scholarly journals Assessment of Motion Bias on the Detection of Dopamine Response to Challenge

2021 ◽  
Author(s):  
Michael A. Levine ◽  
Finnegan Calabro ◽  
David Izquierdo-Garcia ◽  
Daniel B. Chonde ◽  
Kevin T. Chen ◽  
...  
Keyword(s):  
Motion Correction ◽  
Relative Effect ◽  
Constant Infusion ◽  
Binding Potential ◽  
High Temporal Resolution ◽  
Behavioral Task ◽  
Bias Effect ◽  
Reference Tissue ◽  
Behavioral Challenges ◽  
The Impact

ABSTRACT11C-Raclopride (RAC) positron emission tomography (PET) is used to study dopamine response to pharmacological and behavioral challenges. Behavioral challenges produce smaller responses than pharmacological challenges and are more susceptible to sources of bias, including motion bias. The purpose of this study was to characterize the effect of motion bias within the context of a behavioral task challenge, examining the impact of different motion correction strategies, different task response magnitudes, and intra-versus interframe motion.MethodsSeventy healthy young adults were administered bolus plus constant infusion 11C-Raclopride (RAC) and imaged for 90 min on a 3-Tesla simultaneous PET/magnetic resonance (MR) scanner during which a functional MRI (fMRI) reward task experiment was conducted. Kinetic analysis was performed using an extension of the multilinear reference tissue model (MRTM), which encoded the task response as a unit step function at the start of the task (t = 40 min). The quantitative impacts of different approaches to motion correction (frame-based, reconstruction-based, none) were compared using voxel maps of change in binding potential (ΔBPND). Motion bias was compared to task effect by simulating different levels of ΔBPND (0%, 5%, 10%, 20%) in conjunction with simulating high and no motion. Intraframe motion was simulated using motion estimates derived from the simultaneously acquired MR data. The relative impact of intraframe motion was evaluated by comparing maps of bias in ΔBPND before and after applying frame-based motion correction.ResultsAmong the high-motion subjects, failure to perform motion correction resulted in large artifacts. Frame- and reconstruction-based approaches both corrected for motion effectively, with the former showing moderately more intense ΔBPND values (both positive and negative) in and around the striatum. At low task response magnitudes, simulations showed that motion bias can have a greater relative effect. At 5% ΔBPND, motion bias accounted for 60% of the total bias, while at 10% ΔBPND, it accounted for only 34%. Simulating high-temporal resolution motion, frame-based motion correction was shown to counteract the majority of the of the motion bias effect. The remaining bias attributable to intraframe motion accounted for only 8% of the total.ConclusionMotion bias can have a corrupting effect on RAC studies of behavioral task challenges, particularly as the magnitude of the response decreases. Applying motion correction mitigates most of the bias, and specifically correcting for interframe motion provides the bulk of the benefit.

scholarly journals Cerebellar heterogeneity and its impact on PET data quantification of 5-HT receptor radioligands

2017 ◽  
Vol 37 (9) ◽  
pp. 3243-3252 ◽  
Author(s):  
Melanie Ganz ◽  
Ling Feng ◽  
Hanne Demant Hansen ◽  
Vincent Beliveau ◽  
Claus Svarer ◽  
...  
Keyword(s):  
Regional Differences ◽  
Binding Potential ◽  
Reference Tissue ◽  
Tissue Modeling ◽  
Standardized Uptake Values ◽  
Positron Emission ◽  
Serotonin System ◽  
Signed Rank ◽  
The Impact ◽  
G Protein Coupled

