THE EFFECTS OF TELENCEPHALIC LESIONS ON VISUALLY MEDIATED PREY ORIENTING BEHAVIOR IN THE LEOPARD FROG (RANA-PIPIENS) - I - THE EFFECTS OF COMPLETE REMOVAL OF ONE TELENCEPHALIC LOBE, WITH A COMPARISON TO THE EFFECTS OF UNILATERAL TECTAL LOBE LESIONS

In this paper, we report studies aimed at characterizing the relations hip between forebrain and midbrain systems involved in the control of prey orienting behavior in the leopard frog. In frogs, unilateral fore brain lesions, like unilateral rectal lobe lesions, have their most pr ominent effects in the contralateral monocular visual field. Such lesi ons produce partial reductions in response frequency in the binocular visual field as well. Similar sequelae follow unilateral tectal lobe r emoval. These findings suggest that the effects of unilateral forebrai n removal can be largely attributed to removal of a facilitating influ ence on the tectal lobe on the same side of the brain. In the case of both forebrain and midbrain lesions, behavior was assayed not only in terms of the frequency with which animals responded to stimuli at vari ous locations in the visual field (as is usually done) but also in ter ms of the latency of whatever responses were observed. A striking inve rse relationship between response frequency and response latency was f ound, both in lesioned and in normal frogs. This relationship has not previously been noticed, doesn't appear to be an obvious consequence o f any existing models of the neuronal circuitry underlying anuran orie nting behavior, and is difficult to account for in terms of the time s cales associated with axonal conduction times and synaptic delays. It may be easier to account for in terms of the responses to perturbation of large interacting systems of neurons, and this possibility seems w orthy of further exploration.