Publications by authors named "Pi-Chun Huang"

33 Publications

Intracerebral transplantation of autologous adipose-derived stem cells for chronic ischemic stroke: A phase I study.

J Tissue Eng Regen Med 2022 Jan 21;16(1):3-13. Epub 2021 Oct 21.

Department of Neurosurgery, Bioinnovation Center, Tzu Chi Foundation, Buddhist Tzu Chi General Hospital, Tzu Chi University, Hualien, Taiwan, ROC.

Current therapy does not provide significant benefits for patients with chronic stroke. Pre-clinical studies suggested that autologous adipose-derived stem cells have benefits for the treatment of chronic stroke. This Phase I open-label study was conducted to demonstrate the safety and efficacy of autologous adipose-derived stem cells (GXNPC1) in chronic stroke. Three patients with chronic stroke were treated with stereotactic implantation of autologous adipose-derived stem cells (1 × 10 cells). The primary endpoints of safety evaluation included adverse events, over a 6 months post-implantation period. The secondary endpoints included improvements in neurological functions. Evolutional change of brain parenchyma was also followed with magnetic resonance imaging (MRI). All three participants improved significantly at 6 months follow-up. The extent of improvement from pre-treatment was: National Institutes of Health Stroke Scale improved 5-15 points, Barthel Index: 25-50 points, Berg balance scale 0-21 points and Fugl-Meyer modified sensation 3-28 points. All three patients had signal change along the implantation tract on MRI one month after surgery. There is no related safety issue through 6 months observation. Clinical measures of neurological symptoms of these patients with chronic stroke improved at 6 months without adverse effects after implantation of autologous adipose-derived stem cells (GXNPC1), which might be correlated with post-implantation changes on brain MRI. Clinical Trial Registration-URL: https://clinicaltrials.gov/ct2/show/NCT02813512?term=ADSC&cond=Stroke&cntry=TW&draw=2&rank=1 Unique identifier: NCT02813512.
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http://dx.doi.org/10.1002/term.3256DOI Listing
January 2022

Stimulus temporal uncertainty balances intersensory dominance.

Psychon Bull Rev 2021 Dec 22;28(6):1874-1884. Epub 2021 Jun 22.

Department of Psychology, National Cheng Kung University, 1 University Road, Tainan City, 701, Taiwan.

Vision is typically dominant over audition or touch in human adults. One classic example is the Colavita visual dominance effect: The presentation of a tone sometimes goes undetected when it is paired with a flash even though it is well detected when presented alone. We investigated whether the Colavita visual dominance effect is modulated by stimulus uncertainty in the temporal and spatial domains. In a simple discrimination task, participants were asked to press a predesignated key when detecting a flash, another key when detecting a tone, and both keys when detecting both a flash and a tone. Temporal uncertainty was increased by introducing temporal jitter between trials (Experiment 1), and spatial uncertainty was increased by shifting the flash to different locations (Experiment 2). The Colavita visual dominance effect was reduced when temporal uncertainty was increased, while it remained similar when spatial uncertainty was increased. We therefore demonstrate a novel consideration, where increasing temporal uncertainty balances the competition between vision and audition, suggesting that people's degree of sensory dominance is malleable. Our result therefore highlights the concept that intersensory competition is susceptible to the temporal predictability of the stimulus, which provides critical insights into the design of effective warning systems in the field of ergonomics.
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http://dx.doi.org/10.3758/s13423-021-01959-0DOI Listing
December 2021

Global shape perception contributes to crossmodal correspondences.

J Exp Psychol Hum Percept Perform 2021 Mar 25;47(3):357-371. Epub 2021 Jan 25.

Department of Experimental Psychology, University of Oxford.

The Bouba/Kiki effect constitutes a classic sound-shape correspondence, with the meaningless sounds "Bouba" and "Kiki" being mapped onto smooth and spiky patterns, respectively. While it is commonly believed that the Bouba/Kiki effect is driven by the local rounded and angular features of a pattern, here we investigated the importance of an alternative level of visual processing-namely the global contours. We adopted compound radial frequency (RF) patterns and segmented them into convexities (outward curves) or concavities (inward curves). Note that convexities are more informative in terms of inferring the global contour than concavities. When the perceptual grouping of segments was facilitated by increasing their length, the grouping of convexities was more efficient than that of concavities as manifested by the closer matching judgments to the compound RF patterns. When we interfered with the perceptual grouping of segments by rotating each segment by 180°, the matching consensus of convexities was higher when they were presented in the original than in the reversed orientation. Hence, the Bouba/Kiki effect was susceptible to the factors modulating the perceptual grouping process going from segments to the global contour, suggesting that the Bouba/Kiki effect may occur at the global level of shape perception. Sound-shape correspondences would therefore seem to be expressed at multiple levels of information processing, furthering our understanding of the development, underpinning neural mechanisms, and applications of crossmodal correspondences. (PsycInfo Database Record (c) 2021 APA, all rights reserved).
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http://dx.doi.org/10.1037/xhp0000811DOI Listing
March 2021

Reduced Monocular Luminance Increases Monocular Temporal Synchrony Threshold in Human Adults.

Invest Ophthalmol Vis Sci 2020 07;61(8)

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Purpose: The purpose of this study was to present our investigation of the influence of reduced monocular luminance on monocular and dichoptic temporal synchrony processing in healthy adults.

