Higher-order cognitive training effects on processing speed-related neural activity: a randomized trial

Abstract

Higher-order cognitive training has shown to enhance performance in older adults, but the neural mechanisms underlying performance enhancement have yet to be fully disambiguated. This randomized trial examined changes in processing speed and processing speed-related neural activity in older participants (57-71 years of age) who underwent cognitive training (CT, N = 12) compared with wait-listed (WLC, N = 15) or exercise-training active (AC, N = 14) controls. The cognitive training taught cognitive control functions of strategic attention, integrative reasoning, and innovation over 12 weeks. All 3 groups worked through a functional magnetic resonance imaging processing speed task during 3 sessions (baseline, mid-training, and post-training). Although all groups showed faster reaction times (RTs) across sessions, the CT group showed a significant increase, and the WLC and AC groups showed significant decreases across sessions in the association between RT and BOLD signal change within the left prefrontal cortex (PFC). Thus, cognitive training led to a change in processing speed-related neural activity where faster processing speed was associated with reduced PFC activation, fitting previously identified neural efficiency profiles.

Trial registration: ClinicalTrials.gov NCT00977418.

Keywords: Aging; Cognitive training; DSVT; Exercise; Neuroplasticity; Processing speed; Reasoning; fMRI.

Conflict of interest statement

Disclosure statement

The authors declare no competing financial interests.

Copyright © 2017 The Authors. Published by Elsevier Inc. All rights reserved.

Figures

Figure 1

Example of stimuli from the Digit-Symbol Verification Task. Participants in the present study completed the digit-symbol verification task while fMRI data were collected. On each trial, a key containing nine digit-symbol pairs and a single digit-symbol probe-pair appeared simultaneously for 3.5 s, and participants were to judge whether the probe-pair was in the key (A) or not (B). The digit-symbol pairings in the key and the probe-pair varied across trials. On half of the trials, the probe-pair matched a digit-symbol pair in the key, and on half of the trials, the probe-pair did not match a digit-symbol pair in the key. There were 52 trials in a run, and inter-stimulus intervals varied from .5 to 16.5 s.

Figure 2

(A) TOSL Abstraction Score and DSVT (B) RT, (C) proportion correct, and (D) RT coefficient of variation (CV) as functions of group and assessment session. For assessment session, B=baseline, Mid=6 weeks into the training or waiting period, and Post=post-training or post-waiting period. Black=Cognitive Training (CT) group, gray=Wait Listed Control (WLC) group, and gray dashed=Active Control (AC) group. Errors bars show SEM.

Figure 3

Cluster showing significant Group × Assessment Session interaction contrast of RT-related parameter estimates and mean RT-related parameter estimates as a function of assessment session and group extracted from the peak voxel within the cluster (peak voxel MNI coordinates shown below the images). Upper panel (A) shows a significant cluster in left prefrontal cortex (PFC) for the CT versus combined WLC and AC group contrasts (k=210 voxels; cluster-wise α=.05 requiring k=82 voxels at a voxel-wise Z=3.28 and α=.001); middle panel (B) shows significant cluster in left PFC for the CT versus WLC group contrast (k=139 voxels; cluster-wise α=.05 requiring k=116 voxels at a voxel-wise Z=3.28 and α=.001); and lower panel (C) shows significant cluster in left PFC for the CT versus AC group contrast (k=126 voxels; cluster cluster-wise α=.05 requiring k=126 voxels at a voxel-wise Z=3.28 and α=.001). Image orientations are in neurological convention indicated with R=Right. Red to yellow indicates increasing strength of the Group × Assessment Session interaction contrast. For assessment session, BL=baseline, Mid=6 weeks into the training or waiting period, and Post=post-training or post-waiting period. Black=Cognitive Training (CT) group, gray=combined Wait Listed Control (WLC) and Active Control (AC) group in A, gray=WLC group in B, and gray=AC group in C. Errors bars show SEM.