NON-INVASIVE CONTINUOUS-WAVE LASER NEUROMODULATION THROUGH A WIDE RANGE OF WAVELENGTHS AND POWERS

In the search for a balance between effectiveness and non-invasiveness for stimulation techniques, infrared laser has emerged as a novel and effective tool for neural modulation without genetic modification. Combined with its high spatial and temporal resolution, makes it an attractive non-invasive solution for neuromodulation. We have previously demonstrated that continuous-wave infrared laser at 830nm effectively and non-invasively modulates neural dynamics affecting the action potential and burst waveforms, as well as the firing rate in a reversible manner. We have also identified biophysical candidates for the observed modulation using a conductance-based model, as well as the key role of temperature as source of the effect. Complementing those results, we report here the effect of infrared light stimulation under a wide range of wavelengths 830-1450nm and powers (50mW-500mW) in Lymnaea stagnalis and Carcinus maenas. We observe distinct effects depending on the combination of wavelength and power, including changes in waveform amplitude at specific wavelength and power levels, but not significant at lower values. In addition, we explored the safety limits for this neurotechnology, finding that neuronal damage occurs only at high wavelength and power values. We also demonstrated the different modulatory effects when using activity-dependent stimulation by triggering the lasers at specific phases of the spike and burst generation. This work provides insights not only on the biophysical basis of the observed effect but also the optimal delivery modes to apply, enhance, and further develop this technique. Work funded by PID2024-155923NB-I00, PID2023-149669NB-I00 and CPP2023-010818.