| Summary: | 博士 === 國立清華大學 === 生醫工程與環境科學系 === 104 === Resting state functional magnetic resonance imaging (rs-fMRI) has received enormous attention since its discovery more than a decade ago. Rs-fMRI detects the intrinsic low-frequency fluctuations of brain and uncovers the brain connectivity termed resting state networks (RSNs). This technique has been employed on investigating several neuropsychological disorders including attention deficit and hyperactivity disorder (ADHD). However, the rs-fMRI study on ADHD animal model remains unexplored. Since animal model provides a beneficial pathway to discover the pathologies of diseases, we aim to investigate brain networks of an ADHD rodent model: spontaneously hypertensive rat (SHR). In this dissertation, rs-fMRI and diffusion MRI were utilized for exploring the brain networks of SHR rat.
In the first part, SHR and Wistar Kyoto rat (WKY) at 6 weeks old were compared. The default mode network (DMN), which is the most prominent RSN, was derived by using retrosplenial cortex as seed. Our results showed that the major DMN differences are the activities in caudate putamen and hippocampus region. Diffusion scalars also reported abnormality in these regions. Since the dysfunction of prefrontal striatal circuits has long been considered a correlate of ADHD, our findings could support that the striatal dysfunction in SHR rats is related to ADHD symptom.
In the second part, the developmental changes in brain networks were investigated. Animals from 6 to 10 weeks old underwent rs-fMRI and diffusion MRI experiments. The age-related reduction of DMN activity was identified in the caudate putamen and the medial prefrontal cortex of SHR rats. Furthermore, diffusion scalars reflect the microstructural differences between SHR and WKY rats at the same time. Our results suggest the importance of caudate putamen and medial prefrontal cortex in the development of ADHD research using SHR model.
In summary, the striatal area plays an important role in this ADHD rat model. In addition to the conventional behavior evidence on SHR rat, the network details in this dissertation offer an insight into brain function, suggesting the possibility of further ADHD research on rodent models through rs-fMRI techniques.
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