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Abstract
Objective To distinguish between patients with amyloid-positive (A+) and -negative (A−) amnestic mild cognitive impairment (aMCI) by simultaneously investigating navigation performance, visual exploration behavior, and brain activations during a real-space navigation paradigm.
Methods Twenty-one patients with aMCI were grouped into A+ (n = 11) and A− cases by amyloid-PET imaging and amyloid CSF levels and compared to 15 healthy controls. Neuropsychological deficits were quantified by use of the Consortium to Establish a Registry for Alzheimer's Disease–plus cognitive battery. All participants performed a navigation task in which they had to find items in a realistic spatial environment and had to apply egocentric and allocentric route planning strategies. 18F-fluorodeoxyglucose was injected at the start to detect navigation-induced brain activations. Subjects wore a gaze-controlled, head-fixed camera that recorded their visual exploration behavior.
Results A+ patients performed worse during egocentric and allocentric navigation compared to A− patients and controls (p < 0.001). Both aMCI subgroups used fewer shortcuts, moved more slowly, and stayed longer at crossings. Word-list learning, figural learning, and Trail-Making tests did not differ in the A+ and A− subgroups. A+ patients showed a reduced activation of the right hippocampus, retrosplenial, and parietal cortex during navigation compared to A− patients (p < 0.005).
Conclusions A+ patients with aMCI perform worse than A− patients with aMCI in egocentric and allocentric route planning because of a more widespread impairment of their cerebral navigation network. Navigation testing in real space is a promising approach to identify patients with aMCI with underlying Alzheimer pathology.
Glossary
- A+=
- amyloid-positive;
- A−=
- amyloid-negative;
- AD=
- Alzheimer disease;
- aMCI=
- amnestic mild cognitive impairment;
- CERAD=
- Consortium to Establish a Registry for Alzheimer's Disease;
- FDG=
- 18F-fluorodeoxyglucose;
- rCGM=
- regional cerebral glucose metabolism;
- SPM=
- statistical parametric mapping;
- TMT-B=
- Trail-Making Test Part B
Footnotes
Go to Neurology.org/N for full disclosures. Funding information and disclosures deemed relevant by the authors, if any, are provided at the end of the article.
↵* These authors contributed equally to this work.
- Received March 25, 2019.
- Accepted in final form September 5, 2019.
- © 2020 American Academy of Neurology
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