P–264 Clinical relevance of re-expansion after blastocyst thawing

2021 ◽  
Vol 36 (Supplement_1) ◽  
Author(s):  
M Aparici. González ◽  
L Herrer. Grassa ◽  
L Cascale. Romero ◽  
J Lláce. Aparicio ◽  
J Te. Morro ◽  
...  

Abstract Study question Are there any differences in clinical outcomes after SET of re-expanded versus non-re-expanded blastocysts? Summary answer The transfer of re-expanded thawed blastocysts is associated with improved clinical outcomes. What is known already Improvements in embryo culture conditions, endometrial receptivity protocols and vitrification as a revolutionary cryopreservation technique have allowed the expansion of blastocyst stage transfers (Lieberman and Tucker, 2006; Stanger et al., 2012; Rienzi et al., 2017), increasing clinical pregnancy and implantation rates in IVF cycles. The re-expansion of thawed blastocyst at the time of transfer has been considered as a good prognosis factor, but not always thawed embryos re-expand. To evaluate the relevance of this event, we compared the clinical results of the re-expanded embryos versus the collapsed ones after their thawing and transfer. Study design, size, duration A total number of 1.125 frozen-thawed blastocyst transfers were included in this retrospective observational study between January 2018 and December 2020. Seven hundred and eighty-six thawed blastocyst were fully expanded at the time of the transfer and 339 thawed blastocysts were non-re-expanded when they were transferred. Participants/materials, setting, methods 1.125 single frozen-thawed blastocyst embryo transfer (SET) cycles (802 from donated and 319 from autologous oocytes) were divided in two groups (re-expanded vs non-re-expanded). Positive beta human chorionic gonadotrophin (bHCG), pregnancy rate (PR), early miscarriage rate (EMR) and live birth rate (LBR) were compared between the two groups. Blastocysts were thawed using an Irvine Scientific® Thaw kit, Irvine Scientific® and were transferring in culture medium (Global® Total® LP, CooperSurgical®). Main results and the role of chance During 2018, 190 re-expanded blastocyst and 94 non-re-expanded were transferred. Statistical significant differences were found in the percentage of positive bHCG (48.4% vs 30.9%, p < 0,0048) and PR (39.5% vs 25.5%, p < 0,0203), respectively. In 2019, statistical differences were found in the LBR between 307 re-expanded blastocyst and 124 non-re-expanded (30.6% vs 12.9%; p < 0,00001). Differences were also found in positive bHCG (50.2% vs 21.8%, p < 0,00001) and PR (40.7% vs 15.3%, p < 0,00001), respectively. Finally, in 2020, 289 re-expanded blastocyst and 121 non-re-expanded were transferred, and significant differences were obtained in the percentage of positive bHCG (46.8% vs 22.3%, p < 0,00001) and PR (32.9% vs 15.7%, p < 0,00001), respectively. Globally, all the variables analysed were statistically significant in favour of the re-expanded embryo group: positive bHCG (48.7% vs 24.5%; p < 0,00001), PR (37.5% vs 18.3%; p < 0,00001) and LBR (20.1% vs 9.5%; p < 0,00001), except for EMR. Limitations, reasons for caution The inherent limitations to a retrospective design. Larger studies are warranted in order to reach robust conclusions on the subject. Wider implications of the findings: Transfer of re-expand blastocyst could be a positive indicator of clinical outcomes. In case of non-re-expand embryos, transfer of two could be reasonable. Trial registration number NONE

2021 ◽  
Vol 36 (Supplement_1) ◽  
Author(s):  
E Brinkmann ◽  
C Demmers. va. d. Werken ◽  
L Ramos

