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Dario Cazzoli,
René M Müri,
Rahel Schumacher,
Sebastian von Arx,
Silvia Chaves,
Klemens Gutbrod,
Stephan Bohlhalter,
Daniel Bauer,
Tim Vanbellingen,
Manuel Bertschi,
Stefan Kipfer,
Clive R Rosenthal,
Christopher Kennard,
Claudio L Bassetti,
Thomas Nyffeler
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ABSTRACT: Left-sided spatial neglect is a common neurological syndrome following right-hemispheric stroke. The presence of spatial neglect is a powerful predictor of poor rehabilitation outcome. In one influential account of spatial neglect, interhemispheric inhibition is impaired and leads to a pathological hyperactivity in the contralesional hemisphere, resulting in a biased attentional allocation towards the right hemifield. Inhibitory transcranial magnetic stimulation can reduce the hyperactivity of the contralesional, intact hemisphere and thereby improve spatial neglect symptoms. However, it is not known whether this improvement is also relevant to the activities of daily living during spontaneous behaviour. The primary aim of the present study was to investigate whether the repeated application of continuous theta burst stimulation trains could ameliorate spatial neglect on a quantitative measure of the activities of daily living during spontaneous behaviour. We applied the Catherine Bergego Scale, a standardized observation questionnaire that can validly and reliably detect the presence and severity of spatial neglect during the activities of daily living. Eight trains of continuous theta burst stimulation were applied over two consecutive days on the contralesional, left posterior parietal cortex in patients suffering from subacute left spatial neglect, in a randomized, double-blind, sham-controlled design, which also included a control group of neglect patients without stimulation. The results showed a 37% improvement in the spontaneous everyday behaviour of the neglect patients after the repeated application of continuous theta burst stimulation. Remarkably, the improvement persisted for at least 3 weeks after stimulation. The amelioration of spatial neglect symptoms in the activities of daily living was also generally accompanied by significantly better performance in the neuropsychological tests. No significant amelioration in symptoms was observed after sham stimulation or in the control group without stimulation. These results provide Class I evidence that continuous theta burst stimulation is a viable add-on therapy in neglect rehabilitation that facilitates recovery of normal everyday behaviour.
Brain 07/2012; · 9.46 Impact Factor
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ABSTRACT: Improvements of language production in aphasic patients have been reported following repeated 1-Hz transcranial magnetic stimulation over the nondamaged right hemisphere. Most studies examined aphasic patients in the chronic phase. The effect of transcranial magnetic stimulation application in acute or subacute patients has not been systematically studied. We aimed to evaluate whether continuous theta burst stimulation, an inhibitory protocol with a shorter application time than the common 1-Hz protocol, is able to improve naming performance in aphasic patients in different poststroke phases.
Eighteen right-handed aphasic patients performed a picture naming task and a language independent alertness test before and after the application of theta burst stimulation over the intact right Broca's homologue localized by the 10-20 electroencephalogram system in a randomized, sham-controlled, crossover trial.
We found that naming performance was significantly better, and naming latency was significantly shorter, after theta burst stimulation than after the sham intervention. Patients who responded best were in the subacute phase after stroke.
This setting with the short theta burst stimulation application time and the simple stimulation localization procedure is suitable for clinical purposes.
Stroke 05/2012; 43(8):2175-9. · 5.73 Impact Factor
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Cortex 04/2012; 48(4):504-8. · 6.08 Impact Factor
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ABSTRACT: Neglect is defined as the failure to attend and to orient to the contralesional side of space. A horizontal bias towards the right visual field is a classical finding in patients who suffered from a right-hemispheric stroke. The vertical dimension of spatial attention orienting has only sparsely been investigated so far. The aim of this study was to investigate the specificity of this vertical bias by means of a search task, which taps a more pronounced top-down attentional component. Eye movements and behavioural search performance were measured in thirteen patients with left-sided neglect after right hemispheric stroke and in thirteen age-matched controls. Concerning behavioural performance, patients found significantly less targets than healthy controls in both the upper and lower left quadrant. However, when targets were located in the lower left quadrant, patients needed more visual fixations (and therefore longer search time) to find them, suggesting a time-dependent vertical bias.
