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Neuroimage Clin. 2016 Jan 15;11:158-166. doi: 10.1016/j.nicl.2016.01.008. eCollection 2016.

Prefrontal contributions to relational encoding in amnestic mild cognitive impairment.

Author information

1
Department of Psychology, The University of North Carolina, Chapel Hill, NC, United States.
2
Department of Psychology and the Centre for Brain Research, The University of Auckland, Auckland, New Zealand.
3
Department of Neurology, The University of North Carolina, Chapel Hill, NC, United States.
4
Joseph & Kathleen Bryan Alzheimer's Disease Research Center, Duke University Medical Center, Durham, NC, United States; Division of Neurology, Duke University Medical Center, Durham, NC, United States.
5
Joseph & Kathleen Bryan Alzheimer's Disease Research Center, Duke University Medical Center, Durham, NC, United States; Department of Psychiatry & Behavioral Sciences, Duke University Medical Center, Durham, NC, United States.
6
Joseph & Kathleen Bryan Alzheimer's Disease Research Center, Duke University Medical Center, Durham, NC, United States; Division of Neurology, Duke University Medical Center, Durham, NC, United States; Department of Psychiatry & Behavioral Sciences, Duke University Medical Center, Durham, NC, United States.
7
Department of Psychology, The University of North Carolina, Chapel Hill, NC, United States; Biomedical Research Imaging Center, The University of North Carolina, Chapel Hill, NC, United States. Electronic address: kgio@unc.edu.

Abstract

Relational memory declines are well documented as an early marker for amnestic mild cognitive impairment (aMCI). Episodic memory formation relies on relational processing supported by two mnemonic mechanisms, generation and binding. Neuroimaging studies using functional magnetic resonance imaging (fMRI) have primarily focused on binding deficits which are thought to be mediated by medial temporal lobe dysfunction. In this study, prefrontal contributions to relational encoding were also investigated using fMRI by parametrically manipulating generation demands during the encoding of word triads. Participants diagnosed with aMCI and healthy control subjects encoded word triads consisting of a category word with either, zero, one, or two semantically related exemplars. As the need to generate increased (i.e., two- to one- to zero-link triads), both groups recruited a core set of regions associated with the encoding of word triads including the parahippocampal gyrus, superior temporal gyrus, and superior parietal lobule. Participants diagnosed with aMCI also parametrically recruited several frontal regions including the inferior frontal gyrus and middle frontal gyrus as the need to generate increased, whereas the control participants did not show this modulation. While there is some functional overlap in regions recruited by generation demands between the groups, the recruitment of frontal regions in the aMCI participants coincides with worse memory performance, likely representing a form of neural inefficiency associated with Alzheimer's disease.

KEYWORDS:

Aging; Functional MRI; Mild cognitive impairment; Relational memory

PMID:
26937384
PMCID:
PMC4753805
DOI:
10.1016/j.nicl.2016.01.008
[Indexed for MEDLINE]
Free PMC Article

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