A. Plot of the distribution of Fos-labeled cells in a section from squirrel monkey SM5, at about P3.5. Conventions as in Fig. 1A. Scale bar 2 mm. B. Photomicrograph of Fos-immunoreactivity in the nucleus of the mesencephalic tract of the trigeminal (Me5) on a section at about P0.5. Scale bar 500 μm. Abbreviations DCN, dorsal cochlear nucleus, me5, mesencephalic tract of the trigeminal, scp, superior cerebellar peduncle.