Abstract
Purpose: :
Development and in-vitro implementation of a novel projection/excitation strategy that can be used to selectively control large retinal neuronal populations, with high temporal precision (msec) and efficient use of light power.
Methods: :
Of existing display technologies, digital holographic projection ideally meets these constraints, because the use of phase-modulating spatial light modulators (SLMs) and light diffraction allows an efficient use of input light. Our system directs light from Blue, Green and Red DPSS Lasers onto a Ferroelectric liquid crystal SLM that displays binary holograms. Light patterns were coupled into the camera port of an inverted microscope and projected onto retinas, whose responses were measured using a Multi-Electrode Array (MEA).
Results: :
We demonstrate for the first time responses of a population of retinal ganglion cells to patterns of light holographically projected unto wild-type and ChannerhodopsinII transfected retinas. The neurons exhibit spatially-selective responses and have effective receptive fields. We demonstrate sub-millisecond timescale control over the projected light patterns, multi-wavelength excitation, and computational strategies that eliminate the effect of speckle.
Conclusions: :
High-rate holographic projection was demonstrated as an enabling photo-stimulation modality towards the development of a retina neuro-prosthetic, theoretically capable of eliciting over 1 million spikes per second, with millisecond timing precision. Our system can also be applied in experimental studies of the visual system requiring ultra-high-rate stimulus control.
Keywords: retina • ganglion cells