The excitation mechanism underlying infrared (IR) neural stimulation is adopted to be mediated by photo-thermal tissue transients. Since many wavelengths are capable of eliciting excitation, the wavelengths to be used should be chosen based on the desired penetration depth in the nerve tissue. It is believed that IR light-induced activation is the result of a brief (about ms) spatio-temporal temperature gradient (dT/dt and dT/dx). Accordingly, short pulses appear very effective in driving neural excitation. As a consequence, the rapid temperature rise induces a transient change in the electrical capacitance of the neuron's plasma membrane, which in turn depolarizes the cell and induces a propagating action potential (AP). Previous work showed that Mid-IR light selectively excited neural activity in myelinated and unmyelinated axons. It is also reported that it is possible to selectively and transiently inhibit electrically-initiated axonal activation, as well as to both selectively block or enhance the propagation of APs of specific motor neurons. The relatively novel technique to obtain near infrared using Light Emitting Diodes (LED) has made the equipment easier to manipulate, more accessible, and easier to operate. LED technology has provided medicine with a tool capable of delivering light deep into the nerve tissues. It was shown that pulsed, Mid-IR lasers investigated as a method to stimulate neural activity are significant benefits of optically stimulating nerves over electrically stimulating, in particular the application of more spatially confined electrochemically safe neural stimulation. Accordingly, by changing IR light source parameters (e.g. pulse width and frequency), one can produce large, brief temperature transients sufficient for stimulation. In the model we use the phenomenon of water absorption of electromagnetic radiation with intra-molecular vibrational transitions in the IR region. The IR band is often subdivided into smaller sections. In this regard, we propose to use short-wave IR (SWIR) electromagnetic radiation with wavelength below 2 microns. Precisely, the wavelength that is most effective to induce neuronal excitation is a division called short-wavelength infrared (SWIR, IR-B DIN), wavelength 1.4-3 µm. We developed several custom-designed pieces of equipment in this study, including a temperature-controlled measuring chamber, a 7W laser source, pulse shaper providing short-wave IR (SWIR) electromagnetic radiation stimulation pulses, multi-electrode recording spiral cuff and CAP amplifier. It was adopted that the induced thermal transients have a highly localized nature and fast temporal dynamics within the particular superficial region of the porcine vagus nerve, resulting in activation patterns with high spatiotemporal resolution. The model propose electrophysiological measurements performed on a vagus nerve removed from Slovenian male Landrace pig weighing about 70 kg, immediatelly after stubbing.
F.04 Increase of the technological level
COBISS.SI-ID: 33496025Sinapsa Neuroscience Conference 2017; http://www.sinapsa.org/SNC17/programme
B.01 Organiser of a scientific meeting
COBISS.SI-ID: 292427520