Transient and selective suppression of neural activity with infrared light

Abstract

Analysis and control of neural circuitry requires the ability to selectively activate or inhibit neurons. Previous work showed that infrared laser light selectively excited neural activity in endogenous unmyelinated and myelinated axons. However, inhibition of neuronal firing with infrared light was only observed in limited cases, is not well understood and was not precisely controlled. Using an experimentally tractable unmyelinated preparation for detailed investigation and a myelinated preparation for validation, we report that it is possible to selectively and transiently inhibit electrically-initiated axonal activation, as well as to both block or enhance the propagation of action potentials of specific motor neurons. Thus, in addition to previously shown excitation, we demonstrate an optical method of suppressing components of the nervous system with functional spatiotemporal precision. We believe this technique is well-suited for non-invasive investigations of diverse excitable tissues and may ultimately be applied for treating neurological disorders.

Conduction block of mammalian myelinated nerve by local cooling to 15–30°C after a brief heating

“…The length of the heated nerve was 15 mm in the previous study (Klumpp and Zimmermann 1980) but was only 9 mm in our study. In addition, a recent study in rats showed that the sciatic nerve could be blocked by increasing local temperature about 9°C from room temperature using very focused (Ͻ0.1 mm) infrared laser (Duke et al 2013). The effect of heating or cooling different lengths of nerve needs to be investigated.…”

Action potential block in neurons by infrared light

“…[1][2][3][4][5] While the mechanisms behind INS are not fully understood, it is dependent on the fast thermal gradient induced by the infrared exposure 5 and is characterized by rapid increase in intracellular calcium. 6,7 Preliminary reports have demonstrated that SILPs may also block APs; 4,8,9 however, these reports measured reduced electrical activity in neuron networks downstream of repeated SILP exposures and may report indirect effects of INS on inhibitory neurons. Additionally, infrared radiation may cause AP block directly, which we term infrared neural inhibition (INI).…”

Synergistic combination of near-infrared irradiation and targeted gold nanoheaters for enhanced photothermal neural stimulation

“…On the other hand, infrared neural stimulation (INS) enables us to control neural activities by delivering infrared light energy into the target neural cells without genetic modification [2,6,9,10]. While the underlying mechanism is not clear yet, it has been hypothesized that infrared light can excite or inhibit neural cells depending on the thermal gradient at the cell membrane [4,6,[11][12][13][14]. However, conventional INS incorporating infrared wavelength in the range of 1450 -2200 nm has been in trouble with tissue damage due to strong water absorption [15].…”