Emergent Patterns, Collaborative Networks and Thematic Evolution on Black Stain and Dental Caries: A Scientometric Study.

AIM: To conduct a scientometric analysis on black stains, and dental caries, with a focus on identifying emergent patterns, collaborative networks, and thematic evolution. MATERIALS AND METHODS: A retrospective, descriptive, observational study was conducted using a scientometric approach. The Scopus database was utilized for literature search, selecting articles published between 1976 and 2023. The literature search was carried out on February 8, 2024, using AND and OR Boolean operators which were adapted to the search strategy. Finally, SciVal used different scientometric indicators such as "Scholarly Output", "Views Count", "Field-Weighted Citation Impact" and the "Citation Count". RESULTS: A total of 13 documents from 10 different sources were analyzed, covering a period from 1976 to 2023. Despite an annual growth rate of 0%, each document has an average of 21.08 citations, indicating their relevance in the field. The documents have an average age of 12.9 years and contain 336 references. A total of 143 additional keywords and 26 author keywords were identified. The documents were written by 62 different authors, with an average of 5 coauthors per document and 30.77% international coauthorships. CONCLUSION: The results indicate a significant relevance of the documents in the field, a notable collaboration among authors, and a significant thematic evolution in the research topics. The mentioned institutions and sources produced documents with notable results, indicating a significant interest and impact in the field. CLINICAL SIGNIFICANCE: This study provides a detailed view of the trends and patterns in the research of dental caries and black stains. The findings can assist dental health professionals in better understanding the prevalence and impact of these conditions. Furthermore, it can guide future research and treatment strategies in this field. How to cite this article: Mayta-Tovalino F, Espinoza-Carhuancho F, Reyes-Carmona J, et al. Emergent Patterns, Collaborative Networks and Thematic Evolution on Black Stain and Dental Caries: A Scientometric Study. J Contemp Dent Pract 2024;25(4):326-330.

The increase in diaphragm thickness in preterm infants is related to birth weight: a pilot study.

Diaphragm ultrasound (DU) has been used in adult and pediatric critical patients in relation to prediction of extubation success or to detect diaphragm dysfunction, but there is a lack of evidence in neonates. Our aim is to study the evolution of diaphragm thickness in preterm infants, as well as related variables. This prospective monocentric observational study included preterm infants born before 32 weeks (PT32). We performed DU to measure right and left inspiratory and expiratory thickness (RIT, LIT, RET, and LET) and calculated the diaphragm-thickening fraction (DTF) in the first 24 h of life and then weekly until 36 weeks postmenstrual age, death, or discharge. Using multilevel mixed-effect regression, we evaluated the influence of time since birth on diaphragm measurements, as well as bronchopulmonary dysplasia (BPD), birth weight (BW), and days of invasive mechanical ventilation (IMV). We included 107 infants, and we performed 519 DUs. All diaphragm thickness increased with time since birth, but the only additional variable that influenced this growth was BW: beta coefficients RIT = 0.00006; RET = 0.00005; LIT = 0.00005; and LET = 0.00004, p < 0.001. Right DTF values remained stable since birth but left DTF increased with time only in infants with BPD.   Conclusion: In our population we found that the higher the BW, the higher diaphragm thicknesses at birth and follow-up. Contrary to the previously published findings in adult and pediatric settings, we were unable to describe a relationship between days of IMV and diaphragm thickness in PT32. The final diagnosis of BPD does not influence this increase either, but it does increase left DTF. What is Known: • Diaphragm thickness and diaphragm thickening fraction have been related to the time on invasive mechanical ventilation in adults and pediatric patients, as well as with extubation failure. • Very few evidence is yet available on the use of diaphragmatic ultrasound in preterm infants. What is New: • Birth weight is the only variable related to diaphragm thickness in preterm infants born before 32 weeks postmenstrual age. • Days of invasive mechanical ventilation do not influence diaphragm increase in thickness in preterm infants.

Histological Comparison of Post-extraction Alveolar Bone Repair Treated with Melatonin and Calcium Sulfate: An In Vivo Study in Cavia porcellus.

