THE EFFECTS OF TELENCEPHALIC LESIONS ON VISUALLY MEDIATED PREY ORIENTING BEHAVIOR IN THE LEOPARD FROG (RANA-PIPIENS) - II - THE EFFECTS OF LIMITED LESIONS TO THE TELENCEPHALON

Unilateral removal of the telencephalon in the leopard frog, Rana pipi ens, produces a contralateral deficit in visual prey orienting behavio r [Patton and Grobstein, 1997]. In mammals, such deficits are most com monly associated with damage to the isocortex, a pallial derived struc ture. In contrast, we here report that in leopard frogs, lesions that remove substantial areas of one telencephalic lobe, including virtuall y the entire pallium, have no discernible effect on visual orienting b ehavior. Restricted lesions to the ventrocaudal telencephalon, however , produce an effect that closely resembles that produced by the comple te removal of one telencephalic lobe. The 'critical area' that is both included in all lesions that are effective in producing a severe defi cit and excluded from all ineffective lesions includes a portion of th e caudal striatum, The striatum is known to play a significant role in anuran vision. It thus seems likely that the deficit produced by unil ateral removal of the telencephalon in the leopard frog is due specifi cally to the removal of the caudal striatum. Unilateral lesions to the striatum have previously been shown to produce a contralateral defici t in visual orienting behavior in cats, and a role for the striatonigr al pathway in the production of the visual orienting deficit that foll ows visual cortex lesions has been proposed. The current findings call attention to the possible general importance of the striatum in the c ontrol of vertebrate visual orienting behaviors.