Assessment of changes in neural activity during acquisition of spatial knowledge using EEG signal classification.

OBJECTIVE: This study explored the classification of electroencephalography (EEG) signals to assess changes in neural activity as individuals performed a training task in a virtual environment simulator. Commonly, task behavior and perception are used to assess a trainee's ability to perform a task, however, changes in cognition are not usually measured and could be important to provide a true indication of an individual's level of knowledge or skill. APPROACH: In this study, 15 participants acquired spatial knowledge via 60 navigation trials (divided into ten blocks) in a novel virtual environment. Time performance, perceived certainty, and EEG signal data were collected. MAIN RESULTS: A significant increase in alpha power and classification accuracy of EEG data from block 1 against blocks 2-10 was observed and stabilized after block 7, while time performance and perceived certainty measures improved and stabilized after block 5 and 6, respectively. SIGNIFICANCE: Results suggest that changes in neural activity, which may reflect an increase in cognitive efficiency, could provide additional insight beyond time performance and perceived certainty.

Addressing limitations of the Gait Variability Index to enhance its applicability: The enhanced GVI (EGVI).

Prior research has established the Gait Variability Index (GVI) as a composite measure of gait variability, based on spatiotemporal parameters, that is associated with functional outcomes. However, under certain circumstances the magnitude and directional specificity of the GVI is adversely affected by shortcomings in the calculation method. Here we present an enhanced gait variability index (EGVI) that addresses those shortcomings and improves the utility of the measure. The EGVI was further enhanced by removing some input spatiotemporal variables that captured overlapping/redundant information. The EGVI was used to reanalyze data from four previously published studies that used the original GVI. After removing data affected by the GVI's prior shortcomings, the association between EGVI and GVI values was stronger for the pooled dataset (r2 = 0.95) and for the individual studies (r2 = 0.88-0.98). The EGVI also revealed stronger associations between the index value and functional outcomes for some studies. The EGVI successfully addresses shortcomings in the GVI calculation that affected magnitude and directional specificity of the index. We have confirmed the validity of prior published work that used the original GVI, while also demonstrating even stronger results when these prior data were re-analyzed with the EGVI. We recommend that future research should use the EGVI as a composite measure of gait variability.

Neural field model of memory-guided search.

Many organisms can remember locations they have previously visited during a search. Visual search experiments have shown exploration is guided away from these locations, reducing redundancies in the search path before finding a hidden target. We develop and analyze a two-layer neural field model that encodes positional information during a search task. A position-encoding layer sustains a bump attractor corresponding to the searching agent's current location, and search is modeled by velocity input that propagates the bump. A memory layer sustains persistent activity bounded by a wave front, whose edges expand in response to excitatory input from the position layer. Search can then be biased in response to remembered locations, influencing velocity inputs to the position layer. Asymptotic techniques are used to reduce the dynamics of our model to a low-dimensional system of equations that track the bump position and front boundary. Performance is compared for different target-finding tasks.

Concurrent assessment of memory for object and place: Evidence for different preferential importance of perirhinal cortex and hippocampus and for promnestic effect of a neurokinin-3 R agonist.

We here explore the utility of a paradigm that allows the simultaneous assessment of memory for object (what) and object location (where) and their comparative predominance. Two identical objects are presented during a familiarity trial; during the test trial one of these is displaced, and a new object is presented in a familiar location. When tested 5 or 80min later, rats explored both the novel and the displaced objects more than two familiar stationary objects, indicating intact memory for both, object and place. When tested 24h later rats explored the novel object more than the displaced familiar one, suggesting that forgetting differently influenced object and place memory, with memory for object being more robust than memory for place. Animals that received post-trial administration of the neurokinin-3 receptor agonist senktide and were tested 24h later, now explored the novel and displaced objects equally, suggesting that the treatment prevented the selective decay of memory for location. Next, animals received NMDA lesions in either the perirhinal cortex or the hippocampus, which are hypothesized to be preferentially involved in memory for objects and memory for place, respectively. When tested 5 or 80min later, the perirhinal cortex lesion group explored the displaced object more, indicating relatively deficient object memory, while the hippocampal lesion led to the opposite pattern, demonstrating comparatively deficient place memory. These results suggest different preferential engagement of the perirhinal cortex and hippocampus in their processing of memory for object and place. This preference test lends itself to application in the comparison of selective lesions of neural sites and projection systems as well as to the assessment of possible preferential action of pharmacological agents on neurochemical processes that subserve object vs place learning.

Density-Dependent Spacing Behaviour and Activity Budget in Pregnant, Domestic Goats (Capra hircus).

