June 2021
Volume 62, Issue 8
Open Access
ARVO Annual Meeting Abstract  |   June 2021
Psychophysical Absolute Threshold in Mice is Inversely Related to Stimulus Duration
Author Affiliations & Notes
  • Sam LaMagna
    Ophthalmology and Visual Sciences, State University of New York Upstate Medical University, Syracuse, New York, United States
  • Yumiko Umino
    Ophthalmology and Visual Sciences, State University of New York Upstate Medical University, Syracuse, New York, United States
  • Ying Guo
    Ophthalmology and Visual Sciences, State University of New York Upstate Medical University, Syracuse, New York, United States
  • Eduardo C Solessio
    Ophthalmology and Visual Sciences, State University of New York Upstate Medical University, Syracuse, New York, United States
    Neuroscience and Physiology, State University of New York Upstate Medical University, Syracuse, New York, United States
  • Footnotes
    Commercial Relationships   Sam LaMagna, None; Yumiko Umino, None; Ying Guo, None; Eduardo Solessio, None
  • Footnotes
    Support  NEI R01 :EY026216; Research to Prevent Blindness; Lions Club of Central New York
Investigative Ophthalmology & Visual Science June 2021, Vol.62, 620. doi:
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    • Get Citation

      Sam LaMagna, Yumiko Umino, Ying Guo, Eduardo C Solessio; Psychophysical Absolute Threshold in Mice is Inversely Related to Stimulus Duration. Invest. Ophthalmol. Vis. Sci. 2021;62(8):620.

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      © ARVO (1962-2015); The Authors (2016-present)

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Abstract

Purpose : Stimulus duration and psychophysical threshold have an inverse linear relationship up to a critical duration, beyond which thresholds approach a constant value. While the mechanism governing this phenomenon in the amphibian visual system is understood, the mechanism setting the critical duration in mammals is unknown. An obstacle to defining this process is that the threshold-duration relationship has yet to be characterized in a genetically modifiable mammalian model organism. This study seeks to characterize the psychophysical threshold-duration relation in wild type mouse. We expected mice to exhibit a similar inverse-linear relationship as observed in humans and amphibian (Barlow 1958; Haldin et al 2009).

Methods : Absolute visual threshold was measured in 3 male C57 BL6/J mice using a modified 1-alternative forced choice task (Umino et al 2018). Dark adapted mice were trained, via operant conditioning, to visit one of two ports depending on whether a brief, dim stimulus was presented. Hit and False Alarm rates were calculated to determine a sensitivity index (d’) value for each stimulus intensity to construct psychometric functions. Mice first learned the task with a bright, 2s stimulus under light adapted conditions. Mice were then slowly introduced to briefer stimuli and dimmer conditions. After achieving a stable d’ value for a dim 60msec stimulus, multi-intensity trials for data collection began. Radiometric measures of stimulus intensity were converted to R*/rod/s (Lyubarsky et al 2004).

Results : Average d’ values were well fit to stimulus intensity with log-linear models (R2 ≥ 0.75; α = 0.05 ANOVA) at each duration (30ms-2s). At 30ms the absolute threshold, the intensity at the predicted d’ = 1, was 0.27 R*/rod/s (SE = +/- 0.11). Assuming total temporal summation, this is ~0.008 R*/rod. Each mouse exhibited an inverse linear relation between log-threshold and log-duration up to 250-500ms, below which, data is well fit with a linear equation on log-log axes, with slopes of -1.7, -2.0, and -2.9.

Conclusions : In wild type mice, absolute visual thresholds have an inverse relationship with stimulus duration. Unexpectedly, mice exhibit a supra-linear relation between stimulus duration and threshold. This study establishes a foundation to further study threshold-duration relationships in transgenic mouse lines, allowing us to dissect the neural circuits underlying temporal summation in the visual system.

This is a 2021 ARVO Annual Meeting abstract.

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