The occipito-striate pathway and visual discrimination performance in the white rat

Abstract

Discrete bilateral electrolytic lesions destroying the posterior division of the caudoputamen (disconnecting the occipito-striate projection) produces moderate losses in retention of a horizontal-vertical discrimination habit in the rat. Similarly placed lesions had a significantly smaller effect on an equally difficult nonvisual discrimination habit. These results, in conjunction with others, suggest that multiple occipitofugal systems are involved in visually guided behavior. Webster (1961) has demonstrated that the projection of virtually all cortical areas upon the caudoputamen (CP) is organized on a topographical basis in the rat. With respect to the rostral-caudal dimension, for example, the anterior cortical regions project to the anterior portions of the CP, while the posterior cortical regions give rise to projections to the posterior portions of the CPo That a cortico-striate pathway may playa significant role in visually guided behavior was first suggested by the finding that lesions to the tail of the caudate nucleus impair visual discrimination learning in monkeys (Divac, Rosvold, & Szwarcbart, 1967). More recently , Livesey and Muter (1976) , using the method of electrical (blocking) stimulation, have reported retardation in visual discrimination reversal in rats stimulated within the posteroventral CP.The purpose of the present study was to determine if lesions to the posterior aspect of the CP in rats would produce a selective deleterious effect on a visual discrimination habit. MEmODAdult male albino rats of the Wistar strain were trained to approach a horizontal black-and-white striped card (positive) and to avoid an adjacent vertical black-and-white striped card (negative) in a Thompson-Bryant (1955) discrimination apparatus . Under the motive of escape-avoidance of footshock , a response to the unlocked positive card admitted the animal to the goalbox, whereas a response to the locked negative card was automatically punished by mild footshock . The positive card was switched from the left to the right window in a strict double-alternation sequence. Eight trials were given daily with an intertrial interval of 60 sec. The criterion of learning consisted of no more than one error in 2 consecutive days . Following learning, the majority of rats sustained one-stage bilateral electrolytic lesions to the posterior aspect of the CP; the remaining rats served as the normal control group . After a recovery (or rest) period of 10 days, the animals were given a Reprint requests should be sent to Robert Thompson ,

Characteristics of perceptual grouping in rats.

“…Rats are nevertheless capable of discriminating complex visual patterns (e.g., Lashley, 1930Lashley, , 1938. Investigations of the effects of cortical lesions on visual pattern discrimination have indicated that multiple cortical systems within occipto-temporal areas mediate form perception in rats (Lashley, 1931;Lavond et al, 1978;McDaniel, Wildman, & Spears, 1979;Tompson & Bachman, 1979;Wuensch, Broome, Means, & Harris, 1978).…”