1,720,982 research outputs found
Brain Networks Involved in Early versus Late Response Anticipation and Their Relation to Conflict Processing
No full textPrevious electrophysiological studies have clearly identified separable neural events underlying early and late components of response anticipation. Functional neuroimaging studies, however, have so far failed to account for this separation. Here, we performed functional magnetic resonance imaging (fMRI) of an anticipation paradigm in 12 healthy adult subjects that reliably produced early and late expectancy waves in the electroencephalogram. We furthermore compared fMRI activations elicited during early and late anticipation to those associated with response conflict. Our results demonstrate the existence of distinct cortical and subcortical brain regions underlying early and late anticipation. Although late anticipatory behavior was associated with activations in dorsal ACC, frontal cortex, and thalamus, brain responses linked to the early expectancy wave were localized mainly in motor and premotor cortical areas as well as the caudate nucleus. Additionally, late anticipation was associated with increased activity in midbrain dopaminergic nuclei, very likely corresponding to the substantia nigra. Furthermore, whereas regions involved in late anticipation proved to be very similar to activations elicited by response conflict, this was not the case for early anticipation. The current study supports a distinction between early and late anticipatory processes, in line with a plethora of neurophysiological work, and for the first time describes the brain structures differentially involved in these processes
Ginkgo biloba Extract EGb 761 (R) in Children with ADHD Preliminary Findings of an Open Multilevel Dose-Finding Study
No full textObjectives: The side effects, nonresponse, and prejudices against conventional pharmacological treatments call for complementary or alternative medical treatments (CAM) for ADHD. One possible treatment, at least for cognitive problems, might be the administration of Ginkgo biloba, though evidence is currently rare. This study tests the clinical efficacy of a Ginkgo biloba special extract (EGb 761 (R)) and its correlation with brain electrical activity in children with ADHD combined type according to DSM-IV. Method: In this open clinical pilot study, EGb 761 (R) was administered to 20 children with ADHD over 3 to 5 weeks. Dosage was increased to a maximum of 240mg daily if attention problems persisted. Possible drug side effects were assessed using the Side Effect Rating Scale. Efficacy was assessed in a multilevel approach including clinical assessment, quality of life (QoL), as well as performance and preparatory brain-electrical activity evoked during a Continuous Performance Test (Cue-CNV in the CPT). Results: A very low rate of mild adverse effects occurred during the observation period. Following EGb 761 (R) administration, possible improvements in QoL, ADHD core symptoms as well as CPT performance were detected. Improved core symptoms were positively related to elevated CNV amplitude. Conclusion: This preliminary evidence suggests that EGb 761 (R) at a maximal dosage of 240mg daily might be a clinically useful alternative treatment for children with ADHD, but further evidence is required before firm conclusions can be made
Flanker-Task in Children Time-Frequency Analyses of Response Monitoring
No full textResponse processing may comprise multiple systems working in parallel at different functional levels of performance monitoring. In time-frequency decompositions of response-locked event-related potentials from adults, a subprocess operating in the delta frequency band was interpreted as an index of cognitive error monitoring, distinguishable from a process with theta frequency probably related to motor control. However, it remains unclear whether such subprocesses can also be distinguished in children. In the current study, error processing was assessed in 22 normal boys aged 8 to 15 years using an Erikson Flanker task. Performance data revealed the expected indices of conflicting task demands, such as increased reaction times and error rates. A clear error-negativity was found in the response-locked event-related potentials after incompatible stimuli, and correct responses show a slow negative deflection immediately preceding the button-press, which is absent in errors. Time-frequency decompositions disclosed that a subprocess in the lower delta band preceding correct responses may reflect a more general action monitoring process sensitive to conflicting task demands that, moreover, may prevent one from making an error if it is active early enough. Processes in the delta and theta bands are modulated specifically by errors and may index motor-related monitoring in children. Moreover, these processes occurred considerably earlier for correct responses compared to errors, suggesting that their timing reflects some performance capacity. These considerations may help to clarify response processing in tasks with conflicting demands
Attention-deficit/hyperactivity disorder (ADHD) and adaptation night as determinants of sleep patterns in children