Methods: Ten adults with normal or corrected to normal visual acuity participated in our psychophysical study. The temporal synchrony threshold in dichoptic (experiment 1), monocular (experiment 2), and binocular (experiment 3) viewing configurations was obtained from each observer. Four flickering Gaussian dots (one synchronous and one asynchronous pair of two dots) were displayed, from which the observers were asked to identify the asynchronous pair. The temporal phase lag in the signal pair (asynchronous) but not in the reference pair (synchronous) was varied. In addition, a neutral density (ND) filter of various intensities (1.3 and 2.0 log units) was placed before the dominant eye throughout the behavioral measurement. In the end, dichoptic, monocular, and binocular thresholds were measured for each observer.

Results: With decreasing monocular luminance, the dichoptic threshold (2 ND vs. 0 ND, P < 0.001; 2 ND vs. 1.3 ND P = 0.001) and monocular threshold (2 ND vs. 0 ND, P < 0.001; 2 ND vs. 1.3 ND, P = 0.003) increased; however, the bincoular threshold remained unaffected (P = 0.576).

Conclusions: Reduced luminance induces delay and disturbs the discrimination of temporal synchrony. Our findings have clinical implications in visual disorders.
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http://dx.doi.org/10.1167/iovs.61.8.1DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7425744PMC
July 2020

Short-Term Deprivation Does Not Influence Monocular or Dichoptic Temporal Synchrony at Low Temporal Frequency.

Front Neurosci 2020 28;14:402. Epub 2020 Apr 28.

State Key Laboratory of Ophthalmology, Optometry and Vision Science, School of Ophthalmology and Optometry and Eye hospital, Wenzhou Medical University, Wenzhou, China.

Studies on binocular combination and rivalry show that short-term deprivation strengthens the contribution of the deprived eye in binocular vision. However, whether short-term monocular deprivation affects temporal processing is not clear. To address this issue, we conducted a study to investigate the effect of monocular deprivation on dichoptic temporal synchrony. We tested ten adults with normal vision and patched their dominant eye with an opaque patch for 2.5 h. A temporal synchrony paradigm was used to measure if temporal synchrony thresholds change as a result of monocular pattern deprivation. In this paradigm, we displayed two pairs of Gaussian blobs flickering at 1 Hz with either the same or different phased- temporal modulation. In Experiment 1, we obtained the thresholds for detecting temporal asynchrony under dichoptic viewing configurations. We compared the thresholds for temporal synchrony between before and after monocular deprivation and found no significant changes of the interocular synchrony. In Experiment 2, we measured the monocular thresholds for detecting temporal asynchrony. We also found no significant changes of the monocular synchrony of either the patched eye or the unpatched eye. Our findings suggest that short-term monocular deprivation induced-plasticity does not influence monocular or dichoptic temporal synchrony at low temporal frequency.
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http://dx.doi.org/10.3389/fnins.2020.00402DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7198853PMC
April 2020

Abnormal Monocular and Dichoptic Temporal Synchrony in Adults with Amblyopia.

Invest Ophthalmol Vis Sci 2019 11;60(14):4858-4864

Department of Psychology, National Cheng Kung University, Tainan, Taiwan.

Purpose: We investigate temporal synchrony within one eye and between both eyes in adults with amblyopia.

Methods: Eight adult amblyopes (range, 19.88-27.81 years old; median, 22.86 years old) and 12 age-matched adults with normal vision (range, 21.2-50.30 years old; median, 23.78 years old) participated in the experiment. We showed two pairs of Gaussian blobs flickering at 1 Hz as visual stimuli, one pair with the same temporal phase modulation (i.e., the reference) and another pair with a distinct temporal phase (i.e., the signal). We employed the constant stimuli method to measure the minimum degree of temporal phase (temporal synchrony threshold), at which participants were able to discriminate the signal pair under binocular, monocular, and dichoptic viewing configurations.

Results: The temporal synchrony threshold was different across the six configurations (P = 0.001). There was also an interaction between the configuration and the group (P = 0.004). The synchrony threshold was significantly higher in amblyopes than in controls under the configurations where two pairs of blobs were presented to the amblyopic eye (136.52 ± 50.19 vs. 97.08 ± 22.02 ms, P = 0.027) and where the paired blobs were presented to different eyes (163.15 ± 80.85 vs. 111.61 ± 22.46 ms, P = 0.049). The visual deficits in these two configurations were significantly correlated (r = 0.824, P = 0.012).

Conclusions: The threshold for detecting temporal asynchrony increased when the stimuli were presented only to the amblyopic eye and when they were dichoptically presented to the amblyopic and fellow eyes.
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http://dx.doi.org/10.1167/iovs.19-27893DOI Listing
November 2019

Transplantation with GXHPC1 for Liver Cirrhosis: Phase 1 Trial.

Cell Transplant 2019 Dec 14;28(1_suppl):100S-111S. Epub 2019 Nov 14.

Bioinnovation Center, Tzu Chi foundation; Department of Neurosurgery, Buddhist Tzu Chi General hospital, Tzu Chi University, Hualien.

