Decoding the human memory network: a brain mapping approach to spatial navigation
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Abstract
The resection of Patient H.M.’s bilateral medial temporal lobe (MTL) structures in 1957 produced a deficit in encoding new episodic memories, leaving short-term memory, non-declarative memory, and other cognitive functions intact15. The discovery of the relationship between MTL damage and the development of anterograde amnesia has provided evidence that these areas are responsible for memory processes. Animal models have also supported the hypothesis that these areas play a major role in memory function, using lesion methods that have replicated H.M.’s bilateral damage to the hippocampus and the surrounding MTL cortices20. Although animal models of memory research have provided ample evidence in support of this hypothesis, the development of human brain mapping techniques, such as functional magnetic resonance imaging (fMRI), positron emission tomography (PET), diffusion tensor imaging (DTI), magnetoencephalography (MEG) and transcranial magnetic stimulation (TMS), allow researchers to apply the findings from animal studies and Patient H.M.’s case to investigate both spatial and temporal aspects of the neural network underlying the human memory system, and more specifically, the role of this memory network in spatial navigation.