Cerebellar neuromodulation improves naming in post-stroke aphasia

Abstract

Transcranial direct current stimulation has been shown to increase the efficiency of language therapy in chronic aphasia; however, to date, an optimal stimulation site has not been identified. We investigated whether neuromodulation of the right cerebellum can improve naming skills in chronic aphasia. Using a randomized, double-blind, sham-controlled, within-subject crossover study design, participants received anodal cerebellar stimulation (n = 12) or cathodal cerebellar stimulation (n = 12) + computerized aphasia therapy then sham + computerized aphasia therapy, or the opposite order. There was no significant effect of treatment (cerebellar stimulation versus sham) for trained naming. However, there was a significant order x treatment interaction, indicating that cerebellar stimulation was more effective than sham immediately post-treatment for participants who received cerebellar stimulation in the first phase. There was a significant effect of treatment (cerebellar stimulation versus sham) for untrained naming immediately post-treatment and the significant improvement in untrained naming was maintained at two months post-treatment. Greater gains in naming (relative to sham) were noted for participants receiving cathodal stimulation for both trained and untrained items. Thus, our study provides evidence that repetitive cerebellar transcranial direct stimulation combined with computerized aphasia treatment can improve picture naming in chronic post-stroke aphasia. These findings suggest that the right cerebellum might be an optimal stimulation site for aphasia rehabilitation and this could be an answer to handle heterogeneous participants who vary in their size and site of left hemisphere lesions.

Keywords: aphasia; cerebellum; language therapy; stroke; transcranial direct current stimulation.

© The Author(s) (2020). Published by Oxford University Press on behalf of the Guarantors of Brain.

Figures

Graphical Abstract

Figure 1

Study design and stimulation. (A) A randomized, double-blind, sham-controlled, within-subject crossover study design was utilized. Participants took part in two intervention phases, separated by a wash out period of 2 months. (B) A 2 mA of anodal or cathodal stimulation was generated between two 5 cm × 5 cm saline soaked sponges, where one active electrode (anode in ‘group anode’ or cathode in ‘group cathode’) was placed on the right cerebellum, and the reference electrode (cathode in ‘group anode’ or anode in ‘group cathode’) was placed on the right shoulder.

Figure 2

Computerized treatment task. During treatment, a picture appeared on the computer screen followed by a video of the speaker saying a word that either matched or did not match the preceding picture. The participant was instructed to press a green response button if the picture and spoken word matched and a red response button if they did not match. Immediate feedback was provided following each response in the form of a ‘smiley face’ for correct responses and a ‘frowny face’ for incorrect responses.

Figure 3

Trained naming accuracy. Mean change from baseline in Naming 80 test accuracy for sham and tDCS conditions immediately post-treatment and 2 months post-treatment. Error bars show standard errors.

Figure 4

Trained naming accuracy separated by group and order. Mean change from baseline in Naming 80 test accuracy for group anode and group cathode. Within each group, participants were assigned to receive ‘tDCS first then sham’ or ‘sham first then tDCS’. ‘Blue’ and ‘Green’ colours show participants who received tDCS first followed by sham. ‘Brown’ and ‘Orange’ colours show participants who received sham first followed by tDCS. Error bars show standard errors.

Figure 5

Untrained naming accuracy. Mean change from baseline in PNT accuracy for sham and tDCS conditions immediately post-treatment and 2 months post-treatment. Error bars show standard errors.

Figure 6

Untrained naming accuracy separated by group and order. Mean change from baseline in PNT accuracy for group anode and group cathode. Within each group, participants were assigned to receive ‘tDCS first then sham’ or ‘sham first then tDCS’. ‘Blue’ and ‘Green’ colours show participants who received tDCS first followed by sham. ‘Brown’ and ‘Orange’ colours show participants who received sham first followed by tDCS. Error bars show standard errors.