Helping You Find Full Text Journal Articles

Search Results:

Author: Robert Whelan (63)


Jan
2018

Event-related potentials (ERPs) show promise to be objective indicators of cognitive functioning. The aim of the study was to examine if ERPs recorded during an oddball task would predict cognitive functioning and information processing speed in Multiple Sclerosis (MS) patients and controls at the individual level. Seventy-eight participants (35 MS patients, 43 healthy age-matched controls) completed visual and auditory 2- and 3-stimulus oddball tasks with 128-channel EEG, and a neuropsychological battery, at baseline (month 0) and at Months 13 and 26.

View Full Text PDF Listings View primary source full text article PDFs.

Dec
2017

Moment-to-moment reaction time variability on tasks of attention, often quantified by intra-individual response variability (IRV), provides a good indication of the degree to which an individual is vulnerable to lapses in sustained attention. Increased IRV is a hallmark of several disorders of attention, including Attention-Deficit/Hyperactivity Disorder (ADHD). Here, task-based fMRI was used to provide the first examination of how average brain activation and functional connectivity patterns in adolescents are related to individual differences in sustained attention as measured by IRV.

View Full Text PDF Listings View primary source full text article PDFs.

Dec
2017

Nociceptin is a key regulator linking environmental stress and alcohol drinking. In a genome-wide methylation analysis, we recently identified an association of a methylated region in the OPRL1 gene with alcohol-use disorders.
Here, we investigate the biological basis of this observation by analysing psychosocial stressors, methylation of the OPRL1 gene, brain response during reward anticipation and alcohol drinking in 660 fourteen-year-old adolescents of the IMAGEN study.

View Full Text PDF Listings View primary source full text article PDFs.

Mar
2018

The aim of this study was to examine symptom profiles of people diagnosed with attention-deficit/hyperactivity disorder (ADHD) and/or anxiety (ANX) in order to determine the validity of widely used ADHD and ANX rating scales for differential diagnostic use and to develop modified measures that take symptom overlap into account.
A cross-sectional design was used to assess differences in rating scale scores between clinical (n = 52) and control (n = 74) samples as well as differences among subgroups of the clinical sample (22 ADHD; 16 ADHD + ANX; 14 ANX).
Participants completed an online questionnaire where they responded to the Conners Adult ADHD Rating Scale (CAARS; Conners, Erhardt, & Sparrow, ) and State Trait Anxiety Inventory scales (STAI; Spielberger, Gorsuch, Lushene, Vagg, & Jacobs, ).

View Full Text PDF Listings View primary source full text article PDFs.

Oct
2017

The nicotinic system plays an important role in cognitive control and is implicated in several neuropsychiatric conditions. However, the contributions of genetic variability in this system to individuals' cognitive control abilities are poorly understood and the brain processes that mediate such genetic contributions remain largely unidentified. In this first large-scale neuroimaging genetics study of the human nicotinic receptor system (two cohorts, males and females, fMRI total= 1586, behavioral total= 3650), we investigated a common polymorphism of the high-affinity nicotinic receptor α4β2 (rs1044396 on thegene) previously implicated in behavioral and nicotine-related studies (albeit with inconsistent major/minor allele impacts).

View Full Text PDF Listings View primary source full text article PDFs.

Dec
1969

The authors sought to explore how conduct, hyperactivity/inattention, and emotional symptoms are associated with neural reactivity to social-emotional stimuli, and the extent to which psychosocial stress modulates these relationships.
Participants were community adolescents recruited as part of the European IMAGEN study. Bilateral amygdala regions of interest were used to assess the relationship between the three symptom domains and functional MRI neural reactivity during passive viewing of dynamic angry and neutral facial expressions.

View Full Text PDF Listings View primary source full text article PDFs.

May
2017

In a recent genomewide association study of subcortical brain volumes, a common genetic variation at rs945270 was identified as having the strongest effect on putamen volume, a brain measurement linked to familial risk for attention-deficit/hyperactivity disorder (ADHD). To determine whether rs945270 might be a genetic determinant of ADHD, its effects on ADHD-related symptoms and neural mechanisms of ADHD, such as response inhibition and reward sensitivity, were explored.
A large population sample of 1,834 14-year-old adolescents was used to test the effects of rs945270 on ADHD symptoms assessed through the Strengths and Difficulties Questionnaire and region-of-interest analyses of putamen activation by functional magnetic resonance imaging using the stop signal and monetary incentive delay tasks, assessing response inhibition and reward sensitivity, respectively.

