Magnocellular and parvocellular divisions of pigeon nucleus isthmi differentially modulate visual responses in the tectum.

摘要: The electrophysiological responses of 162 tectal cells to computer-generated visual stimuli were extracellularly recorded from 24 homing pigeons before and after injecting either lidocaine or N-methyl-d-aspartate (NMDA) into the nucleus isthmi pars magnocellularis (Imc) parvocellularis (Ipc). Micro-injections Imc resulted in a significant reduction firing rate 80% cells, whose excitatory receptive fields (ERFs) localized within ERF cell where was injected. In contrast, when injected Ipc under identical circumstances it had no effect on visually driven activity 68% cells. However, amino acid NMDA produced 75% neurons their ERFs isthmic ERF, while similar application response 94% neurons. When outside chemical injected, Imc-injected 9 out 10 whereas Ipc-injected increased 7 17 Therefore, is suggested that Imc-tectal fibers participate positive feedback pathway Ipc-tectal are involved negative pathway.