Face processing and early event-related potentials: replications and novel findings.

This research explores early Event-Related Potentials (ERPs) sensitivity to facial stimuli, investigating various facial features aimed to unveil underlying neural mechanisms. Two experiments, each involving 15 undergraduate students, utilized a multidimensional stimulus set incorporating race, gender, age, emotional expression, face masks, and stimulus orientation. Findings highlight significant modulations in N170 and P200 amplitudes and latencies for specific attributes, replicating prior research and revealing novel insights. Notably, age-related facial feature variations, facial inversion, and the presence of face masks significantly impact neural responses. Several speculative explanations are proposed to elucidate these results: First, the findings lend support to the idea that the increased N170 amplitude observed with facial inversion is closely tied to the activation of object-sensitive neurons. This is further bolstered by a similar amplitude increase noted when masks (effective objects) are added to faces. Second, the absence of an additional amplitude increase, when inverting face images with face masks suggests that neural populations may have reached a saturation point, limiting further enhancement. Third, the study reveals that the latency deficit in N170 induced by facial inversion is even more pronounced in the subsequent ERP component, the P200, indicating that face inversion may impact multiple stages of face processing. Lastly, the significant increase in P200 amplitude, typically associated with face typicality, for masked faces in this study aligns with previous research that demonstrated elevated P200 amplitudes for scrambled faces. This suggests that obscured faces may be processed as typical, potentially representing a default state in face processing.

Trust in the police and affective evaluation of police faces: a preliminary study.

Introduction: A study was conducted to investigate if an individual's trust in law enforcement affects their perception of the emotional facial expressions displayed by police officers. Methods: The study invited 77 participants to rate the valence of 360 face images. Images featured individuals without headgear (condition 1), or with a baseball cap (condition 2) or police hat (condition 3) digitally added to the original photograph. The images were balanced across sex, race/ethnicity (Asian, African American, Latine, and Caucasian), and facial expression (Happy, Neutral, and Angry). After rating the facial expressions, respondents completed a survey about their attitudes toward the police. Results: The results showed that, on average, valence ratings for "Angry" faces were similar across all experimental conditions. However, a closer examination revealed that faces with police hats were perceived as angrier compared to the control conditions (those with no hat and those with a baseball cap) by individuals who held negative views of the police. Conversely, participants with positive attitudes toward the police perceived faces with police hats as less angry compared to the control condition. This correlation was highly significant for angry faces (p < 0.01), and stronger in response to male faces compared to female faces but was not significant for neutral or happy faces. Discussion: The study emphasizes the substantial role of attitudes in shaping social perception, particularly within the context of law enforcement.

Affective evaluation of consciously perceived emotional faces reveals a "correct attribution effect".

The strength of the affective priming effect is influenced by various factors, including the duration of the prime. Surprisingly, short-duration primes that are around the threshold for conscious awareness typically result in stronger effects compared to long-duration primes. The misattribution effect theory suggest that subliminal primes do not provide sufficient cognitive processing time for the affective feeling to be attributed to the prime. Instead, the neutral target being evaluated is credited for the affective experience. In everyday social interactions, we shift our gaze from one face to another, typically contemplating each face for only a few seconds. It is reasonable to assume that no affective priming takes place during such interactions. To investigate whether this is indeed the case, participants were asked to rate the valence of faces displayed one by one. Each face image simultaneously served as both a target (primed by the previous trial) and a prime (for the next trial). Depending on the participant's response time, images were typically displayed for about 1-2 s. As predicted by the misattribution effect theory, neutral targets were not affected by positive affective priming. However, non-neutral targets showed a robust priming effect, with emotional faces being perceived as even more negative or positive when the previously seen face was emotionally congruent. These results suggest that a "correct attribution effect" modulates how we perceive faces, continuously impacting our social interactions. Given the importance of faces in social communication, these findings have wide-ranging implications.

