ORCID Profile
0000-0001-7708-1177
Current Organisation
University College Dublin
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Publisher: Springer Science and Business Media LLC
Date: 28-11-2006
Publisher: Wiley
Date: 14-12-2011
Publisher: Wiley
Date: 03-02-2009
DOI: 10.1002/AJMG.B.30921
Publisher: SAGE Publications
Date: 06-03-2022
DOI: 10.1177/10870547221081266
Abstract: Difficulty with sustaining attention to a task is a hallmark of ADHD. It would be useful to know which measures of sustained attention best predict a diagnosis of ADHD. Participants were 129 children with a diagnosis of ADHD and 129 matched controls who completed the fixed Sustained Attention to Response Task (SART). The number of commission and omission errors, standard deviation of response time (SDRT), tau, fast and slow frequency variability, d-prime, and mu were able to successfully classify children with and without ADHD. The mean response time, criterion, and sigma were not able to classify participants. The best classifiers were d-prime (0.75 Area Under the Receiver Operated Characteristic), tau (.74), SDRT (0.74), omission errors (0.72), commission errors (0.71), and SFAUS (0.70). This list of the best classifier measures derived from the SART may prove useful for the planning of future studies.
Publisher: Wiley
Date: 28-12-2007
DOI: 10.1002/AJMG.B.30659
Abstract: There are conflicting reports suggesting that the parental origin of transmitted risk alleles may play a role in the etiology of attention deficit/hyperactivity disorder (ADHD). A recent report by Hawi and colleagues observed a generalized paternal over-transmission of alleles associated with ADHD. This was not replicated in more recent studies. Using data from a large multicenter study we examined the overall and gene-specific parent of origin effect in 554 independent SNPs across 47 genes. Transmission disequilibrium and explicit parent of origin test were performed using PLINK. Overall parent of origin effect was tested by Chi-square. There was no overall parent of origin effect in the IMAGE s le (chi(1)(2) = 1.82, P = 0.117). Five markers in three genes, DDC, TPH2, and SLC6A2 showed nominal association (P < 0.01) with ADHD combined subtype when restricted to maternal or paternal transmission only. Following the initial report by Hawi and co-workers three studies, including this one, found no evidence to support an overall parent of origin effect for markers associated with ADHD. We cannot however, exclude gene-specific parent of origin effect in the etiology ADHD.
Publisher: Bentham Science Publishers Ltd.
Date: 31-07-2014
Publisher: Elsevier BV
Date: 06-2011
DOI: 10.1016/J.NEUROPSYCHOLOGIA.2011.01.001
Abstract: The DAT1 gene codes for the dopamine transporter, which clears dopamine from the synaptic cleft, and a variant of this gene has previously been associated with compromised response inhibition in both healthy and clinical populations. This variant has also been associated with ADHD, a disorder that is characterised by disturbed dopamine function as well as problems with response inhibition. In the present study we used fMRI to investigate the role of dopaminergic genetic variation on executive functioning by comparing how activation associated with successful and unsuccessful inhibitions differs based on DAT1-genotype and ADHD-diagnosis in adolescents performing a go/nogo task. The results identify regional specificity concerning which functional differences can be attributed to the possession of the high risk DAT1 genotype, the clinical condition or an interaction between the two. During response inhibition, in iduals with two copies of the 10-repeat allele showed increased activation in frontal, medial, and parietal regions, which may indicate that inhibition is more effortful for this group. Conversely, this group displayed a reduced error response in the parahippoc al gyrus, suggestive of reduced learning from errors. There were also a number of frontal, parietal, medial and occipital regions, where the relationship between genotype and fMRI-activation differed between the ADHD group and the typically developing adolescents. Finally, the ADHD group displayed decreased activation in parietal and (pre)frontal regions during response inhibition, and in frontal and medial brain regions on error trials.