Currently, the only effective therapy for cirrhosis of the liver is liver transplantation. However, finding a compatible liver is difficult due to the low supply of healthy livers and the ever-increasing demand. However, stem-cell therapy may offer a solution for liver cirrhosis; for example, GXHPC1 therapy preparation contains adipose-derived mesenchymal stem cells (AD-MSCs) and was developed for the treatment of liver cirrhosis. In our previous report, animal studies suggested that treatment of a diseased liver via GXHPC1 transplantation can abrogate liver fibrosis and facilitate recovery of liver function. In our current human trial, patients with liver cirrhosis were included. Their adipose tissue was harvested from the subcutaneous fat of the abdominal wall during surgery. AD-MSCs were cultured and suspended at a concentration of 100 million cells in 1 ml of physiological saline (i.e., GXHPC1). This human study passed the Taiwan Food and Drug Administration IND inspection and received Phase I clinical trial permission. The trial was conducted with six patients with liver cirrhosis to demonstrate the safety and efficacy of administering GXHPC1. Intrahepatic injection of GXHPC1 did not cause any safety issues in the analysis of adverse drug reactions and suspected unexpected serious adverse reactions, and showed a tendency for improvement of liver function, METAVIR score, Child-Pugh score, MELD score, and quality of life for patients with liver cirrhosis.
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http://dx.doi.org/10.1177/0963689719884885DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7016466PMC
December 2019

The effects of the age of onset of strabismus on monocular and binocular visual function in genetically identical twins.

Can J Ophthalmol 2018 12 7;53(6):609-613. Epub 2018 Apr 7.

McGill Vision Research, Department of Ophthalmology, McGill University, Montreal, Que. Electronic address:

Objective: Both genetic and environmental factors are thought to play a role in the pathogenesis of strabismus and subsequent ocular dominance and amblyopia. Our purpose was to compare the characteristics of sensory visual function in 2 adult monozygotic (genetically identical) twins who presented with esotropia at different ages.

Methods: Monocular and binocular visual function was measured in the twins. Contrast sensitivity was used to assess monocular function. Suppressive and stereoscopic measurements were undertaken to assess binocular function. All tests were run using a 2-alternative forced choice psychophysical procedure. Eighteen short tandem repeats (STR) were genotyped across the genome in both twins to determine their exact relationship.

Results: Twin 1 (nondominant eye OD) was diagnosed with esotropia at 6 months of age, whereas twin 2 (nondominant eye OS) was diagnosed with esotropia at 5 years of age. They underwent a similar corrective surgical intervention soon after diagnosis to correct their esodeviations. Monocular contrast sensitivity was poorer for twin 1, particularly at intermediate spatial frequencies. In addition, twin 1 demonstrated complete suppression and unmeasurable stereoscopic function (>300 seconds). On the other hand, twin 2 demonstrated fusion, exhibited only mild suppression, and had near-normal (28 seconds) stereoscopic function. All STR alleles were identical in the twins, proving monozygosity.

Conclusions: Sensory measurements of monocular and binocular visual function in these genetically proven monozygotic twins were significantly different, with the earlier onset of esotropia associated with reduced visual function. Twin 2, whose esotropia was diagnosed at the age of 5 years, had near-normal visual function, both monocularly and binocularly. To the best of our knowledge, this represents the first study of a genetically identical sibling pair with strabismus. By eliminating the genetic differences between these patients, we are able to make powerful observations about the effect of environment on visual function in strabismus.
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http://dx.doi.org/10.1016/j.jcjo.2018.01.032DOI Listing
December 2018

I know that "Kiki" is angular: The metacognition underlying sound-shape correspondences.

Psychon Bull Rev 2019 Feb;26(1):261-268

Department of Experimental Psychology, University of Oxford, Oxford, UK.

We examined the ability of people to evaluate their confidence when making perceptual judgments concerning a classic crossmodal correspondence, the Bouba/Kiki effect: People typically match the "Bouba" sound to more rounded patterns and match the "Kiki" sound to more angular patterns instead. For each visual pattern, individual participants were more confident about their own matching judgments when they happened to fall in line with the consensual response regarding whether the pattern was rated as "Bouba" or "Kiki". Logit regression analyses demonstrated that participants' confidence ratings and matching judgments were predictable by similar regression functions. This implies that the consensus and confidence underlying the Bouba/Kiki effect are underpinned by a common process, whereby perceptual features in the patterns are extracted and then used to match the sound according to rules of crossmodal correspondences. Combining both matching and confidence measures potentially allows one to explore and quantify the strength of associations in human knowledge.
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http://dx.doi.org/10.3758/s13423-018-1516-8DOI Listing
February 2019

Binocular contrast-gain control for natural scenes: Image structure and phase alignment.

Vision Res 2018 05 30;146-147:18-31. Epub 2018 Apr 30.

Department of Psychology, National Cheng Kung University, Tainan, Taiwan.

In the context of natural scenes, we applied the pattern-masking paradigm to investigate how image structure and phase alignment affect contrast-gain control in binocular vision. We measured the discrimination thresholds of bandpass-filtered natural-scene images (targets) under various types of pedestals. Our first experiment had four pedestal types: bandpass-filtered pedestals, unfiltered pedestals, notch-filtered pedestals (which enabled removal of the spatial frequency), and misaligned pedestals (which involved rotation of unfiltered pedestals). Our second experiment featured six types of pedestals: bandpass-filtered, unfiltered, and notch-filtered pedestals, and the corresponding phase-scrambled pedestals. The thresholds were compared for monocular, binocular, and dichoptic viewing configurations. The bandpass-filtered pedestal and unfiltered pedestals showed classic dipper shapes; the dipper shapes of the notch-filtered, misaligned, and phase-scrambled pedestals were weak. We adopted a two-stage binocular contrast-gain control model to describe our results. We deduced that the phase-alignment information influenced the contrast-gain control mechanism before the binocular summation stage and that the phase-alignment information and structural misalignment information caused relatively strong divisive inhibition in the monocular and interocular suppression stages. When the pedestals were phase-scrambled, the elimination of the interocular suppression processing was the most convincing explanation of the results. Thus, our results indicated that both phase-alignment information and similar image structures cause strong interocular suppression.
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http://dx.doi.org/10.1016/j.visres.2018.02.012DOI Listing
May 2018

Symmetry and its role in the crossmodal correspondence between shape and taste.

