Getting LOST: A conceptual framework for supporting and enhancing spatial navigation in aging.

Alzheimer’s disease (AD), as the most common form of dementia and leading cause for disability and death in old age, represents a major burden to healthcare systems worldwide. For the development of disease-modifying interventions and treatments, the detection of cognitive changes at the earliest disease stages is crucial. Recent advancements in mobile consumer technologies provide new opportunities to collect multi-dimensional data in real-life settings to identify and monitor at-risk individuals. Based on evidence showing that deficits in spatial navigation are a common hallmark of dementia, we assessed whether a memory clinic sample of patients with subjective cognitive decline (SCD) who still scored normally on neuropsychological assessments show differences in smartphone-assisted wayfinding behavior compared with cognitively healthy older and younger adults. Guided by a mobile application, participants had to find locations along a short route on the medical campus of the Magdeburg university. We show that performance measures that were extracted from GPS and user input data distinguish between the groups. In particular, the number of orientation stops was predictive of the SCD status in older participants. Our data suggest that subtle cognitive changes in patients with SCD, whose risk to develop dementia in the future is elevated, can be inferred from smartphone data, collected during a brief wayfinding task in the real world.

Objectives: Navigation strategies require different complex abilities. Without landmarks, navigation is based on information about self-velocity, which is transformed to position or orientation by a process called path integration (PI). Using PI, one can estimate the own position without visual or acoustic clues by integrating small increments of movement onto a continually updated representation of direction and distance from a starting point. Respective deficits can derive from damages of cerebral areas involved in spatial navigation, particularly structures of the temporal lobe, most notably the hippocampus, entorhinal cortex and parietal cortex. In this study, our aim was to establish a simple diagnostic tool to evaluate PI in patients with suspected deficits in spatial navigation.

Critical periods for alcohol-induced deficits in spatial navigation and passive avoidance learning were investigated with a rat model of fetal alcohol syndrome. Rats were exposed to alcohol prenatally (Gestational Days 1-10 or 11-22) or postnatally (Postnatal Days 2-10) or throughout all 3 periods. Offspring were tested in either a spatial navigation or an avoidance task as juveniles or adults. As juveniles, the combined exposure group took longer to learn the spatial navigation task compared with all other groups. This effect was not seen in adults. Passive avoidance performance was not affected. These results suggest that long-term exposure to alcohol during development has adverse effects on spatial learning. The lack of differences in the short-term exposure groups implies that there may not be 1 critical period of alcohol exposure, but that the adverse effects of alcohol during development may be cumulative on some behaviors.

Spatial navigation testing discriminates two types of amnestic mild cognitive impairment

There is considerable research on the neurobiological mechanisms within the hippocampal system that support spatial navigation. In this article I review the literature on navigational strategies in humans and animals, observations on hippocampal function in navigation, and studies of hippocampal neural activity in animals and humans performing different navigational tasks and tests of memory. Whereas the hippocampus is essential to spatial navigation via a cognitive map, its role derives from the relational organization and flexibility of cognitive maps and not from a selective role in the spatial domain. Correspondingly, hippocampal networks map multiple navigational strategies, as well as other spatial and nonspatial memories and knowledge domains that share an emphasis on relational organization. These observations suggest that the hippocampal system is not dedicated to spatial cognition and navigation, but organizes experiences in memory, for which spatial mapping and navigation are both a metaphor for and a prominent application of relational memory organization.