Very little is known about the spacing behaviour in social groups of domestic goats (Capra hircus) in the farm environment. In this experiment, we studied interindividual distances, movement patterns and activity budgets in pregnant goats housed at three different densities. Norwegian dairy goats were kept in stable social groups of six animals throughout pregnancy at 1, 2 or 3 m2 per individual and their spacing behaviours (i.e., distance travelled, nearest and furthest neighbour distance) and activity budgets (e.g., resting, feeding, social activities) were monitored. Observations were made in the first, second and last thirds of pregnancy in the mornings, at noon and in the afternoons of each of these phases (4.5 hours per observation period). The findings show that goats held at animal densities of 2 and 3 m2 moved longer distances when they had more space per animal and kept larger nearest and furthest neighbour distances when compared to the 1 m2 per animal density. Less feeding activity was observed at the high animal density compared to the medium and low density treatments. The phase of gestation also had an impact on almost all behavioural variables. Closer to parturition, animals moved further distances and the increase in nearest and furthest neighbour distance was more pronounced at the lower animal densities. During the last period of gestation, goats spent less time feeding and more on resting, social behaviours and engaging in other various activities. Our data suggest that more space per goat is needed for goats closer to parturition than in the early gestation phase. We concluded that in goats spacing behaviour is density-dependent and changes with stages of pregnancy and activities. Finally, the lower density allowed animals to express individual preferences regarding spacing behaviour which is important in ensuring good welfare in a farming situation.

On the costs and benefits of repeating a nonspatial feature in an exogenous spatial cuing paradigm.

Recent research using the Posner cuing paradigm to explore inhibition of return seems to suggest that repetition of a nonspatial feature modulates cue-related facilitatory and inhibitory aftereffects differently in detection and discrimination tasks. Because the cues were unrelated to the final response in the detection task but parallel to (not orthogonal with) the final response in the discrimination task, it is unclear whether the different patterns of results were caused by the complexity of the decision (detection vs. discrimination) or by the task relevance of the feature that might or might not repeat from cue to target. Using a paradigm modeled on previous work, in Experiment 1 (detection task) and 2 (discrimination task) we replicated the previous patterns: No early feature repetition benefit but reduced IOR for feature mismatch trials in the detection task; and large early feature repetition benefit but no effect of feature match upon the later IOR in the discrimination task. In Experiment 3 (discrimination task), we used an "orthogonal-cuing" method: the feature (color) that could repeat or not from cue to target was not on the dimension being discriminated (shape). The pattern of results was very similar to what is observed in detection tasks. These results demonstrate that it is not the task but the task relevance of the repeating feature that modulates facilitation and inhibition effects. The findings are generally consistent with a habituation account of the inhibitory aftereffects of orienting but do not rule out the contribution of other mechanisms.

Conceptualizing intragroup and intergroup dynamics within a controlled crowd evacuation.

Social dynamics play a critical role in successful pedestrian evacuations. Crowd modeling research has made progress in capturing the way individual and group dynamics affect evacuations; however, few studies have simultaneously examined how individuals and groups interact with one another during egress. To address this gap, the researchers present a conceptual agent-based model (ABM) designed to study the ways in which autonomous, heterogeneous, decision-making individuals negotiate intragroup and intergroup behavior while exiting a large venue. A key feature of this proposed model is the examination of the dynamics among and between various groupings, where heterogeneity at the individual level dynamically affects group behavior and subsequently group/group interactions. ABM provides a means of representing the important social factors that affect decision making among diverse social groups. Expanding on the 2013 work of Vizzari et al., the researchers focus specifically on social factors and decision making at the individual/group and group/group levels to more realistically portray dynamic crowd systems during a pedestrian evacuation. By developing a model with individual, intragroup, and intergroup interactions, the ABM provides a more representative approximation of real-world crowd egress. The simulation will enable more informed planning by disaster managers, emergency planners, and other decision makers. This pedestrian behavioral concept is one piece of a larger simulation model. Future research will build toward an integrated model capturing decision-making interactions between pedestrians and vehicles that affect evacuation outcomes.

Bio-inspired modeling and implementation of the ocelli visual system of flying insects.

Two visual sensing modalities in insects, the ocelli and compound eyes, provide signals used for flight stabilization and navigation. In this article, a generalized model of the ocellar visual system is developed for a 3-D visual simulation environment based on behavioral, anatomical, and electrophysiological data from several species. A linear measurement model is estimated from Monte Carlo simulation in a cluttered urban environment relating state changes of the vehicle to the outputs of the ocellar model. A fully analog-printed circuit board sensor based on this model is designed and fabricated. Open-loop characterization of the sensor to visual stimuli induced by self motion is performed. Closed-loop stabilizing feedback of the sensor in combination with optic flow sensors is implemented onboard a quadrotor micro-air vehicle and its impulse response is characterized.

