-
[show abstract]
[hide abstract]
ABSTRACT: Autism spectrum disorders (ASDs) are associated with a marked disturbance of neural functional connectivity, which may arise from disrupted organization of white matter. The aim of this study was to use constrained spherical deconvolution (CSD)-based tractography to isolate and characterize major intrahemispheric white matter tracts that are important in visuospatial processing. CSD-based tractography avoids a number of critical confounds that are associated with diffusion tensor tractography, and to our knowledge, this is the first time that this advanced diffusion tractography method has been used in autism research. Twenty-five participants with ASD and aged 25, intelligence quotient-matched controls completed a high angular resolution diffusion imaging scan. The inferior fronto-occipital fasciculus (IFOF) and arcuate fasciculus were isolated using CSD-based tractography. Quantitative diffusion measures of white matter microstructural organization were compared between groups and associated with visuospatial processing performance. Significant alteration of white matter organization was present in the right IFOF in individuals with ASD. In addition, poorer visuospatial processing was associated in individuals with ASD with disrupted white matter in the right IFOF. Using a novel, advanced tractography method to isolate major intrahemispheric white matter tracts in autism, this research has demonstrated that there are significant alterations in the microstructural organization of white matter in the right IFOF in ASD. This alteration was associated with poorer visuospatial processing performance in the ASD group. This study provides an insight into structural brain abnormalities that may influence atypical visuospatial processing in autism. Autism Res 2013, ●●: ●●-●●. © 2013 International Society for Autism Research, Wiley Periodicals, Inc.
Autism Research 03/2013; · 3.69 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Response inhibition deficits are well-documented in drug users, and are related to the impulsive tendencies characteristic of the addictive phenotype. Addicts also show significant motivational issues that may accentuate these inhibitory deficits. We investigated the extent to which these inhibitory deficits are present in abstinence. Salience of the task stimuli was also manipulated on the premise that emotionally-valenced inputs might impact inhibitory efficacy by overcoming the blunted responses to everyday environmental inputs characteristic of this population. Participants performed response inhibition tasks consisting of both neutral and emotionally valenced stimuli while high-density event-related potentials (ERPs) were recorded. Electrophysiological responses (N2/P3 components) to successful inhibitions in abstinent abusers (N=20) and non-using participants (N=21) were compared. In contrast to previous work in current users, our abstinent cohort showed no detectable behavioral or electrophysiological differences in their inhibitory responses, and no differences on self-reports of impulsivity, despite their long histories of chronic use (mean = 10.3 years). The current findings are consistent with a recovery of inhibitory control processes as a function of abstinence. Abstinent former users, however, did show a reduced modulation, relative to controls, of their ERPs to valenced input while performing successful inhibitions, although contrary to our hypothesis, the use of valenced inputs had no impact on inhibitory performance. Reduced ERP modulation to emotionally valenced inputs may have implications for relapse in emotional contexts outside the treatment center.
Neuropharmacology 03/2013; · 4.81 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Neuroimaging studies in current cocaine dependent (CD) individuals consistently reveal cortical hypoactivity across regions of the response inhibition circuit (RIC). Dysregulation of this critical executive network is hypothesized to account for the lack of inhibitory control that is a hallmark of the addictive phenotype, and chronic abuse is believed to compound the issue. A crucial question is whether deficits in this circuit persist after drug cessation, and whether recovery of this system will be seen after extended periods of abstinence, a question with implications for treatment course and outcome. Utilizing functional magnetic resonance imaging (fMRI), we examined activation in nodes of the RIC in abstinent CD individuals (n=27) and non-using controls (n=45) while they performed a motor response inhibition task. In contrast to current users, these abstinent individuals, despite extended histories of chronic cocaine-abuse (average duration of use = 8.2 years), performed the task just as efficiently as non-users. In line with these behavioral findings, no evidence for between-group differences in activation of the RIC was found and instead, robust activations were apparent in both groups within the well-characterized nodes of the RIC. Similarly, our complementary Electroencephalography (EEG) investigation also showed an absence of behavioral and electrophysiological deficits in abstinent drug abusers. These results are consistent with an amelioration of neurobiological deficits in inhibitory circuitry following drug cessation, and could help explain how long-term abstinence is maintained. Finally, regression analyses revealed a significant association between level of activation in the right insula with inhibition success and increased abstinence duration in the CD cohort suggesting that this region may be integral to successful recovery from cocaine addiction.
