Plasticity of cortico-thalamic projections and functional recovery in the unilateral detelencephalized infant rat

Previous results have shown that the unilateral removal of the telencephalon in adult rats leads to the appearance of crossed connections from the remaining telencephalon to the thalamus one week after the ablation. This study extends this finding to infant rats. The telencephalon structures were unilaterally removed in 7-day-old animals. As in adult rats the ablation induced behavioral asymmetries, including active turning behavior which ceased within the first days after the lesion. Either immediately after the ablation or one week thereafter the animals were injected with horseradish peroxidase (HRP) into the posterior part of the thalamus ipsilateral to the lesion. HRP-labeled cells appeared in the remaining contralateral cortex in animals that were injected one week after the lesion. Rapid functional recovery from the lesion-induced behavioral asymmetries, as indicated, for example, by the cessation of spontaneous turning behavior, may be related to the observed appearance of crossed projections between structures that are normally connected only ipsilaterally.