Implicit Motor Sequence Learning and Working Memory Performance Changes Across the Adult Life Span.

Sarah Nadine Meissner,Ariane Keitel,Bettina Pollok,Martin Südmeyer

doi:10.3389/fnagi.2016.00089

Sarah Nadine Meissner, Ariane Keitel + Show 2 more

Open Access

https://doi.org/10.3389/fnagi.2016.00089

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Abstract

Although implicit motor sequence learning is rather well understood in young adults, effects of aging on this kind of learning are controversial. There is first evidence that working memory (WM) might play a role in implicit motor sequence learning in young adults as well as in adults above the age of 65. However, the knowledge about the development of these processes across the adult life span is rather limited. As the average age of our population continues to rise, a better understanding of age-related changes in motor sequence learning and potentially mediating cognitive processes takes on increasing significance. Therefore, we investigated aging effects on implicit motor sequence learning and WM. Sixty adults (18–71 years) completed verbal and visuospatial n-back tasks and were trained on a serial reaction time task (SRTT). Randomly varying trials served as control condition. To further assess consolidation indicated by off-line improvement and reduced susceptibility to interference, reaction times (RTs) were determined 1 h after initial learning. Young and older but not middle-aged adults showed motor sequence learning. Nine out of 20 older adults (compared to one young/one middle-aged) exhibited some evidence of sequence awareness. After 1 h, young and middle-aged adults showed off-line improvement. However, RT facilitation was not specific to sequence trials. Importantly, susceptibility to interference was reduced in young and older adults indicating the occurrence of consolidation. Although WM performance declined in older participants when load was high, it was not significantly related to sequence learning. The data reveal a decline in motor sequence learning in middle-aged but not in older adults. The use of explicit learning strategies in older adults might account for the latter result.

Highlights

Implicit motor sequence learning refers to the ability to incidentally acquire knowledge of sequences of events and actions
Due to reaction times (RTs) two standard deviations below or above the respective individual mean, max 6.02% of trials in young and 6.48% of trials in middle-aged and older adults respectively were excluded from further serial reaction time task (SRTT) analyses
Two participants of each age group showed RTs that were more than two standard deviations below or above the respective group mean in baseline, EoA and interference trials and were excluded from motor sequence learning and susceptibility to interference analyses

Summary

Introduction

Implicit motor sequence learning refers to the ability to incidentally acquire knowledge of sequences of events and actions. The acquisition of such skills occurs ‘‘on-line’’ during practice but skills can stabilize—manifesting as reduced susceptibility to interference—or even improve ‘‘off-line’’ without further training (Robertson et al, 2004a, 2005). Whereas some studies found intact acquisition in older adults (Howard and Howard, 1992; Brown et al, 2009; Nemeth and Janacsek, 2011), others suggest age-related declines in implicit motor sequence learning (Frensch and Miner, 1994; Howard et al, 2004). To the best of our knowledge, age-related differences in susceptibility to interference, the second component of consolidation, have not been investigated directly so far

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