Visual Receptive-field Properties of Single Cells in the Rat Superior Colliculus

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Abstract
Receptive-field properties were studied in single cells in the visual layer of the albino rat''s superior colliculus. All the samples (N = 195) were identified as 1 of the 4 classes (I, II, III and IV cells) which were established previously on the bases of the response properties to single shocks to the optic pathway and of the recording sites. The 4 classes were located more deeply in the superior colliculus roughly in the order of from I to IV. Response latencies to single shocks to the optic chiasm were shortest in the III cells, intermediate in the II cells and longest in the I and IV cells. These cell classes were different from each other in a number of visual properties. Receptive-field centers in the I and II cells (N = 26 and 27, respectively) were of either the ON-OFF or the ON type. Of class III (N = 47), 1 subgroup (IIIa) consisted mostly of the ON-OFF type. About 2/3 of the IV cells (71/95) were of either the ON, the OFF or the ON-OFF type; except for 2 cells, therest were all of the motion-sensitive type. The average size of the receptive-field center was small (5.4.degree. .+-. 2.3.degree.) in the class I, intermediate in the classes II and III (8.1.degree. .+-. 2.1.degree.) and 7.1.degree. .+-. 2.7.degree., respectively) and large in the class IV (18.1.degree. .+-. 15.9.degree.). Responsiveness to moving light stimuli (speeds, 40.degree.-90.degree./s) decreased in the order of IIIa, II and IIIb, and I and IV. Maintained activity was lower in the superficially located cells (I, II and IIIa) than in the deeply located ones (IIIb and IV).