Scientific contributions of citizen science applied to rare or threatened animals.

Citizen science is filling important monitoring gaps and thus contributing to the conservation of rare or threatened animals. However, most researchers have used peer-reviewed publications to evaluate citizen science contributions. We quantified a larger spectrum of citizen science's contributions to the monitoring of rare or threatened animals, including contributions to the peer-reviewed publications, gray literature and to conservation measures (i.e., actions taken as a direct result of citizen science monitoring). We sought to provide broad information on how results of studies of citizen science monitoring is used. We also evaluated factors associated with success of citizen science projects. We conducted a web search to find citizen science projects focusing on rare and threatened species and surveyed citizen science project managers about their contributions and factors influencing their success. The number of projects increased rapidly after 2010. Almost one-half of the citizen science projects produced at least 1 peer-reviewed publication, 64% produced at least 1 gray literature publication, and 64% resulted in at least 1 conservation measure. Conservation measures covered a wide range of actions, including management and mitigation plans, modification of threat status, identification and establishment of protected areas, habitat restoration, control of invasive species, captive breeding programs, and awareness campaigns. Longevity, data quality, and collaboration type best explained quantities of all types of scientific contributions of citizen science. We found that citizen science contributed substantially to knowledge advancement and conservation, especially when programs were long term and had rigorous data collection and management standards, and multidisciplinary or transdisciplinary collaborations.

La ciencia ciudadana contribuye a llenar vacíos en el monitoreo, lo que ayuda a la conservación de animales raros o amenazados. Sin embargo, la mayoría de los investigadores han usado publicaciones revisadas por pares para evaluar las contribuciones de la ciencia ciudadana. Cuantificamos un mayor espectro de las contribuciones de la ciencia ciudadana al monitoreo de animales raros y amenazados, incluyendo las contribuciones a la literatura gris, a las publicaciones revisada por pares y a las medidas de conservación (es decir, las acciones tomadas como resultado directo del monitoreo ciudadano). Buscamos proporcionar información generalizada sobre cómo los resultados de los estudios de monitoreo ciudadano es usado. También evaluamos los factores asociados con el éxito de los proyectos de ciencia ciudadana. Realizamos una búsqueda en línea para encontrar proyectos de ciencia ciudadana enfocados en especies raras o amenazadas y encuestamos a los gestores de estos proyectos sobre sus contribuciones y los factores que influyen sobre su éxito. El número de proyectos incrementó rápidamente a partir de 2010. De los proyectos de ciencia ciudadana, casi la mitad produjo al menos 1 publicación revisada por pares, el 64% produjo al menos una publicación en la literatura gris y el 64% derivó en al menos 1 medida de conservación. Las medidas de conservación abarcaron una gama extensa de acciones que incluyeron planes de gestión y mitigación, modificación del estado de amenaza, identificación y establecimiento de áreas protegidas, restauración del hábitat, control de especies invasoras, programas de reproducción en cautiverio y campañas de concientización. La longevidad, calidad de los datos y el tipo de colaboración explicaron de mejor manera las cantidades de todos los tipos de contribuciones científicas hechas por la ciencia ciudadana. Descubrimos que la ciencia ciudadana contribuyó sustancialmente al avance del conocimiento y la conservación, especialmente cuando los programas eran a largo plazo y contaban con estándares rigurosos de recolección y gestión de datos, y con colaboraciones multi o transdisciplinarias.

In Vitro Technology in Plant Conservation: Relevance to Biocultural Diversity.