Abstract Study question Should 1PN embryos be considered suitable for transfer when normal development is observed at day 3 or day 5? Summary answer In IVF/ICSI cycles, 1PN zygotes are encountered in 2.7% of inseminated oocytes. Transfer of 1PN-embryos should be considered in the absence of suitable 2PN embryos. What is known already During in vitro fertilisation (IVF) and intracytoplasmic sperm injection (ICSI) zygotes containing only a single pronucleus (monopronuclear, 1PN) are encountered in 1–7.7% of cases, while the display of two pronuclei is expected in a normally fertilised oocyte. A 1PN zygote can be of gynogenetic or androgenetic origin, but it can also be biparental. Gynogenetic and androgenetic 1PN embryos can be haploid or diploid, so a diploid 1PN embryo is not guaranteed to be normally fertilised. Generally, 1PN are discarded, as they have an increased risk for aneuploidy. However, sporadically they can develop into healthyl babies. Study design, size, duration 1PN-zygotes (n = 1287, 2.7% from all inseminated oocytes) from 1–1–2016 up to 15–12–2020 were retrospectively evaluated. The development and fate (discarded/transferred/cryopreserved) of all embryos were recorded. Embryos were evaluated at day 2, 3 or 5 of development. The policy of our unit is that, in absence of 2PN embryos, normal developed 1PN-embryos can be transferred on day 3. Supernumerary 1PN embryos can be cryopreserved at blastocyst stage. Ongoing pregnancies from fresh embryo transfers (ET) were analysed. Participants/materials, setting, methods In 946 IVF/ICSI cycles, at least one 1PN zygote was observed (total 1287 embryos). ICSI with ejaculated, PESA or TESE sperm counted for a total of 795 embryos, IVF cycles for 494 embryos. Embryo evaluation was performed using a home-made numerical algorithm: A (top embryo; 150–200 points), B (regular embryo; 100–149 points) or C (poor embryo; 0–99 points). Monopronuclear embryos always scored lower than equal developed 2PN embryos. Blastocyst evaluation was according to Gardner score. Main results and the role of chance From the 795 ICSI embryos, 49 (6.1%) were used for fresh ET (26 scored quality A or B), and a total of 60 embryos developed to blastocyst and were cryopreserved. From these 49 ICSI transfers, 4 (8.1%) ongoing pregnancies were obtained, all 4 from DET (1PN+2PN embryo), from which one twin pregnancy was confirmed. From the 494 IVF embryos, 41 (8.3%) were used for fresh ET (24 scored A or B), and 62 blastocysts were cryopreserved. A total of 9/41 (22%) ongoing pregnancies were obtained: 5 from SET (1PN) and 4 from DET (1PN+ 2PN embryo). Therefore, in only five IVF cycles a confirmed pregnancy was observed from a 1PN embryo (all A-quality embryos). Considering six ongoing pregnancies with complete certainty of monopronuclear origin from fresh tranfers could be confirmed from our retrospective data, we can conclude that although the live birth rate of these embryos is very low (around 0,5- 1.0%), they should not be discarded when development is normal and no dipronuclear embryos are present. Limitations, reasons for caution Cryo-thawing data is missing as these embryos were not differentially marked at freezing. Therefore, the cumulative pregnancies from monopronuclear embryos could be higher. Embryos were not evaluated in a time lapse system, so asynchronicity of PN formation could explain missing the right moment for evaluation, while normal fertilized. Wider implications of the findings: Notably, IVF monopronuclear embryos display a higher developmental potential than those derived from ICSI. We suggest that, in absence of dipronuclear embryos, culture to blastocyst stage before considering fresh ET or cryopreservation will help differentiate viable 1PN embryos, reducing the higher chance of genetic anomalies and miscarriages. Trial registration number N.A.


2021 ◽  
Vol 36 (Supplement_1) ◽  
Author(s):  
E Young ◽  
S Garci Argibay ◽  
L Isa ◽  
M P Zappacost. Villarroel ◽  
R Inza ◽  
...  

Abstract Study question What is the destination of supernumerary embryos after a positive pregnancy test? Summary answer Half of the surplus cryopreserved embryos in assisted reproduction treatments are not transferred. What is known already Many of the surpernumerary cryopreserved embryos in assisted reproductive technologies are not transferred. This is a constant issue in many fertility centers around the world. Our objective was to report what happens with vitried surplus embryos after IVF in patients with a positive pregnancy test, carrying out an analysis according to age and final evolution of the pregnancy. Study design, size, duration This is a retrospective descriptive study. We analyzed 245 embryo transfer cycles, performed between January 2013 to December 2017, in 235 patients with a positive pregnancy test and who vitrified surplus embryos. Participants/materials, setting, methods All the patients underwent treatment with their own oocytes. The variables studied were: age, miscarriage rate (MR) and live birth rate (LBR). We compared the destination of the cryopreserved embryos according to the patient’s age and pregnancy evolution. Statistical analysis was performed with Fisher’s exact test. Main results and the role of chance 20% of the IVF cycles (n = 49) were performed in women older than 40 years, 42% between 35 and 39 (n = 103) and 38% in women younger than 35 (n = 94). Average age was 35.8 ± 4.1 years. 859 embryos were cryopreserved (3.5 ± 1.9 cryopreserved embryos/patient). Average search time for surplus embryos was 20.5 ± 17.9 months, rising to 36.9 ± 14.9 months after delivery and decreasing to 8.7 ± 7.8 months after miscarriage (P < 0.0001). Up to date there are 118 (48.2%) patients whose cryopreserved embryos have not been transferred yet. Signficant differences were found in the three groups in using the cryopreserved embryos according to whether or not they had delivery. Almost half of the surplus cryopreserved embryos are not transferred. Regardless of the age of the patient, all groups showed the same behavior regarding the utilization of the cryopreserved embryos after delivery. It is essential to advise couples who perform assisted reproductive technologies, with a good probability of success (regardless of the patient’s age), about the responsibility that embryonic cryopreservation entails. Argentine legislation has limitations regarding the availability of cryopreserved surplus embryos. Limitations, reasons for caution This is a retrospective study. Wider implications of the findings: We believe that Public Health policies related to this issue should be re evaluated based on these results. Trial registration number Not applicable


