76
|
Dockree PM, Barnes JJ, Matthews N, Dean AJ, Abe R, Nandam LS, Kelly SP, Bellgrove MA, O'Connell RG. The Effects of Methylphenidate on the Neural Signatures of Sustained Attention. Biol Psychiatry 2017; 82:687-694. [PMID: 28599833 DOI: 10.1016/j.biopsych.2017.04.016] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/07/2016] [Revised: 03/31/2017] [Accepted: 04/18/2017] [Indexed: 11/19/2022]
Abstract
BACKGROUND Although it is well established that methylphenidate (MPH) enhances sustained attention, the neural mechanisms underpinning this improvement remain unclear. We examined how MPH influenced known electrophysiological precursors of lapsing attention over different time scales. METHODS We measured the impact of MPH, compared with placebo, on behavioral and electrocortical markers while healthy adults (n = 40) performed a continuous monitoring paradigm designed to elicit attentional lapses. RESULTS MPH led to increased rates of target detection, and electrophysiological analyses were conducted to identify the mechanisms underlying these improvements. Lapses of attention were reliably preceded by progressive increases in alpha activity that emerged over periods of several seconds. MPH led to an overall suppression of alpha activity across the entire task but also diminished the frequency of these maladaptive pretarget increases through a reduction of alpha variability. A drug-related linear increase in the amplitude of the frontal P3 event-related component was also observed in the pretarget timeframe (3 or 4 seconds). Furthermore, during immediate target processing, there was a significant increase in the parietal P3 amplitude with MPH, indicative of enhanced perceptual evidence accumulation underpinning target detection. MPH-related enhancements occurred without significant changes to early visual processing (visual P1 and 25-Hz steady-state visual evoked potential). CONCLUSIONS MPH serves to reduce maladaptive electrophysiological precursors of lapsing attention by acting selectively on top-down endogenous mechanisms that support sustained attention and target detection with no significant effect on bottom-up sensory excitability. These findings offer candidate markers to monitor the therapeutic efficacy of psychostimulants or to predict therapeutic responses.
Collapse
|
77
|
Newman DP, Lockley SW, Loughnane GM, Martins ACP, Abe R, Zoratti MTR, Kelly SP, O’Neill MH, Rajaratnam SMW, O’Connell RG, Bellgrove MA. Erratum: Corrigendum: Ocular exposure to blue-enriched light has an asymmetric influence on neural activity and spatial attention. Sci Rep 2017; 7:44958. [PMID: 28332565 PMCID: PMC5362959 DOI: 10.1038/srep44958] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/02/2022] Open
|
78
|
Hawi Z, Cummins TDR, Tong J, Arcos-Burgos M, Zhao Q, Matthews N, Newman DP, Johnson B, Vance A, Heussler HS, Levy F, Easteal S, Wray NR, Kenny E, Morris D, Kent L, Gill M, Bellgrove MA. Rare DNA variants in the brain-derived neurotrophic factor gene increase risk for attention-deficit hyperactivity disorder: a next-generation sequencing study. Mol Psychiatry 2017; 22:580-584. [PMID: 27457811 DOI: 10.1038/mp.2016.117] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/27/2015] [Revised: 04/14/2016] [Accepted: 05/06/2016] [Indexed: 12/26/2022]
Abstract
Attention-deficit hyperactivity disorder (ADHD) is a prevalent and highly heritable disorder of childhood with negative lifetime outcomes. Although candidate gene and genome-wide association studies have identified promising common variant signals, these explain only a fraction of the heritability of ADHD. The observation that rare structural variants confer substantial risk to psychiatric disorders suggests that rare variants might explain a portion of the missing heritability for ADHD. Here we believe we performed the first large-scale next-generation targeted sequencing study of ADHD in 152 child and adolescent cases and 188 controls across an a priori set of 117 genes. A multi-marker gene-level analysis of rare (<1% frequency) single-nucleotide variants (SNVs) revealed that the gene encoding brain-derived neurotrophic factor (BDNF) was associated with ADHD at Bonferroni corrected levels. Sanger sequencing confirmed the existence of all novel rare BDNF variants. Our results implicate BDNF as a genetic risk factor for ADHD, potentially by virtue of its critical role in neurodevelopment and synaptic plasticity.
