to play a more prominent role in mediating plasticity and specific aspects of cognitive function, including spatial learning and memory processes, reversal learning, extinction learning, and incentive learning.
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Affiliation(s)
- Mufida El-Ghundi
- Department of Pharmacology, University of Toronto, Ontario, Canada
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178
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Stouffer EM, White NM. Roles of learning and motivation in preference behavior: Mediation by entorhinal cortex, dorsal and ventral hippocampus. Hippocampus 2007; 17:147-60. [PMID: 17183529 DOI: 10.1002/hipo.20254] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
In the latent cue preference (LCP) task, water-deprived rats alternately drink a salt solution in one distinctive compartment of a conditioned cue preference (CCP) apparatus and water in the other compartment over 8 days (training trials). They are then given a choice between the two compartments with no solutions present (preference test). Previous findings showed that this training procedure results in two parallel forms of learning: conditioning to water-paired cues (a water-CCP) and latent learning of an association between salt and salt-paired compartment cues (a salt-LCP). Experiment 1 examined these two types of learning in isolation. Results showed that expression of the salt-LCP required salt deprivation during testing, but expression of the water-CCP did not require a deprivation state during testing. Other results showed that salt-LCP learning itself involves two distinct components: (1) the latent association among neutral cues in the salt-paired compartment, and (2) motivational information about salt deprivation during testing. Previous findings also demonstrated roles for the dorsal hippocampus (DH), ventral hippocampus (VH), and entorhinal cortex (EC) in salt-LCP learning. Experiment 2 examined the involvement of these structures during acquisition or expression of salt-LCP learning. Rats with cannulas aimed at DH, VH, or EC were given infusions of muscimol, either before exposure to the salt-paired, but not the water-paired, compartment during training or before the preference test. Inactivation of the DH or EC impaired both acquisition and expression of the association between salt and salt-paired compartment cues, while inactivation of the VH disrupted the influence of motivational information about salt deprivation required to express the salt-LCP. These results suggest unique roles for the EC-DH circuit and VH in salt-LCP learning, as well as a functional dissociation between the DH and VH.
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Affiliation(s)
- Eric M Stouffer
- Department of Psychology, McGill University, Montreal, Canada.
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179
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Cimadevilla JM, Mendez M, Mendez-Lopez M, Arias JL. Unilateral hippocampal blockade reveals that one hippocampus is sufficient for learning a passive avoidance task. J Neurosci Res 2007; 85:1138-42. [PMID: 17335088 DOI: 10.1002/jnr.21222] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Understanding hippocampal participation in memory processes is one of the goals in neuroscience research. By blocking the hippocampus unilaterally in Wistar rats, we assessed the contribution of this brain structure to memory in a passive avoidance task. Subjects were distributed into four groups. Group 1 received tetrodotoxin (TTX) in the right hippocampus during acquisition and retrieval phases. Group 2 had the same procedure as group 1, except that the contralateral hippocampus was blocked during retrieval. Subjects from group 3 acquired the task with saline (both hippocampi intact) and retrieved with the right hippocampus inactivated. Finally, group 4 received TTX unilaterally 2 min after acquisition to determine the hippocampal role in consolidation. Results showed that group 2 was impaired, compared with the other groups, during retrieval. These findings reveal that the hippocampal contribution to this task differs from that in other tasks considered to be hippocampus dependent.
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Affiliation(s)
- J M Cimadevilla
- Department of Neuroscience, University of Almeria, Almeria, Spain
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180
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Baarendse PJJ, van Grootheest G, Jansen RF, Pieneman AW, Ogren SO, Verhage M, Stiedl O. Differential involvement of the dorsal hippocampus in passive avoidance in C57bl/6J and DBA/2J mice. Hippocampus 2007; 18:11-9. [PMID: 17696168 DOI: 10.1002/hipo.20356] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The inferior performance of DBA/2 mice when compared to C57BL/6 mice in hippocampus-dependent behavioral tasks including contextual fear conditioning has been attributed to impaired hippocampal function. However, DBA/2J mice have been reported to perform similarly or even better than C57BL/6J mice in the passive avoidance (PA) task that most likely also depends on hippocampal function. The apparent discrepancy in PA versus fear conditioning performance in these two strains of mice was investigated using an automated PA system. The aim was to determine whether these two mouse strains utilize different strategies involving a different contribution of hippocampal mechanisms to encode PA. C57BL/6J mice exhibited significantly longer retention latencies than DBA/2J mice when tested 24 h after training irrespective of the circadian cycle. Dorsohippocampal NMDA receptor inhibition by local injection of the selective antagonist DL-2-amino-5-phosphonovaleric acid (AP5, 3.2 microg/mouse) before training resulted in impaired PA retention in C57BL/6J but not in DBA/2J mice. Furthermore, nonreinforced pre-exposure to the PA system before training caused a latent inhibition-like reduction of retention latencies in C57BL/6J, whereas it improved PA retention in DBA/2J mice. These pre-exposure experiments facilitated the discrimination of hippocampal involvement without local pharmacological intervention. The results indicate differences in PA learning between these two strains based on a different NMDA receptor involvement in the dorsal hippocampus in this emotional learning task. We hypothesize that mouse strains can differ in their PA learning performance based on their relative ability to form associations on the basis of unisensory versus multisensory contextual/spatial cues that involve hippocampal processing.