Plant diversity is critical to the functioning of human societies, and evidence shows that plant conservation success is driven by integrative approaches that include social and biological factors. Plants have a unique capacity to reproduce asexually, and propagation practices can yield large numbers of plantlets. These plantlets can be used in several ways to fulfil conservation goals including the repopulation of regions with declining densities of threatened species that hold cultural meaning. However, the potential of in vitro technologies in the conservation of plants that hold cultural meaning is understudied. In this paper we focus upon the roles of in vitro technologies in the conservation of plants relevant to biocultural environments and provide an overview of potential knowledge gaps at the interface of in vitro and plants used traditionally, including those meaningful to Indigenous Peoples. We conclude that in vitro technologies can be powerful tools in biocultural conservation if they are deployed in a manner respectful of the socio-cultural context in which plants play a role, but that further research is needed in this regard. We suggest several epistemological points to facilitate future research.

Having Difficulties Reading the Facial Expression of Older Individuals? Blame It on the Facial Muscles, Not the Wrinkles.

Previous studies have found it is more difficult identifying an emotional expression displayed by an older than a younger face. It is unknown whether this is caused by age-related changes such as wrinkles and folds interfering with perception, or by the aging of facial muscles, potentially reducing the ability of older individuals to display an interpretable expression. To discriminate between these two possibilities, participants attempted to identify facial expressions under different conditions. To control for the variables (wrinkles/folds vs facial muscles), we used Generative Adversarial Networks to make faces look older or younger. Based upon behavior data collected from 28 individuals, our model predicts that the odds of correctly identifying the expressed emotion of a face reduced 16.2% when younger faces (condition 1) are artificially aged (condition 3). Replacing the younger faces with natural old-looking faces (Condition 2), however, results in an even stronger effect (odds of correct identification decreased by 50.9%). Counterintuitively, making old faces (Condition 2) look young (Condition 4) results in the largest negative effect (odds of correct identification decreased by 74.8% compared with natural young faces). Taken together, these results suggest that both age-related decline in the facial muscles' ability to express facial emotions and age-related physical changes in the face, explain why it is difficult to recognize facial expressions from older faces; the effect of the former, however, is much stronger than that of the latter. Facial muscle exercises, therefore, might improve the capacity to convey facial emotional expressions in the elderly.

Indigenous guardians as an emerging approach to indigenous environmental governance.

Over the past 3 decades, indigenous guardian programs (also known as indigenous rangers or watchmen) have emerged as an institution for indigenous governments to engage in collaborative environmental governance. Using a systematic review of peer-reviewed literature for research conducted in Australia, Canada, Aotearoa-New Zealand, and the United States, we sought to characterize the emergence of indigenous guardians in the literature and explore whether guardian approaches are representative of Indigenous approaches to environmental governance. Using a multistep relevance-screening method, we reviewed 83 articles published since 1995, that report on, critique, or comment on Indigenous guardians. Our findings indicated that most articles on the topic were published in the last decade (88%), focused on Australia (65%), and were in a social science discipline (53%). The lead author of the majority of articles was an academic, although only half of the articles included an indigenous scholar or member of an indigenous group or organization as a coauthor. Finally, 11 articles were on research of guardian programs that were locally led and only 5 exemplified indigenous governance, based on 2 well-known community-based monitoring typologies. Our findings indicate that more research is required to understand the implications of current guardian programs for indigenous self-determination, particularly when such programs are embedded in a broader western environmental governance structure.

Guardianes Indígenas como una Estrategia Emergente para la Administración Ambiental Indígena Resumen Durante las tres décadas más recientes, los programas de guardianes indígenas (también conocidos como guardias o vigilantes indígenas) han emergido como una institución para que las administraciones indígenas participen en la administración ambiental colaborativa. Mediante una revisión sistemática de la literatura revisada por pares de proyectos de investigación realizados en Australia, Canadá, Aotearoa-Nueva Zelanda y en los Estados Unidos buscamos caracterizar el surgimiento de los guardianes indígenas en la literatura y exploramos si las estrategias de guardianes son representativas de las estrategias indígenas para la administración ambiental. Usamos un método de filtración de relevancia con pasos múltiples para revisar 83 artículos publicados desde 1995; estos artículos reportan, critican o comentan sobre los guardianes indígenas. Nuestros hallazgos indicaron que la mayoría de los artículos dedicados a este tema fue publicada en la última década (88%), está enfocada en Australia (65%) y está dedicada a una disciplina de las ciencias sociales (53%). El autor principal de la mayoría de los artículos fue un académico, aunque sólo la mitad de los artículos incluía a un investigador indígena o a un miembro de un grupo u organización indígena como coautor. Finalmente, once artículos investigaron los programas de guardianes liderados localmente y solamente cinco artículos ejemplifican la administración indígena con base en dos tipologías populares de monitoreo basadas en la comunidad. Nuestros hallazgos indican que se requiere una mayor investigación para entender las implicaciones de los programas de guardianes para la autodeterminación indígena, particularmente cuando dichos programas están arraigados en una estructura de administración ambiental occidental más generalizada.