Publisher: Wiley
Date: 05-2008
DOI: 10.1002/AJMG.B.30737
Abstract: Several independent studies have reported association between serotonin transporter gene (SLC6A4) polymorphisms and attention deficit hyperactivity disorder (ADHD). Five studies found evidence for association between the long-allele of a 44-bp insertion/deletion polymorphism (5-HTTLPR) and ADHD. Another two studies corroborated this finding while a further six studies did not find such an association. For a second polymorphism within the gene, a variable number tandem repeat (VNTR) within intron 2, one study demonstrated that the 12/12 genotype was significantly less frequent in ADHD cases compared to controls, while a second study found that the 12-allele was preferentially transmitted to offspring affected with ADHD. To provide further clarification of the reported associations, we investigated the association of these two markers with ADHD in a s le of 1,020 families with 1,166 combined type ADHD cases for the International Multi-Centre ADHD Genetics project, using the Transmission Disequilibrium Test. Given the large body of work supporting the association of the promoter polymorphism and mood disorders, we further analyzed the group of subjects with ADHD plus mood disorder separately. No association was found between either of the two markers and ADHD in our large multisite study or with depression within the s le of ADHD cases.
Publisher: Wiley
Date: 10-2008
Publisher: Elsevier BV
Date: 10-2008
Publisher: Informa UK Limited
Date: 07-2019
DOI: 10.2147/NDT.S210227
Publisher: Springer Science and Business Media LLC
Date: 08-01-2008
Abstract: As part of the International Multi-centre ADHD Genetics project we completed an affected sibling pair study of 142 narrowly defined Diagnostic and Statistical Manual of Mental Disorders, fourth edition combined type attention deficit hyperactivity disorder (ADHD) proband-sibling pairs. No linkage was observed on the most established ADHD-linked genomic regions of 5p and 17p. We found suggestive linkage signals on chromosomes 9 and 16, respectively, with the highest multipoint nonparametric linkage signal on chromosome 16q23 at 99 cM (log of the odds, LOD=3.1) overlapping data published from the previous UCLA (University of California, Los Angeles) (LOD>1, approximately 95 cM) and Dutch (LOD>1, approximately 100 cM) studies. The second highest peak in this study was on chromosome 9q22 at 90 cM (LOD=2.13) both the previous UCLA and German studies also found some evidence of linkage at almost the same location (UCLA LOD=1.45 at 93 cM German LOD=0.68 at 100 cM). The overlap of these two main peaks with previous findings suggests that loci linked to ADHD may lie within these regions. Meta-analysis or reanalysis of the raw data of all the available ADHD linkage scan data may help to clarify whether these represent true linked loci.
Publisher: Elsevier BV
Date: 04-2010
DOI: 10.1016/J.NEUROPSYCHOLOGIA.2009.12.026
Abstract: Children with Attention Deficit Hyperactivity Disorder (ADHD) often show spatial attentional deficits, exhibiting a subtle rightwards bias, possibly due to dysfunction within the right hemisphere fronto-parietal network. Approximately 50% of children with ADHD also show signs of movement dysfunction. The nature of this movement dysfunction and possible interactions with spatial attention difficulties has not been clearly described. This study compared 31 children with and 31 children without ADHD on a movement kinematic task that tested hand-drawing movement precision. Participants used an electronic pen on a digitizing tablet. The pen tip position was s led as X and Y coordinates at 200Hz. The task was to join targets of either 10 or 20mm diameter that were separated by a distance of 62.5 or 125 mm. Constant error in the X and Y planes, peak absolute velocity and acceleration, movement time, the number of pauses and pause time were analysed. Apart from a significantly increased rate of acceleration across all conditions, the children with ADHD demonstrated no temporal difficulties with the task rather they showed subtle spatial difficulties, possibly suggestive of cerebellar involvement. The children with ADHD showed difficulties in accuracy of movement towards the right. They were less accurate in the X plane when moving towards the right-sided targets over the long distance. Greater variability in target accuracy was shown when moving towards the small target on the right side. The children with ADHD made significantly more pauses on the left target, when preparing the right movement, than the control group. These results suggest that the subtle spatial bias towards the right that has been demonstrated in ADHD in spatial attention also extends into the continuous movement domain.