No full textSleep problems are a prominent feature in children with attention-deficit/hyperactivity disorder (ADHD) but their relationships to sleep structure are not consistent across studies. We aimed at further examining the sleep architecture in children with ADHD, while considering the role of the first-night effect (FNE) as a possible confounder. Twenty unmedicated children with ADHD combined type (8-15 years old; mean 11.24, SD 2.31) and 19 healthy controls, matched for age and gender, underwent polysomnography during an adaptation and a consecutive second night. ADHD and controls displayed a typical FNE without group differences. Independently of testing night, children with ADHD spent more time in sleep and had shortened rapid eye movement (REM) sleep latency and a greater amount of REM sleep relative to controls. However, the increased REM sleep amount in ADHD children was more expressed in the second night when it was also significantly related to scores of inattention and hyperactivity. Our results (1) document similar sleep adaptation processes in children with ADHD and typically developing children, (2) reveal that REM sleep changes in association with ADHD-specific psychopathology may characterize sleep in ADHD children, which is evident only when the FNE is accounted for, (3) indicate that ADHD psychopathology and adaptation night may exert opposite effects on REM sleep in children. These results may prompt the awareness of clinicians about the importance of actual sleep alterations and their precise evaluation in children with ADHD, which could significantly contribute to better diagnostic, treatment and early prevention strategies.German Foundation for Scientific Research (DFG) [436 BUL 112/35/03
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Response inhibition deficits in externalizing child psychiatric disorders: An ERP-study with the Stop-task
Full text linkBACKGROUND: Evidence from behavioural studies suggests that impaired motor response inhibition may be common to several externalizing child psychiatric disorders, although it has been proposed to be the core-deficit in AD/HD. Since similar overt behaviour may be accompanied by different covert brain activity, the aim of this study was to investigate both brain-electric-activity and performance measures in three groups of children with externalizing child psychiatric disorders and a group of normal controls. METHODS: A Stop-task was used to measure specific aspects of response inhibition in 10 children with attention-deficit hyperactivity disorder (AD/HD), 8 children with oppositional defiant disorder/conduct disorder (ODD/CD), 11 children with comorbid AD/HD+ODD/CD and 11 normal controls. All children were between 8 and 14 years old. Event-related potentials and behavioural responses were recorded. An initial go-signal related microstate, a subsequent Stop-signal related N200, and performance measures were analyzed using ANCOVA with age as covariate. RESULTS: Groups did not differ in accuracy or reaction time to the Go-stimuli. However, all clinical groups displayed reduced map strength in a microstate related to initial processing of the Go-stimulus compared to normal controls, whereas topography did not differ. Concerning motor response inhibition, the AD/HD-only and the ODD/CD-only groups displayed slower Stop-signal reaction times (SSRT) and Stop-failure reaction time compared to normal controls. In children with comorbid AD/HD+ODD/CD, Stop-failure reaction-time was longer than in controls, but their SSRT was not slowed. Moreover, SSRT in AD/HD+ODD/CD was faster than in AD/HD-only or ODD/CD-only. The AD/HD-only and ODD/CD-only groups displayed reduced Stop-N200 mean amplitude over right-frontal electrodes. This effect reached only a trend for comorbid AD/HD+ODD/CD. CONCLUSION: Following similar attenuations in initial processing of the Go-signal in all clinical groups compared to controls, distinct Stop-signal related deficits became evident in the clinical groups. Both children with AD/HD and ODD/CD showed deficits in behavioural response-inhibition accompanied by decreased central conflict signalling or inhibition processes. Neither behavioural nor neural markers of inhibitory deficits as found in AD/HD-only and ODD/CD-only were additive. Instead, children with comorbid AD/HD+ODD/CD showed similar or even less prominent inhibition deficits than the other clinical groups. Hence, the AD/HD+ODD/CD-group may represent a separate clinical entity
Pathophysiology of ADHD and associated problems – starting points for Neurofeedback interventions?
No full textAttention deficit hyperactivity disorder (ADHD) is characterized by severe and age-inappropriate levels of hyperactivity, impulsivity and inattention. ADHD is a heterogeneous disorder, and the majority of patients show comorbid or associated problems from other psychiatric disorders. Also, ADHD is associated with cognitive and motivational problems as well as resting-state abnormalities, associated with impaired brain activity in distinct neuronal networks. This needs to be considered in a multimodal treatment, of which neurofeedback may be a promising component. During neurofeedback, specific brain activity is fed-back using visual or auditory signals, allowing the participants to gain control over these otherwise unaware neuronal processes. Neurofeedback may be used to directly improve underlying neuronal deficits, and/or to establish more general self-regulatory skills that may be used to compensate behavioural difficulties.The current manuscript describes pathophysiological characteristics of ADHD, heterogeneity of ADHD subtypes and gender differences, as well as frequently associated behavioural problems such as oppositional defiant/conduct or tic disorder. It is discussed how neurofeedback may be helpful as a treatment approach within these contexts
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