ORIENTATION DISCRIMINATION IN THE CAT AND ITS CORTICAL LOCI

This chapter discusses whether a processing hierarchy exists in the cat, similar to the one described in monkeys. Since the use of anatomical criteria that has proved insufficient to distinguish a detailed hierarchy between areas in the cat, a rather coarse division between lower order areas (Tier I areas) and higher order areas (Tier I1 areas) is made. As Tier I areas, two areas which receive the strongest input from the LGNd— that is, areas 17 and 18. Tier II areas included all those areas which receive direct input from areas 17 and 18 that is, areas 19, 20a, 21a and 21b, AMLS and PMLS. This study utilizes an experimental plan in which cats were trained to discriminate between differently oriented contours. The behavioral effects of bilateral anatomical lesions of Tier I and Tier II areas were assessed. The effects of cortical lesions on the discrimination of bar stimuli, followed by an account of lesion effects on illusory contour discrimination are discussed. The result description divides the postoperative observation period into two parts. Short-term post-operative measurements correspond to measurements obtained in the first four months after the surgery (—that is, a maximum of 80 testing sessions). Measurements obtained in a later stage are referred to as long-term measurements. © 1993, Academic Press Inc.