Age differences in neural correlates of route encoding and route recognition

Abstract

Spatial memory deficits are core features of aging-related changes in cognitive abilities. The neural correlates of these deficits are largely unknown. In the present study, we investigated the neural underpinnings of age-related differences in spatial memory by functional MRI using a navigational memory task with route encoding and route recognition conditions. We investigated 20 healthy young (18 -29 years old) and 20 healthy old adults (53 -78 years old) in a random effects analysis. Old subjects showed slightly poorer performance than young subjects. Compared to the control condition, route encoding and route recognition showed activation of the dorsal and ventral visual processing streams and the frontal eye fields in both groups of subjects. Compared to old adults, young subjects showed during route encoding stronger activations in the dorsal and the ventral visual processing stream (supramarginal gyrus and posterior fusiform/parahippocampal areas). In addition, young subjects showed weaker anterior parahippocampal activity during route recognition compared to the old group. In contrast, old compared to young subjects showed less suppressed activity in the left perisylvian region and the anterior cingulate cortex during route encoding. Our findings suggest that agerelated navigational memory deficits might be caused by less effective route encoding based on reduced posterior fusiform/parahippocampal and parietal functionality combined with diminished inhibition of perisylvian and anterior cingulate cortices correlated with less effective suppression of task-irrelevant information. In contrast, age differences in neural correlates of route recognition seem to be rather subtle. Old subjects might show a diminished familiarity signal during route recognition in the anterior parahippocampal region. D

Aging: Compensation or maturation?

“…4), with the most notable differences in SMG, DLPFC, and AC during the Delayed Recognition Memory condition. This result is consistent with other studies reporting a posterior-to-anterior shift (or ventralto-dorsal) in young relative to elderly (Grady et al, 2003;Meulenbroek et al, 2004) which is interpreted as reflecting the additional recruitment of dorsolateral prefrontal regions to facilitate memory (compensation). However, as pointed out previously, our elderly did not perform worse than the young, similar to many other studies.…”

“…Gagnon et al (2003), for example, indicate that young individuals, relative to the elderly, obtained higher scores on the recall of Rey and Taylor Complex figures, tests of visual memory. Similarly, a posterior-to-anterior shift in neuroimaging data in young relative to elderly has been reported in other studies of aging as well (Grady et al, 2003;Meulenbroek et al, 2004). When we asked our young about the strategy they used, young females in particular seem to focus on the details of the Walsh patterns (e.g., "I looked for patterns within each figure and tried to match them").…”

Spatial Navigation Impairment in Healthy Aging and Alzheimer’s Disease

“…The second approach to assess changes in brain function in spatial navigation accompanying aging is to use functional imaging. In the first route encoding and recognition study in a virtual reality building (Meulenbroek et al, 2004) subjects should remember a set of turns marked by arrows on the walls and then, during the recognition phase, on the same places choose the correct one of two arrows to follow the route. The elderly subjects reached slightly lower scores than young subjects, and compared to the young they showed diminished posterior fusiform-parahippocampal and parietal activity during route encoding, corresponding to the role of these brain areas in navigation.…”

Efficiency of route selection as a function of adult age

“…In our version of the task the participants were given a map of a zoo and were allowed as much time as desired to select the most efficient route to visit a specified set of exhibits. Shallice and Burgess (1991) speculated that this type of route selection or planning task is dependent on the frontal lobes, in contrast to the posterior and parietal involvement that has been found to be associated with the learning or remembering of routes (e.g., Meulenbroek, Petersson, Voermans, Weber, & Fernandez, 2004).…”