Lobus

Abstract: The olfactory system of the pigeon (Columba livia) was examined. Our electrophysiological and experimental neuroanatomical (Fink-Heimer technique) data showed that axons from the olfactory bulb terminated in both sides of the forebrain. The cortex prepiriformis (olfactory cortex), the hyperstriatum ventrale and the lobus parolfactorius comprised the uncrossed terminal field. The crossed field included the paleostriatum primitivum and the caudal portion of the lobus parolfactorius, areas which were reached through the anterior commissure. In this report the relationships between areas that receive olfactory information and the possible roles that olfaction plays in the birds' behavior are discussed.

Abstract: Day-old-chicks can be trained in one trial to avoid a methylanthranilate-coated bead (methyl-chicks). The lobus parolfactorius of the chick forebrain is an important structure for memory of this avoidance response. To examine training-induced electrophysiological changes in this structure, spontaneous neuronal bursting activity was measured from the lobus parolfactorius of anaesthetized, day-old methyl- and water-chicks (the latter chicks trained to peck at a water-coated bead) over the period 1-10 h post-test. Bursting was significantly higher in methyl-chicks over this period. This post-test increase was time-dependent: bursting in methyl-chicks was significantly higher only during the period 4-7 h post-test. In a second experiment, methyl-chicks were subjected to brief, subconvulsive electroshock 5 min post-training. When tested 1 h later about half of these chicks showed recall (avoided the bead) and half were amnesic (pecked the bead). These chicks were anaesthetized and bursting was recorded from the lobus parolfactorius. Chicks that showed recall exhibited a significantly higher level of bursting over the period 1-10 h post-test when compared to chicks that were amnesic. The time course of bursting was similar to that seen in non-electroshocked methyl-chicks. These results suggest that passive avoidance training induces a memory-specific, time-dependent increase in neuronal activity within the lobus parolfactorius of day-old chicks. This increase may be directly associated with long-term consolidation of memory for the task.

Abstract: A study of was carried out of Golgi impregnated material in two regions of the paleostriatal complex of the chick telencephalon, the lobus parolfactorius and paleostriatum augmentatum. As in our previous investigation of the chick medial hyperstriatum ventrale, two major classes of neurons were observed in the paleostriatum: a Golgi I type neuron (type 1) with long axon (putative projection neuron) and a Golgi II type neuron (type 2) with short axon (putative local circuit neuron). Based upon the nature of the axon (bifurcating or nonbifurcating, ascending or descending) and of the dendrites (spiny or aspinous, and thickness), the following subclasses (types) were identified: two projection and three local circuit neurons in the lobus parolfactorius and two projection and two local circuit neurons in the paleostriatum augmentatum. In addition to known differences in developmental chronology and extrinsic connectivity, the lobus parolfactorius clearly differs from palaeostriatum augmentatum in cellular composition and organization. From its cytoarchitectonic appearance we would suggest that the lobus parolfactorius is the paleostriatal region of greater complexity.