A horseradish peroxidase study of afferent projections to nucleus reticularis thalami in the cat

Afferent projections from both the reticular formation and the thalamic relay nuclei to nucleus reticularis thalami (R) were studied using the HRP technique. Injections were performed in different regions of the nucleus. Numerous labelled cells were found ipsilaterally in the lateral geniculate nucleus (GL) following HRP injections in dorsolateral regions of R and in the ventrobasal complex (VB) following HRP injections in the ventral regions. No labelling of brain stem reticular structures was ever found. These results provide evidence for direct projections from the VB and GL nuclei to R. The functional meaning of this data is discussed in relation to previous anatomical and neurophysiological findings. The hypothesis of a significant role of R in feedback circuits modulating sensory information seems to be supported.