ABSTRACT
Abstract The limbic-reticular coupling theory suggests that the hippocampus and amygdala regulate such descending limbic structures as the mammillary bodies, septum, hypothalamus and epithalamus to regulate the ascending noradrenergic, serotonergic, dopaminergic and cholinergic systems, performing declarative memory consolidation and recall. Recent studies have revealed that, less sensitive to familiarity, the hippocampus functions via the fornix, mammillary bodies and hypothalamus for memory recall. Lesions to the thalamic nuclei were complicated with damage to adjacent fornix, stria medullaris and habenula, simultaneously destroying two kinds of structures respectively for familiarity and recall. Furthermore, the orbitofrontal cortex was shown to be clinically irrelevant for memory recall. Electrophysiologically, the hippocampus regulates the raphe nuclei in complex ways, and the hippocampal theta wave activates the dopaminergic cells in ventral tegmental area and cholinergic neurons in basal forebrain, while cholinergic-modulated theta-gamma coupling mediates cortical recall. These concurrent advances support the limbic-reticular coupling theory for elucidation of memory recall.
Resumo A teoria do acoplamento límbico-reticular sugere que o hipocampo e a amígdala regulam estruturas límbicas descendentes como os corpos mamilares, septum, hipotálamo e epitálamo para regular os sistemas ascendentes noradrenérgico, serotoninérgico, dopaminérgico e colinérgico, realizando a consolidação da memória declarativa e a recordação. Estudos recentes revelaram que, menos sensível à familiaridade, o hipocampo funcionava via fórnice, corpos mamilares e hipotálamo para a recordação da memória. Lesões aos núcleos talâmicos são complicadas com danos ao fórnice, estria medullaris e habenula adjacentes, destruindo simultaneamente dois tipos de estruturas, respectivamente, para familiaridade e recordação. Além disso, o córtex orbitofrontal mostrou-se clinicamente irrelevante para a recordação da memória. Eletrofisiologicamente, o hipocampo regula os núcleos da rafe de maneiras complexas, e a onda teta hipocampal ativa as células dopaminérgicas na área tegmentar ventral e os neurônios colinérgicos no prosencéfalo basal, enquanto que o acoplamento teta-gama colinergicamente modulado medeia a evocação cortical. Esses avanços concorrentes sugerem que a teoria do acoplamento límbico-reticular apropriada para a elucidação da recordação da memória.
Subject(s)
Memory/physiology , Mental Recall , Hippocampus , AmygdalaABSTRACT
Adult onset Leigh syndrome is a very rare neurodegenerative disorder of unknown cause. We report the evolution of the lesions on serial MRIs in a 38-year-old man with clinically diagnosed Leigh syndrome. We emphasize that the mammillary bodies can be involved during the disease course and that premortem diagnosis of Leigh syndrome is pos-sible, if a characteristic distribution of lesions can be demonstrated on MRI.
Subject(s)
Adult , Humans , Diagnosis , Leigh Disease , Magnetic Resonance Imaging , Mammillary Bodies , Neurodegenerative DiseasesABSTRACT
Nine adult rabbits, perfused with 10% formalin, were used in this experiment. Five of them were mounted on the stereotaxic apparatus according to the Sawyer's atlas. Brains were removed and made serial sections including thalamus and hippocampus. The neocortices of the other four rabbits were removed and the hippocampal formations were exposed. Serial sections of the hippocampus were made and stained alternately with Nissl's method and the silver impregnation method of Glees. The results could be summarized as follows.1. The hippocampus measured 28.00-36.00 mm in length, 6.00-8.50 mm in breadth and 2.68-3.39 mm in thickness. The total numbers of the pyramidal cells (CA_1-CA_4), the granular cells in the dentate gyrus and the basket cells were 7.36?10~6, 4.93?10~6, 2.40?10~5 respectively. The ratio of the total numbers among the pyramidal, granular and the basket cells was 30:20:1 approximately. The total number of the CA_1 pyramidal neurones was 4.11?10~6, and that of the CA_3 was 2.48?10~6. The ratio of the numbers of the CA_1 and CA_3 neurones was 1.66:1.2. The arrangements of the granular cells in the dentate gyrus and the apical dentrites of the CA_1 neurones were rather regular and possessed a typical array-like structure.3. The total numbers of the fibers in the column fornix (FN)and the mamillothalamic tract (MT) were 83700 and 58740 respectively. MT:FN=1:1.42. The total number of the neurones in the mamillary nucleus was 113500, and that of the anterior thalamic nucleus was 165600. The ratio of the neurones between these two nuclei was 1:1.46.According to the results mentioned above, the functional significance of the characteristic structure of the hippocampus was also discussed.