Neuropharmacology 03/2013; · 4.81 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Extensive evidence indicates that current and recently abstinent cocaine abusers compared to drug-naïve controls have decreased grey matter in regions such as the anterior cingulate, lateral prefrontal and insular cortex. Relatively little is known, however, about the persistence of these deficits in long-term abstinence despite the implications this has for recovery and relapse. Optimized voxel based morphometry was used to assess how local grey matter volume varies with years of drug use and length of abstinence in a cross-sectional study of cocaine users with various durations of abstinence (1-102 weeks) and years of use (0.3-24 years). Lower grey matter volume associated with years of use was observed for several regions including anterior cingulate, inferior frontal gyrus and insular cortex. Conversely, higher grey matter volumes associated with abstinence duration were seen in non-overlapping regions that included the anterior and posterior cingulate, insular, right ventral and left dorsal prefrontal cortex. Grey matter volumes in cocaine dependent individuals crossed those of drug-naïve controls after 35 weeks of abstinence, with greater than normal volumes in users with longer abstinence. The brains of abstinent users are characterized by regional grey matter volumes, which on average, exceed drug-naïve volumes in those users who have maintained abstinence for more than 35 weeks. The asymmetry between the regions showing alterations with extended years of use and prolonged abstinence suggest that recovery involves distinct neurobiological processes rather than being a reversal of disease-related changes. Specifically, the results suggest that regions critical to behavioral control may be important to prolonged, successful, abstinence.
PLoS ONE 01/2013; 8(3):e59645. · 4.09 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Atypical visuospatial processing is commonly described in autism spectrum disorders (ASDs); however the specific neurobiological underpinnings of this phenomenon are poorly understood. Given the extensive evidence suggesting ASDs are characterized by abnormal neural connectivity, this study aimed to investigate network connectivity during visuospatial processing in ASD. Twenty-two males with ASD without intellectual disability and 22 individually matched controls performed a mental rotation task during functional magnetic resonance imaging (MRI) in which two rotated stimuli were judged to be same ("Same Trials") or mirror-imaged ("Mirror Trials"). Behavioral results revealed a relative advantage of mental rotation in the ASD group-controls were slower responding to the more difficult Mirror Trials than Same Trials whereas the ASD group completed Mirror Trials and Same-trials at similar speeds. In the ASD group, brain activity was reduced in frontal, temporal, occipital, striatal, and cerebellar regions and, consistent with previous literature, functional connectivity between a number of brain regions was reduced. However, some connections appeared to be conserved and were recruited in a qualitatively different way by the two groups. As task difficulty increased (on Mirror Trials), controls tended to increase connections between certain brain regions, whereas the ASD group appeared to suppress connections between these regions. There was an interesting exception to this pattern in the visual cortex, a finding that may suggest an advantage in early visual perceptual processing in ASD. Overall, this study has identified a relative advantage in mental rotation in ASD that is associated with aberrant neural connectivity and that may stem from enhanced visual perceptual processing. Autism Res 2012, 5: 314-330. © 2012 International Society for Autism Research, Wiley Periodicals, Inc.
