Neural Mechanisms
Jul. 15, 2017 09:00 AM - 10:45 AM
Talk session 3, 2nd Lecture Room |
Increased ipRGC stimulation enhances spatial contrast sensitivity at low spatial frequencies in peripheral vision
Presentation Number:T21.21 Time:09:00 - 09:15 Abstract Number:0048 |
Sung-en Chien 1, Akiko Matsumoto 2, Wakayo Yamashita 2, Sei-ichi Tsujimura 2, Su-Ling Yeh 1, 3, 4, *
1Department of Psychology, National Taiwan University, Taipei, Taiwan
2Faculty of Science and Engineering, Kagoshima University, Kagoshima, Japan
3Graduate Institute of Brain and Mind Sciences, National Taiwan University, Taipei, Taiwan
4Neurobiology and Cognitive Science Center, National Taiwan University, Taipei, Taiwan
A recently discovered third receptor type, intrinsically photosensitive retinal ganglion cell (ipRGC), has attracted much attention because it affects circadian rhythm and sleep via signaling environmental light level. Nevertheless, few studies have examined whether ipRGCs also affect spatial vision. Here we investigate whether ipRGC stimulation in background affects human contrast sensitivity function (CSF), which varies with background luminance. A Gabor was presented at either left or right side of fixation. Participants were asked to perform a position-judgment task with the two-alternative forced-choice procedure. We measured CSFs at low spatial frequencies in periphery by adopting the silent substitution method to keep background color and luminance silent while manipulating ipRGC stimulation. Three conditions were tested: control, ipRGC-high, and light-flux-high condition. In ipRGC-high condition, only ipRGC stimulation was increased compared to control condition. In light-flux-high condition, both ipRGC and cone stimulations were increased. The results showed that increased ipRGC stimulation enhanced spatial contrast sensitivity while increased cone stimulation decreased it. Furthermore, increased ipRGC stimulation enhanced a spatial tuning in sensitivity according to changes in shape of the receptive field. Our findings indicate that, contrary to previous findings that ipRGCs contribute mainly to non-visual functions, ipRGCs also contributed to fundamental properties of spatial vision.
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Difference in brain activities for unique and cardinal hues investigated by fMRI
Presentation Number:T21.22 Time:09:15 - 09:30 Abstract Number:0026 |
Ichiro Kuriki 1, *, Wakiko Maemura 1, Kazumichi Matsumiya 1, Satoshi Shioiri 11Tohoku University
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Monocular orientation-deprivation in nature viewing strengthens the deprived eye
Presentation Number:T21.23 Time:09:30 - 09:45 Abstract Number:0015 |
Yonghua Wang 1, Reza Farivar 2, Jia Qu 1, Jiawei Zhou 1, *, Robert Hess 21Wenzhou Medical University 2McGill University
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Orientation tuning in V1 is contrast invariant on short, but not long, timescales
Presentation Number:T21.24 Time:09:45 - 10:00 Abstract Number:0014 |
Masoud Ghodrati 1, Elizabeth Zavitz 1, Marcello Rosa 1, Nicholas Price 1, *1Monash University
Orientation tuning in primary visual cortex (V1) neurons is contrast-invariant; while increasing contrast drives higher firing rates, orientation tuning bandwidths do not change. However, previous studies have not examined the time course of contrast adaptation, and whether stable orientation tuning is maintained as firing rates continually change.
We recorded extracellular V1 activity in anaesthetised marmosets using two orientation reverse correlation paradigms, in which gratings with random orientation were updated every 16 ms. In the “slow adaptation” paradigm, four contrasts were tested, but contrast was fixed for 30 minutes. As shown previously, orientation tuning was contrast invariant. However, our ability to predict orientation from the neuronal responses using a linear decoder increased with contrast.
In the “rapid adaptation” paradigm, luminance and contrast were changed every 5 seconds. Spiking rates increased immediately after contrast-increments, and then decayed exponentially. Our ability to decode orientation was highest when contrast was high, but surprisingly, within a period of constant contrast, spiking rate changed with no concomitant change in decoding performance.
This dramatically demonstrates that adaptation within a few milliseconds allows neurons to encode orientation nearly independently contrast and firing rate; but on longer timescales, orientation encoding is contrast dependent, and correlated with mean spiking rate.
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Receptive field mapping in the dorsolateral frontal cortex of marmosets (Callithrix jacchus)
Presentation Number:T21.25 Time:10:00 - 10:15 Abstract Number:0001 |
Azadeh Feizpour 1, *, Declan Rowley 1, Tristan Chaplin 1, Piotr Majka 1, Leo Lui 1, Nicholas Price 1, Hsin-Hao Yu 1, Marcello Rosa 11Monash Uni, Dept. of Physiology
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Visuotopy and feature selectivity of neurons in the extrastriate dorsomedial (DM) area of the marmoset monkey
Presentation Number:T21.26 Time:10:15 - 10:30 Abstract Number:0133 |
Hsin-Hao Yu 1, *, Declan Rowley 1, Elizabeth Zavitz 1, Nicholas Price 1, Marcello Rosa 11Monash University
The organization of the "third-tier" areas (Brodmann's area 19) in the primate visual cortex has been an issue of controversy. While the traditional view is that in small New World monkeys, adjoining the rostral border of dorsal V2 is the dorsomedial (DM) area, representing both the upper and the lower quadrants of the visaul field (Allman & Kaas, 1971), some researchers proposed a macaque-like area V3 representing only the lower quadrant. We densely mapped the visuotopy in this cortical region of the marmoset monkey, using 10-by-10 multi-electrode arrays, and were able to precisely duplicate the DM-map suggested by Rosa & Schmid (1995). Furthermore, we used white noise analysis to quantitatively model DM neurons' response characteristics, and showed that their responses could be approximated by small numbers of filters resembling Gabor functions, similar to the orientation-selective complex cells in V1. Finally, penetrations thought the medial segment of DM showed that although most DM neurons in the dorsal surface of DM are not direction selective, direction selectivity increases with eccentricity in DM. The results are consistent with the idea that DM is an intermediate-level area mediating functions related to both the dorsal and the ventral pathways.
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Visual responses of primate orbitofrontal neurons contribute to preference judgment
Presentation Number:T21.27 Time:10:30 - 10:45 Abstract Number:0082 |
Shintaro Funahashi 1, *1Kyoto University
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