View Full Text PDF Listings View primary source full text article PDFs.

Apr
2017

To analyze the involvement of different brain regions in behavioral inhibition and impulsiveness, differences in activation were investigated in fMRI data from a response inhibition task, the stop-signal task, in 1709 participants. First, areas activated more in stop-success (SS) than stop-failure (SF) included the lateral orbitofrontal cortex (OFC) extending into the inferior frontal gyrus (ventrolateral prefrontal cortex, BA 47/12), and the dorsolateral prefrontal cortex (DLPFC). Second, the anterior cingulate and anterior insula (AI) were activated more on failure trials, specifically in SF versus SS.

View Full Text PDF Listings View primary source full text article PDFs.

Dec
1969

This study investigated the neural correlates of psychotic-like experiences in youths during tasks involving inhibitory control, reward anticipation, and emotion processing. A secondary aim was to test whether these neurofunctional correlates of risk were predictive of psychotic symptoms 2 years later.
Functional imaging responses to three paradigms-the stop-signal, monetary incentive delay, and faces tasks-were collected in youths at age 14, as part of the IMAGEN study.

View Full Text PDF Listings View primary source full text article PDFs.

Nov
2017

Neuroimaging studies of attention-deficit/hyperactivity disorder (ADHD) have most commonly reported volumetric abnormalities in the basal ganglia, cerebellum, and prefrontal cortices. Few studies have examined the relationship between ADHD symptomatology and brain structure in population-based samples. We investigated the relationship between dimensional measures of ADHD symptomatology, brain structure, and reaction time variability-an index of lapses in attention.

View Full Text PDF Listings View primary source full text article PDFs.

Jun
2017

This study investigated the prevalence of disordered eating cognitions and behaviours across mid-adolescence in a large European sample, and explored the extent to which prevalence ratings were affected by informant (parent/adolescent), or the sex or age of the adolescent. The Development and Well-Being Assessment was completed by parent-adolescent dyads at age 14 (n = 2225) and again at age 16 (n = 1607) to explore the prevalence of 7 eating disorder symptoms (binge eating, purging, fear of weight gain, distress over shape/weight, avoidance of fattening foods, food restriction, and exercise for weight loss). Informant agreement was assessed using kappa coefficients.

View Full Text PDF Listings View primary source full text article PDFs.

Dec
1969

Complex human cognition, such as decision-making under ambiguity, is reflected in dynamic spatio-temporal activity in the brain. Here, we combined event-related potentials with computational modelling of the time course of decision-making and outcome evaluation during the Iowa Gambling Task. Measures of choice probability generated using the Prospect Valence Learning Delta (PVL-Delta) model, in addition to objective trial outcomes (outcome magnitude and valence), were applied as regressors in a general linear model of the EEG signal.

View Full Text PDF Listings View primary source full text article PDFs.

Apr
2017

Dysfunction in brain regions underlying impulse control, reward processing and executive function have been associated previously with adolescent alcohol misuse. However, identifying pre-existing neurobiological risk factors, as distinct from changes arising from early alcohol-use, is difficult. Here, we outline how neuroimaging data can identify the neural predictors of adolescent alcohol-use initiation and misuse by using prospective longitudinal studies to follow initially alcohol-naive individuals over time and by neuroimaging adolescents with inherited risk factors for alcohol misuse.

View Full Text PDF Listings View primary source full text article PDFs.

Nov
2016

The traditional view that mental disorders are distinct, categorical disorders has been challenged by evidence that disorders are highly comorbid and exist on a continuum (e.g., Caspi et al.

View Full Text PDF Listings View primary source full text article PDFs.

Nov
2016

Despite calls for integration of neurobiological methods into research on youth resilience (high competence despite high adversity), we know little about structural brain correlates of resilient functioning. The aim of the current study was to test for brain regions uniquely associated with positive functioning in the context of adversity, using detailed phenotypic classification.
1,870 European adolescents (M = 14.

