Interactions of the hippocampus and non-hippocampal long-term memory systems during learning, remembering, and over time

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Sparks, Fraser T
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Lethbridge, Alta. : University of Lethbridge, Dept. of Neuroscience, c2012
The hippocampus and non-hippocampal long-term memory systems each have the capacity to learn and express contextual fear memory. How these systems interact during learning and remembering revolves around hippocampal mediated interference, where the hippocampus dominates for both the acquisition and expression of long-term memory. Hippocampal interference during learning can be overcome by modifying learning parameters such that learning is distributed across multiple independent sessions. The standard view of the role of the hippocampus in long-term memory retrieval is that it is temporally limited, where recently acquired memory is dependent on hippocampal function though as a memory ages, dependency is transferred to other memory systems by a process called systems consolidation. Distributed training demonstrates that learning parameters create a memory that is resistant to hippocampal damage. We find little evidence to support temporally based systems consolidation, and present data that supports the view that if the hippocampus is initially involved in learning a memory, it will always be necessary for accurate retrieval of that memory. A critical assessment of the rat literature revealed that initial memory strength, and/or lesion techniques might be responsible for the few studies that report temporally graded retrograde amnesia using contextual fear conditioning. Our experiments designed to directly test these possibilities resulted in flat gradients, providing further evidence that the hippocampus plays a permanent role in long-term memory retrieval. We propose and assess alternatives to the standard model and conclude that a dual store model is most parsimonious within the presented experiments and related literature. Interactions of the hippocampus and non-hippocampal systems take place at the time of learning and remembering, and are persistent over time.
xvi, 161 leaves : ill. (some col.) ; 29 cm
Hippocampus (Brain) -- Research , Long-term memory -- Research , Memory -- Physiological aspects -- Research , Rats as laboratory animals