Collapse
|
79
|
Tong J, McKinley LA, Cummins TDR, Johnson B, Matthews N, Vance A, Heussler H, Gill M, Kent L, Bellgrove MA, Hawi Z. Identification and functional characterisation of a novel dopamine beta hydroxylase gene variant associated with attention deficit hyperactivity disorder. World J Biol Psychiatry 2016; 16:610-8. [PMID: 25975715 DOI: 10.3109/15622975.2015.1036771] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
OBJECTIVES Dysregulation in neurotransmitter signalling has been implicated in the aetiology of attention deficit hyperactivity disorder (ADHD). Polymorphisms of the gene encoding dopamine beta hydroxylase (DBH) have been reported to be associated with ADHD; however, small sample sizes have led to inconsistency. METHODS We conducted transmission disequilibrium test analysis in 794 nuclear families to examine the relationship between DBH and ADHD. The effects of the ADHD-associated polymorphisms on gene expression were assessed by luciferase reporter assays in a human neuroblastoma cell line, SH-SY5Y. RESULTS A SNP within the 3' untranslated region of DBH rs129882 showed a significant association with ADHD (χ(2) = 9.71, p = 0.0018, OR = 1.37). This association remained significant after Bonferroni correction for multiple testing (p = 0.02). Further, allelic variation in rs129882 significantly impacted luciferase expression. Specifically, the C allele of the ADHD-associated rs129882 SNP produced a 2-fold decrease (p < 0.001) in luciferase activity. CONCLUSIONS These data demonstrate for the first time that a DBH gene variant, rs129882, which confers risk to ADHD is also associated with reduced in vitro gene expression. Reduced DBH expression would be consistent with decreased conversion of dopamine to noradrenaline and thus with a relative hypo-noradrenergic state in ADHD.
Collapse
|
80
|
Silk TJ, Beare R, Malpas C, Adamson C, Vilgis V, Vance A, Bellgrove MA. Cortical morphometry in attention deficit/hyperactivity disorder: Contribution of thickness and surface area to volume. Cortex 2016; 82:1-10. [DOI: 10.1016/j.cortex.2016.05.012] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2015] [Revised: 02/23/2016] [Accepted: 05/16/2016] [Indexed: 12/18/2022]
|
81
|
Wang E, Sun L, Sun M, Huang J, Tao Y, Zhao X, Wu Z, Ding Y, Newman DP, Bellgrove MA, Wang Y, Song Y. Attentional Selection and Suppression in Children With Attention-Deficit/Hyperactivity Disorder. BIOLOGICAL PSYCHIATRY: COGNITIVE NEUROSCIENCE AND NEUROIMAGING 2016; 1:372-380. [PMID: 29560866 DOI: 10.1016/j.bpsc.2016.01.004] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/12/2015] [Revised: 01/13/2016] [Accepted: 01/19/2016] [Indexed: 10/22/2022]
Abstract
BACKGROUND Attention-deficit/hyperactivity disorder (ADHD) is a prevalent neurodevelopmental disorder with prominent impairments in directing and sustaining attention. The aim of this study was to identify the neurophysiologic bases of attention deficits in ADHD, focusing on electroencephalography markers of attentional selection (posterior contralateral N2 [N2pc]) and suppression (distractor positivity [PD]). METHODS The electroencephalography data were collected from 135 children 9-15 years old with and without ADHD while they searched for a shape target in either the absence (experiment 1) or the presence (experiment 2) of a salient but irrelevant color distractor. RESULTS In experiment 1, the shape target elicited a smaller N2pc in children with ADHD (n = 38) compared with typically developing children (n = 36). The smaller N2pc amplitude predicted higher levels of inattentive symptoms in children with ADHD. Moreover, the target-elicited N2pc was followed by a positivity in typically developing children but not in children with ADHD. In experiment 2, the salient but irrelevant color distractor elicited a smaller PD component in children with ADHD (n = 32) compared with typically developing children (n = 29). The smaller PD predicted higher inattentive symptom severity as well as lower behavioral accuracy in children with ADHD. CONCLUSIONS The correlation between N2pc/PD amplitudes and ADHD symptom severity suggests that these signals of attentional selection and suppression may serve as potential candidates for neurophysiologic markers of ADHD. Our findings provide a neurophysiologic basis for the subjective reports of attention deficits in children with ADHD and highlight the importance of spatial attention impairments in ADHD.
