1,514 research outputs found

    The role of dopamine in the accumbens core in the expression of Pavlovian‐conditioned responses

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    The role of dopamine in reward is a topic of debate. For example, some have argued that phasic dopamine signaling provides a prediction‐error signal necessary for stimulus–reward learning, whereas others have hypothesized that dopamine is not necessary for learning per se , but for attributing incentive motivational value (‘incentive salience’) to reward cues. These psychological processes are difficult to tease apart, because they tend to change together. To disentangle them we took advantage of natural individual variation in the extent to which reward cues are attributed with incentive salience, and asked whether dopamine (specifically in the core of the nucleus accumbens) is necessary for the expression of two forms of Pavlovian‐conditioned approach behavior – one in which the cue acquires powerful motivational properties (sign‐tracking) and another closely related one in which it does not (goal‐tracking). After acquisition of these conditioned responses (CRs), intra‐accumbens injection of the dopamine receptor antagonist flupenthixol markedly impaired the expression of a sign‐tracking CR, but not a goal‐tracking CR. Furthermore, dopamine antagonism did not produce a gradual extinction‐like decline in behavior, but maximally impaired expression of a sign‐tracking CR on the very first trial, indicating the effect was not due to new learning (i.e. it occurred in the absence of new prediction‐error computations). The data support the view that dopamine in the accumbens core is not necessary for learning stimulus–reward associations, but for attributing incentive salience to reward cues, transforming predictive conditional stimuli into incentive stimuli with powerful motivational properties. Ongoing debate exists about dopamine’s exact role in reward‐related processes. We took advantage of natural individual variation in the degree to which reward cues are attributed with motivational value, and asked whether dopamine in the core of the nucleus accumbens is necessary for the performance of two forms of Pavlovian conditioned approach behavior ‐ one in which the cue acquires powerful motivational properties (sign‐tracking) and another related one in which it does not (goal‐tracking). We found that blocking dopamine transmission within the core impaired the expression of sign‐tracking responses, but not goal‐tracking responses.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/93510/1/j.1460-9568.2012.08217.x.pd

    eleanor: An open-source tool for extracting light curves from the TESS Full-Frame Images

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    During its two year prime mission the Transiting Exoplanet Survey Satellite (TESS) will perform a time-series photometric survey covering over 80% of the sky. This survey comprises observations of 26 24 x 96 degree sectors that are each monitored continuously for approximately 27 days. The main goal of TESS is to find transiting planets around 200,000 pre-selected stars for which fixed aperture photometry is recorded every two minutes. However, TESS is also recording and delivering Full-Frame Images (FFIs) of each detector at a 30 minute cadence. We have created an open-source tool, eleanor, to produce light curves for objects in the TESS FFIs. Here, we describe the methods used in eleanor to produce light curves that are optimized for planet searches. The tool performs background subtraction, aperture and PSF photometry, decorrelation of instrument systematics, and cotrending using principal component analysis. We recover known transiting exoplanets in the FFIs to validate the pipeline and perform a limited search for new planet candidates in Sector 1. Our tests indicate that eleanor produces light curves with significantly less scatter than other tools that have been used in the literature. Cadence-stacked images, and raw and detrended eleanor light curves for each analyzed star will be hosted on MAST, with planet candidates on ExoFOP-TESS as Community TESS Objects of Interest (CTOIs). This work confirms the promise that the TESS FFIs will enable the detection of thousands of new exoplanets and a broad range of time domain astrophysics.Comment: 21 pages, 13 figures, 2 tables, Accepted to PAS

    Fragile antiferromagnetism in the heavy-fermion compound YbBiPt

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    We report results from neutron scattering experiments on single crystals of YbBiPt that demonstrate antiferromagnetic order characterized by a propagation vector, τAFM\tau_{\rm{AFM}} = (121212\frac{1}{2} \frac{1}{2} \frac{1}{2}), and ordered moments that align along the [1 1 1] direction of the cubic unit cell. We describe the scattering in terms of a two-Gaussian peak fit, which consists of a narrower component that appears below TN 0.4T_{\rm{N}}~\approx 0.4 K and corresponds to a magnetic correlation length of ξn\xi_{\rm{n}} \approx 80 A˚\rm{\AA}, and a broad component that persists up to TT^*\approx 0.7 K and corresponds to antiferromagnetic correlations extending over ξb\xi_{\rm{b}} \approx 20 A˚\rm{\AA}. Our results illustrate the fragile magnetic order present in YbBiPt and provide a path forward for microscopic investigations of the ground states and fluctuations associated with the purported quantum critical point in this heavy-fermion compound.Comment: 5 pages, 3 figure