AIM AND OBJECTIVE: To histologically compare alveolar bone repair after tooth extraction treated with melatonin and calcium sulfate in an in vivo experimental study in guinea pigs (Cavia porcellus). MATERIALS AND METHODS: The study was of longitudinal, prospective, and experimental design in an animal bio-model. A total of 24 male guinea pigs were included, weighing from 700 to 900 g and separated into two experimental groups (melatonin and calcium sulfate) for three periods (15, 30, and 45 days) at 15-day intervals after surgery. The guinea pigs were randomly included into groups for the time evaluated. RESULTS: In relation to bone repair cells using calcium sulfate, the presence of osteoblasts at 15, 30, and 45 days was 39.0 ± 63, 55.3 ± 6.0, respectively, with 61.3 ± 10.0 cells per field. Regarding bone repair cells using melatonin, the presence of osteoblasts at 15, 30, and 45 days was 25.0 ± 3.7, 49.3 ± 1.5, respectively, with 53.6 ± 5.6 cells per field. CONCLUSION: Both melatonin and calcium sulfate were found to be useful in bone repair at a histological and clinical level, although they present certain nonsignificant, albeit marked advantages in the bone repair process when compared with the control socket at the histological level. CLINICAL SIGNIFICANCE: This research allows us to know the usefulness of these easily accessible chemicals for the generation of bone repair.

Effect of Post-bleaching Surface Microroughness with Whiteness HP Blue vs Whiteness HP Maxx on Different Locations of Bovine Enamel.

AIM: To compare the effect after bleaching with 35% hydrogen peroxide with and without calcium gluconate on surface microroughness in an in vitro study on the bovine enamel. MATERIALS AND METHODS: The study had an in vitro experimental design. The following groups were formed: group I: MV (mesiovestibular) enamel, group II: V (vestibular) enamel, and group III: DV (dystovestibular) enamel, undergoing treatment with Whiteness HP Blue (H2O2 at 35% with calcium gluconate), Whiteness HP Maxx: H2O2 at 35% (without calcium gluconate), and physiological serum. A Surftest SJ-210 digital roughness meter (Mitutoyo) was used to evaluate microroughness. RESULTS: The highest mean microroughness was found in group II (V) with 0.23 ± 0.13 µm and 0.17 ± 0.02 µm for Whiteness HP Blue and Whiteness HP Maxx, respectively. The post hoc analysis of surface microroughness subjected to H2O2 with and without calcium gluconate showed that there were only statistically significant differences between Whiteness HP Blue and the control (p = 0.032). CONCLUSION: There were no significant differences in surface microroughness on comparing the Whiteness HP Maxx group with the control group and the Whiteness HP Blue group. CLINICAL SIGNIFICANCE: The clinical importance of this study was that it allowed us to know the direct impact that bleaching agents with and without calcium have on dental structures.

Design, synthesis and biological evaluation of new carbazole derivatives as anti-cancer and anti-migratory agents.

Based on the efficacy of EHop-016 as an inhibitor of migration and Rac1 activation, a new series of carbazole derivatives has been synthesized. Cytotoxic and anti-migratory effects of these compounds were evaluated in MCF-7 and MDA-MB-231 breast cancer cell lines. Preliminary investigations of their anticancer activity demonstrated that several compounds have moderate antiproliferative effects on cancer cell lines with GI50 values in the range of 13-50 µM. Furthermore, compounds 3b and 11b inhibit migration activity of metastatic cell line MDA-MB-231 by 32% and 34%, respectively. Compound 11b was shown to inhibit activation of the Rho GTPase Rac1 by 55% at 250 nM in both MDA-MB-231 and MDA-MB-435 cell lines. Compared with the IC50 of Rac1 inhibition by lead compound EHop-016 of 1.1 µM, compound 11b demonstrates 4X improved in vitro efficacy.

Exploring the Scientific Literature Between Ultraprocessed Foods and Cancer: A Scientometric Mapping.

