1,721,388 research outputs found
Annotation: What electrical brain activity tells us about brain function that other techniques cannot tell us – a child psychiatric perspective
No full textBackground: Monitoring brain processes in real time requires genuine subsecond resolution to follow the typical timing and frequency of neural events. Non-invasive recordings of electric (EEG/ERP) and magnetic (MEG) fields provide this time resolution. They directly measure neural activations associated with a wide variety of brain states and processes, even during sleep or in infants. Mapping and source estimation can localise these time-varying activation patterns inside the brain. Methods: Recent EEG/ERP research on brain functions in the domains of attention and executive functioning, perception, memory, language, emotion and motor processing in ADHD, autism, childhood-onset schizophrenia, Tourette syndrome, specific language disorder and developmental dyslexia, anxiety, obsessive-compulsive disorder, and depression is reviewed. Results: Over the past two decades, electrophysiology has substantially contributed to the understanding of brain functions during normal development, and psychiatric conditions of children and adolescents. Its time resolution has been important to measure covert processes, and to distinguish cause and effect. Conclusions: In the future, EEG/ERP parameters will increasingly characterise the interplay of neural states and information processing. They are particularly promising tools for multilevel investigations of etiological pathways and potential predictors of clinical treatment response
Integration of electrical imaging with other functional imaging methods
No full textIntegrating evidence from different imaging modalities is important to overcome specific limitations of any given imaging method, such as insensitivity of the EEG to unsynchronized neural events, or the lack of fMRI sensitivity to events of low metabolic demand. Processes that are visible in one modality may be related in a nontrivial way to other processes visible in another modality and insight may only be obtained by integrating both methods through a common analysis. For example, brain activity at rest seems to be at least partly determined by an interaction of cortical rhythms (visible to EEG but not to fMRI) with sub-cortical activity (visible to fMRI, but usually not to EEG without averaging). A combination of EEG and fMRI data during rest may thus be more informative than the sum of two separate analyses in both modalities.
Integration is also an important source of converging evidence about specific aspects and general principles of neural functions and their dysfunctions in certain pathologies. This is because not only electrical, but also energetic, biochemical, hemodynamic and metabolic processes characterize neural states and functions, and because brain structure provides crucial constraints upon neural functions. Focusing on multimodal integration of functional data should not distract from the privileged status of the electric field as the primary direct, noninvasive real-time measure of neural transmission.
The preceding chapters illustrate how electrical neuroimaging has turned scalp EEG into an imaging modality which directly captures the full temporal dynamics of neural activity in the brain
Computer-based cognitive training for ADHD: a review of current evidence
No full textThere has been an increasing interest in and the use of computer-based cognitive training as a treatment of attention-deficit/hyperactivity disorder (ADHD). The authors' review of current evidence, based partly on a stringent meta-analysis of 6 randomized controlled trials (RCTs) published in 2013, and an overview of 8 recently published RCTs highlights the inconsistency of findings between trials and across blinded and nonblinded ADHD measures within trials. Based on this, they conclude that more evidence from well-blinded studies is required before cognitive training can be supported as a frontline treatment of core ADHD symptoms
Neurofeedback for ADHD: a review of current evidence
Full text linkConsiderable scientific effort has been directed at developing effective treatments for attention-deficit/hyperactivity disorder (ADHD). Among alternative treatment approaches, neurofeedback has gained some promising empirical support in recent years from controlled studies as a treatment of core ADHD symptoms. However, a recent stringent meta-analysis of 8 randomized controlled trials published in 2013 found that the effects were stronger for unblinded measures and 3 recent subsequently published well-controlled trials found no effects for the most blinded ADHD outcome. Firmer conclusions must await upcoming evidence from larger controlled studies and future meta-analyses contrasting different forms of neurofeedback and different outcome measures
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
Neural activity before stimulus presentation predicts the success of stimulus retrieval.
No full textThe brain’s information processing is state dependent. In this context, previous research has
shown that pre-stimulus ERP activity predicts later recollection (subsequent memory effect).
In this experiment, we attempted to systematically manipulate the pre-stimulus state by giving the subjects a) a semantic decision task and b) an emotional decision task and after that testing the incidental encoding of each single item presented in the study phase with a
recognition memory test. We recorded and analyzed 65 channel ERPs in 21 healthy volunteers.
We found a significant interactions of task and later memory performance using a TANOVA in two different intervals preceding the words onset (-800 to -400 ms, -400 to 0 ms). When the cue indicated to execute a semantic decision, ERPs of subsequently remembered and forgotten words differed in an interval from -800 to -400 ms. When the cue indicated to execute a emotional decision ERPs of subsequently remembered and forgotten words differed from -400 to 0 ms. This indicates that the neural networks necessary for a successful incidental encoding depend on the task that the subject is preparing. When searching for those networks, Loreta analyses suggested that for the semantic condition, the maximal difference between remembered and forgotten words was in the left middle frontal gyrus that is known to be related to semantic processes. In the emotional condition, the maximal difference was estimated to be in the left middle temporal gyrus. This structure has been related to memory encoding and processing of emotional stimuli. These effects may also reflect latency differences between semantic and emotional preparatory processes important for efficient encoding into episodic memory. This study supports the idea that the formation of lasting memories involves the role of neural activity that both precedes and follows the presentation of a stimulus event
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
Electrical Neuroimaging in the time domain
No full textA publication entitled “A default mode of brain function” initiated a new way of looking at functional imaging data. In this PET study the authors discussed the often-observed consistent decrease of brain activation in a variety of tasks as compared with the baseline. They suggested that this deactivation is due to a task-induced suspension of a default mode of brain function that is active during rest, i.e. that there exists intrinsic well-organized brain activity during rest in several distinct brain regions. This suggestion led to a large number of imaging studies on the resting state of the brain and to the conclusion that the study of this intrinsic activity is crucial for understanding how the brain works.
The fact that the brain is active during rest has been well known from a variety of EEG recordings for a very long time. Different states of the brain in the sleep–wake continuum are characterized by typical patterns of spontaneous oscillations in different frequency ranges and in different brain regions. Best studied are the evolving states during the different sleep stages, but characteristic EEG oscillation patterns have also been well described during awake periods (see Chapter 1 for details). A highly recommended comprehensive review on the brain's default state defined by oscillatory electrical brain activities is provided in the recent book by György Buzsaki, showing how these states can be measured by electrophysiological procedures at the global brain level as well as at the local cellular level
Aggression in children and adolescents
No full textAggressive behaviour is a common phenomenon during childhood and adolescence, but at the same time it is an important associated feature of many psychiatric disorders during this age period. Persistent aggression is related to a variety of negative outcomes in adulthood, including low socioeconomic status and unemployment, criminal behaviour and social isolation. The great heterogeneity of aggressive behaviour still hampers our understanding of causal mechanisms. Still, over the past years, the identification of specific subtypes of aggression has opened possibilities for new and individualized treatment approaches. This article provides information on different subtypes of aggression in children and adolescents, on individual differences that contribute to aggression during development and on possible underlying processes related to aggressive behaviour in young people. Current treatment approaches as well as new emerging treatment possibilities are discussed
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