Non-invasive Brain Stimulation on Functional Capacity in Prefrail Older Adults

The tDCS will be performed anodically (a-tDCS), and for 24 sessions, 3 days a week. The electrodes will be mounted on a neoprene helmet, in accordance with the International Standard 10-20 EEG System, for optimal targeting of the primary motor cortex M1. It will be a type of unihemispheric application, in which the anode will be located in the primary motor cortex (M1), and the cathode located in the orbitofrontal cortex contralateral to the anode. The treatment parameters will be: stimulation time of 20 minutes; intensity of 2mA, current rise-fall time at the beginning and end of stimulation of 30 seconds. They will then perform the therapeutic exercise protocol explained above.

The instrumentation will be the same as in the actual tDCS intervention, but the device will be programmed to increase the intensity from 0 to 2 mA progressively during the first 30 seconds and then cease to provide the patient with the initial itchy sensation on the skin, similar to the real application. They will then perform the therapeutic exercise protocol explained above.

24 sessions will be applied, 3 days a week. The patient will be placed standing (with an ad-hoc designed assistance system) in front of a mirror (located at waist height) and a height-adjustable screen (from waist to caudal) where a video of real legs running on a treadmill will be projected. In order for the participant to feel the projected legs as their own, people with different body sizes will have been previously recorded running to have recordings with legs of different size and length. Each session will last 20 minutes. They will then perform the therapeutic exercise protocol explained above.

The instrumentation of the participants will be the same as in the intervention with virtual running. However, the projection will consist of a series of videos of landscapes in which no type of human or animal movement will appear in order not to stimulate the motor areas of the brain. They will then perform the therapeutic exercise protocol explained above.