Atten Percept Psychophys 2018 Apr;80(3):738-751

Crossmodal Research Laboratory, Department of Experimental Psychology, University of Oxford, Oxford, UK.

Despite the rapid growth of research on the crossmodal correspondence between visually presented shapes and basic tastes (e.g., sweet, sour, bitter, and salty), most studies that have been published to date have focused on shape contour (roundness/angularity). Meanwhile, other important features, such as symmetry, as well as the underlying mechanisms of the shape-taste correspondence, have rarely been studied. Over two experiments, we systematically manipulated the symmetry and contours of shapes and measured the influences of these variables on shape-taste correspondences. Furthermore, we investigated a potential underlying mechanism, based on the common affective appraisal of stimuli in different sensory modalities. We replicated the results of previous studies showing that round shapes are associated with sweet taste, whereas angular shapes are associated with sour and bitter tastes. In addition, we demonstrated a novel effect that the symmetry group of a shape influences how it is associated with taste. A significant relationship was observed between the taste and appraisal scores of the shapes, suggesting that the affective factors of pleasantness and threat underlie the shape-taste correspondence. These results were consistent across cultures, when we compared participants from Taiwanese and Western (UK, US, Canada) cultures. Our findings highlight that perceived pleasantness and threat are culturally common factors involved in at least some crossmodal correspondences.
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http://dx.doi.org/10.3758/s13414-017-1463-xDOI Listing
April 2018

Contrast Gain Control in Plaid Pattern Detection.

PLoS One 2016 20;11(10):e0164171. Epub 2016 Oct 20.

Department of Psychology, National Taiwan University, Taipei, Taiwan.

A plaid is a combination of two gratings whose orientations are orthogonal to each other with the same or similar contrasts. We used plaid patterns as stimuli to investigate the mechanisms underlying the detection of a plaid to understand how the visual system combines information from orientation-selective channels. We used a masking paradigm in which an observer was required to detect a target (either a spiral or a plaid) superimposed on a pedestal. We measured the target threshold versus pedestal contrast (TvC) functions at 7 pedestal contrasts for various target-pedestal combinations with a temporal 2AFC paradigm and a staircase procedure. All TvC functions, except the one with an orthogonal spiral pedestal, showed a dipper shape, although the position of the dip and the slope varied across conditions. The result can be explained by a multiple-mechanism divisive inhibition model, which contains several orientation-selective mechanisms. The response of each mechanism is the excitation of a linear filter divided by a broadband inhibitory input. The threshold is determined by a nonlinear combination of the responses of those mechanisms. Alternative models with mechanism(s) specific for plaid did not provide a better description of the data. Thus, a plaid pattern is mediated by a combination of orientation-selective mechanisms. An early plaid-specific mechanism is not necessary for plaid detection.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0164171PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5072603PMC
June 2017

When "Bouba" equals "Kiki": Cultural commonalities and cultural differences in sound-shape correspondences.

Sci Rep 2016 05 27;6:26681. Epub 2016 May 27.

Department of Experimental Psychology, Oxford University, Oxford, UK.

It has been suggested that the Bouba/Kiki effect, in which meaningless speech sounds are systematically mapped onto rounded or angular shapes, reflects a universal crossmodal correspondence between audition and vision. Here, radial frequency (RF) patterns were adapted in order to compare the Bouba/Kiki effect in Eastern and Western participants demonstrating different perceptual styles. Three attributes of the RF patterns were manipulated: The frequency, amplitude, and spikiness of the sinusoidal modulations along the circumference of a circle. By testing participants in the US and Taiwan, both cultural commonalities and differences in sound-shape correspondence were revealed. RF patterns were more likely to be matched with "Kiki" than with "Bouba" when the frequency, amplitude, and spikiness increased. The responses from both groups of participants had a similar weighting on frequency; nevertheless, the North Americans had a higher weighting on amplitude, but a lower weighting on spikiness, than their Taiwanese counterparts. These novel results regarding cultural differences suggest that the Bouba/Kiki effect is partly tuned by differing perceptual experience. In addition, using the RF patterns in the Bouba/Kiki effect provides a "mid-level" linkage between visual and auditory processing, and a future understanding of sound-shape correspondences based on the mechanism of visual pattern processing.
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http://dx.doi.org/10.1038/srep26681DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4882484PMC
May 2016

Therapeutic Effect of Ligustilide-Stimulated Adipose-Derived Stem Cells in a Mouse Thromboembolic Stroke Model.

Cell Transplant 2016 18;25(5):899-912. Epub 2016 Jan 18.

Center for Neuropsychiatry, China Medical University Hospital, Taichung, Taiwan, China.

