Biomedical subjects

Adam R Clarke

Publications and source records attributed to Adam R Clarke.

44 records · Page 3Linked to original sources

PubMed2002

EEG differences between good and poor responders to methylphenidate and dexamphetamine in children with attention-deficit/hyperactivity disorder.

OBJECTIVES: This series of studies investigated (1) electroencephalographic (EEG) differences between good and poor responders to methylphenidate, (2) EEG differences between good and poor responders to dexamphetamine, and (3) differences in the EEGs of good responders to methylphenidate versus dexamphetamine, within samples of children with the combined type of attention-deficit/hyperactivity disorder (ADHD). METHODS: Twenty good and 20 poor responders to each of methylphenidate and dexamphetamine, based on the results of a continuous performance task, and 20 age-matched control subjects, participated in this study. EEG was recorded from 21 sites during an eyes-closed resting condition and Fourier transformed to provide estimates for total power, and absolute and relative power in the delta, theta, alpha and beta bands, and for the theta/alpha and theta/beta ratios. RESULTS: EEG differences were found between the good and poor responders to each medication. Good responders to methylphenidate had EEG profiles that suggested that they were more cortically hypoaroused than poor responders. In contrast, the good responders to dexamphetamine appeared to be more maturationally lagged than the poor responders. The two good-responder groups had EEG profiles which suggested that there were two different underlying central nervous system (CNS) dysfunctions. CONCLUSIONS: Children with the combined type of ADHD do not constitute a homogeneous clinical group, as different types of CNS dysfunction are present within this population. These results also indicate the need for medication testing to be undertaken before a child is prescribed stimulant medication for ADHD.

Attention Deficit Disorder with Hyperactivity↗

PubMed2002

EEG coherence in attention-deficit/hyperactivity disorder: a comparative study of two DSM-IV types.

OBJECTIVES: This study investigated differences in intrahemispheric and interhemispheric electroencephalographic (EEG) coherences between attention-deficit/hyperactivity disorder (ADHD) and control children, and between children with the Combined (ADHDcom) and Inattentive (ADHDin) types of ADHD. METHODS: Three age- and sex-matched groups of 40 children, aged 8-12 years, diagnosed with ADHDcom, ADHDin, and normal control children, participated in this study. EEG was recorded from 21 sites during an eyes-closed resting condition and Fourier transformed. Wave-shape coherence was calculated for 8 intrahemispheric electrode pairs (4 in each hemisphere), and 8 interhemispheric electrode pairs, within each of the delta, theta, alpha and beta bands. RESULTS: At shorter inter-electrode distances, ADHD children had elevated intrahemispheric coherences in the theta band and reduced lateral differences in the theta and alpha bands. At longer inter-electrode distances, ADHD children had lower intrahemispheric alpha coherences than controls. Frontally, ADHD children had interhemispheric coherences elevated in the delta and theta bands, and reduced in the alpha band. An alpha coherence reduction in temporal regions, and a theta coherence enhancement in central/parietal/occipital regions, were also apparent. ADHDcom had greater intrahemispheric theta and beta coherences than ADHDin. Frontally, ADHDcom had higher levels of interhemispheric coherences than ADHDin for the delta and theta bands. In central/parietal/occipital regions, beta coherences were elevated in ADHDcom. CONCLUSIONS: EEG coherences suggest reduced cortical differentiation and specialisation in ADHD, particularly in cortico-cortical circuits involving theta activity. Generally, ADHDcom children displayed greater anomalies than ADHDin children.

Analysis of Variance↗

PubMed2002

EEG evidence for a new conceptualisation of attention deficit hyperactivity disorder.

OBJECTIVES: This study investigated the presence of electroencephalographic (EEG) clusters within a sample of children with the inattentive type of attention-deficit/hyperactivity disorder (ADHD). METHODS: Subjects consisted of 100 boys with ADHD and 40 age-matched controls. EEG was recorded from 21 sites during an eyes-closed resting condition and Fourier transformed to provide estimates for total power, and relative power in the delta, theta, alpha and beta bands. Factor analysis was used to group sites into 3 regions; frontal, central and posterior. These data were subjected to cluster analysis. RESULTS: Two distinct EEG clusters of children with the inattentive type of ADHD were found. These were characterised by (a) increased high-amplitude theta with deficiencies of delta and beta activities, and (b) increased slow wave and deficiencies of fast wave activity. CONCLUSIONS: These two subtypes are independent of current diagnostic categories, and consist of a cortically hypoaroused group and a group typified by a maturational lag in central nervous system (CNS) development. These results support a re-conceptualisation of ADHD based on the CNS abnormality underlying the disorder rather than the behavioural profile of the child. This has the potential to add a level of predictive validity, which is currently lacking in the present diagnostic systems.

Adolescent↗

PubMed2002

EEG differences between good and poor responders to methylphenidate in boys with the inattentive type of attention-deficit/hyperactivity disorder.

OBJECTIVES: This study investigated electroencephalographic (EEG) differences between good and poor responders to methylphenidate in boys with the Inattentive type of Attention-Deficit/Hyperactivity Disorder (ADHD). METHODS: Twenty good and 15 poor responders to methylphenidate, based on the results of a continuous performance task, and 35 age- and sex-matched control subjects, participated in this study. EEG was recorded from 21 sites during an eyes-closed resting condition and Fourier transformed to provide estimates for total power, and absolute and relative power in the delta, theta, alpha and beta bands, and for the theta/alpha and theta/beta ratios. RESULTS: EEG differences were found between the ADHD children and controls which were compatible with previous literature on the Inattentive type. Differences were also found between the good and poor responders to methylphenidate. CONCLUSIONS: Good responders had EEG profiles that suggested that they were more cortically hypoaroused than poor responders.