Intencionalidad del embarazo y cuidados prenatales en Uruguay / Pregnancy intention and antenatal care services in Uruguay / Intencionalidade da gravidez e cuidado pré-natal no Uruguai

Resumen: Introducción: desde hace algunos años el número de embarazos no intencionales en Uruguay ronda el 40%; esta cifra es alta en comparación con otros países que también tienen baja fecundidad y da cuenta de las dificultades de acceso y uso eficaz de métodos anticonceptivos modernos. Además, varios estudios evidencian que los embarazos no intencionales están vinculados con cuidados prenatales insuficientes y peores desempeños de los recién nacidos respecto a los nacimientos resultantes de embarazos intencionales. Objetivo: analizar la asociación entre intencionalidad de los embarazos y los cuidados prenatales en Uruguay a partir del estudio de su incidencia sobre la captación temprana del embarazo y las prácticas no saludables durante la gestación (fumar y tomar alcohol). Método: se consideran los nacimientos no intencionales y a destiempo (no buscados en ese momento) como dos grupos de tratamiento y se comparan con el grupo de nacimientos intencionales. Se examina el efecto neto de la intencionalidad del embarazo sobre las prácticas de salud durante la gestación utilizando técnicas de Propensity Score Matching (PSM). Se utilizan datos provenientes de la Encuesta de Nutrición, Desarrollo Infantil y Salud (ENDIS), un estudio de panel que recoge información desde 2013 de madres con hijos de entre 0 y 3 años en hogares ubicados en localidades urbanas de Uruguay (mayores a 5.000 habitantes). Resultados: antes de realizar el emparejamiento por PSM, las diferencias entre grupos de intención de embarazos fueron significativas para captación temprana y haber fumado, mientras que haber bebido alcohol no se asoció a diferencias significativas entre grupos de intención de los embarazos.

Summary: Introduction: in Uruguay, the number of unintended pregnancies has been around 40% for several years. This is rather a high percentage if compared to other countries who also have low fertility rates and evidences difficulties in access to modern contraceptive methods or using them effectively. Likewise, several studies evidence unintended pregnancies are related to insufficient antenatal care services and worse outcome in the new-borns when compared to births resulting from intentional pregnancies. Objective: to study the relationship between pregnancy intentionality and antenatal care services in Uruguay, based on an analysis of its impact on the early engagement of pregnancies and non-healthy practices during pregnancy (smoking and alcohol consumption). Method: unintended and untimely births (not sought at that time) were included in the study as two treatment groups, and they are compared to the group of intentional births. The net effect of pregnancy intention on health practices during pregnancy was examined using the de Propensity Score Matching (PSM) techniques. We used data delivered by the Nutrition, Child Development and Health Survey, a panel study that has been collecting information from mothers of children between 0 and 3 years old who live in urban localities of Uruguay (with over 5,000 inhabitants) since 2013. Results: Prior to the PSM matching, the differences in early engagement and smoking were significant between pregnancy intention groups, whereas alcohol consumption was not associated to significant differences between pregnancy intention groups.

