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Title: Motor Cortex Excitation/Inhibition Imbalance in Young Adults With Autism Spectrum Disorder: A MRS-TMS Approach
Authors: Bernardino, Inês 
Dionísio, Ana 
Violante, Inês R. 
Monteiro, Raquel 
Castelo-Branco, Miguel 
Keywords: GABA; autism (ASD); glutamate; magnetic resonance spectroscopy; transcranial magnetic stimulation
Issue Date: 2022
Publisher: Frontiers
Project: info:eu-repo/grantAgreement/FCT/UID/4950/2020/PT/CIBIT 
info:eu-repo/grantAgreement/FCT/FARH/SFRH/BPD/101641/2014/PT/Neural correlates of inhibitory control in autism: from neurotransmitter neurobiology to physiological mechanisms and cognition 
info:eu-repo/grantAgreement/FCT/3599-PPCDT/DSAIPA/DS/0041/2020/PT/A clinical documentation system interfacing clinical and data scientist needs to address the COVID challenge 
Serial title, monograph or event: Frontiers in Psychiatry
Volume: 13
Abstract: Excitatory/inhibitory imbalance has been suggested as a neurobiological substrate of the cognitive symptomatology in Autism Spectrum Disorder (ASD). Studies using magnetic resonance spectroscopy (MRS) attempted to characterize GABA and Glutamate brain levels in ASD. However mixed findings have been reported. Here, we characterize both neurochemical and physiological aspects of GABA system in ASD by implementing a more comprehensive approach combining MRS and transcranial magnetic stimulation (TMS). A group of 16 young ASD adults and a group of 17 controls participated in this study. We employed one MRS session to assess motor cortex GABA+ and Glutamate+Glutamine (Glx) levels using MEGAPRESS and PRESS sequences, respectively. Additionally, a TMS experiment was implemented including paired-pulse (SICI, ICF and LICI), input-output curve and cortical silent period to probe cortical excitability. Our results showed a significantly increased Glx, with unchanged GABA+ levels in the ASD group compared with controls. Single TMS measures did not differ between groups, although exploratory within-group analysis showed impaired inhibition in SICI5ms, in ASD. Importantly, we observed a correlation between GABA levels and measures of the input-output TMS recruitment curve (slope and MEP amplitude) in the control group but not in ASD, as further demonstrated by direct between group comparisons. In this exploratory study, we found evidence of increased Glx levels which may contribute to ASD excitatory/inhibitory imbalance while highlighting the relevance of conducting further larger-scale studies to investigate the GABA system from complementary perspectives, using both MRS and TMS techniques.
ISSN: 1664-0640
DOI: 10.3389/fpsyt.2022.860448
Rights: openAccess
Appears in Collections:FMUC Medicina - Artigos em Revistas Internacionais
I&D ICNAS - Artigos em Revistas Internacionais
I&D CIBIT - Artigos em Revistas Internacionais

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