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Affiliation(s)
- Petra J J Baarendse
- Center for Neurogenomics and Cognitive Research and Institute for Neurosciences (INW), Vrije Universiteit Amsterdam, The Netherlands
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181
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Ito R, Robbins TW, McNaughton BL, Everitt BJ. Selective excitotoxic lesions of the hippocampus and basolateral amygdala have dissociable effects on appetitive cue and place conditioning based on path integration in a novel Y-maze procedure. Eur J Neurosci 2006; 23:3071-80. [PMID: 16819997 PMCID: PMC1852059 DOI: 10.1111/j.1460-9568.2006.04883.x] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
The hippocampus and amygdala are thought to be functionally distinct components of different learning and memory systems. This functional dissociation has been particularly apparent in pavlovian fear conditioning, where the integrity of the hippocampus is necessary for contextual conditioning, and of the amygdala for discrete cue conditioning. Their respective roles in appetitive conditioning, however, remain equivocal mainly due to the lack of agreement concerning the operational definition of a 'context'. The present study used a novel procedure to measure appetitive conditioning to spatial context or to a discrete cue. Following selective excitotoxic lesions of the hippocampus (HPC) or basolateral amygdala (BLA), rats were initially trained to acquire discrete CS-sucrose conditioning in a Y-maze apparatus with three topographically identical chambers, the chambers discriminated only on the basis of path integration. The same group of animals then underwent 'place/contextual conditioning' where the CS presented in a chamber assigned as the positive chamber was paired with sucrose, but the same CS presented in either of the other two chambers was not. Thus, spatial context was the only cue that the animal could use to retrieve the value of the CS. HPC lesions impaired the acquisition of conditioned place preference but facilitated the acquisition of cue conditioning, while BLA lesions had the opposite effect, retarding the acquisition of cue conditioning but leaving the acquisition of conditioned place preference intact. Here we provide strong support for the notion that the HPC and BLA subserve complementary and competing roles in appetitive cue and contextual conditioning.
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Affiliation(s)
- Rutsuko Ito
- Department of Experimental Psychology, University of Cambridge, Downing Street, Cambridge, CB2 3EB, UK.
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182
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Borlikova GG, Elbers NA, Stephens DN. Repeated withdrawal from ethanol spares contextual fear conditioning and spatial learning but impairs negative patterning and induces over-responding: evidence for effect on frontal cortical but not hippocampal function? Eur J Neurosci 2006; 24:205-16. [PMID: 16882017 DOI: 10.1111/j.1460-9568.2006.04901.x] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Repeated exposure of rats to withdrawal from chronic ethanol reduces hippocampal long-term potentiation and gives rise to epileptiform-like activity in hippocampus. We investigated whether such withdrawal experience also affects learning in tasks thought to be sensitive to hippocampal damage. Rats fed an ethanol-containing diet for 24 days with two intermediate 3-day withdrawal episodes, resulting in intakes of 13-14 g/kg ethanol per day, showed impaired negative patterning discrimination compared with controls and animals that had continuous 24-day ethanol treatment, but did not differ from these animals in the degree of contextual freezing 24 h after training or in spatial learning in the Barnes maze. Repeatedly withdrawn animals also showed increased numbers of responses in the period immediately before reinforcement became available in an operant task employing a fixed-interval schedule although overall temporal organization of responding was unimpaired. Thus, in our model of repeated withdrawal from ethanol, previously observed changes in hippocampal function did not manifest at the behavioural level in the tests employed. The deficit seen after repeated withdrawal in the negative patterning discrimination and over-responding in the fixed-interval paradigm might be related to the changes in the functioning of the cortex after withdrawal.