Resumo: Introdução: há anos, o número de gestações não intencionais no Uruguai gira em torno de 40%; este número é alto em comparação com outros países que também têm baixa fecundidade e explica as dificuldades de acesso e uso de métodos anticoncepcionais modernos. Além disso, diversos estudos mostram que a gravidez não intencional está associada ao pré-natal insuficiente e piores parâmetros do recém-nascido em comparação com o nascimento decorrente da gravidez intencional. Objetivos: analisar a associação entre intencionalidade da gravidez e assistência pré-natal no Uruguai, a partir do estudo de sua incidência na detecção precoce da gravidez e práticas não saudáveis durante a gravidez (tabagismo e etilismo). Método: os nascimentos não intencionais e prematuros (não desejados no momento) são considerados dois grupos de tratamento e comparados com o grupo de partos intencionais. O efeito líquido da intencionalidade da gravidez sobre as práticas de saúde durante a gravidez é examinado usando técnicas de correspondência de pontuação de propensão (PSM). São utilizados os dados da Pesquisa de Nutrição, Desenvolvimento Infantil e Saúde (ENDIS), um estudo de painel que coleta informações desde 2013 de mães com filhos de 0 a 3 anos em domicílios localizados em áreas urbanas do Uruguai (mais de 5.000 habitantes). Resultados: antes de realizar a comparação por PSM, as diferenças entre os grupos de intenção de gravidez foram significativas para recrutamento precoce e tabagismo, enquanto ter bebido álcool não foi associado a diferenças significativas entre os grupos de intenção de gravidez.

Do Glasses Modulate Age Perception?

No formal studies have reported how glasses influence age perception, except for a London Vision Clinic survey that found that people over 45 look 5 or more years older when wearing eyeglasses. To investigate the effect of eyeglasses and sunglasses on age perception while controlling for age and interpersonal differences, we digitally manipulated the photographs of faces of 50 young adults, to create two age conditions (young and old) and three eyewear conditions (no glasses, eyeglasses, and sunglasses). Participants then estimated the age of the faces, displayed in random order. Contrary to the generally accepted beliefs that wearing eyeglasses makes you look older and wearing sunglasses make you look younger, our results suggest that the effect of glasses on age perception is rather small.

Familiarity with visual stimuli boosts recency bias in macaques.

To probe how non-human primates (NHPs) decode temporal dynamic stimuli, we used a two-alternative forced choice task (2AFC), where the cue was dynamic: a movie snippet drawn from an animation that transforms one image into another. When the cue was drawn from either the beginning or end of the animation, thus heavily weighted towards one (the target) of both images (the choice pair), then primates performed at high levels of accuracy. For a subset of trials, however, the cue was ambiguous, drawn from the middle of the animation, containing information that could be associated to either image. Those trials, rewarded randomly and independent of choice, offered an opportunity to study the strategy the animals used trying to decode the cue. Despite being ambiguous, the primates exhibited a clear strategy, suggesting they were not aware that reward was given non-differentially. More specifically, they relied more on information provided at the end than at the beginning of those cues, consistent with the recency effect reported by numerous serial position studies. Interestingly and counterintuitively, this effect became stronger for sessions where the primates were already familiar with the stimuli. In other words, despite having rehearsed with the same stimuli in a previous session, the animals relied even more on a decision strategy that did not yield any benefits during a previous session. In the discussion section we speculate on what might cause this behavioral shift towards stronger bias, as well as why this behavior shows similarities with a repetition bias in humans known as the illusory truth effect.

Human visual cortical gamma reflects natural image structure.