An assessment of the effects of navigation maps on drivers' mental workloads.

This study compares the mental workloads and subjective feelings of drivers navigating different road patterns using different formats of electronic and paper maps. The results show drivers experience lower mental workloads when using 2D electronic maps compared to 3D electronic maps. Significant differences in galvanic skin responses were observed for navigation map formats with different road intersection patterns. The low- and high-frequency components of heart rate variability showed significant differences between map formats for regular road intersections, but no significant differences between map formats for irregular road intersections. Statistically significant effects on subjective feelings were found between different map formats and road intersection patterns. The wider implications of the study results for the design and use of navigation map interfaces are discussed.

How do we select multiple features? Transient costs for selecting two colors rather than one, persistent costs for color-location conjunctions.

In a previous study Lo, Howard, & Holcombe (Vision Research 63:20-33, 2012), selecting two colors did not induce a performance cost, relative to selecting one color. For example, requiring possible report of both a green and a red target did not yield a worse performance than when both targets were green. Yet a cost of selecting multiple colors was observed when selection needed be contingent on both color and location. When selecting a red target to the left and a green target to the right, superimposing a green distractor to the left and a red distractor to the right impeded performance. Possibly, participants cannot confine attention to a color at a particular location. As a result, distractors that share the target colors disrupt attentional selection of the targets. The attempt to select the targets must then be repeated, which increases the likelihood that the trial terminates when selection is not effective, even for long trials. Consistent with this, here we find a persistent cost of selecting two colors when the conjunction of color and location is needed, but the cost is confined to short exposure durations when the observer just has to monitor red and green stimuli without the need to use the location information. These results suggest that selecting two colors is time-consuming but effective, whereas selection of simultaneous conjunctions is never entirely successful.

Incorporating variability in honey bee waggle dance decoding improves the mapping of communicated resource locations.

Honey bees communicate to nestmates locations of resources, including food, water, tree resin and nest sites, by making waggle dances. Dances are composed of repeated waggle runs, which encode the distance and direction vector from the hive or swarm to the resource. Distance is encoded in the duration of the waggle run, and direction is encoded in the angle of the dancer's body relative to vertical. Glass-walled observation hives enable researchers to observe or video, and decode waggle runs. However, variation in these signals makes it impossible to determine exact locations advertised. We present a Bayesian duration to distance calibration curve using Markov Chain Monte Carlo simulations that allows us to quantify how accurately distance to a food resource can be predicted from waggle run durations within a single dance. An angular calibration shows that angular precision does not change over distance, resulting in spatial scatter proportional to distance. We demonstrate how to combine distance and direction to produce a spatial probability distribution of the resource location advertised by the dance. Finally, we show how to map honey bee foraging and discuss how our approach can be integrated with Geographic Information Systems to better understand honey bee foraging ecology.

Assessment of the caudate nucleus and its relation to route learning in both congenital and late blind individuals.

BACKGROUND: In the absence of visual input, the question arises as to how complex spatial abilities develop and how the brain adapts to the absence of this modality. As such, the aim of the current study was to investigate the relationship between visual status and an important brain structure with a well established role in spatial cognition and navigation, the caudate nucleus. We conducted a volumetric analysis of the caudate nucleus in congenitally and late blind individuals, as well as in matched sighted control subjects. RESULTS: No differences in the volume of the structure were found either between congenitally blind (CB) and matched sighted controls or between late blind (LB) and matched sighted controls. Moreover, contrary to what was expected, no significant correlation was found between caudate volume and performance in a spatial navigation task. Finally, consistent with previously published reports, the volume of the caudate nucleus was found to be negatively correlated with age in the sighted; however such correlations were not significant in the blind groups. CONCLUSION: Although there were no group differences, the absence of an age-volume correlation in the blind suggests that visual deprivation may still have an effect on the developmental changes that occur in the caudate nucleus.

Behavioral assessment of emotional and motivational appraisal during visual processing of emotional scenes depending on spatial frequencies.

Previous studies performed on visual processing of emotional stimuli have revealed preference for a specific type of visual spatial frequencies (high spatial frequency, HSF; low spatial frequency, LSF) according to task demands. The majority of studies used a face and focused on the appraisal of the emotional state of others. The present behavioral study investigates the relative role of spatial frequencies on processing emotional natural scenes during two explicit cognitive appraisal tasks, one emotional, based on the self-emotional experience and one motivational, based on the tendency to action. Our results suggest that HSF information was the most relevant to rapidly identify the self-emotional experience (unpleasant, pleasant, and neutral) while LSF was required to rapidly identify the tendency to action (avoidance, approach, and no action). The tendency to action based on LSF analysis showed a priority for unpleasant stimuli whereas the identification of emotional experience based on HSF analysis showed a priority for pleasant stimuli. The present study confirms the interest of considering both emotional and motivational characteristics of visual stimuli.

