Hippocampus dentate gyrus

The major distant afferents to the LC arrive from the brainstem (nucleus paragigantocellularis, PGI) and telencephalon (central nucleus of amygdala, CEA, and prefrontal cortex, PFC). The efferents of the LC innervate literally all areas of the central neural system (CNS). The majority of the fibers, however, project to the hippocampus, dentate gyrus (DG), prefrontal cortex (PFC) and basolateral nucleus of amygdala (BLA) (Bouret and Sara 2005 Kandel et al., 2000 Kieman and Barr 1998). 

Hippocampus Hippocampus dentate gyrus Thalamus Cerebellum Cingulate gyrus Temporal cortex Parietal cortex Hippocampus Frontal cortex Medial temporal lobe... 

In the rabbit brain, the Nadi (a-naphthol, dimethyl-p-phenylenediamine) reaction showed marked activity of cytochrome oxidase in the caudate nucleus, the putamen, the anterior nucleus of the thalamus, the optic tectum, the interpeduncular nucleus. Golfs and Burdach s nuclei, and the inferior ohvary nucleus (Shimizu et al. 1957). A moderate reaction was seen in the neocortex, hippocampus, dentate gyrus, substantia nigra, cerebellar cortex and the nuclei of the cranial nerves. 

In that and subsequent studies (Kosofsky 1985 Blue et al. 1988a), a distinct laminar pattern of innervation was found in somatosensory cortex, and a quite different pattern in the cingulate cortex, hippocampus, and dentate gyrus, where there are distinct bands of highly varicose axons. In the primate, the 5-HT innervation of cerebral cortex is denser and more highly differentiated among different architectonic and functional areas (Kosofsky et al. 1984 Morrison et al. 1982 Morrison and Foote 1986 Wilson and Molliver 1986 Wilson et al. 1989). For example, marked differences in the density and distribution of 5-HT axons are found in the macaque on either side of the central sulcus, in primary motor and somatosensory cortex while... 

CA3 pyramidal neurons receive the mossy fiber input from the granule neurons of the dentate gyrus. This connection is part of the 3-cell circuit of the hippocampus that is believed to be involved in learning and memory. 

The proposed neurogenesis-memory clearance hypothesis is attractive because addition and removal of adult-born neurons in local network architecture could gradually destabilize the stored memory traces. Also, adult-generated neurons within the dentate gyrus, the upstream location in the hippocampus, potentially can amplify the destabilization effects. Coincidently, these newborn neurons are short-lived, typically with a life-span of three weeks in rodents [40], which seems to correlate well with the duration of hippocampal dependence of declarative memories. 

Figure 18.7 Distribution of iron in human brain. GP, globus pallidus SN, substantia nigra IPN, interpeduncular nucleus TH, thalamus DG, dentate gyrus RN, red nucleus CC, cerebral cortex HIPP, hippocampus CER, cerebellum FC, frontal cortex. (From Crichton and Ward, 2006. Reproduced with permission from John Wiley Sons., Inc.)...

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