View Full Text PDF Listings View primary source full text article PDFs.

Oct
2017

Human subcortical brain asymmetries in 15,847 people worldwide reveal effects of age and sex.

Brain Imaging Behav 2017 Oct;11(5):1497-1514
Tulio Guadalupe, Samuel R Mathias, Theo G M vanErp, Christopher D Whelan, Marcel P Zwiers, Yoshinari Abe, Lucija Abramovic, Ingrid Agartz, Ole A Andreassen, Alejandro Arias-Vásquez, Benjamin S Aribisala, Nicola J Armstrong, Volker Arolt, Eric Artiges, Rosa Ayesa-Arriola, Vatche G Baboyan, Tobias Banaschewski, Gareth Barker, Mark E Bastin, Bernhard T Baune, John Blangero, Arun L W Bokde, Premika S W Boedhoe, Anushree Bose, Silvia Brem, Henry Brodaty, Uli Bromberg, Samantha Brooks, Christian Büchel, Jan Buitelaar, Vince D Calhoun, Dara M Cannon, Anna Cattrell, Yuqi Cheng, Patricia J Conrod, Annette Conzelmann, Aiden Corvin, Benedicto Crespo-Facorro, Fabrice Crivello, Udo Dannlowski, Greig I de Zubicaray, Sonja M C de Zwarte, Ian J Deary, Sylvane Desrivières, Nhat Trung Doan, Gary Donohoe, Erlend S Dørum, Stefan Ehrlich, Thomas Espeseth, Guillén Fernández, Herta Flor, Jean-Paul Fouche, Vincent Frouin, Masaki Fukunaga, Jürgen Gallinat, Hugh Garavan, Michael Gill, Andrea Gonzalez Suarez, Penny Gowland, Hans J Grabe, Dominik Grotegerd, Oliver Gruber, Saskia Hagenaars, Ryota Hashimoto, Tobias U Hauser, Andreas Heinz, Derrek P Hibar, Pieter J Hoekstra, Martine Hoogman, Fleur M Howells, Hao Hu, Hilleke E Hulshoff Pol, Chaim Huyser, Bernd Ittermann, Neda Jahanshad, Erik G Jönsson, Sarah Jurk, Rene S Kahn, Sinead Kelly, Bernd Kraemer, Harald Kugel, Jun Soo Kwon, Herve Lemaitre, Klaus-Peter Lesch, Christine Lochner, Michelle Luciano, Andre F Marquand, Nicholas G Martin, Ignacio Martínez-Zalacaín, Jean-Luc Martinot, David Mataix-Cols, Karen Mather, Colm McDonald, Katie L McMahon, Sarah E Medland, José M Menchón, Derek W Morris, Omar Mothersill, Susana Munoz Maniega, Benson Mwangi, Takashi Nakamae, Tomohiro Nakao, Janardhanan C Narayanaswaamy, Frauke Nees, Jan E Nordvik, A Marten H Onnink, Nils Opel, Roel Ophoff, Marie-Laure Paillère Martinot, Dimitri Papadopoulos Orfanos, Paul Pauli, Tomáš Paus, Luise Poustka, Janardhan Yc Reddy, Miguel E Renteria, Roberto Roiz-Santiáñez, Annerine Roos, Natalie A Royle, Perminder Sachdev, Pascual Sánchez-Juan, Lianne Schmaal, Gunter Schumann, Elena Shumskaya, Michael N Smolka, Jair C Soares, Carles Soriano-Mas, Dan J Stein, Lachlan T Strike, Roberto Toro, Jessica A Turner, Nathalie Tzourio-Mazoyer, Anne Uhlmann, Maria Valdés Hernández, Odile A van den Heuvel, Dennis van der Meer, Neeltje E M van Haren, Dick J Veltman, Ganesan Venkatasubramanian, Nora C Vetter, Daniella Vuletic, Susanne Walitza, Henrik Walter, Esther Walton, Zhen Wang, Joanna Wardlaw, Wei Wen, Lars T Westlye, Robert Whelan, Katharina Wittfeld, Thomas Wolfers, Margaret J Wright, Jian Xu, Xiufeng Xu, Je-Yeon Yun, JingJing Zhao, Barbara Franke, Paul M Thompson, David C Glahn, Bernard Mazoyer, Simon E Fisher, Clyde Francks
The two hemispheres of the human brain differ functionally and structurally. Despite over a century of research, the extent to which brain asymmetry is influenced by sex, handedness, age, and genetic factors is still controversial. Here we present the largest ever analysis of subcortical brain asymmetries, in a harmonized multi-site study using meta-analysis methods.