Many studies have reported visual cortical gamma-band activity related to stimulus processing and cognition. Most respective studies used artificial stimuli, and the few studies that used natural stimuli disagree. Electrocorticographic (ECoG) recordings from awake macaque areas V1 and V4 found gamma to be abundant during free viewing of natural images. In contrast, a study using ECoG recordings from V1 of human patients reported that many natural images induce no gamma and concluded that it is not necessary for seeing. To reconcile these apparently disparate findings, we reanalyzed those same human ECoG data recorded during presentation of natural images. We find that the strength of gamma is positively correlated with different image-computable metrics of image structure. This holds independently of the precise metric used to quantify gamma. In fact, an average of previously used gamma metrics reflects image structure most robustly. Gamma was sufficiently diagnostic of image structure to differentiate between any possible pair of images with >70% accuracy. Thus, while gamma might be weak for some natural images, the graded strength of gamma reflects the graded degree of image structure, and thereby conveys functionally relevant stimulus properties.

The role of digital data entry in participatory environmental monitoring.

Many argue that monitoring conducted exclusively by scientists is insufficient to address ongoing environmental challenges. One solution entails the use of mobile digital devices in participatory monitoring (PM) programs. But how digital data entry affects programs with varying levels of stakeholder participation, from nonscientists collecting field data to nonscientists administering every step of a monitoring program, remains unclear. We reviewed the successes, in terms of management interventions and sustainability, of 107 monitoring programs described in the literature (hereafter programs) and compared these with case studies from our PM experiences in Australia, Canada, Ethiopia, Ghana, Greenland, and Vietnam (hereafter cases). Our literature review showed that participatory programs were less likely to use digital devices, and 2 of our 3 more participatory cases were also slow to adopt digital data entry. Programs that were participatory and used digital devices were more likely to report management actions, which was consistent with cases in Ethiopia, Greenland, and Australia. Programs engaging volunteers were more frequently reported as ongoing, but those involving digital data entry were less often sustained when data collectors were volunteers. For the Vietnamese and Canadian cases, sustainability was undermined by a mismatch in stakeholder objectives. In the Ghanaian case, complex field protocols diminished monitoring sustainability. Innovative technologies attract interest, but the foundation of effective participatory adaptive monitoring depends more on collaboratively defined questions, objectives, conceptual models, and monitoring approaches. When this foundation is built through effective partnerships, digital data entry can enable the collection of more data of higher quality. Without this foundation, or when implemented ineffectively or unnecessarily, digital data entry can be an additional expense that distracts from core monitoring objectives and undermines project sustainability. The appropriate role of digital data entry in PM likely depends more on the context in which it is used and less on the technology itself.

Visual cortical gamma-band activity during free viewing of natural images.

Gamma-band activity in visual cortex has been implicated in several cognitive operations, like perceptual grouping and attentional selection. So far, it has been studied primarily under well-controlled visual fixation conditions and using well-controlled stimuli, like isolated bars or patches of grating. If gamma-band activity is to subserve its purported functions outside of the laboratory, it should be present during natural viewing conditions. We recorded neuronal activity with a 252-channel electrocorticographic (ECoG) grid covering large parts of the left hemisphere of 2 macaque monkeys, while they freely viewed natural images. We found that natural viewing led to pronounced gamma-band activity in the visual cortex. In area V1, gamma-band activity during natural viewing showed a clear spectral peak indicative of oscillatory activity between 50 and 80 Hz and was highly significant for each of 65 natural images. Across the ECoG grid, gamma-band activity during natural viewing was present over most of the recorded visual cortex and absent over most remaining cortex. After saccades, the gamma peak frequency slid down to 30-40 Hz at around 80 ms postsaccade, after which the sustained 50- to 80-Hz gamma-band activity resumed. We propose that gamma-band activity plays an important role during natural viewing.

Dynamic encoding of face information in the human fusiform gyrus.

