![]() ![]() When these levels of organization are superimposed, a new model of hippocampal long-axis organization emerges: gradients with discrete domains, the latter dividing the hippocampus into (at least) three portions along the long axis. Hippocampal involvement in unconditioned fear responses is limited to the ventral one-third. Hippocampal intrinsic anatomical connectivity, as well as electrophysiological measures of coherence, show abrupt division from the ventral (anterior) one-third to dorsal (posterior) two-thirds of the hippocampus. ![]() The relative size of spatial representation by place cells in the rat hippocampus gradually increases from dorsal to ventral.īy contrast, rodent gene expression studies demonstrate multiple long-axis functional domains with sharply demarcated borders: at least nine in CA3 and three in CA1 and the dentate gyrus. There is evidence for two types of long-axis organization: gradients and discrete transitions.Īnatomical studies in rodents and primates show that hippocampal extrinsic connectivity is organized as smooth topographical gradients. The currently accepted model of a dorsal–ventral (posterior–anterior) dichotomy of hippocampal function requires revision. ![]()
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