View Full Text PDF Listings View primary source full text article PDFs.

Aug
2016

Psychotic disorders are characterized by attenuated activity in the brain's valuation system in key reward processing areas, such as the ventral striatum (VS), as measured with functional magnetic resonance imaging.
To examine whether common risk variants for psychosis are associated with individual variation in the VS.
A cross-sectional study of a large cohort of adolescents from the IMAGEN study (a European multicenter study of reinforcement sensitivity in adolescents) was performed from March 1, 2008, through December 31, 2011.

View Full Text PDF Listings View primary source full text article PDFs.

Aug
2016

Substance misusers, including adolescent smokers, often have reduced reward system activity during processing of non-drug rewards. Using a psychophysiological interaction approach, we examined functional connectivity with the ventral striatum during reward anticipation in a large (N = 206) sample of adolescent smokers. Increased smoking frequency was associated with (1) increased connectivity with regions involved in saliency and valuation, including the orbitofrontal cortex and (2) reduced connectivity between the ventral striatum and regions associated with inhibition and risk aversion, including the right inferior frontal gyrus.

View Full Text PDF Listings View primary source full text article PDFs.

Aug
2017

Individual differences in impulsivity and early adversity are known to be strong predictors of adolescent antisocial behavior. However, the neurobiological bases of impulsivity and their relation to antisocial behavior and adversity are poorly understood.
Impulsivity was estimated with a temporal discounting task.

View Full Text PDF Listings View primary source full text article PDFs.

Mar
2016

Prominent theories suggest that compulsive behaviors, characteristic of obsessive-compulsive disorder and addiction, are driven by shared deficits in goal-directed control, which confers vulnerability for developing rigid habits. However, recent studies have shown that deficient goal-directed control accompanies several disorders, including those without an obvious compulsive element. Reasoning that this lack of clinical specificity might reflect broader issues with psychiatric diagnostic categories, we investigated whether a dimensional approach would better delineate the clinical manifestations of goal-directed deficits.

View Full Text PDF Listings View primary source full text article PDFs.

Dec
1969

The incomplete-hippocampal-inversion (IHI), also known as malrotation, is an atypical anatomical pattern of the hippocampus, which has been reported in healthy subjects in different studies. However, extensive characterization of IHI in a large sample has not yet been performed. Furthermore, it is unclear whether IHI are restricted to the medial-temporal lobe or are associated with more extensive anatomical changes.

View Full Text PDF Listings View primary source full text article PDFs.

Dec
1969

Conduction along the optic nerve is often slowed in multiple sclerosis (MS). This is typically assessed by measuring the latency of the P100 component of the Visual Evoked Potential (VEP) using electroencephalography. The Visual Evoked Spread Spectrum Analysis (VESPA) method, which involves modulating the contrast of a continuous visual stimulus over time, can produce a visually evoked response analogous to the P100 but with a higher signal-to-noise ratio and potentially higher sensitivity to individual differences in comparison to the VEP.

View Full Text PDF Listings View primary source full text article PDFs.

Dec
1969

An important characteristic of childhood attention-deficit/hyperactivity disorder (ADHD) is a bias towards small immediate versus larger delayed rewards, but it is not known if this symptom is also a feature of adult ADHD. A delay-discounting task was administered to participants with adult ADHD and a comparison group in conjunction with functional magnetic resonance imaging. Participants responded to a series of questions that required judgments between small sums of money available immediately and larger sums obtained after a temporal delay.

View Full Text PDF Listings View primary source full text article PDFs.

