Binocular combination at threshold: temporal filtering and summation of signals in separate ON and OFF channels

Mark A. Georgeson, Timothy S. Meese

Research output: Contribution to conferenceAbstract

Abstract

How does the brain combine spatio-temporal signals from the two eyes? We quantified binocular summation as the improvement in 2AFC contrast sensitivity for flickering gratings seen by two eyes compared with one. Binocular gratings in-phase showed sensitivity up to 1.8 times higher, suggesting nearly linear summation of contrasts. The binocular advantage decreased to 1.4 at lower spatial and higher temporal frequencies (0.25 cycle deg-1, 30 Hz). Dichoptic, antiphase gratings showed only a small binocular advantage, by a factor of 1.1 to 1.2, but no evidence of cancellation. We present a signal-processing model to account for the contrast-sensitivity functions and the pattern of binocular summation. It has linear sustained and transient temporal filters, nonlinear transduction, and half-wave rectification that creates ON and OFF channels. Binocular summation occurs separately within ON and OFF channels, thus explaining the phase-specific binocular advantage. The model also accounts for earlier findings on detection of brief antiphase flashes and the surprising finding that dichoptic antiphase flicker is seen as frequency-doubled (Cavonius et al, 1992 Ophthalmic and Physiological Optics 12 153 - 156). [Supported by EPSRC project GR/S74515/01].
Original languageEnglish
Publication statusPublished - 2007
Event13th European Conference on Visual Perception - Arezzo (IT), Italy
Duration: 27 Aug 200731 Aug 2007

Conference

Conference13th European Conference on Visual Perception
CountryItaly
CityArezzo (IT)
Period27/08/0731/08/07

Bibliographical note

Abstract published in ECVP 2007 Abstract Supplement, Perception 36 (Supplement), p.60. 0001-4966.

Keywords

  • brain
  • spatio-temporal signals
  • eyes
  • binocular summation
  • 2AFC contrast sensitivity
  • flickering gratings
  • binocular gratings in-phase
  • contrast-sensitivity functions
  • pattern of binocular summation

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