Objective: The objective of the study is to explore the scientific literature between ultraprocessed foods (UPFs) and cancer using a scientometric mapping. Materials and Methods: A Scopus search was conducted on February 4, 2024, limited to papers published between 2018 and 2023. We found 662 articles, 189 reviews, 68 book chapters, 13 conference papers, and 9 notes. The whole analysis included the evaluation of scholarly output by country/region, the number of scholarly papers produced (scholarly output), the number of views (view count), the field-weighted citation impact (FWCI). Results: In the analysis conducted for the period 2018-2023, a dataset was examined where the annual growth rate was 5.96%, indicating a sustained expansion of the literature. The average number of citations per paper was 18.56, underlining the impact and relevance of the publications. Sixty-six single-authored papers were identified, and international collaborations accounted for 27.23% of the collaborative efforts. The most prominent authors were Inge Huybrechts, Marc J.R. Gunter, and Edward Luciano Giovannucci. In terms of impact and visibility, Harvard University leads with 52 contributions and a field-weighted impact of 3.39. Conclusions: The literature in the field of UPFs and cancer has experienced a sustained expansion. The scientometric indicators reveal a high activity of recent academic contributions with significant impact.

Shear strength of metal brackets using LED lamps with different wavelengths: An in vitro comparative study.

AIM: To evaluate the shear strength of Orthocem and BracePaste polymerizable cement light-cured with light-emitting diode (LED) units with different wavelengths (Bluephase N) with their high power, low power, and soft start programs in the bonding of metal brackets. MATERIALS AND METHODS: In vitro experimental research was performed. Mini Roth 0.022 metal brackets (Roth Orthometric brackets) were used. The adhesives were placed on the metal brackets with Orthocem and BracePaste resin cement. To compare the average strengths, the analysis of variance (ANOVA) test was used (P < 0.05). RESULTS: The average shear strength was better with Bracepaste polymerizable cement compared to Orthocem cement in all its high power, low power, and soft star programs; the highest was Bracepaste with soft start of 26.52 MPa, and the lowest was Orthocem with soft start of 13.92 MPa. When evaluating the differences, it was found that these were statistically significant in all groups (P < 0.05). CONCLUSIONS: Differences were found in the shear strength of light-curing Orthocem and Bracepaste light-curing cement cured with LED units with different wavelengths in bonding metal brackets to the tooth in vitro.

Evaluating novel approaches for estimating awake and sleep blood pressure: design of the Better BP Study - a randomised, crossover trial.

INTRODUCTION: For many people, blood pressure (BP) levels differ when measured in a medical office versus outside of the office setting. Out-of-office BP has a stronger association with cardiovascular disease (CVD) events compared with BP measured in the office. Many BP guidelines recommend measuring BP outside of the office to confirm the levels obtained in the office. Ambulatory BP monitoring (ABPM) can assess out-of-office BP but is not available in many US practices and some individuals find it uncomfortable. The aims of the Better BP Study are to (1) test if unattended office BP is closer to awake BP on ABPM compared with attended office BP, (2) assess if sleep BP assessed by home BP monitoring (HBPM) agrees with sleep BP from a full night of ABPM and (3) compare the strengths of associations of unattended versus attended office BP, unattended office BP versus awake BP on ABPM and sleep BP on HBPM versus ABPM with markers of end-organ damage. METHODS AND ANALYSIS: We are recruiting 630 adults not taking antihypertensive medication in Birmingham, Alabama, and New York, New York. Participants are having their office BP measured with (attended) and without (unattended) a technician present, in random order, using an automated oscillometric office BP device during each of two visits within one week. Following these visits, participants complete 24 hours of ABPM and one night of HBPM, in random order. Psychosocial factors, anthropometrics, left ventricular mass index and albumin-to-creatinine ratio are also being assessed. ETHICS AND DISSEMINATION: This study was approved by the University of Alabama at Birmingham and the Columbia University Medical Center Institutional Review Boards. The study results will be disseminated at scientific conferences and published in peer-reviewed journals. TRIAL REGISTRATION NUMBER: NCT04307004.

Characterization of Novel Derivatives of MBQ-167, an inhibitor of the GTP-binding proteins Rac/Cdc42.

