Purpose. In cats, vernier acuity thresholds are thought to be limited by neurons in the primary visual cortex (Berkley & Sprague, 1979; Swindale & Cynader, 1986, 1989). We assessed vernier acuity in male and female adult rats to investigate whether sex differences in the anatomy of the rat visual cortex (Reid & Juraska, 1992, 1995; Seymoure & Juraska, 1992) are reflected in this visual ability. Method. Seven adult male and female littermate pairs of Long-Evans rats were tested in a jumping stand with 10x10cm cards (multiple black and white gratings of 1.1c/deg per stripe) presented at 40cm behind 2 collapsing landing platforms. For the vernier stimuli, the gratings were offset across the middle of the stimuli and always presented behind a locked platform. An incorrect jump to the control gratings caused that platform to collapse. The rats were tested on 7 vernier offset sizes that ranged from 21.8 to 12.1 mins/arc. Fifty trials were given for each offset size, with the vernier and control gratings randomly presented on each side. A score of 34 or more correct detections for each size was considered as significant according to a binomial distribution. Results. The vernier threshold for 6 female rats was 15.6 min/arc while 5 male rats had a threshold of 13.6 min/arc. One female and two males had a vernier threshold of 12.8 mm/arc. No rats could detect vernier offsets of 12.1 min/arc above chance. Conclusions. All of the animals had vernier acuity thresholds that equaled or exceeded established limits of grating acuity for pigmented rats. The majority of male rats had lower vernier thresholds than female rats, which may be influenced by the greater number of neurons (18%) in the male binocular cortex (Oc1B).
|Original language||English (US)|
|Journal||Investigative Ophthalmology and Visual Science|
|State||Published - Feb 15 1996|
ASJC Scopus subject areas