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Exploring the impact of laterality and polarity of tDCS on therapy for post-stroke anomia: A case study

Anna M. Woollams1*, Margaret Sandars1 and Lauren L. Cloutman1
  • 1 University of Manchester, Psychology, United Kingdom

Anomia is a frequent and persistent symptom of post-stroke aphasia. Cortical neuroplasticity plays a significant role in language recovery following stroke and can be facilitated by behavioural speech and language therapy (e.g. Fridriksson et al., 2012). Existing research suggests that complementing therapy for anomia with neurostimulation techniques (such as transcranial Direct Current Stimulation, or tDCS) can lead to greater therapeutic gains, with studies suggesting that applying anodal (excitatory) tDCS to the left hemisphere and/or cathodal (inhibitory) tDCS to the right hemisphere may be particularly beneficial (e.g. Baker et al., 2010; Rosso et al., 2014). However, the effects of varying both polarity and laterality of tDCS have yet to be systematically investigated. The primary aim of the current study was to determine the optimal tDCS parameters to increase naming ability in an 81 year old right-handed male (JS) with chronic non-fluent post stroke anomia. Results of a pre-therapy screening assessment were used to create 12, 20-item therapy sets (6 treated and 6 untreated), matched across a range of psycholinguistic variables. JS completed two therapy runs over 7 months. The three therapy conditions within each run involved either anodal, cathodal or sham stimulation. Stimulation sites were determined on the basis of a previous MRI structural scan. In the first run, stimulation targeted the perilesional left inferior frontal gyrus (IFG) and in the second run, stimulation targeted its right homologue. In all six cycles, JS received 20 minutes of 1mA tDCS (electrodes 5cm x 7cm) on three consecutive days alongside computerised naming therapy. In the sham conditions, anodal stimulation was applied for one minute before being slowly turned off. The percentage of correctly named treated items increased in all conditions immediately following therapy. As shown in the Figure, for items consistently incorrect over both of the screening sessions, only the left anodal stimulation produced a significant improvement in naming performance, both immediately (McNemar=8.10, p=.002) and after 3 weeks (McNemar=5.14, p=.016). The initial effect of left anodal stimulation in terms of item gains was significantly greater than those seen for sham (Chi-square=13.33, p<.005). These results indicate that the effect of behavioural therapy for anomia was enhanced by anodal tDCS specifically to left frontal perilesional areas in this case of nonfluent aphasia, consistent with Baker et al. (2010) and Vestito et al. (2014). There was not a significant benefit associated with cathodal tDCS to contralesional right frontal regions, in contrast to Rosso et al. (2014). Overall, these results are consistent with neuroimaging work implicating perilesional regions in therapeutic improvements following stroke (Fridriksson, 2010; Fridriksson et al., 2012; Meinzer et al., 2008, Menke et al., 2009).

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References

Baker, J.M., Rorden, C. & Fridriksson, J. (2010). Using transcranial direct-current stimulation to treat stroke patients with aphasia. Stroke, 41(6), 1229-1236.

Fridriksson, J. (2010). Preservation and modulation of specific left hemisphere regions is vital for treated recovery from anomia in stroke. Journal of Neuroscience, 30(35), 11558-11564.

Fridriksson, J., Richardson, J.D., Filmore, P. & Cai, B. (2012). Left hemisphere plasticity and aphasia recovery. NeuroImage, 60(2), 854-863.

Meinzer, M., Flaisch, T., Breitenstein, C., Wienbruch, C., Elbert, T. & Rockstroh, B. (2008). Functional re-recruitment of dysfunctional brain areas predicts language recovery in chronic aphasia. NeuroImage, 39(4), 2038-2046.

Menke, R., Menizer, M., Kugel, H., Deppe, M., Baumgärtner, A., Schiffbauer, H., … & Breitenstein, C. (2009). Imagining short- and long-term training success in chronic aphasia. BMC Neuroscience, 10, 118.

Rosso, C., Perlbarg, V., Valabregue, R., Arbizu, C., Ferrieux, S., Alshawan, B., …& Samon, Y. (2014). Broca’s area damage is necessary but not sufficient to induce after-effects of cathodal tDCS on the unaffected hemisphere in post-stroke aphasia. Brain Stimulation, 7(5), 627-635.

Vestito, L., Rosellini, S., Mantero, M. & Bandini, F. (2014) Long-term effects of transcranial direct-current stimulation in chronic post-stroke aphasia: A pilot study. Frontiers in Human Neuroscience, 8(785), DOI: 10.3389/fnhum.2014.00785.

Keywords: stoke aphasia, Anomia, therapy, tDCS, perilesional plasticity

Conference: Academy of Aphasia 53rd Annual Meeting, Tucson, United States, 18 Oct - 20 Oct, 2015.

Presentation Type: Poster

Topic: Not student first author

Citation: Woollams AM, Sandars M and Cloutman LL (2015). Exploring the impact of laterality and polarity of tDCS on therapy for post-stroke anomia: A case study. Front. Psychol. Conference Abstract: Academy of Aphasia 53rd Annual Meeting. doi: 10.3389/conf.fpsyg.2015.65.00043

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Received: 01 May 2015; Published Online: 24 Sep 2015.

* Correspondence: Dr. Anna M Woollams, University of Manchester, Psychology, Manchester, United Kingdom, Anna.Woollams@manchester.ac.uk