Rac and Cdc42, are homologous GTPases that regulate cell migration, invasion, and cell cycle progression; thus, representing key targets for metastasis therapy. We previously reported on the efficacy of MBQ-167, which blocks both Rac1 and Cdc42 in breast cancer cells and mouse models of metastasis. To identify compounds with increased activity, a panel of MBQ-167 derivatives was synthesized, maintaining its 9-ethyl-3-(1H-1,2,3-triazol-1-yl)-9H-carbazole core. Similar to MBQ-167, MBQ-168 and EHop-097, inhibit activation of Rac and Rac1B splice variant and breast cancer cell viability, and induce apoptosis. MBQ-167 and MBQ-168 inhibit Rac and Cdc42 by interfering with guanine nucleotide binding, and MBQ-168 is a more effective inhibitor of PAK (1,2,3) activation. EHop-097 acts via a different mechanism by inhibiting the interaction of the guanine nucleotide exchange factor (GEF) Vav with Rac. MBQ-168 and EHop-097 inhibit metastatic breast cancer cell migration, and MBQ-168 promotes loss of cancer cell polarity to result in disorganization of the actin cytoskeleton and detachment from the substratum. In lung cancer cells, MBQ-168 is more effective than MBQ-167 or EHop-097 at reducing ruffle formation in response to EGF. Comparable to MBQ-167, MBQ-168 significantly inhibits HER2+ tumor growth and metastasis to lung, liver, and spleen. Both MBQ-167 and MBQ-168 inhibit the cytochrome P450 (CYP) enzymes 3A4, 2C9, and 2C19. However, MBQ-168 is ~10X less potent than MBQ-167 at inhibiting CYP3A4, thus demonstrating its utility in relevant combination therapies. In conclusion, the MBQ-167 derivatives MBQ-168 and EHop-097 are additional promising anti metastatic cancer compounds with similar and distinct mechanisms.

Effects of Different Light-curing Modes on the Compressive Strengths of Nanohybrid Resin-based Composites: A Comparative In Vitro Study.

OBJECTIVE: To evaluate the effects of polymerization conducted by using LED lamps of different wavelengths (polywave and monowave) on the compressive strengths of nanohybrid composite resins Filtek™ Bulk Fill - 3M and 3M™ Filtek™ Z350 XT. MATERIALS AND METHODS: The study was prospective, experimental in vitro, and comparative. The sample consisted of nanohybrid composite resins. The sample size (n) was 100 specimens, divided into 10 groups. CRIS (Checklist for Reporting In-vitro Studies) Guidelines were used for writing this article. RESULTS: There were statistically significant differences between all groups with P < 0.001. Group 2 (nanohybrid composite resin blocks 3M™ Filtek™ Z350 XT with Monowave LED lamps) showed the highest compressive strength of 238.36±34.69N; CI (213.55-263.18) N. This was followed by Group 4 (nanohybrid composite resin blocks 3M™ Filtek™ Z350 XT with Poliwave LED lamps, High Power) and Group 6 (nanohybrid composite resin blocks 3M™ Filtek™ Z350 XT with Poliwave LED lamps, Soft Star), with compressive strengths of 222.33 ± 53.09N, and 209.21 ± 22.52N, respectively. CONCLUSIONS: Significant differences were found between the compressive strengths of 3M™ Filtek™ Z350 XT and Filtek™ Bulk Fill - 3M resins, and that of resins photopolymerized with monowave and polywave LED lamps and halogen light. Thus, the types of light and lamp directly influence the compressive strengths of the composite resins.

Speech stream segregation to control an ERP-based auditory BCI.

