Fixed interval responding by pigeons following damage to corpus striatal and limbic brain structures (paleostriatal complex and parolfactory lobe)

Abstract

Twenty-three adult pigeons were trained on a fixed-interval 2 min schedule for grain reinforcement. After responding stabilized on the fixed-interval schedule, groups of animals were either lesioned bilaterally in paleostriatal complex (PC), parolfactory lobe (LPO), neostriatum and/or ectostriatum (N/E controls) or received no lesioning current at all (sham controls). Analysis of reponse timing patterns and response rates indicated significant declines only in experimental animals; PC group quarter life scores and rates returned to normal after 6 days, LPO group quarter life scores returned to preoperative levels after 16 days and response rates remained significantly depressed through 21 test days. PC pigeons exhibited short-lived postsurgical signs of somnolence with sustained docility. LPO pigeons, in contrast, exhibited early and sustained defensive behavior. It is hypothesized that subtelencephalic PC inputs and/or outputs may be more critical than neostriatal inputs in paleostriatal control of operant responding and/or arousability. The results suggest that the PC and LPO, two basal forebrain structures, are separable both anatomically and functionally.