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Sutcubasi Kaya B, Metin B, Tas ZC, Buyukaslan A, Soysal A, Hatiloglu D, Tarhan N. Gray Matter Increase in Motor Cortex in Pediatric ADHD: A Voxel-Based Morphometry Study. J Atten Disord 2018; 22:611-618. [PMID: 27469397 DOI: 10.1177/1087054716659139] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
OBJECTIVE Several studies report that ADHD is associated with reduced gray matter (GM), whereas others report no differences in GM volume between ADHD patients and controls, and some even report more GM volume in individuals with ADHD. These conflicting findings suggest that reduced GM is not a universal finding in ADHD, and that more research is needed to delineate with greater accuracy the range of GM alterations. METHOD The present study aimed to identify GM alterations in ADHD using pediatric templates. 19 drug-naïve ADHD patients and 18 controls, all aged 7 to 14 years, were scanned using magnetic resonance imaging. RESULTS Relative to the controls, the ADHD patients had more GM, predominantly in the precentral and supplementary motor areas. Moreover, there were positive correlations between GM volume in these areas and ADHD scale scores. CONCLUSION The clinical and pathophysiological significance of increased GM in the motor areas remains to be elucidated by additional research.
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Affiliation(s)
| | | | | | - Ayse Buyukaslan
- 2 Marmara University, Istanbul, Turkey.,4 Istanbul Medeniyet University, Turkey
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2
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Pediatric applications of functional magnetic resonance imaging. Pediatr Radiol 2015; 45 Suppl 3:S382-96. [PMID: 26346144 DOI: 10.1007/s00247-015-3365-1] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/30/2014] [Revised: 10/31/2014] [Accepted: 02/23/2015] [Indexed: 01/05/2023]
Abstract
Pediatric functional MRI has been used for the last 2 decades but is now gaining wide acceptance in the preoperative workup of children with brain tumors and medically refractory epilepsy. This review covers pediatrics-specific difficulties such as sedation and task paradigm selection according to the child's age and cognitive level. We also illustrate the increasing uses of functional MRI in the depiction of cognitive function, neuropsychiatric disorders and response to pharmacological agents. Finally, we review the uses of resting-state fMRI in the evaluation of children and in the detection of epileptogenic regions.
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MEG analysis of neural dynamics in attention-deficit/hyperactivity disorder with fuzzy entropy. Med Eng Phys 2015; 37:416-23. [DOI: 10.1016/j.medengphy.2015.02.006] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2014] [Revised: 01/29/2015] [Accepted: 02/16/2015] [Indexed: 11/22/2022]
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Sharma A, Couture J. A Review of the Pathophysiology, Etiology, and Treatment of Attention-Deficit Hyperactivity Disorder (ADHD). Ann Pharmacother 2013; 48:209-25. [DOI: 10.1177/1060028013510699] [Citation(s) in RCA: 259] [Impact Index Per Article: 23.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Objective: To review the pathophysiology, etiology, and treatment of attention-deficit hyperactivity disorder (ADHD). Data Sources and Data Extraction: A literature search was conducted in PubMed and EMBASE using the terms attention deficit hyperactive disorder, ADHD, pathophysiology, etiology, and neurobiology. Limits applied were the following: published in the past 10 years (January 2003 to August 2013), humans, review, meta-analysis, and English language. These yielded 63 articles in PubMed and 74 in EMBASE. After removing duplicate/irrelevant articles, 86 articles and their relevant reference citations were reviewed. Data Synthesis: ADHD is a neurological disorder that affects children, but symptoms may persist into adulthood. Individuals suffering from this disorder exhibit hyperactivity, inattention, impulsivity, and problems in social interaction and academic performance. Medications used to treat ADHD such as methylphenidate, amphetamine, and atomoxetine indicate a dopamine/norepinephrine deficit as the neurochemical basis of ADHD, but the etiology is more complex. Moreover, these agents have poor adverse effect profiles and a multitude of drug interactions. Because these drugs are also dispensed to adults who may have concomitant conditions or medications, a pharmacist needs to be aware of these adverse events and drug interactions. This review, therefore, focuses on the pathophysiology, etiology, and treatment of ADHD and details the adverse effects and drug interaction profiles of the drugs used to treat it. Conclusions: Published research shows the benefit of drug therapy for ADHD in children, but given the poor adverse effect and drug interaction profiles, these must be dispensed with caution.