Dec
2015

Cannabis use in adolescence may be characterized by differences in the neural basis of affective processing. In this study, we used an fMRI affective face processing task to compare a large group (n=70) of 14-year olds with a history of cannabis use to a group (n=70) of never-using controls matched on numerous characteristics including IQ, SES, alcohol and cigarette use. The task contained short movies displaying angry and neutral faces.

View Full Text PDF Listings View primary source full text article PDFs.

Oct
2015

Cannabis use during adolescence is known to increase the risk for schizophrenia in men. Sex differences in the dynamics of brain maturation during adolescence may be of particular importance with regard to vulnerability of the male brain to cannabis exposure.
To evaluate whether the association between cannabis use and cortical maturation in adolescents is moderated by a polygenic risk score for schizophrenia.

View Full Text PDF Listings View primary source full text article PDFs.

Feb
2016

The subject matter of neuroscience research is complex, and synthesising the wealth of data from this research to better understand mental processes is challenging. A useful strategy, therefore, may be to distinguish explicitly between the causal effects of the environment on behaviour (i.e.

View Full Text PDF Listings View primary source full text article PDFs.

Jun
2015

Suboptimal decision-making is a feature in the initiation and maintenance of substance use, often manifested in choosing for short-term benefits rather than long-term gain, and the failure to display cognitive flexibility, respectively. Studies of nicotine users typically focus on characterizing those who are already addicted; less is known about decision-making in former smokers.
Non- (n=21), former daily- (n=23) and current daily smokers (n=24), completed the contingency-shifting variant Iowa Gambling Task (csIGT), in which the reward and punishment contingencies of the decks are systematically varied after 100 trials of the 'standard' IGT.

View Full Text PDF Listings View primary source full text article PDFs.

Dec
2014

Longitudinal and family-based research suggests that conduct disorder, substance misuse, and ADHD involve both unique forms of dysfunction as well as more specific dysfunctions unique to each condition. Using direct measures of brain function, this study also found evidence in both unique and disorder-specific perturbations.

View Full Text PDF Listings View primary source full text article PDFs.

Aug
2014

A comprehensive account of the causes of alcohol misuse must accommodate individual differences in biology, psychology and environment, and must disentangle cause and effect. Animal models can demonstrate the effects of neurotoxic substances; however, they provide limited insight into the psycho-social and higher cognitive factors involved in the initiation of substance use and progression to misuse. One can search for pre-existing risk factors by testing for endophenotypic biomarkers in non-using relatives; however, these relatives may have personality or neural resilience factors that protect them from developing dependence.

View Full Text PDF Listings View primary source full text article PDFs.

Oct
2014

Catecholamine-0-methyl-transferase (COMT) gene variation effects on prefrontal blood oxygenation-level-dependent (BOLD) activation are robust; however, despite observations that COMT is estrogenically catabolized, sex differences in its prefrontal repercussions remain unclear. Here, in a large sample of healthy adolescents stratified by sex and Val(158)Met genotype (n=1133), we examine BOLD responses during performance of the stop-signal task in right-hemispheric prefrontal regions fundamental to inhibitory control. A significant sex-by-genotype interaction was observed in pre-SMA during successful-inhibition trials and in both pre-SMA and inferior frontal cortex during failed-inhibition trials with Val homozygotes displaying elevated activation compared with other genotypes in males but not in females.

View Full Text PDF Listings View primary source full text article PDFs.

Aug
2014

Noninvasive investigation of human sensory processing with high temporal resolution typically involves repeatedly presenting discrete stimuli and extracting an average event-related response from scalp recorded neuroelectric or neuromagnetic signals. While this approach is and has been extremely useful, it suffers from two drawbacks: a lack of naturalness in terms of the stimulus and a lack of precision in terms of the cortical response generators. Here we show that a linear modeling approach that exploits functional specialization in sensory systems can be used to rapidly obtain spatiotemporally precise responses to complex sensory stimuli using electroencephalography (EEG).

View Full Text PDF Listings View primary source full text article PDFs.

May
2014

The pathogenesis of adult-onset primary dystonia remains poorly understood. There is variable age-related and gender-related expression of the phenotype, the commonest of which is cervical dystonia. Endophenotypes may provide insight into underlying genetic and pathophysiological mechanisms of dystonia.

