Testing visuo-spatial memory and executive function during navigation in children with adhd: the virtual city

Navigation is a complex process, requiring target localization, route planning or retrieval, and physical displacement. Traditionally, spatial navigation has been assessed by means of paper mazes, in manual space and not requiring locomotion. Only recently, novel tests for the assessment of navigation have been created and validated in adults and children, requiring different processing of spatial data. Whereas reaching locations are coded relative to the body, more options are available when navigating: updating egocentric locations or switching to an allocentric reference frame. The egocentric frame leads to the creation of body centered representation, based on subject-to object relation (Colombo et al. 2017). The allocentric reference frame leads instead to a representation independent from the subject’s point of view, based on object-to-object relationship. The latter cognitive strategy is supposed to be acquired later in life and is important to develop mature navigation skills, introducing a substantial computational simplification, but requiring in the meanwhile the maturation of specific neuronal populations. In real life, more than one strategy is often available and can be successful in many situations. People choose their strategy on the basis of task demands, environmental features, and individual characteristics. Convergent evidence points to a crucial age, around 10-11 years, for the achievement of adult-like navigation strategies, based on allocentric spatial representation (Belmonti et al. 2015). The aim of the study was to create a new ecological and motivating task, in a gaming format, to assess real locomotor navigation in a controlled laboratory space and under specific experimental conditions. The Virtual CityTM paradigm, which evolved from more recent Magic Carpet tasks, was created to allow assessing cognitive strategies in navigation, simulating skills needed in real-life scenarios which include complex neuropsychological functions beyond spatial memory as executive functions, frequently impaired in children diagnosed with neurodevelopmental disorders such as Attention Deficit Hyperactivity Disorder. In fact, convergent evidence underlie that these abilities recruited for a successful performance in a navigational task are specifically challenging for school-aged children with ADHD, characterized by persistent inattention and/or hyperactivity/impulsivity, present in at least two life contexts, associated with significant social and academic impairment and with onset before 12 years of age. The VC™ developed by our group consisted of a virtual town with houses, streets and crossroads projected on the ground. It includes a motion capture system, tracking body movement in 3D in real time. In one condition, children were required to walk through the city and reach a sequence of houses. In the other, before walking, they had to plan the shortest path to reach the houses, inhibiting the prepotent response to start walking. Results show a good feasibility of the paradigm (feasibility checklist and ad hoc questionnaire), being an ecological, motivating, potentially informing clinical practice, recruiting different cognitive strategies than the neuropsychological tests presented in peri-personal space. Correlation and multivariate regression analyses between VC™ quantitative parameters (span and execution time) and neuropsychological measures of EFs and visuo-spatial memory (assessed with standardized tests) in ADHD children and control sample let to corroborate cognitive and neuropsychological processes involved in the navigation task. VC™ measure of span in ADHD children is statically significant different from the control group, with a greater span for typically developing children and positively correlated with age and with visuo-spatial short and working memory measures, suggesting that VC™ heavily relies on efficient spatial memory but also on the active manipulation of spatial information. Statistically significant correlations in ADHD group were also found between total execution time (both in following and in planning condition) and some EFs assessed with direct and indirect measures, pointing out the involvement of higher functions than memory in this complex activity. ADHD total execution times in both conditions also significantly differ from the control sample of typically developing children, with shorter execution time for the former group, probably due to traits of impulsiveness and poor planning abilities present in this population. The error analyses conducted through the video recordings, highlights the possibility of classifying different type of errors and to identify as more common the substitution ones (differently from Belmonti et al. 2015). Individual subject trajectories analyses suggested that children with ADHD may approach this task differently from typically developing children, considering the neuropsychological weaknesses assessed with standardized tests (memory, executive functioning). Therefore, preliminary data suggest VCTM paradigm as an ecological, playful and thus feasible tool, useful to assess some neuropsychological functions challenging for children with neurodevelopmental disorders, with good construct validity, simulating real-life situations and allowing a quantitative measurement of the performance in a motivation contest differently from paper and pencil or computerized tests. Larger samples of ADHD and healthy children may further explore neuropsychological processes and cognitive strategies underlying the Virtual City task, potentially opening new avenues for intervention.