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Affiliation(s)
- Alok Sharma
- MCPHS University, Worcester/Manchester, NH, USA
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Baumeister AA, Henderson K, Pow JL, Advokat C. The early history of the neuroscience of attention-deficit/hyperactivity disorder. JOURNAL OF THE HISTORY OF THE NEUROSCIENCES 2012; 21:263-279. [PMID: 22724488 DOI: 10.1080/0964704x.2011.595649] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Research on the neurobiology and pharmacotherapy of attention-deficit/hyperactivity disorder (ADHD) has grown exponentially since 1980. A reasonable question is whether this research has improved our understanding and treatment of ADHD. This article describes relevant developments that took place roughly between 1900 and 1970. During this time, the efficacy of stimulant therapy for the disorder was established and the symptoms of ADHD were linked to many possible nervous system disorders including in the brain-stem, reticular formation, diencephalon, basal ganglia, frontal lobes, and cortex. In 1970, the catecholamine hypothesis of ADHD was proposed. It is concluded that early theories about the neurobiologic basis of ADHD anticipated core ideas of modern theory.
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Affiliation(s)
- Alan A Baumeister
- Department of Psychology, Louisiana State University, Baton Rouge, LA, USA.
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6
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Pastura G, Mattos P, Gasparetto EL, Araújo APDQC. Advanced techniques in magnetic resonance imaging of the brain in children with ADHD. ARQUIVOS DE NEURO-PSIQUIATRIA 2011; 69:242-52. [PMID: 21537569 DOI: 10.1590/s0004-282x2011000200020] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/16/2010] [Accepted: 09/30/2010] [Indexed: 11/22/2022]
Abstract
Attention deficit hyperactivity disorder (ADHD) affects about 5% of school-aged child. Previous published works using different techniques of magnetic resonance imaging (MRI) have demonstrated that there may be some differences between the brain of people with and without this condition. This review aims at providing neurologists, pediatricians and psychiatrists an update on the differences between the brain of children with and without ADHD using advanced techniques of magnetic resonance imaging such as diffusion tensor imaging, brain volumetry and cortical thickness, spectroscopy and functional MRI. Data was obtained by a comprehensive, non-systematic review of medical literature. The regions with a greater number of abnormalities are splenium of the corpus callosum, cingulate gyrus, caudate nucleus, cerebellum, striatum, frontal and temporal cortices. The brain regions where abnormalities are observed in studies of diffusion tensor, volumetry, spectroscopy and cortical thickness are the same involved in neurobiological theories of ADHD coming from studies with functional magnetic resonance imaging.
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Affiliation(s)
- Giuseppe Pastura
- Departamento de Pediatria, Instituto de Puericultura e Pediatria Martagão Gesteira, Universidade Federal do Rio de Janeiro, Rio de Janeiro, RJ, Brazil.
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Dillo W, Göke A, Prox-Vagedes V, Szycik GR, Roy M, Donnerstag F, Emrich HM, Ohlmeier MD. Neuronal correlates of ADHD in adults with evidence for compensation strategies--a functional MRI study with a Go/No-Go paradigm. GERMAN MEDICAL SCIENCE : GMS E-JOURNAL 2010; 8:Doc09. [PMID: 20421953 PMCID: PMC2858877 DOI: 10.3205/000098] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/19/2010] [Revised: 03/27/2010] [Indexed: 11/30/2022]
Abstract
Objective: Response inhibition impairment is one of the most characteristic symptoms of attention-deficit/hyperactivity disorder (ADHD). Thus functional magnetic resonance imaging (fMRI) during a Go/No-Go task seems to be an ideal tool for examining neuronal correlates of inhibitory control deficits in ADHD. Prior studies have shown frontostriatal abnormalities in children and adolescents. The aim of our study was to investigate whether adults with ADHD would still show abnormal brain activation in prefrontal brain regions during motor response inhibition tasks. Methods: fMRI was used to compare brain activation in 15 untreated adult patients with ADHD and 15 healthy reference volunteers during performance of a Go/No-Go task. Results: In contrast to various other studies with children and adolescents with ADHD, we found no significant difference in the activity of anterior cingulate cortex (ACC) or other frontostriatal structures between ADHD and healthy adults. Significantly enhanced activity was found in the parietal cortex, which is known to play an important role in building up attention. Conclusion: We hypothesize that the enhanced activity is due to the ability of adult ADHD patients to compensate their deficits for a short time, which is demonstrated in our study by equal task performance in both groups.
