MEG event-related desynchronization and synchronization deficits during basic somatosensory processing in individuals with ADHD
ABSTRACT Attention-Deficit/Hyperactivity Disorder (ADHD) is a prevalent, complex disorder which is characterized by symptoms of inattention, hyperactivity, and impulsivity. Convergent evidence from neurobiological studies of ADHD identifies dysfunction in fronto-striatal-cerebellar circuitry as the source of behavioural deficits. Recent studies have shown that regions governing basic sensory processing, such as the somatosensory cortex, show abnormalities in those with ADHD suggesting that these processes may also be compromised.
We used event-related magnetoencephalography (MEG) to examine patterns of cortical rhythms in the primary (SI) and secondary (SII) somatosensory cortices in response to median nerve stimulation, in 9 adults with ADHD and 10 healthy controls. Stimuli were brief (0.2 ms) non-painful electrical pulses presented to the median nerve in two counterbalanced conditions: unpredictable and predictable stimulus presentation. We measured changes in strength, synchronicity, and frequency of cortical rhythms.
Healthy comparison group showed strong event-related desynchrony and synchrony in SI and SII. By contrast, those with ADHD showed significantly weaker event-related desynchrony and event-related synchrony in the alpha (8-12 Hz) and beta (15-30 Hz) bands, respectively. This was most striking during random presentation of median nerve stimulation. Adults with ADHD showed significantly shorter duration of beta rebound in both SI and SII except for when the onset of the stimulus event could be predicted. In this case, the rhythmicity of SI (but not SII) in the ADHD group did not differ from that of controls.
Our findings suggest that somatosensory processing is altered in individuals with ADHD. MEG constitutes a promising approach to profiling patterns of neural activity during the processing of sensory input (e.g., detection of a tactile stimulus, stimulus predictability) and facilitating our understanding of how basic sensory processing may underlie and/or be influenced by more complex neural networks involved in higher order processing.
Full-textDOI: · Available from: Douglas Cheyne, Jun 16, 2015
Click to see the full-text of:
Article: MEG event-related desynchronization and synchronization deficits during basic somatosensory processing in individuals with ADHD
- SourceAvailable from: Alberto Fernandez Jaen[Show abstract] [Hide abstract]
ABSTRACT: INTRODUCTION: Advances in neuroimaging in the last decade have allowed a number of new findings about attention deficit hyperactivity disorder (ADHD) to be obtained. Quickly developing technology, together with the progress being made in genetics and neurochemical research, suggests a dysfunction of the fronto striatal circuit that involves the prefrontal cortex and its relationship with the basal, thalamic and cerebellar nuclei as the pathophysiological foundation of this disorder. On the other hand, neuroimaging in the future may complement clinical evaluation, which will favour more accurate diagnoses and allow the subtypes and even the mode of treatment and its monitoring to be identified. AIMS AND DEVELOPMENT: The aim of this study was to review the more significant literature on neuroimaging and ADHD and to discuss the usefulness and drawbacks of the different modes of neuroimaging techniques that can be applied with a view to gaining an improved and deeper knowledge of ADHD in the future. CONCLUSIONS: Although the development of neuroimaging in ADHD is a promising area, at the present time its diagnostic value is very restricted. One of the greatest difficulties in this respect concerns the clinical, genetic and pathophysiological heterogeneity of the disorder. Hence, given the inexistence of a specific marker, future studies will have to search for several markers that have a suitable value in the diagnosis, prognosis and/or treatment of the different subtypes of ADHD.Revista de neurologia 03/2010; 50 Suppl 3:S125-33. · 0.93 Impact Factor
- [Show abstract] [Hide abstract]
ABSTRACT: The comorbidity of disorders, though it is an extremely common phenomenon, remains unexplained. Among the developmental disorders that are most often diagnosed together are dyslexia and ADHD. The goal of this book is to present a neuropsychological analysis of memory deficits among children with concomitant dyslexia and ADHD. Assuming the perspective of development neuropsychology, the book presents contemporary theoretical perspectives on the specific nature of the double diagnosis of dyslexia and ADHD in children, and general models of the comorbidity of disturbances. This is followed by a discussion of the processes and models of memory from a neuropsychological perspective, with particular attention to microgenetic theory. The specific