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Down Syndrome and Memory

All people with Down syndrome (DS) have a mild-to-moderate learning disability. DS affects both physical and cognitive development and the severity of the impairments among individuals vary tremendously . There are many hypotheses as to why this impairment is seen. One indication is that there are several key parts of the brains of individuals with Down syndrome appear smaller than in people without DS. These key areas would include: the hippocampus, frontal cortex, and cerebellum. The cerebellum is responsible for the regulation and coordination of complex voluntary muscular movement, the frontal cortex identifies which memories are stored, and the hippocampus in important in the formation of new memories. As a result of the volume loss there are impairments in in memory and cognition . An additional study correlates the over-expression of a number of Hsa21 genes; which was tested in mouse models and the results display learning and memory defects in the mice. This is suggestive that trisomy of these genes may contribute to learning disability in people with DS .

Short-term Memory in Down Syndrome

It has been established that individuals with DS have a deficit in the phonological loop; however, the visuospatial sketchpad appears to be well preserved . The phonological loop allows an individual to hold visual and spatial images for manipulation, while the phonological loop allows for the same management but with auditory memories . An explanation for why individuals with down syndrome struggle with verbal short-term memory tasks may be due to the presentation of information. Speech perception and production are typically problematic areas for individuals with DS; therefore information presented auditorily will cause the person to have issues .

The insufficiency in the phonological loop may be cause for a shortage in the central executive in persons with DS as well. The central executive utilizes both the visuospatial sketchpad and phonological loop. It has been shown that individuals with DS demonstrate poor performance in a variety of areas, such as inhibition, shifting, planning, fluency, and task switching due to a deficit in the central executive . The central executive provides cognitive control of working memory and the transfer of information back and forth between short-term and long-term memory .

Many studies have been conducted and supported the hypothesis that verbal short-term memory is reduced in individuals with Down Syndrome (DS). In children, adolescents, and adults with DS, it has been shown they have a shorter verbal span as well. This impairment continues to be demonstrated even when items are presented visually or when the answer to the task is given by pointing at items on a board and thereby avoiding the need for a verbal response. 

Long-Term Memory in Down Syndrome

Other research has suggested that the capability for explicit long-term memory in persons with DS is also impaired. A study compared individuals with an intellectual disability of unspecified aetiology and a group of mental age-matched typically-developing children. This research concluded that the Down syndrome group scored significantly lower than both of the other groups on tests of free recall of word lists and a short story .