Active avoidance behavior following archistriatal lesions in pigeons.

Experiment 1 examined the performance of 10 pigeons, 5 with bilateral medial archistriatal lesions and 5 sham-operated controls, in the acquisition and maintnenance of a discrete-press avoidance response. The archistriatal subjects had longer response latencies and never attained the level of performance achieved by the controls. In Experiment 2 eight pigeons learned a treadle-press response to avoid or escape shock on a signaled free-operant schedule. After 17 daily sessions four subjects received bilateral lesions in the medial archistriatum, and four received control lesions in the neostriatum. After recovery from surgery, all subjects were returned to the experimental procedure. Avoidance of those subjects with archistriatal lesions was impaired relative to the postoperative level while that of the control group was unchanged. These results are interpreted in the light of earlier experiments showing reduced escape and avoidance behavior both in order avian species and in mammals with lesions in the amygdala, to which the archistriatum is considered homologous.