Perspectives: Hemianopia—Toward Novel Treatment Options Based on Oscillatory Activity?

Abstract

Stroke has become one of the main causes of visual impairment, with more than 15 million incidences of first-time strokes, per year, worldwide. One-third of stroke survivors exhibit visual impairment, and most of them will not fully recover. Some recovery is possible, but this usually happens in the first few weeks after a stroke. Most of the rehabilitation options that are offered to patients are compensatory, such as optical aids or eye training. However, these techniques do not seem to provide a sufficient amount of improvement transferable to everyday life. Based on the relatively recent idea that the visual system can actually recover from a chronic lesion, visual retraining protocols have emerged, sometimes even in combination with noninvasive brain stimulation (NIBS), to further boost plastic changes in the residual visual tracts and network. The present article reviews the underlying mechanisms supporting visual retraining and describes the first clinical trials that applied NIBS combined with visual retraining. As a further perspective, it gathers the scientific evidence demonstrating the relevance of interregional functional synchronization of brain networks for visual field recovery, especially the causal role of α and γ oscillations in parieto-occipital regions. Because transcranial alternating current stimulation (tACS) can induce frequency-specific entrainment and modulate spike timing–dependent plasticity, we present a new promising interventional approach, consisting of applying physiologically motivated tACS protocols based on multifocal cross-frequency brain stimulation of the visuoattentional network for visual field recovery.

Vision recovery with perceptual learning and non-invasive brain stimulation: Experimental set-ups and recent results, a review of the literature

“…Post-chiasmatic lesions commonly result in unilateral homonymous hemianopia (HH) affecting about 20% of stroke survivors (Raffin et al, 2020). HH is an impairment of the visual field in the same side for both eyes that involve the entire hemifield.…”

“…Generally, this damage could be caused by a traumatic event, arteriovenous malformation or stroke. Speaking about the latter, there are about 15 million incidences of first-time strokes per year, worldwide, that produce vision impairment (Raffin et al, 2020). Typically, a posterior brain injury results in a visual field loss.…”

The effects of occipital and parietal tDCS on chronic visual field defects after brain injury

“…Even though some logistical problems can be overcome [e.g., home-based multisensory training in ( 16 ) and https://osf.io/jmq86/ for an ongoing clinical trial], the idea of boosting brain plasticity by means of non-invasive brain stimulation (NIBS) to make rehabilitation faster and/or more effective has attracted some attention. Accordingly, visual trainings have been combined with non-invasive transcranial electrical stimulation techniques (tES) such as transcranial Direct Current Stimulation [tDCS; ( 21 , 22 )] or repetitive transorbital alternating current stimulation [rtACS; ( 23 , 24 )].…”