Faculty Scholarship
Showing 51 - 60 of 733 Items
All-loop group-theory constraints for color-ordered SU(N) gauge-theory amplitudes
Date: 2012-01-16
Creator: Stephen G. Naculich
Access: Open access
- We derive constraints on the color-ordered amplitudes of the L-loop four-point function in SU(N) gauge theories that arise solely from the structure of the gauge group. These constraints generalize well-known group theory relations, such as U(1) decoupling identities, to all loop orders. © 2011 Elsevier B.V.
Learning the futility of the thought suppression enterprise in normal experience and in obsessive compulsive disorder
Date: 2010-01-01
Creator: Sadia Najmi, Hannah Reese, Sabine Wilhelm, Jeanne Fama, Celeste, Beck, Daniel M. Wegner
Access: Open access
- Background: The belief that we can control our thoughts is not inevitably adaptive, particularly when it fuels mental control activities that have ironic unintended consequences. The conviction that the mind can and should be controlled can prompt people to suppress unwanted thoughts, and so can set the stage for the intrusive return of those very thoughts. An important question is whether or not these beliefs about the control of thoughts can be reduced experimentally. One possibility is that behavioral experiments aimed at revealing the ironic return of suppressed thoughts might create a lesson that could reduce unrealistic beliefs about the control of thoughts. Aims: The present research assessed the influence of the thought suppression demonstration on beliefs about the control of thoughts in a non-clinical sample, and among individuals with obsessive-compulsive disorder (OCD). Method: In Study 1, we assessed the effect of the thought suppression demonstration on beliefs about the control of thoughts among low and high obsessive individuals in the non-clinical population (N = 62). In Study 2, we conducted a similar study with individuals with OCD (N = 29). Results: Results suggest that high obsessive individuals in the non-clinical population are able to learn the futility of suppression through the thought suppression demonstration and to alter their faulty beliefs about the control of thoughts; however, for individuals with OCD, the demonstration may be insufficient for altering underlying beliefs. Conclusions: For individuals with OCD, the connection between suppressing a neutral thought in the suppression demonstration and suppressing a personally relevant obsession may need to be stated explicitly in order to affect their obsessive beliefs. © British Association for Behavioural and Cognitive Psychotherapies 2009.
Individual differences in EEG correlates of recognition memory due to DAT polymorphisms
Date: 2017-12-01
Creator: Paolo Medrano, Erika Nyhus, Andrew Smolen, Tim Curran, Robert S., Ross
Access: Open access
- Introduction: Although previous research suggests that genetic variation in dopaminergic genes may affect recognition memory, the role dopamine transporter expression may have on the behavioral and EEG correlates of recognition memory has not been well established. Objectives: The study aims to reveal how individual differences in dopaminergic functioning due to genetic variations in the dopamine transporter gene influences behavioral and EEG correlates of recognition memory. Methods: Fifty-eight participants performed an item recognition task. Participants were asked to retrieve 200 previously presented words while brain activity was recorded with EEG. Regions of interest were established in scalp locations associated with recognition memory. Mean ERP amplitudes and event-related spectral perturbations when correctly remembering old items (hits) and recognizing new items (correct rejections) were compared as a function of dopamine transporter group. Results: Participants in the dopamine transporter group that codes for increased dopamine transporter expression (10/10 homozygotes) display slower reaction times compared to participants in the dopamine transporter group associated with the expression of fewer dopamine transporters (9R-carriers). 10/10 homozygotes further displayed differences in ERP and oscillatory activity compared to 9R-carriers. 10/10 homozygotes fail to display the left parietal old/new effect, an ERP signature of recognition memory associated with the amount of information retrieved. 10/10 homozygotes also displayed greater decreases of alpha and beta oscillatory activity during item memory retrieval compared to 9R-carriers. Conclusion: Compared to 9R-carriers, 10/10 homozygotes display slower hit and correct rejection reaction times, an absence of the left parietal old/new effect, and greater decreases in alpha and beta oscillatory activity during recognition memory. These results suggest that dopamine transporter polymorphisms influence recognition memory.
