The human ear is remarkable in its ability to discriminate various properties of sound. As a result of genetic conditions, drug exposure, infection, and noise damage, however, nearly 30 million Americans suffer from hearing problems that range from mild difficulty in understanding speech to profound deafness. Remarkably, the hair cell, a single type of cell, is responsible for the ear's outstanding capabilities and for its vulnerabilities. Each hair cell is a mechanical sensor in the internal ear that responds when sound or acceleration deflects its sensitive structure, the hair bundle. Recent results indicate that the hair cell is not only the passive recipient of sound, but also an active amplifier.
Most people can recognize a familiar face or voice within a fraction of a second.
By contrast, the most powerful computers perform such tasks poorly. Part of the answer to this question comes from the observation that the brain divides and modifies the sensory information at each stage of processing. For example, in the visual system, different aspects such as color, motion, and depth are analyzed separately. How the various attributes of a complex sensation are divided and reassembled is an area of active research.