2020 ◽  
Author(s):  
Meijia Wang ◽  
Zhenli Huang ◽  
Kun Tang ◽  
Pengfei Gao ◽  
Yanjiao Lu ◽  
...  

Abstract Background:COVID-19 causes epidemics and pandemics worldwide, but the role of pathophysiological parameters particularly systemic inflammation in COVID-19 has not been understood. We aimed to investigate clinical outcomes in view of systemic inflammation in COVID-19.Methods:In this retrospective study, the demographic and clinical data of 225 confirmed COVID-19 cases on admission at Tongji Hospital from January 28 to February 15, 2020, were extracted and analyzed. These patients were categorized by inflammation state on the basis of the expression of inflammatory factors or classified as severe and non-severe according to 2019 American Thoracic Society / Infectious Disease Society of America guidelines.Results: Among 225 patients with confirmed COVID-19, 155 patients (68.9%) categorized into hyperinflammation group and 70 (31.1%) were non- hyperinflammation group. Compared to non-hyperinflammation group, hyperinflammation group more frequently had chest tightness/dyspnea and lymphopenia, aberrant multiple indexes of organ function including the heart, liver, kidney, and coagulation, with higher level of C-reactive protein (hsCRP) as well as interleukin (IL)-6, IL-8, tumour necrosis factor α (TNF-α), etc. Hyperinflammation group were more likely to admit to intensive care unit (ICU) (52.3% vs 5.7%), receive ventilation (84.5% vs 10.0%) and be with higher mortality (44.5% vs 5.7%) than non-hyperinflammation group. The mortality of severe patients with hyperinflammation (60/99, 60.6%) was significantly higher than without hyperinflammation (2/20, 10.0%). Non-severe patients with hyperinflammation even tended to have higher mortality (9/56, 16.1%) than those in severe cases without hyperinflammation (2/20, 10%).Conclusion: Excessive systemic inflammation was correlated highly with poor clinical outcomes in COVID-19, particularly in severe cases. Non-severe patients with hyperinflammation even tended to have higher mortality than those in severe cases without hyperinflammation.Trial registration: This is a retrospective observational study without a trial registration number.


2021 ◽  
Vol 36 (Supplement_1) ◽  
Author(s):  
S H Tan ◽  
A Q Y Chan ◽  
A Y X Lim ◽  
M W Lim

