Mostafa, JakariaPorter, JasonQueener, Hope M.Ostrin, Lisa A....
10页
查看更多>>摘要：Previous findings regarding intrinsically photosensitive retinal ganglion cell (ipRGC) function after traumatic brain injury (TBI) are conflicting. We examined ipRGC-driven pupil responses in civilian TBI and control participants using two pupillography protocols that assessed transient and adaptive properties: (1) a one second (s) long wavelength "red" stimulus (651 nm, 133 cd/m2) and 10 increasing intensities of 1 s short wavelength "blue" stimuli (456 nm, 0.167 to 167 cd/m2) with a 60 s interstimulus interval, and (2) two minutes of 0.1 Hz red stimuli (33 cd/m2), followed by two minutes of 0.1 Hz blue stimuli (16 cd/m2). For Protocol 1, constriction amplitude and the 6 s post illumination pupil response (PIPR) were calculated. For Protocol 2, amplitudes and peak velocities of pupil constriction and redilation were calculated. For Protocol 1, constriction amplitude and the 6 s PIPR were not significantly different between TBI patients and control subjects for red or blue stimuli. For Protocol 2, pupil constriction amplitude attenuated over time for red stimuli and potentiated over time for blue stimuli across all subjects. Constriction and redilation velocities were similar between groups. Pupil constriction amplitude was significantly less in TBI patients compared to control subjects for red and blue stimuli, which can be attributed to age-related differences in baseline pupil size. While TBI, in addition to age, may have contributed to decreased baseline pupil diameter and constriction amplitude, responses to blue stimulation suggest no selective damage to ipRGCs.
Mostafa, JakariaPorter, JasonQueener, Hope M.Ostrin, Lisa A....
10页
查看更多>>摘要：Previous findings regarding intrinsically photosensitive retinal ganglion cell (ipRGC) function after traumatic brain injury (TBI) are conflicting. We examined ipRGC-driven pupil responses in civilian TBI and control participants using two pupillography protocols that assessed transient and adaptive properties: (1) a one second (s) long wavelength "red" stimulus (651 nm, 133 cd/m2) and 10 increasing intensities of 1 s short wavelength "blue" stimuli (456 nm, 0.167 to 167 cd/m2) with a 60 s interstimulus interval, and (2) two minutes of 0.1 Hz red stimuli (33 cd/m2), followed by two minutes of 0.1 Hz blue stimuli (16 cd/m2). For Protocol 1, constriction amplitude and the 6 s post illumination pupil response (PIPR) were calculated. For Protocol 2, amplitudes and peak velocities of pupil constriction and redilation were calculated. For Protocol 1, constriction amplitude and the 6 s PIPR were not significantly different between TBI patients and control subjects for red or blue stimuli. For Protocol 2, pupil constriction amplitude attenuated over time for red stimuli and potentiated over time for blue stimuli across all subjects. Constriction and redilation velocities were similar between groups. Pupil constriction amplitude was significantly less in TBI patients compared to control subjects for red and blue stimuli, which can be attributed to age-related differences in baseline pupil size. While TBI, in addition to age, may have contributed to decreased baseline pupil diameter and constriction amplitude, responses to blue stimulation suggest no selective damage to ipRGCs.
Bellagarda, Cayla A.Dickinson, J. EdwinBell, JasonBadcock, David R....
9页
查看更多>>摘要：Symmetry perception in dot patterns is tolerant to temporal delays of up to 60 ms within and between element pairs. However, it is not known how factors effecting symmetry discrimination in static patterns might affect temporal integration in dynamic patterns. One such feature is luminance polarity. Using dynamic stimuli with increasing temporal delay (SOA) between the onset of the first and second element in a symmetric pair, we investigated how four different luminance-polarity conditions affected the temporal integration of symmetric patterns. All four luminance polarity conditions showed similar upper temporal limits of approximately 60 ms. However psychophysical performance over all delay durations showed significantly higher symmetry thresholds for unmatched-polarity patterns at short delays, but also significantly less sensitivity to increasing temporal delay relative to matched-polarity patterns. These varying temporal windows are consistent with the involvement of a fast, sensitive first-order mechanism for matched-polarity patterns, and a slower, more robust second-order mechanism for unmatched-polarity patterns. Temporal integration windows for unmatched-polarity patterns were not consistent with performance expected from attentional mechanisms alone, and instead supports the involvement of second-order mechanisms that combines information from ON and OFF channels.
Bellagarda, Cayla A.Dickinson, J. EdwinBell, JasonBadcock, David R....
9页
查看更多>>摘要：Symmetry perception in dot patterns is tolerant to temporal delays of up to 60 ms within and between element pairs. However, it is not known how factors effecting symmetry discrimination in static patterns might affect temporal integration in dynamic patterns. One such feature is luminance polarity. Using dynamic stimuli with increasing temporal delay (SOA) between the onset of the first and second element in a symmetric pair, we investigated how four different luminance-polarity conditions affected the temporal integration of symmetric patterns. All four luminance polarity conditions showed similar upper temporal limits of approximately 60 ms. However psychophysical performance over all delay durations showed significantly higher symmetry thresholds for unmatched-polarity patterns at short delays, but also significantly less sensitivity to increasing temporal delay relative to matched-polarity patterns. These varying temporal windows are consistent with the involvement of a fast, sensitive first-order mechanism for matched-polarity patterns, and a slower, more robust second-order mechanism for unmatched-polarity patterns. Temporal integration windows for unmatched-polarity patterns were not consistent with performance expected from attentional mechanisms alone, and instead supports the involvement of second-order mechanisms that combines information from ON and OFF channels.