Neuropsychologia 04/2011; 49(9):2369-74. · 3.64 Impact Factor
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ABSTRACT: The traditional view of a predominant inferior parietal representation of gestures has been recently challenged by neuroimaging studies demonstrating that gesture production and discrimination may critically depend on inferior frontal lobe function. The aim of the present work was therefore to investigate the effect of transient disruption of these brain sites by continuous theta burst stimulation (cTBS) on gesture production and recognition.
Fourteen healthy subjects participated in the study. A repeated measures design was employed with three experimental sessions: baseline (BSL), left inferior parietal (IPL) and inferior frontal (IFG) TBS. Gesture production and recognition was assessed in an off-line approach using a new test of upper limb apraxia (TULIA) and a modified version of postural knowledge test (PKT).
TBS of the left IFG significantly lowered total TULIA scores. The effect was even more prominent when contrasted with IPL than with BSL. However, TBS over either stimulation site did not significantly influence PKT measures.
The interference of the left inferior frontal cTBS with gesture production emphasizes the role this brain region has in the control of gestures.
The study demonstrated that gesture performance is amenable to modulation with TBS.
Clinical neurophysiology: official journal of the International Federation of Clinical Neurophysiology 12/2010; 122(6):1197-202. · 3.12 Impact Factor
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ABSTRACT: Hemispatial neglect - defined as the failure to attend, explore, and act upon the contralesional side of space - is a frequent and disabling neurological syndrome. Interhemispheric rivalry is considered as a major pathophysiological mechanism underlying hemispatial neglect. According to this account, the contralesional, intact hemisphere undergoes a pathological hyperactivity due to a deficient transcallosal inhibition from the damaged hemisphere. This model offers a framework for possible therapeutic interventions with repetitive transcranial magnetic stimulation (rTMS), i.e. a reduction of the pathological hyperactivity with a rTMS protocol that has lasting inhibitory effects. In the present work, we will first review evidence for the interhemispheric rivalry account coming from animals and humans. We will then describe studies showing the possibility to perturb and to restore interhemispheric balance in healthy subjects as a proof of concept for therapeutic rTMS application. Finally, we will consider studies applying rTMS as a therapeutic approach in hemispatial neglect. We conclude that rTMS is a promising approach to reduce the interhemispheric imbalance in neglect patients and to ameliorate symptoms. Newly developed protocols such as Theta Burst Stimulation (TBS) - with short stimulation times and long offline effects - seem to be particularly convenient. However, future studies should assess stimulation effects not only in clinical testing, but also on disability, considering combination with traditional therapies as well.
Restorative neurology and neuroscience 01/2010; 28(4):499-510. · 2.51 Impact Factor
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ABSTRACT: After a lesion of the posterior parietal cortex (PPC), the perception of a contra-lesional stimulus in presence of a simultaneous, ipsilesional stimulus may be impaired, a phenomenon referred to as visual extinction. In the present study, visual extinction was transiently induced in healthy subjects by interfering with the function of the right PPC by means of continuous theta burst stimulation (TBS). We investigated to which extent the horizontal and vertical position of visual stimuli influenced the extinction rate. A single TBS train over the right PPC induced a significant increase of left visual extinctions of at least 30 min. Left visual extinction rate was higher when the left sided visual stimulus was presented at a more eccentric position on the horizontal axis (irrespective of right sided visual stimulus position) and in the lower part of the visual field. The results are discussed within the framework of current explanatory models and of putative inter- and intrahemispheric mechanisms directing visuospatial attention.
Neuroscience 09/2009; 164(4):1609-14. · 3.38 Impact Factor
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ABSTRACT: Visual neglect is a frequent disability in stroke and adversely affects mobility, discharge destination, and length of hospital stay. It is assumed that its severity is enhanced by a released interhemispheric inhibition from the unaffected toward the affected hemisphere. Continuous theta burst transcranial magnetic stimulation (TBS) is a new inhibitory brain stimulation protocol which has the potential to induce behavioral effects outlasting stimulation. We aimed to test whether parietal TBS over the unaffected hemisphere can induce a long-lasting improvement of visual neglect by reducing the interhemispheric inhibition.
