Publications by authors named "Jason C Chan"

32 Publications

Assessment of retinal neurodegeneration with spectral-domain optical coherence tomography: a systematic review and meta-analysis.

Eye (Lond) 2020 Jun 24. Epub 2020 Jun 24.

Department of Ophthalmology and Visual Sciences, The Chinese University of Hong Kong, Hong Kong, SAR, China.

Objectives: To comprehensively assess diabetic retinopathy neurodegeneration (DRN) as quantified by retinal neuronal and axonal layers measured with spectral-domain optical coherence tomography (SD-OCT) in subjects with diabetes mellitus (DM).

Methods: Articles on the topic of examining macular ganglion cell-inner plexiform layer (m-GCIPL), macular retinal nerve fibre layer (m-RNFL), macular ganglion cell complex (m-GCC), and peripapillary RNFL (p-RNFL) measured with SD-OCT in DM subjects without DR (NDR) or with non-proliferative DR (NPDR) were searched in PubMed and Embase up to November 31, 2019. Standardized mean difference (SMD) as effect size were pooled using random-effects model.

Results: Thirty-six studies searched from online databases and the CUHK DM cohort were included in the meta-analysis. In the comparison between NDR and control, macular measures including mean m-GCIPL (SMD = -0.26, p = 0.003), m-RNFL (SMD = -0.26, p = 0.046), and m-GCC (SMD = -0.28; p = 0.009) were significantly thinner in the NDR group. In the comparison between NPDR and NDR, only mean p-RNFL was significantly thinner in the NPDR group (SMD = -0.27; p = 0.03), but not other macular measures.

Conclusions: Thinning of retinal neuronal and axonal layers at macula as measured by SD-OCT are presented in eyes with NDR, supporting DRN may be the early pathogenesis in the DM patients without the presence of clinical signs of DR. In the future, these SD-OCT measures may be used as surrogates of DRN to stratify DM patients with a high risk of DR, and may be used as a therapeutic target if neuroprotection treatment for DR is available.
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http://dx.doi.org/10.1038/s41433-020-1020-zDOI Listing
June 2020

Ophthalmology in the time of COVID-19: experience from Hong Kong Eye Hospital.

Int J Ophthalmol 2020 18;13(6):851-859. Epub 2020 Jun 18.

Department of Ophthalmology and Visual Sciences, the Chinese University of Hong Kong, Hong Kong SAR, China.

Aim: To review international guidelines and to share our infection control experience during the coronavirus disease 2019 (COVID-19) pandemic at a tertiary eye centre in Hong Kong.

Methods: Infection control guidelines and recommendations from international ophthalmological bodies are reviewed and discussed. The measures at our hospital were drawn up as per international and local health authorities' guidelines and implemented with the collaboration of doctors, nurses and administrative staff.

Results: The aims of our infection control measures are to 1) minimize cross-infection within the hospital; 2) protect and support hospital staff; 3) ensure environmental control. To minimize the risk of cross-infection, outpatient attendance and elective surgery have been reduced by 40%, and general anesthesia procedures were reduced by 90%. Patients entering the hospital are screened for fever, travel history, contact and cluster history, and COVID-19 related symptoms. To protect and support hospital staff, we ensure provision of adequate personal protective equipment (PPE) and provide clear guidelines on the level of PPE needed, depending on the clinical situation. Other protective measures include provision of work uniforms, easy access to alcohol-based hand rub, opening new lunch areas, implementation of self-monitoring and self-reporting systems, and communication online education and updates. Finally, environmental control is achieved by ensuring regular disinfection of the hospital premise, enhancing ventilation, and usage of disposable ophthalmic instruments.

Conclusion: Our multi-pronged approach to infection control is, so far, successful in minimizing infection risks, while allowing the maintenance of essential ophthalmic services.
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http://dx.doi.org/10.18240/ijo.2020.06.01DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7270264PMC
June 2020

Transient corneal ectasia after phacoemulsification in an eye with femtosecond intrastromal presbyopic treatment.

J Cataract Refract Surg 2020 01;46(1):143-146

From the Department of Ophthalmology, Hong Kong Sanatorium & Hospital (T.C.Y. Chan, Chang); Department of Ophthalmology and Visual Sciences, The Chinese University of Hong Kong (T.C.Y. Chan, J.C.K. Chan, Lam, Chang); and Hong Kong Eye Hospital (C.K. Chan, Lam), Hong Kong, China.

We report a case of transient corneal ectasia developed after phacoemulsification in an eye previously treated with INTRACOR. There was a myopic refractive surprise after cataract surgery. Corneal tomography showed an increase in keratometry and elevation profile compared with preoperative examination. Soft contact lenses and intraocular pressure-lowering medications were prescribed as interim treatment. Clinical improvement was seen gradually, and the resolution of myopia and ectasia was achieved at 3 months. We believe that high intraocular pressure during phacoemulsification and the weakening effect of femtosecond intrastromal presbyopic treatment can be the culprits.
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http://dx.doi.org/10.1016/j.jcrs.2019.08.050DOI Listing
January 2020

Clinically relevant factors associated with quantitative optical coherence tomography angiography metrics in deep capillary plexus in patients with diabetes.