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Affiliation(s)
- Wolfgang Dillo
- Department of Psychiatry, Socialpsychiatry and Psychotherapy, Hannover Medical School, Hannover, Germany.
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Positron emission tomography neuroimaging for a better understanding of the biology of ADHD. Neuropharmacology 2009; 57:601-7. [DOI: 10.1016/j.neuropharm.2009.08.001] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2009] [Revised: 07/29/2009] [Accepted: 08/04/2009] [Indexed: 11/20/2022]
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Visser J, Jehan Z. ADHD: a scientific fact or a factual opinion? A critique of the veracity of Attention Deficit Hyperactivity Disorder. EMOTIONAL AND BEHAVIOURAL DIFFICULTIES 2009. [DOI: 10.1080/13632750902921930] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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Frank MJ, Scheres A, Sherman SJ. Understanding decision-making deficits in neurological conditions: insights from models of natural action selection. Philos Trans R Soc Lond B Biol Sci 2007; 362:1641-54. [PMID: 17428775 PMCID: PMC2440777 DOI: 10.1098/rstb.2007.2058] [Citation(s) in RCA: 119] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Models of natural action selection implicate fronto-striatal circuits in both motor and cognitive 'actions'. Dysfunction of these circuits leads to decision-making deficits in various populations. We review how computational models provide insights into the mechanistic basis for these deficits in Parkinson's patients and those with ventromedial frontal damage. We then consider implications of the models for understanding behaviour and cognition in attention-deficit/hyperactivity disorder (ADHD). Incorporation of cortical noradrenaline function into the model improves action selection in noisy environments and accounts for response variability in ADHD. We close with more general clinical implications.
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Affiliation(s)
- Michael J Frank
- Departments of Psychology and Neurology, Program in Neuroscience, University of Arizona Tucson, AZ 85721, USA.
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Li X, Jiang J, Zhu W, Yu C, Sui M, Wang Y, Jiang T. Asymmetry of prefrontal cortical convolution complexity in males with attention-deficit/hyperactivity disorder using fractal information dimension. Brain Dev 2007; 29:649-55. [PMID: 17573219 DOI: 10.1016/j.braindev.2007.04.008] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/22/2007] [Revised: 04/24/2007] [Accepted: 04/26/2007] [Indexed: 11/16/2022]
Abstract
BACKGROUND AND PURPOSE Prefrontal cortex, known to be a crucial region for the function of attention, is generally thought to be largely associated with the pathogenesis of attention-deficit hyperactivity disorder (ADHD). Most previous structural imaging studies of ADHD reported abnormality of grey matter volume in prefrontal region. However, volume measure is affected by the size of the interrogated brain, which may cause the inconsistence of the volume based findings. The purpose of the current paper is to use a scale-free measure, fractal information dimension (FID), to assess the prefrontal cortical convolution complexity and asymmetry in ADHD patients. METHODS MRI scans from 12 boys with ADHD and 11 controls were carefully processed. Prefrontal cortex was outlined manually. FIDs of bilateral prefrontal cortical surface were examined in each case. Group differences of the bilateral prefrontal cortical convolution complexities and the asymmetry pattern were statistically tested. RESULTS We found a left-greater-than-right prefrontal cortical convolution complexity pattern in both groups. However, compared with healthy controls, the left prefrontal cortical convolution complexities of ADHD patients were significantly reduced, resulting in significant reduction of the normal left-greater-than-right cortical convolution complexity asymmetry pattern. CONCLUSION This study confirms and extends the existing anatomical knowledge about the brains of people with ADHD. The cortical convolution analysis method may also be applied to quantitatively assess changes in other neuropsychiatric syndromes as well.
