Bocci Tommaso, Nasini Francesco, Caleo Matteo, Restani Laura, Barloscio Davide, Ardolino Gianluca, Priori Alberto, Maffei Lamberto, Nardi Marco, Sartucci Ferdinando
Section of Neurophysiopathology, Department of Clinical and Experimental Medicine, University of Pisa, Pisa, Italy.
Clinical Center for Neurotechnologies, Neuromodulation, and Movement Disorders, Fondazione IRCCS Ca'Granda Ospedale Maggiore Policlinico, Milan, Italy.
Front Behav Neurosci. 2018 May 29;12:109. doi: 10.3389/fnbeh.2018.00109. eCollection 2018.
Amblyopia is a neurodevelopmental disorder characterized by visual acuity and contrast sensitivity loss, refractory to pharmacological and optical treatments in adulthood. In animals, the corpus callosum (CC) contributes to suppression of visual responses of the amblyopic eye. To investigate the role of interhemispheric pathways in amblyopic patients, we studied the response of the visual cortex to transcranial Direct Current Stimulation (tDCS) applied over the primary visual area (V1) contralateral to the "lazy eye." Visual acuity (logMAR) was assessed before (T), immediately after (T) and 60' following the application of cathodal tDCS (2.0 mA, 20') in 12 amblyopic patients. At each time point, Visual Evoked Potentials (VEPs) triggered by grating stimuli of different contrasts (K90%, K20%) were recorded in both hemispheres and compared to those obtained in healthy volunteers. Cathodal tDCS improved visual acuity respect to baseline ( < 0.0001), whereas sham polarization had no significant effect. At T, tDCS induced an inhibitory effect on VEPs amplitudes at all contrasts in the targeted side and a facilitation of responses in the hemisphere ipsilateral to the amblyopic eye; compared with controls, the facilitation persisted at T for high contrasts (K90%; Holm-Sidak method, < 0.001), while the stimulated hemisphere recovered more quickly from inhibition (Holm-Sidak method, < 0.001). tDCS is a promising treatment for amblyopia in adults. The rapid recovery of excitability and the concurrent transcallosal disinhibition following perturbation of cortical activity may support a critical role of interhemispheric balance in the pathophysiology of amblyopia.
弱视是一种神经发育障碍，其特征为视力和对比敏感度丧失，成年后对药物和光学治疗无效。在动物中，胼胝体（CC）有助于抑制弱视眼的视觉反应。为了研究半球间通路在弱视患者中的作用，我们研究了视觉皮层对经颅直流电刺激（tDCS）的反应，该刺激应用于与“弱视眼”对侧的初级视觉区（V1）。在12名弱视患者中，在应用阴极tDCS（2.0 mA，20分钟）之前（T）、之后立即（T）以及之后60分钟评估视力（logMAR）。在每个时间点，记录由不同对比度（K90%，K20%）的光栅刺激触发的视觉诱发电位（VEP），并在两个半球中进行记录，并与健康志愿者获得的结果进行比较。阴极tDCS相对于基线改善了视力（<0.0001），而假极化没有显著影响。在T时，tDCS在目标侧对所有对比度的VEP振幅产生抑制作用，并促进弱视眼同侧半球的反应；与对照组相比，在T时，高对比度（K90%；Holm-Sidak法<0.001）的促进作用持续存在，而受刺激半球从抑制中恢复得更快（Holm-Sidak法<0.001）。tDCS是一种有前景的成人弱视治疗方法。皮质活动扰动后兴奋性的快速恢复和同时发生的胼胝体去抑制可能支持半球间平衡在弱视病理生理学中的关键作用。
