by Martin Rakusa
The symposium covered specific cognitive deficits of spatial memory, orientation, and navigation which may be clinical biomarkers for Mild Cognitive Impairment (MCI) and Alzheimer’s disease (AD). After a short introduction by professor Thomas Brandt, professor Vladislava Segen presented the first lecture, ‘Effects of aging and Alzheimer’s disease on spatial navigation’. Spatial cognition is one of the crucial cognitive functions. In her lecture, she presented the brain’s navigation circles that connect the entorhinal cortex, hypothalamus, temporal cortex, occipital cortex, medial parietal and medial prefrontal cortex. Spatial navigation is based on two principles: landmark navigation and self-motion based navigation, including path integration. Ageing affects both types of navigation. However, this process is enhanced in patients with AD. For example, amyloid-beta accumulates in the medial prefrontal and medial parietal cortex and disrupts navigation circles. On the other hand, navigation abilities may be enhanced, and in the future, we may be using virtual reality tools to help patients with mild AD.
In the second lecture ‘Spatial navigation deficits as cognitive markers for preclinical Alzheimer’s disease’, professor Jan Laczo gave a brief introduction on the biology of AD, followed by spatial navigation in patients with pre-clinical AD and mild AD. Patients with AD have difficulties in wayfinding and route learning. They need more time and make more mistakes than healthy controls. Results on navigational tests significantly correlate with AD biomarkers. Moreover, some studies suggest that even people at genetic risk of AD have impaired spatial navigation. In the end, he presented a ‘Real-space navigation test’ to detect patients with MCI or mild AD, which has high sensitivity and specificity.
Professor Brand gave the final lecture. In his lecture, he focused on the differences between bilateral vestibulopathy, hippocampal disorders, and spatial navigation impairment due to AD. In addition, he presented results from animal experiments and clinical trials.
During the discussion, chair Prof. Husain pointed out that most of the work is based on experiments in rodents, which do not rely on vision as much as humans. However, newer studies indicate that differences are getting smaller, and we may speculate that there won’t be any differences in a few years.
One of the important questions was at which level visual and vestibular information converge. Professor Brandt explained that this happens at the level of vestibular nuclei, which also indicates the importance of the spatial navigation system.
Another question from the audience was whether pilots, taxi drivers and others with similar occupations have milder cognitive decline than the rest of the population. Unfortunately, results from extensive studies on London’s taxi drivers did not show a protective effect. They also point out the gender differences. Several studies show that females had worse spatial navigation than men.
The symposium was very interesting and is recommended for students and residents.