Klinische Neurophysiologie 2012; 43 - P147
DOI: 10.1055/s-0032-1301697

Photobiomodulation of the Human Cortex Using Infrared Laser Stimulation

L Chaieb 1, A Antal 1, W Paulus 1
  • 1Department of Clinical Neurophysiology, Georg-August University, Göttingen

Application of low level laser therapy (LLLT) for wound healing, inflammation and chronic pain relief has now widened to include neurological disorders such as stroke, neurodegenerative diseases and the treatment of traumatic brain disorders (Hashmi et al, 2010).

We applied LLLT at a wavelength of 810nm to 12 participants (5 male; age range: 23-31 years) for 10minutes to the primary motor cortex (M1). Single-pulse and paired-pulse measures of transcranial magnetic stimulation (TMS) were used to evaluate levels of cortical excitability. Initial effects of LLLT were first ascertained using single-pulse TMS before and after LLLT stimulation (baseline, 0, 5, 10, 15, 20, 25, 30, and 60minutes). Other TMS measures included long-interval cortical inhibition (LICI), short-interval cortical inhibition (SICI) and recruitment curves before LLLT and at 0, 30, 60 and 90 minutes poststimulation. We applied LLLT during the execution of a variant of the serial reaction time task (SRTT), a measure of implicit motor learning. Participants completed a questionnaire at the end of the study regarding their perceived effect of the LLLT stimulation, including any adverse side effects.

Data suggest that a 10minute application of LLLT in the infrared range causes inhibition of mean MEP amplitudes up to 20-40% compared to sham stimulation, for up to 1hour poststimulation. LICI showed a tendency toward a decrease in MEP amplitudes at 150ms. For the SRTT, a significant difference was observed between males and females for REACTION TIME in the LLLT condition; females being significantly faster poststimulation.

Results suggest that LLLT stimulation over the human cortex has robust effects on levels of cortical excitability and implicit motor learning. Participants reported feeling the cutaneous sensation of the laser stimulation during the experimental sessions which raises an issue with regard to blinding. This study suggests that LLLT has a promising future role in cortical stimulation.