Objective. The use of natural sounds in auditory brain-computer interfaces (BCI) has been shown to improve classification results and usability. Some auditory BCIs are based on stream segregation, in which the subjects must attend one audio stream and ignore the other(s); these streams include some kind of stimuli to be detected. In this work we focus on event-related potentials (ERP) and study whether providing intelligible content to each audio stream could help the users to better concentrate on the desired stream and so to better attend the target stimuli and to ignore the non-target ones.Approach. In addition to a control condition, two experimental conditions, based on the selective attention and the cocktail party effect, were tested using two simultaneous and spatialized audio streams: (a) the condition A2 consisted of an overlap of auditory stimuli (single syllables) on a background consisting of natural speech for each stream, (b) in condition A3, brief alterations of the natural flow of each speech were used as stimuli.Main results. The two experimental proposals improved the results of the control condition (single words as stimuli without a speech background) both in a cross validation analysis of the calibration part and in the online test. The analysis of the ERP responses also presented better discriminability for the two proposals in comparison to the control condition. The results of subjective questionnaires support the better usability of the first experimental condition.Significance. The use of natural speech as background improves the stream segregation in an ERP-based auditory BCI (with significant results in the performance metrics, the ERP waveforms, and in the preference parameter in subjective questionnaires). Future work in the field of ERP-based stream segregation should study the use of natural speech in combination with easily perceived but not distracting stimuli.

Different effects of using pictures as stimuli in a P300 brain-computer interface under rapid serial visual presentation or row-column paradigm.

Previous proposals for controlling a P300-based BCI speller have shown an improvement using alternative images instead of letters as target stimuli under a row-column paradigm (RCP). However, the RCP is not suitable for those patients with a lack of gaze control. To solve that, the rapid serial visual presentation (RSVP) paradigm has been proposed in previous studies. The aim of the present work is to assess if a set of alternative pictures that improved performance in RCP could also improve performance in RSVP. Sixteen participants controlled four conditions in calibration and online tasks: letters in RCP, pictures in RCP, letters in RSVP and pictures in RSVP. The effect given by pictures was greater under RCP than under RSVP, both for performance and event-related potential analyses. Indeed, pictures did not show any improvement under RSVP in comparison to letters. In addition, the condition with pictures under RCP was declared the favourite by most users (68.75%), while the condition with pictures under RSVP was not chosen as favourite by any participant. Therefore, this work shows that the improvement related to the use of pictures as alternative flashing stimuli under RCP may not be transferred to RSVP. Graphical abstract.

Efficacy of Rac and Cdc42 Inhibitor MBQ-167 in Triple-negative Breast Cancer.

Triple-negative breast cancer (TNBC) is an aggressive form of breast cancer, with a high predisposition for locally invasive and metastatic cancer. With the objective to reduce cancer metastasis, we developed small molecule inhibitors to target the drivers of metastasis, the Rho GTPases Rac and Cdc42. Of these, MBQ-167 inhibits both Rac and Cdc42 with IC50s of 103 and 78 nmol/L, respectively; and consequently, inhibits p21-activated kinase (PAK) signaling, metastatic cancer cell proliferation, migration, and mammosphere growth; induces cell-cycle arrest and apoptosis; and decreases HER2-type mammary fatpad tumor growth and metastasis (Humphries-Bickley and colleagues, 2017). Herein, we used nuclear magnetic resonance to show that MBQ-167 directly interacts with Rac1 to displace specific amino acids, and consequently inhibits Rac.GTP loading and viability in TNBC cell lines. Phosphokinome arrays in the MDA-MB-231 human TNBC cells show that phosphorylation status of kinases independent of the Rac/Cdc42/PAK pathway are not significantly changed following 200 nmol/L MBQ-167 treatment. Western blotting shows that initial increases in phospho-c-Jun and phospho-CREB in response to MBQ-167 are not sustained with prolonged exposure, as also confirmed by a decrease in their transcriptional targets. MBQ-167 inhibits tumor growth, and spontaneous and experimental metastasis in immunocompromised (human TNBC) and immunocompetent (mouse TNBC) models. Moreover, per oral administration of MBQ-167 at 100 mg/kg body weight is not toxic to immunocompetent BALB/c mice and has a half-life of 4.6 hours in plasma. These results highlight the specificity, potency, and bioavailability of MBQ-167, and support its clinical potential as a TNBC therapeutic.

Radiographic Correlation of Skeletal Maturation Using the Stages of Dental Calcification in a Peruvian Population.

