Disrupted anterior and posterior hippocampal structural networks correlate impaired verbal memory and spatial memory in different subtypes of mild cognitive impairment.

BACKGROUND AND PURPOSE

The anterior and posterior hippocampal networks represent verbal and spatial memory, respectively, and may play different roles in the pathological mechanism of amnestic mild cognitive impairment (aMCI) and non-amnestic MCI (naMCI), which has not been explored.

METHODS

A total of 990 older adults with 791 normal controls (NCs) (65 ± 6 years, 502 women), 140 aMCI (66 ± 7 years, 84 women) and 59 naMCI (66 ± 7 years, 38 women) were included. A multivariate method, partial least squares, was used to assess the structural covariance networks of the anterior hippocampus (aHC) and posterior hippocampus (pHC), and their relationships with verbal memory and spatial memory in the three groups.

RESULTS

Three aHC and pHC structural covariance network patterns emerged: (1) the age pattern; (2) the specific aMCI pattern; and (3) the spatial memory pattern. Furthermore, aMCI patients had more extensive and severe damage in the three patterns, and correlated with greater decline in verbal memory, which was mainly characterized by the aHC network.

CONCLUSIONS

The aMCI and naMCI showed different patterns and damage in the structural covariance networks, and functional segregation of the aHC and pHC networks still exists in the process of pathological aging. A potential neural explanation is provided for the conversion of aMCI and naMCI into different types of dementia in the future.