Collapse
|
82
|
Bastiaansen JA, Cummins TDR, Riese H, van Roon AM, Nolte IM, Oldehinkel AJ, Bellgrove MA. A Population Based Study of the Genetic Association between Catecholamine Gene Variants and Spontaneous Low-Frequency Fluctuations in Reaction Time. PLoS One 2015; 10:e0126461. [PMID: 25978426 PMCID: PMC4433112 DOI: 10.1371/journal.pone.0126461] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2014] [Accepted: 04/03/2015] [Indexed: 11/18/2022] Open
Abstract
The catecholamines dopamine and noradrenaline have been implicated in spontaneous low-frequency fluctuations in reaction time, which are associated with attention deficit hyperactivity disorder (ADHD) and subclinical attentional problems. The molecular genetic substrates of these behavioral phenotypes, which reflect frequency ranges of intrinsic neuronal oscillations (Slow-4: 0.027-0.073 Hz; Slow-5: 0.010-0.027 Hz), have not yet been investigated. In this study, we performed regression analyses with an additive model to examine associations between low-frequency fluctuations in reaction time during a sustained attention task and genetic markers across 23 autosomal catecholamine genes in a large young adult population cohort (n = 964), which yielded greater than 80% power to detect a small effect size (f2 = 0.02) and 100% power to detect a small/medium effect size (f2 = 0.15). At significance levels corrected for multiple comparisons, none of the gene variants were associated with the magnitude of low-frequency fluctuations. Given the study’s strong statistical power and dense coverage of the catecholamine genes, this either indicates that associations between low-frequency fluctuation measures and catecholamine gene variants are absent or that they are of very small effect size. Nominally significant associations were observed between variations in the alpha-2A adrenergic receptor gene (ADRA2A) and the Slow-5 band. This is in line with previous reports of an association between ADRA2A gene variants and general reaction time variability during response selection tasks, but the specific association of these gene variants and low-frequency fluctuations requires further confirmation. Pharmacological challenge studies could in the future provide convergent evidence for the noradrenergic modulation of both general and time sensitive measures of intra-individual variability in reaction time.
Collapse
|
83
|
Cornish KM, Kraan CM, Bui QM, Bellgrove MA, Metcalfe SA, Trollor JN, Hocking DR, Slater HR, Inaba Y, Li X, Archibald AD, Turbitt E, Cohen J, Godler DE. Novel methylation markers of the dysexecutive-psychiatric phenotype in FMR1 premutation women. Neurology 2015; 84:1631-8. [PMID: 25809302 DOI: 10.1212/wnl.0000000000001496] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2014] [Accepted: 12/08/2014] [Indexed: 12/18/2022] Open
Abstract
OBJECTIVE To examine the epigenetic basis of psychiatric symptoms and dysexecutive impairments in FMR1 premutation (PM: 55 to 199 CGG repeats) women. METHODS A total of 35 FMR1 PM women aged between 22 and 55 years and 35 age- and IQ-matched women controls (CGG <45) participated in this study. All participants completed a range of executive function tests and self-reported symptoms of psychiatric disorders. The molecular measures included DNA methylation of the FMR1 CpG island in blood, presented as FMR1 activation ratio (AR), and 9 CpG sites located at the FMR1 exon1/intron 1 boundary, CGG size, and FMR1 mRNA levels. RESULTS We show that FMR1 intron 1 methylation levels could be used to dichotomize PM women into greater and lower risk categories (p = 0.006 to 0.037; odds ratio = 14-24.8), with only FMR1 intron 1 methylation, and to a lesser extent AR, being significantly correlated with the likelihood of probable dysexecutive or psychiatric symptoms (p < 0.05). Furthermore, the significant relationships between methylation and social anxiety were found to be mediated by executive function performance, but only in PM women. FMR1 exon 1 methylation, CGG size, and FMR1 mRNA could not predict probable dysexecutive/psychiatric disorders in PM women. CONCLUSIONS This is the first study supporting presence of specific epigenetic etiology associated with increased risk of developing comorbid dysexecutive and social anxiety symptoms in PM women. These findings could have implications for early intervention and risk estimate recommendations aimed at improving the outcomes for PM women and their families.
Collapse
|
84
|
Johnson BP, Pinar A, Fornito A, Nandam LS, Hester R, Bellgrove MA. Left anterior cingulate activity predicts intra-individual reaction time variability in healthy adults. Neuropsychologia 2015; 72:22-6. [PMID: 25791710 DOI: 10.1016/j.neuropsychologia.2015.03.015] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2014] [Revised: 03/13/2015] [Accepted: 03/16/2015] [Indexed: 11/17/2022]
Abstract
Within-subject, or intra-individual, variability in reaction time (RT) is increasingly recognised as an important indicator of the efficiency of attentional control, yet there have been few investigations of the neural correlates of trial-to-trial RT variability in healthy adults. We sought to determine the neural correlates of intra-individual RT variability during a go/no-go response inhibition task in 27 healthy, male participants. We found that reduced trial-to-trial RT variability (i.e. greater response stability) was significantly associated with greater activation in the left pregenual anterior cingulate. These results support the role of the left anterior cingulate in the dynamic control of attention and efficient response selection. Greater understanding of intra-individual RT variability and top-down attentional control in healthy adults may help to inform disorders that impact executive/attentional control, such as attention deficit hyperactivity disorder and schizophrenia.
