Eric L. Schwartz

Eric L. Schwartz

Eric L. Schwartz is Professor of Cognitive and Neural Systems, Professor of Electrical and Computer Engineering, and Professor of Neurobiology and Neuroanatomy at Boston University. His research interest is in computational neuroscience, machine vision, neuroanatomy, and neural modeling. He made major contributions in topographic mapping in primate visual cortex using computational and anatomical approaches.

Schwartz (1980) made a similar attempt as Whitman Richards (1971) to explain the fortifications patterns, but came to a different conclusion. In 1977, Hubel and Wiesel suggested that so-called cortical columns are packed in essentially linear parallel stripes, which Hubel (1988) subsequently referred to as the "ice-cube" model.

Cortical column vertical arrangement (not necessarily of circular shape) of neurons that have similar response properties.

The definition of a cortical column is best quoted from Geoffrey J. Goodhill and Miguel Á. Carreira-Perpiñán (2002): "In many regions of the cortex, neural response properties remain relatively constant as one moves perpendicular to the surface of the cortex, while they vary in a direction parallel to the cortex. Such columnar organization is particularly evident in the visual system, in the form of ocular dominance and orientation columns."

On the basis of the "ice-cube" model, Schwartz argued that the approaching wave would initially affect cortical cells which possess the highest spontaneous activity. Such cells are located in a special layer of the cortex (IVc). In this layer, the afferent inputs to the cortex largely terminate. Cells in this layer possess concentric circular receptive field structure. Simple cells in the surrounding laminae possess fairly low spontaneous discharge rate, and presumably are strongly inhibited by intracortical inhibition. Therefore, those cells which converge to orientations which are perpendicular to the wavefront will be inhibited earliest by the advancing wave. Their excitatory input to the surrounding simple cells will be dismissed, and the activity of these cells will be depressed. Correspondingly, their neighbors on either side will be disinhibited, and will experience an elevation in firing rate. These columns correspond to orientations which are in the range of 30° to 60° from perpendicular to the advancing front, and thus would be perceived as the jagged fortification.

References

Goodhill GJ, Carreira-Perpiñán MÁ. Cortical Columns. Invited article in the Encyclopedia of Cognitive Science (L. Nadel, ed.), Macmillan, 2002; 1: 845-851.
Hubel DH, Wiesel TN. Ferrier lecture. Functional architecture of macaque monkey visual cortex. Proc R Soc Lond B Biol Sci 1977; 198: 11-59.
Hubel DH. Eye, brain, and vision. New York: WH Freeman 1988.
Richards W. The fortification illusions of migraines. Sci Am 1971; 224: 88-96.
Schwartz EL. A quantitative model of the functional architecture of human striate cortex with application to visual illusion and cortical texture analysis. Biol Cybern 1980; 37: 63-76.

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