Study of functional magnetic resonance imaging (fMRI) in children and adolescents with specific learning disorder (dyslexia) : Review Study

Backgrounds: Dyslexia is a type of Specific Learning Disorder (SLD) with neurobiological origin with difficulties in accurate and/or fluent word recognition, poor spelling and decoding abilitiesDyslexia is perhaps the most common neurobehavioral disorder affecting children with prevalence ranging from ۵ to ۱۷.۵ percent.The impaired reading in dyslexia is associated with inability to process the sensory input that enters the nervous system. fMRI has emerged as a potential source in understanding the neurobiology and to identify the brain basis of sensory stimuli processed in dyslexic patientsn Application of modern techniques in fMRI and analysis of fMRI data have highlighted the importance of coordinated processing across functional networks of distinct brain. Methods :In this review study, in order to find appropriate papers related to Study of fMRI in children with learning disorder , a comprehensive search of valid English scientific databases such as: PubMed, Google scholar, Scopus in the years ۲۰۱۵-۲۰۲۳ with a combination of keywords, Dyslexia, fMRI, functional connectivity were performed. Exclusion criteria were studies out of the Imaging modalities other than fMRI, Patients other than children and irrelevant studies of the subject. From the total number of papers obtained, papers were chosen.Results :As compared to control group, the participants with dyslexia show phonological decoding problem. During picture task, the participants with dyslexia use more areas of brain involve in recalling the memory events while during semantic tasks processing the occipito-temporal (fusiform) gyrus was less activated when in contrast to control. Findings showed both positive and negative Resting-state functional connectivity(RSFC) behaviour relationships that diverged across different reading subskills. Positive relationships included increasing RSFC among left dorsal and anterior regions with increasing decoding proficiency, and increasing RSFC between the left thalamus and right fusiform gyrus with increasing sight word reading, RAN, and reading comprehension abilities. In contrast, negative relationships suggested greater functional segregation of attentional and reading networks with improved performance on RAN, decoding, and reading comprehension tasks.Conclusion :A review of these studies shows that participants with dyslexia fail to use normal brain regions specialized in language processing, but rather use different areas.Importantly, the results suggest that although reading subskills rely to some extent on shared functional networks, there are also distinct functional connections supporting different components of reading ability in children.

Keywords:

fMRI , dyslexia , SLD