Can tDCS enhance item-specific effects and generalization after linguistically motivated aphasia therapy for verbs?

Vânia de Aguiar; Roelien Bastiaanse; Rita Capasso; Marialuisa Gandolfi; Nicola Smania; Giorgio Rossi; Gabriele Miceli

doi:10.3389/fnbeh.2015.00190

Can tDCS enhance item-specific effects and generalization after linguistically motivated aphasia therapy for verbs?

Front Behav Neurosci. 2015 Jul 30:9:190. doi: 10.3389/fnbeh.2015.00190. eCollection 2015.

Authors

Vânia de Aguiar¹, Roelien Bastiaanse², Rita Capasso³, Marialuisa Gandolfi⁴, Nicola Smania⁴, Giorgio Rossi⁵, Gabriele Miceli⁶

Affiliations

¹ International Doctorate in Experimental Approaches to Language And Brain (IDEALAB, Universities of Trento, Groningen, Potsdam, Newcastle and Macquarie University)Rovereto, Italy; Center for Mind/Brain Sciences and Center for Neurocognitive Rehabilitation, University of TrentoRovereto, Italy; Center for Language and Cognition Groningen, University of GroningenGroningen, Netherlands.
² Center for Language and Cognition Groningen, University of Groningen Groningen, Netherlands.
³ S.C.A. Associates Rome, Italy.
⁴ Neuromotor and Cognitive Rehabilitation Research Centre, USO Neurological Rehabilitation, Azienda Ospedaliera Universitaria Integrata (AOUI) of VeronaVerona, Italy; Department of Neurological and Movement Sciences, University of VeronaVerona, Italy.
⁵ Neurology, Santa Maria del Carmine Hospital Rovereto, Italy.
⁶ Center for Mind/Brain Sciences and Center for Neurocognitive Rehabilitation, University of Trento Rovereto, Italy.

Abstract

Background: Aphasia therapy focusing on abstract properties of language promotes both item-specific effects and generalization to untreated materials. Neuromodulation with transcranial Direct Current Stimulation (tDCS) has been shown to enhance item-specific improvement, but its potential to enhance generalization has not been systematically investigated. Here, we test the efficacy of ACTION (a linguistically motivated protocol) and tDCS in producing item-specific and generalized improvement in aphasia.

Method: Nine individuals with post-stroke aphasia participated in this study. Participants were pre-tested with a diagnostic language battery and a cognitive screening. Experimental tasks were administered over multiple baselines. Production of infinitives, of finite verbs and of full sentences were assessed before and after each treatment phase. Nonword repetition was used as a control measure. Each subject was treated in two phases. Ten daily 1-h treatment sessions were provided per phase, in a double-blind, cross-over design. Linguistically-motivated language therapy focusing on verb inflection and sentence construction was provided in both phases. Each session began with 20 min of real or sham tDCS. Stimulation site was determined individually, based on MRI scans.

Results: Group data showed improved production of treated and untreated verbs, attesting the efficacy of behavioral treatment, and its potential to yield generalization. Each individual showed significant item-specific improvement. Generalization occurred in the first phase of treatment for all subjects, and in the second phase for two subjects. Stimulation effects at the group level were significant for treated and untreated verbs altogether, but a ceiling effect for Sham cannot be excluded, as scores between real tDCS and Sham differed only before treatment.

Conclusion: Our data demonstrate the efficacy of ACTION and suggest that tDCS may enhance both item-specific effects and generalization.

Keywords: aphasia rehabilitation; argument structure; generalization; linguistically motivated therapy; neuromodulation; sentence production; transcranial direct current stimulation (tDCS); verb retrieval.