Transcranial direct current stimulation to the parietal cortex in hemispatial neglect: A feasibility study.
OBJECTIVE
Prior research suggests that dampening neural activity of the intact, presumably overactive hemisphere, combined with increasing neural activity in the damaged hemisphere, might restore cortical interhemispheric balance and reduce neglect. In the present study we repeatedly applied a relatively new technique, transcranial direct current stimulation (tDCS), to the posterior parietal cortex to modulate spontaneous neural activity levels in a polarity dependent fashion to find evidence for improvements in severe hemispatial neglect in chronic patients.


METHODS
Eighty-nine patients were initially identified from our databases as having neglect, after thoroughly screening databases, consulting medical practitioners and baseline testing, only five met our inclusion criteria and agreed to participate. Sixty-five patients were excluded as they did not meet safety criteria for tDCS (epilepsy, metal implants), suffered from other medical conditions (i.e., heart disease, epilepsy, current psychiatric disorder) or displayed only mild neglect at baseline testing. Five patients with severe chronic hemispatial neglect were enrolled in a double-blind, placebo-controlled treatment program. TDCS or placebo was applied for 20 minutes over the left (cathodal) and right (anodal) posterior parietal cortex at an intensity of 2 mA on five consecutive days. Treatment conditions were separated by a four week wash-out period. Baseline corrected change in performance on the conventional subtests of the Behavioral Inattention Test (BIT) was our primary endpoint.


RESULTS
No treatment-related effects were observed for the BIT change scores and performance on individual subtests. Moreover, patients' performance somewhat improved only during the stimulation period (day one vs day five, irrespective of whether it was placebo or tDCS), but not thirty days later, indicating a practice effect.


CONCLUSIONS
The present study does not provide evidence that tDCS to the posterior parietal cortex improves chronic hemispatial neglect. As a result of in- and exclusion health and safety criteria the majority of patients were excluded, which indicates that performing large randomized controlled trials is not feasible in chronic neglect patients.
Utrecht University, Department of Experimental Psychology, Helmholtz Institute, Utrecht, The Netherlands; Nieuw Unicum, Zandvoort, The Netherlands. Electronic address: M.Smit@uu.nl.
Miranda
M
Smit
Radboud University Nijmegen, Donders Institute for Brain, Cognition and Behaviour, Nijmegen, The Netherlands.
Dennis J L G
DJ
Schutter
Utrecht University, Department of Experimental Psychology, Helmholtz Institute, Utrecht, The Netherlands; University Medical Center Utrecht, Department of Neurology, Rudolf Magnus Institute of Neuroscience, The Netherlands; Brain Center Rudolf Magnus and Center of Excellence for Rehabilitation Medicine, University Medical Center Utrecht and Rehabilitation Center De Hoogstraat, Utrecht, The Netherlands.
Tanja C W
TC
Nijboer
Brain Center Rudolf Magnus and Center of Excellence for Rehabilitation Medicine, University Medical Center Utrecht and Rehabilitation Center De Hoogstraat, Utrecht, The Netherlands.
Johanna M A
JM
Visser-Meily
University Medical Center Utrecht, Department of Neurology, Rudolf Magnus Institute of Neuroscience, The Netherlands.
L Jaap
LJ
Kappelle
Utrecht University, Department of Experimental Psychology, Helmholtz Institute, Utrecht, The Netherlands; Nieuw Unicum, Zandvoort, The Netherlands.
Neeltje
N
Kant
Stichting Zorggroep Noordwest-Veluwe, Sonnevanck, Harderwijk, The Netherlands.
Janne
J
Penninx
Utrecht University, Department of Experimental Psychology, Helmholtz Institute, Utrecht, The Netherlands; University Medical Center Utrecht, Department of Neurology, Rudolf Magnus Institute of Neuroscience, The Netherlands.
H Chris
HC
Dijkerman
D000368:Aged; D004311:Double-Blind Method; D005240:Feasibility Studies; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010296:Parietal Lobe / Q000502:physiology*; D010468:Perceptual Disorders / Q000209:etiology / Q000628:therapy*; D011597:Psychomotor Performance; D018709:Statistics, Nonparametric; D065908:Transcranial Direct Current Stimulation / Q000379:methods*
Behavioral inattention test; Chronic hemispatial neglect patients; Double blind controlled treatment program; Interhemispheric balance; Stroke; Transcranial direct current stimulation