Afferent connections of area 20 in the cat studied by means of the retrograde axonal transport of horseradish peroxidase.

Following injections of horseradish peroxidase in area 20 of the cat neuronal labeling was observed in visual areas 19, 21 and lateral suprasylvian as well as in other sensory, association and limbic related neo- and allocortical regions, both ipsi- and contralaterally. Labeled neurons in the thalamus were identified in the LP-Pu complex, in the LIc, in the midline and intralaminar nuclei, and in the nuclei ventralis anterior, dorsalis medialis, lateralis anterior, lateralis medialis, ventralis posteroinferior, and in the medial subdivision of the posterior group. Projections from other subcortical prosencephalic and brain stem regions are also described.