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Affiliation(s)
- Gilyana G Borlikova
- Department of Psychology, School of Life Sciences, University of Sussex, Falmer, Brighton, BN1 9QG, UK
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183
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Gosso MF, de Geus EJC, van Belzen MJ, Polderman TJC, Heutink P, Boomsma DI, Posthuma D. The SNAP-25 gene is associated with cognitive ability: evidence from a family-based study in two independent Dutch cohorts. Mol Psychiatry 2006; 11:878-86. [PMID: 16801949 DOI: 10.1038/sj.mp.4001868] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The synaptosomal-associated protein of 25 kDa (SNAP-25) gene plays an integral role in synaptic transmission, and is differentially expressed in the mammalian brain in the neocortex, hippocampus, anterior thalamic nuclei, substantia nigra and cerebellar granular cells. Recent studies have suggested a possible involvement of SNAP-25 in learning and memory, both of which are key components of human intelligence. In addition, the SNAP-25 gene lies in a linkage area implicated previously in human intelligence. In two independent family-based Dutch samples of 391 (mean age 12.4 years) and 276 (mean age 37.3 years) subjects, respectively, we genotyped 12 single-nucleotide polymorphisms (SNPs) in the SNAP-25 gene on 20p12-20p11.2. From all individuals, standardized intelligence measures were available. Using a family-based association test, a strong association was found between three SNPs in the SNAP-25 gene and intelligence, two of which showed association in both independent samples. The strongest, replicated association was found between SNP rs363050 and performance IQ (PIQ), where the A allele was associated with an increase of 2.84 PIQ points (P=0.0002). Variance in this SNP accounts for 3.4% of the phenotypic variance in PIQ.
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Affiliation(s)
- M F Gosso
- Department of Biological Psychology, Vrije Universiteit, Amsterdam, The Netherlands.
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184
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Cardinal RN. Neural systems implicated in delayed and probabilistic reinforcement. Neural Netw 2006; 19:1277-301. [PMID: 16938431 DOI: 10.1016/j.neunet.2006.03.004] [Citation(s) in RCA: 222] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2005] [Accepted: 03/30/2006] [Indexed: 11/23/2022]
Abstract
This review considers the theoretical problems facing agents that must learn and choose on the basis of reward or reinforcement that is uncertain or delayed, in implicit or procedural (stimulus-response) representational systems and in explicit or declarative (action-outcome-value) representational systems. Individual differences in sensitivity to delays and uncertainty may contribute to impulsivity and risk taking. Learning and choice with delayed and uncertain reinforcement are related but in some cases dissociable processes. The contributions to delay and uncertainty discounting of neuromodulators including serotonin, dopamine, and noradrenaline, and of specific neural structures including the nucleus accumbens core, nucleus accumbens shell, orbitofrontal cortex, basolateral amygdala, anterior cingulate cortex, medial prefrontal (prelimbic/infralimbic) cortex, insula, subthalamic nucleus, and hippocampus are examined.
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Affiliation(s)
- Rudolf N Cardinal
- Department of Experimental Psychology, University of Cambridge, Downing Street, Cambridge, UK.
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185
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Weisstaub NV, Zhou M, Lira A, Lambe E, González-Maeso J, Hornung JP, Sibille E, Underwood M, Itohara S, Dauer WT, Ansorge MS, Morelli E, Mann JJ, Toth M, Aghajanian G, Sealfon SC, Hen R, Gingrich JA. Cortical 5-HT2A receptor signaling modulates anxiety-like behaviors in mice. Science 2006; 313:536-40. [PMID: 16873667 DOI: 10.1126/science.1123432] [Citation(s) in RCA: 316] [Impact Index Per Article: 17.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Serotonin [5-hydroxytryptamine (5-HT)] neurotransmission in the central nervous system modulates depression and anxiety-related behaviors in humans and rodents, but the responsible downstream receptors remain poorly understood. We demonstrate that global disruption of 5-HT2A receptor (5HT2AR) signaling in mice reduces inhibition in conflict anxiety paradigms without affecting fear-conditioned and depression-related behaviors. Selective restoration of 5HT2AR signaling to the cortex normalized conflict anxiety behaviors. These findings indicate a specific role for cortical 5HT2AR function in the modulation of conflict anxiety, consistent with models of cortical, "top-down" influences on risk assessment.