OBJECTIVE: To identify the correlation between the Baccetti method of SM (skeletal maturation) and the stages of DC (dental calcification) using the Demirjian method in the Orthodontics Service of the Universidad Peruana Cayetano Heredia (UPCH) in Lima-Peru. Materials and Methods. The sample was obtained from panoramic and lateral radiographs of 200 subjects (116 women and 84 men) with ages between 9 and 17 years. Canine, premolar, and molar teeth calcification was evaluated using the Demirjian method while SM was evaluated by the cervical vertebrae with the Baccetti method. Spearman's correlation coefficient was used to assess the relationship between the maturation of these cervical vertebrae and DC. RESULTS: There is a high correlation between the Baccetti method of maturation of the cervical vertebrae and the stages of DC ranging from r = 0.635 to 0.774 for men and from r = 0.677 to 0.784 for women (p < 0.001), the second lower molar being the one with the highest correlation (r = 0.774 in men) and the second lower premolar (r = 0.784 in women). CONCLUSIONS: Stages of DC could be used as a reliable indicator of SM.

Targeting Rac and Cdc42 GEFs in Metastatic Cancer.

The Rho family GTPases Rho, Rac, and Cdc42 have emerged as key players in cancer metastasis, due to their essential roles in regulating cell division and actin cytoskeletal rearrangements; and thus, cell growth, migration/invasion, polarity, and adhesion. This review will focus on the close homologs Rac and Cdc42, which have been established as drivers of metastasis and therapy resistance in multiple cancer types. Rac and Cdc42 are often dysregulated in cancer due to hyperactivation by guanine nucleotide exchange factors (GEFs), belonging to both the diffuse B-cell lymphoma (Dbl) and dedicator of cytokinesis (DOCK) families. Rac/Cdc42 GEFs are activated by a myriad of oncogenic cell surface receptors, such as growth factor receptors, G-protein coupled receptors, cytokine receptors, and integrins; consequently, a number of Rac/Cdc42 GEFs have been implicated in metastatic cancer. Hence, inhibiting GEF-mediated Rac/Cdc42 activation represents a promising strategy for targeted metastatic cancer therapy. Herein, we focus on the role of oncogenic Rac/Cdc42 GEFs and discuss the recent advancements in the development of Rac and Cdc42 GEF-interacting inhibitors as targeted therapy for metastatic cancer, as well as their potential for overcoming cancer therapy resistance.

Antibacterial Effectiveness of Four Concentrations of the Hydroalcoholic Extract of Solanum tuberosum (Tocosh) against Streptococcus mutans ATCC 25175TM: A Comparative In Vitro Study.

OBJECTIVE: To determine the in vitro antibacterial effect of four concentrations of the hydroalcoholic extract of Solanum tuberosum "tocosh" (HET) against Streptococcus mutans ATCC 25175TM. METHODS: This was a prospective, experimental, comparative study. Fermented tocosh was subjected to hydric stress to obtain a hydroalcoholic extract at four different concentrations: 100%, 50%, 75%, and 25%. S. mutans strains were cultured in brain heart infusion agar using the swab technique. The antibacterial effectiveness of HET was evaluated following the Kirby-Bauer disk diffusion method and compared with 0.12% chlorhexidine (positive control group). RESULTS: The highest mean inhibitory effect was achieved with HET at 100% (33.1 ± 2.2 mm, showing a gradual reduction in the other HET groups at 75%, 50%, and 25% (29.7 ± 1.3 mm, 26.6 ± 2.0, and 20.1 ± 1.8 mm, respectively)). Inferential analysis found statistically significant differences among all the experimental groups (p=0.001). The post hoc analysis also showed significant differences among all the experimental groups evaluated; however, there were no significant differences between HET 50% and chlorhexidine 0.12% (p > 0.05). CONCLUSIONS: It was found that the highest antibacterial effectiveness was obtained by HET 100%, being even higher than the 0.12% chlorhexidine positive control, and was statistically significant. Post hoc analysis showed that almost all the concentrations showed optimal efficacy against S. mutans.

P300-Based Brain-Computer Interface Speller: Usability Evaluation of Three Speller Sizes by Severely Motor-Disabled Patients.