View Full Text PDF Listings View primary source full text article PDFs.

Jan
2014

The Relational Completion Procedure is effective for establishing same, opposite and comparative derived relations in verbally able adults, but to date it has not been used to establish relational frames in young children or those with developmental delay. In Experiment 1, the Relational Completion Procedure was used with the goal of establishing two 3-member sameness networks in nine individuals with Autism Spectrum Disorder (eight with language delay). A multiple exemplar intervention was employed to facilitate derived relational responding when required.

View Full Text PDF Listings View primary source full text article PDFs.

Dec
1969

A compulsivity spectrum has been hypothesized to exist across Obsessive-Compulsive disorder (OCD), Eating Disorders (ED), substance abuse (SA) and binge-drinking (BD). The objective was to examine the validity of this compulsivity spectrum, and differentiate it from an externalizing behaviors dimension, but also to look at hypothesized personality and neural correlates.
A community-sample of adolescents (N=1938; mean age 14.

View Full Text PDF Listings View primary source full text article PDFs.

Nov
2013

The pathogenesis and the genetic basis of adult-onset primary torsion dystonia remain poorly understood. Because of markedly reduced penetrance in this disorder, a number of endophenotypes have been proposed; many of these may be epiphenomena secondary to disease manifestation. Mediational endophenotypes represent gene expression; the study of trait (endophenotypic) rather than state (phenotypic) characteristics avoids the misattribution of secondary adaptive cerebral changes to pathogenesis.

View Full Text PDF Listings View primary source full text article PDFs.

Sep
2013

Research using explicit measures has linked decreased positive future thinking, but not increased negative future thinking, with clinical depression. However, individuals may be unable or unwilling to express thoughts about the future, and can be unaware of implicit beliefs that can influence their behavior. Implicit measures of cognition may shed light on the role of future thinking in depression.

View Full Text PDF Listings View primary source full text article PDFs.

May
2014

The ability to predict outcomes from neuroimaging data has the potential to answer important clinical questions such as which depressed patients will respond to treatment, which abstinent drug users will relapse, or which patients will convert to dementia. However, many prediction analyses require methods and techniques, not typically required in neuroimaging, to accurately assess a model's predictive ability. Regression models will tend to fit to the idiosyncratic characteristics of a particular sample and consequently will perform worse on unseen data.

View Full Text PDF Listings View primary source full text article PDFs.

Feb
2014

Overgeneralization of fear and threat-avoidance represents a formidable barrier to successful clinical treatment of anxiety disorders. While stimulus generalization along quantifiable physical dimensions has been studied extensively, less consideration has been given to symbolic generalization, in which stimuli are indirectly and arbitrarily related. The present study examined whether the magnitude and extent of symbolic generalization of threat-avoidance and threat-beliefs differed between spider-phobic and nonphobic individuals.

View Full Text PDF Listings View primary source full text article PDFs.

Sep
2013

The validity of self-rated anxiety inventories in people with multiple sclerosis (pwMS) is unclear. However, the appropriateness of self-reported depression scales has been widely examined. Given somatic symptom overlap between depression and MS, research emphasises caution when using such scales.

View Full Text PDF Listings View primary source full text article PDFs.

Jan
2013


View Full Text PDF Listings View primary source full text article PDFs.

Dec
1969

Cognitive impairment (CI), often examined with neuropsychological tests such as the Paced Auditory Serial Addition Test (PASAT), affects approximately 65% of multiple sclerosis (MS) patients. The P3b event-related potential (ERP), evoked when an infrequent target stimulus is presented, indexes cognitive function and is typically compared across subjects' scalp electroencephalography (EEG) data. However, the clustering of independent components (ICs) is superior to scalp-based EEG methods because it can accommodate the spatiotemporal overlap inherent in scalp EEG data.

View Full Text PDF Listings View primary source full text article PDFs.

Jun
2012

The impulsive behavior that is often characteristic of adolescence may reflect underlying neurodevelopmental processes. Moreover, impulsivity is a multi-dimensional construct, and it is plausible that distinct brain networks contribute to its different cognitive, clinical and behavioral aspects. As these networks have not yet been described, we identified distinct cortical and subcortical networks underlying successful inhibitions and inhibition failures in a large sample (n = 1,896) of 14-year-old adolescents.