Collapse
|
85
|
Tong JHS, Cummins TDR, Johnson BP, McKinley LA, Pickering HE, Fanning P, Stefanac NR, Newman DP, Hawi Z, Bellgrove MA. An association between a dopamine transporter gene (SLC6A3) haplotype and ADHD symptom measures in nonclinical adults. Am J Med Genet B Neuropsychiatr Genet 2015; 168B:89-96. [PMID: 25656223 DOI: 10.1002/ajmg.b.32283] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/06/2014] [Indexed: 01/07/2023]
Abstract
Previous genetic studies have postulated that attention deficit hyperactivity disorder (ADHD) should be regarded as the extreme end of a set of behavioural traits that can be continuously measured in the general population. The current study adopted a quantitative trait approach to examine the relationship between dopamine gene variants and self-reported ADHD symptoms in 517 nonclinical adults. Although genetic associations with variants of both the dopamine transporter (DAT1; SLC6A3) and D4 receptor (DRD4) genes have been reliably reported in children, results in adults are less consistent. We probed two potentially functional variable number of tandem repeat (VNTR) polymorphisms in the 3'UTR and intron 8 of DAT1, the 10-repeat and 6-repeat alleles of which respectively form a haplotype (10/6 DAT1 haplotype) that is associated with childhood ADHD. We also genotyped the exon 3 VNTR of DRD4, the 7-repeat allele of which is also an established risk factor for childhood ADHD. Permutation analysis showed an influence of the 10/6 DAT1 haplotype on both CAARS-G and CAARS-H (DSM-IV ADHD Symptoms Total and ADHD Index respectively), such that ADHD symptom scores increased with each additional copy of the 10/6 DAT1 haplotype. This result survived corrections for multiple comparisons both at the level of genotype and phenotype. A nominal association with CAARS-G was also found for the 7-repeat allele of the DRD4 VNTR however this did not survive multiple comparison correction. Our results provide further support for the influence of variation in the 10/6 DAT1 haplotype and individual differences in ADHD symptoms in adults.
Collapse
|
86
|
Hawi Z, Cummins TDR, Tong J, Johnson B, Lau R, Samarrai W, Bellgrove MA. The molecular genetic architecture of attention deficit hyperactivity disorder. Mol Psychiatry 2015; 20:289-97. [PMID: 25600112 DOI: 10.1038/mp.2014.183] [Citation(s) in RCA: 157] [Impact Index Per Article: 17.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/18/2014] [Revised: 11/14/2014] [Accepted: 11/19/2014] [Indexed: 12/27/2022]
Abstract
Attention deficit hyperactivity disorder (ADHD) is a common childhood behavioral condition which affects 2-10% of school age children worldwide. Although the underlying molecular mechanism for the disorder is poorly understood, familial, twin and adoption studies suggest a strong genetic component. Here we provide a state-of-the-art review of the molecular genetics of ADHD incorporating evidence from candidate gene and linkage designs, as well as genome-wide association (GWA) studies of common single-nucleotide polymorphisms (SNPs) and rare copy number variations (CNVs). Bioinformatic methods such as functional enrichment analysis and protein-protein network analysis are used to highlight biological processes of likely relevance to the aetiology of ADHD. Candidate gene associations of minor effect size have been replicated across a number of genes including SLC6A3, DRD5, DRD4, SLC6A4, LPHN3, SNAP-25, HTR1B, NOS1 and GIT1. Although case-control SNP-GWAS have had limited success in identifying common genetic variants for ADHD that surpass critical significance thresholds, quantitative trait designs suggest promising associations with Cadherin13 and glucose-fructose oxidoreductase domain 1 genes. Further, CNVs mapped to glutamate receptor genes (GRM1, GRM5, GRM7 and GRM8) have been implicated in the aetiology of the disorder and overlap with bioinformatic predictions based on ADHD GWAS SNP data regarding enriched pathways. Although increases in sample size across multi-center cohorts will likely yield important new results, we advocate that this must occur in parallel with a shift away from categorical case-control approaches that view ADHD as a unitary construct, towards dimensional approaches that incorporate endophenotypes and statistical classification methods.