查看更多>>摘要：An object is perceived as larger when it is surrounded by smaller context objects than when it is surrounded by larger context objects. The origin of this well-known phenomenon, called as Ebbinghaus or Titchener circles illusion, is still puzzling. Here we introduce a basic explanation of how this illusion could emerge and provide some preliminary empirical support for this idea. In essence, we suggest that changes in the figural extent and in the spatial frequency of the stimulus pattern entail adjustments of the size and resolution of the attentional field, which are accompanied by changes in spatial coding. This approach is consistent with previous observations and can enable a deeper understanding of geometric illusions.
查看更多>>摘要：An object is perceived as larger when it is surrounded by smaller context objects than when it is surrounded by larger context objects. The origin of this well-known phenomenon, called as Ebbinghaus or Titchener circles illusion, is still puzzling. Here we introduce a basic explanation of how this illusion could emerge and provide some preliminary empirical support for this idea. In essence, we suggest that changes in the figural extent and in the spatial frequency of the stimulus pattern entail adjustments of the size and resolution of the attentional field, which are accompanied by changes in spatial coding. This approach is consistent with previous observations and can enable a deeper understanding of geometric illusions.
查看更多>>摘要：Adaptation to a natural face attribute such as a happy face can bias the perception of a subsequent face in this dimension such as a neutral face. Such face adaptation aftereffects have been widely found in many natural facial categories. However, how temporally tuned mechanisms could control the temporal dynamics of natural face adaptation aftereffects remains unknown. To address the question, we used a deadaptation paradigm to examine whether the spontaneous recovery of natural facial aftereffects would emerge in four natural facial categories including variable categories (emotional expressions in Experiment 1 and eye gaze in Experiment 2) and invariable categories (facial gender in Experiment 3 and facial identity in Experiment 4). In the deadaptation paradigm, participants adapted to a face with an extreme attribute (such as a 100% angry face in Experiment 1) for a relatively long duration, and then deadapted to a face with an opposite extreme attribute (such as a 100% happy face in Experiment 1) for a relatively short duration. The time courses of face adaptation aftereffects were measured using a top-up manner. Deadaptation only masked the effects of initial longer-lasting adaptation, and the spontaneous recovery of adaptation aftereffects was observed at the post-test stage for all four natural facial categories. These results likely indicate that the temporal dynamics of adaptation aftereffects of natural facial categories may be controlled by multiple temporally tuned mechanisms.
查看更多>>摘要：Adaptation to a natural face attribute such as a happy face can bias the perception of a subsequent face in this dimension such as a neutral face. Such face adaptation aftereffects have been widely found in many natural facial categories. However, how temporally tuned mechanisms could control the temporal dynamics of natural face adaptation aftereffects remains unknown. To address the question, we used a deadaptation paradigm to examine whether the spontaneous recovery of natural facial aftereffects would emerge in four natural facial categories including variable categories (emotional expressions in Experiment 1 and eye gaze in Experiment 2) and invariable categories (facial gender in Experiment 3 and facial identity in Experiment 4). In the deadaptation paradigm, participants adapted to a face with an extreme attribute (such as a 100% angry face in Experiment 1) for a relatively long duration, and then deadapted to a face with an opposite extreme attribute (such as a 100% happy face in Experiment 1) for a relatively short duration. The time courses of face adaptation aftereffects were measured using a top-up manner. Deadaptation only masked the effects of initial longer-lasting adaptation, and the spontaneous recovery of adaptation aftereffects was observed at the post-test stage for all four natural facial categories. These results likely indicate that the temporal dynamics of adaptation aftereffects of natural facial categories may be controlled by multiple temporally tuned mechanisms.
查看更多>>摘要：The visual system is sensitive to statistical properties of complex scenes and can encode feature probability distributions in detail. But does the brain use these statistics to build probabilistic models of the ever-changing visual input? To investigate this, we examined how observers temporally integrate two different orientation distributions from sequentially presented visual search trials. If the encoded probabilistic information is used in a Bayesian optimal way, observers should weigh more reliable information more strongly, such as feature distributions with low variance. We therefore manipulated the variance of the two feature distributions. Participants performed sequential odd-one-out visual search for an oddly oriented line among distractors. During successive learning trials, the distractor orientations were sampled from two different Gaussian distributions on alternating trials. Then, observers performed a 'test trial' where the orientations of the target and distractors were switched, allowing us to assess observer's internal representation of distractor distributions based on changes in response times. In three experiments we observed that observer's search times on test trials depended mainly on the very last learning trial, indicating a strong recency effect. Since temporal integration has been previously observed with this method, we conclude that when the input is unreliable, the visual system relies more on the most recent stimulus. This indicates that the visual system prefers to utilize sensory history when the statistical properties of the environment are relatively stable.
查看更多>>摘要：The visual system is sensitive to statistical properties of complex scenes and can encode feature probability distributions in detail. But does the brain use these statistics to build probabilistic models of the ever-changing visual input? To investigate this, we examined how observers temporally integrate two different orientation distributions from sequentially presented visual search trials. If the encoded probabilistic information is used in a Bayesian optimal way, observers should weigh more reliable information more strongly, such as feature distributions with low variance. We therefore manipulated the variance of the two feature distributions. Participants performed sequential odd-one-out visual search for an oddly oriented line among distractors. During successive learning trials, the distractor orientations were sampled from two different Gaussian distributions on alternating trials. Then, observers performed a 'test trial' where the orientations of the target and distractors were switched, allowing us to assess observer's internal representation of distractor distributions based on changes in response times. In three experiments we observed that observer's search times on test trials depended mainly on the very last learning trial, indicating a strong recency effect. Since temporal integration has been previously observed with this method, we conclude that when the input is unreliable, the visual system relies more on the most recent stimulus. This indicates that the visual system prefers to utilize sensory history when the statistical properties of the environment are relatively stable.
NSTL
Elsevier