Cerebrocortical plasticity after acute and chronic unilateral lesion of the central vestibular system in rats: A Micro-PET study

Objectives Animal studies revealed a significant predominance of the left parieto-insular cortex for processing vestibular information. The aim of the present study was to investigate brain glucose metabolism of vestibular processing and plasticity of the vestibular network after acute and chronic, unilateral lesion in the central pathway.

Methods Brain glucose metabolism in 12 rats was measured (FDG, Micro-PET Focus) under different conditions: during left galvanic vestibular stimulation (t=50, 0.2 mA, 1 Hz) and during control stimulation. In 8 rats a stereotactic electrolytic lesion was set into a vestibular processing thalamic nucleus, and 4 rats underwent a shame-operation. The time course of compensatory brain activity after intervention was investigated by longitudinal PET imaging after one day, three days, seven days and twenty days. PET images were realigned to an MRI image of the rat brain and spatially normalized using an FDG rat brain template. Statistical analyses were performed on a voxelwise basis by means of SPM5.

Results In comparison to the shame-lesioned animals the SPM-analyses showed a significantly increased glucose metabolism ipsilateral to stimulation in the postsubiculum and the colliculus superior one day post lesion and contralateral in the corpus geniculatum medialis three days post lesion (p<0.001). After seven days, the entorhinal cortex region ipsilateral and after twenty days, the zona inserta showed a high metabolism rate.

Conclusions Our results exhibit brain regions which are highly associated with the vestibular network. The data indicate that a time-dependent compensatory cerebral plasticity exists within the network that controls vestibular function. Different functional regions seem to be involved in the time course of vestibular compensation after a central vestibular lesion