Eye Vis (Lond) 2020 3;7. Epub 2020 Feb 3.

1Department of Ophthalmology and Visual Sciences, The Chinese University of Hong Kong, Hong Kong Special Administrative Region, Kowloon, China.

Background: To test clinically relevant factors associated with quantitative artifact-free deep capillary plexus (DCP) metrics in patients with diabetes mellitus (DM).

Methods: 563 eligible eyes (221 with no diabetic retinopathy [DR], 135 with mild DR, 130 with moderate DR, and 77 with severe DR) from 334 subjects underwent optical coherence tomography-angiography (OCT-A) with a swept-source OCT (Triton DRI-OCT, Topcon, Inc., Tokyo, Japan). Strict criteria were applied to exclude from analysis those DCP images with artifacts and of poor quality, including projection artifacts, motion artifacts, blurriness, signal loss, B-scan segmentation error, or low-quality score. A customized MATLAB program was then used to quantify DCP morphology from the artifact-free DCP images by calculating three metrics: foveal avascular zone (FAZ), vessel density (VD), and fractal dimension (FD).

Results: 166 (29.5%) eyes were excluded after quality control, leaving in the analysis 397 eyes (170 with no DR, 101 with mild DR, 90 with moderate DR, 36 with severe DR) from 250 subjects. In the multiple regression models, larger FAZ area was associated with more severe DR (β = 0.687;  = 0.037), shorter axial length (AL) (β = - 0.171;  = 0.003), thinner subfoveal choroid thickness (β = - 0.122;  = 0.031), and lower body mass index (BMI) (β = - 0.090;  = 0.047). Lower VD was associated with more severe DR (β = - 0.842;  = 0.001), shorter AL (β = 0.107;  = 0.039), and poorer visual acuity (VA) (β = - 0.133;  = 0.021). Lower FD was associated with more severe DR (β = - 0.891;  < 0.001) and with older age (β = - 0.142;  = 0.004).

Conclusions: Quantitative artifact-free DCP metrics are associated with VA, DR severity, AL, subfoveal choroidal thickness, age, and BMI in diabetic patients. The effects of ocular and systemic factors should be considered for meaningful interpretations of DCP changes in DM patients.
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http://dx.doi.org/10.1186/s40662-019-0173-yDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6996172PMC
February 2020

OCT Angiography Metrics Predict Progression of Diabetic Retinopathy and Development of Diabetic Macular Edema: A Prospective Study.

Ophthalmology 2019 12 26;126(12):1675-1684. Epub 2019 Jun 26.

Department of Ophthalmology and Visual Sciences, The Chinese University of Hong Kong, Hong Kong Special Administrative Region, China. Electronic address:

Purpose: To prospectively determine the relationship of OCT angiography (OCTA) metrics to diabetic retinopathy (DR) progression and development of diabetic macular edema (DME).

Design: Prospective, observational study.

Participants: A total of 205 eyes from 129 patients with diabetes mellitus followed up for at least 2 years.

Methods: All participants underwent OCTA with a swept-source OCT device (DRI-OCT Triton, Topcon, Inc, Tokyo, Japan). Individual OCTA images of superficial capillary plexus (SCP) and deep capillary plexus (DCP) were generated by IMAGEnet6 (Basic License 10). After a quality check, automated measurements of foveal avascular zone (FAZ) area, FAZ circularity, vessel density (VD), and fractal dimension (FD) of both SCP and DCP were then obtained.

Main Outcome Measures: Progression of DR and development of DME.

Results: Over a median follow-up of 27.14 months (interquartile range, 24.16-30.41 months), 28 of the 205 eyes (13.66%) developed DR progression. Of the 194 eyes without DME at baseline, 17 (8.76%) developed DME. Larger FAZ area (hazard ratio [HR], 1.829 per SD increase; 95% confidence interval [CI], 1.332-2.512), lower VD (HR, 1.908 per SD decrease; 95% CI, 1.303-2.793), and lower FD (HR, 4.464 per SD decrease; 95% CI, 1.337-14.903) of DCP were significantly associated with DR progression after adjusting for established risk factors (DR severity, glycated hemoglobin, duration of diabetes, age, and mean arterial blood pressure at baseline). Lower VD of SCP (HR, 1.789 per SD decrease; 95% CI, 1.027-4.512) was associated with DME development. Compared with the model with established risk factors alone, the addition of OCTA metrics improved the predictive discrimination of DR progression (FAZ area of DCP, C-statistics 0.723 vs. 0.677, P < 0.001; VD of DCP, C-statistics 0.727 vs. 0.677, P = 0.001; FD of DCP, C-statistics 0.738 vs. 0.677, P < 0.001) and DME development (VD of SCP, C-statistics 0.904 vs. 0.875, P = 0.036).

Conclusions: The FAZ area, VD, and FD of DCP predict DR progression, whereas VD of SCP predicts DME development. Our findings provide evidence to support that OCTA metrics improve the evaluation of risk of DR progression and DME development beyond traditional risk factors.
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http://dx.doi.org/10.1016/j.ophtha.2019.06.016DOI Listing
December 2019

Telling a good story: The effects of memory retrieval and context processing on eyewitness suggestibility.

