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

Colleen Dockstader¹ , William Gaetz² , Douglas Cheyne¹^,2 , Frank Wang¹ , F Xavier Castellanos³ and Rosemary Tannock¹^,4

¹Neurosciences and Mental Health Program, The Hospital for Sick Children, Toronto, Canada

²Department of Diagnostic Imaging, The Hospital for Sick Children, Toronto, Canada

³Child Study Center, New York University, New York, USA

⁴Human Development & Applied Psychology, Ontario Institute for Studies in Education, Toronto, Canada

author email corresponding author email

Behavioral and Brain Functions 2008, 4:8doi:10.1186/1744-9081-4-8


Published:	12 February 2008

Abstract

Background

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.

Methods

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.

Results

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.

Conclusion

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.