Wheel running behavior is impaired by both surgical section and genetic absence of the mouse corpus callosum.

Mice lacking a corpus callosum (CC) often show little or no deficit on tests of behavior. This paper reports that on highly complex bimanual motor tasks, deficits can be found. The speed of running on a wheel with irregularly spaced rungs is reduced by both hereditary absence of the CC in 129 x BALB/c recombinant mice and surgical section of the CC in genetically normal B6D2F(2) mice. The effect of CC absence appears on measures most closely related to speed, no influence exists on the amount of running over a period of 5 days. Motor behavior on a notched balance beam, on the other hand, shows clear superiority of the hybrid mice but no relation with reduced size of the CC, whether it was produced by genotype or surgery. The effect of absent CC is task dependent, but it is not obscured by developmental compensation in the recombinant mice.