Stroke is a result of cerebral ischemia that triggers a cascade of both physiological and biochemical events. No effective treatment is available for stroke; however, stem cells have the potential to rescue tissue from the effects of stroke. Adipose-derived stem cells (ADSCs) are an abundant source of adult stem cells; therefore, ADSC therapy can be considered as a future strategy for regenerative medicine. However, more research is required to improve the effectiveness of transplanted ADSCs as a treatment for stroke in the mouse stroke model. Ligustilide, isolated from the herb Angelica sinensis, exhibits a protective effect on neurons and inhibits inflammation. We also demonstrated that ligustilide treatment increases the expression levels of homing factors such as SDF-1 and CXCR4. In the present study, we evaluated the therapeutic effects of ADSC transplantation and ligustilide treatment in a mouse thromboembolic stroke model by behavioral tests, including beam walking, locomotor activity, and rotarod analysis. ADSCs pretreated with ligustilide were transplanted into the brains of stroke mice. The results showed that the therapeutic effect of ADSCs pretreated with ligustilide was better than that of ADSCs without ligustilide pretreatment. There was no difference between the recovery of mice treated by ADSC transplantation combined with subcutaneous ligustilide injection and that of mice treated only with ADSCs. The TUNEL assay showed fewer apoptotic cells in the brains of mice transplanted with ADSCs pretreated with ligustilide as well as in those without pretreatment. In summary, pretreatment of ADSCs with ligustilide improves the therapeutic efficacy of ADSC transplantation. The results of this study will help improve stem cell therapies being developed for future clinical applications.
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http://dx.doi.org/10.3727/096368916X690539DOI Listing
March 2017

A proposed novel stem cell therapy protocol for liver cirrhosis.

Cell Transplant 2015 9;24(3):533-40. Epub 2015 Feb 9.

Department of Stem Cell Applied Technology, Gwo Xi Stem Cell Applied Technology, Hsinchu, Taiwan.

Currently, there is not an effective therapy for cirrhosis of the liver except for liver transplant. However, finding a compatible liver is difficult due to the low supply and increased demand for healthy livers. Stem cell therapy may be a solution for liver cirrhosis. In our previous report, stem cells from Wharton's jelly and bone marrow were shown to improve liver function in a chemically induced liver fibrosis animal model. However, the immunological rejection of an allograft is always a risk for clinical application. In this study proposal, we suggest using human adipose-derived stem cells (ADSCs) because they are an immune-privileged cell type; they lack human leukocyte antigen-DR expression, and they also suppress the proliferation of activated allogenic lymphocytes and inhibit the production of inflammatory cytokines. In addition, ADSCs contain a sufficient amount of adult stem cells for autologous transplantation. Based on these benefits, ADSCs are promising candidates for clinical application when compared to other stem cell types. The aim of our study will be to investigate the safety and efficacy of autologous ADSCs for the clinical treatment of liver cirrhosis.
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http://dx.doi.org/10.3727/096368915X687228DOI Listing
December 2015

A comparison of pedestal effects in first- and second-order patterns.

J Vis 2014 Jan 10;14(1). Epub 2014 Jan 10.

Department of Psychology, National Taiwan University, Taipei, Taiwan.

The human visual system is sensitive to both luminance (first-order) and contrast (second-order) modulations in an image. A linear-nonlinear-linear model is commonly used to explain visual processing of second-order patterns. Here we used a pattern-masking paradigm to compare first-order and second-order visual mechanisms and to characterize the nonlinear properties underlying them. The carriers were either a high-frequency horizontal grating (8 c/°) or a binary random dot pattern; they were either added to a vertical low-frequency (2 c/°) sinusoidal grating (first-order stimuli) or multiplied by it (second-order stimuli). The incremental discrimination threshold of the target was measured with pedestals whose spatial properties matched those of the target, with the exception of contrast (in the first-order pedestal) or modulation depth (in the second-order pedestal). The threshold function showed a typical dipper shape for both first- and second-order stimuli. The results for the first-order stimuli with different types of carrier and the second-order stimuli with a grating carrier were well explained by a divisive inhibition model in which the facilitatory input was divided by the sum of broadband inhibitory inputs. The results for the second-order stimuli with a random-dot carrier were explained by a modified divisive inhibition model that operated on modulation depth. Our results suggest that divisive inhibition is required to explain visual discrimination in both first- and second-order patterns. However, the source and nonlinearity of the divisive inhibition may be different for these two types of patterns and carrier.
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http://dx.doi.org/10.1167/14.1.9DOI Listing
January 2014

Interocular suppression in amblyopia for global orientation processing.

J Vis 2013 Apr 22;13(5):19. Epub 2013 Apr 22.

McGill Vision Research, Department of Ophthalmology, McGill University, Montreal, Québec, Canada.

We developed a dichoptic global orientation coherence paradigm to quantify interocular suppression in amblyopia. This task is biased towards ventral processing and allows comparison with two other techniques-global motion processing, which is more dorsally biased, and binocular phase combination, which most likely reflects striate function. We found a similar pattern for the relationship between coherence threshold and interocular contrast curves (thresholds vs. interocular contrast ratios or TvRs) in our new paradigm compared with those of the previous dichoptic global motion coherence paradigm. The effective contrast ratios at balance point (where the signals from the two eyes have equal weighting) in our new paradigm were larger than those of the dichoptic global motion coherence paradigm but less than those of the binocular phase combination paradigm. The measured effective contrast ratios in the three paradigms were also positively correlated with each other, with the two global coherence paradigms having the highest correlation. We concluded that: (a) The dichoptic global orientation coherence paradigm is effective in quantifying interocular suppression in amblyopia; and (b) Interocular suppression, while sharing a common suppression mechanism at the early stage in the pathway (e.g., striate cortex), may have additional extra-striate contributions that affect both dorsal and ventral streams differentially.
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http://dx.doi.org/10.1167/13.5.19DOI Listing
April 2013

Temporal synchrony deficits in amblyopia.

Invest Ophthalmol Vis Sci 2012 Dec 17;53(13):8325-32. Epub 2012 Dec 17.

McGill Vision Research, Department of Ophthalmology, McGill University, Montreal, Canada.

