Spatiotemporal integration of light by the cat X-cell center under photopic and scotopic conditions

J. B. Troy*, D. L. Bohnsack, J. Chen, X. Guo, C. L. Passaglia

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


Visual responses to stimulation at high temporal frequency are generally considered to result from signals that avoid light adaptive gain adjustment, simply reflecting linear summation of luminance. Under conditions of high photopic illuminance, the center of the receptive field of the cat X-cell has been shown to expand in size when stimulated at high temporal frequency, raising the possibility that there is spatiotemporal interaction in luminance summation. Here we show that this expansion maintains constant the product of the center's luminance summing area and the temporal period of luminance modulation, implying that spatial and temporal integration of luminance can be traded for one another by the X-cell center. As such the X-cell has a spatiotemporal window for luminance integration that fuses the classical concepts of a spatial window of luminance integration (Ricco's Law) with a temporal window of luminance integration (Bloch's Law). We were interested to determine whether this tradeoff between spatial and temporal summation of luminance occurs also at lower light levels, where the temporal-frequency bandwidth of the X-cell is narrower. We found that it does not. Center radius does not expand with temporal frequency under either low photopic or scotopic conditions. These results are discussed within the context of the known retinal circuitry that underlies the X-cell center for photopic and scotopic conditions.

Original languageEnglish (US)
Pages (from-to)493-500
Number of pages8
JournalVisual Neuroscience
Issue number4
StatePublished - Jul 2005


  • Contrast sensitivity
  • Retinal ganglion cell
  • Rod and cone inputs
  • Temporal frequency
  • Visual adaptation

ASJC Scopus subject areas

  • Neuroscience(all)


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