Eleven patients with left-sided visual neglect attributable to right hemispheric stroke were tested in a visual perception task. To evaluate the specificity of the TBS effect, 3 conditions were tested: 2 TBS trains over the left contralesional posterior parietal cortex, 2 trains of sham stimulation over the contralesional posterior parietal cortex, and a control condition without any intervention. To evaluate the lifetime of repeated trains of TBS in 1 session, 4 trains were applied over the contralesional posterior parietal cortex.
Two TBS trains significantly increased the number of perceived left visual targets for up to 8 hours as compared to baseline. No significant improvement was found with sham stimulation or in the control condition without any intervention. The application of 4 TBS trains significantly increased the number of perceived left targets up to 32 hours.
The new approach of repeating TBS at the same day may be promising for therapy of neglect.
Stroke 07/2009; 40(8):2791-6. · 5.73 Impact Factor
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ABSTRACT: Interhemispheric imbalance is discussed as a pathophysiological mechanism in visuospatial neglect. It is suggested that after a lesion of the right hemisphere the mutual transcallosal inhibition is impaired, resulting in an increased activity of the left hemisphere. We investigated the interhemispheric balance of attention in healthy subjects by using a free visual exploration task and by interfering with the neural activity of the posterior parietal cortex (PPC) of either hemisphere using an inhibitory transcranial magnetic stimulation routine with theta burst stimulation (TBS). Subjects explored colour photographs of real-life scenes presented on a computer screen under four conditions: (i) without TBS; (ii) after TBS over the right PPC; (iii) after TBS over the left PPC; and (iv) after TBS over the right PPC and, after the first half of the task, over the left PPC. Eye movements were measured, and distribution of mean cumulative fixation duration over screen halves was analyzed. TBS over the right PPC resulted in a significant rightward shift of mean cumulative fixation duration of approximately 30 min. The shift could be reversed when a subsequent train of TBS was applied over the left PPC. However, left PPC stimulation alone had no significant effect on visual exploration behaviour. The present study shows that the effect of TBS on the PPC depends on which hemisphere is stimulated and on the state of the contralateral homologue area. These findings are in accordance with the predictions of the interhemispheric rivalry model in neglect.
European Journal of Neuroscience 04/2009; 29(6):1271-6. · 3.63 Impact Factor
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ABSTRACT: Based on neurophysiological findings and a grid to score binocular visual field function, two hypotheses concerning the spatial distribution of fixations during visual search were tested and confirmed in healthy participants and patients with homonymous visual field defects. Both groups showed significant biases of fixations and viewing time towards the centre of the screen and the upper screen half. Patients displayed a third bias towards the side of their field defect, which represents oculomotor compensation. Moreover, significant correlations between the extent of these three biases and search performance were found. Our findings suggest a new, more dynamic view of how functional specialisation of the visual field influences behaviour.
Vision research 12/2008; 49(2):237-48. · 2.29 Impact Factor
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ABSTRACT: The right posterior parietal cortex (PPC) is critically involved in visual exploration behaviour, and damage to this area may lead to neglect of the left hemispace. We investigated whether neglect-like visual exploration behaviour could be induced in healthy subjects using theta burst repetitive transcranial magnetic stimulation (rTMS). To this end, one continuous train of theta burst rTMS was applied over the right PPC in 12 healthy subjects prior to a visual exploration task where colour photographs of real-life scenes were presented on a computer screen. In a control experiment, stimulation was also applied over the vertex. Eye movements were measured, and the distribution of visual fixations in the left and right halves of the screen was analysed. In comparison to the performance of 28 control subjects without stimulation, theta burst rTMS over the right PPC, but not the vertex, significantly decreased cumulative fixation duration in the left screen-half and significantly increased cumulative fixation duration in the right screen-half for a time period of 30 min. These results suggest that theta burst rTMS is a reliable method of inducing transient neglect-like visual exploration behaviour.
European Journal of Neuroscience 05/2008; 27(7):1809-13. · 3.63 Impact Factor
