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Department of Clinical Medicine

Midway Evaluation - Maiken Kirkegaard Brix

Midway Evaluation for the Ph.D degree at the University of Bergen.

Main content

The Candidate is affiliated to the Department of Clinical Medicine. Principle supervisor - Mona Beyer.

 

Abstract

Background

A multimodal magnetic resonance (MR) imaging approach is used to get a better characterization of the Autism Spectrum Disorder (ASD). ASD includes a range of complex pervasive neurodevelopmental disorders defined clinically by impaired social interaction, communication difficulties (both verbal and non verbal), and by repetitive, restricted or stereotypic behaviour. Increasing evidence suggests that ASD may be associated with abnormalities in the glutamate and g-aminobutyric acid (GABA) system, also referred to as the excitatory/inhibitory (E/I) imbalance theory.

A particular focus in this PhD project has been the MR Spectroscopy (MRS) sequence MEGA-PRESS. MRS is a non-invasive method for measuring metabolites eg. in the brain, and the novel MEGA-PRESS technique allows for quantification of GABA. A GABA reproducibility study on healthy male volunteers validating the MEGA-PRESS method is therefore also included in the PhD project.

Methods

20 ASD boys and 27 typically developing (TD) age-matched controls are included. Exclusion criteria in both groups are braces, genetic abnormalities and prematurity. Epilepsy, autistic traits and other neuropsychiatric disorders are exclusion criteria in the TD group. The MRI protocol includes two spectroscopy sequences (PRESS and MEGA-PRESS) with voxel placement in the left Anterior Cingulate Cortex (ACC), a T1 sequence for anatomical imaging and positioning of the spectroscopy voxel and a fMRI sequence designed to examine “resistance to change”. Analyses of the spectroscopy data is performed using LCModel, the fMRI data is analysed with SPM12 and the anatomy data will be analysed with FreeSurfer software. SPSS is used on all statistics.

Results

Paper 1 (submitted)

Title: ”Brain MR Spectroscopy in Autism Spectrum Disorder –the GABA excitatory/inhibitory imbalance theory revisited”. Authors: Brix MK, Ersland L, Hugdahl K, Gruner R, Posserud MB, Hammar Å, Craven AR, Noeske R, Evans JC, Walker HB, Midtvedt T, Beyer MK.

Main findings: We did find a significant negative correlation in the ASD group between Autism Spectrum Screening Questionnaire (ASSQ) and GABA, which may imply that severity of symptoms in ASD is associated with differences in the level of GABA in the brain, supporting the E/I imbalance theory. However we did not find a significant difference between the two groups (ASD and TD) in GABA levels.

The fMRI and structural MR data and the data from the GABA reproducibility study are yet to be analysed.

 

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