. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. SEASONAL PLASTICITY IN BEHAVIOR AND BRAIN 95 ^^^^itiM&. Figure 2. Diagram ot'a coronal cross-section of the hippocampal formation (HP, APH) in the labora- tory pigeon. The right side of the figure shows the Nissl-stained brain section; the left side of the figure shows the boundaries of brain regions. The hippocampus (HP) and area parahippocampalis (APH) are labeled. Adapted from Karten and Hodos( 1967). tion bouts. Most remarkably, the changes in dendritic structure occur within 2 h of a squirrel's arousal from torpor,
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. SEASONAL PLASTICITY IN BEHAVIOR AND BRAIN 95 ^^^^itiM&. Figure 2. Diagram ot'a coronal cross-section of the hippocampal formation (HP, APH) in the labora- tory pigeon. The right side of the figure shows the Nissl-stained brain section; the left side of the figure shows the boundaries of brain regions. The hippocampus (HP) and area parahippocampalis (APH) are labeled. Adapted from Karten and Hodos( 1967). tion bouts. Most remarkably, the changes in dendritic structure occur within 2 h of a squirrel's arousal from torpor, and it is suggested that such changes must there- fore occur repeatedly throughout hibernation, with cy- clic changes occurring with each bout of spontaneous ac- tivity (Popov and Bocharova, 1992; Popov ei a/.. 1992). Of course, it is possible that this remarkable process was occurring throughout the squirrel brain; other regions were not assessed in these studies. Future work should address this question, but nonetheless, such plasticity does exist in the hippocampus. This plasticity may well be hormonally mediated be- cause gonadal, thyroid, and adrenal hormones produce similar changes in the dendritic arbor of hippocampal pyramidal neurons in the laboratory rat (McEwen et ai, 1991). The hippocampus is, in fact, a remarkably plastic brain structure. As in the song nuclei of passerine birds, new neurons continue to be recruited in the granule layer of the dentate gyrus of the hippocampus in the adult lab- oratory rat (Altman and Bayer, 1990), and these new neurons make functional connections (Kaplan and Bell. 1983). But perhaps it is not a coincidence that such plas- ticity, rare in the adult brain, happens to be found in the hippocampus, a structure that plays such an important role in the neurobiology of learning. Seasonal changes in spatial behavior and hippocam- pus in mammals. Evidence suggests that seasonal pat- terns of spatial behavior are linked to seasonal changes in
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
