FIG. 36.20

How does the retina process visual information?

BACKGROUND In the 1950s, the American neurophysiologist Stephen Kuffler was interested in understanding how the retina helps to process light information before it is sent to the brain. He focused on the activity of ganglion cells in the retina because they receive input from the photoreceptors and bipolar cells.

EXPERIMENT Kuffler stimulated different regions of a cat’s retina with localized points of light while recording the action potentials produced by ganglion cells.

RESULTS Kuffler found that there are two types of ganglion cell: on-center and off-center cells. On-center ganglion cells fire more action potentials when light shines on the center of the cell’s receptive field compared to the surrounding region, and off-center cells fire more when light is shown in the periphery and less on the center. These patterns are explained by lateral inhibition of input by the photoreceptors and varying excitation or inhibition of bipolar cells to the ganglion cells in the retina.

FOLLOW-UP WORK In the 1960s, Hubel and Wiesel found similar center–surround neural receptive fields, though with enhanced opposition, in part of the thalamus and in the visual cortex of the brain. Cells with these fields enable cats and other mammals to detect shapes of a given orientation moving through their visual field. Similar center–surround receptive fields have also been found in the somatosensory and auditory cortex, highlighting the use of lateral inhibition to enhance sensory acuity and edge detection. Other studies have found similar center–surround sensory processing in invertebrates and other vertebrates.

SOURCES Kuffler, S. W. 1953. “Discharge Patterns and Functional Organization of Mammalian Retina.” Journal of Neurophysiology 16:37–68; Hubel, D. H. 1963. “The Visual Cortex of the Brain.” Scientific American 209:54–62.