Cartography, like medicine, has transformed over the centuries from art into science. Due to the challenges of long-distance travel, medieval European map makers knew little about what lay across the vast expanse of the Atlantic Ocean, nor the far reaches of the Asian continent, aside from stories that had trickled into Europe from traders.
Because such areas were unknown, and therefore dangerous, medieval maps have long been rumored to include the phrase "Here be dragons" over uncharted areas, with fantastical drawings of sea monsters decorating the edges. The truth is that the Latin phrase HC SVNT DRACONES has only been discovered on two surviving maps. The phrase, like the dragons themselves, is part of the lore.
Early cartographers were not only interested in the terrain of terra firma. Physicians have striven to understand brain structure and function for centuries, and early attempts at mapping regions of the brain responsible for specific functions have a lot in common with medieval maps: They're more art than science.
The origin of the pseudoscience of phrenology is credited to Austrian physicist Franz Joseph Gall. He believed that the structure of the skull reflected the underlying structures and functions of the brain—a theory that picked up some popular steam in the 19th century. Other phrenologists riffed on Gall's theories like jazz musicians, resulting in many different "authoritative" brain maps, like this one from 1898, which shows the emotion "aversion" to originate from the cerebellum.
Credit: Alesha Sivartha, “Plan of the Brain.” Public domain.
Like so many areas of science, we've come such a long, long way in a relatively short time. In May 2020, the Allen Institute published in Cell a 3D "reference atlas" of a complete mouse brain, constructed from a compilation of 1,675 mice. In June 2021, Google and Harvard University's Lichtman Laboratory released a detailed map of a tiny piece of human brain tissue, which they used to image and reconstruct thousands of neurons and millions of synapses in a dataset totaling 1.4 petabytes (and freely available online).
That is to say, the tools of science are only now capable of the sensitivity, speed, and storage capacity necessary to begin accurately charting the massive complexity of the brain. Meanwhile, new imaging techniques rapidly accelerate our understanding of brain structure and function.
This issue of Photonics Focus looks to the frontier of neuroscience, where new worlds are being discovered. We learn about optical tools for measuring olfaction, which may reveal new understanding of neurodegenerative diseases. We hear of researchers pairing large objective lenses with light-sheet microscopes for unprecedented live-organism imaging. And, we explore the recent revelations of neuroscience researchers who believe that the brain innately has the necessary building blocks for quantum communication.
This frontier is exciting, and there's little doubt that photonics will be a great enabler of tomorrow's neurologic cartography. There still be dragons in the brain, but they're quickly going extinct.
Gwen Weerts, Photonics Focus Editor-In-Chief
