NeuroImage
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Despite an extensive literature on the neural substrates of response inhibition, when and where this process occurs in the brain remain unclear. The present study aimed to shed light on this issue by exploiting the high temporal resolution of the event-related potentials (ERPs) and recent advances in source localization. Temporo-spatial principal component analysis was employed to define more precisely the two ERP components most often associated with response inhibition (i.e., frontocentral N2 and frontocentral P3), as well as to improve the accuracy of source localization. ⋯ This increased activation was observed predominantly in the presupplementary motor area (preSMA). Present results suggest that the frontocentral P3 and the preSMA play a core role in response inhibition. The findings of this study substantiate and complement previous results obtained by hemodynamic procedures.
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Serotonin transporter-linked polymorphic region (5-HTTLPR) has been associated with modulation of resting-state amygdala level, which was considered to underlie a risk for mood and anxiety disorders. The findings however have been inconsistent which could be related to interactions of the genotype with other factors e.g. sex or personality characteristics. Therefore, the aim of the present study was to explore the modulation of the amygdala perfusion in the resting-state by sex and 5-HTTLPR/rs25531 genotype, controlled for personality dimensions assessed by Temperament and Character Inventory (Cloninger et al., 1994). ⋯ In females, there was a significant negative correlation between the rCBF and BOLD response in the right amygdala, and more so in S carriers. In males, there was no significant correlation between rCBF and BOLD response in the right amygdala. The novelty of our results lies in the demonstration of gene by sex interaction with resting blood flow in the amygdala that elucidates sex-related differences in emotional reactivity.
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In everyday life, expert advice has a great impact on individual decision making. Although often beneficial, advice may sometimes be misleading and cause people to pursue actions that entail suboptimal outcomes. This detrimental effect may diminish over time, when individuals have gathered sufficient contradicting evidence. ⋯ Our results demonstrate that the nature of the very first advice-related experience already determines how strongly misleading advice will influence learning and ensuing decision making-an effect that is mediated by the ventral pallidum. Thus, in contrast to conventional reinforcement learning, learning under the influence of advice is susceptible to primacy effects. The present findings advance our understanding of why false beliefs are particularly difficult to change once they have been reinforced.
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A specific positron emission tomography (PET) radiotracer for the glycine transporter type 1 (GlyT1) would constitute an imaging biomarker to investigate the distribution of GlyT1 in normal individuals and those with neuropsychiatric disorders. In addition it could demonstrate the ability of a novel drug to reach its target in the brain and enable receptor occupancy studies, thus facilitating drug development. In this article we describe the evaluation in non-human primates of two candidate PET radiotracers ([(11)C]RO5013852 and [(11)C]RO5013853) previously characterized in the rat. ⋯ Plasma concentrations of approximately 150-300 ng/mL were estimated to produce 50% GlyT1 occupancy in the thalamus, the cerebellum and the pons. [(11)C]RO5013853 is a promising radiotracer for in vivo imaging of the GlyT1. It can be easily radiolabeled, exhibits moderate metabolism, displays a good specific signal, and is suitable for receptor occupancy studies of therapeutic compounds that target the GlyT1. The successful characterization of [(11)C]RO5013853 in healthy volunteers is presented in this NeuroImage issue (Wong et al., 2013).
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Quantitative assessment of the myelin content in white matter (WM) using MRI has become a useful tool for investigating myelin-related diseases, such as multiple sclerosis (MS). Myelin water fraction (MWF) maps can be estimated pixel-by-pixel by a determination of the T₂ or T₂* spectrum from signal decay measurements at each individual image pixel. However, detection of parameters from the measured decay curve, assuming a combination of smooth multi-exponential curves, results in a nonlinear and seriously ill-posed problem. ⋯ To determine optimal weighting factors, we define a spatially independent neighborhood for each pixel and a distance with respect to decay rates that effectively includes pixels with similar decay characteristics, and which therefore have similar relaxation parameters. We recover the MWF values by using optimally weighted decay curves. We use numerical simulations and in vitro and in vivo experimental brain data scanned with a multi-gradient-echo sequence to demonstrate the feasibility of our proposed algorithm and to highlight its advantages compared to the conventional method.