Columnar distribution of U-fibres from the postcruciate cerebral projection area of the cat's group I muscle afferents.

Needle stitch lesions were made in the maximal point of the cerebral projection area of the low threshold muscle afferents near the postcruciate dimple of the cat's posterior sigmoid gyrus. The lesions did not exceed 500 mum in diameter and were restricted to the cortical grey matter. Degenerating nerve fibres and terminals were investigated with Fink-Heimer technique in four cats (survival times: 26, 48 and 96 hours). The cytoarchitectonic areas of the sensori-motor cortex were determined in cresyl violet and van Gieson sections. All lesions were made in area 3a. Degenerating U-fibres originating from the lesion travelled in the white matter to the cortex of area 4 gamma, 3b and 2. They reentered the cortex and branched in layer III. Terminal degeneration was found in layer I. The degeneration was distributed to distinct columns with a diameter of about 1mm. Such columns were observed laterally and medially in area 4 gamma, in area 3b near the caudal end of the coronal sulcus, in area 2 near the lateral ansate sulcus and in the forelimb region of SII. The distribution of the cortico-cortical connections from the cerebral projection area of the forelimb group I muscle afferents was discussed in relation to the known cerebral projections of group I muscle afferents, low threshold joint afferents, pacinian afferents and low threshold skin afferents.