Incorporating an ERP project into undergraduate instruction
Date: 2016-01-01
Creator: Erika Nyhus, Nancy Curtis
Access: Open access
- Electroencephalogram (EEG) is a relatively non-invasive, simple technique, and recent advances in open source analysis tools make it feasible to implement EEG as a component in undergraduate neuroscience curriculum. We have successfully led students to design novel experiments, record EEG data, and analyze event-related potentials (ERPs) during a one-semester laboratory course for undergraduates in cognitive neuroscience. First, students learned how to set up an EEG recording and completed an analysis tutorial. Students then learned how to set up a novel EEG experiment; briefly, they formed groups of four and designed an EEG experiment on a topic of their choice. Over the course of two weeks students collected behavioral and EEG data. Each group then analyzed their behavioral and ERP data and presented their results both as a presentation and as a final paper. Upon completion of the group project students reported a deeper understanding of cognitive neuroscience methods and a greater appreciation for the strengths and weaknesses of the EEG technique. Although recent advances in open source software made this project possible, it also required access to EEG recording equipment and proprietary software. Future efforts should be directed at making publicly available datasets to learn ERP analysis techniques and making publicly available EEG recording and analysis software to increase the accessibility of hands-on research experience in undergraduate cognitive neuroscience laboratory courses. Copyright
Correction of profiles of in-situ chlorophyll fluorometry for the contribution of fluorescence originating from non-algal matter
Date: 2017-01-01
Creator: Xiaogang Xing, Hervé Claustre, Emmanuel Boss, Collin Roesler, Emanuele, Organelli, Antoine Poteau, Marie Barbieux, Fabrizio D’Ortenzio
Access: Open access
- In situ chlorophyll fluorometers have been widely employed for more than half a century, and to date, it still remains the most used instrument to estimate chlorophyll-a concentration in the field, especially for measurements onboard autonomous observation platforms, e.g., Bio-Argo floats and gliders. However, in deep waters (> 300 m) of some specific regions, e.g., subtropical gyres and the Black Sea, the chlorophyll fluorescence profiles frequently reveal "deep sea red fluorescence" features. In line with previous studies and through the analysis of a large data set (cruise transect in the South East Pacific and data acquired by 82 Bio- Argo floats), we show that the fluorescence signal measured by a humic-like DOM fluorometer is highly correlated to the "deep sea red fluorescence." Both fluorescence signals are indeed linearly related in deep waters. To remove the contribution of non-algal organic matter from chlorophyll fluorescence profiles, we introduce a new correction. Rather that removing a constant value (generally the deepest chlorophyll a fluorescence value from the profile, i.e., so-called "deep-offset correction"), we propose a correction method which relies on DOM fluorometry and on its variation with depth. This new method is validated with chlorophyll concentration extracted from water samples and further applied on the Bio-Argo float data set. More generally, we discuss the potential of the proposed method to become a standard and routine procedure in quality-control and correction of chlorophyll a fluorescence originating from Bio-Argo network.
“Unmotivated bias” and partisan hostility: Empirical evidence
Date: 2019-04-01
Creator: Daniel F. Stone
Access: Open access
- Extreme partisan animosity has been on the rise in the US and is prevalent around the world. This hostility is typically attributed to social group identity, motivated reasoning, or a combination thereof. In this paper, I empirically examine a novel contributing factor: the “unmotivated” cognitive bias of overprecision (overconfidence in precision of beliefs). Overprecision could cause partisan hostility indirectly via inflated confidence in one's own ideology, partisan identity, or perceptions of social distance between the parties. Overprecision could also cause this hostility directly by causing excessively strong inferences from observed information that is either skewed against the out-party or simply misunderstood. Using a nationally representative sample, I find consistent support for direct effects of overprecision and mixed support for indirect effects. The point estimates imply a one standard deviation increase in a respondent's overprecision predicts as much as a 0.71 standard deviation decline in relative out-party favorability.
