Path Integration and Cognitive Mapping Capacities in Down and Williams Syndromes

Abstract

Williams (WS) and Down (DS) syndromes are neurodevelopmental disorders with distinct genetic origins and different spatial memory profiles. In real-world spatial memory tasks, where spatial information derived from all sensory modalities is available, individuals with DS demonstrate low-resolution spatial learning capacities consistent with their mental age, whereas individuals with WS are severely impaired. However, because WS is associated with severe visuo-constructive processing deficits, it is unclear whether their impairment is due to abnormal visual processing or whether it reflects an inability to build a cognitive map. Here, we tested whether blindfolded individuals with WS or DS, and typically developing (TD) children with similar mental ages, could use path integration to perform an egocentric homing task and return to a starting point. We then evaluated whether they could take shortcuts and navigate along never-traveled trajectories between four objects while blindfolded, thus demonstrating the ability to build a cognitive map. In the homing task, 96% of TD children, 84% of participants with DS and 44% of participants with WS were able to use path integration to return to their starting point consistently. In the cognitive mapping task, 64% of TD children and 74% of participants with DS were able to take shortcuts and use never-traveled trajectories, the hallmark of cognitive mapping ability. In contrast, only one of eighteen participants with WS demonstrated the ability to build a cognitive map. These findings are consistent with the view that hippocampus-dependent spatial learning is severely impacted in WS, whereas it is relatively preserved in DS.

A Critical Review of Spatial Abilities in Down and Williams Syndromes: Not All Space Is Created Equal

“…To our knowledge, other than the unpublished study by Mangan (27) no other study investigated the real-world allocentric spatial abilities of individuals with DS. Our findings in two lowresolution allocentric tasks, the allocentric open-field task and the cognitive mapping task, were consistent in showing that 75-95% of individuals with DS are capable of creating and using an allocentric spatial representation to orient and navigate in their environment (37,41). In order to succeed on these tasks participants must be able to create an allocentric representation (a.k.a., a cognitive map) of their surrounding environment that incorporates idiothetic cues, in the presence of vision in the openfield arena task, and in the absence of vision in the cognitive mapping task.…”

“…A majority of our participants were tested on both the openfield arena and the cognitive mapping task thus allowing us to make within-subject comparisons of allocentric abilities [Table 1; (41)]. By and large, the abilities of individuals with DS and individuals with WS to create and use a cognitive map without vision are consistent with our findings from the open-field arena with vision.…”

“…TD children's ability to rely both on the sequence of directional changes and their consistency with environmental landmarks at choice points or along the path may underlie their more efficient route learning (48). It is thus possible that the absence of visual guidance cues in our allocentric spatial studies, cues that would normally facilitate the performance of TD children as compared to individuals with DS, enabled participants with DS to perform similarly to MA-matched TD children (37,41).…”

“…In order to answer these two questions we designed an experiment to assess the ability of blindfolded individuals with DS, individuals with WS and TD children in the same mental age range to use path integration to create and use egocentric and allocentric spatial representations to navigate in their environment in the absence of visual input (41). Our study included 19 individuals with DS (mean MA 5.57 years), 18 individuals with WS (mean MA 5.89 years) and 28 TD children (mean CA 6.91 years).…”

“…We next tested the ability of the same participants to create and use a cognitive map to navigate and take shortcuts (41). In the same 8 × 8 m room, we placed four pieces of real-sized furniture, a bench, a shelf, a chair and a table, with one object placed at the center of each wall (Figure 4C).…”