The cost of defeat: Capuchin groups travel further, faster and later after losing conflicts with neighbors.

Although competition between social groups is central to hypotheses about the evolution of human social organization, competitive interactions among group-mates are thought to play a more dominant role in shaping the behavior and ecology of other primate species. However, few studies have directly tested the impact of intergroup conflicts in non-human primates. What is the cost of defeat? To address this question, the movements of six neighboring white-faced capuchin (Cebus capucinus) social groups living on Barro Colorado Island, Panama were tracked simultaneously using an Automated Radio Telemetry System (ARTS), for a period of six months. Groups moved 13% (441 m) further on days they lost interactions compared with days they won interactions. To cover these larger distances, they traveled faster, stopped less frequently, and remained active later in the evening. Defeat also caused groups to alter their patterns of space use. Losing groups had straighter travel paths than winning groups, larger net displacements and were more likely to change their sleeping site. These results demonstrate that losing groups pay increased travel costs and suggest that they forage in low-quality areas. They provide some of the first direct evidence that intergroup conflicts have important energetic consequences for members of competitively unsuccessful primate social groups. A better understanding of how intergroup competition impacts patterns of individual fitness is thus needed to clarify the role that this group-level process plays in shaping the evolution of human- and non-human primate behavior.

Learning and exposure affect environmental perception less than evolutionary navigation costs.

Most behaviors are conditional upon successful navigation of the environment, which depends upon distance perception learned over repeated trials. Unfortunately, we understand little about how learning affects distance perception-especially in the most common human navigational scenario, that of adult navigation in familiar environments. Further, dominant theories predict mutually exclusive effects of learning on distance perception, especially when the risks or costs of navigation differ. We tested these competing predictions in four experiments in which we also presented evolutionarily relevant navigation costs. Methods included within- and between-subjects comparisons and longitudinal designs in laboratory and real-world settings. Data suggested that adult distance estimation rapidly reflects evolutionarily relevant navigation costs and repeated exposure does little to change this. Human distance perception may have evolved to reflect navigation costs quickly and reliably in order to provide a stable signal to other behaviors and with little regard for objective accuracy.

Use of the Gait Deviation Index and spatiotemporal variables for the assessment of dual task interference paradigm.

Three-dimensional gait analysis (3DGA) is an important element in the quantitative evaluation of gait in subjects with Parkinson's disease (PD). Indexes, such as the Gait Deviation Index (GDI), have recently been proposed as a summary measure of gait. The aim of the present study was to investigate the effectiveness of the GDI and spatiotemporal variables in the quantification of changes in gait during a dual-task (DT) exercise. Fourteen patients with idiopathic PD and nine healthy subjects (CG) participated in the study. All subjects walked under two conditions: free walking and DT walking. The GDI was computed from the 3DGA data. The results show gait impairment during DT, a significant difference between groups regarding GDI and an interaction effect involving the group, side and task factors. The CG and PDG were different independent of interference and side, but interference was only different for the PDG group. The results also demonstrate that the GDI should be an appropriate outcome measure for the evaluation of the effects of DT on patients with Parkinson's disease.

Optimization of apparatus design and behavioral measures for the assessment of visuo-spatial learning and memory of mice on the Barnes maze.

We have previously shown that apparatus design can affect visual-spatial cue use and memory performance of mice on the Barnes maze. The present experiment extends these findings by determining the optimal behavioral measures and test procedure for analyzing visuo-spatial learning and memory in three different Barnes maze designs. Male and female C57BL/6J mice were trained with a stable or random escape hole location and the sensitivities (statistical power) of four commonly used measures of learning and three measures of memory to detect differences between these training procedures were compared on each maze design. A maze design with a large diameter and no wall was optimal, because mice showed a reliable use of extra-maze visual cues, visuo-spatial search strategies, and spatial memory. A maze design with a small diameter, surrounding wall, and intra-maze visual cues was the least sensitive for determining visuo-spatial learning and memory, because mice showed little evidence of extra-maze cue use. Errors, distance traveled, and hole deviation scores were more sensitive measures of learning than latency to find the escape hole. Measures based on locating the escape hole (primary measures) were more sensitive than measures based on entering the escape hole (total measures). Measures of memory had similar levels of sensitivity on each maze. This experiment demonstrates that both apparatus design and the behavioral measures used as indicators of learning and memory can influence the ability of the Barnes maze to detect visuo-spatial learning and memory impairments in mice.