Autism Research 08/2012; 5(5):314-30. · 3.69 Impact Factor
-
Emma J Rose,
Derek W Morris,
Ciara Fahey,
Ian H Robertson,
Ciara Greene,
John O'Doherty,
Fiona N Newell, Hugh Garavan,
Jane McGrath,
Arun Bokde,
Daniela Tropea,
Michael Gill,
Aiden P Corvin,
Gary Donohoe
[show abstract]
[hide abstract]
ABSTRACT: A single nucleotide polymorphism rs12807809 located upstream of the neurogranin (NRGN) gene has been identified as a risk variant for schizophrenia in recent genome-wide association studies. To date, there has been little investigation of the endophenotypic consequences of this variant, and our own investigations have suggested that the effects of this gene are not apparent at the level of cognitive function in patients or controls. Because the impact of risk variants may be more apparent at the level of brain, the aim of this investigation was to delineate whether NRGN genotype predicted variability in brain structure and/or function. Healthy individuals participated in structural (N = 140) and/or functional (N = 36) magnetic resonance imaging (s/fMRI). Voxel-based morphometry was used to compare gray and white matter volumes between carriers of the non-risk C allele (i.e., CC/CT) and those who were homozygous for the risk T allele. Functional imaging data were acquired during the performance of a spatial working memory task, and were also analyzed with respect to the difference between C carriers and T homozygotes. There was no effect of the NRGN variant rs12807809 on behavioral performance or brain structure. However, there was a main effect of genotype on brain activity during performance of the working memory task, such that while C carriers exhibited a load-independent decrease in left superior frontal gyrus/BA10, TT individuals failed to show a similar decrease in activity. The failure to disengage this ventromedial prefrontal region, despite preserved performance, may be indicative of a reduction in processing efficiency in healthy TT carriers. Although it remains to be established whether this holds true in larger samples and in patient cohorts, if valid, this suggests a potential mechanism by which NRGN variability might contribute to schizophrenia risk.
Twin Research and Human Genetics 06/2012; 15(3):296-303. · 1.70 Impact Factor
-
Emma J Rose,
Ciara Greene,
Sinead Kelly,
Derek W Morris,
Ian H Robertson,
Ciara Fahey,
Sarah Jacobson,
John O'Doherty,
Fiona N Newell,
Jane McGrath,
Arun Bokde, Hugh Garavan,
Thomas Frodl,
Michael Gill,
Aiden P Corvin,
Gary Donohoe
[show abstract]
[hide abstract]
ABSTRACT: A common polymorphism within the nitric oxide sythanse-1 (NOS1) gene (rs6490121), initially identified as risk variant for schizophrenia, has been associated with variation in working memory and IQ. Here we investigated how this variation might be mediated at the level of brain structure and function. In healthy individuals (N=157), voxel based morphometry was used to compare grey matter (GM) volume between homozygous and heterozygous carriers of the 'G' allele (i.e. the allele associated with impaired cognition and schizophrenia risk) and homozygous carriers of the non-risk 'A' allele. Functional brain imaging data were also acquired from 48 participants during performance of a spatial working memory (SWM) task, and analysed to determine any effect of NOS1 risk status. An a priori region-of-interest analysis identified a significant reduction in ventromedial prefrontal GM volume in 'G' allele carriers. Risk carriers also exhibited altered patterns of activation in the prefrontal cortex, caudate, and superior parietal lobe, which were characteristic of abnormal increases in activation in frontoparietal working memory networks and a failure to disengage regions of the default mode network. These functional changes suggest a NOS1-mediated processing inefficiency, which may contribute to cognitive dysfunction in schizophrenia. While the mechanisms by which NOS1 may influence brain structure and/or function have not yet been well delineated, these data provide further evidence for a role of NOS1 in risk for schizophrenia via an impact upon cognitive function.
NeuroImage 03/2012; 60(1):614-22. · 5.89 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: The Trail-Making Test (TMT) is a widely used neuropsychological measure that assesses visuomotor abilities and cognitive flexibility. For the TMT-A condition participants are required to locate and connect numbers (i.e. 1-2-3…) while in the TMT-B condition participants perform the set-shifting task of locating and connecting numbers and letters (i.e. 1-A-2-B…). The TMT-B condition has shown impairments in many clinical populations, particularly schizophrenia patients, but the neurobiological underpinning of the task can be difficult to discern given pragmatic obstacles in adapting the task for neuroimaging. In a behavioural testing experiment we demonstrated a close correspondence between performance on the standard TMT and a novel, computer programmed adaptation of the TMT (pcTMT). The pcTMT was designed for functional magnetic resonance imaging (fMRI) administration and neuroimaging data for this task were obtained in. A whole brain analysis revealed significantly greater activation during the pcTMT-B relative to the pcTMT-A in right inferior/middle frontal cortices, right precentral gyrus, left angular gyrus/left middle temporal gyrus. These results identify the regions that most likely underlie cognitive flexibility during the TMT and are candidate regions underlying the impairment of groups with poor set-shifting abilities.
