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Counteractive effect of transcranial direct current stimulation on spatial attention biases

Laurie Geers1, 2*, Valerie Dormal1, 2, Yves Vandermeeren2, 3, Nicolas Masson1, 2 and Michael Andres1, 2
  • 1 Institute of Research in Psychological Sciences, Catholic University of Louvain, Belgium
  • 2 Institut de Neuroscience, Université Catholique de Louvain, Belgium
  • 3 CHU Dinant Godinne UCL Namur, Belgium

Transcranial direct current stimulation (tDCS) has the potential to modulate neuronal activity and modify behaviour. The enhancement of activity in one hemisphere relative to the other is assumed to benefit to the rehabilitation of hemineglect, a disorder of spatial attention consecutive to a unilateral lesion [1, 2]. Previous studies on neglect patients showed that anodal (excitatory) tDCS over the left or right posterior parietal cortex (PPC) reorient attention toward the opposite hemifield [3, 4, 5]. However, this mechanism has been mainly studied in visuospatial tasks, while visuomotor and representational aspects have received little consideration so far. In the present study, we investigated how tDCS modulates spatial attention during visuomotor behaviour and visual imagery in healthy humans. The visuomotor task required participants to cross out a maximum of targets randomly distributed over a digital tablet within thirty seconds. The digital tablet allowed us to compute the centre of gravity of the crossed targets, a sensitive measure indexing the number of errors but also their spatial distribution [6]. The visual imagery task required participants to mentally compare the similarity of two previously seen geometrical shapes that could differ either on their left or right side. The anode was positioned either over the left (n=24) or right (n=24) parietal cortex and the cathode was positioned over the controlateral orbitofrontal area. Participants performed the tasks under real and sham tDCS applied on two different days. The stimulated hemisphere and the order of the active and sham conditions were counterbalanced between participants. In the sham condition, the centre of gravity of the crossed targets revealed a leftward bias in half of the participants and a rightward bias in the other half. In the active condition, the visuomotor attention of participants was shifted in the direction opposite to their natural bias (observed in the sham condition), irrespective to the stimulated hemisphere. No effect was observed in the visual imagery task, possibly because this task relied on allocentric rather than egocentric spatial coordinates. The present findings demonstrate that activating the attention network through tDCS counteracts natural biases in visual search. Because the side of stimulation (i.e. left vs. right hemisphere) did not matter, we suggest that the net effect of tDCS is to re-balance activity within the whole network, which makes it an optimal technique to redeploy attention towards both hemispaces after a unilateral lesion. Summary Neglect is a disorder that prevents patients to detect the presence of an object in the visual field opposite to the hemisphere affected by a lesion. Transcranial electric stimulation is used to enhance activity in the damaged hemisphere and redeploy attention towards both hemispaces. Our study investigates the benefit of this technique for attention orientation in visuomotor coordination and visual imagery, two skills that are important to recover autonomy in everyday life. The results observed in healthy participants showed that transcranial electric stimulation contributes to cancel spatial biases in a visuomotor task. This finding opens perspectives for the neurorehabilitation of stroke patients.

References

[1] Halligan, P. W., Fink, G. R., Marshall, J. C., & Vallar, G. (2003). Spatial cognition: Evidence from visual neglect. Trends in Cognitive Science, 7(3), 125–133. [2] Kinsbourne, M. (1970). The cerebral basis of lateral asymmetries in attention. Acta Psychologica, 33, 193–201 [3] Ko, M. H., Han, S. H., Park, S. H., Seo, J. H., & Kim, Y. H. (2008). Improvement of visual scanning after DC brain polarization of parietal cortex in stroke patients with spatial neglect. Neuroscience letters, 448(2), 171-174. [4] Sparing, R., Thimm, M., Hesse, M. D., Küst, J., Karbe, H., & Fink, G. R. (2009). Bidirectional alterations of interhemispheric parietal balance by non-invasive cortical stimulation. Brain, 132(11), 3011-3020. [5] Sunwoo, H., Kim, Y. H., Chang, W. H., Noh, S., Kim, E. J., & Ko, M. H. (2013). Effects of dual transcranial direct current stimulation on post-stroke unilateral visuospatial neglect. Neuroscience letters, 554, 94-98. [6] Rorden, C., & Karnath, H. O. (2010). A simple measure of neglect severity. Neuropsychologia, 48(9), 2758-2763.

Keywords: Neurorehabiliation, hemineglect, Visuomotor coordination, neurostimulation, spatial attention

Conference: Belgian Brain Congress 2018 — Belgian Brain Council, LIEGE, Belgium, 19 Oct - 19 Oct, 2018.

Presentation Type: e-posters

Topic: NOVEL STRATEGIES FOR NEUROLOGICAL AND MENTAL DISORDERS: SCIENTIFIC BASIS AND VALUE FOR PATIENT-CENTERED CARE

Citation: Geers L, Dormal V, Vandermeeren Y, Masson N and Andres M (2019). Counteractive effect of transcranial direct current stimulation on spatial attention biases. Front. Neurosci. Conference Abstract: Belgian Brain Congress 2018 — Belgian Brain Council. doi: 10.3389/conf.fnins.2018.95.00062

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Received: 24 Aug 2018; Published Online: 17 Jan 2019.

* Correspondence: Miss. Laurie Geers, Institute of Research in Psychological Sciences, Catholic University of Louvain, Louvain-la-Neuve, Walloon Brabant, 1348, Belgium, laurie.geers@uclouvain.be