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MESH Headings
- Animals
- Anxiety/physiopathology
- Cerebral Cortex/metabolism
- Conditioning, Psychological
- Conflict, Psychological
- Depression/physiopathology
- Exploratory Behavior
- Fear
- Limbic System/metabolism
- Mice
- Mice, Knockout
- Patch-Clamp Techniques
- Periaqueductal Gray/metabolism
- Prosencephalon/metabolism
- Receptor, Serotonin, 5-HT2A/genetics
- Receptor, Serotonin, 5-HT2A/metabolism
- Receptor, Serotonin, 5-HT2C/metabolism
- Receptors, Neurotransmitter/metabolism
- Risk-Taking
- Serotonin/physiology
- Signal Transduction
- Synaptic Transmission
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Affiliation(s)
- Noelia V Weisstaub
- Department of Biology, Columbia University and the New York State Psychiatric Institute, New York, NY 10032, USA
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186
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Meyers RA, Zavala AR, Speer CM, Neisewander JL. Dorsal hippocampus inhibition disrupts acquisition and expression, but not consolidation, of cocaine conditioned place preference. Behav Neurosci 2006; 120:401-12. [PMID: 16719704 DOI: 10.1037/0735-7044.120.2.401] [Citation(s) in RCA: 87] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Cocaine abusers may experience drug craving upon exposure to environmental contexts where cocaine was experienced. The dorsal hippocampus (DHC) is important for contextual conditioning, therefore the authors examined the specific role of the DHC in cocaine conditioned place preference (CPP). Muscimol was used to temporarily inhibit the DHC and was infused before conditioning sessions or tests for CPP to investigate acquisition and expression of cocaine CPP, respectively. To investigate consolidation, rats received intra-DHC muscimol either immediately or 6 hr after conditioning sessions. Inhibition of DHC, but not the overlying cortex, disrupted acquisition and expression of cocaine CPP. It is interesting to note that there was no effect of post-conditioning DHC inhibition. The findings suggest that the DHC is important for both acquisition and recall, but not consolidation, of context-cocaine associations.
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Affiliation(s)
- Ryan A Meyers
- Department of Psychology, Arizona State University, Tempe, AZ 85287-1104, USA
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187
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Mead AN, Morris HV, Dixon CI, Rulten SL, Mayne LV, Zamanillo D, Stephens DN. AMPA receptor GluR2, but not GluR1, subunit deletion impairs emotional response conditioning in mice. Behav Neurosci 2006; 120:241-8. [PMID: 16719688 DOI: 10.1037/0735-7044.120.2.241] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Deletions of gria1 or gria2 genes encoding alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic-acid-receptor subunits differ in their effects on appetitive conditioning. The authors investigated whether similar differences would occur in an aversive conditioning test. The ability of a discrete stimulus paired with footshock to subsequently inhibit food-maintained operant responding (conditioned emotional response) was examined in mice with deletions of gria1 or gria2 genes. Whereas gria1 knockout (KO) mice performed normally compared with wild-type (WT) controls, gria2 KO mice displayed no reduction in response rates when the shock-paired stimulus was presented. Nevertheless, gria2 KOs displayed evidence of freezing in a footshock-paired context, indicating that aversive learning could occur. In addition, gria1 KO mice showed some evidence of increased anxiety, and gria2 KOs showed reduced anxiety, in the elevated plus-maze.
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Affiliation(s)
- A N Mead
- Department of Psychology, University of Sussex, Brighton, United Kingdom
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188
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Yamazaki Y, Jia Y, Niu R, Sumikawa K. Nicotine exposurein vivoinduces long-lasting enhancement of NMDA receptor-mediated currents in the hippocampus. Eur J Neurosci 2006; 23:1819-28. [PMID: 16623839 DOI: 10.1111/j.1460-9568.2006.04714.x] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The use of nicotine via cigarette smoking forms long-lasting memories that are recalled in response to environmental cues associated with previous nicotine use. However, the changes in brain memory systems that underlie these long-lasting memories are not well understood. The N-methyl-D-aspartate receptor (NMDAR) is critical for long-lasting modifications of synapses. Here we show that in vivo nicotine exposure induces the enhancement of NR2B-containing NMDAR-mediated currents in the hippocampus, a brain region associated with the formation of memories. This nicotine effect is maintained during continued nicotine exposure and is accompanied by increased tyrosine phosphorylation of NR2B. Furthermore, long-term potentiation (LTP), which is considered to be a cellular substrate of learning and memory, induced in nicotine-exposed hippocampi contains a protein synthesis-independent long-lasting component. An NR2B-selective antagonist blocks a long-lasting component of LTP, but not LTP. These results suggest that exposure to nicotine provides conditions that promote the induction of long-lasting modifications of synapses, which may be involved in the formation of memories involving nicotine use.
