ebook_ADHD2019

The World Federation of ADHD Guide 33 an auditory attention task in adults with ADHD and controls. ADHD was associa- ted with a greater phase coherence in the beta (14-30Hz) and gamma frequency (30-56Hz) range in attend and no-attend conditions compared to controls. Sti- mulant medication attenuated these differences but did not fully eliminate them. These results suggest that aberrant bottom-up processing may compromise execu- tive resources in ADHD. 108 PROTON MAGNETIC RESONANCE SPECTROSCOPY Proton magnetic resonance spectroscopy (MRS) is a non-invasive method allowing for in vivo quantification of several neurometabolites in small volumes of the brain. MRS studies in ADHD and other neurodevelopmental disorders as autism and obsessive compulsive disorder (OCD) are limited by small sample sizes and varying methodology. Nevertheless, some consistent findings were identified in a systematic review: 25 1. possible increased Glx (which is a combination of com- bination of Glu, glutamine and GABA) signal in the striatum across ADHD, OCD and autism; 2. increased Glx in the anterior cingulate cortex (ACC) in children and adolescents with ADHD and autism, and 3. decreased Glx in the ACC in adults with ADHD and with autism. This suggests neurodevelopmental changes in fronto-striatal glutamatergic circuits across the lifespan. RADIOTRACER IMAGING Radiotracer techniques such as positron emission tomography (PET) and single photon emission computed tomography (SPECT) can provide more direct evidence of altered dopamine binding patterns in the striatum of patients with ADHD. A meta-analysis of SPECT and PET studies investigating striatal dopamine transpor- ter density in individuals with ADHD and matched healthy comparison subjects found that the striatal dopamine transporter density was 14% higher on average in the ADHD group than in the controls. 12 However, there was marked heterogeneity across studies, and density was higher in patients with previous medication exposure and lower in medication-naive patients. Thus, striatal dopamine transporter density in ADHD appears to depend on previous psychostimulant exposure, with lower density in drug-naive subjects and higher density in previously medicated patients. SUMMARYAND CONCLUSION ADHD is a highly heritable, multifactorial disorder, in which genetic factors – of- ten in combination with environmental factors – form risk factors for disease onset.