David Hubel, neuroscientist who transformed understanding of vision, dies aged 87
Neuroscientist transformed understanding of vision and was jointly awarded the Nobel prize for physiology and medicine in 1981
David Hubel, who has died aged 87, was one of the greats of neuroscience. He discovered how individual brain cells convey the information that enables us to see the world, how these cells are organised in an exquisite crystalline structure and how they are moulded by experience in early life.
Besides transforming our understanding of vision and childhood visual disorders, his work created new insights into the detailed machinery of the brain.
Like many important scientific discoveries, Hubel's came from a close collaboration. He and Torsten Wiesel met as postdoctoral researchers in Johns Hopkins University, Baltimore, in 1958, and they continued to work together until Wiesel moved to Rockefeller University in 1983. In 1981 Hubel and Wiesel were together awarded the Nobel prize for physiology and medicine, along with Roger Sperry for his separate work on the hemispheres of the brain.
Before working with Wiesel, Hubel had applied his flair for tinkering with equipment to devise ultrafine electrodes for detecting nerve impulses from single cells, and the microdrive that allowed these electrodes to be precisely positioned in the brain.
At Johns Hopkins, they worked in the laboratory of Stephen Kuffler, whose pioneering experiments had shown how retinal cells in the eye respond to differences between patches of light and dark. Hubel and Wiesel attempted a similar approach to cells in the cat's visual cortex (the brain area that receives signals from the eyes).
Hubel, in his Nobel lecture, recounted how they tried in vain to activate a cell with projection slides showing dark and bright spots, but after many hours "we were inserting the glass slide ... when suddenly over the audiomonitor the cell went off like a machine gun". It was the edge of the slide, rather than anything on it, that proved key to activating the cell. Hubel and Wiesel found that visual cells in the cortex responded not to spots but to lines and edges, each cell having its own preferred orientation - responding, for instance, to 45-degree edges but not vertical or horizontal.
This discovery had enormous impact, establishing the ideas that the cortex was describing the visual world in terms of local features, that individual cells were tuned to respond to things such as slant, size and motion.
Hubel and Wiesel published their findings in a 1962 paper that was monumental in its scope. As well as orientation tuning, it described a hierarchy of cells with increasingly complex properties, built up by connections between cells sharing the same tuning that were arranged in a sequence of vertical columns in the cortex. A broader column structure organised signals from the left and right eyes, signals that were combined in binocular cells to give a sense of depth.
Their later work with monkeys showed even more clearly how the cortex was laid out as an orderly array of columnar modules, a structure now confirmed to be shared by the human brain.
These findings led the pair to a second strand of work, on development. They found that, if one eye was covered, the cortical columns that carried its signals shrunk away while the eye which retained visual experience came to dominate the cortex. If the two eyes pointed in different directions, each remained connected to the brain, but the cells which normally combined their signals were lost. These experiments mimicked the commonest eye disorders of children, amblyopia or "lazy eye" and strabismus or "squint". The changes in brain connections could only be induced (and reversed) by visual deprivation in a "sensitive period" during childhood.
This concept had a radical effect on clinical practice, making clear the importance of corrective treatment. It also provided a model for understanding how many other brain functions, such as language, develop through interaction between a programmed "wiring diagram" and early experience.
These discoveries have stimulated thousands of studies in neuroscience, ophthalmology and psychology. Hubel's work is lucidly and accessibly explained in his Nobel lecture and book Eye, Brain and Vision (1988).
He was born in Ontario, Canada to American parents; his father was a chemical engineer. He grew up in Montreal, where he gained a degree in physics and mathematics at McGill University. He then trained in medicine, and was inspired to turn to research in neurology and neurophysiology.
At McGill, Hubel met Ruth Izzard, and they married in 1953. She died this year. He is survived by three sons, Paul, Carl and Eric, and four grandchildren.