Humans' ability to rapidly and accurately detect, identify and classify faces under variable conditions derives from a network of brain regions highly tuned to face information. The fusiform face area (FFA) is thought to be a computational hub for face processing; however, temporal dynamics of face information processing in FFA remains unclear. Here we use multivariate pattern classification to decode the temporal dynamics of expression-invariant face information processing using electrodes placed directly on FFA in humans. Early FFA activity (50-75 ms) contained information regarding whether participants were viewing a face. Activity between 200 and 500 ms contained expression-invariant information about which of 70 faces participants were viewing along with the individual differences in facial features and their configurations. Long-lasting (500+ms) broadband gamma frequency activity predicted task performance. These results elucidate the dynamic computational role FFA plays in multiple face processing stages and indicate what information is used in performing these visual analyses.

Gamma or no gamma, that is the question.

Numerous studies suggest that gamma-band synchronization is central to visual processing, yet most of them have used artificial stimuli. A new study using electrocorticography (ECoG) in humans reported finding no gamma for many natural images and for visual noise. However, we highlight that sensitive metrics can reveal clear gamma not only for natural images, but for noise stimuli and even during the absence of visual stimuli. This shows the importance of using appropriate metrics for detecting rhythmic synchronization and investigating the function of gamma during natural viewing.

Stimulus repetition modulates gamma-band synchronization in primate visual cortex.

When a sensory stimulus repeats, neuronal firing rate and functional MRI blood oxygen level-dependent responses typically decline, yet perception and behavioral performance either stay constant or improve. An additional aspect of neuronal activity is neuronal synchronization, which can enhance the impact of neurons onto their postsynaptic targets independent of neuronal firing rates. We show that stimulus repetition leads to profound changes of neuronal gamma-band (∼40-90 Hz) synchronization. Electrocorticographic recordings in two awake macaque monkeys demonstrated that repeated presentations of a visual grating stimulus resulted in a steady increase of visually induced gamma-band activity in area V1, gamma-band synchronization between areas V1 and V4, and gamma-band activity in area V4. Microelectrode recordings in area V4 of two additional monkeys under the same stimulation conditions allowed a direct comparison of firing rates and gamma-band synchronization strengths for multiunit activity (MUA), as well as for isolated single units, sorted into putative pyramidal cells and putative interneurons. MUA and putative interneurons showed repetition-related decreases in firing rate, yet increases in gamma-band synchronization. Putative pyramidal cells showed no repetition-related firing rate change, but a decrease in gamma-band synchronization for weakly stimulus-driven units and constant gamma-band synchronization for strongly driven units. We propose that the repetition-related changes in gamma-band synchronization maintain the interareal stimulus signaling and sharpen the stimulus representation by gamma-synchronized pyramidal cell spikes.

Ca(2+)-regulatory function of the inhibitory peptide region of cardiac troponin I is aided by the C-terminus of cardiac troponin T: Effects of familial hypertrophic cardiomyopathy mutations cTnI R145G and cTnT R278C, alone and in combination, on filament sliding.

Investigations of cardiomyopathy mutations in Ca(2+) regulatory proteins troponin and tropomyosin provide crucial information about cardiac disease mechanisms, and also provide insights into functional domains in the affected polypeptides. Hypertrophic cardiomyopathy-associated mutations TnI R145G, located within the inhibitory peptide (Ip) of human cardiac troponin I (hcTnI), and TnT R278C, located immediately C-terminal to the IT arm in human cardiac troponin T (hcTnT), share some remarkable features: structurally, biochemically, and pathologically. Using bioinformatics, we find compelling evidence that TnI and TnT, and more specifically the affected regions of hcTnI and hcTnT, may be related not just structurally but also evolutionarily. To test for functional interactions of these mutations on Ca(2+)-regulation, we generated and characterized Tn complexes containing either mutation alone, or both mutations simultaneously. The most important results from in vitro motility assays (varying [Ca(2+)], temperature or HMM density) show that the TnT mutant "rescued" some deleterious effects of the TnI mutant at high Ca(2+), but exacerbated the loss of function, i.e., switching off the actomyosin interaction, at low Ca(2+). Taken together, our experimental results suggest that the C-terminus of cTnT aids Ca(2+)-regulatory function of cTnI Ip within the troponin complex.