Behavioral Study of Effects of Low-Level Light Therapy on Mood and Reaction Time

Administration of left LLLT consists of applying light of a specific wavelength (1064 nanometers) using a laser diode, the CG-5000 high density laser (Cell Gen Therapeutics, LLC). Left LLLT will target the left forehead. The diameter parameters of stimulation are the same that showed psychologically beneficial effects in Schiffer et al. (2009). At the power level described, the energy emitted by the CG-5000 at this setting is one quarter of the skin MPE (0.250 W/cm2), exposure to it is not deemed harmful to tissue, and it causes no detectable physical damage and negligible heat.

The task will consist of a modified dot-probe paradigm. A pair of stimuli depicting a negative word and a neutral word will be presented, randomly located to the right and left side of the computer screen. The words will be presented for 1000 ms. The words will then disappear and a dot-probe will appear in the center of the screen location of one of the words (i.e., O or Q). This probe will appear on the screen until the participant presses one of two response buttons to indicate the identity of the probe. The presentation of the probe will be staggered to maximize attention for the neutral stimulus. Latency and accuracy of the button press responses are recorded by the computer.

Administration of right LLLT consists of applying light of a specific wavelength (1064 nanometers) using a laser diode, the CG-5000 high density laser (Cell Gen Therapeutics, LLC). Right LLLT will target the right forehead. The diameter parameters of stimulation are the same that showed psychologically beneficial effects in Schiffer et al. (2009). At the power level described, the energy emitted by the CG-5000 at this setting is one quarter of the skin MPE (0.250 W/cm2), exposure to it is not deemed harmful to tissue, and it causes no detectable physical damage and negligible heat.

Administration of sham LLLT is designed to resemble active LLLT from the participant's perspective, but uses a dosage markedly below the minimal necessary threshold to elicit a response.