Simulation-informed low-current anodal tDCS accelerates early motor recovery after photochemically induced cortical stroke in rats

Animal transcranial direct current stimulation (tDCS) studies typically use intensities exceeding clinical levels, and the off-line behavioral effects of weak electric fields in rodents remain unclear. We examined whether repeated anodal tDCS, calibrated by electric-field simulation to approximate human-equivalent weak fields, facilitates motor recovery after focal photothrombotic ischemic stroke (PIT) in rats. Simulation estimated that 50 μA produced a maximum field of ∼1.96 V/m in the targeted motor cortex, matching clinically relevant intensities. Under isoflurane anesthesia, rats received anodal tDCS at 50 μA, 250 μA, or 1 mA (5 min/day, 5 days/week, 2 weeks), or sham; motor recovery was assessed weekly by beam-walking for 4 weeks. A linear mixed-effects model revealed significant time, group, and time × group effects. The 50 μA group outperformed the PIT group at 1 week, and the 1 mA group at 2 weeks, with no differences thereafter. Low-current tDCS accelerates early post-stroke motor recovery, supporting weak-field neuromodulation.