PLoS One 2019 21;14(2):e0212592. Epub 2019 Feb 21.

Department Psychology, Iowa State University, Ames, Iowa, United States of America.

Witnesses are likely to describe a crime many times before testifying or encountering misinformation about that crime. Research examining the effect of retrieval on later suggestibility has yielded mixed results. LaPaglia and Chan manipulated whether misinformation was presented in a narrative or misleading questions, and they found that retrieval increased suggestibility when misinformation was presented in a narrative, but reduced suggestibility when the same misinformation was presented in questions. In the current study, we aimed to address why these differences occurred. Specifically, we examined whether contextual detail and narrative coherence during misinformation exposure influenced the relation between retrieval and suggestibility. Participants watched a robbery video and some were questioned about the event afterwards. They were then exposed to misinformation presented in a narrative (Experiment 1) or questions (Experiment 2) before taking a final memory test. Testing enhanced suggestibility when the misinformation phase reinstated contextual information of the event, but not when the misinformation phase included few contextual details-regardless of whether the misinformation was in a narrative or questions. In Experiment 3, disrupting narrative coherence by randomizing the order of contextual information eliminated retrieval-enhanced suggestibility. Therefore, context processing during the post-event information phase influences whether retrieval enhances or reduces eyewitness suggestibility.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0212592PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6383884PMC
November 2019

Do masked-face lineups facilitate eyewitness identification of a masked individual?

J Exp Psychol Appl 2019 Sep 17;25(3):396-409. Epub 2018 Dec 17.

Department of Psychology.

Perpetrators often wear disguises like ski masks to hinder subsequent identification by witnesses or law enforcement officials. In criminal cases involving a masked perpetrator, the decision of whether and how to administer a lineup often rests on the investigating officer. To date, no evidence-based recommendations are available for eyewitness identifications of a masked perpetrator. In 4 experiments, we examined lineup identification performance depending on variations in both encoding (studying a full face vs. a partial/masked face) and retrieval conditions (identifying a target from a full-face lineup vs. a partial/masked-face lineup). In addition, we manipulated whether the target was present or absent in the lineup in Experiments 3 and 4. Across all experiments, when participants had encoded a masked face, the masked-face lineup increased identification accuracy relative to the full-face lineup. These data provide preliminary evidence that matching lineup construction to how witnesses originally encoded the perpetrator may enhance the accuracy of eyewitness identifications. (PsycINFO Database Record (c) 2019 APA, all rights reserved).
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http://dx.doi.org/10.1037/xap0000195DOI Listing
September 2019

Retrieval potentiates new learning: A theoretical and meta-analytic review.

Psychol Bull 2018 11 27;144(11):1111-1146. Epub 2018 Sep 27.

Department of Psychology.

A growing body of research has shown that retrieval can enhance future learning of new materials. In the present report, we provide a comprehensive review of the literature on this finding, which we term test-potentiated new learning. Our primary objectives were to (a) produce an integrative review of the existing theoretical explanations, (b) summarize the extant empirical data with a meta-analysis, (c) evaluate the existing accounts with the meta-analytic results, and (d) highlight areas that deserve further investigations. Here, we identified four nonexclusive classes of theoretical accounts, including resource accounts, metacognitive accounts, context accounts, and integration accounts. Our quantitative review of the literature showed that testing reliably potentiates the future learning of new materials by increasing correct recall or by reducing erroneous intrusions, and several factors have a powerful impact on whether testing potentiates or impairs new learning. Results of a metaregression analysis provide considerable support for the integration account. Lastly, we discuss areas of under-investigation and possible directions for future research. (PsycINFO Database Record (c) 2018 APA, all rights reserved).
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http://dx.doi.org/10.1037/bul0000166DOI Listing
November 2018

Survival Analysis of Corneal Densitometry After Collagen Cross-Linking for Progressive Keratoconus.

Cornea 2018 Nov;37(11):1449-1456

Cornea Service, Wills Eye Hospital, Sidney Kimmel Medical College at Thomas Jefferson University, Philadelphia, PA.

Purpose: To evaluate the history of densitometric data in patients with keratoconus undergoing corneal cross-linking.

Methods: Twenty-two eyes of 22 patients with keratoconus were included. Corneal tomography and densitometry measurements were performed before and after accelerated corneal cross-linking. The duration of corneal haze was defined as the time between cross-linking and densitometry measurements returning to the preoperative value. Survival analysis of corneal haze after cross-linking was performed. Preoperative and postoperative corneal densitometry, maximum keratometry (Kmax), and central corneal thickness were compared.