Publisher: Wiley
Date: 21-11-2008
DOI: 10.1111/J.1469-7610.2008.01936.X
Abstract: An important theory of attention suggests that there are three separate networks that execute discrete cognitive functions. The 'alerting' network acquires and maintains an alert state, the 'orienting' network selects information from sensory input and the 'conflict' network resolves conflict that arises between potential responses. This theory holds promise for dissociating discrete patterns of cognitive impairment in disorders where attentional deficits may often be subtle, such as in attention deficit hyperactivity disorder (ADHD). The Attentional Network Test (ANT), a behavioural assay of the functional integrity of attention networks, was used to examine the performance of 73 children with ADHD and 73 controls. Performance on the ANT clearly differentiated the children with and without ADHD in terms of mean and standard deviation (SD) of reaction time (RT), the number of incorrect responses made and the number of omission errors made. The ADHD group demonstrated deficits in the conflict network in terms of slower RT and a higher number of incorrect responses. The ADHD group showed deficits in the alerting network in terms of the number of omission errors made. There was no demonstration of a deficit in the orienting network in ADHD on this task. The children with ADHD demonstrated deficits in the alerting and conflict attention networks but normal functioning of the orienting network.
Publisher: Springer Science and Business Media LLC
Date: 19-09-2008
Publisher: American Medical Association (AMA)
Date: 12-2013
DOI: 10.1001/JAMAPSYCHIATRY.2013.2174
Abstract: The neurobiological underpinnings of attention-deficit/hyperactivity disorder (ADHD) and particularly those associated with the persistence of ADHD into adulthood are not yet well understood. The correlation patterns in spontaneous neural fluctuations at rest are known as resting-state functional connectivity (RSFC) and could characterize ADHD-specific connectivity changes. To determine the specific location of possible ADHD-related differences in RSFC between adults diagnosed as having ADHD in childhood and control subjects. DESIGN Using resting-state functional magnetic resonance imaging, we calculated and compared functional connectivity from attention, affective, default, and cognitive control networks involved in the psychopathology of ADHD between the ADHD and control groups. SETTING University psychiatric service and magnetic resonance imaging research center. Sixteen drug-free adults (5 women and 11 men mean age, 24.5 years) diagnosed with combined-type ADHD in childhood and 16 healthy controls matched for age (mean age, 24.4 years), sex, handedness, and educational level recruited from the community. Functional magnetic resonance imaging. Connectivity data from ventral and dorsal attention, affective, default, and cognitive control networks and ADHD symptoms derived from ADHD-specific rating instruments. Adults with ADHD showed significantly decreased RSFC within the attention networks and increased RSFC within the affective and default mode and the right lateralized cognitive control networks compared with healthy controls (P < .01, familywise error for whole-brain cluster correction). Lower RSFC in the ventral and dorsal attention network was significantly correlated with higher levels of ADHD symptoms (P < .001). These RSFC findings might underpin a biological basis for adult ADHD and are functionally related to persistent inattention, disturbance in cognitive control, and emotional dysregulation in adults with ADHD. These findings need to be understood in the context of all aspects of brain function in ADHD.
Publisher: Wiley
Date: 19-11-2007
DOI: 10.1002/AJMG.B.30596
Abstract: A major goal of genetic studies of attention deficit hyperactivity disorder (ADHD) is to identify in idual characteristics that might help segregate the disorder's inherent heterogeneity. [Mill et al. (2006) Arch Ger Psychiatry 63:462-469] recently reported a potentially important association between two dopamine-related risk polymorphisms (DRD4 variable number tandem repeat (VNTR) in exon 3 and DAT1 VNTR in the 3' UTR) and lowered IQ in ADHD. The objective of the current study was to replicate the [Mill et al. (2006) Arch Ger Psychiatry 63:462-469] findings in a clinical s le and to extend the analysis to a large range of alternative SNP markers of putative ADHD risk alleles identified in a recent study [Brookes et al. (2006) Mol Genet 11:934-953]. Participants were 1081 children and adolescents with a research-confirmed combined type ADHD diagnosis and 1300 unaffected siblings who took part in the International Multi-centre ADHD Genetics (IMAGE) project. They were recruited from multiple settings from across Europe: Belgium, Britain, Germany, Ireland, Israel, Netherlands, Spain and Switzerland. The results were that ADHD was associated with reduced IQ. However, there was no association between the two dopamine-related risk polymorphisms and IQ in either the probands or their siblings. Furthermore, other selected genetic markers previously demonstrated to be associated with ADHD in this s le were not associated with IQ. This large scale study with a clinically ascertained and regorously diagnosed s le failed to replicate the association between genetic polymorphisms in the dopamine system and IQ in ADHD. We also observed no association of other SNPs with IQ in ADHD.