Brain and Cognition 10/2011; 77(1):60-70. · 3.17 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Extensive evidence demonstrates that current cocaine abusers show hypoactivity in anterior cingulate and dorsolateral prefrontal cortex and respond poorly relative to drug-naïve controls on tests of executive function. Relatively little is known about the cognitive sequelae of long-term abstinence in cocaine addicts.
Here, we use a GO-NOGO task in which successful performance necessitated withholding a prepotent response to assay cognitive control in short- and long-term abstinent cocaine users (1-5 weeks and 40-102 weeks, respectively).
We report significantly greater activity in prefrontal, cingulate, cerebellar and inferior frontal gyrii in abstinent cocaine users for both successful response inhibitions and errors of commission. Moreover, this relative hyperactivity was present in both abstinent groups, which, in the presence of comparable behavioral performance, suggests a functional compensation.
Differences between the short- and long-abstinence groups in the patterns of functional recruitment suggest different cognitive control demands at different stages in abstinence. Short-term abstinence showed increased inhibition-related dorsolateral and inferior frontal activity indicative of the need for increased inhibitory control while long-term abstinence showed increased error-related ACC activity indicative of heightened behavioral monitoring. The results suggest that the integrity of prefrontal systems that underlie cognitive control functions may be an important characteristic of successful long-term abstinence.
Drug and alcohol dependence 08/2011; 121(1-2):45-53. · 3.60 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Drug-related stimuli, through conditioning, are thought to acquire incentive motivational properties that code possible reward availability and elicit an attentional bias, possibly through increased "bottom-up" neural processing. The processes underlying this attentional bias are considered important in the maintenance of addiction, and crucially, in relapse among substance users attempting to remain abstinent. Equally, impaired "top-down" cognitive control may impair the ability to restrain "bottom-up" pre-potent behaviours, such as drug use, following exposure to drug-related stimuli. Two experiments sought to identify the neural loci of bottom-up/top-down processing during fMRI. Experiment 1 utilised an attentional bias paradigm to examine the behavioural and neural responses to neutral, emotionally evocative and smoking-related cues in control (n=13), ex-smoking (n=10 - abstinent >12months) and smoking (n=13 - mean >6.5years of use) groups. Experiment 2 used a go/no-go paradigm to examine the neural correlates of motor response inhibition and error monitoring in the same sample. The results of Experiment 1 demonstrated that, across conditions, current smokers had significantly less neural activity in cortical but significantly more activity in subcortical areas compared to both controls and ex-smokers. Ex-smokers exhibited more neural activity than both control and smoker groups in prefrontal cortical regions. Similarly, Experiment 2 revealed that smokers had reduced neural activity in prefrontal cortical regions during motor response inhibition compared to controls while ex-smokers demonstrated greater neural activity in prefrontal cortical regions compared to both controls and smokers during error monitoring. The results reveal cortical and subcortical differences between current smokers and controls and a general pattern of increased prefrontal cortical activity in ex-smokers. These findings may suggest that elevated topdown control might be an important characteristic of successful abstinence in individuals formerly dependent on nicotine.
NeuroImage 03/2011; 56(4):2258-75. · 5.89 Impact Factor
-
Wouter Braet,
Katherine A Johnson,
Claire T Tobin,
Ruth Acheson,
Caroline McDonnell,
Ziarah Hawi,
Edwina Barry,
Aisling Mulligan,
Michael Gill,
Mark A Bellgrove,
Ian H Robertson, Hugh Garavan
[show abstract]
[hide abstract]
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, individuals 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 parahippocampal 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.
