The ipsilateral cortico-cortical connections of area 7b, PF, in the parietal and temporal lobes of the monkey.

The cortico-cortical connections of area 7b (or PF) in the parietal and temporal lobes of the monkey have been studied with the method of axoplasmic transport of horseradish peroxidase (HRP). Area 7b is reciprocally and precisely connected with area 5, the second somatic sensory area (SII), the retroinsular area, the granular insular area (Ig), area 23 of the cingulate cortex and with the cortex in the walls of the superior temporal sulcus. Area 7b is not interconnected with area 7a (PG) nor with any of the prestriate visual areas. After injections of HRP into area PF the labelled cells in all these areas, except the granular insular area, are mainly in layer III and these cells are considered to be the origin of 'feed-forward' type connections; in the granular insular area most of the cell labelling is in layer V, interpreted to be the origin of 'feed-back' connections. Between SI and area PF there are two sequences of connections in parallel with each other, one through area 5 and the other through SII. In all areas the labelled cells are in clusters of 500-2000 microns width on individual sections and in bands of these widths on planar reconstructions.