MEG event-related desynchronization and synchronization deficits during basic somatosensory processing in individuals with ADHD

Neurosciences and Mental Health Program, The Hospital for Sick Children, Toronto, Canada. .
Behavioral and Brain Functions (Impact Factor: 1.97). 02/2008; 4(8):8. DOI: 10.1186/1744-9081-4-8
Source: PubMed


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.

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    • "Magnetoencephalography (MEG) measures the spatial and temporal aspects of brain activity. As a result, studies frequently use both ERP and MEG to evaluate the activity in a specific brain region in response to an event [56] . Studies have found impairments in various areas associated with attention in individuals with ADHD. "
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    ABSTRACT: Attention-deficit/hyperactivity disorder (ADHD) is a neurodevelopmental disorder with a long-term impact on functioning, productivity and quality of life of patients. This impact is largely due to the symptoms of inattentiveness. However, despite its impairing role in the lives of ADHD patients, inattentiveness has been studied relatively less frequently than have symptoms of impulsivity/hyperactivity and problems with executive function. This review therefore seeks to integrate the neuropsychological theories and current findings in the research fields of neuropsychology, neurophysiology, and neuroimaging, in an attempt to gain a more complete understanding of the role that inattentiveness plays in ADHD, as well as to suggest directions for future studies. The need for a more comprehensive understanding of inattentiveness and ADHD, which integrates findings from each of the three disciplines mentioned above, is emphasized.
    Neuroscience Bulletin 01/2013; 29(1). DOI:10.1007/s12264-012-1295-6 · 2.51 Impact Factor
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    • "Furthermore, not all impairments associated with ADHD can be explained within the concept of EF [16]. Alterations in more basic perceptual processing [17,18], activation [19] and tempo of information processing [20,21] are reported to influence everyday functioning of individuals with ADHD. A cognitive model of ADHD should therefore describe and operationalize different levels of information processing, their interactions and neurobiological substrates [15]. "
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    ABSTRACT: The Attention Network Test (ANT) generates measures of different aspects of attention/executive function. In the present study we investigated whether adults with ADHD performed different from controls on measures of accuracy, variability and vigilance as well as the control network. Secondly, we studied subgroups of adults with ADHD, expecting impairment on measures of the alerting and control networks in a subgroup with additional symptoms of affective fluctuations. A group of 114 adults (ADHD n = 58; controls n = 56) performed the ANT and completed the Adult ADHD Rating Scale (ASRS) and the Mood Disorder Questionnaire (MDQ). The latter was used to define affective fluctuations. The sex distribution was similar in the two groups, but the ADHD group was significantly older (p = .005) and their score on a test of intellectual function (WASI) significantly lower than in the control group (p = .007). The two groups were not significantly different on measures of the three attention networks, but the ADHD group was generally less accurate (p = .001) and showed a higher variability through the task (p = .033).The significance was only retained for the accuracy measure when age and IQ scores were controlled for. Within the ADHD group, individuals reporting affective fluctuations (n = 22) were slower (p = .015) and obtained a lower score on the alerting network (p = .018) and a higher score on the conflict network (p = .023) than those without these symptoms. The significance was retained for the alerting network (p = .011), but not the conflict network (p = .061) when we controlled for the total ASRS and IQ scores. Adults with ADHD were characterized by impairment on accuracy and variability measures calculated from the ANT. Within the ADHD group, adults reporting affective fluctuations seemed to be more alert (i.e., less impacted by alerting cues), but slower and more distracted by conflicting stimuli than the subgroup without such fluctuations. The results suggest that the two ADHD subgroups are characterized by distinct patterns of attentional problems, and that the symptoms assessed by MDQ contribute to the cognitive heterogeneity characterizing groups of individuals with ADHD.
    Behavioral and Brain Functions 07/2011; 7(1):27. DOI:10.1186/1744-9081-7-27 · 1.97 Impact Factor
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    • "Children with ADHD and tactile defensiveness exhibit significantly larger somatosensory evoked potential (SEP) amplitudes over central electrodes than either controls or ADHD children without tactile defensiveness (Parush et al. 2007). Primary and secondary somatosensory cortical responses to electrical stimulation of the median nerve were measured with MEG from adults with ADHD by Dockstader and colleagues (2008). They found altered patterns of synchronization and desynchronization in the ADHD group. "
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    ABSTRACT: The purpose of this article is to review the role of somatosensory perception in typical development, its aberration in a range of neurodevelopmental disorders, and the potential relations between tactile processing abnormalities and central features of each disorder such as motor, communication, and social development. Neurodevelopmental disorders that represent a range of symptoms and etiologies, and for which multiple peer-reviewed articles on somatosensory differences have been published, were chosen to include in the review. Relevant studies in animal models, as well as conditions of early sensory deprivation, are also included. Somatosensory processing plays an important, yet often overlooked, role in typical development and is aberrant in various neurodevelopmental disorders. This is demonstrated in studies of behavior, sensory thresholds, neuroanatomy, and neurophysiology in samples of children with Fragile X syndrome, autism spectrum disorders (ASD), attention deficit hyperactivity disorder (ADHD), and cerebral palsy (CP). Impaired somatosensory processing is found in a range of neurodevelopmental disorders and is associated with deficits in communication, motor ability, and social skills in these disorders. Given the central role of touch in early development, both experimental and clinical approaches should take into consideration the role of somatosensory processing in the etiology and treatment of neurodevelopmental disorders.
    Journal of Neurodevelopmental Disorders 06/2010; 2(2):62-9. DOI:10.1007/s11689-010-9046-3 · 3.27 Impact Factor
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