Abstract Study question The objective of this study is to evaluate the effect of trophectoderm (TE) biopsy on different blastocyst stages and its clinical outcome. Summary answer Our results showed that TE biopsy significantly reduced the clinical outcome of fully hatched blastocyst. What is known already: TE biopsy is a method widely practiced to harvest cells to determine the chromosomal constitution of a blastocyst, ensuring higher implantation and healthy pregnancies. The effect on clinical outcome after transferring blastocysts biopsied at different blastocysts stages has not been extensively studied. Study design, size, duration This retrospective study was conducted from January 2017 until July 2019 at Alpha IVF & Women’s Specialists. Following laser assisted hatching on day 3, TE biopsy was performed on unhatched, hatching and fully hatched day–5 blastocysts. A total of 1,020 single euploid blastocysts transfer (SBT) were performed. The average maternal age was 31.7. Implantation rates (IR) were evaluated for all stages of hatching (Unhatched: BG3 & 4; hatching: BG5; fully hatched: BG6). Participants/materials, setting, methods Laser assisted hatching (Hamilton Thorne Bioscience, USA) was performed on day–3 and subsequently cultured to blastocyst-stage. Different hatching stages were observed using embryoscope time-lapse system (Vitrolife, Sweden) and were recorded. Day–5 blastocysts with at least BG3BB grade (Gardner’s System) were selected for TE biopsy and the biopsied cells were sent for preimplantation genetic testing for aneuploidy (PGT-A) using Next-Generation Sequencing (Life Technologies, USA). All blastocysts were vitrified and warmed using the Cryotec Method (Cryotech, Japan). Main results and the role of chance: All 1,020 blastocysts survived post-warmed (post-warm survival rate= 100%) and were transferred in frozen transfer cycles. TE biopsy performed on unhatched blastocysts showed a comparable IR to hatching blastocysts (60.0% [15/25] and 65.2% [627/961]). While fully hatched blastocysts (44.12% [15/34]) show a significantly lower IR when compared to hatching blastocysts (65.2% [627/961]), no significant difference was seen when comparing unhatched blastocysts to fully hatched blastocysts (60.0% [15/25] and 44.12% [15/34]; p = 0.2949). Limitations, reasons for caution The sample size was comparatively smaller in the unhatched and fully hatched group than the hatching group. Further studies with a larger sample size is recommended to ascertain the clinical outcome. Since this is a retrospective study and biopsy was done by different embryologists, the biopsy technique was not controlled. Wider implications of the findings: To achieve higher clinical pregnancy, it is recommended to perform TE biopsy before the blastocysts is fully hatched. Trial registration number Not applicable


2021 ◽  
Vol 26 (1) ◽  
Author(s):  
Ahmed Elsayed Abdelaal ◽  
Mohamed Atef Behery ◽  
Ahmed Farouk Abdelkawi

Abstract Background Hypogonadotropic hypogonadism (HH) is a rare condition in which there is gonadal hypofunction due to absence of gonadotropin drive. In this condition, there are very low serum levels of gonadotropins. Pituitary gland may itself have some disease or disorder, or there may be loss of gonadotropin-releasing hormone (GnRH) pulses from the hypothalamus. The pharmacological interventions in HH women formed the basis for superovulation strategies for assisted reproduction techniques (ART) with a special reference to the role of LH and its impact on oocyte and embryo quality. Results The medians ±inter quartile ranges for number of oocytes retrieved, number of MII oocytes, and number of embryos transferred were 5±7, 4±3, and 3±1 respectively. The pregnancy rate was 31.5% for this group of patients. The live birth rate and miscarriage rate were 21% and 11.5% respectively. Conclusion The reproductive outcomes of patients of hypogonadotrophic hypogonadism are reasonable after ICSI and clinical trials are recommended to corroborate this concern.


2021 ◽  
Author(s):  
Haitao Xi ◽  
Lin Qiu ◽  
Yaxin Yao ◽  
Lanzi Luo ◽  
Liucai Sui ◽  
...  

Abstract Background: This retrospective cohort study determines whether noninvasive chromosome screening (NICS) for aneuploidy can improve the clinical outcomes of patients with recurrent pregnancy loss (RPL) or repeated implantation failure (RIF) in assisted reproductive technology.Methods: A total of 273 women with a history of RPL or RIF between 2018 and 2021 were included in this study. We collected data of all oocyte retrieval cycles and single blastocyst resuscitation transfer cycles.Results: For the RPL patients, NICS reduced the miscarriages rate per frozen embryo transfer (FET), improved the ongoing pregnancies rate and live birth rate: 17.9% vs 42.6%, adjusted OR 0.39, 95% CI 0.16–0.95; 40.7% vs 25.0%, adjusted OR 2.00, 95% CI 1.04–3.82; 38.9% vs 20.6%, adjusted OR 2.53, 95% CI 1.28–5.02, respectively. For the RIF patients, the pregnancy rates per FET in the NICS group were significantly higher than in the non-NICS group (46.9% vs. 28.7%, adjusted OR 2.82, 95% CI 1.20–6.66).Conclusions: This study demonstrated that selection of euploid embryos through NICS can reduce the miscarriage rate of patients with RPL and improve the clinical pregnancy rate of patients with RIF. Our data suggested that NICS could be used as a diagnostic test in clinical practice.