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Affiliation(s)
- Yoshihiko Yamazaki
- Department of Neurobiology and Behavior, University of California Irvine, CA 92697-4550, USA
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189
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Balleine BW, Killcross S. Parallel incentive processing: an integrated view of amygdala function. Trends Neurosci 2006; 29:272-9. [PMID: 16545468 DOI: 10.1016/j.tins.2006.03.002] [Citation(s) in RCA: 406] [Impact Index Per Article: 22.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2005] [Revised: 01/30/2006] [Accepted: 03/02/2006] [Indexed: 11/21/2022]
Abstract
The amygdala is a heterogeneous structure that has been implicated in a wide variety of functions, most notably in fear conditioning. From this research, an influential serial model of amygdala processes has emerged in which aversive learning is mediated by the amygdala basolateral nucleus whereas performance, in this case of various defensive reflexes, is mediated by the central nucleus. By contrast, recent evidence from appetitive conditioning studies suggests that the basolateral and central nuclei operate in parallel to mediate distinct incentive processes: the basolateral nucleus encodes emotional events with reference to their particular sensory-specific features, whereas the central nucleus encodes their more general motivational or affective significance. Given that there is little if any direct behavioral evidence for the serial model, we suggest that more attention should be given to the claims of the parallel view.
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Affiliation(s)
- Bernard W Balleine
- Department of Psychology and the Brain Research Institute, University of California-Los Angeles, Box 951563, Los Angeles, CA 90095-1563, USA.
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190
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Zironi I, Burattini C, Aicardi G, Janak PH. Context is a trigger for relapse to alcohol. Behav Brain Res 2006; 167:150-5. [PMID: 16256214 DOI: 10.1016/j.bbr.2005.09.007] [Citation(s) in RCA: 108] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2004] [Revised: 08/31/2005] [Accepted: 09/03/2005] [Indexed: 10/25/2022]
Abstract
The environment in which alcohol consumption occurs may trigger later relapse in alcohol abusers. In this study, we tested whether an alcohol-associated environment would induce alcohol-seeking behavior. Male rats were trained to lever press for oral alcohol reinforcement in a distinctive context. Responding was then extinguished in a context with different olfactory, visual and tactile properties. Placement of the rats back into the original context in which they self-administered alcohol induced, in the absence of alcohol availability, a significant increase in lever press responding on the alcohol lever as compared to extinction levels of responding. The ability of the alcohol context to support alcohol-seeking behavior was maintained over 3 weeks, with no significant diminution. A second group of rats was trained to lever press for sucrose reinforcement; this group also demonstrated context-dependent reinstatement, although the degree of reinstatement decreased over repeated tests, returning to extinction values after 3 weeks. These findings indicate that contextual conditioning has a long-term impact on ethanol-seeking behavior after ethanol withdrawal. This animal model may be useful to study the neural mechanisms underlying relapse induced by ethanol-associated contexts in humans.
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Affiliation(s)
- Isabella Zironi
- Department of Human and General Physiology, University of Bologna, Via San Donato 19/2, 40127 Bologna, Italy.
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191
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Everitt BJ, Robbins TW. Neural systems of reinforcement for drug addiction: from actions to habits to compulsion. Nat Neurosci 2006; 8:1481-9. [PMID: 16251991 DOI: 10.1038/nn1579] [Citation(s) in RCA: 2543] [Impact Index Per Article: 141.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Drug addiction is increasingly viewed as the endpoint of a series of transitions from initial drug use--when a drug is voluntarily taken because it has reinforcing, often hedonic, effects--through loss of control over this behavior, such that it becomes habitual and ultimately compulsive. Here we discuss evidence that these transitions depend on interactions between pavlovian and instrumental learning processes. We hypothesize that the change from voluntary drug use to more habitual and compulsive drug use represents a transition at the neural level from prefrontal cortical to striatal control over drug seeking and drug taking behavior as well as a progression from ventral to more dorsal domains of the striatum, involving its dopaminergic innervation. These neural transitions may themselves depend on the neuroplasticity in both cortical and striatal structures that is induced by chronic self-administration of drugs.
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Affiliation(s)
- Barry J Everitt
- Department of Experimental Psychology and the MRC-Wellcome Behavioural and Clinical Neuroscience Institute, University of Cambridge, Downing Street, Cambridge CB2 3EB, UK.
