Gamma synchrony in ADHD

Proposal details

Title: Gamma synchrony in ADHD
Research Area(s): ADHD and Allied Conditions
Background: A recent area of psychophysiological research is the Gamma band (31-63 Hz), which is suggested to be functionally associated with integrative conscious stimulus evaluation. Core symptomology of Attention Deficit/Hyperactivity Disorder (AD/HD) including impulsiveness, hyperactivity and inattentiveness is suggestive of atypical integration of information within the brain (and hence predicted gamma abnormality), yet only one study to date has investigated gamma in relation to AD/HD (Yordanova et al., 2002). Yordanova et al. (2002) investigated early event-related gamma oscillations 0-120ms during a selective attention auditory oddball task, while having children press a button with their right hand following a target tone presented to the attended side. It was reported that event-related gamma oscillations differed between children (9-12 years, DSM-III-R criteria ) with and without ADHD. Those with ADHD produced larger and more strongly phase-locked gamma when auditory stimuli were presented to the right ear, independent to whether they were asked to attend to this side or not (Yordanova et al.). Yordonova et al. proposed that this was not a reflection of an over arousing response to auditory stimuli, nor a different over reactive habituation response. Rather, the results were associated with pre-processed motor task related mechanisms, in support of motor inhibition models of AD/HD, related to a poorly controlled motor program of the right hand. The proposed manuscript will further Yordanova et al (2001) in many ways. Firstly, it will use current DSM-IVR criteria. Secondly, it will feature a larger age range, with participants to be children 6-17 years (Yordanova used children 9-12 years) with and without AD/HD (combined and inattentive subtypes) . Also, Yordanova et al. had children pressing a button with their right hand to target tones, which may have lead to the asymmetrical gamma differences reported. Methodology employed by BRC (and hence this manuscript) during the auditory oddball requires children to press with both hands, and thus this problem will be rectified. Lastly, this manuscript will correlate gamma with arousal, as measured by EDA. As, arousal is proposed to exert control over gamma, a measure which has been consistently been reported to be atypical in AD/HD. Yordanova, J., Banaschewski, T., Kolev, V., Woerner, W., & Rothenberger, A. (2001). Abnormal early stages of task stimulus processing in children with attention-deficit hyperactivity disorder--evidence from event-related gamma oscillations. Clin Neurophysiol, 112(6), 1096-1108.
Aims: The aim of the study is to compare gamma (early and late bursts) during the auditory oddball task in children with and without ADHD (inattentive and combined subtypes).
Method: Participants: Male ADHDin, ADHDcom and aged-matched controls (dependent on numbers of ADHD children in database), aged between 6-17. This study will look at gamma (early and late bursts) and EDA (tonic and phasic) from the auditory oddball paradigm.