2021 ◽  
Vol 12 ◽  
Author(s):  
Jie Zhang ◽  
Yi-Fei Sun ◽  
Yue-Ming Xu ◽  
Bao-jun Shi ◽  
Yan Han ◽  
...  

ObjectiveTo investigate the factors that influence luteal phase short-acting gonadotropin-releasing hormone agonist (GnRH-a) long protocol and GnRH-antagonist (GnRH-ant) protocol on pregnancy outcome and quantify the influence. About the statistical analysis, it is not correct for the number of gravidities.MethodsInfertile patients (n = 4,631) with fresh in-vitro fertilization/intracytoplasmic sperm injection (IVF/ICSI) and embryo transfer were divided into GnRH-a long protocol (n =3,104) and GnRH-ant (n =1,527) protocol groups and subgroups G1 (EMT ≤7mm), G2 (7 mm <EMT ≤10 mm), and G3 (EMT >10 mm) according to EMT on the trigger day. The data were analyzed.ResultsThe GnRH-ant and the GnRH-a long protocols had comparable clinical outcomes in the clinical pregnancy, live birth, and miscarriage rate after propensity score matching. In the medium endometrial thickness of 7–10 mm, the clinical pregnancy rate (61.81 vs 55.58%, P < 0.05) and miscarriage rate (19.43 vs 12.83%, P < 0.05) of the GnRH-ant regime were significantly higher than those of the GnRH-a regime. The EMT threshold for clinical pregnancy rate in the GnRH-ant group was 12 mm, with the maximal clinical pregnancy rate of less than 75% and the maximal live birth rate of 70%. In the GnRH-a long protocol, the optimal range of EMT was >10 mm for the clinical pregnancy rate and >9.5 mm for the live birth rate for favorable clinical outcomes, and the clinical pregnancy and live birth rates increased linearly with increase of EMT. In the GnRH-ant protocol, the EMT thresholds were 9–6 mm for the clinical pregnancy rate and 9.5–15.5 mm for the live birth rate.ConclusionsThe GnRH-ant protocol has better clinical pregnancy outcomes when the endometrial thickness is in the medium thickness range of 7–10 mm. The optimal threshold interval for better clinical pregnancy outcomes of the GnRH-ant protocol is significantly narrower than that of the GnRH-a protocol. When the endometrial thickness exceeds 12 mm, the clinical pregnancy rate and live birth rate of the GnRH-ant protocol show a significant downward trend, probably indicating some negative effects of GnRH-ant on the endometrial receptivity to cause a decrease of the clinical pregnancy rate and live birth rate if the endometrial thickness exceeds 12 mm.


2021 ◽  
Vol 36 (Supplement_1) ◽  
Author(s):  
A Tanaka ◽  
Y Yanagihara ◽  
M Nagayoshi ◽  
T Yamaguchi ◽  
I Tanaka ◽  
...  

Abstract Study question What technique can be used to successfully cryopreserve five or fewer testicular spermatozoa from non-obstructive azoospermic men? Summary answer This method for cryopreserving five or fewer spermatozoa from non-obstructive azoospermic men showed a recovery rate above 90% and a survival rate of about 70%. What is known already Clinical outcomes of ICSI when using only five or fewer testicular spermatozoa after cryopreservation have been unsuccessful and are considered to be inferior to those using testicular fresh spermatozoa from Micro-TESE. A possible cause of these poor results has been the lack of a successful freezing technique. In these cases, repeated Micro-TESE and simultaneous oocyte pick up has been the only available treatment. Study design, size, duration Evaluation of the efficiency of cryopreservation by modified permeable cryoprotectant-free vitrification method (HTF supplemented with 0.1M sucrose and 10% SPS) for five or fewer testicular spermatozoa from 113 non-obstructive azoospermic men using Micro-TESE was conducted retrospectively at St. Mother Clinic between 2011 and 2018. Participants/materials, setting, methods This study included 113 non-obstructive azoospermic men. Each motile spermatozoon was carefully aspirated tail first into the pipette, put into a 2-μl microdroplet media of the vitrification medium near the tip of the Cryotop (Kitazato Corporation, Tokyo, Japan) submerged in liquid nitrogen vapor for 2 min and then immediately plunged in liquid nitrogen. The vitrified spermatozoa were warmed by dipping them into a droplet media. Successfully recovered motile sperm were selected and used for ICSI. Main results and the role of chance Number of patients, transfer cycles and collected sperms were 113, 192 and 560. Mean age of patients and their wives were 32.0±3.7y and 28.4±5.8y. Clinical pregnancy rate, miscarriage rate, live birth rate and number of live offspring were 24.0% (46/192), 19.6% (9/46), 19.3% (37/192) and 37 (Male: Female = 17: 20). Sperm recovery rate and survival rate were 90.3% (506/560) and 70.4% (356/506). Fertilization rate and mean number of transferred embryos were 51.6% (99/192) and 1.73 (1–2). Mean gestational weeks and mean body weight at birth were 39.23±5.27w and 2852.31±314.28g. No congenital anomalies were observed in any of the babies. Limitations, reasons for caution The maximum number of spermatozoa to which this method can be applied successfully is about 10. When the number of aspirated spermatozoa is over 10, some of them change direction and reach the mineral oil, and once this happens, they cannot be expelled out of the pipette. Wider implications of the findings: This technique is very useful for the cryopreservation of very small numbers of testicular spermatozoa (fewer than 10) in order to avoid or reduce Micro-TESE interventions. Trial registration number N/A


