Neurophilosophy

Hubel’s Eye, Vision and Brain online

I’ve just discovered that the book Eye, Vision and Brain, by Nobel Prize winner David Hubel, is available online in its entirety.

Hubel is a neurophysiologist who performed some classic experiments with Torsten Wiesel, beginning in the late 1950s, on the development and functional properties of the visual system.

Using microelectrodes inserted into the primary visual cortex of anaesthetized cats, Hubel and Wiesel characterized the responses of cells to various visual stimuli. They found groups of cells which responded selectively to lines of a specific orientation, others which responded to lines moving in a specific direction, and yet others which had visual fields consisting of light spots on a dark background and vice versa.

These experiments also showed that cells in the visual system are organized into what Hubel and Wiesel called ocular dominance columns, which alternately receive sensory inputs from eithe rthe left or right eye, and which give the visual cortex a characteristic striped appearance (hence, the primary visual cortex is also referred to as the striate cortex).

Subsequently, Hubel and Wiesel carried out experiments in which kittens had one of their eyes sewn shut, in order to determine the effects on development of the visual brain. They found that monocular deprivation led to a failure of the development of ocular dominance columns receiving inputs from the closed eye, and to an expansion of the columns receiving inputs from the other eye.

This body of work contributed significantly to our understanding of the visual system, and Hubel and Wiesel later shared the 1981 Nobel Prize in Physiology. The first set of experiments showed how cells in the visual system act as detectors of contrast, edges and motion; the monocular deprivation experiments showed that sensory experience during a critical period of development is essential for proper wiring of the visual system, and have implications for the treatment of strabismus (squint) and related conditions.

Hubel’s book, which was first published in 1995, begins with a description of the structure and function of the retina and primary visual cortex and then goes on to describe the architecture of the rest of the visual cortex, colour vision. It concludes with a discussion of the effects of sensory deprivation on the development of the visual system, and how the findings can be applied by ophthalmologists.