Neuropsychologia 01/2011; 49(7):1641-50. · 3.64 Impact Factor
-
Clare Kelly,
Xi-Nian Zuo,
Kristin Gotimer,
Christine L Cox,
Lauren Lynch,
Dylan Brock,
Davide Imperati, Hugh Garavan,
John Rotrosen,
F Xavier Castellanos,
Michael P Milham
[show abstract]
[hide abstract]
ABSTRACT: Models of cocaine addiction emphasize the role of disrupted frontal circuitry supporting cognitive control processes. However, addiction-related alterations in functional interactions among brain regions, especially between the cerebral hemispheres, are rarely examined directly. Resting-state functional magnetic resonance imaging (fMRI) approaches, which reveal patterns of coherent spontaneous fluctuations in the fMRI signal, offer a means to quantify directly functional interactions between the hemispheres. We examined interhemispheric resting-state functional connectivity (RSFC) in cocaine dependence using a recently validated approach, voxel-mirrored homotopic connectivity.
We compared interhemispheric RSFC between 25 adults (aged 35.0 ± 8.8) meeting DSM-IV criteria for cocaine dependence within the past 12 months but currently abstaining (>2 weeks) from cocaine and 24 healthy comparisons (35.1 ± 7.5), group-matched on age, sex, education, and employment status.
We observed reduced prefrontal interhemispheric RSFC in cocaine-dependent participants relative to control subjects. Further analyses demonstrated a striking cocaine-dependence-related reduction in interhemispheric RSFC among nodes of the dorsal attention network, comprising bilateral lateral frontal, medial premotor, and posterior parietal areas. Further, within the cocaine-dependent group, RSFC within the dorsal attention network was associated with self-reported attentional lapses.
Our findings provide further evidence of an association between chronic exposure to cocaine and disruptions within large-scale brain circuitry supporting cognitive control. We did not detect group differences in diffusion tensor imaging measures, suggesting that alterations in the brain's functional architecture associated with cocaine exposure can be observed in the absence of detectable abnormalities in the white matter microstructure supporting that architecture.
Biological psychiatry 01/2011; 69(7):684-92. · 8.93 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Evidence from a number of substance abuse populations suggests that substance abuse is associated with a cluster of differences in cognitive processes. However, investigations of this kind in non-clinical samples are relatively few. The present study examined the ability of alcohol-attentional bias (an alcohol Stroop task), impulsive decision-making (a delay discounting task), and impaired inhibitory control (a GO-NOGO task) to: (a) discriminate problem from non-problem drinkers among a sample of college students; (b) predict scores on the Alcohol Use Disorders Identification Test (AUDIT; a measure of alcohol consumption, drinking behaviour, and alcohol-related problems) across all of the student drinkers; (c) predict AUDIT scores within the subgroups of problem and non-problem student drinkers. In logistic regression controlling for gender and age, student drinkers with elevated alcohol-attentional bias and impulsive decision-making were over twice as likely to be a problem than a non-problem drinker. Multiple regression analysis of the entire sample revealed that all three cognitive measures were significant predictors of AUDIT scores after gender and age had been controlled; the cognitive variables together accounted for 48% of the variance. Moreover, subsequent multiple regressions revealed that impaired inhibitory control was the only significant predictor of AUDIT scores for the group of non-problem drinkers, and alcohol-attentional bias and impulsive decision-making were the only significant predictors of AUDIT scores for the group of problem drinkers. Finally, both impulsive decision-making and impaired inhibitory control were significantly correlated with alcohol-attentional bias across the whole sample. Implications are discussed relating to the development of problematic drinking.
