Corticostriatal projections from rat barrel cortex have an anisotropic organization that correlates with vibrissal whisking behavior

To elucidate the detailed organization of corticostriatal projections from rodent somatosensory cortex, the anterograde tracers biotinylated dextran a mine (BDA) and fluoro-ruby (FR) were injected into separate parts of the wh isker "barrel" representation. In one group of rats, the two tracers were i njected into different barrel columns residing in the same row; in the othe r group of rats, the tracers were deposited into barrel columns residing in different rows. Reconstructions of labeled axonal varicosities in the neos triatum and ventrobasal thalamus were analyzed quantitatively to compare th e extent of overlapping projections to these subcortical structures. For bo th groups of animals, corticostriatal projections terminated in densely pac ked clusters that occupied curved lamellar-shaped regions along the dorsola teral edge of the neostriatum. When the tracers were injected into differen t whisker barrel rows, the distribution of BDA- and FR-labeled terminals in the neostriatum followed a crude somatotopic organization in which the amo unt of overlap was approximately the same as in the ventrobasal thalamus. W hen both tracers were injected into the same whisker barrel row, however, t he amount of corticostriatal overlap was significantly higher than the amou nt of overlap observed in the ventrobasal thalamus. These results indicate that corticostriatal projections from whisker barrel cortex have an anisotr opic organization that correlates with the pattern of vibrissal movements d uring whisking behavior.