Low-Resolution Place and Response Learning Capacities in Down Syndrome.

Mathilde Bostelmann,Stefano Vicari,Pamela Banta Lavenex,Lorelay Martorana,Deny Menghini,Pierre Lavenex,Floriana Costanzo

doi:10.3389/fpsyg.2018.02049

Mathilde Bostelmann, Stefano Vicari + Show 5 more

Open Access

https://doi.org/10.3389/fpsyg.2018.02049

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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.

Highlights

Down syndrome (DS), resulting from a partial or complete triplication of chromosome 21, is the most common genetic cause of intellectual disability, with an incidence of 1 in 625–1,000 live births (Bittles et al, 2006; de Graaf et al, 2017)
In order to characterize the place learning and response learning capacities of individuals with DS, mental age (MA)-matched typically developing (TD) children, and TD adults, we analyzed the proportion of correct choices in both the place learning and response learning tasks, in presence or absence of a local cue marking the reward location (Figure 2)
Note that if we consider only the performance of the individuals performing above chance level, there was no difference between groups [F(2,32) = 0.419, P = 0.662, η2p = 0.025, power = 0.112; DS individuals: M = 0.992, SE = 0.008; TD adults: M = 0.978, SE = 0.016; TD children: M = 1.000, SE = 0.000]

Summary

Introduction

Down syndrome (DS), resulting from a partial or complete triplication (trisomy) of chromosome 21, is the most common genetic cause of intellectual disability, with an incidence of 1 in 625–1,000 live births (Bittles et al, 2006; de Graaf et al, 2017). Low-Resolution Spatial Learning in Down Syndrome impairments in verbal short-term memory (Jarrold and Baddeley, 1997), especially in maintaining phonological information over a short delay (Raitano Lee et al, 2010). By contrast, their visuo-spatial memory (“where” memory) is reported as relatively preserved. Individuals with DS exhibit a performance similar to that of MA-matched typically developing (TD) children in learning where pictures are presented on a piece of paper (Vicari et al, 2005) and on the Corsi block-tapping task (Wang and Bellugi, 1994; Jarrold and Baddeley, 1997; Numminen et al, 2001; Laws, 2002). Difficulties in memorizing and recognizing pictures of objects (“what” memory) have been reported in DS (Vicari, 2001; Vicari et al, 2005)

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