The Inner Ear and Aging Brain: A Cross-Sectional Study of Vestibular Function and Morphometric Variations in the Entorhinal and Trans-Entorhinal Cortex

Abstract

Purpose: While the vestibular system is crucial for balance, posture, and stable vision, emerging evidence connects vestibular loss in older adults to spatial cognitive deficits. However, the specific neural pathways remain unclear. This study examines morphometric changes in the entorhinal cortex (ERC) and trans-entorhinal cortex (TEC), key regions in the vestibular spatial cognitive network, with vestibular function.

Methods: This cross-sectional study used T1-weighted MRI images and vestibular physiological data from 103 Baltimore Longitudinal Study of Aging participants (74 males and 29 females). Vestibular function was assessed through the cervical vestibular-evoked myogenic potential (cVEMP), ocular VEMP (oVEMP), and video head-impulse test (vHIT), examining both categorical presence/absence of responses and continuous measures (cVEMP amplitude, oVEMP amplitude, and VOR gain). Morphometric changes in the ERC and TEC were analyzed by examining surface expansions and contractions relative to average shapes.

Results: Reduced saccular function correlated with surface expansion in the left ERC's pro-rhinal, right ERC's intermediate caudal and superior regions, and right TEC's sulcal region. The decreased utricular function was associated with surface contraction in the left lateral TEC, left ERC's anterior sulcal and trans-entorhinal regions, and surface expansion in the lateral region of the left ERC. Reduced canal function showed surface contraction in the right ERC's pro-rhinal and lateral regions and the right TEC's posterior sulcal and trans-entorhinal regions.

Conclusion: These findings highlight the intricate link between vestibular function and ERC/TEC morphology, emphasizing their role in spatial and cognitive abilities. Future research will assess if structural changes due to vestibular loss contribute to cognitive deficits in aging and Alzheimer's disease.

Keywords: Aging; Entorhinal cortex; MRI; Shape analysis; Trans-entorhinal cortex; Vestibular function.

Fig. 1

Pipeline flowchart

Fig. 2

Schematic of shape analysis

Fig. 3

View of ERC overlayed with Krimer partitions

Fig. 4

ERC template showing significant results for the clustered left and right sides of the ERC (view from the caudal end, upside-down) for categorical cVEMP

Fig. 5

ERC template showing significant results for the clustered left and right sides of the ERC (view from the caudal end, upside-down) for categorical oVEMP

Fig. 6

TEC template showing significant results for the clustered left and right sides of the TEC (view from the caudal end, upside-down) for continuous oVEMP

Fig. 7

ERC template showing significant results for the clustered Left and Right sides of the ERC (view from the caudal end, upside-down) for categorical VOR

Fig. 8

ERC template showing significant results for the clustered left and right sides of the ERC (view from the caudal end, upside-down) for continuous VOR

Fig. 9

ERC template showing significant results for the clustered left and right sides of the ERC (view from the caudal end, upside-down) for categorical cVEMP

Fig. 10

TEC template showing significant results for the clustered left and right sides of the TEC (view from the caudal end, upside-down) for categorical cVEMP

Fig. 11

TEC template showing significant results for the clustered left and right sides of the TEC (view from the caudal end, upside-down) for continuous oVEMP

Fig. 12

ERC template showing significant results for the clustered left and right sides of the ERC (view from the caudal end, upside-down) for categorical VOR

Fig. 13

ERC template showing significant results for the clustered left and right sides of the ERC (view from the caudal end, upside-down) for continuous VOR

Fig. 14

TEC template showing significant results for the clustered left and right sides of the TEC (view from the caudal end, upside-down) for categorical VOR