Evidence for caudate nucleus involvement in an egocentric spatial task: Return from passive transport

Potegal (1972) proposed that the caudate nucleus was involved in processing sensory (especially vestibular) cues for egocentric spatial orientation. The purpose of these experiments was to determine the effect of caudate nucleus lesions on a return from passive transport (RPT) task, which has been shown to depend on vestibular input (Miller, Barnett, & Potegal, Note 1). In the first experiment, 18 male rats were trained on RPT. Six then received bilateral posterior caudate lesions, 6 received bilateral control lesions in the dorsal hippocampus, and 6 served as sham-operated controls. Postsurgical retraining revealed deficits in RPT for the caudate group, relative to hippocampal and sham groups. To test the specificity of the caudate lesion effect, a second experiment examined the effect of caudate and hippocampal lesions on an exteroceptive-cue-based spatial task, olfactory trail finding (OTF). Neither posterior caudate lesions nor dorsal hippocampal lesions produced deficits in OTF. These results suggest that the role of the posterior caudate in spatially oriented behavior is restricted to egocentric orientation based on vestibular cues. Since the caudate lesions had no effect on air-righting behavior, any vestibulostriatal contribution to RPT must be separate from the regulation of righting reflexes. This contribution may be mediated via the posterior portion of the caudate. Failure to find an effect of hippocampal lesions on RPT supports the suggestion that hippocampal involvement in spatial behavior may be restricted to memory and mapping of exteroceptive cues (O'Keefe & Nadel, 1978).