David Hubel, noted neuroscientist and Nobel laureate, died on September 22th at the age of 87. In his collaboration with Torsten Wiesel that lasted several decades, David unlocked the door to understanding the transformation of visual information performed by the visual cortex. At the time Hubel and Wiesel began their studies, the emergent properties of sensory cortex were a mystery. The central concept of sensory processing, first defined by Sir Charles Sherrington, is the receptive field, the area of the sensory surface within which the appropriate stimulus could activate a neuron. At early stages in the visual pathway any given neuron’s receptive field is a small window on the visual scene. The question that bedeviled neuroscientists at the time was: What is the optimum visual stimulus to put within the receptive field to get neurons to respond? Hubel andWiesel found, through a fortuitous event in their search for the “code” of the visual cortex, that cortical neurons were selective for the orientation of line segments placed within their receptive fields. This discovery provided the first insight into how the visual cortex begins to analyze the contours that describe an object’s shape.
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