Callosal mediation of cortical inhibition in the lateralized rat brain.

This paper tested a brain model for muricide. The model states that, in animals given handling stimulation in infancy, the right hemisphere is dominant for the occurrence of mouse killing and the left hemisphere acts to inhibit this behavior. On the assumption that the inhibition is mediated transcortically, it follows that severing the corpus callosum should result in an increase in muricide. This prediction was confirmed. In addition, prior research has found that animals not given extra stimulation in infancy show no evidence of lateralization for muricide. Therefore, splitting the brains of this group should not have any effect. This prediction was also confirmed. Latency analyses of muricidal rats found that those with only an intact right hemisphere killed much more quickly than those with only an intact left hemisphere. Sham controls had killing latencies similar to animals with only a right hemisphere. This pattern represents a brain model in which the right hemisphere is dominant for latency to kill. Rats exposed to mice in early life killed much more quickly than those without this early social experience, thus indicating that familiarity can reduce killing latency.