Purpose: Amblyopia is a developmental abnormality of visual cortex characterized by spatial processing deficits. Recently, it has been suggested that temporal processing also is affected. We investigated temporal sensitivity by measuring temporal synchrony sensitivity.

Methods: In Experiment 1, we used a contrast detection task to compare the detection of a flickering 3 Hz Gaussian blob to that of synchrony discrimination for a 180° phase shift. In Experiment 2, we measured synchrony thresholds directly by assessing the minimum degree of asynchrony that allowed subjects to discriminate which of 4 high-contrast Gaussian blobs was flickering asynchronously in time (synchrony thresholds). Three temporal frequencies (1, 2, and 3 Hz) and two element separations (1.25° and 5°) were compared.

Results: In Experiment 1, we found that the amblyopes (mean age 19.90 ± 8.59 years, range 11-48 years) exhibited a synchrony deficit only for the 1.25 degrees element separation in the amblyopic eye. In Experiment 2, we also found that the sensitivity for nonstrabismic (pure anismetropia) amblyopes (mean age 15.70 ± 4.00 years, range 12-23 years) was reduced for all three temporal frequencies, whereas for strabismic (strabismus and anisometropia) amblyopes (mean age 24.10 ± 10.03 years, range 11-48 years) it was reduced at 3 Hz only, possibly suggesting a different extent of impairment in temporal synchrony for different types of amblyopia.

Conclusions: Our results suggest that amblyopes have a foveal low-level temporal processing deficit that could explain the previously reported deficit for figure-ground discrimination.
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http://dx.doi.org/10.1167/iovs.12-10835DOI Listing
December 2012

Interocular suppression in normal and amblyopic vision: spatio-temporal properties.

J Vis 2012 Oct 31;12(11). Epub 2012 Oct 31.

Department of Psychology, National Cheng Kung University, Tainan, Taiwan.

We measured the properties of interocular suppression in strabismic amblyopes and compared these to dichoptic masking in binocularly normal observers. We used a dichoptic version of the well-established probed-sinewave paradigm that measured sensitivity to a brief target stimulus (one of four letters to be discriminated) in the amblyopic eye at different times relative to a suppression-inducing mask in the fixing eye. This was done using both sinusoidal steady state and transient approaches. The suppression-inducing masks were either modulations of luminance or contrast (full field, just overlaying the target, or just surrounding the target). Our results were interpreted using a descriptive model that included contrast gain control and spatio-temporal filtering prior to excitatory binocular combination. The suppression we measured, other than in magnitude, was not fundamentally different from normal dichoptic masking: lowpass spatio-temporal properties with similar contributions from both surround and overlay suppression.
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http://dx.doi.org/10.1167/12.11.29DOI Listing
October 2012

Orientation coherence sensitivity.

J Vis 2012 Jun 12;12(6):18. Epub 2012 Jun 12.

McGill Vision Research, Department of Ophthalmology, McGill University, Montreal, Quebec, Canada.

We developed a global orientation coherence task for the assessment of global form processing along similar lines to the global motion coherence task. The task involved judgments of global orientation for an array of limited duration 1-D Gabors, some of which were signal (signal orientation) and some of which were noise (random orientation). We address two issues. First: Do motion and form global processing have similar dependencies? And second: Can global sensitivity be explained solely in terms of integrative function? While most dependencies (e.g., contrast, spatial scale, and field size) are similar for form and motion processing, there is a greater dependence on eccentricity for form processing. Sensitivity for global tasks involves more than just integration by filters broadly tuned for orientation. Results are best modeled by filters with narrowband orientation tuning that effectively segregate as well as integrate global information.
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http://dx.doi.org/10.1167/12.6.18DOI Listing
June 2012

Food supplement 20070721-GX may increase CD34+ stem cells and telomerase activity.

J Biomed Biotechnol 2012 22;2012:498051. Epub 2012 Apr 22.

Center for Neuropsychiatry and Department of Neurosurgery, China Medical University Hospital, Taichung, Taiwan.

Few rejuvenation and antiaging markers are used to evaluate food supplements. We measured three markers in peripheral blood to evaluate the antiaging effects of a food supplement containing placental extract. Samples were evaluated for CD34(+) cells, insulin-like growth factor 1 (IGF1), and telomerase activity, which are all markers related to aging. To control the quality of this food supplement, five active components were monitored. In total, we examined 44 individuals who took the food supplement from 1.2 months to 23 months; the average number of CD34(+) cells was almost 6-fold higher in the experimental group compared with the control group. Food supplement intake did not change serum IGF1 levels significantly. Finally, the average telomerase activity was 30% higher in the subjects taking this food supplement. In summary, our results suggest that the placental extract in the food supplement might contribute to rejuvenation and antiaging.
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http://dx.doi.org/10.1155/2012/498051DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3346997PMC
October 2012

Collinear facilitation over space and depth.

J Vis 2012 Feb 21;12(2). Epub 2012 Feb 21.

Department of Psychology, National Taiwan University, Taipei, Taiwan.

