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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.

Two major classes of neurons were observed in Golgi impregnated material of two regions of the hyperstriatum ventrale (HV) (medial and rostral HV) of the chick telencephalon: a Golgi I type neuron with long axon (putative projection neuron) and a Golgi II type neuron with short axon (putative local circuit neuron). On the basis of the nature of the axon (bifurcating or non-bifurcating, ascending or descending) and of the dendrites (spiny or aspinous, and thickness), the following subclasses (types) were identified: two long axon (projection) and three short axon (local circuit) neurons in the medial (mid-telencephalic) hyperstriatum ventrale, and one major long axon (projection) and two short axon (local circuit) neurons in the rostral hyperstriatum ventrale. Possible patterns of intraregional connections between these neurons are suggested on the basis of cytoarchitectonics. The differences in cellular types and in internal connectivity patterns strongly suggest, in agreement with physiological and behavioural observations, that the medial (mid-telencephalic) hyperstriatum ventrale distinctly differs in cellular morphology from other parts of hyperstriatum ventrale in so far as it displays a greater diversity of neuronal types with an apparent higher degree of complexity.