Journal of comparative physiology

, Volume 136, Issue 4, pp 291–299 | Cite as

Visual sensitivity of ground squirrels to spatial and temporal luminance variations

  • Gerald H. Jacobs
  • Barbara Blakeslee
  • Mark E. McCourt
  • R. B. H. Tootell


We have investigated the visual sensitivity of the California ground squirrel (Speromphilus beecheyi) to spatial and temporal luminance patterns. Spatial contrast sensitivity functions were determined in behavioral discrimination experiments in which the stimuli were sinusoidally-modulated luminance gratings. These squirrels were found to be maximally sensitive to spatial frequencies of about 0.7 cycles/ degree (c/d), and they are unable to discriminate gratings whose frequencies exceed 4 c/d. Similar results were obtained in electrophysiological experiments when the visually evoked cortical potential (VECP) was recorded from anesthetized squirrels. A third experiment involved tests of the ability of ground squirrels to discriminate square-wave gratings of much higher luminance (340 cd/m2). The finest gratings which were discriminable at this luminance level did not exceed 3.9–4.3 c/d and, thus, we conclude that the maximal spatial resolution of the California ground squirrel is about 4 c/d (corresponding to a bar separation of 7.5′). In another behavioral experiment the abilities of ground squirrels to discriminate sinusoidally flickering lights (mean luminance = 3.4 cd/m2) was measured. The results show that ground squirrels are maximally sensitive to lights flickering at a rate of about 18 Hz, and that the highest rates that are still discriminable are slightly above 60 Hz.


Contrast Sensitivity Ground Squirrel Luminance Level Visual Sensitivity High Luminance 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.





critical flicker frequency


visually evoked cortical potential


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Copyright information

© Springer-Verlag 1980

Authors and Affiliations

  • Gerald H. Jacobs
    • 1
  • Barbara Blakeslee
    • 1
  • Mark E. McCourt
    • 1
  • R. B. H. Tootell
    • 1
  1. 1.Department of PsychologyUniversity of CaliforniaSanta BarbaraUSA

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