Probabilistic sequence learning in mild cognitive impairment

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.

Caudate Resting Connectivity Predicts Implicit Probabilistic Sequence Learning

“…Interpretation of the MTL's role in IPSL is further complicated by the fact that there is some behavioral evidence of preserved SL in patients with MTL damage (Nissen and Bullemer, 1987;Nissen et al, 1989;Reber and Squire, 1994), suggesting that this region may not be necessary for IPSL. However, such clinical groups sometimes show less learning than healthy controls when the to-be-learned sequences are more complex (the sort studied here) and/or when training is extended (Curran, 1997;Nemeth et al, 2013;Vandenberghe et al, 2006), implying that MTL involvement may be necessary under certain conditions. Despite the mixed evidence from IPSL studies in clinical groups, the bulk of the (albeit correlational) evidence in healthy samples, such as the one tested here, have shown that both caudate and MTL are activated during IPSL, although frequently on different timescales.…”

Implicit sequence learning in people with Parkinson’s disease

“…A recent paper suggested that the relative importance of the striatal and hippocampal learning systems varies within blocks (Nemeth et al, 2013). Nemeth et al compared sequence learning between healthy older adults and those with Mild Cognitive Impairment (MCI), a condition associated with declines in medial temporal lobe structure and function, but intact striatal function.…”

“…In the 1st Half Blocks, the MCI group again showed no learning, and therefore less than the Controls, while in the 2nd Half Blocks, the MCI group showed learning equal to the controls. Nemeth et al (2013) hypothesized that the 1st Half Blocks involved recall and reactivation of the sequence learned, thus reflecting learning dependent on the medial temporal lobe/hippocampus, while learning in the 2nd Half Blocks involved more automated and proceduralized behavior of learned sequences, and thus reflected striatal-based learning. This hypothesis is consistent with a processing-based model, which suggests that the hippocampus is involved in repeated encoding and reconsolidation, but may disengage as proceduralization occurs (Henke, 2010).…”

“…Results revealed that the PD group was able to learn the sequence, however, when learning was examined using a Half Blocks analysis (Nemeth et al, 2013), which compared learning in the 1st 25/50 trials of all blocks to that in the 2nd 25/50 trials, the PD group showed significantly less learning than Controls in the 2nd Half Blocks, but not in the 1st. Nemeth et al (2013) hypothesized that the 1st Half Blocks involve recall and reactivation of the sequence learned, thus reflecting hippocampal-dependent learning, while the 2nd Half Blocks involve proceduralized behavior of learned sequences, reflecting striatal-based learning. The present results suggest that the PD group had intact hippocampal-dependent implicit sequence learning, but impaired striatal-dependent learning.…”

Learning temporal statistics for sensory predictions in mild cognitive impairment

“…Previous behavioral studies showing preserved implicit learning in MCI patients (Negash et al, 2007;Nemeth et al, 2013), have not investigated the brain circuits that may support this ability in MCI. Our results suggest that predictive learning engages a corticostriatal-cerebellar network that is thought to be involved in implicit learning of temporal regularities and is spared in MCI.…”