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192
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193
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Abstract
Effects of hippocampal lesions on conditional discrimination were examined in rats. Rats were trained in a conditional drug discrimination paradigm using pentobarbital. They were able to learn the discrimination. After hippocampal lesions, all rats maintained discrimination. Thus a hippocampal lesion had no effect on retention of the conditional discrimination with drugs. Another group was trained in the same conditional discrimination except that the conditional stimuli were two different flashing lights. Similarly to the drug discrimination, only one of the two light conditioning stimuli was presented in one training session. No rat was able to learn the discrimination. New rats were trained in conventional conditional discrimination, in which the two conditional stimuli (flashing lights) were repeatedly presented within one training session. Hippocampal lesions made after learning this discrimination had no effect on retention. The present study reveals that the hippocampus does not have a crucial role in conditional discrimination learning when conditional stimuli were drugs and that rats could not learn conditional discrimination when two external conditional stimuli were presented in a similar way to the internal stimuli (drug discrimination paradigm).
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Affiliation(s)
- Yusuke Otsuka
- Department of Psychology, Keio University, Tokyo, Japan.
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194
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Abstract
The amygdala plays a crucial role in the orchestration and modulation of the organism response to aversive, stressful events. This response could be conceived as the result of two interdependent components. The first is represented by sets of visceral and motor responses aimed at helping the organism to cope with the present event. The second is the acquisition and modulation of memories relative to the stressful stimulus and its context. This latter component contributes to the instatement of conditioned stress responses that are essential to the capability of the organism to predict future exposures to similar stimuli in order to avoid them or counteract them effectively. In the amygdala, these two components become fully integrated. Massive networks link the amygdala to the hypothalamus, midbrain and brainstem. These networks convey visceral, humoral and nociceptive information to the amygdala and mediate its effects on the hypothalamic-pituitary-adrenal axis as well on autonomic and motor centers. On the other hand, interactions between the amygdala and interconnected cortical networks play a crucial role in acquisition, consolidation and extinction of learning relative to the stressful stimulus. Within the scope of this review, current evidence relative to the interaction between the amygdala and cortical networks will be considered in relationship to the integration of the conditioned response to stress.
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Affiliation(s)
- Sabina Berretta
- Harvard Medical School, Department of Psychiatry, 25 Shattuck Street, Boston, Massachusetts 02115, USA.
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195
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Ito R, Everitt BJ, Robbins TW. The hippocampus and appetitive Pavlovian conditioning: effects of excitotoxic hippocampal lesions on conditioned locomotor activity and autoshaping. Hippocampus 2005; 15:713-21. [PMID: 15906393 DOI: 10.1002/hipo.20094] [Citation(s) in RCA: 71] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The hippocampus (HPC) is known to be critically involved in the formation of associations between contextual/spatial stimuli and behaviorally significant events, playing a pivotal role in learning and memory. However, increasing evidence indicates that the HPC is also essential for more basic motivational processes. The amygdala, by contrast, is important for learning about the motivational significance of discrete cues. This study investigated the effects of excitotoxic lesions of the rat HPC and the basolateral amygdala (BLA) on the acquisition of a number of appetitive behaviors known to be dependent on the formation of Pavlovian associations between a reward (food) and discrete stimuli or contexts: (1) conditioned/anticipatory locomotor activity to food delivered in a specific context and (2) autoshaping, where rats learn to show conditioned discriminated approach to a discrete visual CS+. While BLA lesions had minimal effects on conditioned locomotor activity, hippocampal lesions facilitated the development of both conditioned activity to food and autoshaping behavior, suggesting that hippocampal lesions may have increased the incentive motivational properties of food and associated conditioned stimuli, consistent with the hypothesis that the HPC is involved in inhibitory processes in appetitive conditioning.
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Affiliation(s)
- Rutsuko Ito
- Department of Experimental Psychology, University of Cambridge, Downing Street, Cambridge, CB2 3EB UK.
