الفهرس 
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Abstract
Introduction : The reward system is a complex neural network. It plays a vital role in motivation and decision-making. During early development, the reward system undergoes substantial growth, with notable increases in the volume of key regions such as the prefrontal cortex, and amygdala with a peak in volume typically observed during early adolescence followed by a gradual decline. These changes are believed to reflect the maturation of neural connections, which contribute to enhanced reward processing and decision-making abilities. Psychiatric disorders can affect the reward system and its functioning. Aim of the work : Throw light on the volumetric changes of the reward system and its tracts in the normal human brain across childhood and adolescence. Subjects and methods : Sixty Egyptian healthy volunteers of both sexes aging between 6–21 years. The chosen subjects were classified into three age groups : group I (childhood group) : including 24 people aged between 6–10 years old. group II (early adolescence group) : included 19 Persons aged between 11–15 years old. group III (late adolescence group) : included 17 people aged between 16–21 years old. The study was done at the MRI scanning unit at Radiology Department, Tanta University Hospital. The components of the reward system that were studied included subcortical areas (thalamus, putamen, caudate, hippocampus, and amygdala) and cortical areas (Medial prefrontal cortex(mPFC), dorsolateral prefrontal cortex (dlPFC), Anterior cingulate cortex (ACC) and Insular cortex). 3D T1 sequence was performed with slice thickness 0.5 mm. The brain images were transferred to a personal computer (PC) workstation, where the slicer 5.0.2 software was used to provide reliable morphometric measurements of structures of interest. Also, the measurements of the fraction anisotropy (FA) of the medial forebrain bundle and the cingulum bundle were done using DTI 40, 3D T1 weighted. Data were analyzed by independent t-test, ANOVA, and regression analysis. Results : The mean values of the caudate and hippocampus corrected volumes in each group revealed Right asymmetry. Total corrected thalamic, putamen and caudate volumes showed that there was a highly significant decrease (p < 0.001) across all groups. Regarding the total corrected hippocampus and amygdala volumes there were a highly significant increase (p < 0.001) in group II as compared with group I, followed by a highly significant decrease (p < 0.001) in group III. The total corrected mPFC and dlPFC volumes showed a highly significant increase (p < 0.001) in group II as compared with group I, followed by a highly significant decrease (p < 0.001) in group III. On the other hand, the total corrected ACC and insula volumes showed a highly significant decrease (p < 0.001) across all groups. Moreover, the fraction anisotropy (FA) of medial forebrain bundle and cingulum bundle increased across all groups as age increased.