Abstract #0043

Anomalous relationship between sensorimotor GABA levels and cortical excitability in children with Attention-deficit/hyperactivity disorder

Ashley D Harris^1,2,3, David A Huddleston⁴, Paul S Horn⁴, Kim M Cecil⁵, Richard AE Edden^6,7, Donald L Gilbert⁴, Stewart H Mostofsky^8,9,10, and Nicolaas AJ Puts^6,7

¹Radiology, University of Calgary, Calgary, AB, Canada, ²Child and Adolescent Imaging Research Program, Alberta Children's Hospital Research Institute, University of Calgary, Calgary, AB, Canada, ³Hotchkiss Brain Institute, University of Calgary, Calgary, AB, Canada, ⁴Division of Pediatric Neurology, Cincinnati Children's Hospital Medical Center and University of Cincinnati, Cincinnati, OH, United States, ⁵Department of Radiology, Cincinnati Children's Hospital Medical Center and University of Cincinnati, Cincinnati, OH, United States, ⁶Russell H. Morgan Department of Radiology and Radiological Science, Johns Hopkins School of Medicine, Baltimore, MD, United States, ⁷F.M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Institute, Baltimore, MD, United States, ⁸Center forNeurocognitive and Imaging Research, Kennedy Krieger Institute, Baltimore, MD, United States, ⁹Department of Neurology, Johns Hopkins School of Medicine, Baltimore, MD, United States, ¹⁰Department of Behavioral Science and Psychiatry, Johns Hopkins School of Medicine, Baltimore, MD, United States

Reduced inhibition as shown though GABA-edited MRS and TMS measures have been suggested to underlie some of the symptomology of ADHD. In this study we apply GABA-MRS and single- and paired-pulse TMS in ADHD and typically developing cohorts to better understand altered inhibition in ADHD. We show that SICI approaches 1 with increasing GABA across both groups. Secondly, we show a convergence in SICI and single-pulse TMS responses with increasing GABA. Last, we show different factors modulate the TMS responses between ADHD and control suggesting there are additional differences in GABAergic inhibition between these two groups.

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