Combined transcranial electrical stimulation (tES) and cognitive training (CT) for cognitive impairment: Evidence...

Cognitive impairment is a serious pathological feature of neuropsychiatric disorders, making the exploration of effective treatments urgent. Recent research shows that combined transcranial electrical stimulation (tES) and cognitive training (CT) can reduce cognitive deficits. This review summarizes studies on neurological disorders that use both clinical patients and rodent models to highlight the underlying neural mechanisms. In patients, this combined approach improves cognitive domains such as attention, working memory, and executive function. Improvements have been observed in patients with mild cognitive impairment (MCI), dementia (e.g., Alzheimer's disease (AD)), Parkinson's disease (PD), stroke, traumatic brain injury (TBI), multiple sclerosis, schizophrenia, attention deficit hyperactivity disorder (ADHD) and depression, as well as in healthy populations. In contrast, studies on the combined intervention are lacking in rodent models of disease. However, tES and CT separately improve spatial learning and memory in AD, TBI, schizophrenia, ADHD, and healthy animals, as well as in models of vascular dementia and cerebral ischemia. The combined intervention regulates and remodels functional connectivity in brain networks, and improves cerebrovascular microcirculation and glutamatergic neurotransmission. Importantly, tES and CT may enhance each other through cooperative and complementary effects. In addition, some studies have reported the limited efficacy or negative outcomes of combined and single interventions, which may be due to suboptimal parameters or techniques that fail to target key pathologies. Future clinical trials should explore tES-CT combination strategies targeting disease-specific brain regions. Furthermore, animal studies must be strengthened to elucidate the potential mechanisms and interactions of tES and CT.