In the article “The Structure of Multi-Neuron Firing Patterns in Primate Retina,” by Jonathon Shlens, Greg D. Field, Jeffrey L. Gauthier, Matthew I. Grivich, Dumitru Petrusca, Alexander Sher, Alan M. Litke, and E. J. Chichilnisky, which appeared on pages 8254–8266 of the August 9, 2006 issue, there were two errors. On page 8255 (in Materials and Methods, Spike sorting, third sentence), “spikes were identified using a threshold of three times the voltage SD” should read “spikes were identified using a threshold of four times the voltage SD.” On page 8256 (in Materials and Methods, Stimulation and receptive field analysis, first paragraph), “intensity 9200 (8700, 7100)” should read “intensity 4300 (4200, 2400).”