Driving Oscillatory Dynamics: Neuromodulation for Recovery After Stroke

Abstract

Stroke is a leading cause of death and disability worldwide, with limited treatments being available. However, advances in optic methods in neuroscience are providing new insights into the damaged brain and potential avenues for recovery. Direct brain stimulation has revealed close associations between mental states and neuroprotective processes in health and disease, and activity-dependent calcium indicators are being used to decode brain dynamics to understand the mechanisms underlying these associations. Evoked neural oscillations have recently shown the ability to restore and maintain intrinsic homeostatic processes in the brain and could be rapidly deployed during emergency care or shortly after admission into the clinic, making them a promising, non-invasive therapeutic option. We present an overview of the most relevant descriptions of brain injury after stroke, with a focus on disruptions to neural oscillations. We discuss the optical technologies that are currently used and lay out a roadmap for future studies needed to inform the next generation of strategies to promote functional recovery after stroke.

Keywords: brain oscillations; neuromodulation; neuroprotection; optical technologies; stroke.

Figure 1

Simplified schema of hemispheric changes to neural oscillatory power following stroke in human and animal models. Previously described alterations to the power of brain oscillations in the contralateral and ipsilesional hemispheres of human patients (top) and mice (bottom) post-stroke. δ = delta, α = alpha, β = beta, γ = gamma frequency bands. Acute refers to <7 days after stroke, and chronic refers to >6 months after stroke.

Figure 2

Tools for modulating brain activity post-stroke in human and animal models. Current invasive and non-invasive brain stimulation, sensory stimulation, and optogenetic tools that are used to modulate brain oscillations. Applications are shown on animal models in the inner circle, with the corresponding applications on human patients in the outer part of the circle. The figure in the bottom left represents a combination of current methods and integrates them into a non-invasive closed-loop design that could be considered for future research. DBS, deep brain stimulation; TES, transcranial electric stimulation; TMS, transcranial magnetic stimulation.