CORTICOTHALAMIC PROJECTIONS OF THE PRIMARY SOMATOSENSORY BARREL FIELD IN THE WISTAR RAT

The primary somatosensory barrel field (S1Bf) is critically involved in whisker-related sensory processing through its reciprocal interactions with the thalamus. In this study, we examined corticothalamic projections from the S1Bf to thalamic nuclei in adult Wistar rats using the anterograde tracer biotinylated dextran amine (BDA). Seven adult male Wistar rats (approximately 300 g) were used, and stereotaxic BDA injections were targeted to the S1BF based on the Paxinos and Watson rat brain atlas (anteroposterior −2.3 mm, mediolateral +5.0 mm, dorsoventral −3.0 mm relative to bregma). Following tracer injections, labeled axons and terminal fields were visualized histochemically in coronal brain sections. BDA tracer was observed in the ventrobasal, posterior, and lateral geniculate nucleus. The ventrobasal labeling was primarily confined to the ventral posteromedial nucleus. In addition, sparse labeling was observed in the rostral reticular thalamic nucleus. These corticothalamic pathways are known to play a key role in regulating thalamocortical excitability and synchronization, mechanisms that are critically implicated in the generation and propagation of epileptic activity. Therefore, the present anatomical findings provide a structural framework for understanding how alterations in S1Bf-thalamic connectivity may contribute to sensory-triggered seizures and thalamocortical network dysfunction in epilepsy.