Behavioral and Neural Correlates of Cognitive Training and Transfer Effects in Stroke Patients

Abstract

Stroke lesions are frequently followed by cognitive impairments. Cognitive training is a non-pharmacological intervention that can promote neural compensation mechanisms and strategies to remediate cognitive impairments. The aims of this study were: (1) To investigate the cognitive performance, generalization effects, and neural correlates of semantic organization strategy training (SOST) in patients with chronic left frontoparietal stroke and healthy controls (HC); and (2) to compare the behavioral effects and neural correlates of SOST with an active control psychoeducation intervention (PI). In this randomized controlled study, all participants were randomly allocated into two groups, one group received SOST, and the other received PI intervention. Participants underwent two fMRI sessions, one prior and the other, after intervention. In each fMRI session, images were obtained during memory encoding task using a list of semantically related words. We found improved post-intervention memory performance in participants that received SOST (both patients and controls), indicated by number of words recalled, word clustering scores, and performance in a generalization task. The fMRI analysis revealed negative correlation between task performance and regions of the default-mode network. These results suggest that cognitive training using semantic organization strategy can improve episodic memory performance and promote potential functional neuroplasticity in patients with ischemic stroke lesions. Clinical Trial Registration: www.ClinicalTrials.gov, identifier: NCT03644290.

Keywords: cognitive training; episodic memory; fMRI; semantic organization strategies; stroke.

Conflict of interest statement

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Copyright © 2020 Miotto, Bazán, Batista, Conforto, Figueiredo, Martin, Avolio, Amaro and Teixeira.

Figures

Figure 1

Lesion Maps. Superposition of patients' lesions represented by the number of subjects that had lesions in each voxel. Left hemisphere lesion maps are presented separately for each group: patients that received Semantic Organization Strategy Training (SOST; n = 7; top); and patients that received Psychoeducation Intervention (PI; n = 6; bottom). Images in neurological orientation.

Figure 2

CONSORT flowchart of the recruitment and selection of the study participants. SP, Stroke patients; HC, Healthy Controls; fMRI, Functional Magnetic Resonance Imaging; SOST, Semantic Organization Strategy Training; PI, Psychoeducational Intervention.

Figure 3

Word-List Learning Paradigm (WLLP). Schematic representation of WLLP showing the structure of each task block (top): Semantically related (SR) block; and non-words (NW) block. The words presented in the image are only illustrations. The experiments were performed with words in Portuguese. The fMRI block sequence is also presented (bottom) showing an example with SR block (participants were randomly assigned to start with SR block or with NW block).

Figure 4

Plots of the Post vs. pre intervention average differences, with standard error bars, according to group (Healthy Controls; Stroke patients) and intervention (SOST, Semantic Organization Strategy Training; PI, Psychoeducation Intervention), for each of the 6 dependent variables evaluated: Word-List Learning Paradigm (WLLP) recall; WLLP clustering score; Supermarket Generalization Task (SGT) recall; SGT clustering score; brief metamemory questionnaire (BMQ) strategy use; and BMQ capacity.

Figure 5

Average BOLD responses in SR task block for each group in each run (Pre and Post-intervention) presented as Z-values (neurological orientation). Voxel threshold of Z > 2.3 and cluster corrected threshold of p < 0.05. PI, Psychoeducation Intervention; SOST, Semantic Organization Strategy Training; HC, Healthy Controls; SP, Stroke Patients.

Figure 6

Stroke patient ANOVA results, showing significant interaction effects between run, and intervention presented as Z-values (neurological orientation). Voxel threshold of Z > 2.3 and cluster corrected threshold of p < 0.05.

Figure 7

Plots of the semantically related (SR) task block BOLD response (beta-values from first-level GLM analyses) in pre and post-intervention runs in frontal cluster of default-mode network (DMN) found in the ANOVA with stroke patients (SP), showing changes for each subject, in each group. PI, Psychoeducation Intervention; SOST, Semantic Organization Strategy Training; HC, Healthy Controls; SP, Stroke Patients.