Publisher: Wiley
Date: 24-10-2008
DOI: 10.1002/AJMG.B.30871
Abstract: Attention-deficit/hyperactivity disorder (ADHD) is typically characterized by inattention, excessive motor activity, impulsivity, and distractibility. In iduals with ADHD have significant impairment in family and peer relations, academic functioning, and show high co-morbidity with a wide range of psychiatric disorders including oppositional defiant disorder (ODD), conduct disorder (CD), anxiety disorder, depression, substance abuse, and pervasive developmental disorder (PDD). Family studies suggest that ADHD + CD represents a specific subtype of the ADHD disorder with familial risk factors only partly overlapping with those of ADHD alone. We performed a hypothesis-free analysis of the GAIN-ADHD s le to identify markers and genes important in the development of conduct problems in a European cohort of in iduals with ADHD. Using the Family-Based Association Test (FBAT) package we examined three measures of conduct problems in 1,043,963 autosomal markers. This study is part of a series of exploratory analyses to identify candidate genes that may be important in ADHD and ADHD-related traits, such as conduct problems. We did not find genome-wide statistical significance (P < 5 x 10(-7)) for any of the tested markers and the three conduct problem traits. Fifty-four markers reached strong GWA signals (P < 10(-5)). We discuss these findings in the context of putative candidate genes and the implications of these findings in the understanding of the etiology of ADHD + CD. We aimed to achieve insight into the genetic etiology of a trait using a hypothesis-free study design and were able to identify a number of biologically interesting markers and genes for follow-up studies.
Publisher: American Medical Association (AMA)
Date: 10-2009
DOI: 10.1001/ARCHGENPSYCHIATRY.2009.120
Abstract: A distinct pattern of selective attention deficits in attention-deficit/hyperactivity disorder (ADHD) has been difficult to identify. Heterogeneity may reflect differences in underlying genetics. To document an objective deficit of selective attention in a large s le of children with and without ADHD using spatial orienting paradigms. By stratifying s les according to the gene dosage of a risk haplotype of the dopamine transporter gene (DAT1), we could determine whether genetic factors predict spatial inattention in ADHD. A case-control design was used. Children with ADHD were recruited from clinics or support groups in Ireland. Typically developing children were recruited from schools in and around Dublin, Ireland. One hundred fifteen children were recruited (ADHD = 50, control = 65). Groups were matched for age but differed in estimated intelligence. Two versions of a visual spatial orienting task in which attention was directed by valid, neutral, or invalid cues to target locations. Sudden-onset peripheral cues (exogenous) and centrally presented predictive cues (endogenous) were used. To isolate an attention deficit in ADHD, groups were first compared using analysis of variance on the spatial orienting tasks. Multiple regression was used to assess the main effect of DAT1 haplotype status (heterozygous vs homozygous) and the interaction of diagnosis and genotype on those variables that discriminated children with and without ADHD. Children with ADHD displayed deficits in reorienting attention from invalidly cued spatial locations, particularly for targets in the left visual field. DAT1 haplotype status predicted spatial reorienting deficits for left visual field targets (P = .007) but there was also a significant interaction of diagnosis and genotype (P = .02), which revealed the greatest impairment in children with ADHD homozygous for the DAT1 haplotype. Heterogeneity in selective attention in ADHD can be explained by a replicated genetic risk factor for ADHD, the 10/3 DAT1 haplotype.
Publisher: Springer Science and Business Media LLC
Date: 24-07-2008
DOI: 10.1007/S11845-008-0184-5
Abstract: The social communication questionnaire (SCQ) for autistic spectrum disorder was previously validated in clinical populations. To describe the distribution of SCQ-scores in the general child population, and identify if traits from all domains of autism are present. The SCQ was completed by parents of children attending a mixed-gender primary school of 240 children. Total SCQ scores ranged from 1 to 20, with a mode 1 and corrected mean of 3.89, SD = 2.77. SCQ items corresponding to all three domains of autism were found in the s le. Some items on the SCQ were answered as "autism-positive" for up to 41.8% of children in the general population s le. The SCQ has a wide range in the general population, with traits from all three domains of autism. Some items in the SCQ do not discriminate children with autism from other school-going children.
No related grants have been discovered for Aisling Mulligan.