The contribution of non-invasive brain stimulation techniques in the experimental treatment of cognitive and neuropsychiatric symptoms in Vascular Dementia

Repetitive Transcranial magnetic stimulation (rTMS) and transcranial Direct Current Stimulation (tDCS) are non-invasive and painless stimulation techniques able not only to explore cortical circuits and related neurochemical pathways in dementing illnesses but also to induce cortical plasticity with a potential therapeutic and rehabilitative purposes. Several studies, although methodologically heterogeneous and most of them open-label in design, have shown that specific paradigms of stimulation might improve cognitive performance, thus possibly becoming an alternative to conventional neuroleptic therapy for psychiatric symptoms of dementia. In Alzheimer’s disease these effects are probably mediated by compensatory mechanisms supporting the residual abilities. The efficacy can be maximised by selecting patients on the basis of putative neurophysiological markers. Although less is known, similar plastic phenomena are invoked in Vascular Dementia (VaD). High frequency rTMS over the left dorsolateral prefrontal cortex improved executive performance in patients with subcortical ischemic vascular disease and the effect has been hypothesized to be due to an indirect activation of dopaminergic neurons in the mesencephalon and the noradrenergic and serototoninergic neurons in the brainstem. Moreover, rTMS was effective in alleviating also symptoms of vascular depression. More recently, the restorative effects of these techniques on cognitive ability have been observed in murine model of VaD probably through the neurotrophin release, such as the Brain Derived Neurotrophic Factor (BDNF) and the induction of hyppocampal glutamate-mediated synaptic plasticity.