Acute stress switches spatial navigation strategy from egocentric to allocentric in a virtual Morris water maze.

Stress and stress hormones are known to influence the function of the hippocampus, a brain structure critical for cognitive-map-based, allocentric spatial navigation. The caudate nucleus, a brain structure critical for stimulus-response-based, egocentric navigation, is not as sensitive to stress. Evidence for this comes from rodent studies, which show that acute stress or stress hormones impair allocentric, but not egocentric navigation. However, there have been few studies investigating the effect of acute stress on human spatial navigation, and the results of these have been equivocal. To date, no study has investigated whether acute stress can shift human navigational strategy selection between allocentric and egocentric navigation. The present study investigated this question by exposing participants to an acute psychological stressor (the Paced Auditory Serial Addition Task, PASAT), before testing navigational strategy selection in the Dual-Strategy Maze, a modified virtual Morris water maze. In the Dual-Strategy maze, participants can chose to navigate using a constellation of extra-maze cues (allocentrically) or using a single cue proximal to the goal platform (egocentrically). Surprisingly, PASAT stress biased participants to solve the maze allocentrically significantly more, rather than less, often. These findings have implications for understanding the effects of acute stress on cognitive function in general, and the function of the hippocampus in particular.

Transit apps for people with brain injury and other cognitive disabilities: the state of the art.

Individuals with cognitive disability have difficulty using public transit, but little research is directed toward this issue. Recent studies suggest that smartphones may be useful assistive devices in this context. Current objectives were to (1) survey research into difficulties people with cognitive disabilities experience when using public transit, (2) survey the current state of the art of transit and personal navigation applications (apps) and features, (3) recommend best existing transit apps for people with cognitive disability, and (4) recommend the best designs and features of these apps to developers of future transit apps. Potentially useful features were found in four categories: Transit apps for (1) individuals with cognitive disabilities and (2) healthy individuals, and personal navigation apps for (3) individuals with cognitive disabilities and (4) healthy individuals. A total of 159 apps were examined, but only seven were found specific to public transit for cognitive disability. By comparing research recommendations and currently available features, we identified several unmet needs. We note that there appears to be a shortage of apps for this population-function but that there is good research in the area and it is well suited to inform app development.

Spatial deficits in a virtual water maze in amnesic participants with hippocampal damage.

The Morris water maze is a standard paradigm for the testing of hippocampal function in laboratory animals. Virtual versions of the Morris water maze are now available and can be used to assess spatial learning and memory ability in both healthy and brain injured participants. To evaluate the importance of the hippocampus in spatial learning and memory, we tested five amnesic participants with selective hippocampal damage using a virtual water maze called the Arena Maze. The amnesic participants with hippocampal damage were impaired on the invisible platform (place) task that required them to use distal cues, but were able to navigate almost as well as comparison participants when the invisible platform was marked by a single proximal cue. These results not only confirm that the hippocampus plays a necessary role in human navigation in large-scale environments but also provides a new link between the mnemonic and navigational roles of the hippocampus.

Incidental learning of allocentric and egocentric strategies by both men and women in a dual-strategy virtual Morris Water Maze.

In studies of human navigation, an underlying assumption is that, by nature, navigators are proficient with and strongly biased toward using only one strategy, either allocentric (cognitive mapping) or egocentric (stimulus-response based). Further, research often suggests that males are allocentric navigators whereas females are egocentric navigators. We tested these binary assumptions using two versions of a virtual Morris water maze (MWM). The Dual-strategy maze could be solved using either an allocentric or an egocentric strategy. Preferred strategy was tested by alternating test and probe trials. Two "Forced-strategy" probe trials tested navigators' ability to use their non-preferred strategy. Participants then completed the Place maze that was best solved using an allocentric strategy. In the Dual-strategy maze, there was no particular order of acquisition of a preferred strategy and a quarter of participants switched strategies; this switching was bilateral (from egocentric to allocentric and vice-versa). Navigators were most competent in the use of their preferred strategy. Importantly, navigators did learn (incidentally) information related to their non-preferred strategy and were capable of using that strategy. This pattern of results was shown for both males and females, although females did show a stronger preference for egocentric navigation than did males. We concluded that navigators can use all environmental information available to them and that the tendency to view people as innately allocentric or egocentric navigators does not allow for more nuanced investigations of navigational ability. Such investigations would better inform research into deficits in spatial ability in clinical populations.

Passively learned spatial navigation cues evoke reinforcement learning reward signals.

Since the suggestion by Tolman (1948) that both rodents and humans create cognitive maps during navigation, the specifics of how navigators learn about their environment has been mired in debate. One facet of this debate is whether or not the creation of cognitive maps - also known as allocentric navigation - involves reinforcement learning. Here, we demonstrate a role for reinforcement learning during allocentric navigation using event-related brain potentials (ERPs). In the present experiment, participants navigated in a virtual environment that allowed the use of three different navigation strategies (allocentric, egocentric-response, & egocentric-cue), in which their goal was to locate and remember a hidden platform. Following the navigation phase of the experiment, participants were shown "cue images" representative of the three navigation strategies. Specifically, we examined whether or not these passively learned strategy images elicited a reward positivity - an ERP component associated with reinforcement learning and the anterior cingulate cortex. We found that when allocentric navigators were shown previously learned cues predicting the goal location a reward positivity was elicited. The present findings demonstrate that allocentric navigational cues carry long-term value after navigation and lend support to the claim that reinforcement learning plays a role in the acquisition of allocentric navigation and thus the generation of cognitive maps.