In the quantification of positron emission tomography (PET) radiotracer binding, a commonly used method is reference tissue modeling (RTM). RTM necessitates a proper reference and a ubiquitous choice for G-protein coupled receptors is the cerebellum. We investigated regional differences in uptake within the grey matter of the cerebellar hemispheres (CH), the cerebellar white matter (CW), and the cerebellar vermis (CV) for five PET radioligands targeting the serotonin system. Furthermore, we evaluated the impact of choosing different reference regions when quantifying neocortical binding. The PET and MR images are part of the Cimbi database: 5-HT1AR ([11C]CUMI-101, n = 8), 5-HT1BR ([11C]AZ10419369, n = 36), 5-HT2AR ([11C]Cimbi-36, n = 29), 5-HT4R ([11C]SB207145, n = 59), and 5-HTT ([11C]DASB, n = 100). We employed SUIT and FreeSurfer to delineate CV, CW, and CH and quantified mean standardized uptake values (SUV) and nondisplaceable neocortical binding potential (BPND). Statistical difference was assessed with paired nonparametric two-sided Wilcoxon signed-rank tests and multiple comparison corrected via false discovery rate. We demonstrate significant radioligand specific regional differences in cerebellar uptake. These differences persist when using different cerebellar regions for RTM, but the influence on the neocortical BPND is small. Nevertheless, our data highlight the importance of validating each radioligand carefully for defining the optimal reference region.

The effect of emotions, eWOM quality and online review sequence on consumer intention to follow advice obtained from digital services

2020 ◽  
Vol 31 (3) ◽  
pp. 465-487 ◽  
Author(s):  
Carla Ruiz-Mafe ◽  
Enrique Bigné-Alcañiz ◽  
Rafael Currás-Pérez
Keyword(s):  
Structural Model ◽  
Online Reviews ◽  
Moderating Effect ◽  
Online Information ◽  
Bias Effect ◽  
Content Type ◽  
Digital Services ◽  
Information Cues ◽  
Cognitive Information ◽  
The Impact

PurposeThis paper analyses the interrelationships between emotions, the cognitive information cues of online reviews and intention to follow the advice obtained from digital platforms, paying special attention to the moderating effect of the sequencing of review valence.Design/methodology/approachThe data were collected from 830 Spanish Tripadvisor users. In a two-step approach, a measurement model was estimated and a structural model analysed to test the proposed hypotheses. SmartPLS 3.0 software was used. The moderating effect of sequencing of reviews is tested.FindingsThe data analysis showed a bias effect of review sequence on the impact of online information cues and emotions on intention to follow advice obtained from Tripadvisor. When the online reviews of a restaurant begin with positive commentaries, their perceived persuasiveness is a stronger driver of the pleasure and arousal elicited by online reviews than when they begin with negative reviews. On the other hand, the perceived helpfulness of online reviews only triggers arousal when the user reads negative, followed by positive, comments. The impact of pleasure on intention to follow the advice provided in an online travel community is higher with positive-negative than with negative-positive sequences.Originality/valueWhile researchers have demonstrated the benefits of customer reviews on company sales, a largely uninvestigated issue is the interplay between emotions and cognitive information cues in the processing of online reviews. This is one of the first studies to examine the moderating effect of conflicting reviews on the impact of emotions and cognitive information cues on consumer intention to follow the advice obtained from digital services.

scholarly journals Determinants of Individual Support for Independence: Evidence from Montenegro

2021 ◽  
pp. 1-20
Author(s):  
Pëllumb Kelmendi ◽  
Christian Pedraza
Keyword(s):  
Individual Preference ◽  
Minority Rights ◽  
Relative Effect ◽  
Factors Associated ◽  
Eu Integration ◽  
Eu Membership ◽  
Individual Support ◽  
Nationally Representative ◽  
Democratic Principles ◽  
The Impact

Abstract This article investigates the determinants of individual support for independence in Montenegro. We outline five theoretically distinct groups of factors covered by the literature and evaluate their impact on individual preference for independence. Using observational data obtained from a nationally representative survey conducted in Montenegro in 2003–2004, we find support for several hypotheses, showing that identity, income, and partisanship significantly impact individual opinion about independence. We also investigate and discuss the relative effect size of different factors associated with preference for independence. Additionally, we test variables with hitherto unexplored implications for opinions on independence, including the impact of support for EU membership, as well as support for democratic principles. Our logistic regression analyses reveal that attitudes towards EU integration and minority rights are strongly associated with support for independence. By systematically analyzing existing and new hypotheses with data from an understudied case, our findings contribute to the nascent literature on individual preferences for independence.

scholarly journals Quantification of Ligand PET Studies using a Reference Region with a Displaceable Fraction: Application to Occupancy Studies with [11C]-DASB as an Example

