Perceptual Mnemonic Medial Temporal Lobe Function in Individuals with Down Syndrome

Abstract

Behavioral data in individuals with Down syndrome (DS) and mouse models of the syndrome suggest impaired object processing. In this study we examined the component processes that may contribute to object memory deficits. A neuropsychological test battery was administered to individuals with DS (n=28), including tests targeting perirhinal cortex (PRC) and prefrontal cortex (PFC) function, tests of perception (i.e., convexity based figure ground perception), and tests of memory (object recognition and object-in-place learning). To compare to individuals with DS, the same number of typically developing chronological age (CA, n=28) and mental age-matched (MA, n=28) controls were recruited. We observed object memory deficits in DS (p<0.001). In contrast, the DS group showed relatively intact use of convexity when making figure-ground judgments and spared PRC-dependent function, as compared to MA control. In addition, measures of PFC function seemed to be related to performance on object recognition tasks. These findings suggest that the inputs into the MTL from low and high level perceptual processing streams may be intact in DS. The object memory deficits we observed might reflect impaired PFC function.