Effects of Transcutaneous Electrical Nerve Stimulation (TENS) to Improve the Cognitive Functions in Older Adults

The subjects in Group A will received TENS (Burst mode, 9 pulses per burst, pulse frequency =160Hz, burst frequency=2Hz, intensity was set to trigger visible muscular twitches). Two 2 x 3 cm electrodes was attached on T1 level with 2 cm from the spine. Previous study has shown that it was effective to improve the cognitive function in subjects with Alzheimer's disease.

The subjects in Group B will received TENS (25Hz, 0.5mA) on the concha of left outer ear. The electrical stimulation was generated by the portable neurostimulator (Nemos®, Cerbomed, Erlangen, Germany) and was delivered by a titanium electrodes positioning on top of a silicon earplug. Previous study has shown that it was effective to improve the Accelerate extinction memory formation and retention in healthy young adults.

The subjects in Group C will receive 30 min sham electrical stimulation on T1 by a placebo-TENS device. The Placebo-TENS was applied by an apparently identical TENS unit. The unit's power indicator light was illuminated, but the unit's electrical circuit had been manually disconnected inside. In order to shape the common mindset, all subjects (except those in the Control group) were informed that they might or might not feel an electrical current, as different stimulation parameters were being applied.