Studies On The Clinical And Functional Magnetic Resonance Imaging Of The Marginal Division Of Human Neostriatum

The marginal division of the striatum (MrD) is a newly identified structure at the caudal most edge of the neostriatum, near the rostral border of the globus pallidus, in the brain of the rat, discovered by Shu et al in 1988. The MrD is distinguished from the rest of the striatum by consisting of spindle-shaped neurons, special connections, and intensely expressed neurotransmitters in the fibers, terminals, and neuronal somata. The MrD was also identified in the brains of cat and monkey. It was proved to be involved in learning and memory function of rat brain by a double blinded Y-maze behavioral test and c-fos expression experiment. However, whether there is a MrD in human striatum is still undiscovered, does it have the function of learning and memory?How about its structure and shape? Are there involved in learning and memory of human being? For probing into these questions, some measures had been taken. Firstly, the existence of the MrD in human brain were proved and demonstrated with Nissl stain, and the abundant blood supplies in this area were also showed by the observiations of the autopsy specimens, the films of digital subtruction angiography(DSA),MRIand MRA. Secondly, the involvement of the human MrD in learning and memory was investigated with a functional magnetic resonance imaging (fMRI) experiment. It is proved that the MrD was involved in visual digital working memory, spatial working memory,instantaneous spatial memory, instantaneous digital memory,and calculation in human. Then, the clinical cases with MrD lesions were investigated, combining MRI and cognitive function analyses with Mini-Mental StateExamination (MMSE), to explore in clinic whether the MrD is involved in the cognitive function of human brain. The learning and memory function of the MrD was then verified by clinic investigations.Chapter I Study on the structure of human MrDTo prove the existence of the MrD in the human striatum, the cytoarchitecture in the human striatum were studied using Nissl stain . The results of Nissl stained showed that there is a distinct fusiform cell zone between the putamen and globus pallidus of the human striatum. The long axes of these neurons were running dorsoventrally, parallelly to the medial border of the putamen. The results demonstrated the existence of the MrD in the striatum of human brain, as well as in the rat, cat and monkey brains. The shape of the neurons in human MrD are also similar to the rat, cat and monkey MrD. The MrD is much thicker in human than other mammalians, which suggested that the MrD is a developing structure in the evolution. The abundant blood supplies in the human striatum were also found by observing the autopsy specimens and the films of digital subtruction angiography(DSA),MRI,MRA.It can be inferred that the MrD might have important function in human brain. Then the function of human MrD was investigated in healthy volunteers using fMRI technique.Chapter II Study on the fMRI of human MrDFMRI technique was used to indentify whether there were activation in Mrd of the human brain during the performance of learning and memory tasks. Healthy volunteers were instructed to undertake the tasks of visual digital working memory, spatial working memory, instantaneous spatial memory, instantaneous digital memory,and calculation, monitored by fMRI. The activation of brain regions was observed during the performance of different tasks. Highly active areas were observed in bilateral prefrontal cortex with left sided predominance and left MrD during performance of the visual working memory task, but other parts of the striatum were not excited. The prefrontal cortex and the MrD were not obviously activated during performance of the control test of non-working memory. In addition, the Mrdcooperated with the other areas of brain to participate in the tasks of spatial working memory and calculation,but not in the tasks of instantaneous spatial memory and instantaneous digital memory. The results suggested that the MrD was involved in visual digital working memory task as well as the prefrontal cortex in human brain. The MrD is probably a subcortical memory center. Then clinic cases with MrD lesions were investigated, combining MRI and cognitive function analyses, to confirm the learning and memory function of the MrD in human brain. Chapter III Clinic observation on the cognitive function of human MrDTo investigate the relationship between the injury of marginal division of the striatum(MrD) and the cognitive impairment,50 cases with the injury of marginal division of striatum were examined rountinely by MRI. Cognitive tests of each case were performed and compared with the findings of MRI. Simultaneously, the features of MRI and the degree of cognitive impairment between 50 cases with the injury of MrD and 15 cases with Alzheimer disease were compared. The results showed that (1) The MMSE scores of the cases were ranged from 6 to 25, and averaged to 215 The main cognitive impairments were memory and calculation.(2) There were no significant difference of the cognitive impairment between the injury of marginal division and the injury accompanied with the other areas of striatum. The results indicated that the injury of MrD may cause the cognitive impairment. The MrD is the major part of the striatum in human brain, which is related to the cognitive function. Finally,two cases with the decending of memory after the injury in the marginal division of neostriatum(MrD) were reported.The case one is a young male.His memory was impaired after truma.The injury in the left marginal division of neostriatum(MrD) was revealed by MRI. The another case is an old female.Her memory was impaired after radiation therapy. MRI examination revealed that there were abnormal signals in the bilateral marginal division of neostriatum(MrD) .The results of tests showed that the score of the first patient' IQ was only 78 and the main manifestion was the impairment of his memory. The fMRI results showed that the MrD were not activated as normal volunteers. The score of another case MMSE test was 6.These results demonstrated that the injury in the marginal division of neostriatum(MrD) can cause the decending of patient' memory.