Prenatal cocaine effects on fear conditioning:: Exaggeration of sex-dependent context extinction

Spatial cognition is known to decline with aging. However, little is known about whether training can reduce or eliminate age-related deficits in spatial memory. We investigated whether a custom-designed video game involving spatial navigation, obstacle avoidance, and balance control would improve spatial memory in older adults. Specifically, 56 healthy adults aged 65 to 84 years received 10 sessions of multicomponent video game training, based on a virtual cityscape, over 5 weeks. Participants were allocated to one of three training conditions: the main intervention, the “CityQuest” group (n = 19), and two control groups, spatial navigation without obstacle avoidance (“Spatial Navigation-only” group, n = 21) and obstacle avoidance without spatial navigation (“Obstacles-only” group, n = 15). Performance on object recognition, egocentric and allocentric spatial memory (incorporating direction judgment tasks and landmark location tasks, respectively), navigation strategy preference, and executive functioning was assessed in pre- and post-intervention sessions. The results showed an overall benefit on performance in a number of spatial memory measures and executive function for participants who received spatial navigation training, particularly the CityQuest group, who also showed significant improvement on the landmark location task. However, there was no evidence of a shift from egocentric to allocentric strategy preference. We conclude that spatial memory in healthy older participants is amenable to improvement with training over a short term. Moreover, technology based on age-appropriate, multicomponent video games may play a key role in cognitive training in older adults.

Transient Deregulation of Canonical Wnt Signaling in Developing Pyramidal Neurons Leads to Dendritic Defects and Impaired Behavior

P34. I slipped – Did it slip my mind? Cognitive deficits in patients with a peripheral vestibular disorder

The purpose of this study was to examine differences between older and younger listeners in the ability to sequentially attend to and ignore words. Participants (n = 13 older adults and 13 younger adults) completed a temporally interleaved word recognition task. On each trial, 10 words were presented, and participants were instructed to repeat back every other word while ignoring the intervening words. Three variables were examined: (1) whether the word strings that were to be attended and to be ignored created syntactically correct sentences; (2) whether the to-be-attended and to-be-ignored words were presented from the same or from different spatial locations; and (3) whether the five target words in each trial (and the five distractor words in each trial) were spoken by a single talker or by five different talkers. In addition, digit-span forward and digit-span backward were measured and used as variables in correlation analyses. As a group, the younger participants outperformed the older listeners, particularly when the to-be-attended and to-be-ignored words were presented from the same spatial location (versus when they were presented with spatial separation). Compared with the younger participants, older listeners also made more error responses that were to-be-ignored words, although the proportion of errors that were not responses involving masking words did not significantly differ between groups. Scores on the digit-span-forward test (but not digit-span-backward scores or the degree of hearing loss) were associated with older individuals' performance on this temporally interleaved speech-recognition task. The overall pattern of results suggests that factors other than threshold elevation contribute to speech-understanding problems experienced by older listeners. However, although younger adults outperformed older listeners on this interleaved sentence task, older and younger adults benefited, to a similar extent, from spatial separation of the to-be-attended and to-be-ignored words, and from having a consistent target talker within a trial.

Spatial navigation abilities decline with age, affecting older adults' quality of life. Recent studies revealed a specific impairment in landmark-based reorientation, linked to changes in scene-selective brain regions' activity. While functional magnetic resonance imaging studies suggest increased activity in these regions in older adults, more detailed investigation of brain dynamics associated with visuospatial processing is warranted. We analyzed event-related potentials (ERPs) and event-related spectral perturbations recorded from electrodes over scene-selective regions. Twenty-eight young adults and 28 older adults performed a desktop-based reorientation task using objects as landmarks, contrasted with a passive scene perception task. Older adults showed reduced reorientation performance along with increased latencies of early cortical markers of visual processing in scene-selective regions, suggesting that navigational deficits may result from delayed processing of visuospatial information. Decreasing landmark size, and thus increasing perceptual difficulty, impaired performance in both age groups, but only resulted in a delayed P1 component in older adults, suggesting an age-related delayed early discrimination of smaller landmarks. Interestingly, by contrasting the reorientation task with a passive scene perception task, we were able to dissociate the age-related effect over the perception and the use of objects as landmarks. Our results suggest that most of the differences reported for neural markers of reorientation were already present in a passive scene perception task, highlighting the importance of accounting for age-related differences in scene perception when investigating deficits in visuospatial reorientation. When these differences in passive perception were accounted for using regression-based ERP, our results indicated that young adults showed increased neural markers of attentional resources allocated to the reorientation task, as indicated by an increased P1 amplitude. On the other hand, older adults exhibited increased N1 amplitude associated with theta activity during reorientation, suggesting that they might rely on more extensive neural resources to process visual objects, only when using them as landmarks. These findings emphasize the need to dissociate age-related changes in early perceptual processing from those affecting higher-order visuo-spatial mechanisms and suggest that age-related differences in scene processing may underpin some navigational deficits in older adults.