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196
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Corcoran KA, Desmond TJ, Frey KA, Maren S. Hippocampal inactivation disrupts the acquisition and contextual encoding of fear extinction. J Neurosci 2005; 25:8978-87. [PMID: 16192388 PMCID: PMC6725608 DOI: 10.1523/jneurosci.2246-05.2005] [Citation(s) in RCA: 299] [Impact Index Per Article: 15.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2005] [Revised: 08/15/2005] [Accepted: 08/15/2005] [Indexed: 11/21/2022] Open
Abstract
In recent studies, inactivation of the dorsal hippocampus before the retrieval of extinguished fear memories disrupted the context-dependent expression of these memories. In the present experiments, we examined the role of the dorsal hippocampus in the acquisition of extinction. After pairing an auditory conditional stimulus (CS) with an aversive footshock [unconditional stimulus (US)], rats received an extinction session in which the CS was presented without the US. In experiment 1, infusion of muscimol, a GABAA receptor agonist, into the dorsal hippocampus before the extinction training session decreased the rate of extinction. Moreover, when later tested for fear to the extinguished CS, all rats that had received hippocampal inactivation before extinction training demonstrated renewed fear regardless of the context in which testing took place. This suggests a role for the dorsal hippocampus in both acquiring the extinction memory and encoding the CS-context relationship that yields the context dependence of extinction. In experiment 2, inactivation of the dorsal hippocampus before testing also disrupted the context dependence of fear to the extinguished CS. In experiment 3, quantitative autoradiography revealed the boundaries of muscimol diffusion after infusion into the dorsal hippocampus. Together, these results reveal that the dorsal hippocampus is involved in the acquisition, contextual encoding, and context-dependent retrieval of fear extinction. Learning and remembering when and where aversive events occur is essential for adaptive emotional regulation.
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Affiliation(s)
- Kevin A Corcoran
- Department of Psychology, University of Michigan, Ann Arbor, Michigan 48109-1043, USA
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197
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Thomson LM, Sutherland RJ. Systemic administration of lipopolysaccharide and interleukin-1β have different effects on memory consolidation. Brain Res Bull 2005; 67:24-9. [PMID: 16140159 DOI: 10.1016/j.brainresbull.2005.05.024] [Citation(s) in RCA: 75] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2005] [Revised: 05/11/2005] [Accepted: 05/14/2005] [Indexed: 11/28/2022]
Abstract
Sickness behaviour is an adaptive response to infection that includes lethargy, anorexia and of direct relevance to this work, learning and memory impairments. It has been suggested that proinflammatory cytokines may disrupt learning and memory by interfering with memory consolidation [C.R. Pugh, K. Kumagawa, M. Fleshner, L.R. Watkins, S.F. Maier, J.R. Rudy, Selective effects of peripheral lipopolysaccharide administration on contextual and auditory-cue fear conditioning, Brain Behav. Immun. 12 (1998) 212-229]. We tested whether systemic interleukin-1beta is sufficient to induce impairments in memory consolidation by comparing the effects of post-learning administration of interleukin-1beta with, the potent endotoxin, lipopolysaccharide; and saline, on retention of conditioned fear of a context. We administered an acute intraperitoneal injection of lipopolysaccharide, interleukin-1beta or saline immediately following a single conditioning episode in which rats received two tone-shock pairings. Two days following the learning episode, animals were tested for strength of conditioned responding to both the context and tone. Lipopolysaccharide-injected animals, but not interleukin-1beta-injected animals, exhibited less conditioned fear of context compared to saline-treated controls. All groups showed similar conditioned fear of tone. Our results suggest that systemic interleukin-1beta is not sufficient to disrupt memory consolidation, but rather, the synergistic actions of the proinflammatory cytokines released by lipopolysaccharide are required to disrupt memory consolidation.
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Affiliation(s)
- Lisa M Thomson
- Canadian Centre for Behavioural Neuroscience, University of Lethbridge, 4401 University Dr., Lethbridge, Alta., Canada T1K 3M4.
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198
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Calandreau L, Desmedt A, Decorte L, Jaffard R. A different recruitment of the lateral and basolateral amygdala promotes contextual or elemental conditioned association in Pavlovian fear conditioning. Learn Mem 2005; 12:383-8. [PMID: 16027178 PMCID: PMC1183256 DOI: 10.1101/lm.92305] [Citation(s) in RCA: 75] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Convergent data suggest dissociated roles for the lateral (LA) and basolateral (BLA) amygdaloid nuclei in fear conditioning, depending on whether a discrete conditioned stimulus (CS)-unconditional stimulus (US) or context-US association is considered. Here, we show that pretraining inactivation of the BLA selectively impaired conditioning to context. In contrast, inactivation of the LA disrupted conditioning to the discrete tone CS, but also either impaired or enhanced contextual conditioning, depending on whether the context was in the foreground or in the background. Hence, these findings refine the current model of the amygdala function in emotional learning by showing that the BLA and the LA not only differentially contribute to elemental and context-US association, but also promote, through their interaction, the most relevant of these two associations.