The detection threshold of a Gabor target can be reduced by the presence of collinear flanking Gabors but is disrupted when the target and the flankers have different disparity. Here, we further investigated whether it is the depth or surface difference between the target and the flanker that causes the abolition of collinear facilitation. The target and the flankers were 1.6 cycle per degree vertical Gabor patches with a separation of three wavelength units between them. There were six viewing conditions: target and flankers were set (A) in the same frontoparallel plane in a collinear configuration, (B) at different disparities but embedded in the same slanted plane, (C) at different disparities in different frontoparallel planes (flankers occupied at the same depth), (D) at different disparities in different frontoparallel planes (flankers occupied at different depth), (E) in the same frontoparallel plane in a noncollinear configuration, and (F) at the same disparity but locally slanted. We measured the target contrast detection threshold with and without the flankers present with a temporal 2AFC paradigm with the Ψ staircase method. Strong collinear facilitation was observed when the target and the flankers were either in the same frontoparallel plane or embedded in the same slanted surface even though the target and the flankers were at different disparities. Our results suggest that it is the difference in surface assignment, not the difference in disparity per se, that causes the disruption of collinear facilitation.
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http://dx.doi.org/10.1167/12.2.20DOI Listing
February 2012

Synchronous sounds enhance visual sensitivity without reducing target uncertainty.

Seeing Perceiving 2011 ;24(6):623-38

Department of Experimental Psychology, University of Oxford, Oxford, OX1 3UD, UK.

We examined the crossmodal effect of the presentation of a simultaneous sound on visual detection and discrimination sensitivity using the equivalent noise paradigm (Dosher and Lu, 1998). In each trial, a tilted Gabor patch was presented in either the first or second of two intervals embedded in dynamic 2D white noise with one of seven possible contrast levels. The results revealed that the sensitivity of participants' visual detection and discrimination performance were both enhanced by the presentation of a simultaneous sound, though only close to the noise level at which participants' target contrast thresholds started to increase with the increasing noise contrast. A further analysis of the psychometric function at this noise level revealed that the increase in sensitivity could not be explained by the reduction of participants' uncertainty regarding the onset time of the visual target. We suggest that this crossmodal facilitatory effect may be accounted for by perceptual enhancement elicited by a simultaneously-presented sound, and that the crossmodal facilitation was easier to observe when the visual system encountered a level of noise that happened to be close to the level of internal noise embedded within the system.
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http://dx.doi.org/10.1163/187847611X603765DOI Listing
March 2012

Pattern masking: the importance of remote spatial frequencies and their phase alignment.

J Vis 2012 Feb 16;12(2):14. Epub 2012 Feb 16.

McGill Vision Research, Department of Ophthalmology, Montreal, Quebec, Canada.

To assess the effects of spatial frequency and phase alignment of mask components in pattern masking, target threshold vs. mask contrast (TvC) functions for a sine-wave grating (S) target were measured for five types of mask: a sine-wave grating (S), a square-wave grating (Q), a missing fundamental square-wave grating (M), harmonic complexes consisting of phase-scrambled harmonics of a square wave (Qp), and harmonic complexes consisting of phase-scrambled harmonics of a missing fundamental square wave (Mp). Target and masks had the same fundamental frequency (0.46 cpd) and the target was added in phase with the fundamental frequency component of the mask. Under monocular viewing conditions, the strength of masking depends on phase relationships among mask spatial frequencies far removed from that of the target, at least 3 times the target frequency, only when there are common target and mask spatial frequencies. Under dichoptic viewing conditions, S and Q masks produced similar masking to each other and the phase-scrambled masks (Qp and Mp) produced less masking. The results suggest that pattern masking is spatial frequency broadband in nature and sensitive to the phase alignments of spatial components.
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http://dx.doi.org/10.1167/12.2.14DOI Listing
February 2012

Butylidenephthalide suppresses human telomerase reverse transcriptase (TERT) in human glioblastomas.

Ann Surg Oncol 2011 Nov 7;18(12):3514-27. Epub 2011 May 7.

Department of Life Science and Graduate Institute of Biotechnology, National Dong Hwa University, Hualien, Taiwan, Republic of China.

Background: Telomerase is widely expressed in most human cancers, but is almost undetectable in normal somatic cells and is therefore a potential drug target. Using the human telomerase promoter platform, the naturally occurring compound butylidenephthalide (BP) was selected for subsequent investigation of antitumor activity in vitro and in vivo.

Methods: We treated human glioblastoma cells with BP and found a dose-dependent decrease in human telomerase reverse transcriptase (hTERT) mRNA expression and a concomitant increase in p16 and p21 expression. Because c-Myc and Sp1 are involved in transcriptional regulation of hTERT, the effect of BP on c-Myc and Sp1 expression was examined.

Results: Using electrophoretic mobility shift assays and western blotting, we showed that BP represses hTERT transcriptional activity via downregulation of Sp1 expression. Using the telomerase repeat amplification protocol, an association between BP concentration and suppression of telomerase activity, induction of human glioblastoma senescence, and inhibition of cellular proliferation was identified. This was supported by a mouse xenograft model, in which BP repressed telomerase and inhibited tumor proliferation, resulting in tumor senescence. Overexpression of hTERT restored telomerase activity in human glioblastoma cells and overcame replicative senescence.

Conclusions: These findings suggest that BP inhibits proliferation and induces senescence in human glioblastomas by downregulating hTERT expression and consequently telomerase activity. This is the first study to describe regulation of telomerase activity by BP in human glioblastomas.
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http://dx.doi.org/10.1245/s10434-011-1644-0DOI Listing
November 2011

The effects of flankers on contrast detection and discrimination in binocular, monocular, and dichoptic presentations.

J Vis 2010 Apr 27;10(4):13.1-15. Epub 2010 Apr 27.

McGill Vision Research Unit, Department of Ophthalmology, McGill University, 687 Pine Avenue West, Montreal, Quebec, Canada.

