Phase gradients in ADHD

Proposal details

Title: Phase gradients in ADHD
Research Area(s): ADHD and Allied Conditions
Background: We utilize a new method for measuring event-related phase gradients (PGs) in EEG. The method detects smooth phase-gradients of long spatial wavelength, which indicate the presence spatio-temporal waves. The symptoms of attention deficit/hyperactivity disorder (ADHD) reveal a lack coordination of cognition and behaviour and are associated with low frequency brain activity. Previously published conference abstracts indicate that ADHD subjects have a lack of long wavelength activtity in the delta and slow-wave bands (Alexander et al., 2006a, 2006b). This effect was specific to ADHD and did not occur for FEP, PTSD or AD.
Aims: To explore the differences in ADHD and controls in regard to long wavelength EEG activity. To establish the relationship between previous findings of a deficit in slow-wave and delta wave activity and relate to ERP findings in the literature. To find which aspects of long wavelength EEG activity are associated with the main symptom scales of ADHD i.e. inattentiveness and hyperactivity/impulsivity.
Method: EEG were acquired via the Brain Resource International Database from 175 ADHD subjects and age/gender matched controls (175), during seven tasks: letter viewing (LET), auditory habituation (AH), facial emotion processing (FC), Auditory Oddball (OB), working memory (WM) and Go-Nogo (GNG). Phase gradient measures are extracted from the EEG as described in Alexander et al. (in press). Multple t-tests will be used to distinguish the two groups on the 4 measures (total phase gradients, anterior-posterior waves, peripheral-central waves, right-left waves) for the frequencies 0.2 to 32Hz, from -200ms pre-stimulus to 800ms post-stimulus. The same measures will be correlated with symptom scores (inattentiveness and hyperactivity/impulsivity) to see which elements of long wavelength activity predict symptomology, controlling for age. To avoid type I errors, in each of these analyses, only 20 contiguous time/frequency points where p