Adolescent↗

PubMed2002

Acute mobile phone operation affects neural function in humans.

OBJECTIVES: Mobile phones (MP) are used extensively and yet little is known about the effects they may have on human physiology. There have been conflicting reports regarding the relation between MP use and the electroencephalogram (EEG). The present study suggests that this conflict may be due to methodological differences such as exposure durations, and tests whether exposure to an active MP affects EEG as a function of time. METHODS: Twenty-four subjects participated in a single-blind fully counterbalanced cross-over design, where both resting EEG and phase-locked neural responses to auditory stimuli were measured while a MP was either operating or turned off. RESULTS: MP exposure altered resting EEG, decreasing 1-4 Hz activity (right hemisphere sites), and increasing 8-12 Hz activity as a function of exposure duration (midline posterior sites). MP exposure also altered early phase-locked neural responses, attenuating the normal response decrement over time in the 4-8 Hz band, decreasing the response in the 1230 Hz band globally and as a function of time, and increasing midline frontal and lateral posterior responses in the 30-45 Hz band. CONCLUSIONS: Active MPs affect neural function in humans and do so as a function of exposure duration. The temporal nature of this effect may contribute to the lack of consistent results reported in the literature.

Adult↗

PubMed2002

Evidence-based practice for young people who self harm: can it be sustained and does it improve outcomes?

In 1998-1999, two Area Health Services in NSW conducted a project to implement evidence-based service enhancements for the clinical management of young people who present with Deliberate Self Harm (DSH) behaviour. The present study examined what structures and procedures were required to implement and sustain evidence-based practice in different health care settings for patients with DSH behaviour. Service provision was assessed at three points during the initial project to assess the degree of change that occurred, and 9 months after the completion of the project to allow an assessment of sustainability of the service provision. We examined staff perceptions of the importance of education, management directives, policy and procedure changes, and cultural/attitudinal changes, in implementing clinical best practice. Results indicated that support from both service management and clinical staff is necessary for successful implementation of service enhancements. High levels of staff education and policy development were also associated with high levels of service performance. The best sustained enhancements were those that were developed by the services themselves.

Adolescent↗

PubMed2002

Can the Q Link Ally, a form of Sympathetic Resonance Technology (SRT), attenuate acute mobile phone-related changes to neural function?

OBJECTIVES: Exposure to active mobile phones (MP) has been shown to affect human neural function as shown by the electroencephalogram (EEG). Although it has not been determined whether such effects are harmful, a number of devices have been developed that attempt to minimize these MP-related effects. One such device, the Q Link Ally (QL; Clarus Products, International, L.L.C., San Rafael, CA), is argued to affect the human organism in such a way as to attenuate the effect of MPs. The present pilot study was designed to determine whether there is any indication that QL does alter MP-related effects on the human EEG. DESIGN: Twenty-four (24) subjects participated in a single-blind, fully counterbalanced crossover design in which subjects' resting EEG and phase-locked neural responses to auditory stimuli were assessed under conditions of either active MP or active MP plus QL. RESULTS: The addition of QL to the MP condition increased resting EEG in the gamma range and did so as a function of exposure duration, and it attenuated MP-related effects in the delta and alpha range (at trend-level). The addition of the QL also affected phase-locked neural responses, with a laterality reversal in the alpha range and an alteration to changes over time in the delta range, a reduction of the MP-related beta decrease over time at fronto-posterior sites, and a global reduction in the gamma range that increased as a function of exposure duration. No unambiguous relations were found between these changes and either performance or psychologic state. CONCLUSIONS: This pilot study suggests that the addition of the QL to active MP-exposure does affect neural function in humans, altering both resting EEG patterns and the evoked neural response to auditory stimuli, and that there is a tendency for some MP-related changes to the EEG to be attenuated by the QL.

Acoustic Stimulation↗

PubMedDate not supplied

EEG analysis of children with attention-deficit/hyperactivity disorder and comorbid reading disabilities.

This study investigated electroencephalographic differences between two groups of children with attention-deficit/hyperactivity disorder, combined type, with reading disabilities (ADHD + RD) or without (ADHD) and typical control participants. Twenty participants were included in each group. All participants were between the ages of 8 and 12 years, and groups were matched on age and gender. The electroencephalographic (EEG) was recorded during an eyes-closed resting condition from 21 monopolar derivations, which were clustered into nine regions for analysis. The EEGs were Fourier-transformed to provide absolute and relative power estimates for the delta, theta, alpha, and beta bands. Ratio coefficients were also calculated for the theta/alpha and theta/beta ratios. Compared with controls, the clinical groups demonstrated the increased slow-wave and reduced fast-wave activity commonly reported in the ADHD literature. The ADHD + RD group had more relative theta, less relative alpha, and a higher theta/alpha ratio than the ADHD group. A number of hemispheric differences were also found in the delta and alpha bands. These results suggested that some of the EEG divergences found in the ADHD + RD group represent an electrophysiological component associated with the reading disability that is independent of the EEG divergences found in ADHD.

Attention Deficit Disorder with Hyperactivity↗