Collapse
|
87
|
Newman DP, O’Connell RG, Bellgrove MA. Corrigendum to “Linking time-on-task, spatial bias and hemispheric activation asymmetry: A neural correlate of rightward attention drift” [Neuropsychologia 51 (2013) 1215–1223]. Neuropsychologia 2015. [DOI: 10.1016/j.neuropsychologia.2014.10.028] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
|
88
|
Cummins TDR, Jacoby O, Hawi Z, Nandam LS, Byrne MAV, Kim BN, Wagner J, Chambers CD, Bellgrove MA. Alpha-2A adrenergic receptor gene variants are associated with increased intra-individual variability in response time. Mol Psychiatry 2014; 19:1031-6. [PMID: 24166412 DOI: 10.1038/mp.2013.140] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/11/2013] [Revised: 09/10/2013] [Accepted: 09/17/2013] [Indexed: 11/09/2022]
Abstract
Intra-individual variability in response time has been proposed as an important endophenotype for attention deficit hyperactivity disorder (ADHD). Here we asked whether intra-individual variability is predicted by common variation in catecholamine genes and whether it mediates the relationship between these gene variants and self-reported ADHD symptoms. A total of 402 non-clinical Australian adults of European descent completed a battery of five cognitive tasks and the Conners' Adult ADHD Rating Scale. Exclusion criteria included the presence of major psychiatric or neurologic illnesses and substance dependency. A total of 21 subjects were excluded due to incomplete data or poor quality cognitive or genotyping data. The final sample comprised 381 subjects (201 males; mean age=21.2 years, s.d.=5.1 years). Principal components analysis on variability measures yielded two factors (response selection variability vs selective attention variability). Association of these factors with catecholamine gene variants was tested using single-step linear regressions, with multiple comparisons controlled using permutation analysis. The response selection variability factor was associated with two ADRA2A single-nucleotide polymorphisms (SNPs) (rs1800544, rs602618), p corrected=0.004, 0.012, respectively, whereas the selective attention variability factor was associated with a TH SNP (rs3842727), p corrected=0.024. A bootstrapping analysis indicated that the response selection variability factor mediated the relationship between the ADRA2A SNP rs1800544 and self-reported ADHD symptoms. Thus this study finds evidence that DNA variation in the ADRA2A gene may be causally related to ADHD-like behaviors, in part through its influence on intra-individual variability. Evidence was also found for a novel association between a TH gene variant and intra-individual variability.
Collapse
|
89
|
Soltész F, Suckling J, Lawrence P, Tait R, Ooi C, Bentley G, Dodds CM, Miller SR, Wille DR, Byrne M, McHugh SM, Bellgrove MA, Croft RJ, Lu B, Bullmore ET, Nathan PJ. Identification of BDNF sensitive electrophysiological markers of synaptic activity and their structural correlates in healthy subjects using a genetic approach utilizing the functional BDNF Val66Met polymorphism. PLoS One 2014; 9:e95558. [PMID: 24760076 PMCID: PMC3997566 DOI: 10.1371/journal.pone.0095558] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2013] [Accepted: 03/28/2014] [Indexed: 12/18/2022] Open
Abstract
Increasing evidence suggests that synaptic dysfunction is a core pathophysiological hallmark of neurodegenerative disorders. Brain-derived neurotropic factor (BDNF) is key synaptogenic molecule and targeting synaptic repair through modulation of BDNF signalling has been suggested as a potential drug discovery strategy. The development of such "synaptogenic" therapies depend on the availability of BDNF sensitive markers of synaptic function that could be utilized as biomarkers for examining target engagement or drug efficacy in humans. Here we have utilized the BDNF Val66Met genetic polymorphism to examine the effect of the polymorphism and genetic load (i.e. Met allele load) on electrophysiological (EEG) markers of synaptic activity and their structural (MRI) correlates. Sixty healthy adults were prospectively recruited into the three genetic groups (Val/Val, Val/Met, Met/Met). Subjects also underwent fMRI, tDCS/TMS, and cognitive assessments as part of a larger study. Overall, some of the EEG markers of synaptic activity and brain structure measured with MRI were the most sensitive markers of the polymorphism. Met carriers showed decreased oscillatory activity and synchrony in the neural network subserving error-processing, as measured during a flanker task (ERN); and showed increased slow-wave activity during resting. There was no evidence for a Met load effect on the EEG measures and the polymorphism had no effects on MMN and P300. Met carriers also showed reduced grey matter volume in the anterior cingulate and in the (left) prefrontal cortex. Furthermore, anterior cingulate grey matter volume, and oscillatory EEG power during the flanker task predicted subsequent behavioural adaptation, indicating a BDNF dependent link between brain structure, function and behaviour associated with error processing and monitoring. These findings suggest that EEG markers such as ERN and resting EEG could be used as BDNF sensitive functional markers in early clinical development to examine target engagement or drug related efficacy of synaptic repair therapies in humans.