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Affiliation(s)
- Ludovic Calandreau
- Laboratoire de Neurosciences Cognitives, Centre National de la Recherche Scientifique UMR 5106, Université de Bordeaux I, 33405 Talence, France
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199
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Perez-Villalba A, Teruel-Martí V, Ruiz-Torner A, Olucha-Bordonau F. The effect of long context exposure on cued conditioning and c-fos expression in the rat forebrain. Behav Brain Res 2005; 161:263-75. [PMID: 15922053 DOI: 10.1016/j.bbr.2005.02.028] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2004] [Revised: 02/10/2005] [Accepted: 02/17/2005] [Indexed: 02/05/2023]
Abstract
The c-fos expression was used to study the neural substrates of the cued fear conditioning acquisition, preceded by a short exposure versus a long exposure to the conditioning context. A long-context exposure (either during the night or during the day) prior to conditioning, was associated with low freezing in the learning test. Differences in the c-fos expression of CA1, CA3, BL Amygdala, LS and BNST were found between the short- or long-context groups with a pre-exposure before cued conditioning. Ce Amygdala showed no differences in the c-fos expression labeling. We reported the hippocampal c-fos activation during the cued fear conditioning acquisition. Specifically, the CA1 activation could be related with the context-US processing during the CS-US association acquisition, which might prove that the CS-US associations cannot be made without an integrated context participating. The results showed that a long-context exposure prior to cued conditioning produces an inhibition of the CR (freezing), and this phenomenon is related with a specific c-fos expression in CA1, CA3, BL Amygdala, LS and BNST during the fear acquisition.
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Affiliation(s)
- Ana Perez-Villalba
- Department of Embryology and Human Anatomy, School of Medicine, Av Blasco Ibanez, 15, University of Valencia, 46010 Valencia, Spain.
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200
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Cheung THC, Cardinal RN. Hippocampal lesions facilitate instrumental learning with delayed reinforcement but induce impulsive choice in rats. BMC Neurosci 2005; 6:36. [PMID: 15892889 PMCID: PMC1156904 DOI: 10.1186/1471-2202-6-36] [Citation(s) in RCA: 98] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2005] [Accepted: 05/13/2005] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Animals must frequently act to influence the world even when the reinforcing outcomes of their actions are delayed. Learning with action-outcome delays is a complex problem, and little is known of the neural mechanisms that bridge such delays. When outcomes are delayed, they may be attributed to (or associated with) the action that caused them, or mistakenly attributed to other stimuli, such as the environmental context. Consequently, animals that are poor at forming context-outcome associations might learn action-outcome associations better with delayed reinforcement than normal animals. The hippocampus contributes to the representation of environmental context, being required for aspects of contextual conditioning. We therefore hypothesized that animals with hippocampal lesions would be better than normal animals at learning to act on the basis of delayed reinforcement. We tested the ability of hippocampal-lesioned rats to learn a free-operant instrumental response using delayed reinforcement, and what is potentially a related ability -- the ability to exhibit self-controlled choice, or to sacrifice an immediate, small reward in order to obtain a delayed but larger reward. RESULTS Rats with sham or excitotoxic hippocampal lesions acquired an instrumental response with different delays (0, 10, or 20 s) between the response and reinforcer delivery. These delays retarded learning in normal rats. Hippocampal-lesioned rats responded slightly less than sham-operated controls in the absence of delays, but they became better at learning (relative to shams) as the delays increased; delays impaired learning less in hippocampal-lesioned rats than in shams. In contrast, lesioned rats exhibited impulsive choice, preferring an immediate, small reward to a delayed, larger reward, even though they preferred the large reward when it was not delayed. CONCLUSION These results support the view that the hippocampus hinders action-outcome learning with delayed outcomes, perhaps because it promotes the formation of context-outcome associations instead. However, although lesioned rats were better at learning with delayed reinforcement, they were worse at choosing it, suggesting that self-controlled choice and learning with delayed reinforcement tax different psychological processes.
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Affiliation(s)
- Timothy HC Cheung
- Department of Experimental Psychology, University of Cambridge, Downing Street, Cambridge CB2 3EB, UK
- Psychopharmacology Section, Division of Psychiatry, B Floor, Medical School, Queen's Medical Centre, Nottingham NG7 2UH, UK
| | - Rudolf N Cardinal
- Department of Experimental Psychology, University of Cambridge, Downing Street, Cambridge CB2 3EB, UK
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