TY - JOUR
T1 - Binocularity in the little owl, athene noctua
T2 - II. properties of visually evoked potentials from the wulst in response to monocular and binocular stimulation with sine wave gratings
AU - Porciatti, Vittorio
AU - Fontanesi, Gigliola
AU - Raffaelli, Agnese
AU - Bagnoli, Paola
PY - 1990/1/1
Y1 - 1990/1/1
N2 - Visually evoked potentials (VEPs) have been recorded from the Wulst surface of the little owl, Athene noctua, in response to counterphase-reversal of sinusoidal gratings with different contrast, spatial frequency and mean luminance, presented either monocularly or binocularly. Monocular full-field stimuli presented to either eye evoked VEPs of similar amplitude, waveform and latency. Under binocular viewing, VEPs approximately doubled in amplitude without waveform changes. VEPs with similar characteristics could be obtained in response to stimulation of the contralateral, but not ipsilateral, hemifield. These results suggest that a 50% recrossing occurs in thalamic efferents and that different ipsilateral and contralateral regions converge onto the same Wulst sites. The VEP amplitude progressively decreased with increase of the spatial frequency beyond 2 cycles/degree, and the high spatial frequency cut-off (VEP acuity) was under binocular viewing (8 cycles/degree) higher than under monocular (5 cycles/degree) viewing (200 cd/m2, 45% contrast). The VEP acuity increased with increase in the contrast and decreased with reduction of the mean luminance. The binocular gain in both VEP amplitude and VEP acuity was largest at the lowest luminance levels. Binocular VEP summation occurred in the medium-high contrast range. With decreased contrast, both monocular and binocular VEPs progressively decreased in amplitude and tended to the same contrast threshold. The VEP contrast threshold depended on the spatial frequency (0.6-1.8% in the range 0.12-2 cycles/degree). Binocular VEPs often showed facilitatory interaction (binocular/monocular amplitude ratio >2), but the binocular VEP amplitude did not change either by changing the stimulus orientation (horizontal vs. vertical gratings) or by inducing different retinal disparities. These results indicate that VEPs can serve as a useful tool to measure visual performance in owls under different stimulus conditions in their operative range. Under low-luminance, high-contrast conditions, binocular visual performance, compared to monocular performance appears to improve by a factor of more than √2 (probability summation). This binocular advantage occurs independent of stereopsis.
AB - Visually evoked potentials (VEPs) have been recorded from the Wulst surface of the little owl, Athene noctua, in response to counterphase-reversal of sinusoidal gratings with different contrast, spatial frequency and mean luminance, presented either monocularly or binocularly. Monocular full-field stimuli presented to either eye evoked VEPs of similar amplitude, waveform and latency. Under binocular viewing, VEPs approximately doubled in amplitude without waveform changes. VEPs with similar characteristics could be obtained in response to stimulation of the contralateral, but not ipsilateral, hemifield. These results suggest that a 50% recrossing occurs in thalamic efferents and that different ipsilateral and contralateral regions converge onto the same Wulst sites. The VEP amplitude progressively decreased with increase of the spatial frequency beyond 2 cycles/degree, and the high spatial frequency cut-off (VEP acuity) was under binocular viewing (8 cycles/degree) higher than under monocular (5 cycles/degree) viewing (200 cd/m2, 45% contrast). The VEP acuity increased with increase in the contrast and decreased with reduction of the mean luminance. The binocular gain in both VEP amplitude and VEP acuity was largest at the lowest luminance levels. Binocular VEP summation occurred in the medium-high contrast range. With decreased contrast, both monocular and binocular VEPs progressively decreased in amplitude and tended to the same contrast threshold. The VEP contrast threshold depended on the spatial frequency (0.6-1.8% in the range 0.12-2 cycles/degree). Binocular VEPs often showed facilitatory interaction (binocular/monocular amplitude ratio >2), but the binocular VEP amplitude did not change either by changing the stimulus orientation (horizontal vs. vertical gratings) or by inducing different retinal disparities. These results indicate that VEPs can serve as a useful tool to measure visual performance in owls under different stimulus conditions in their operative range. Under low-luminance, high-contrast conditions, binocular visual performance, compared to monocular performance appears to improve by a factor of more than √2 (probability summation). This binocular advantage occurs independent of stereopsis.
KW - Binocular interaction
KW - Birds
KW - Pattern visually evoked potentials
KW - Visual pathways
UR - http://www.scopus.com/inward/record.url?scp=0025350475&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=0025350475&partnerID=8YFLogxK
U2 - 10.1159/000115855
DO - 10.1159/000115855
M3 - Article
C2 - 2340414
AN - SCOPUS:0025350475
VL - 35
SP - 40
EP - 48
JO - Brain, Behavior and Evolution
JF - Brain, Behavior and Evolution
SN - 0006-8977
IS - 1
ER -