Results: The duration of corneal haze was 18.2 ± 3.8 months at the first zone of 0 to 2 mm and 10.9 ± 2.5 months at the second zone of 2 to 6 mm. There was no change in Kmax between the preoperative period and the time at which corneal haze resolved (P = 0.394 at the first zone; P = 0.658 at the second zone). Compared with the measurement taken at resolution of corneal haze, Kmax at 1 year after haze resolution was lower (62.0 ± 9.9 D to 61.2 ± 9.9 D, P = 0.008 at the first zone; 63.6 ± 10.9 D to 62.5 ± 10.1 D, P = 0.016 at the second zone). There was a decrease of central corneal thickness between the preoperative period and the time at which corneal haze resolved (470.8 ± 34.1 μm to 464.8 ± 34.5 μm, P = 0.047 at the first zone; 465.0 ± 35.3 μm to 454.7 ± 37.2 μm, P = 0.001 at the second zone), but it remained unchanged after haze resolution (P = 0.146 at the first zone; P = 0.067 at the second zone).

Conclusions: Corneal cross-linking halted keratoconus progression when detectable haze was present. There was continuous corneal flattening measured at 1 year after haze resolution. Thinning of the cornea was seen only when haze was detectable after cross-linking.
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http://dx.doi.org/10.1097/ICO.0000000000001686DOI Listing
November 2018

Beyond communication: Episodic memory is key to the self in time.

Behav Brain Sci 2018 01;41:e33

Department of Psychology,Iowa State University,Ames,IA

Mahr & Csibra (M&C) propose that episodic memory evolved to support epistemic authority in social communication. We argue for a more parsimonious interpretation whereby episodic memory subserves a broader preparatory function for both social and non-social behavior. We conclude by highlighting that functional accounts of episodic memory may need to consider the complex interrelations between self and subjective time.
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http://dx.doi.org/10.1017/S0140525X17001522DOI Listing
January 2018

Corneal backward scattering and higher-order aberrations in children with vernal keratoconjunctivitis and normal topography.

Acta Ophthalmol 2018 May 1;96(3):e327-e333. Epub 2017 Nov 1.

Department of Ophthalmology & Visual Sciences, The Chinese University of Hong Kong, Hong Kong, China.

Purpose: To investigate the corneal backward scattering and higher-order aberrations (HOAs) in children with vernal keratoconjunctivitis (VKC) and normal topography.

Methods: Thirty-six eyes of 22 patients with VKC and 54 eyes of 34 normal subjects were included. All participants had clear cornea, absence of dry eyes and a normal corneal tomography. Scheimpflug imaging was used to measure corneal backward scattering in zones centred on the corneal apex (central 2-mm zone and paracentral 2- to 6-mm zone), and HOAs were compared between VKC and normal control.

Results: The mean age of participants was 12.0 ± 4.1 years in VKC group and 11.2 ± 4.1 years in control group (p = 0.339). There was no significant intergroup difference in mean keratometry, astigmatism and apex pachymetry (p ≥ 0.076). Total corneal backscatter was higher in the VKC group compared to the control group (p ≤ 0.012). Anterior and posterior cornea displayed a higher level of backward scattering in the VKC group (p < 0.001 for anterior; p ≤ 0.048 for posterior). Patients with VKC exhibited higher total HOAs and coma (p ≤ 0.036). There were significant correlations between total anterior HOAs and backward scattering measured at the central (r = 0.500; p = 0.032) and paracentral zones (r = 0.470; p = 0.024) for VKC.

Conclusion: The current study showed optical quality changes in patients with clear corneas and quiescent VKC. An increase in corneal backward scattering and HOAs was noted in patients with VKC as compared to normal patients.
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http://dx.doi.org/10.1111/aos.13566DOI Listing
May 2018

Epithelium-on corneal collagen crosslinking for management of advanced keratoconus.

J Cataract Refract Surg 2016 05;42(5):738-49

From the Department of Ophthalmology (Chen, Zhang, Ding, Li, Wang), Affiliated Eye Hospital of Wenzhou Medical College, Wenzhou, Zhejiang, the Department of Ophthalmology and Visual Sciences (T.C.Y. Chan, Jhanji), Chinese University of Hong Kong, and Hong Kong Eye Hospital (T.C.Y. Chan, J.C.K. Chan, Jhanji), Mongkok, Kowloon, and the Department of Mathematics and Statistics (Yu), Hang Seng Management College, Hong Kong, China.

Purpose: To report the 1-year visual and keratometric results of epithelium-on corneal collagen crosslinking (CXL) for advanced keratoconus (median maximum keratometry [K] ≥58.0 diopters [D]).

Setting: School of Ophthalmology and Optometry and Eye Hospital of Wenzhou Medical College, Wenzhou, China.

Design: Prospective case series.

Methods: Patients with bilateral progressive keratoconus had tetracaine-enhanced epithelium-on CXL. The worse eye had CXL, and the fellow eye was not treated. Results were reported 1, 3, 6, and 12 months postoperatively. The outcomes were compared with those in the fellow untreated eyes.

Results: Twenty-one eyes of 21 patients with a median age of 20.4 years (interquartile range [IQR], 9.5 years) were treated. A significant improvement in postoperative uncorrected distance visual acuity was observed at 12 months (P = .002). Postoperative corrected distance visual acuity improved at 6 months and 12 months (P ≤ .009) compared with baseline values. The maximum K decreased by 1.63 D from the median preoperative maximum K of 62.7 D (IQR, 12.9 D) at 12 months (P < .001). The reduction in maximum K was higher after CXL than in untreated eyes at the end of 12 months (P = .001). Correlation analysis between the preoperative maximum K values and the change over 6 to 12 months between different studies showed a significant correlation (r = -0.764, P < .001; Spearman correlation).

