The retina encodes environmental light intensity to drive innate physiological responses. The synaptic basis of such coding remains obscure. Intrinsically photosensitive retinal ganglion cells (ipRGCs) are the only retinal output neurons stably encoding intensity. They do so even without their melanopsin photopigment, so specializations in their synaptic drive from bipolar cells (BCs) must also contribute. Here, we shed new light on mechanisms responsible for this unique intensity-coding drive. By ultrastructural reconstruction, we show that specific BC types and unusual ribbon synapses carry photoreceptor signals to ipRGCs. By glutamate imaging and electrophysiology, we show that their light responses are unusually persistent. Still, we find that virtually all BCs encode intensity. Intensity coding becomes restricted to ipRGCs primarily because other RGCs filter out steady-state intensity signals postsynaptically. Thus, neural 'pinholes' in global, persistent neural 'masking' allow intensity signals to be encoded by ipRGCs and sent to specific centers of the visual brain.

We present a 10-patient case series supporting the use of the erector spinae plane block (ESPB) as a novel approach for the treatment of acute pain from renal colic. An in-plane needle approach was used with either transverse or longitudinal orientation of the ultrasound probe on the affected side, in either seated or prone patient position. These cases showed significant improvement in patient reported pain; suggesting that the ESPB can be used safely and effectively for either primary or adjunctive treatment of acute pain due to renal colic in the emergency department.

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