Collapse
|
90
|
Dean AJ, Bor W, Adam K, Bowling FG, Bellgrove MA. A randomized, controlled, crossover trial of fish oil treatment for impulsive aggression in children and adolescents with disruptive behavior disorders. J Child Adolesc Psychopharmacol 2014; 24:140-8. [PMID: 24689967 DOI: 10.1089/cap.2013.0093] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
OBJECTIVE Epidemiological research links aggression to low serum concentrations of omega-3 fatty acids, such as those found in fish oil. However, no studies have specifically examined whether fish oil supplementation can reduce the frequency and severity of impulsive aggression in children with disruptive behavior disorders. METHODS Children presenting with impulsive aggression and meeting research criteria for diagnosis of disruptive behavior disorders were randomized to receive either: 1) Fish oil capsules (4 g daily) for 6 weeks followed by placebo (identical-looking capsules) for 6 weeks; or 2) placebo for 6 weeks, followed by fish oil for 6 weeks, in a double-blind, crossover design. Primary outcomes were the Children's Aggression Scale and the Modified Overt Aggression Scale. Secondary outcomes included emotional and behavioral functioning (Strengths and Difficulties Questionnaire [SDQ]), hyperactivity symptoms (Attention-Deficit/Hyperactivity Disorder [ADHD] Rating Scale), family functioning (Family Assessment Device), and cognitive functioning (Stop Signal Task, Trail-Making Task, and Eriksen Flanker Task). Serum concentrations of omega-3 and omega-6 fatty acids were measured at baseline, and at 6 and 12 weeks. RESULTS Twenty-one children participated (81% male; mean age 10.3±2.2 years; range 7-14). Fish oil treatment increased serum concentrations of eicosapentanoic acid (F=14.76, p<0.05) and total omega-3s (F=20.56, p<0.05), but did not influence primary ratings of aggression. In fact, a trend suggested that fish oil worsened a secondary measure of aggression (SDQ Conduct Subscale, F=4.34, p=0.06). Fish oil treatment was associated with an improvement in one rating of hyperactivity (SDQ Hyperactivity Subscale, F=2.22, p<0.05), but did not influence any other outcome measures. CONCLUSIONS These findings suggest that fish oil treatment does not improve aggression in children with disruptive behavior disorders.
Collapse
|
91
|
Nandam LS, Hester R, Bellgrove MA. Dissociable and common effects of methylphenidate, atomoxetine and citalopram on response inhibition neural networks. Neuropsychologia 2014; 56:263-70. [PMID: 24513025 DOI: 10.1016/j.neuropsychologia.2014.01.023] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2013] [Revised: 01/27/2014] [Accepted: 01/31/2014] [Indexed: 11/27/2022]
Abstract
Response inhibition is an executive function that allows the detection and modification of unwanted actions. Its underlying neurochemistry and neurobiology have been explored by combining classic neuropsychological paradigms, such as the go/no-go task (GNG), with targeted pharmacology and functional neuroimaging. We sought to further this literature by using single doses of methylphenidate (30 mg), atomoxetine (60 mg), citalopram (30 mg) and placebo to probe dopaminergic, noradrenergic and serotonergic aspects of response inhibition. Twenty-seven (27) healthy, right-handed males participated in a randomised, double blind, placebo-controlled, within subject, crossover fMRI study to examine stop-related BOLD activation correlates of a modified GNG task. Methylphenidate demonstrated activation versus placebo in the pregenual cingulate (dorsal anterior cingulate), right inferior frontal, left middle frontal, left angular and right superior temporal gyri and right caudate. Atomoxetine demonstrated activation versus placebo across a broad network of cortical regions. Both methylphenidate and atomoxetine, but not citalopram, activated superior temporal, right inferior frontal and left middle frontal clusters. Citalopram only activated the left inferior occipital lobe. Taking the above as functionally defined regions of interest, we examined the specificity of stop-related drug activity by comparing mean activations across the four conditions. Only methylphenidate demonstrated drug-specific effects with increased activation of the pregenual cingulate and decreased activation of the caudate. Direct comparison of methylphenidate and atomoxetine showed broad recruitment of prefrontal regions but specific effects of methylphenidate in the pregenual cingulate and caudate revealing dissociable modulations of response inhibition networks.
Collapse
|
92
|
Bellgrove MA, O’Connell RG, Vance A. Genetics of cognitive deficits in ADHD: clues for novel treatment methods. Expert Rev Neurother 2014; 8:553-61. [DOI: 10.1586/14737175.8.4.553] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
|
93
|
Barnes JJM, O'Connell RG, Nandam LS, Dean AJ, Bellgrove MA. Monoaminergic modulation of behavioural and electrophysiological indices of error processing. Psychopharmacology (Berl) 2014; 231:379-92. [PMID: 23995299 DOI: 10.1007/s00213-013-3246-y] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/30/2012] [Accepted: 08/07/2013] [Indexed: 11/29/2022]
Abstract
RATIONALE Error processing is a critical executive function that is impaired in a large number of clinical populations. Although the neural underpinnings of this function have been investigated for decades and critical error-related components in the human electroencephalogram (EEG), such as the error-related negativity (ERN) and the error positivity (Pe), have been characterised, our understanding of the relative contributions of key neurotransmitters to the generation of these components remains limited. OBJECTIVES The current study sought to determine the effects of pharmacological manipulation of the dopamine, noradrenaline and serotonin neurotransmitter systems on key behavioural and event-related potential correlates of error processing. METHODS A randomised, double-blinded, placebo-controlled, crossover design was employed. Monoamine levels were manipulated using the clinically relevant drugs methylphenidate, atomoxetine and citalopram, in comparison to placebo. Under each of the four drug conditions, participants underwent EEG recording while performing a flanker task. RESULTS Only methylphenidate produced significant improvement in performance accuracy, which was without concomitant slowing of reaction time. Methylphenidate also increased the amplitude of an early electrophysiological index of error processing, the ERN. Citalopram increased the amplitude of the correct-response negativity, another component associated with response processing. CONCLUSIONS The effects of methylphenidate in this study are consistent with theoretical accounts positing catecholamine modulation of error monitoring. Our data suggest that enhancing catecholamine function has the potential to remediate the error-monitoring deficits that are seen in a wide range of psychiatric conditions.