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Affiliation(s)
- Xiaobo Li
- National Laboratory of Pattern Recognition, Institute of Automation, Chinese Academy of Sciences, Beijing 100080, PR China
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12
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Franzoni E, Sarajlija J, Garone C, Malaspina E, Marchiani V. No kinetic interaction between levetiracetam and cyclosporine: a case report. J Child Neurol 2007; 22:440-2. [PMID: 17621525 DOI: 10.1177/0883073807301920] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Levetiracetam is a new antiepileptic drug reported to be effective and well-tolerated in adults and children affected by epilepsy. Its lack of hepatic cytochrome metabolism is the theoretic basis for the absence of interactions with other drugs that follow this pathway. We present a 14-year-old girl who underwent orthotopic heart transplantation, followed by antirejection therapy including cyclosporine. Symptomatic occipital lobe epilepsy developed that was successfully treated with oxcarbazepine, but cyclosporine plasma levels decreased to below the antirejection threshold. Oxcarbazepine was replaced by levetiracetam. Levetiracetam did not affect the metabolism of cyclosporine, and cyclosporine plasma levels have remained in the therapeutic range up to now. The patient is still seizure-free and does not complain of any side effects after a 1-year follow-up. Further studies are necessary to confirm the lack of interactions between these drugs, which would make levetiracetam a useful therapeutic option in managing seizure control during antirejection therapy with cyclosporine.
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Affiliation(s)
- Emilio Franzoni
- Child Neuropsychiatry, University of Bologna, Bologna, Italy.
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Castellanos FX, Glaser PEA, Gerhardt GA. Towards a neuroscience of attention-deficit/hyperactivity disorder: Fractionating the phenotype. J Neurosci Methods 2006; 151:1-4. [PMID: 16427130 DOI: 10.1016/j.jneumeth.2005.11.002] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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Carmona S, Vilarroya O, Bielsa A, Trèmols V, Soliva JC, Rovira M, Tomàs J, Raheb C, Gispert JD, Batlle S, Bulbena A. Global and regional gray matter reductions in ADHD: A voxel-based morphometric study. Neurosci Lett 2005; 389:88-93. [PMID: 16129560 DOI: 10.1016/j.neulet.2005.07.020] [Citation(s) in RCA: 196] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2005] [Revised: 07/10/2005] [Accepted: 07/11/2005] [Indexed: 11/26/2022]
Abstract
Attention deficit hyperactivity disorder (ADHD) is a developmental disorder characterized by inattentiveness, motor hyperactivity and impulsivity. According to neuroimaging data, the neural substrate underlying ADHD seems to involve fronto-striatal circuits and the cerebellum. However, there are important discrepancies between various studies, probably due to the use of different techniques. The aim of this study is to examine cerebral gray (GM) and white (WM) matter abnormalities in a group of ADHD children using a voxel-based morphometry protocol. The sample consisted of 25 children/adolescents with DSM-IV TR diagnosis of ADHD (medicated, aged 6-16 years) who were compared with 25 healthy volunteer children/adolescents. ADHD brains on an average showed a global volume decrease of 5.4% as compared to controls. Additionally, there were regionally specific effects in the left fronto-parietal areas (left motor, premotor and somatosensory cortex), left cingulate cortex (anterior/middle/posterior cingulate), parietal lobe (precuneus bilaterally), temporal cortices (right middle temporal gyrus, left parahippocampal gyrus), and the cerebellum (bilateral posterior). There were no differences in WM volume between ADHD children and control subjects. The results are consistent with previous studies that used different techniques, and may represent a possible neural basis for some of the motor and attentional deficits commonly found in ADHD.
