Paw preference in mice with callosal defects induced by prenatal gamma irradiation

The development of the corpus callosum of male Swiss mice was perturbed by exposure to gamma radiation at embryonic day 16 with total doses of 2 Gy (N = 48) or 3 Gy (N = 26). At adulthood paw preference was studied in these callosal defective animals and in 93 control nonirradiated male Swiss mice. The analysis of directional laterality indicated a populational tendency for right paw use in the 2 Gy group (60 per cent ) that was markedly increased in the 3 Gy group (95 per cent ). In the 3 Gy group, directional laterality was significantly different from chance in contrast to that observed in normal controls (49 per cent ). In the three groups most mice presented a significant individual paw preference. These data are consistent with our hypothesis that the early absence of the corpus callosum disrupts the normal pattern of directional asymmetries

The effects of total and partial callosal agenesis on the rotatory behavior of Balb/cCF mice

We report a study on rotational behavior (free swin test) of 30 adult male mice of an inbred strain in which about 20% of the animals are born with callosal defects (the BALB/cCF strain). The experiment was designied to study the relationship between the development of the corpus callosum and the degree of lateralization in rotatory behavior. Most of the BALB/cCF mice (77%) were lateralized rotators. Although most animals with a normal callosal area presented individual asymetry, there was no signficant tendency for a populational asymetry toward one side in this group. In contrast, 75% of the animals with abnormally callosal areas were left rotators. These animals, therefore, presented not only individual asymetry, but also a tendency for a populational asymetry. It was concluded that disturbances in the development of the corpus callosum are related to the appearence of directional populational asymetry in rotatory behavior

Absence of populational cerebral asymmetries in mice with callosal defects induced by prenatal gamma irradiation

The development of the corpus callosum of 19 male Swiss mice was disturved by exposure to a 60Co gamma source on embryonic day 16 with a total dose of 2 Gy (dose rate of 56 to 59 rads/min). At adulthood the animals were perfused with saline followed by formaldehyde and the cerebral hemispheres were weighed and phtographed in dorsal, lateral and medial views. Brain asymmetries were evaluated by measurements of hemisphere weight, as well as dorsal and lateral areas. From the measurements of the midsagittal callosal areas, performed on the medial views, 2 subgroups could be identified: one with a small callosal remnant (N=9) and another with a non-measurable callosal area (N=10). In spite of a pronounced individual asymmetry, the irradiated mice (N=19) did not show a populational asymmetry toward any side. A slight tendency favoring the left hemisphere was found in the small remmant subgroup. These results are consistent with our previous data for a strain of mice in which some animals present callosal defects. We conclude that the present data support the hypothesis that the corpus callosum may play a role in directing morphological hemispheric asymmetries