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Spatial navigation is a complex cognitive skill that is necessary for everyday functioning in the environment. However, navigational skills are not typically measured in most test batteries assessing cognitive aging. The present paper reviews what we know about behavioral differences between older and younger adults in navigational skill and reviews the putative neural mechanisms that may underlie these behavioral differences. Empirical studies to date clearly identify navigation as an aspect of cognitive function that is vulnerable to the aging process. The few functional and structural neuroimaging studies that speak to neurological correlates of these age-related differences point to the hippocampus, parahippocampal gyrus, posterior cingulate gyrus (retrosplenial cortex), parietal lobes and pre-frontal cortex as structures critically involved in age effects on navigation. Outstanding issues in the field are addressed and productive avenues of future research are suggested. Among these outstanding issues include the necessity of performing longitudinal studies and differentiating between hippocampal and extra-hippocampal contributions to aging in navigation. The field may also be advanced by empirical assessment of navigational strategies and investigations into the multisensory nature of navigation including assessing the relative contributions of visual, vestibular, and proprioceptive function to age differences in navigational skill.

Circulating testosterone (T) levels have behavioral and neurological effects in both human and nonhuman species. Both T concentrations and neuropsychological function decrease substantially with age in men. The purpose of this prospective, longitudinal study was to investigate the relationships between age-associated decreases in endogenous serum T and free T concentrations and declines in neuropsychological performance. Participants were volunteers from the Baltimore Longitudinal Study of Aging, aged 50-91 yr at baseline T assessment. Four hundred seven men were followed for an average of 10 yr, with assessments of multiple cognitive domains and contemporaneous determination of serum total T, SHBG, and a free T index (FTI). We administered neuropsychological tests of verbal and visual memory, mental status, visuomotor scanning and attention, verbal knowledge/language, visuospatial ability, and depressive symptomatology. Higher FTI was associated with better scores on visual and verbal memory, visuospatial functioning, and visuomotor scanning and a reduced rate of longitudinal decline in visual memory. Men classified as hypogonadal had significantly lower scores on measures of memory and visuospatial performance and a faster rate of decline in visual memory. No relations between total T or the FTI and measures of verbal knowledge, mental status, or depressive symptoms were observed. These results suggest a possible beneficial relationship between circulating free T concentrations and specific domains of cognitive performance in older men.

This study assessed age differences in navigational behavior in a virtual Morris water maze (vMWM) and examined the ability of older adults to develop cognitive maps after vMWM experience. Compared with younger participants, older volunteers traversed a longer linear distance to locate the hidden platform. On the probe trial, younger volunteers spent a greater proportion of their total distance traveled in proximity to the platform and had more platform intersections. Analysis of map reproductions demonstrated that older participants used proximal objects to locate the goal but did not use room-geometry cues to aid navigation. These findings demonstrate age-related deficits on a laboratory measure of place learning and suggest that deficiencies in allocentric mapping may contribute to these deficits.

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Calculated free testosterone concentrations were lower in men who developed Alzheimer disease, and this difference occurred before diagnosis. Future research may determine whether higher endogenous free testosterone levels offer protection against a diagnosis of Alzheimer disease in older men.

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