Photoactivation of neurons by laser-generated local heating

TL;DR

This paper introduces a laser-based thermal method for precise, genetic-free neuron activation, enabling targeted and repeatable stimulation of neurons through localized heating without genetic modification.

Contribution

The study presents a novel photothermal technique for neuron activation that does not require genetic expression of photosensitive proteins, expanding options for neural circuit analysis.

Findings

Achieved reliable neuron activation with 70-90% success rate.

Demonstrated activation in Hirudo verbana neurons and Xenopus oocytes.

Allowed multiple pulses with minimal cellular property changes.

Abstract

We present a method for achieving temporally and spatially precise photoactivation of neurons without the need for genetic expression of photosensitive proteins. Our method depends upon conduction of thermal energy via absorption by a dye or carbon particles and does not require the presence of voltage-gated channels to create transmembrane currents. We demonstrate photothermal initiation of action potentials in Hirudo verbana neurons and of transmembrane currents in Xenopus oocytes. Thermal energy is delivered by focused 50 ms, 650 nm laser pulses with total pulse energies between 250 and 3500 \muJ. We document an optical delivery system for targeting specific neurons that can be expanded for multiple target sites. Our method achieves photoactivation reliably (70 - 90% of attempts) and can issue multiple pulses (6-9) with minimal changes to cellular properties as measured by intracellular recording. Direct photoactivation presents a significant step towards all-optical analysis of neural circuits in animals such as Hirudo verbana where genetic expression of photosensitive compounds is not feasible.