Functional and structural neuroimaging correlates of selective retrograde amnesia: A case study with MRI and PET
The neuroanatomical and neurophysiological systems underlying episodic memory functioning were assessed in a case of retrograde amnesia without anterograde amnesia following traumatic brain injury (TBI). MRI showed evidence of a focal right inferior frontal injury affecting both cortical tissue and frontal-subcortical pathways, including the uncinate fasciculus, a frontal-temporal band of fibers previously hypothesized to be involved in retrieval of personal episodic memories. On an H215O PET activation paradigm that reliably elicits right frontal activation on retrieval and left frontal activation on encoding, the index case did not show increased right frontal activation on retrieval. The normal pattern of right frontal activation was observed in a matched TBI control subject without retrograde amnesia. Both the index case and the matched control showed additional posterior activations which suggested TBI-related disinhibition, compensation, or both. Taken together, the neuroimaging findings converge to suggest a right frontal-temporal system mediating retrieval of episodic memories.
Levine, B; Cabeza, R; Black, S; Sinden, M; Leibovitch, F; Toth, JP; Tulving, E; Stuss, DT
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