Brain-computer interface (BCI) spellers allow severe motor-disabled patients to communicate using their brain activity without muscular mobility. Different visual configurations of the widely studied P300-based BCI speller had been assessed with healthy and motor-disabled users. However, the speller size (in terms of cm) had only been assessed for healthy subjects. We think that the speller size might be limiting for some severely motor-disabled patients with restricted head and eye movements. The usability of three speller sizes was assessed for seven patients diagnosed with amyotrophic lateral sclerosis (ALS) and a participant diagnosed with Duchenne muscular dystrophy (DMD). This is the first usability evaluation of speller size with severely motor-disabled participants. Effectiveness (in the online results) and efficiency (in the workload test) of the medium speller was remarkably better. Satisfaction was significantly the highest with the medium size speller and the lowest with the small size. These results correlate with previously described findings in healthy subjects. In conclusion, the speller size should be considered when designing a speller paradigm, especially for motor-disabled individuals, since it might affect their performance and user experience while controlling a BCI speller.

Effects of Spatial Stimulus Overlap in a Visual P300-based Brain-computer Interface.

The rapid serial visual presentation (RSVP) paradigm seems to be one of the most appropriate for patients using P300-based brain-computer interface (BCI) applications, since non-ocular movements are required. However, according to previous works, the use of different locations for each stimulus may improve performance. Thus, the aim of the present work is to explore how spatial overlap between stimuli influences performance in controlling a visual P300-based BCI. Nineteen participants were tested using four levels of overlap between two stimuli: 100%, 66.7%, 33.3% and 0%. Significant differences in accuracy were found between the 0% overlapped condition and all the other conditions, and between 33.3% and higher overlap (66.7% and 100%). These results can be explained due to a modulation in the non-target stimulus amplitude signal caused by the overlapping factor. In short, the stimulus overlap provokes a modulation in performance using a P300-based BCI; this should be considered in future BCI proposals in which an optimal surface exploitation is convenient and potential users have only residual ocular movement.

Performance Analysis With Different Types of Visual Stimuli in a BCI-Based Speller Under an RSVP Paradigm.

Brain-Computer Interface (BCI) systems enable an alternative communication channel for severely-motor disabled patients to interact with their environment using no muscular movements. In recent years, the importance of research into non-gaze dependent brain-computer interface paradigms has been increasing, in contrast to the most frequently studied BCI-based speller paradigm (i.e., row-column presentation, RCP). Several visual modifications that have already been validated under the RCP paradigm for communication purposes have not been validated under the most extended non-gaze dependent rapid serial visual presentation (RSVP) paradigm. Thus, in the present study, three different sets of stimuli were assessed under RSVP, with the following communication features: white letters (WL), famous faces (FF), neutral pictures (NP). Eleven healthy subjects participated in this experiment, in which the subjects had to go through a calibration phase, an online phase and, finally, a subjective questionnaire completion phase. The results showed that the FF and NP stimuli promoted better performance in the calibration and online phases, being slightly better in the FF paradigm. Regarding the subjective questionnaires, again both FF and NP were preferred by the participants in contrast to the WL stimuli, but this time the NP stimuli scored slightly higher. These findings suggest that the use of FF and NP for RSVP-based spellers could be beneficial to increase information transfer rate in comparison to the most frequently used letter-based stimuli and could represent a promising communication system for individuals with altered ocular-motor function.

Evaluation of emotional and neutral pictures as flashing stimuli using a P300 brain-computer interface speller.

OBJECTIVE: Previous works have reported that complex emotional and visual stimuli can increase the amplitude of the P300 brain potential. Thus, the aim of the present work is to assess these kinds of images in a P300 brain-computer interface (BCI) speller as flashing stimuli. APPROACH: Twenty-three volunteers controlled four spellers with different sets of flashing stimuli: flashing letters, neutral pictures (NP), emotional pleasant pictures (EPP) and emotional unpleasant pictures (EUP). MAIN RESULTS: The sets of pictures showed a higher performance than the letters in accuracy and information transfer rate. These results were supported by the analysis of the P300 signal, where the picture sets offered the greatest amplitudes. The NP and EPP sets were the best evaluated in the subjective questionnaire. SIGNIFICANCE: In short, despite the fact that the effect of emotional stimuli could not be observed in the performance metrics, picture sets have offered a high performance and should be considered in future proposals for visual P300-based BCI applications.