Probabilistic sequence learning in mild cognitive impairment

Dezso Nemeth,Ilona Ádám,Karolina Janacsek,Király Elemérné,Kata Fazekas,Attila Csányi,Katalin Király,Kornél Németh,Zsuzsa Londe

doi:10.3389/fnhum.2013.00318

Abstract

Mild Cognitive Impairment (MCI) causes slight but noticeable disruption in cognitive systems, primarily executive and memory functions. However, it is not clear if the development of sequence learning is affected by an impaired cognitive system and, if so, how. The goal of our study was to investigate the development of probabilistic sequence learning, from the initial acquisition to consolidation, in MCI and healthy elderly control groups. We used the Alternating Serial Reaction Time task (ASRT) to measure probabilistic sequence learning. Individuals with MCI showed weaker learning performance than the healthy elderly group. However, using the reaction times only from the second half of each learning block—after the reactivation phase—we found intact learning in MCI. Based on the assumption that the first part of each learning block is related to reactivation/recall processes, we suggest that these processes are affected in MCI. The 24-h offline period showed no effect on sequence-specific learning in either group but did on general skill learning: the healthy elderly group showed offline improvement in general reaction times while individuals with MCI did not. Our findings deepen our understanding regarding the underlying mechanisms and time course of sequence acquisition and consolidation.

Highlights

Mild cognitive impairment (MCI) is a transition stage between normal age-related cognitive decline and the more serious symptoms of dementia caused by, for example, Alzheimer’s disease
At first, based on the standard Alternating Serial Reaction Time task (ASRT) analysis we found that individuals with Mild Cognitive Impairment (MCI) showed weaker implicit probabilistic sequence learning than the healthy aged group
In the case of general reaction time, the MCI group was faster in the first part of the blocks compared to the second part in Session 1

Summary

Introduction

Mild cognitive impairment (MCI) is a transition stage between normal age-related cognitive decline and the more serious symptoms of dementia caused by, for example, Alzheimer’s disease. Many who develop MCI eventually develop Alzheimer’s disease, some will remain stable or might even return to normal (Roberts et al, 2008). The characteristic symptoms of MCI are impaired memory functions during learning or recall, impaired attention and information processing evidenced by the speed with which these functions are executed, flawed executive functions, and perceptual motor-skill and languageexpression disturbances (e.g., word finding). Properties of implicit learning and its consolidation could be useful in the dissociation of MCI from healthy age-related changes and could contribute to a better understanding of the formation and consolidation of sequence acquisition, the role of the MTL and hippocampus in these processes

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Conclusion