Probing neuronal functions with precise and targeted laser ablation in the living cortex: comment

The paper [Optica8, 1559 (2021)OPTIC82334-253610.1364/OPTICA.433562] is devoted to probing neuronal functions by targeted cell ablation in living cortex. It demonstrates the advantage of cell ablation by single high-energy pulses from an amplified femtosecond (fs) laser system, which leaves adjacent structures intact. The single-pulse effects rely on mechanical disruption by laser-induced microcavitation, which goes along with a lack of diffusive collateral damage. In comparison, cell damage by low-energy pulses from fs laser oscillators is shown to be associated with a damage zone with tens of micrometer radius around the targeted cell. The collateral damage is attributed to heat accumulation and diffusion. We demonstrate through numerical simulations of plasma formation and temperature evolution for the experimentally employed irradiation conditions that a large number of free electrons is produced but the temperature rise at focus is only 0.3 K. Therefore, the damage is caused by nonlinear photochemistry and plasma-mediated chemical effects rather than by thermal effects.