Drug and alcohol dependence 12/2010; 115(1-2):94-100. · 3.60 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Current cocaine-dependent users show reductions in white matter (WM) integrity, especially in cortical regions associated with cognitive control that have been associated with inhibitory dysfunction. A key question is whether these white matter differences are present following abstinence from drug use. To address this, WM integrity was examined using diffusion tensor imaging (DTI) obtained on 43 cocaine abstinent patients (abstinence duration ranged between five days and 102 weeks) and 43 non-using controls. Additionally, a cross-sectional comparison separated the patients into three groups (short-term, mid-term and long-term) based upon duration of cocaine abstinence. The 43 cocaine abstinent patients showed lower fractional anisotropy (FA) in the left anterior callosal fibers, left genu of the corpus callosum, right superior longitudinal fasciculus, right callosal fibers and the superior corona radiata bilaterally when compared against non-using controls. Higher FA in the cocaine abstinent patients was observed in the splenium of the corpus callosum and right superior longitudinal fasciculus. Differences between the cocaine abstinent groups were observed bilaterally in the inferior longitudinal fasciculus, right anterior thalamic radiation, right ventral posterolateral nucleus of the thalamus, left superior corona radiata, superior longitudinal fasciculus bilaterally, right cingulum and the WM of the right precentral gyrus. The results identified WM differences between cocaine abstinent patients and controls as well as distinct differences between abstinent subgroups. The findings suggest that specific white matter differences persist throughout abstinence while other, spatially distinct, differences discriminate as a function of abstinence duration. These differences may, therefore, represent brain changes that mark recovery from addiction.
Drug and alcohol dependence 11/2010; 114(2-3):159-68. · 3.60 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Neuropsychological impairment is a core feature of schizophrenia. Adolescents reporting subclinical psychotic symptoms are considered to be at greater risk of developing a psychotic illness later in life than adolescents who do not report such symptoms and, thus, may represent an at-risk group for further study. We wished to investigate neuropsychological functioning in early adolescence in relation to reports of psychotic symptoms.
Participants were recruited from local primary schools after a two-stage screening and parental consent process. In brief, 277 adolescents were screened and 37 attended for testing. Seventeen adolescents who were deemed to report 'definite' psychotic symptoms after clinical interview and 20 control adolescents underwent a clinical interview and a one-hour neuropsychological battery.
Adolescents who report psychotic symptoms exhibited significant impairments in receptive language (as measured by the British Picture Vocabulary Scale), motor function (as measured by the Pegboard test) and executive function/speed of processing (as measured by the Trail-Making test). There were no significant differences between the groups on measures of attention, memory or expressive language, abstract reasoning or overall scholastic ability.
Taken together with the results from birth cohort, genetic high risk and prodromal studies, these findings are consistent with a neural inefficiency/disconnectivity hypothesis in those at risk for psychosis. These results highlight the need to investigate developmental brain circuits subserving language and motor function and processing speed and how these change over time in at-risk adolescents.
Biological Psychiatry 10/2010; 123(1):71-6. · 8.28 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Evidence suggests that users of ecstasy (3,4-methylenedioxymethamphetamine) have behavioural and cognitive deficits and show increased impulsivity. Impulse control impairments have been shown to be common to a number of addictive behaviours and may constitute a risk factor for drug abuse and dependence. The aim of this study was to investigate brain activation during response inhibition and performance monitoring in current recreational drug users who predominantly used ecstasy. Twenty drug users (ten female) and twenty healthy controls were scanned during performance of a response-inhibition GO/NOGO task using functional magnetic resonance imaging. No performance deficits were evident. However, the drug user group revealed elevated frontal and parietal BOLD response during successful inhibitions, and temporal, frontal, and cingulate hyperactivity during commission errors. In addition, the users showed reduced deactivation in the default-mode network during task performance. Whether contributing to or arising from drug use, these results reveal dysregulation in brain regions subserving cognitive control and default-mode processes in current recreational drug users mirroring effects previously observed for "harder" drugs of abuse.
NeuroImage 08/2010; 52(2):429-35. · 5.89 Impact Factor
-
Hugh Garavan
[show abstract]
[hide abstract]
ABSTRACT: This paper reviews the role of the insula in drug craving. Evidence is presented that drug craving may be a particular instance of the anterior insula's broader role in interoception and subjective feeling states similar, for example, to thirst and hunger. An important role for the insula in craving is supported by evidence of insular activity changing with satiety and with the top-down cognitive modulation of cravings. Cognitive processes involving the insula's role in awareness of one's own behaviour may also contribute to craving insofar as the avoidance of craving might require subjective awareness of the endogenous and exogenous cues that initiate it. Finally, some consideration is given to sex differences and developmental processes in craving.