Conclusions: Epithelium-on CXL was an effective treatment for patients with advanced keratoconus. A higher preoperative maximum K value correlated with greater corneal flattening after CXL.

Financial Disclosure: None of the authors has a financial or proprietary interest in any material or method mentioned.
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http://dx.doi.org/10.1016/j.jcrs.2016.02.041DOI Listing
May 2016

Studying on borrowed time: How does testing impair new learning?

J Exp Psychol Learn Mem Cogn 2015 Nov 4;41(6):1741-54. Epub 2015 May 4.

Department of Psychology.

Retrieving studied materials often enhances subsequent learning of new materials (Pastötter & Bäuml, 2014). However, retrieval has also been shown to impair new learning (Finn & Roediger, 2013). In this article, we attempted to determine when retrieval enhances and when it impairs new learning. We argue that testing impairs new learning when one intermixes testing with new learning, which biases participants to relearn the tested information at the expense of the new information. We refer to this as the borrowed time hypothesis. Consistent with this idea, we reduced or eliminated test-impaired new learning by discouraging time borrowing. Moreover, testing enhanced new learning only when the test trials and new learning trials were presented in separate blocks. These results suggest that test-impaired new learning and test-enhanced new learning are based on different underlying mechanisms and that they are not simply the flipped side of the same coin.
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http://dx.doi.org/10.1037/xlm0000126DOI Listing
November 2015

Retrieval induces forgetting, but only when nontested items compete for retrieval: Implication for interference, inhibition, and context reinstatement.

J Exp Psychol Learn Mem Cogn 2015 Sep 26;41(5):1298-315. Epub 2015 Jan 26.

Department of Psychology, Iowa State University.

The mechanism responsible for retrieval-induced forgetting has been the subject of rigorous theoretical debate, with some researchers postulating that retrieval-induced forgetting can be explained by interference (J. G .W. Raaijmakers & E. Jakab, 2013) or context reinstatement (T. R. Jonker, P. Seli, & C. M. MacLeod, 2013), whereas others claim that retrieval-induced forgetting is better explained by inhibition (M. C. Anderson, 2003). A fundamental assumption of the inhibition account is that nonpracticed items are suppressed because they compete for retrieval during initial testing. In the current study, we manipulated competition in a novel interpolated testing paradigm by having subjects learn the nonpracticed items either before (high-competition condition) or after (low-competition condition) they practiced retrieval of the target items. We found retrieval-induced forgetting for the nonpracticed competitors only when they were studied before retrieval practice. This result provides support for a critical assumption of the inhibition account.
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http://dx.doi.org/10.1037/xlm0000101DOI Listing
September 2015

Testing increases suggestibility for narrative-based misinformation but reduces suggestibility for question-based misinformation.

Behav Sci Law 2013 Sep-Oct;31(5):593-606. Epub 2013 Sep 16.

Department of Psychology, Morningside College, 1501 Morningside Ave, Sioux City, IA, 51106, U.S.A.

A number of recent studies have found that recalling details of an event following its occurrence can increase people's suggestibility to later presented misinformation. However, several other studies have reported the opposite result, whereby earlier retrieval can reduce subsequent eyewitness suggestibility. In the present study, we investigated whether differences in the way misinformation is presented can modulate the effects of testing on suggestibility. Participants watched a video of a robbery and some were questioned about the event immediately afterwards. Later, participants were exposed to misinformation in a narrative (Experiment 1) or in questions (Experiment 2). Consistent with previous studies, we found that testing increased suggestibility when misinformation was presented via a narrative. Remarkably, when misinformation was presented in questions, testing decreased suggestibility.
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http://dx.doi.org/10.1002/bsl.2090DOI Listing
May 2014

Retrieval enhances eyewitness suggestibility to misinformation in free and cued recall.

J Exp Psychol Appl 2014 Mar 2;20(1):81-93. Epub 2013 Sep 2.

Department of Psychology, Iowa State University.

Immediately recalling a witnessed event can increase people's susceptibility to later postevent misinformation. But this retrieval-enhanced suggestibility (RES) effect has been shown only when the initial recall test included specific questions that reappeared on the final test. Moreover, it is unclear whether this phenomenon is affected by the centrality of event details. These limitations make it difficult to generalize RES to criminal investigations, which often begin with free recall prior to more specific queries from legal officials and attorneys. In 3 experiments, we examined the influence of test formats (free recall vs. cued recall) and centrality of event details (central vs. peripheral) on RES. In Experiment 1, both the initial and final tests were cued recall. In Experiment 2, the initial test was free recall and the final test was cued recall. In Experiment 3, both the initial and final tests were free recall. Initial testing increased misinformation reporting on the final test for peripheral details in all experiments, but the effect was significant for central details only after aggregating the data from all 3 experiments. These results show that initial free recall can produce RES, and more broadly, that free recall can potentiate subsequent learning of complex prose materials.
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http://dx.doi.org/10.1037/xap0000001DOI Listing
March 2014

Impairing existing declarative memory in humans by disrupting reconsolidation.