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Affiliation(s)
- S Carmona
- Unitat de Recerca en Neurociencia Cognitiva, Departament de Psiquiatria i Medicina Legal, Universitat Autonoma de Barcelona, Campus de Bellaterra, Barcelona, Spain
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Garvey MA, Barker CA, Bartko JJ, Denckla MB, Wassermann EM, Castellanos FX, Dell ML, Ziemann U. The ipsilateral silent period in boys with attention-deficit/hyperactivity disorder. Clin Neurophysiol 2005; 116:1889-96. [PMID: 15979402 DOI: 10.1016/j.clinph.2005.03.018] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2004] [Revised: 02/16/2005] [Accepted: 03/11/2005] [Indexed: 11/18/2022]
Abstract
OBJECTIVE Characterize maturation of transcallosal inhibition (ipsilateral silent period [iSP]) in attention deficit/hyperactivity disorder (ADHD) using transcranial magnetic stimulation (TMS). BACKGROUND Maturation of the iSP is related to acquisition of fine motor skills in typically developing children suggesting that dexterous fine motor skills depend upon mature interhemispheric interactions. Since neuromotor maturation is abnormal in boys with ADHD we hypothesized that iSP maturation in these children would be abnormal. We studied iSP maturation in 12 boys with ADHD and 12 age-matched, typically developing boys, 7-13 years of age. METHODS Surface electromyographic activity was recorded from right first dorsal interosseus (FDI). During background activation, focal TMS was delivered at maximal stimulator output over the ipsilateral motor cortex. RESULTS Maturation of finger speed in boys with ADHD was significantly slower than that in the control group. The iSP latency decreased with age in the control group but not in the ADHD group. CONCLUSIONS These findings suggest the presence of a complex relationship between abnormalities of certain interhemispheric interactions (as represented by iSP latency) and delayed maturation of neuromotor skills in boys with ADHD. SIGNIFICANCE These data provide preliminary physiologic evidence supporting delayed or abnormal development of interhemispheric interactions in boys with ADHD.
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Affiliation(s)
- Marjorie A Garvey
- Pediatric Movement Disorders Unit, Human Motor Control Section, MNB, NINDS, National Institutes of Health, Bethesda, MD 20892, USA.
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Bush G, Valera EM, Seidman LJ. Functional neuroimaging of attention-deficit/hyperactivity disorder: a review and suggested future directions. Biol Psychiatry 2005; 57:1273-84. [PMID: 15949999 DOI: 10.1016/j.biopsych.2005.01.034] [Citation(s) in RCA: 507] [Impact Index Per Article: 26.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/13/2004] [Revised: 11/17/2004] [Accepted: 01/19/2005] [Indexed: 10/25/2022]
Abstract
Over the past few decades, functional neuroimaging techniques have begun to provide unprecedented windows on the neurobiology of attention-deficit/hyperactivity disorder (ADHD) and the neural effects of medications used to treat the disorder. Convergent data from neuroimaging, neuropsychological, genetics, and neurochemical studies have implicated dysfunction of fronto-striatal structures (lateral prefrontal cortex, dorsal anterior cingulate cortex, caudate, and putamen) as likely contributing to the pathophysiology of ADHD. This review 1) provides an overview of the main imaging techniques being used to study ADHD; 2) discusses their relative strengths and weaknesses, highlighting how they can complement one another; 3) shows how the functional imaging literature, which has built on the structural imaging data, is now being used to test focused hypotheses regarding the neurobiological substrate of ADHD; and 4) suggests guidelines for improving future functional imaging studies. Although at present there are no accepted uses for functional imaging in diagnosing ADHD, this article mentions possible future clinical uses of imaging in ADHD.
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Affiliation(s)
- George Bush
- Psychiatric Neuroscience Program and Department of Psychiatry, Harvard Medical School and Massachusettes General Hospital, Boston, Massachusetts, USA.
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Billingsley RL, Jackson EF, Slopis JM, Swank PR, Mahankali S, Moore BD. Functional magnetic resonance imaging of phonologic processing in neurofibromatosis 1. J Child Neurol 2003; 18:731-40. [PMID: 14696899 DOI: 10.1177/08830738030180110701] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Neurofibromatosis 1 is associated with reading disabilities, but few associations between neuroanatomic abnormalities and reading problems have been found. We examined the neuronal bases for phonologic processing, a core component of learning to read, in 15 individuals with neurofibromatosis 1 and 15 controls using functional magnetic resonance imaging (MRI). Our results revealed differential use of inferior and dorsolateral prefrontal cortical areas relative to posterior (temporal, parietal, and occipital) cortices for participants with neurofibromatosis 1 compared with controls during phonologic (rhyme) decisions. In addition, similar to previous brain imaging studies of reading deficits in the general population, poorer performance on one of the phonologic decision tasks was associated with increased signal change in the right superior temporal gyrus for the neurofibromatosis 1 group. Behavioral performance on the functional MRI tasks was related to academic reading measures for the neurofibromatosis 1 group. The differential patterns of functional connectivity observed here lend support to previous morphologic studies that suggested inferior frontal and superior temporal areas to be important mediators of reading and language development in neurofibromatosis 1.
