Cytoarchitecture and chemoarchitecture of the striate cortex and a putative area prostriata in the domestic cat.

OBJECTIVE: The striate cortex (V1) and the adjacent area prostriata (Pro) are key components of visual cortical organization. In the domestic cat, however, the cytoarchitectural and chemoarchitectural features of the medial V1-presubiculum (Prs) transition remain incompletely defined, and the anatomical relationship between the feline splenial visual area/splenial visual cortex (SVA/SV) and Pro remains unresolved. This study aimed to characterize the laminar organization and molecular marker distribution of V1 and a candidate region provisionally designated as putative Pro in the domestic cat. METHODS: Two adult female domestic cats were examined. Coronal sections of the right hemisphere were processed for Nissl staining and immunohistochemistry for Calbindin-D28k (CB), Purkinje cell protein 4 (PCP4), and non-phosphorylated neurofilament H (SMI-32). Low-magnification serial sections were used to assess regional topography, and high-magnification micrographs were used to examine laminar and cellular labeling patterns across the V1-putative Pro-Prs transition. RESULTS: V1 showed a typical six-layered neocortical architecture with a prominent layer 4 and abundant SMI-32-immunoreactive pyramidal neurons in layers 3 and 5. PCP4 labeling was evident in pyramidal layers of V1. By contrast, putative Pro showed a dysgranular profile with an indistinct layer 4, PCP4-positive neurons mainly in deeper layers, and weak or sparse SMI-32 immunoreactivity. No convincing CB-immunoreactive neuronal profiles were identified in the sampled V1 field, whereas weak superficial CB labeling and occasional dark profiles were observed in putative Pro. Because cellular contrast was limited, CB staining was treated as a descriptive observation rather than a decisive criterion for regional parcellation. The transition between putative Pro and Prs was further supported by differences in PCP4 and SMI-32 labeling patterns. CONCLUSION: The present findings characterize a restricted dysgranular transition zone between medial V1 and Prs that is provisionally designated as putative area prostriata. The results provide anatomical and immunohistochemical information relevant to the identification of feline Pro, but do not establish whether the region described here is identical to, overlaps with, or is distinct from the physiologically defined SVA/SV. Larger studies combining histology, connectivity analysis, and electrophysiological mapping will be required to resolve this relationship.