Proc Natl Acad Sci U S A 2013 Jun 20;110(23):9309-13. Epub 2013 May 20.

Department of Psychology and Neuroscience Interdisciplinary Program, Iowa State University, Ames, IA 50014, USA.

During the past decade, a large body of research has shown that memory traces can become labile upon retrieval and must be restabilized. Critically, interrupting this reconsolidation process can abolish a previously stable memory. Although a large number of studies have demonstrated this reconsolidation associated amnesia in nonhuman animals, the evidence for its occurrence in humans is far less compelling, especially with regard to declarative memory. In fact, reactivating a declarative memory often makes it more robust and less susceptible to subsequent disruptions. Here we show that existing declarative memories can be selectively impaired by using a noninvasive retrieval-relearning technique. In six experiments, we show that this reconsolidation-associated amnesia can be achieved 48 h after formation of the original memory, but only if relearning occurred soon after retrieval. Furthermore, the amnesic effect persists for at least 24 h, cannot be attributed solely to source confusion and is attainable only when relearning targets specific existing memories for impairment. These results demonstrate that human declarative memory can be selectively rewritten during reconsolidation.
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http://dx.doi.org/10.1073/pnas.1218472110DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3677482PMC
June 2013

Understanding depressive rumination from a mood-as-input perspective: effects of stop-rule manipulation.

Behav Res Ther 2013 Jun 6;51(6):300-6. Epub 2013 Mar 6.

Clinical, Educational & Health Psychology, University College London, Gower Street, London WC1E 6BT, UK.

The current study tested the mood-as-input hypothesis account of perseverative rumination in 25 participants with a diagnosis of major depressive disorder and 25 healthy controls. It also examined the factors underlying mood changes within a bout of rumination and their relations with trait rumination and metacognitive beliefs about rumination. A structured rumination interview was used to facilitate participants' reflection on two previous depressive incidents while deploying a specific stop-rule for the task (either a goal-guided or feeling-guided stop-rule). As predicted by the mood-as-input hypothesis, perseveration exhibited by depressed participants was affected by the interaction between diagnosis and stop-rule, with levels of perseveration being greatest when depressed participants used the goal-guided stop-rule. Increases in negative mood over the rumination interview were shown to be influenced only by participants' diagnostic status, regardless of their stop-rule. Compared to healthy controls, depressed participants also reported a preferential use of the goal-guided stop-rule in response to negative mood states in their daily lives. The findings about the dependence of rumination on stop-rule use within the depressed sample support the use of metacognitive treatment approaches in which patients are encouraged to challenge negative beliefs about the controllability of rumination.
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http://dx.doi.org/10.1016/j.brat.2013.02.007DOI Listing
June 2013

Retrieval does not always enhance suggestibility: testing can improve witness identification performance.

Law Hum Behav 2012 Dec 12;36(6):478-87. Epub 2011 Dec 12.

Department of Psychology, Iowa State University, Ames, IA 50011, USA.

Verbally recalling the appearance of a perpetrator and the details of an event can sometimes hinder later eyewitness memory performance. In two experiments, we investigated the effects of verbally recalling a face on people's ability to resist subsequent misinformation about that face. Participants watched a video of a theft and then completed either a recall test or a distractor activity. After a delay, some participants heard a piece of misinformation. Memory was assessed with a recall test in Experiment 1 and with a target-present lineup in Experiment 2. In both experiments, initial testing reduced eyewitness suggestibility for the face.
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http://dx.doi.org/10.1037/h0093931DOI Listing
December 2012

The dark side of testing memory: repeated retrieval can enhance eyewitness suggestibility.

J Exp Psychol Appl 2011 Dec 22;17(4):418-32. Epub 2011 Aug 22.

Department of Psychology, Iowa State University, Ames, IA 50011, USA.

Eyewitnesses typically recount their experiences many times before trial. Such repeated retrieval can enhance memory retention of the witnessed event. However, recent studies (e.g., Chan, Thomas, & Bulevich, 2009) have found that initial retrieval can exacerbate eyewitness suggestibility to later misleading information--a finding termed retrieval-enhanced suggestibility (RES). Here we examined the influence of multiple retrieval attempts on eyewitness suggestibility to subsequent misinformation. In four experiments, we systematically varied the number of initial tests taken (between zero and six), the delay between initial testing and misinformation exposure (~30 min or 1 week), and whether initial testing was manipulated between- or within-subjects. University undergraduate students were used as participants. Overall, we found that eyewitness suggestibility increased as the number of initial tests increased, but this RES effect was qualified by the delay and by whether initial testing occurred in a within- or between-subjects manner. Specifically, the within-subjects RES effect was smaller than the between-subjects RES effect, possibly because of the influence of retrieval-induced forgetting/facilitation (Chan, 2009) when initial testing was manipulated within subjects. Moreover, consistent with the testing effect literature (Roediger & Karpicke, 2006), the benefits of repeated testing on later memory were stronger after a 1-week delay than after a 30-min delay, thus reducing the negative impact of RES in long-term situations. These findings suggest that conditions that are likely to occur in criminal investigations can either increase (repeated testing) or reduce (delay) the influence of RES, thus further demonstrating the complex relationship between eyewitness memory and repeated retrieval.
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http://dx.doi.org/10.1037/a0025147DOI Listing
December 2011

Paradoxical effects of testing: retrieval enhances both accurate recall and suggestibility in eyewitnesses.