ABSTRACTThe hippocampus is closely tied to spatial navigation, a central component in cognitive functioning, and critically involved in age-associated cognitive decline and dementia. This study evaluated a novel, cognitive computerized spatial navigation training (CSNT) program targeting the hippocampus, with expectation of mitigating possible cognitive decline with bed rest (BR). During a 14-day BR study with 16 healthy, older men (mean age = 60 ± 3, range = 55–65 years), half received CSNT for 12 days in 50-min sessions and half were controls (watching documentaries). This design uniquely controlled diet, sleep, and other personal and environmental activities. Although there were no cognitive declines in controls post-BR, CSNT participants demonstrated significant increases in executive/attention ability and processing speed, and continued spatial navigation testing showed improvement to 400 days post-BR. This intervention may prove useful to mitigate cognitive declines known to occur in long periods of immobilization and could have broader implications in protecting against age-related cognitive decline.

Previous studies have suggested that discrete cross-sensory events could be incorrectly combined in the brain of older adults with a history of falls, possibly undermining motor and balance control. Based on previous findings that multisensory integration is modifiable with practice, even in an ageing population, we designed a serious game, named CityQuest, to train typical, everyday multisensory processes including sensori-motor control, spatial navigation, obstacle avoidance and balance control. Played over several sessions, this game was shown to improve these functions in older adults with and without a history of falls, depending on the specific condition of the game on which they were trained. Here, using voxel-based morphometry analysis of anatomical magnetic resonance imaging (MRI) data, we investigated structural changes in the brain of a smaller group of older adults from those who successfully completed this five-week intervention. A grey-matter (GM) volume increase in the precentral gyrus, and GM volume reduction in the inferior temporal and orbitofrontal gyri, was found for all participants. Changes in GM volume within regions of the cerebellum were differentially associated with fall-prone and healthy older adults. Furthermore, a greater GM volume increase in the precentral gyrus was observed in participants who performed the full CityQuest intervention relative to those required to avoid obstacles only. Our results support previous evidence that multisensory training can affect structural changes in the older brain and have implications for programmes designed for the successful rehabilitation of perceptual and cognitive functions.

The Aging Navigational System

It is well known that ischemia causes neuronal necrosis in selectively vulnerable sectors of the hippocampus. Since the hippocampus is involved in spatial navigation, learning, and memory, selective deficits in these areas may arise from ischemic brain damage. The objective of this study was to test whether a minimal ischemic insult, producing selective neuronal necrosis restricted to only a portion of the CA1 pyramidal cells of the hippocampus, could produce a detectable spatial navigation deficit. Male Wistar rats received 9 min of forebrain ischemia induced by carotid clamping and hypotension or sham operation with exposure of the carotid arteries. The rats were allowed to recover and were tested on a simple place task, a place learning-set task, and a pattern discrimination task in swimming pools paradigms. Subsequently, the rats were perfusion-fixed and their entire brains subjected to quantitative histopathologic analysis. Although both ischemic and sham-operated groups learned the simple place task, the learning-set task revealed defects in spatial navigation, reflected as increased errors and latency in the performance of the ischemic rats. In the subsequent pattern discrimination task, the ischemic group was superior to the control group, which perseverated by attempting to use a place strategy to solve the discrimination. Quantitative neuropathology revealed neuronal necrosis in the ischemia group limited to 50% of the CA1 zone of the hippocampus. Extrahippocampal damage consisted of rare cortical neuronal necrosis in 2 of 6 animals.(ABSTRACT TRUNCATED AT 250 WORDS)