Rapid evolution of a coadapted gene complex: Evidence from the segregation Distorter (SD) system of meiotic drive in Drosophila melanogaster
Date: 1996-09-11
Creator: Michael F. Palopoli, Chung I. Wu
Access: Open access
- Segregation Distorter (SD) is a system of meiotic drive found in natural populations of Drosophila melanogaster. Males heterozygous for an SD second chromosome and a normal homologue (SD+) produce predominantly SD- bearing sperm. The coadapted gene complex responsible for this transmission advantage spans the second chromosome centromere, consisting of three major and several minor interacting loci. To investigate the evolutionary history of this system, we surveyed levels of polymorphism and divergence at six genes that together encompass this pericentromeric region and span seven map units. Interestingly, there was no discernible divergence between SD and SD1 chromosomes for any of these molecular markers. Furthermore, SD chromosomes harbored much less polymorphism than did SD+ chromosomes. The results suggest that the SD system evolved recently, swept to appreciable frequencies worldwide, and carried with it the entire second chromosome centromeric region (roughly 10% of the genome). Despite its well-documented genetic complexity, this coadapted systems appears to have evolved on a time scale that is much shorter than can be gauge using nucleotide substitution data. Finally, the large genomic region hitchhiking with SD indicates that a multilocus, epistatically selected could affect the levels of DNA polymorphism observed in regions of reduced recombination.
Neural correlates of behavior therapy for Tourette's disorder
Date: 2014-01-01
Creator: Thilo Deckersbach, Tina Chou, Jennifer C. Britton, Lindsay E. Carlson, Hannah E., Reese, Jedidiah Siev, Lawrence Scahill, John C. Piacentini, Douglas W. Woods, John T. Walkup, Alan L. Peterson, Darin D. Dougherty, Sabine Wilhelm
Access: Open access
- Tourette's disorder, also called Tourette syndrome (TS), is characterized by motor and vocal tics that can cause significant impairment in daily functioning. Tics are believed to be due to failed inhibition of both associative and motor cortico-striato-thalamo-cortical pathways. Comprehensive Behavioral Intervention for Tics (CBIT), which is an extension of Habit Reversal Therapy (HRT), teaches patients to become more aware of sensations that reliably precede tics (premonitory urges) and to initiate competing movements that inhibit the occurrence of tics. In this study, we used functional magnetic resonance imaging (fMRI) to investigate the neural changes associated with CBIT treatment in subjects with TS. Eight subjects with TS were matched with eight healthy controls in gender, education, age, and handedness. Subjects completed the Visuospatial Priming (VSP) task, a measure of response inhibition, during fMRI scanning before and after CBIT treatment (or waiting period for controls). For TS subjects, we found a significant decrease in striatal (putamen) activation from pre- to post-treatment. Change in VSP task-related activation from pre- to post-treatment in Brodmann's area 47 (the inferior frontal gyrus) was negatively correlated with changes in tic severity. CBIT may promote normalization of aberrant cortico-striato-thalamo-cortical associative and motor pathways in individuals with TS.
Level-rank duality of D-branes on the SU(N) group manifold
Date: 2006-04-17
Creator: Stephen G. Naculich, Howard J. Schnitzer
Access: Open access
- The consequences of level-rank duality for untwisted D-branes on an SU(N) group manifold are explored. Relations are found between the charges of D-branes (which are classified by twisted K-theory) belonging to su (N)K and su (K)N theories, in the case of odd N + K. An isomorphism between the charge algebras is also demonstrated in this case. © 2006 Elsevier B.V. All rights reserved.
Requirement for pectin methyl esterase and preference for fragmented over native pectins for wall-associated kinase-activated, EDS1/PAD4-dependent stress response in arabidopsis
Date: 2014-07-04
Creator: Bruce D. Kohorn, Susan L. Kohorn, Nicholas J. Saba, Victoriano Meco Martinez
Access: Open access
- Background: The wall-associated kinases (WAKs) serve as pectin receptors. Results: A pectin methyl esterase and two transcription factor mutants suppress a dominant WAK allele. Conclusion: De-esterification of pectin is required for WAK activation though EDS1 and PAD4. Significance: The results provide a mechanism for the state of pectins to activate two different pathways. © 2014 by The American Society for Biochemistry and Molecular Biology, Inc.