Hex Maze: A new virtual maze able to track acquisition and usage of three navigation strategies.

Spatial navigation is a complex and multi-faceted skill that, in humans, is understood to encompass two distinct navigational strategies, namely allocentric and egocentric navigation. These differ in the frame of reference used and the brain networks activated. However, egocentric navigation can be further divided into two, equally distinct strategies depending on whether the navigator is using subject-to-object relations (egocentric-cue) or direction of body turns (egocentric-response) to navigate. To date, there are no experimental paradigms able to distinguish between participants' employment of allocentric, egocentric-cue and egocentric-response strategies, and to track their usage over time. The current study presents the Hex Maze: a novel virtual environment that can not only distinguish between the three navigational strategies, but can also be used to index aspects of strategy use such as preference, acquisition, stability and competence. To illustrate this, 32 male and 32 female participants were presented with the Hex Maze and sex differences in strategy usage were explored. While the results offer some support for previously identified sex differences in strategy preference, there were no significant sex differences in the novel measures of strategy acquisition, stability, or multi-strategy competence. Additionally, our results suggest that strategy preference does not preclude learning to competently navigate using other strategies. Importantly, the current study offers validation for the Hex Maze as an unbiased method of exploring spatial navigation, and it is anticipated that this easy-to-use tool will be valuable across research and clinical settings.

Virtual environment navigation tasks and the assessment of cognitive deficits in individuals with brain injury.

Navigation in real environments is often impaired by traumatic brain injury (TBI). These deficits in wayfinding appear to be due to disruption of cognitive processes underlying navigation and may in turn be due to damage to the hippocampus and frontal lobes. These wayfinding problems after TBI were investigated using a virtual simulation of a Morris Water Maze (MWM), a standard test of hippocampal function in laboratory animals. The virtual environment consisted of a large virtual arena in a very large virtual room whose walls provided views of a naturalistic landscape. Eleven community-dwelling TBI survivors and 12 comparison participants, matched for gender, age and education were tested to see if they could find a location in the arena marked by one of the following: (a) a visible platform, (b) a single proximal object, (c) a single proximal object among seven other distracter objects, or (d) distal features inside and outside the room. The proximal objects allowed participants to use egocentric (body-centered) navigational strategies that rely on relatively simple stimulus-response associations. The absence of proximal cues forced the participants to rely on distal features of the environment (room walls, landscape elements) and tested their ability to use allocentric (world-based) navigational strategies requiring cognitive mapping. Results indicated that the navigation of TBI survivors was not impaired when the proximal cues were present but was impaired when proximal cues were absent. These results provide more evidence that the navigational deficit after TBI is due to an inability to form, remember or use cognitive maps.

Direct measurement of spontaneous strategy selection in a virtual Morris water maze shows females choose an allocentric strategy at least as often as males do.

Considerable evidence indicates that males navigate large-scale space better than females, and some have previously attributed this difference to a greater ability of males to select or use an allocentric (cognitive mapping) navigational strategy. We directly tested this proposal by having males and females navigate in an "ambiguous" virtual Morris water maze environment that permitted participants to choose and use either an allocentric or an egocentric strategy. A novel probe trial at the end of training revealed which strategy each participant had been using and showed that the strategy selected by the greatest number of males and females was allocentric, and that this bias was even greater for females. Traditional measures of navigational performance (distance, latency, probe dwell time) indicated that overall, males were more efficient than females. However, this gender difference was not related to strategy choice: males were better than females regardless of strategy, though the difference was significant only in those navigating allocentrically. These data indicate that while males may navigate allocentrically more efficiently than females, this does not account for the male advantage in navigation. The data also indicate that under specific circumstances, females may also prefer and use an allocentric strategy to navigate. These findings have implications for theories regarding the differential use of the hippocampus by men and women.

Simple gaze analysis and special design of a virtual Morris water maze provides a new method for differentiating egocentric and allocentric navigational strategy choice.

We present a novel method of combining eye tracking with specially designed virtual environments to provide objective evidence of navigational strategy selection. A simple, inexpensive video camera with an easily built infrared LED array is used to capture eye movements at 60Hz. Simple algorithms analyze gaze position at the start of each virtual maze trial to identify stimuli used for navigational orientation. To validate the methodology, human participants were tested in two virtual environments which differed with respect to features usable for navigation and which forced participants to use one or another of two well-known navigational strategies. Because the environmental features for the two kinds of navigation were clustered in different regions of the environment (and the video display), a simple analysis of gaze-position during the first (i.e., orienting) second of each trial revealed which features were being attended to, and therefore, which navigational strategy was about to be employed on the upcoming trial.

Human spatial navigation deficits after traumatic brain injury shown in the arena maze, a virtual Morris water maze.

OBJECTIVE: Survivors of traumatic brain injury (TBI) often have spatial navigation deficits. This study examined such deficits and conducted a detailed analysis of navigational behaviour in a virtual environment. DESIGN: TBI survivors were tested in a computer simulation of the Morris water maze task that required them to find and remember the location of an invisible platform that was always in the same location. A follow-up questionnaire assessed everyday spatial ability. METHOD: Fourteen survivors of moderate-to-severe TBI were compared to 12 non-injured participants. RESULTS: TBI survivors navigated to a visible platform but could not learn the location of the invisible platform. The difference between TBI survivors and uninjured participants was best indicated by two new dependent variables, path efficacy and spatial scores. CONCLUSION: This study confirms the capacity of virtual environments to reveal spatial navigation deficits after TBI and establishes the best way to identify such deficits.