Abstract
Purpose: :
Characterize the statistical properties of rat retinal ganglion cell spike trains under steady illumination
Methods: :
The maintained discharge of ganglion cells was recorded at various light levels from the optic tract of paralyzed rats anesthetized with urethane, urethane-chloralose, and ketamine.
Results: :
Urethane and urethane-chloralose anesthesia produced unstable spiking behavior in most rat ganglion cells. The firing rate jumped up and down in epochs of seconds to minutes. The waxing and waning persisted both in the dark and under constant uniform illumination. Ketamine anesthesia, on the other hand, produced stable activity patterns in every cell. Interspike interval distributions in most cases showed signs of oscillatory behavior, with increased firing probability at an interval of 25-40ms and multiples of this interval. The oscillations gave rise to sharp peak between 25-40Hz in maintained discharge power spectra. The oscillation frequency is much higher than the signaling range of the cell, which cuts off around 10Hz. Oscillations were present in all types of recorded cells (ON and OFF, X and Y) and the oscillation frequency varied both within and across animals. The maintained discharge spectra could be accurately reproduced with an integrate and fire model of spike discharge and a noisy sinusoidal input.
Conclusions: :
The maintained discharge of rat retinal ganglion cells is oscillatory. The prominence and prevalence of the oscillation suggests that it serves a functional role in rat vision.
Keywords: ganglion cells • image processing • receptive fields