    Psychiatric Medications and Stigmatizing Attitudes in College Students

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    Research suggests that biological explanations of mental illness include the promotion of the effectiveness of medication, and that such explanations lead to greater attributions of responsibility and potentially greater stigmatizing emotional and behavioral reactions. This study examined whether college students\u27 attitudes toward a fellow student with mental illness are affected by whether the latter is described as having benefitted previously from medication. Results suggest that the promotion of psychiatric medications as helpful may increase stigmatizing attitudes by peers against fellow students with mental illness

    Subcellular peptide localization in single identified neurons by capillary microsampling mass spectrometry

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    Single cell mass spectrometry (MS) is uniquely positioned for the sequencing and identification of peptides in rare cells. Small peptides can take on different roles in subcellular compartments. Whereas some peptides serve as neurotransmitters in the cytoplasm, they can also function as transcription factors in the nucleus. Thus, there is a need to analyze the subcellular peptide compositions in identified single cells. Here, we apply capillary microsampling MS with ion mobility separation for the sequencing of peptides in single neurons of the mollusk Lymnaea stagnalis, and the analysis of peptide distributions between the cytoplasm and nucleus of identified single neurons that are known to express cardioactive Phe-Met-Arg-Phe amide-like (FMRFamide-like) neuropeptides. Nuclei and cytoplasm of Type 1 and Type 2 F group (Fgp) neurons were analyzed for neuropeptides cleaved from the protein precursors encoded by alternative splicing products of the FMRFamide gene. Relative abundances of nine neuropeptides were determined in the cytoplasm. The nuclei contained six of these peptides at different abundances. Enabled by its relative enrichment in Fgp neurons, a new 28-residue neuropeptide was sequenced by tandem MS

    Antiinflammatory Therapy with Canakinumab for Atherosclerotic Disease

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    Background: Experimental and clinical data suggest that reducing inflammation without affecting lipid levels may reduce the risk of cardiovascular disease. Yet, the inflammatory hypothesis of atherothrombosis has remained unproved. Methods: We conducted a randomized, double-blind trial of canakinumab, a therapeutic monoclonal antibody targeting interleukin-1β, involving 10,061 patients with previous myocardial infarction and a high-sensitivity C-reactive protein level of 2 mg or more per liter. The trial compared three doses of canakinumab (50 mg, 150 mg, and 300 mg, administered subcutaneously every 3 months) with placebo. The primary efficacy end point was nonfatal myocardial infarction, nonfatal stroke, or cardiovascular death. RESULTS: At 48 months, the median reduction from baseline in the high-sensitivity C-reactive protein level was 26 percentage points greater in the group that received the 50-mg dose of canakinumab, 37 percentage points greater in the 150-mg group, and 41 percentage points greater in the 300-mg group than in the placebo group. Canakinumab did not reduce lipid levels from baseline. At a median follow-up of 3.7 years, the incidence rate for the primary end point was 4.50 events per 100 person-years in the placebo group, 4.11 events per 100 person-years in the 50-mg group, 3.86 events per 100 person-years in the 150-mg group, and 3.90 events per 100 person-years in the 300-mg group. The hazard ratios as compared with placebo were as follows: in the 50-mg group, 0.93 (95% confidence interval [CI], 0.80 to 1.07; P = 0.30); in the 150-mg group, 0.85 (95% CI, 0.74 to 0.98; P = 0.021); and in the 300-mg group, 0.86 (95% CI, 0.75 to 0.99; P = 0.031). The 150-mg dose, but not the other doses, met the prespecified multiplicity-adjusted threshold for statistical significance for the primary end point and the secondary end point that additionally included hospitalization for unstable angina that led to urgent revascularization (hazard ratio vs. placebo, 0.83; 95% CI, 0.73 to 0.95; P = 0.005). Canakinumab was associated with a higher incidence of fatal infection than was placebo. There was no significant difference in all-cause mortality (hazard ratio for all canakinumab doses vs. placebo, 0.94; 95% CI, 0.83 to 1.06; P = 0.31). Conclusions: Antiinflammatory therapy targeting the interleukin-1β innate immunity pathway with canakinumab at a dose of 150 mg every 3 months led to a significantly lower rate of recurrent cardiovascular events than placebo, independent of lipid-level lowering. (Funded by Novartis; CANTOS ClinicalTrials.gov number, NCT01327846.
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