Abstract
Purpose :
Zebrafish (Danio rerio) are a widely used to study vertebrate development, diseases, genetics and increasingly visual function. Zebrafish retina develops quickly with adult-like function occurring 20 day postfertilization. While adult zebrafish outer retinal and amacrine cell function has received some attention virtually nothing known about their ganglion cell (GC) function. In adult fish, 11 different types of GCs have been identified morphologically (Mangrum, 2002) and an ON-OFF response to a light flash has been shown once (Huand, 2005). Here we address this deficit by clustering adult zebrafish GCs into functional classes and determine their temporal and spatial properties.
Methods :
Multiunit GC activity was recorded from freshly isolated retina of adult zebrafish (0.5-2yrs), continuously superfused with room temperature Ames’, using an 8*8 perforated multielectrode array. Light stimuli consisted of full field light intensity steps, full field temporally modulated binary M-sequences (FF-Mseq) and spatial/temporal modulated binary checkerboard M-sequences (ST-Mseq). Stimuli were projected by a Lightcrafter and focused on to the photoreceptors via a x2 immersion objective.
Results :
Hierarchical clustering of GC time-series responses to light stimuli suggest about 10 functional GC classes in adult zebrafish. For the FF-Mseq stimulus, the reverse spike triggered average (rSTA) and the time-series power spectra show most GCs responses had band pass characteristic with peak frequencies commonly occurring between approx. 5 to 15Hz. For the ST-Mseq stimuli, rSTA analysis revealed typical centre-surround receptive field structures as well as serval surprisingly complex centre-surround organisations. Here surrounds would not encompasses the centre, but rather appear in one part of the surround often changing location over the rSTA period. In some instances both the location and number of these surround components would change in time.
Conclusions :
We found evidence of about 10 function types of zebrafish GCs based on their response profiles to binary modulated white light stimuli. The addition of chromatic information as well as more complex stimuli features, like orientation or movement, may increase this number further. The response profiles of many of the GCs suggests the zebrafish retina is tuned to process higher temporal frequencies relative to mice or salamander.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.