Collapse
|
94
|
Johnson KA, Barry E, Lambert D, Fitzgerald M, McNicholas F, Kirley A, Gill M, Bellgrove MA, Hawi Z. Methylphenidate side effect profile is influenced by genetic variation in the attention-deficit/hyperactivity disorder-associated CES1 gene. J Child Adolesc Psychopharmacol 2013; 23:655-64. [PMID: 24350812 DOI: 10.1089/cap.2013.0032] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
OBJECTIVE A naturalistic, prospective study of the influence of genetic variation on dose prescribed, clinical response, and side effects related to stimulant medication in 77 children with attention-deficit/hyperactivity disorder (ADHD) was undertaken. The influence of genetic variation of the CES1 gene coding for carboxylesterase 1A1 (CES1A1), the major enzyme responsible for the first-pass, stereoselective metabolism of methylphenidate, was investigated. METHODS Parent- and teacher-rated behavioral questionnaires were collected at baseline when the children were medication naïve, and again at 6 weeks while they were on medication. Medication dose, prescribed at the discretion of the treating clinician, and side effects, were recorded at week 6. Blood and saliva samples were collected for genotyping. Single nucleotide polymorphisms (SNPs) were selected in the coding, non-coding and the 3' flanking region of the CES1 gene. Genetic association between CES1 variants and ADHD was investigated in an expanded sample of 265 Irish ADHD families. Analyses were conducted using analysis of covariance (ANCOVA) and logistic regression models. RESULTS None of the CES1 gene variants were associated with the dose of methylphenidate provided or the clinical response recorded at the 6 week time point. An association between two CES1 SNP markers and the occurrence of sadness as a side effect of short-acting methylphenidate was found. The two associated CES1 markers were in linkage disequilibrium and were significantly associated with ADHD in a larger sample of ADHD trios. The associated CES1 markers were also in linkage disequilibrium with two SNP markers of the noradrenaline transporter gene (SLC6A2). CONCLUSIONS This study found an association between two CES1 SNP markers and the occurrence of sadness as a side effect of short-acting methylphenidate. These markers were in linkage disequilibrium together and with two SNP markers of the noradrenaline transporter gene.
Collapse
|
95
|
Chan E, Baumann O, Bellgrove MA, Mattingley JB. Reference frames in allocentric representations are invariant across static and active encoding. Front Psychol 2013; 4:565. [PMID: 24009595 PMCID: PMC3755211 DOI: 10.3389/fpsyg.2013.00565] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2013] [Accepted: 08/08/2013] [Indexed: 11/22/2022] Open
Abstract
An influential model of spatial memory—the so-called reference systems account—proposes that relationships between objects are biased by salient axes (“frames of reference”) provided by environmental cues, such as the geometry of a room. In this study, we sought to examine the extent to which a salient environmental feature influences the formation of spatial memories when learning occurs via a single, static viewpoint and via active navigation, where information has to be integrated across multiple viewpoints. In our study, participants learned the spatial layout of an object array that was arranged with respect to a prominent environmental feature within a virtual arena. Location memory was tested using judgments of relative direction. Experiment 1A employed a design similar to previous studies whereby learning of object-location information occurred from a single, static viewpoint. Consistent with previous studies, spatial judgments were significantly more accurate when made from an orientation that was aligned, as opposed to misaligned, with the salient environmental feature. In Experiment 1B, a fresh group of participants learned the same object-location information through active exploration, which required integration of spatial information over time from a ground-level perspective. As in Experiment 1A, object-location information was organized around the salient environmental cue. Taken together, the findings suggest that the learning condition (static vs. active) does not affect the reference system employed to encode object-location information. Spatial reference systems appear to be a ubiquitous property of spatial representations, and might serve to reduce the cognitive demands of spatial processing.
