Callosal agenesis affects consistency of laterality in a paw preference task in BALB/cCF mice.

We tested the hypothesis that the ontogenetic development of the corpus callosum (CC) affects the consistency of laterality in a paw preference task. Adult male mice (55 normal and 29 acallosal) of the BALB/cCF strain were initially tested (twice; inter-test interval: 72 h) in an unbiased setup in which both forepaws could easily perform a reaching movement. In a subsequent test, animals were placed in a biased setup that favored the use of the non-preferred paw. Acallosal and normal mice were strongly lateralized in the unbiased setup. Additionally, while normal mice did not present a populational bias favoring one of the paws, acallosal mice presented a significant bias favoring the left paw. In the biased setup, left- and right-pawed normal mice were equally consistent (approximately 65% of the animals, in both groups, used the preferred paw of the initial two tests, in spite of the bias). Conversely, while left-pawed acallosal mice were as consistent (65%) as normal mice, only 20% of right-pawed mice were consistent. These results suggest that the development of the CC affects consistency of laterality in a side-dependent manner. These results are discussed considering the role of the CC in the establishment of behavioral lateralization.