Brain Structure and Function 06/2010; 214(5-6):593-601. · 5.63 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Although many studies have found similar cortical areas activated during the recognition of objects encoded through vision or touch, little is known about cortical areas involved in the crossmodal recognition of dynamic objects. Here, we investigated which cortical areas are involved in the recognition of moving objects and were specifically interested in whether motion areas are involved in the recognition of dynamic objects within and across sensory modalities. Prior to scanning, participants first learned to recognise a set of 12 novel objects, each presented either visually or haptically, and either moving or stationary. We then conducted fMRI whilst participants performed an old-new task with static images of learned or not-learned objects. We found the fusiform and right inferior frontal gyri more activated to within-modal visual than crossmodal object recognition. Our results also revealed increased activation in area hMT+, LOC and the middle occipital gyrus, in the right hemisphere only, for the objects learned as moving compared to the learned static objects, regardless of modality. We propose that the network of cortical areas involved in the recognition of dynamic objects is largely independent of modality and have important implications for understanding the neural substrates of multisensory dynamic object recognition.
NeuroImage 10/2009; 49(2):1708-16. · 5.89 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Reacting appropriately to errors during task performance is fundamental to successful negotiation of our environment. This is especially true when errors will result in a significant penalty for the person performing a given task, be they financial or otherwise. Error responses and monitoring states were manipulated in a GO/NOGO task by introducing a financial punishment for errors. This study employed a mixed block design alternating between punishment and no punishment (neutral) conditions, enabling an assessment of tonic changes associated with cognitive control as well as trial-specific effects. Behavioural results revealed slower responses and fewer commission errors in the punishment condition. The dorsal anterior cingulate cortex (ACC) had equal trial-specific activity for errors in the neutral and punishment conditions but had greater tonic activity throughout the punishment condition. A region of interest analysis revealed different activation patterns between the dorsal and the rostral parts of the ACC with the rostral ACC having only trial-specific activity for errors in the punishment condition, an activity profile similar to one observed in the nucleus accumbens. This study suggests that there is a motivational influence on cognitive processes in the ACC and nucleus accumbens and hints at a dissociation between tonic proactive activity and phasic reactive error-related activity.
Human Brain Mapping 09/2009; 31(3):458-69. · 5.88 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: It has been consistently shown that ecstasy users display impairments in learning and memory performance. In addition, working memory processing in ecstasy users has been shown to be associated with neural alterations in hippocampal and/or cortical regions as measured by functional magnetic resonance imaging (fMRI). Using functional imaging and a face-learning task, we investigated neural correlates of encoding and recalling face-name associations in 20 recreational drug users whose predominant drug use was ecstasy and 20 controls. To address the potential confounding effects of the cannabis use of the ecstasy using group, a second analysis included 14 previously tested cannabis users (Nestor, L., Roberts, G., Garavan, H., Hester, R., 2008. Deficits in learning and memory: parahippocampal hyperactivity and frontocortical hypoactivity in cannabis users. Neuroimage 40, 1328-1339). Ecstasy users performed significantly worse in learning and memory compared to controls and cannabis users. A conjunction analysis of the encode and recall phases of the task revealed ecstasy-specific hyperactivity in bilateral frontal regions, left temporal, right parietal, bilateral temporal, and bilateral occipital brain regions. Ecstasy-specific hypoactivity was evident in the right dorsal anterior cingulated cortex (ACC) and left posterior cingulated cortex. In both ecstasy and cannabis groups brain activation was decreased in the right medial frontal gyrus, left parahippocampal gyrus, left dorsal cingulate gyrus, and left caudate. These results elucidated ecstasy-related deficits, only some of which might be attributed to cannabis use. These ecstasy-specific effects may be related to the vulnerability of isocortical and allocortical regions to the neurotoxic effects of ecstasy.
Brain research 08/2009; 1292:71-81. · 2.46 Impact Factor