nature of memory processes in children is also described, in the course of both normal and pathological development. The empirical section of the book presents the results of the author’s own research on memory deficits, as well as their cognitive moderators - attention, language, executive functions, and cognitive style - in four research groups of pupils in the 4th to 6th year of primary school: dyslexic children (n = 60), ADHD (n = 60), both together (n = 60), and children without disturbances as background (n = 60). Carefully chosen methods for evaluating memory were applied, and indicated the occurrence of problems in respect to verbal, visual, and visuospatial memory among all the children from the three clinical groups. Although analysis showed some differences between them, the differentiation is not markedly specific. When the deficits found among the children from the criterial group, i.e. with the double diagnosis, are compared, it turned out that their memory problems are primarily a factor of dyslexia and ADHD, and not something qualitatively unique, i.e. they do not constitute a new, specific symptom. These research results made it possible to differentiate the moderators of memory that are characteristics for each of the clinical groups: 1. In children with ADHD alone, the axial moderators proved to be attention and executive functions; 2. in children with dyslexia, the moderators affecting verbal memory turned out to be language functions, while in respect to visual and visuospatial memory, this role was played primarily by attention; 3. among the children from the criterial group, i.e. with concomitant dyslexia and ADHD, the moderators proved to be attention, language functions, and executive functions. The results presented here are fully consistent with the microgenetic model of the formation of the symptom. The formation of the symptom in children with dyslexia, with ADHD, and with both disorders can constitute a bridge connecting all neurodevelopmental disorders. Beginning with common, non-specific mutations, through distributed differences in the development of brain structures and non-specific symptoms in early childhood, to proximate disturbances of cognitive functions in children with fully symptomatic disturbances, we can observe the visible formation of a common symptom, which consists in the combination of the symptoms of two disorders. Microgenetic theory completes the concept of proximate etiology as a model for double diagnosis. This is the theoretical foundation that allows for a full understanding of the mechanism of comorbidity of neurodevelopmental disorders. The monograph concludes with a summary of the research results, which verify the microgenetic theory of symptom formation, and the development of the author’s own neuropsychological model of memory disturbances in children with a double diagnosis, based on that theory. Directions for further research are indicated. This microgenetic interpretation of the comorbidity of dyslexia and ADHD constitutes the first such attempt, not only in Poland, but in the world.01/2011; Warszawa: Wydawnictwo Naukowe Scholar., ISBN: 978-83-7383-561-0
- [Show abstract] [Hide abstract]
ABSTRACT: The knowledge of the brain processes underlying mental disorders has significantly increased during the last decades, but in spite of this very important research effort a biological marker is not available for such disorders. For example, neurophysiological techniques (EEG and MEG),have been broadly utilized in the investigation of the most important psychiatric syndromes such as schizophrenia, major depression, bipolar disorder or obsessive/compulsive disorder. The outcomes of some of those neurophysiological studies allowed the building of statistical models with very high sensitivity and specificity, although those models did not reach day-to-day clinical practice. A potential explanation for this situation is an inadequate analysis procedure which might be missing some important quantums of information contained in brain signals. In this vein, new methods of non-linear analysis have been proposed for the investigation of neurophysiological data. Particularly, the analysis of brain signals' complexity has been broadly utilized in the investigation of psychiatric disorders. Parameters of EEG-MEG complexity usually estimate the predictability of brain oscillations and/or the number of independent oscillators underlying the observed signals. More importantly, complexity parameters seem to be sensitive to the temporal components of brain activity, and therefore might reflect the dynamical nature of psychiatric disorders. This paper reviews some of the most relevant studies within this field, especially those focusing on the diagnosis, follow-up and prediction of response to treatment.Actas espanolas de psiquiatria 07/2010; 38(4):229-38. · 0.76 Impact Factor