Relationship between hippocampal subfields volume and balance function in healthy older adults.

BACKGROUND: The volume of the hippocampus and its subfields is known to be affected by aging, disease, and physical training. In regard to training, the differential effects of aerobic exercise and dance training on the subfield volume suggest that balance function may be involved. However, the relationship between balance function and the volume of the hippocampus and its subfields remains unclear. METHODS: Subjects were 30 cognitively intact individuals. They underwent balance tests, cognitive tests and structural MRI scans. The balance index measured was the index of postural stability (IPS) under a visual block condition and/or a proprioception block condition. MR images acquired using a 3-tesla system and three-dimensional T1-weighted images were segmented in the hippocampal subfield with Freesurfer 6.0.0. The relationship between the IPS and hippocampal volume was evaluated. RESULTS: A positive correlation was observed only between the IPS closed eyes/soft surface condition and whole hippocampal volume ratio. In the subfields, positive correlations were found between the IPS and molecular layer of the hippocampus, granule cell layer of the dentate gyrus (GC-ML-DG), and cornu ammonis areas (CA)3 and CA4. These correlations were stronger under the closed eyes/soft surface condition than under the other conditions. CONCLUSIONS: A correlation between balance function and the volume of the hippocampus and subfields was found in healthy elderly subjects. The balance function may be involved in the volume of the whole hippocampus and specific subfields. The IPS closed eyes/soft surface condition is considered to reflect vestibular function. Thus, IPS may be useful in evaluations of the relationship between the vestibular system function via the hippocampus and balance.

Dynamic balance deficit and the neural network in Alzheimer's disease and mild cognitive impairment.

BACKGROUND: Patients with Alzheimer's disease (AD) and mild cognitive impairment (MCI) exhibit balance deficits. Although only a few studies have evaluated the relationship between the brain images and balance indices. In this study, we measured balance indices, including the index of postural stability (IPS) and assessed the relationship between the brain images and their clinical motor and cognitive functional features. METHODS: The study included patients with MCI (N = 14) and patients with AD (N = 19). The primary outcome was IPS under a visual block condition and/or a proprioception block condition. In addition, 9 MCI and 8 AD patients underwent a 1.5-Tesla (1.5-T) Magnetic Resonance Imaging (MRI) scan, and the relationships between the MRI parameters and the balance indices were evaluated. RESULTS: The IPS score was significantly lower in the AD group than the MCI group, but only under the closed eyes/hard surface condition. In terms of MRI, there was a significant positive correlation between the IPS and the regional betweenness centrality in the left hippocampal region. CONCLUSIONS: The finding of a significantly lower IPS score under the closed eyes/hard surface condition in AD than in MCI cases suggests that the vestibular and/or proprioceptive systems were more severely impaired in AD than MCI cases. The results suggest that a dynamic balance disturbance due to deficits of the vestibular hippocampal pathway may be a useful marker for the diagnosis of MCI and detection of disease progression from MCI to AD.