J Exp Psychol Learn Mem Cogn 2011 Jan;37(1):248-55

Department of Psychology, Iowa State University of Science and Technology, Ames, IA 50011, USA.

Although retrieval practice typically enhances memory retention, it can also impair subsequent eyewitness memory accuracy (Chan, Thomas, & Bulevich, 2009). Specifically, participants who had taken an initial test about a witnessed event were more likely than nontested participants to recall subsequently encountered misinformation—an effect we called retrieval-enhanced suggestibility (RES). Here, we sought to test the generality of RES and to further elucidate its underlying mechanisms. To that end, we tested a dual mechanism account, which suggests that RES occurs because initial testing (a) enhances learning of the later misinformation by reducing proactive interference and (b) causes the reactivated memory trace to be more susceptible to later interference (i.e., a reconsolidation account). Three major findings emerged. First, RES was found after a 1-week delay, where a robust testing benefit occurred for event details that were not contradicted by later misinformation. Second, blockage of reconsolidation was unnecessary for RES to occur. Third, initial testing enhanced learning of the misinformation even when proactive interference played a minimal role.
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http://dx.doi.org/10.1037/a0021204DOI Listing
January 2011

True and false memories in the DRM paradigm on a forced choice test.

Memory 2010 May 19;18(4):375-84. Epub 2010 Apr 19.

Department of Psychology, Washington University in St. Louis, MO 63105, USA.

Participants studied lists of semantic associates that converged on a non-presented critical word (e.g., sleep; Deese, 1959; Roediger & McDermott, 1995) and took a two-alternative forced choice test. At test, each critical non-presented word was paired with a studied word from the same list. The test was administered either immediately or 7 days after the study phase. Accuracy in distinguishing between the non-presented critical word and the studied list word was above chance at immediate testing. After a 7-day retention interval, however, accuracy did not differ from chance performance: participants were as likely to choose the non-presented critical word as the studied list word.
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http://dx.doi.org/10.1080/09658211003685533DOI Listing
May 2010

Long-term effects of testing on the recall of nontested materials.

Authors:
Jason C K Chan

Memory 2010 Jan 1;18(1):49-57. Epub 2009 Dec 1.

Department of Psychology, W112 Lagomarcino Hall, Ames, IA 50011-3180, USA.

Testing, or memory retrieval, is a powerful way to enhance long-term retention of studied material. Recent studies have shown that testing can also benefit later retention of related but nontested material (a finding known as retrieval-induced facilitation, Chan, McDermott, & Roediger, 2006), but the long-term consequences of this benefit is unknown. In the current experiment three retention intervals-20 minutes, 24 hours, 7 days-were used to assess the effects of testing on subsequent recall of the nontested material. The results indicate that the magnitude of retrieval-induced facilitation, like that of the testing effect (i.e., the memorial benefit of testing on the tested material), increases with delay at the beginning (i.e., between 20 minutes and 24 hours) but asymptotes afterward (i.e., between 24 hours and 7 days). Theoretical and applied implications of this finding are discussed.
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http://dx.doi.org/10.1080/09658210903405737DOI Listing
January 2010

Recalling a witnessed event increases eyewitness suggestibility: the reversed testing effect.

Psychol Sci 2009 Jan 25;20(1):66-73. Epub 2008 Nov 25.

Department of Psychology, W112 Lagomarcino Hall, Iowa State University, Ames, IA 50011-3180, USA.

People's later memory of an event can be altered by exposure to misinformation about that event. The typical misinformation paradigm, however, does not include a recall test prior to the introduction of misinformation, contrary to what real-life eyewitnesses encounter when they report to a 911 operator or crime-scene officer. Because retrieval is a powerful memory enhancer (the testing effect), recalling a witnessed event prior to receiving misinformation about it should reduce eyewitness suggestibility. We show, however, that immediate cued recall actually exacerbates the later misinformation effect for both younger and older adults. The reversed testing effect we observed was based on two mechanisms: First, immediate cued recall enhanced learning of the misinformation; second, the initially recalled details became particularly susceptible to interference from later misinformation, a finding suggesting that even human episodic memory may undergo a reconsolidation process. These results show that real-life eyewitness memory may be even more susceptible to misinformation than is currently envisioned.
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http://dx.doi.org/10.1111/j.1467-9280.2008.02245.xDOI Listing
January 2009

Contextual processing in episodic future thought.

Cereb Cortex 2009 Jul 2;19(7):1539-48. Epub 2008 Nov 2.

