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Lynn Nadel
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Journal Articles
Publisher: Journals Gateway
Journal of Cognitive Neuroscience (2013) 25 (11): 1908–1925.
Published: 01 November 2013
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Representing an environment globally, in a coarse way, and locally, in a fine-grained way, are two fundamental aspects of how our brain interprets the world that surrounds us. The neural correlates of these representations have not been explicated in humans. In this study we used fMRI to investigate these correlates and to explore a possible functional segregation in the hippocampus and parietal cortex. We hypothesized that processing a coarse, global environmental representation engages anterior parts of these regions, whereas processing fine-grained, local environmental information engages posterior parts. Participants learned a virtual environment and then had to find their way during fMRI. After scanning, we assessed strategies used and representations stored. Activation in the hippocampal head (anterior) was related to the multiple distance and global direction judgments and to the use of a coarse, global environmental representation during navigation. Activation in the hippocampal tail (posterior) was related to both local and global direction judgments and to using strategies like number of turns. A structural shape analysis showed that the use of a coarse, global environmental representation was related to larger right hippocampal head volume and smaller right hippocampal tail volume. In the inferior parietal cortex, a similar functional segregation was observed, with global routes represented anteriorly and fine-grained route information such as number of turns represented posteriorly. In conclusion, moving from the anterior to the posterior hippocampus and inferior parietal cortex reflects a shift from processing coarse global environmental representations to processing fine-grained, local environmental representations.
Journal Articles
Publisher: Journals Gateway
Journal of Cognitive Neuroscience (2013) 25 (1): 22–28.
Published: 01 January 2013
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We discuss the question of differentiation along the anterior–posterior longitudinal axis of the hippocampus. Data from a recent fMRI study are reanalyzed to determine whether activations in these hippocampal regions are affected by the nature of the information being accessed during a scanning session in which participants thought about episodes from their lives. Retrieving detailed spatial relational information preferentially activated the posterior hippocampus, whereas retrieving information about locales (or contexts) preferentially activated the anterior hippocampus. These data support the view that there is functional differentiation along the longitudinal axis in humans that matches what has been seen in rats, namely, that the posterior (dorsal) hippocampus is crucial for precise spatial behavior, and the anterior (ventral) hippocampus is crucial for context coding.
Journal Articles
Publisher: Journals Gateway
Journal of Cognitive Neuroscience (1992) 4 (3): 179–188.
Published: 01 July 1992
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Evidence from a variety of domains converges on the view that there are multiple learning/memory systems, but there is no clear understanding of what these systems are, and why they should exist. I review an hypothesis about multiple memory systems postulated by O'Keefe and Nadel ( The hippocampus ac a Cognitive map , Oxford: Clarendon Press, 1978), in particular our assertions about the nature of two kinds of systems (the locale and taxon systems), and what differentiates them from each other. I concentrate on our assumption that systems differ in terms of the type of information they process, rather than in terms of the temporal duration over which they function. Our “content-driven” dichotomy is contrasted with several other current views, none of which appears to explain extant data, or provides clear predictions about when one or the other kind of system would be engaged. Finally, 1 briefly consider why such distinct systems might have evolved.
Journal Articles
Publisher: Journals Gateway
Journal of Cognitive Neuroscience (1991) 3 (2): 95–116.
Published: 01 April 1991
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As part of the general trend toward interdisciplinary research in recent years, a growing number of investigators have come to consider both cognitive and neuroscientific perspectives when theorizing about memory. Although such cognitive neuroscience analyses are a relatively recent development, the approach has precedents in earlier scientific thinking about memory. In this article we present a historical review of three major issues in memory research---consolidation processes, the nature of memory representations, and multiple memory systems. We discuss the nature of the relation between cognitive and neuroscientific approaches to each of these issues with respect to the distinction between collateral, complementary, and convergent relations (Schacter, 1986). Although some early investigators offered analyses that linked psychological and physiological perspectives, there is little historical evidence of systematic or sustained interdisciplinary research. However, more recent work, especially with respect to hypotheses about memory systems, suggests progress toward establishing programmatic interdisciplinary research.