Necturus

 

 

Temporal summation properties of Necturus retinal ganglion cells

John R. Tuttle and Brian C. Madden

 

The temporal summation properties of Necturus retinal ganglion cells were studied by extracellular recording of their impulse discharge. For each cell the dependence of its response (total number of impulses) upon stimulus intensity was determined for as many stimulus durations as time permitted. Using smooth curves fitted to the data, the intensities which elicited several criterion responses were determined for each duration. The criterion response ranged from just suprathreshold to the maximum response common to all durations.

 

Sustained-responding ganglion cells behaved the same at all response levels, exhibiting temporal summation up to some critical duration which varied from cell to cell. This critical duration was never less than the 500 milliseconds previously reported for Necturus horizontal cells and the PNR; it was usually longer and sometimes exceeded one second.

 

All-transiently-responding ganglion cells behaved similarly at low response levels and a few behaved similarly at all response levels. Many of these cells, however, exhibited a preferential tuning for intermediate durations at moderate response criteria which became more pronounced as the response criterion increased.