We investigated how two co-aligned adjacent stimuli (flankers) influence threshold versus pedestal contrast (TvC) functions in binocular, monocular, and dichoptic presentations. Targets were presented to the two eyes or to only one eye. Pedestals and flankers were presented to the same eye to which the target was presented (binocular or monocular presentations) or to the other eye (dichoptic presentation). In the binocular presentation of targets and pedestals, the binocular flankers lowered thresholds at low pedestal contrasts. The monocular flankers had a similar effect to the binocular flanker, although the threshold reduction was smaller. In the dichoptic presentation of a target and a pedestal, flankers lowered thresholds when flankers were presented to the eye where targets were presented. In contrast, dichoptic flankers elevated thresholds at intermediate pedestal contrasts when a pedestal was also dichoptically presented. We fitted binocular contrast gain control models to the data. It follows from the fitting results that flankers modulate outputs from spatial filters in the monocular processing stage of contrast gain control.
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http://dx.doi.org/10.1167/10.4.13DOI Listing
April 2010

Spatial distortions produced by purely dichoptic-based visual motion.

Perception 2009 ;38(7):1012-8

McGill Vision Research, Department of Ophthalmology, McGill University, 687 Pine Avenue West, Montreal, Québec H3A 1A1, Canada.

It is known that local, monocular motion (short-range motion) can produce local distortions of visual space. We wanted to know if local monocular motion was both sufficient and necessary for producing motion-based spatial distortions. We used a previously reported dichoptic motion stimulus in which the directional motion signal is not present in either eye's input but is only present after binocular combination. We show that such a stimulus can also induce perceived changes in spatial position. This suggests that local, monocular motion while being sufficient is not necessary for the production of motion-based illusions. It suggests that one source of motion signals responsible for this illusion is from binocular motion mechanisms.
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http://dx.doi.org/10.1068/p6274DOI Listing
April 2010

Low-level mechanisms may contribute to paradoxical motion percepts.

J Vis 2009 May 13;9(5):9.1-14. Epub 2009 May 13.

Department of Ophthalmology, McGill University, McGill Vision Research, Montreal, Canada.

A recent series of experiments demonstrated a surprising deterioration of visual motion discrimination with increasing stimulus size for stimuli of high contrast. This counterintuitive finding was explained as a result of surround suppression in visual area V5. Equally paradoxical was the finding that older observers showed better performance than younger observers. This second result was explained as an age-related reduction in surround suppression due to changes in GABA-mediated inhibition. Using an opponent motion stimulus, we find an analogous effect and also find that this effect is much reduced in older observers, to the point where they perform better than younger observers. Our long duration stimulus should be beyond the range at which surround-suppressed neurons in V5 are preferentially activated. Having normalized our stimuli relative to contrast threshold, we show that our results can be entirely explained by the relative contrast of the stimulus and speculate that contrast sensitivity may play a role in previously reported results. Our older observers' data similarly can be explained by the relative contrast of the stimulus. The difference between older and younger observers appears to be a result of a weakening of spatial summation at high contrast in younger observers, perhaps caused by earlier saturation of motion mechanisms.
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http://dx.doi.org/10.1167/9.5.9DOI Listing
May 2009

Importance of phase alignment for interocular suppression.

Vision Res 2009 Jul 3;49(14):1838-47. Epub 2009 May 3.

McGill Vision Research Unit, Department of Ophthalmology, McGill University, Montreal, Quebec, Canada.

We measured contrast thresholds for Gabor targets in the presence of maskers which had higher or lower spatial frequencies than the targets. A high-pass fractal masker elevated target contrast thresholds at low and intermediate pedestal contrasts in both monocular and dichoptic modes of presentation, suggesting that the masking occurs after a monocular processing stage. Moreover we found that a high-pass checkerboard masker elevated thresholds at the low and intermediate pedestal contrasts and that most of this threshold elevation disappeared when the phase of the masker's spatial components were scrambled. This masking was effective only in the dichoptic presentation, not in the monocular presentation. These results indicate that phase alignment of the high spatial frequency components plays a crucial role for interocular suppression. We speculate that phase alignments signal the existence of a luminance contour in the monocular image and that this signal suppresses processing of information in the other eye when there is no corresponding signal in that eye.
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http://dx.doi.org/10.1016/j.visres.2009.04.020DOI Listing
July 2009

The dynamics of collinear facilitation: fast but sustained.

Vision Res 2008 Dec 23;48(27):2715-22. Epub 2008 Oct 23.

McGill Vision Research, Department of Ophthalmology, McGill University, Montreal, Quebec, Canada.

The mechanism by which flanking Gabors facilitate the detection of a central test Gabor is not well understood. Since a knowledge of the dynamics of this effect will help constrain the class of possible model, we conducted three different but interrelated experiments designed to assess different aspects of the dynamics associated with this facilitation. In experiment 1, collinear facilitation was measured at different onset times of a test target for flanks whose contrast was sinusoidally-modulated at 1 Hz. In experiment 2, the order between test target and flanks was investigated by varying the SOA, both stimuli being presented for 50 ms. Experiment 3 assessed temporal summation with and without the flanks. The results obtained do not support either a single channel masking explanation which predicts transient dynamics or an explanation-based solely on the conduction of facilitatory impulses from flanks to target via long-range horizontal connections which predicts transient but delayed dynamics. The results suggest that the dynamics of facilitation are fast but sustained. We propose two underlying mechanisms, a rapid signal to initiate facilitation across large retinal distances, based on feedback from higher centers and a sustained facilitative response based on the temporal integration of locally-responsive, lower-level mechanisms.
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http://dx.doi.org/10.1016/j.visres.2008.09.013DOI Listing
December 2008
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