View Full Text PDF Listings View primary source full text article PDFs.

May
2012

In this paper we investigate the use of classical fMRI Random Effect (RFX) group statistics when analyzing a very large cohort and the possible improvement brought from anatomical information. Using 1326 subjects from the IMAGEN study, we first give a global picture of the evolution of the group effect t-value from a simple face-watching contrast with increasing cohort size. We obtain a wide activated pattern, far from being limited to the reasonably expected brain areas, illustrating the difference between statistical significance and practical significance.

View Full Text PDF Listings View primary source full text article PDFs.

Dec
1969

The technical challenges of recording electroencephalographic (EEG) data during motion are considerable, but would enable the possibility of investigating neural function associated with balance, motor function and motion perception. The challenges include finding a reliable method of motion stimulus reproduction, removing artifacts, and ensuring that the recordings retain sufficient EEG signal for proper interpretation. This study details the use of the P3 waveform to validate the concept of motion-based EEG data, and discusses some potential future uses in experimental and clinical settings.

View Full Text PDF Listings View primary source full text article PDFs.

Sep
2011

Adult-onset primary torsion dystonia is an autosomal dominant disorder with markedly reduced penetrance; patients with sporadic adult-onset primary torsion dystonia are much more prevalent than familial. The temporal discrimination threshold is the shortest time interval at which two stimuli are detected to be asynchronous and has been shown to be abnormal in adult-onset primary torsion dystonia. The aim was to determine the frequency of abnormal temporal discrimination thresholds in patients with sporadic adult-onset primary torsion dystonia and their first-degree relatives.

View Full Text PDF Listings View primary source full text article PDFs.

Oct
2011

Symbolic generalization of avoidance may underlie the aetiology and maintenance of anxiety disorders. The aim of the present study was to demonstrate inferred threat-avoidance and safety (non-avoidance) behaviours that occur in the presence of stimuli indirectly related to learned threat and safety cues. A laboratory experiment was conducted involving two symbolic stimulus equivalence relations consisting of three physically dissimilar stimuli (avoidance cues: AV1-AV2-AV3 and neutral cues: N1-N2-N3).

View Full Text PDF Listings View primary source full text article PDFs.

Jul
2011

Plants show patterns of spatial genetic differentiation reflecting gene flow mediated by pollen and seed dispersal and genotype × environment interactions. If patterns of genetic structure are determined largely by gene flow then they may be useful in predicting the likelihood of inbreeding or outbreeding depression but should be less useful if there is strong site-specific selection. For many Australian plants little is known about either their population genetics or the effects on mating systems of variation in pollen transfer distances.

View Full Text PDF Listings View primary source full text article PDFs.

Jun
2011

The frequency of hybridization in plants is context dependent and can be influenced by the local mating environment. We used progeny arrays and admixture and pollen dispersal analyses to assess the relative importance of pre-mating reproductive barriers and the local demographic environment as explanations of variation in hybrid frequency in three mapped hybrid zones of Eucalyptus aggregata and E. rubida.

View Full Text PDF Listings View primary source full text article PDFs.

Sep
2011

The present set of experiments tested the hypothesis that the nodal number effects observed in previous studies of stimulus equivalence were due to the confounding factor of training structure that resulted in unequal reinforcement across trial types. In Experiment 1, two 5-member equivalence classes were trained across equal and unequal reinforcement conditions, both with and without a limited hold. A significant nodal effect, as measured by response speed, was found in the equal reinforcement, no-limited-hold condition.

View Full Text PDF Listings View primary source full text article PDFs.

Jul
2010

Previous research suggests that the Relational Completion Procedure may be an effective alternative procedure for studying derived relational responding. However, the parameters that make it effective, relative to traditional match-to-sample, remain to be determined. The present experiment compared the Relational Completion Procedure and match-to-sample protocols for training and testing Same and Opposite derived stimulus relations.

View Full Text PDF Listings View primary source full text article PDFs.

Back to top