Reversibility of visual field defects through induction of brain plasticity: vision restoration, recovery and rehabilitation using alternating current stimulation

For decades visual field defects were considered irreversible because it was thought that in the visual system the regeneration potential of the neuronal tissues is low.Nevertheless,there is always some potential for partial recovery of the visual field defect that can be achieved through induction of neuroplasticity.Neuroplasticity refers to the ability of the brain to change its own functional architecture by modulating synaptic efficacy.It is maintained throughout life and just as neurological rehabilitation can improve motor coordination,visual field defects in glaucoma,diabetic retinopathy or optic neuropathy can be improved by inducing neuroplasticity.In ophthalmology many new treatment paradigms have been tested that can induce neuroplastic changes,including non-invasive alternating current stimulation.Treatment with alternating current stimulation(e.g.,30 minutes,daily for 10 days using transorbital electrodes and^10 Hz)activates the entire retina and parts of the brain.Electroencephalography and functional magnetic resonance imaging studies revealed local activation of the visual cortex,global reorganization of functional brain networks,and enhanced blood flow,which together activate neurons and their networks.The future of low vision is optimistic because vision loss is indeed,partially reversible.

Cortico–subcortical spatiotemporal dynamics in Parkinson’s disease can be modulated by transcranial alternating current stimulation

Objective:We investigated changes in cortico–subcortical spatiotemporal dynamics to explore the treatment mechanisms oftranscranial alternating current stimulation(tACS)in patientswith Parkinson’s disease(PD).Methods:Resting-state functional magnetic resonance imaging(rs-fMRI)data were collected from 20 patients with PD and 20 normal controls(NC).Each patient with PD received successivemultidisciplinary intensive rehabilitation treatment and tACStreatment over a one-year interval.Individual functional brain network mapping and co-activation pattern(CAP)analysis were performed to characterize cortico–subcortical dynamics.Results:The same tACS electrode placement stimulated different proportions of functional brain networks across the participants.CAP analysis revealed that the visual network,attentional network,and default mode network co-activated with the thalamus,accumbens,and amygdala,respectively.The pattern characterized by thede-activation of the visual network and the activation of the thalamus showed a significantly low amplitude in the patients with PD than inNCs,and this amplitude increased after tACS treatment.Furthermore,the co-occurrence of cortico–subcortical CAPs was significantly higherin patients with PD than in NCs and decreased after tACS treatment.Conclusions:This study investigated cortico–subcortical spatiotemporaldynamics in patients with PD and further revealed the tACS treatmentmechanism.These findings contribute to understanding cortico–subcortical dynamics and exploring noninvasive neuromodulationtargets of cortico–subcortical circuits in brain diseases,such as PD,Alzheimer’s disease,and depression.

Protocol on transcranial alternating current stimulation for the treatment of major depressive disorder:a randomized controlled trial

Background:Transcranial alternating current stimulation(tACS)offers a new approach for adult patients with major depressive disorder(MDD).The study is to evaluate the efficacy and safety of tACS treating MDD.Methods:This is an 8-week,double-blind,randomized,placebo-controlled study.Ninety-two drug-naive patients with MDD aged 18 to 65 years will receive 20 daily 40-min,77.5-Hz,15-mA sessions of active or sham tACS targeting the forehead and both mastoid areas on weekdays for 4 consecutive weeks(week 4),following a 4-week observation period(week 8).The primary outcome is the remission rate defined as the 17-item Hamilton depression rating scale(HDRS-17)score≤7 at week 8.Secondary outcomes are the rates of response at weeks 4 and 8 and rate of remission at week 4 based on HDRS-17,the proportion of participants having improvement in the clinical global impression-improvement,the change in HDRS-17 score(range,0-52,with higher scores indicating more depression)over the study,and variations of brain imaging and neurocognition from baseline to week 4.Safety will be assessed by vital signs at weeks 4 and 8,and adverse events will be collected during the entire study.Discussion:The tACS applied in this trial may have treatment effects on MDD with minimal side effects.Trial registration:Chinese Clinical Trial Registry,ChiCTR1800016479;http://www.chictr.org.cn/showproj.aspx?proj=22048.

Non-invasive electrical brain stimulation:from acute to late-stage treatment of central nervous system damage

Non-invasive brain current stimulation（NIBS） is a promising and versatile tool for inducing neuroplasticity,protection and functional rehabilitation of damaged neuronal systems.It is technically simple,requires no surgery,and has significant beneficial effects.However,there are various technical approaches for NIBS which influence neuronal networks in significantly different ways.Transcranial direct current stimulation（t DCS）,alternating current stimulation（ACS） and repetitive transcranial magnetic stimulation（r TMS） all have been applied to modulate brain activity in animal experiments under normal and pathological conditions.Also clinical trials have shown that t DCS,r TMS and ACS induce significant behavioural effects and can – depending on the parameters chosen – enhance or decrease brain excitability and influence performance and learning as well as rehabilitation and protective mechanisms.The diverse phaenomena and partially opposing effects of NIBS are not yet fully understood and mechanisms of action need to be explored further in order to select appropriate parameters for a given task,such as current type and strength,timing,distribution of current densities and electrode position.In this review,we will discuss the various parameters which need to be considered when designing a NIBS protocol and will put them into context with the envisaged applications in experimental neurobiology and medicine such as vision restoration,motor rehabilitation and cognitive enhancement.