2011 ◽  
Vol 32 (1) ◽  
pp. 70-80 ◽  
Author(s):  
Federico E Turkheimer ◽  
Sudhakar Selvaraj ◽  
Rainer Hinz ◽  
Venkatesha Murthy ◽  
Zubin Bhagwagar ◽  
...  
Keyword(s):  
Specific Binding ◽  
Normal Subjects ◽  
Volume Of Distribution ◽  
Binding Potential ◽  
Accurate Estimation ◽  
Data Sets ◽  
Reference Region ◽  
Reference Tissue ◽  
Positron Emission ◽  
Definition Of

This paper aims to build novel methodology for the use of a reference region with specific binding for the quantification of brain studies with radioligands and positron emission tomography (PET). In particular: (1) we introduce a definition of binding potential BPD = DVR–1 where DVR is the volume of distribution relative to a reference tissue that contains ligand in specifically bound form, (2) we validate a numerical methodology, rank-shaping regularization of exponential spectral analysis (RS-ESA), for the calculation of BPD that can cope with a reference region with specific bound ligand, (3) we demonstrate the use of RS-ESA for the accurate estimation of drug occupancies with the use of correction factors to account for the specific binding in the reference. [11C]-DASB with cerebellum as a reference was chosen as an example to validate the methodology. Two data sets were used; four normal subjects scanned after infusion of citalopram or placebo and further six test—retest data sets. In the drug occupancy study, the use of RS-ESA with cerebellar input plus corrections produced estimates of occupancy very close the ones obtained with plasma input. Test-retest results demonstrated a tight linear relationship between BPD calculated either with plasma or with a reference input and high reproducibility.

scholarly journals Effects of soil rewetting and thawing on soil gas fluxes: a review of current literature and suggestions for future research

2011 ◽  
Vol 8 (5) ◽  
pp. 9847-9899 ◽  
Author(s):  
D.-G. Kim ◽  
R. Vargas ◽  
B. Bond-Lamberty ◽  
M. R. Turetsky
Keyword(s):  
Climate Models ◽  
Gas Production ◽  
Global Climate Models ◽  
Soil Gas ◽  
Future Research ◽  
High Temporal Resolution ◽  
Short Term ◽  
Frozen Soils ◽  
Gas Fluxes ◽  
The Impact

Abstract. The rewetting of dry soils and the thawing of frozen soils are short-term, transitional phenomena in terms of hydrology and the thermodynamics of soil systems. The impact of these short-term phenomena on larger scale ecosystem fluxes has only recently been fully appreciated, and a growing number of studies show that these events affect various biogeochemical processes including fluxes of soil gases such as carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), ammonia (NH3) and nitric oxide (NO). Global climate models predict that future climatic change is likely to alter the frequency and intensity of drying-rewetting events and thawing of frozen soils, highlighting the importance of understanding how rewetting and thawing will influence soil gas fluxes. Here we summarize findings in a new database based on 338 studies conducted from 1956 to 2010, and highlight open research questions. The database revealed conflicting results following rewetting and thawing in various terrestrial ecosystems, ranging from large increases in gas fluxes to non-significant changes. An analysis of published field studies (n = 142) showed that after rewetting or thawing, CO2, CH4, N2O, NO and NH3 fluxes increase from pre-event fluxes following a power function, with no significant differenced among gases. We discuss possible mechanisms and controls that regulate flux responses, and note that a high temporal resolution of flux measurements is critical to capture rapid changes in gas fluxes after these soil perturbations. Finally, we propose that future studies should investigate the interactions between biological (i.e. microbial community and gas production) and physical (i.e. flux, diffusion, dissolution) changes in soil gas fluxes, and explore synergistic experimental and modelling approaches.

scholarly journals Synthesis and preclinical evaluation of [11C]MTP38 as a novel PET ligand for phosphodiesterase 7 in the brain

2020 ◽  
Author(s):  
Naoyuki Obokata ◽  
Chie Seki ◽  
Takeshi Hirata ◽  
Jun Maeda ◽  
Hideki Ishii ◽  
...  
Keyword(s):  
Arterial Input Function ◽  
Inflammatory Diseases ◽  
Input Function ◽  
Binding Potential ◽  
Dependent Manner ◽  
Reference Tissue ◽  
Molar Activity ◽  
The Brain

