Abstract
Research during the past two decades has demonstrated an important role of the vestibular system in topographical orientation and memory and the network of neural structures associated with them. Almost all of the supporting data have come from animal or human clinical studies, however. The purpose of the present study was to investigate the link between vestibular function and topographical memory in normal elderly humans. Twenty-five participants aged 70 to 85 years who scored from mildly impaired to normal on the Montreal Cognitive Assessment (MoCA) received three topographical memory tests: the Camden Topographical Recognition Memory Test (CTMRT), a computerized topographical mental rotation test (TMRT), and a virtual pond maze (VPM). They also received six vestibular or oculomotor tests: optokinetic nystagmus (OKN), visual pursuit (VP), actively generated vestibulo-ocular reflex (VOR), the sensory orientation test (SOT) for posture, and two measures of rotational memory (error in degrees, or RM°, and correct directional recognition, or RM→). The only significant bivariate correlations were among the three vestibular measures primarily assessing horizontal canal function (VOR, RM°, and RM→). A multiple regression analysis showed significant relationships between vestibular and demographic predictors and both the TMRT (R = 0.78) and VPM (R = 0.66) measures. The significant relationship between the vestibular and topographical memory measures supports the theory that vestibular loss may contribute to topographical memory impairment in the elderly.
Highlights
The topographical orientation system, known as the spatial navigation, topokinetic, and action-extrapersonal systems, is one of the four major networks in the brain governing our interaction with our 3D environment (Previc, 1998)
Activation of the hippocampus occurs during recall of topographical routes (Maguire et al, 1997), and damage to it results in a profound amnesia for spatial landmarks, loss of spatial maps, and severe topographical disorientation (Aguirre and D’Esposito, 1999)
The importance of the vestibular inputs to the hippocampus may be due to the fact that the head is the anchor for the topographical memory system (Previc, 1998)—the reference to it (“heading”) when describing movements in topographical space
Summary
The topographical orientation system, known as the spatial navigation, topokinetic, and action-extrapersonal systems, is one of the four major networks in the brain governing our interaction with our 3D environment (Previc, 1998). It is the system that is responsible for scene and route memory, presence in the world, and topographical orientation in the plane of the Earth’s surface (Previc, 1998). In maintaining a cognitive map of the environment, the hippocampus integrates inputs from various sensory modalities, the two most important of these being distal visual inputs representing large regions of mainly the upper visual field (Previc, 1998; Arcaro et al, 2009) and those emanating from the vestibular system. The primary labyrinthine inputs to the hippocampus and the topographical memory system in general are from the lateral/horizontal semicircular canals (Taube et al, 1996), which signal angular rotation of the head in the plane of the Earth’s surface (i.e., the domain of the topographical as opposed to gravitational orientation system). The importance of the vestibular inputs to the hippocampus may be due to the fact that the head is the anchor for the topographical memory system (Previc, 1998)—the reference to it (“heading”) when describing movements in topographical space
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