Operant Discriminative Learning and Evidence of SubtelencephalicPlastic Changes After Long-Term Detelencephalation in Pigeons

摘要

We analyzed operant discrimination in detelencephalated pigeons and neuroanatomical substrates after long-term detelencephalation. In Experiment I, experimental pigeons with massive telencephalic ablation and control pigeons were conditioned to key peck for food. Successive discrimination was made under alternating red (variable-ratio reinforcement) and yellow (extinction) lights in one key of the chamber. These relations were interchanged during reversal discrimination. The sessions were run until steady-state rates were achieved. Experiment II analyzed the morphology of the nucleus rotundus and optic tectum in long-term detelencephalated and control birds, using a Klüver-Barrera staining and image analyzer system. Detelencephalated birds had moretraining sessions for response shaping andsteady-state behavior (p<0.001), higher red keypeck rates during discrimination (p<0.01), and reversal discrimination indexes around 0.50.Morphometric analysis revealed a decreasednumber of neurons and increased vascularity,associated with increases in the perimeter(p<0.001) in the nucleus rotundus. In the optictectum, increases in the perimeter (p<0.05)associated with disorganization in the layersarrangement were seen. The data indicate thattelencephalic systems might have an essentialfunction in reversal operant discriminationlearning. The structural characteristics of subtelencephalicsystems after long-term detelencephalationevidence plastic changes thatmight be related to functional mechanisms oflearning and neural plasticity in pigeons.