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Affiliation(s)
- Rebecca L Billingsley
- Division of Pediatrics, University of Texas M.D. Anderson Cancer Center, Houston, TX 77030, USA
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Abstract
Numerous studies have shown the importance of the mesocorticolimbic dopamine system in the pathophysiology of attention deficit/hyperactivity disorder. However, there has been inconsistency in the findings of those studies. Varied and sometimes contradictory interpretation has been made on the basis of similar results. It is, therefore, still unclear whether the dopaminergic system is hypo- or hyperfunctioning in attention deficit/hyperactivity disorder. The majority of the functional brain imaging studies in both clinical and experimental settings support hypofunction of the basal ganglia which receive abundant dopaminergic afferent. The experimental studies, using dopamine-depleted animals, also support the hypodopaminergic hypothesis, whereas recent studies with the dopamine transporter knockout/knockdown mouse suggest hyperdopaminergic function as the underlying abnormality. In this review we attempt to clarify the issues raised by previous neuroimaging and functional neuroimaging studies. Research involving animal models with genetic traits, genetic manipulation or with brain lesions is analysed, concentrating on the significance of the dopaminergic system in the abnormal behavior of attention deficit/hyperactivity disorder. In addition, the functional state of the dopaminergic system is considered through the speculated mechanism of psychostimulant therapy of the disorder. No final conclusions have been reached regarding the pathological, biochemical and physiological mechanisms responsible for various symptoms. Inconsistency in the findings and their interpretations may indicate the heterogeneity of the pathogenesis of this syndrome.
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Affiliation(s)
- Masaki Ohno
- Department of Pediatrics, Shiga University of Medical Science, Otsu 520-2192, Japan.
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Sylvester CM, Krout KE, Loewy AD. Suprachiasmatic nucleus projection to the medial prefrontal cortex: a viral transneuronal tracing study. Neuroscience 2003; 114:1071-80. [PMID: 12379260 DOI: 10.1016/s0306-4522(02)00361-5] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
The viral transneuronal labeling method was used to examine whether the suprachiasmatic nucleus (SCN) is linked by multisynaptic connections to the medial prefrontal cortex of the rat. In separate experiments, pseudorabies virus (PRV) was injected into one of the three different cytoarchitectonic regions that comprise the medial prefrontal cortex: infralimbic (Brodmann area 25), prelimbic (Brodmann area 32), and cingulate (Brodmann area 24) cortical areas. After 4-days survival, extensive SCN transneuronal labeling was found following infralimbic cortex (ILC) injections, but almost none occurred when the PRV injections were centered in the prelimbic or cingulate areas. In the ILC cases, transneuronal labeling was localized mainly in the dorsomedial SCN, although a moderate number of labeled neurons were found in the ventrolateral SCN. About 13% of the infected neurons were vasopressin immunoreactive and 4% were vasoactive intestinal polypeptide-positive. Another set of experiments was performed in which the paraventricular thalamic nucleus (PVT) was destroyed 2 weeks prior to making PRV injections into the ILC. Almost no SCN transneuronal labeling occurred in these animals, suggesting that the SCN projection to the ILC is dependent on a relay in the PVT. We propose that the SCN sends timing signals, via its relay in the PVT, to the ILC. This pathway may modulate higher-level brain functions, such as attention, mood, or working memory. Assuming that a homologous circuit exists in humans, we speculate that neurochemical changes affecting this pathway may account for some of the symptoms associated with clinical depression and attention-deficit/hyperactivity disorder.
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Affiliation(s)
- C M Sylvester
- Department of Anatomy and Neurobiology, P.O. Box 8108, Washington University School of Medicine, 660 S. Euclid Avenue, St. Louis, MO 63110-1093, USA
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