Noise components in Limulus vision.

Abstract

three), as well as processes in the lamina and medulla (n = 10, Fig. 1 B). Previous anatomical studies witb cobalt chloride showed that a single nerve fiber gives off a puff of processes in the lamina as it continues on into the medulla and other optic nuclei (10). What is the cellular compartment we are recording from? The spike discharge and Neurobiotin staining patterns strongly suggest the axons of optic nerve fibers. However, such large slow potentials would not be expected in this compartment because the soma is located 4-5 cm away in the retina. Moreover, it is unclear why the spike size would change, spike duration would differ, and multiple axons would stain if this were the case. Hence, it appears that we are recording from synaptic compartments, presumably in the branches of optic nerve fibers, that receive action potentials from the main axon and slow potentials from other nerve fibers or cells in the brain. The differences in discharge patterns to single ommatidial and whole eye stimulation result from lateral inhibition in the retina, whereas the differences in slow potentials are a consequence of synaptic interactions in the lamina. Neural processing in the lateral eye of the horseshoe crab is hidden from microelectrodes in the tangled web of the lateral plexus that interconnects neighboring ommatidia to mediate lateral inhibition. Neural processing in the lamina appears to use the same integrative mechanisms as the retina and may be more accessible to electrode studies. If so, we may gain an understanding of the synaptic interactions that occur across a parallel array of optic nerve fibers and their influence on the information sent to other regions of the brain. Supported by NSF grant BNS9309539 and NIH grants MH4974 1 and EY00667.