Ph.D Thesis

Ph.D StudentGoldshuv Ezra Nurit
SubjectEEG-Biofeedback Treatment for Unilateral Spatial Neglect: a
Behavioural and Functional Imaging study
DepartmentDepartment of Medicine
Supervisors PROFESSOR EMERITUS Hillel Pratt
DR. Nachum Soroker
Full Thesis textFull thesis text - English Version


Unilateral Spatial Neglect (USN) is a common disorder among stroke patients, characterized by the failure of salient objects and events occurring in the contralesional space to attract attention. USN patients suffer from additional cognitive and physical deficits and slower rehabilitation. Despite the dramatic impact of USN on the functional prognosis of stroke patients, most rehabilitation strategies fail to show a consistent benefit in reduction of USN-related disability. This stresses the importance of developing theory-driven treatments targeted at the specific mechanisms underlying USN.

Electrophysiological studies have revealed a widespread perilesional hypoarousal associated with physiological dysfunction in USN. Cortical excitation induced by external neuromodulatory methods, such as repetitive transcranial magnetic stimulation (rTMS) and transcranial direct current stimulation (tDCS), are known to diminish the parietal inter-hemispheric imbalance in USN patients. Corbetta (2005) showed that the Superior Parietal Lobe (SPL) is fundamental in perilesional reorganization in USN-amelioration. Based on these findings, we set to evaluate the effectiveness of electroencephalogram biofeedback (EEG-BF), an internal neuromodulatory intervention, in inducing cortical excitation at the hypoaroused and mal-functioning perilesional area of the SPL, and in enhancing USN rehabilitation. This theory-based SHAM-controlled EEG-BF study is a first step forward into the field of USN-rehabilitation by neuromodulation.

Twenty-one USN-patients were screened for neglect with conventional paper-and-pencil tests and randomly assigned to a series of 10 daily EEG-BF or SHAM interventions. Performance in a computerized visual search task [Starry Night Test (SNT)], before and after each intervention, was evaluated. Post-intervention assessment as well as a one-month follow-up measurement were administered to determine the immediate and long-lasting effect of the intervention.

EEG-BF was found to have neuromodulatory effects. In those patients who successfully performed the neurofeedback training the effect was sustained, as indicated by increased resting state beta/theta amplitudes, as well as decreased parietal hemispheric differences across interventions. As expected, patients improved performance in the SNT and USN-assessment tests. Crucially, behavioral improvement was associated with EEG-BF treatment, as indicated by correlations between enhanced behavioral performance in the SNT, reduced hemispheric differences, and beta/theta ratio increment during resting state EEG.

In order to facilitate future identification of the USN-population that would benefit from EEG-BF treatments, we associated the success of our patients with characteristics such as clinical profile and structural lesion analysis. We found that the impact of structural damage in the inferior parietal lobe (IPL) was negatively correlated with the ability to up-regulate beta/theta amplitude at resting state following EEG-BF. This implies a possible role of the IPL in sustaining the effects of EEG-BF. We conclude that patients with small or no lesions in the IPL may benefit the most from EEG-BF.

To summarize, we designed and tested the attempt to induce cortical arousal via EEG-BF for the treatment of USN. We show that EEG-BF, applied over the SPL can enhance USN-rehabilitation, and that lesion location may predict the success of the treatment. Suggestions for future studies are offered, as we believe that the true potential of EEG-BF in USN-rehabilitation may be revealed by additional steps in the direction marked here.