17 Parkinson´s disease patients were randomly assigned to the photobiomodulation group (experimental group).

Intervention: Photobiomodulation was administered using red light-emitting diodes (LEDs) with a 670-nm wavelength in six 1-minute blocks alternating the LEDs between the right and left temples, with a 30-second rest between blocks.

18 Parkinson´s disease patients were randomly assigned to the sham group.

Intervention: Procedures for the sham group were identical as the photobiomodulation one, except that patients received photobiomodulation during only 5 seconds followed by 55 seconds with no treatment (equalling 1/12th of the energy used for the intervention group).

Photobiomodulation was administered using red light-emitting diodes (LEDs) with a 670-nm wavelength (which has proven to penetrate the skull)

The motor portion (part III) Movement Disorders Society-Unified PD Rating Scale. It assesses the motor signs of Parkinson´s disease (minimum and maximum score is 0 and 76 points respectively -the higher score, the higher movement disorder and vice versa-).

The Spanish-validated version of the Short Parkinson's Evaluation Scale (SPES)/Scales for Outcomes in PD (SCOPA). It measures the Parkinson´s disease patients motor function (minimum and maximum score is 0 and 63 points respectively -the higher score, the worse motor function and vice versa-).