Reduced Power in Fronto-Parietal Theta EEG Linked to Impaired Attention-Sampling in Adult ADHD

Attention-deficit/hyperactivity disorder (ADHD) in adults is understudied, especially regarding neural mechanisms such as oscillatory control of attention sampling. We report an electroencephalography (EEG) study of such cortical mechanisms, in ADHD-diagnosed adults during administration of Test of Variables of Attention (TOVA), a gold-standard continuous performance test for ADHD that measures the ability to sustain attention and inhibit impulsivity. We recorded 53 adults (28 female, 25 male, aged 18-60), and 18 matched healthy controls, using 128-channel EEG. We analyzed sensor-space features established as neural correlates of attention: timing-sensitivity and phase-synchrony of response activations, and event-related (de)synchronization (ERS/D) of alpha and theta frequency band activity; in frontal and parietal scalp regions. TOVA test performance significantly distinguished ADHD adults from neurotypical controls, in commission errors, response time variability (RTV) and d' (response sensitivity). The ADHD group showed significantly weaker target-locked and responselocked amplitudes, that were strongly right-lateralized at the N2 wave, and weaker phase synchrony (longer reset poststimulus). They also manifested significantly less parietal prestimulus 8-Hz theta ERS, less frontal and parietal poststimulus 4-Hz theta ERS, and more frontal and parietal prestimulus alpha ERS during correct trials. These differences may reflect excessive modulation of endogenous activity by strong entrainment to stimulus (alpha), combined with deficient modulation by neural entrainment to task (theta), which in TOVA involves monitoring stimulus spatial location (not predicted occurrence onset which is regular and task-irrelevant). Building on the hypotheses of theta coding for relational structure and rhythmic attention sampling, our results suggest that ADHD adults have impaired attention sampling in relational categorization tasks.Peer reviewe

Computer Enabled Neuroplasticity Treatment : A Clinical Trial of a Novel Design for Neurofeedback Therapy in Adult ADHD

Background: We report a randomized controlled clinical trial of neurofeedback therapy intervention for ADHD/ADD in adults. We focus on internal mechanics of neurofeedback learning, to elucidate the primary role of cortical self-regulation in neurofeedback. We report initial results; more extensive analysis will follow. Methods: Trial has two phases: intervention and follow-up. The intervention consisted of neurofeedback treatment, including intake and outtake measurements, using a waiting-list control group. Treatment involved 40 h-long sessions 2-5 times per week. Training involved either theta/beta or sensorimotor-rhythm regimes, adapted by adding a novel "inverse-training" condition to promote self-regulation. Follow-up (ongoing) will consist of self-report and executive function tests. Setting: Intake and outtake measurements were conducted at University of Helsinki. Treatment was administered at partner clinic Mental Capital Care, Helsinki. Randomization: We randomly allocated half the sample then adaptively allocated the remainder to minimize baseline differences in prognostic variables. Blinding: Waiting-list control design meant trial was not blinded. Participants: Fifty-four adult Finnish participants (mean age 36 years; 29 females) were recruited after screening by psychiatric review. Forty-four had ADHD diagnoses, 10 had ADD. Measurements: Symptoms were assessed by computerized attention test (T.O.V.A.) and self-report scales, at intake and outtake. Performance during neurofeedback trials was recorded. Results: Participants were recruited and completed intake measurements during summer 2012, before assignment to treatment and control, September 2012. Outtake measurements ran April August 2013. After dropouts, 23 treatment and 21 waiting-list participants remained for analysis. Initial analysis showed that, compared to waiting-list control, neurofeedback promoted improvement of self-reported ADHD symptoms, but did not show transfer of learning to T.O.V.A. Comprehensive analysis will be reported elsewhere.Peer reviewe

Alpha and Theta Oscillations during Sustained Attention in Adults with Attention-Deficit Hyperactivity Disorder

Introduction: Attention-deficit hyperactivity disorder (ADHD) is among the most common childhood psychiatric disorders and is marked by persistent, age-inappropriate levels of inattention, hyperactivity and/or impulsivity. The present study examines cortical oscillations in adults diagnosed with ADHD/ADD during administration of T.O.V.A. (Test of Variables of Attention). T.O.V.A. is a continuous performance test (CPT) that measures the ability to sustain attention for a prolonged period of time. The motivation for the study is to contribute to the diagnostic picture of ADHD through the novel combination of T.O.V.A. with an EEG measurement. Parieto-occipital alpha and frontomedial theta are examined in particular as they have been linked to sustained attention as measured in CPTs. Methods: 53 adults diagnosed with ADHD/ADD and 18 healthy controls were recruited. Concomitant T.O.V.A. and EEG was measured. Oscillatory power in theta and alpha bands was compared between groups and between different behavioural conditions. Results & Conclusions: T.O.V.A. performance of healthy controls was more likely to be within normal limits as compared to ADHD/ADD diagnosed adults, and vice versa. There were moderate significant differences in commission errors, RT variability and d’ (response sensitivity) between groups. The control group tended to manifest higher theta synchronisation during correct inhibition trials. Given differences in behavioural performance, this result might be related to a higher sensitivity to task demands in the control group. However, there were no between-groups differences in frontomedial theta power and parietal or frontal alpha power. Further research should compare groups formed on the basis of not only diagnostic status but also of behavioural performance.Johdanto: Tarkkaavaisuus- ja ylivilkkaushäiriö (engl. Attention-deficit hyperactivity disorder, ADHD) on yksi yleisimmistä neuropsykologisista häiriöistä. Tämä tutkimus käsittelee ADHD diagnosoitujen aikuisten EEG oskillaatioita T.O.V.A. -testin (Test of Variables of Attention) aikana. T.O.V.A. on tarkkaavaisuuden pitkäjänteistä ylläpitämistä vaativa testi, jonka tarkoituksena on tunnistaa tarkkaavaisuus- ja ylivilkkaushäiriölle tyypillinen vastausprofiili. Parieto-okkipitaaliset alfa oskillaatiot ja frontomediaaliset theta oskillaatiot on aiemmin yhdistetty tarkkaavaisuuden pitkäjänteiseen ylläpitämiseen liittyvään kognitiiviseen kuormitukseen. Menetelmä: 53 ADHD-diagnosoitua aikuista ja 18 tervettä kontrollikoehenkilöä rekrytoitiin. Koehenkilöille tehtiin T.O.V.A.-testin aikana EEG-mittaus. Koehenkilöiden theta- ja alfa- oskillaatioita vertailtiin ryhmien sekä T.O.V.A:n eri osioiden välillä. Tulokset & Johtopäätökset: Kontrollien suoriutuminen oli keskimäärin lähempänä normaalia suoriutumista kuin ADHD aikuisten. Ryhmien suoriutumisessa oli merkitseviä eroja virhevastausten määrässä, vastausaikojen vaihtelevuudessa sekä vastausherkkyydessä (d’). Kontrolliryhmässä havaittiin enemmän theta-synkronisaatiota silloin kun koehenkilöt tehtävän ohjeistuksen mukaisesti pidättäytyivät vastaamasta ärsykkeeseen (engl. correct inhibition). Tämä havainto ja behavioraaliset tulokset saattavat viitata siihen, että kontrolliryhmä arvioi paremmin tehtävän kuormittavuutta. Ryhmien välillä ei havaittu eroja theta- ja alfa-oskillaatioiden voimakkuudessa. Tässä tutkimuksessa vertailtiin diagnoosin perusteella muodostettujen ryhmien keskiarvoja. Tulevien tutkimusten tulisi vertailla myös suoritutumisen mukaan muodostettuja ryhmiä