Design and characteristics of holographic neural photo-stimulation systems

Abstract

Computer-generated holography is an emerging technology for stimulation of neuronal populations with light patterns. A holographic photo-stimulation system may be designed as a powerful research tool or a compact neural interface medical device, such as an optical retinal prosthesis. We present here an overview of the main design issues including the choice of holographic device, field-of-view, resolution, physical size, generation of two- and three-dimensional patterns and their diffraction efficiency, choice of algorithms and computational effort. The performance and characteristics of a holographic pattern stimulation system with kHz frame rates are demonstrated using experimental recordings from isolated retinas.

Holographic optogenetic stimulation of patterned neuronal activity for vision restoration

“…1d, rise and fall times of B50 ms). This ultra-high rate (2,000 holograms per second) can be used for multiplexing large numbers of different holograms, or alternatively for averaging out holographic noise from a single hologram 28 and/or to project multiple different colours for excitation of multiple optogenetic probes 2,22 .…”

“…The design and characteristics of holographic stimulation systems, including the one used here were previously described and analysed in-depth in Golan et al 22 Our optical set-up is based on a blue diode-pumped solid state (DPSS) laser (473 nm; VA-I-N-473, 50 mW, Viasho, China). Beam expansion is performed by a 1:4 Galilean telescope.…”

“…Binary holograms were calculated by the 'Randomal Superposition' method (SR) 42 (which works well for non-symmetric patterns 22 ). The target stimulation pattern was multiplied by a random phase mask, then inverse Fourier transformed.…”

“…Diffractive wavefront shaping techniques including computergenerated holography (CGH) and generalized phase contrast are an emerging tool for dynamic patterned photo-excitation [20][21][22][23] that were shown to allow structured two-(2D) and threedimensional (3D) excitation of dendritic arbors 20,24 and neurons 25 using neurotransmitter photolysis as well as twophoton optogenetic stimulation of several neurons in brain slices 26 . The principle advantage of CGH systems 22,23 is that they naturally combine the high intensity, efficiency and resolution that are characteristic of sequential laser deflection methods (such as acousto-optical deflectors) with the capacity for scan-less simultaneous parallel illumination of multiple locations of microdisplay array projectors, but without their respective limitations.…”

“…The principle advantage of CGH systems 22,23 is that they naturally combine the high intensity, efficiency and resolution that are characteristic of sequential laser deflection methods (such as acousto-optical deflectors) with the capacity for scan-less simultaneous parallel illumination of multiple locations of microdisplay array projectors, but without their respective limitations. That is, unlike digital mirrors and other array microdisplays, CGH divides power among the 'on' stimulation pattern and avoids the massive inefficiency resulting from blocking the light to the large proportion of 'off' pixels (typically 4 490%), and unlike laser deflectors, the patterns are projected simultaneously rather than sequentially, and are thus independent of (the relatively long) dwell times.…”