Department of Psychology, Washington University in St Louis, St Louis, MO 63130, USA.

Remembering events from one's past (i.e., episodic memory) and envisioning specific events that could occur in one's future (i.e., episodic future thought) invoke highly overlapping sets of brain regions. The present study employed functional magnetic resonance imaging to test the hypothesis that one source of this shared architecture is that episodic future thought--much like episodic memory--tends to invoke memory for known visual-spatial contexts. That is, regions of posterior cortex (within posterior cingulate cortex [PCC], parahippocampal cortex [PHC], and superior occipital gyrus [SOG]) elicit indistinguishable activity during remembering and episodic future thought, and similar regions have been identified as important for establishing visual-spatial contextual associations. In the present study, these regions were similarly engaged when participants thought about personal events in familiar contexts, irrespective of temporal direction (past or future). The same regions, however, exhibited very little activity when participants envisioned personal future events in unfamiliar contextual settings. These findings suggest that regions within PCC, PHC, and SOG support the activation of well-known contextual settings that people tend to imagine when thinking about personal events, whether in the past or future. Hence, this study pinpoints an important similarity between episodic future thought and episodic memory.
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http://dx.doi.org/10.1093/cercor/bhn191DOI Listing
July 2009

The effects of frontal lobe functioning and age on veridical and false recall.

Psychon Bull Rev 2007 Aug;14(4):606-11

Washington University, St. Louis, Missouri, USA.

Older adults' heightened susceptibility to false memories has been linked to compromised frontal lobe functioning as estimated by Glisky and colleagues' (Glisky, Polster, & Routhieaux, 1995) neuropsychological battery (e.g., Butler, McDaniel, Domburg, Price, & Roediger, 2004). This conclusion, however, rests on the untested assumption that young adults have uniformly high frontal functioning. We tested this assumption, and we correlated younger and older adults' frontal scores with veridical and false recall probabilities with prose materials. Substantial variability in scores on the Glisky battery occurred for younger (and older) adults. However, frontal scores and age were independent contributors to recall probabilities. Frontal functioning is not the sole cause of older adults' heightened susceptibility to false memories.
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http://dx.doi.org/10.3758/bf03196809DOI Listing
August 2007

The testing effect in recognition memory: a dual process account.

J Exp Psychol Learn Mem Cogn 2007 Mar;33(2):431-7

Department of Psychology, Washington University, St. Louis, MO 63130, USA.

The testing effect, or the finding that taking an initial test improves subsequent memory performance, is a robust and reliable phenomenon--as long as the final test involves recall. Few studies have examined the effects of taking an initial recall test on final recognition performance, and results from these studies are equivocal. In 3 experiments, we attempt to demonstrate that initial testing can change the ways in which later recognition decisions are executed even when no difference can be detected in the recognition hit rates. Specifically, initial testing was shown to enhance later recollection but leave familiarity unchanged. This conclusion emerged from three dependent measures: source memory, exclusion performance, and remember/know judgments.
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http://dx.doi.org/10.1037/0278-7393.33.2.431DOI Listing
March 2007

Effects of repetition on memory for pragmatic inferences.

Mem Cognit 2006 Sep;34(6):1273-84

Department of Psychology, Washington University, St. Louis, Missouri 63130, USA.

Social interaction requires active inferential processing on the part of the listener. Such inferences can affect memory. For example, after hearing the karate champion hit the cinder block, one might erroneously recollect having heard the verb broke (Brewer, 1977)--a reasonable inference, but one not logically necessitated. The mechanisms behind this type of erroneous recollection have not been much explored. Experiments in the present article assessed the influence of repetition, response deadline, and age (cf. Jacoby, 1999), in an effort to demonstrate the dual contributions of familiarity and recollection underlying this phenomenon. For older adults, repetition at encoding increased the later likelihood of erroneously recognizing pragmatic inferences. For younger adults, repetition exerted the opposite effect. Both age groups, however, benefited from a second study-test trial. Experiment 2 demonstrated a similar interaction on a cued recall test for younger adults, whereby repetition exerted different influences as a function of time permitted during retrieval. Implications for theories of memory and discourse processing are considered.
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http://dx.doi.org/10.3758/bf03193271DOI Listing
September 2006

Retrieval-induced facilitation: initially nontested material can benefit from prior testing of related material.

J Exp Psychol Gen 2006 Nov;135(4):553-71

Department of Psychology, Washington University, St. Louis, MO 63130-4899, USA.

Classroom exams can assess students' knowledge of only a subset of the material taught in a course. What are the implications of this approach for long-term retention? Three experiments (N = 210) examined how taking an initial test affects later memory for prose materials not initially tested. Experiment 1 shows that testing enhanced recall 24 hr later for the initially nontested material. This facilitation was not seen for participants given additional study opportunities without initial testing. Experiment 2 extends this facilitative effect to a within-subjects design. Experiment 3 demonstrates that this facilitation can be modulated by conscious strategies. These results have implications for educational practice and the theoretical developments of the testing effect, associative memory, and retrieval inhibition.
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http://dx.doi.org/10.1037/0096-3445.135.4.553DOI Listing
November 2006