AbstractPurposePhosphodiesterase (PDE) 7 is a potential therapeutic target for neurological and inflammatory diseases, although in-vivo visualization of PDE7 has not been successful. In this study, we aimed to develop [11C]MTP38 as a novel positron emission tomography (PET) ligand for PDE7.Methods[11C]MTP38 was radiosynthesized by 11C-cyanation of a bromo precursor with [11C]HCN. PET scans of rat and rhesus monkey brains and in-vitro autoradiography of brain sections derived from these species were conducted with [11C]MTP38. In monkeys, dynamic PET data were analyzed with an arterial input function to calculate the total distribution volume (VT). The non-displaceable binding potential (BPND) in the striatum was also determined by a reference tissue model with cerebellar reference. Finally, striatal occupancy of PDE7 by an inhibitor was calculated in monkeys according to changes in BPND.Results[11C]MTP38 was synthesized with radiochemical purity ≥ 99.4% and molar activity of 38.6 ± 12.6 GBq/μmol. Autoradiography revealed high radioactivity in the striatum and its reduction by non-radiolabeled ligands, in contrast with unaltered autoradiographic signals in other regions. In-vivo PET after radioligand injection to rats and monkeys demonstrated that radioactivity was rapidly distributed to the brain and intensely accumulated in the striatum relative to the cerebellum. Correspondingly, estimated VT values in the monkey striatum and cerebellum were 3.59 and 2.69 mL/cm3, respectively. The cerebellar VT value was unchanged by pretreatment with unlabeled MTP38. Striatal BPND was reduced in a dose-dependent manner after pretreatment with MTP-X, a PDE7 inhibitor. Relationships between PDE7 occupancy by MTP-X and plasma MTP-X concentration could be described by Hill’s sigmoidal function.ConclusionWe have provided the first successful preclinical demonstration of in-vivo PDE7 imaging with a specific PET radioligand. [11C]MTP38 is a feasible radioligand for evaluating PDE7 in the brain and is currently being applied to a first-in-human PET study.

scholarly journals The efficacy of different preprocessing steps in reducing motion-related confounds in diffusion MRI connectomics

2020 ◽  
Author(s):  
Stuart Oldham ◽  
Aurina Arnatkevic̆iūtė ◽  
Robert E. Smith ◽  
Jeggan Tiego ◽  
Mark A. Bellgrove ◽  
...  
Keyword(s):  
Diffusion Mri ◽  
Motion Correction ◽  
Healthy Adult ◽  
Structural Connectivity ◽  
Head Motion ◽  
List Type ◽  
Edge Weighting ◽  
Quantitative Metrics ◽  
The Impact ◽  
Connectivity Strength

AbstractHead motion is a major confounding factor in neuroimaging studies. While numerous studies have investigated how motion impacts estimates of functional connectivity, the effects of motion on structural connectivity measured using diffusion MRI have not received the same level of attention, despite the fact that, like functional MRI, diffusion MRI relies on elaborate preprocessing pipelines that require multiple choices at each step. Here, we report a comprehensive analysis of how these choices influence motion-related contamination of structural connectivity estimates. Using a healthy adult sample (N = 252), we evaluated 240 different preprocessing pipelines, devised using plausible combinations of different choices related to explicit head motion correction, tractography propagation algorithms, track seeding methods, track termination constraints, quantitative metrics derived for each connectome edge, and parcellations. We found that an approach to motion correction that includes outlier replacement and within-slice volume correction led to a dramatic reduction in cross-subject correlations between head motion and structural connectivity strength, and that motion contamination is more severe when quantifying connectivity strength using mean tract fractional anisotropy rather than streamline count. We also show that the choice of preprocessing strategy can significantly influence subsequent inferences about network organization, with the location of network hubs varying considerably depending on the specific preprocessing steps applied. Our findings indicate that the impact of motion on structural connectivity can be successfully mitigated using recent motion-correction algorithms that include outlier replacement and within-slice motion correction.HighlightsWe assess how motion affects structural connectivity in 240 preprocessing pipelinesMotion contamination of structural connectivity depends on preprocessing choicesAdvanced motion correction tools reduce motion confoundsFA edge weighting is more susceptible to motion effects than streamline count

Sign in / Sign up

Export Citation Format

Share Document