No country for old men: street use and social diet in urban Newcastle.

Within affluent societies, people who grow up in deprived areas begin reproduction much earlier than their affluent peers, and they display a number of other behaviors adapted to an environment in which life will be short. The psychological mechanisms regulating life-history strategies may be sensitive to the age profile of the people encountered during everyday activities. We hypothesized that this age profile might differ between environments of different socioeconomic composition. We tested this hypothesis with a simple observational study comparing the estimated age distribution of people using the streets in an affluent and a socioeconomically deprived neighborhood which were closely matched in other ways. We were also able to use the UK census to compare the age profile of observed street users with the actual age profile of the community. We found that people over 60 years of age were strikingly less often observed on the street in the deprived than in the affluent neighborhood, whereas young adults were observed more often. These differences were not reflections of the different age profiles of people who lived there, but rather of differences in which residents use the streets. The way people use the streets varies with age in different ways in the affluent and the deprived neighborhoods. We argue that chronic exposure to a world where there are many visible young adults and few visible old ones may activate psychological mechanisms that produce fast life-history strategies.

Adaptive social learning strategies in temporally and spatially varying environments : how temporal vs. spatial variation, number of cultural traits, and costs of learning influence the evolution of conformist-biased transmission, payoff-biased transmission, and individual learning.

Long before the origins of agriculture human ancestors had expanded across the globe into an immense variety of environments, from Australian deserts to Siberian tundra. Survival in these environments did not principally depend on genetic adaptations, but instead on evolved learning strategies that permitted the assembly of locally adaptive behavioral repertoires. To develop hypotheses about these learning strategies, we have modeled the evolution of learning strategies to assess what conditions and constraints favor which kinds of strategies. To build on prior work, we focus on clarifying how spatial variability, temporal variability, and the number of cultural traits influence the evolution of four types of strategies: (1) individual learning, (2) unbiased social learning, (3) payoff-biased social learning, and (4) conformist transmission. Using a combination of analytic and simulation methods, we show that spatial-but not temporal-variation strongly favors the emergence of conformist transmission. This effect intensifies when migration rates are relatively high and individual learning is costly. We also show that increasing the number of cultural traits above two favors the evolution of conformist transmission, which suggests that the assumption of only two traits in many models has been conservative. We close by discussing how (1) spatial variability represents only one way of introducing the low-level, nonadaptive phenotypic trait variation that so favors conformist transmission, the other obvious way being learning errors, and (2) our findings apply to the evolution of conformist transmission in social interactions. Throughout we emphasize how our models generate empirical predictions suitable for laboratory testing.

Psychometric evaluation of neglect assessment reveals motor-exploratory predictor of functional disability in acute-stage spatial neglect.

OBJECTIVE: To determine the psychometric properties of 2 neglect measures, the Behavioral Inattention Test (BIT)-conventional and the Catherine Bergego Scale (CBS), in acute spatial neglect. Spatial neglect is a failure or slowness to respond, orient, or initiate action toward contralesional stimuli, associated with functional disability that impedes stroke recovery. Early identification of specific neglect deficits may identify patients likely to experience chronic disability. However, psychometric evaluation of assessments has focused on subacute/chronic populations. DESIGN: Correlational/psychometric study. SETTING: Inpatient rehabilitation hospital. PARTICIPANTS: Screening identified 51 consecutive patients with a right-hemisphere stroke with left neglect (BIT score <129 or CBS score >11) tested an average of 22.3 days poststroke. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: We obtained BIT, CBS, and Barthel Index assessments for each participant and clinical and laboratory measures of perceptual-attentional and motor-intentional deficits. RESULTS: The BIT showed good reliability and loaded onto a single factor. Consistent with our theoretical prediction, principal components analysis of the CBS identified 2 underlying factors: Where perceptual-attentional items (CBS-PA) and embodied, motor-exploratory items (CBS-ME). The CBS-ME uniquely predicted deficits in activities of daily living (ADLs) assessed by using the Barthel Index, but did not predict clinical and laboratory assessments of motor-intentional bias. More severe neglect on the CBS-PA correlated with greater Where perceptual-attentional bias on clinical and laboratory tests, but did not uniquely predict deficits in ADLs. CONCLUSIONS: Our results indicate that assessments of spatial neglect may be used to detect specific motor-exploratory deficits in spatial neglect. Obtaining CBS-ME scores routinely might improve the detection of acute-stage patients with spatial action deficits requiring increased assistance that may persist to the chronic stage.