From axon to mind: Letters of a comparative neuroanatomist and a neurophysiologist

Systematic efforts to localize brain functions began in the nineteenth century through comparative neurological studies and clinicopathological correlations. By the early-twentieth century, investigations into the microstructure of cortical tissue enabled further subdivision of the cortex into distinct regions, laying the foundation for correlating anatomical structure with function. Advances in neurophysiology-such as the discovery of reflexes, synaptic transmission, and the development of electroencephalography-revealed that neurons operate in organized circuits rather than independently. However, the link between brain structure and consciousness remained elusive. Between 1950 and 1956, C. Judson Herrick, a comparative neuroanatomist, and George Bishop, a neurophysiologist, explored this question through correspondence. Herrick analyzed how increasing structural complexity between species corresponded with more complex behavior. Bishop, known for his work with Joseph Erlanger and Herbert Gasser on nerve action potentials, advanced the understanding of nerve fiber function. Together, Herrick and Bishop explored the role of older, more primitive brain structures in facilitating higher functions and emphasized the interconnectedness and integration of brain regions. Although their exchange did not resolve how brain structure results in complex behaviors, their dialogue highlighted the importance of evolutionary and comparative perspectives in understanding brain function.