Collapse
|
96
|
Chan E, Baumann O, Bellgrove MA, Mattingley JB. Negative emotional experiences during navigation enhance parahippocampal activity during recall of place information. J Cogn Neurosci 2013; 26:154-64. [PMID: 23984944 DOI: 10.1162/jocn_a_00468] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Abstract
It is known that the parahippocampal cortex is involved in object-place associations in spatial learning, but it remains unknown whether activity within this region is modulated by affective signals during navigation. Here we used fMRI to measure the neural consequences of emotional experiences on place memory during navigation. A day before scanning, participants undertook an active object location memory task within a virtual house in which each room was associated with a different schedule of task-irrelevant emotional events. The events varied in valence (positive, negative, or neutral) and in their rate of occurrence (intermittent vs. constant). On a subsequent day, we measured neural activity while participants were shown static images of the previously learned virtual environment, now in the absence of any affective stimuli. Our results showed that parahippocampal activity was significantly enhanced bilaterally when participants viewed images of a room in which they had previously encountered negatively arousing events. We conclude that such automatic enhancement of place representations by aversive emotional events serves as an important adaptive mechanism for avoiding future threats.
Collapse
|
97
|
Stjepanović D, Lorenzetti V, Yücel M, Hawi Z, Bellgrove MA. Human amygdala volume is predicted by common DNA variation in the stathmin and serotonin transporter genes. Transl Psychiatry 2013; 3:e283. [PMID: 23860484 PMCID: PMC3731781 DOI: 10.1038/tp.2013.41] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/19/2013] [Accepted: 04/22/2013] [Indexed: 12/16/2022] Open
Abstract
Despite the relevance of changes in amygdala volume to psychiatric illnesses and its heritability in both health and disease, the influence of common genetic variation on amygdala morphology remains largely unexplored. In the present study, we investigated the influence of a number of novel genetic variants on amygdala volume in 139 neurologically healthy individuals of European descent. Amygdala volume was significantly associated with allelic variation in the stathmin (STMN1) and serotonin transporter (SLC6A4) genes, which have been linked to healthy and disordered affective processing. These results were replicated across both manual and automated methods of amygdala parcellation, although manual tracing showed stronger effects, providing a cautionary note to studies relying on automated parcellation methods. Future studies will need to determine whether amygdala volume mediates the impact of stathmin and serotonin transporter gene variants on normal and dysfunctional emotion processing.
Collapse
|
98
|
Newman DP, O'Connell RG, Bellgrove MA. Linking time-on-task, spatial bias and hemispheric activation asymmetry: A neural correlate of rightward attention drift. Neuropsychologia 2013; 51:1215-23. [PMID: 23583973 DOI: 10.1016/j.neuropsychologia.2013.03.027] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2013] [Revised: 03/08/2013] [Accepted: 03/18/2013] [Indexed: 11/17/2022]
|
99
|
Paton K, Hammond P, Barry E, Fitzgerald M, McNicholas F, Kirley A, Robertson IH, Bellgrove MA, Gill M, Johnson KA. Methylphenidate improves some but not all measures of attention, as measured by the TEA-Ch in medication-naïve children with ADHD. Child Neuropsychol 2013; 20:303-18. [PMID: 23639119 DOI: 10.1080/09297049.2013.790358] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
The Test of Everyday Attention for Children (TEA-Ch) is a reliable neuropsychological assessment of attention control in children. Methylphenidate (MPH) is an effective treatment to improve attentional difficulties in children with attention deficit/hyperactivity disorder (ADHD). Previous studies investigating the effects of MPH on attention performance of children with ADHD have produced mixed results and prior MPH usage may have confounded these results. No previous study has tested the effects of MPH on the entire TEA-Ch battery. This study investigated the effects of MPH on attention performance using the entire TEA-Ch in 51 medication-naïve children with ADHD compared with 35 nonmedicated typically developing children. All children were tested at baseline and after 6 weeks: The children with ADHD were medication-naïve at baseline, received MPH for 6 weeks and were tested whilst on medication at the second testing session. A beneficial effect of MPH administration was found on at least one subtest of each of the three forms of attention (selective, sustained, and attentional control) assessed by the TEA-Ch, independent of practice effects. MPH aided performance on the TEA-Ch tasks that were inherently nonarousing and that might require top-down control of attention. It is recommended that the TEA-Ch measures--Sky Search Count (selective attention),Score! (sustained attention), Creature Counting Time Taken for older children (attentional control), and Same Worlds (attentional control) be prioritized for use in future pharmacological studies using MPH.
Collapse
|
100
|
Bellgrove MA, Eramudugolla R, Newman DP, Vance A, Mattingley JB. Influence of attentional load on spatial attention in acquired and developmental disorders of attention. Neuropsychologia 2013; 51:1085-93. [PMID: 23391561 DOI: 10.1016/j.neuropsychologia.2013.01.019] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2012] [Revised: 01/24/2013] [Accepted: 01/25/2013] [Indexed: 12/22/2022]
|