Low-Resolution Place and Response Learning Capacities in Down Syndrome

Abstract

Down syndrome (DS), the most common genetic cause of intellectual disability, results from the partial or complete triplication of chromosome 21. Individuals with DS are impaired at using a high-resolution, allocentric spatial representation to learn and remember discrete locations in a controlled environment. Here, we assessed the capacity of individuals with DS to perform low-resolution spatial learning, depending on two competing memory systems: (1) the place learning system, which depends on the hippocampus and creates flexible relational representations of the environment; and (2) the response learning system, which depends on the striatum and creates fixed stimulus–response representations of behavioral actions. Individuals with DS exhibited a preservation of the low-resolution spatial learning capacities subserved by these two systems. In place learning, although the average performance of individuals with DS was lower than that of typically developing (TD) mental age (MA)-matched children and TD young adults, the number of individuals with DS performing above chance level did not differ from TD children. In response learning, the average performance of individuals with DS was lower than that of TD adults, but it did not differ from that of TD children. Moreover, the number of individuals with DS performing above chance level did not differ from TD adults, and was higher than that of TD children. In sum, whereas low-resolution place learning appears relatively preserved in individuals with DS, response learning appears facilitated. Our findings are consistent with the hypothesis that the neural pathways supporting low-resolution place learning and response learning are relatively preserved in DS.

Path Integration and Cognitive Mapping Capacities in Down and Williams Syndromes

“…Our study thus revealed that in a real-world laboratory setting, individuals with DS exhibit cognitive mapping abilities that are similar to those of TD children within the same mental age range, whereas individuals with WS are comparatively impaired. These findings are consistent with previous findings suggesting a relative preservation of the ability to create and use low-resolution allocentric spatial representations in DS (Banta Bostelmann et al, 2018), and significant impairments in WS (Bostelmann et al, 2017).…”

“…Individuals with WS were severely impaired on this task: only 17% of the participants with WS tested (mean mental age 5.9 years) could solve the task, whereas 95% of TD children can solve the task from 3 years of age (Ribordy et al, 2013;Ribordy Lambert et al, 2015;Bostelmann et al, 2017). In contrast, 78% of the participants with DS (mean mental age 5.6 years) could solve the task (Bostelmann et al, 2018), thus exhibiting markedly better allocentric spatial capacities than participants with WS. These results provide the clearest evidence to date of the most basic cognitive mapping capacities of individuals with WS and DS, in a real-world laboratory setting enabling the integration of all sources of sensory information normally available when moving freely in the environment.…”

“…In that context, Bostelmann et al (2017Bostelmann et al ( , 2018 assessed the allocentric spatial capacities of individuals with WS and DS in a real-world laboratory paradigm: an open-field arena in which participants had to learn the location of one reward among four visually identical reward locations arranged at the cardinal positions in a 4 m × 4 m enclosure surrounded on three sides by opaque curtains. The reward was always hidden in the same location in the arena, but participants entered and exited the arena by different doors on every single trial.…”

“…In contrast, however, failure to succeed on the straight paths should be considered as evidence against the ability to build a cognitive B-C, Bench to Chair; C-T, Chair to Table; T-S, Table to Shelf; S-T, Shelf to Table; T-C, Table to Chair; C-B, Chair to Bench; Homing task, the letter/number indicates sessions in which the participant was considered to have failed; s1, straight session 1; s2, straight session 2; a1, angled session 1; a2, angled session 2. Allo task, performance of participants who were also tested in the open-field allocentric spatial learning task (Bostelmann et al, 2017(Bostelmann et al, , 2018: Pass, succeeded at the task; Fail, failed the task; /, not tested. Pass, average final location within the target quadrant; Fail, average final location not within the target quadrant.…”

“…Egocentric Tasks in the Real-World Bostelmann et al (2018) tested the ability of individuals with DS and TD children to solve a spatial response-learning task in a 4 m × 4 m open-field arena. In that task, the reward was hidden in one of four possible locations, which alternated between the left and right sides of the arena on each trial.…”