2020 ◽  
Vol 35 (2) ◽  
pp. 283-292 ◽  
Author(s):  
L Delaroche ◽  
P Oger ◽  
E Genauzeau ◽  
P Meicler ◽  
F Lamazou ◽  
...  

Abstract STUDY QUESTION How do manufacturers perform embryotoxicity testing in their quality control programs when validating IVF consumables? SUMMARY ANSWER The Mouse Embryo Assay (MEA) and Human Sperm Survival Assay (HSSA) used for IVF disposables differed from one manufacturer to another. WHAT IS KNOWN ALREADY Many components used in IVF laboratories, such as culture media and disposable consumables, may negatively impact human embryonic development. STUDY DESIGN, SIZE, DURATION Through a questionnaire-based survey, the main manufacturers of IVF disposable devices were contacted during the period November to December 2018 to compare the methodology of the MEA and HSSA. We focused on catheters for embryo transfer, catheters for insemination, straws, serological pipettes, culture dishes and puncture needles used in the ART procedures. PARTICIPANTS/MATERIALS, SETTING, METHODS We approached the manufacturers of IVF disposables and asked for details about methodology of the MEA and HSSA performed for toxicity testing of their IVF disposable devices. All specific parameters like mouse strains, number of embryos used, culture conditions (media, temperature, atmosphere), extraction protocol, subcontracting, and thresholds were registered and compared between companies. MAIN RESULTS AND THE ROLE OF CHANCE Twenty-one companies were approached, of which only 11 answered the questionnaire. Significant differences existed in the methodologies and thresholds of the MEA and HSSA used for toxicity testing of IVF disposables. Importantly, some of these parameters could influence the sensitivity of the tests. LIMITATIONS, REASONS FOR CAUTION Although we approached the main IVF manufacturers, the response rate was relatively low. WIDER IMPLICATIONS OF THE FINDINGS Our study confirms the high degree of heterogeneity of the embryotoxicity tests performed by manufacturers when validating their IVF disposable devices. Currently, no regulations exist on this issue. Professionals should call for and request standardization and a future higher degree of transparency as regards embryotoxicity testing from supplying companies; moreover, companies should be urged to provide the users clear and precise information about the results of their tests and how testing was performed. Future recommendations are urgently awaited to improve the sensitivity and reproducibility of embryotoxicity assays over time. STUDY FUNDING/COMPETING INTEREST(S) This study did not receive any funding. L.D. declares a competing interest with Patrick Choay SAS. TRIAL REGISTRATION NUMBER N/A


2004 ◽  
Vol 63 (3) ◽  
pp. 143-149 ◽  
Author(s):  
Fred W. Mast ◽  
Charles M. Oman

The role of top-down processing on the horizontal-vertical line length illusion was examined by means of an ambiguous room with dual visual verticals. In one of the test conditions, the subjects were cued to one of the two verticals and were instructed to cognitively reassign the apparent vertical to the cued orientation. When they have mentally adjusted their perception, two lines in a plus sign configuration appeared and the subjects had to evaluate which line was longer. The results showed that the line length appeared longer when it was aligned with the direction of the vertical currently perceived by the subject. This study provides a demonstration that top-down processing influences lower level visual processing mechanisms. In another test condition, the subjects had all perceptual cues available and the influence was even stronger.


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