Tracing Neural Connections of Human Brain with Selective Silver Impregnation: Observations on Geniculocalcarine, Spinothalamic, and Entorhinal Pathways

In selected human brains, it is possible to study the efferent connections of a damaged site with the suppressive silver impregnation techniques described by Nauta and Gygax.¹ Autopsy specimens with circumscribed lesions of recent origin (one to five weeks before death) are suitable. However, the large size of the human brain and the lack of perfusion with fixative necessitates modifications in the methodology used on experimental animals. With these modifications, it has been possible to trace details of the spinothalamic tract, the geniculocalcarine pathway, and a projection into the entorhinal area in autopsied human brains. More frequent use of this methodology may substantially increase the information that is currently available on the neuronal connections of the human brain.