Noninvasive Brain Stimulation Protects Cognitive Impairment in i.c.v. STZ-Injected Rats: Role of Adult Neurogenesis

In Alzheimer's-like dementia, neurodegeneration and synaptic dysfunction are known to be the critical players in explaining cognitive impairment. Adult neurogenesis, normally a chronic and quiet process, is explained to have potential in the field of Alzheimer's therapy. Previous research on noninvasive brain stimulation showed that by controlling the pattern of stimulation externally, we can regulate/entrain neuronal activity, possibly altering the structural changes at the circuit level. However, literature investigating whether noninvasive brain stimulation could hold any potential to initiate the process of adult neurogenesis is scarce. In the present study, with the use of behavioural, microscopic and biochemical tools, we found that extremely low-frequency magnetic field at an intensity of 17.96 μT with a sinusoidal wave of 50 Hz for 2 h daily for a period of 2 weeks in a streptozotocin-induced animal model of sporadic Alzheimer's disease can cause improvement in spatial and reference memory, influencing their swimming strategy in the water maze. This is caused by stimulation in immature neural pluripotent stem cells, with additional redox balance and mitigation of glial aggravation in brain areas like the olfactory bulb, prefrontal cortex and hippocampus. These changes were accompanied by neuroprotection, as observed in the granular layer of dentate gyrus. Taken together, the present study explains a plausible mechanism of action on the protection of neurodegeneration in Alzheimer's disease through noninvasive brain stimulation.