Browsing by Author "Soares, Sandra Cristina de Oliveira"
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- Adaptive memory: The mnemonic value of contaminationPublication . Fernandes, Natália Lisandra; Pandeirada, Josefa N. S.; Soares, Sandra Cristina de Oliveira; Nairne, James S.Humans likely evolved an adaptive disease avoidance system, the Behavioral Immune System, to mitigate the fitness costs posed by pathogens. This system is specially attuned to cues connoting infection risk:When perceived, these cues drive affective, cognitive, and behavioral responses, which work in an articulated way to enhance the organism's chances of survival. The current work investigated the cognitive aspect of this system, specifically if human memory preferentially retains potentially contaminated items. Participants were shown pictures of objects that were touched by sick or healthy people. Each object was linked to verbal descriptions (Experiment 1a and 1b) or visual cues (faces; Experiment 2 and 3) about the person initiating the contact. During encoding participants were required to decide whether each object had been touched by a sick or a healthy person. Then, after a short distractor task, a surprise free recall task for the objects was given. In all experiments, objects touched by sick people were remembered better than those touched by healthy people. This mnemonic advantage was obtained using the same procedure in two different countries suggesting its robustness. Finally, it seems not to rely on the visual cues accompanying the objects, but rather onwhether the context presented establishes a real opportunity for contamination. These results suggest that memory might play a key role in the Behavioral Immune System.
- An automatic classifier of emotions built from entropy of noisePublication . Ferreira, Jacqueline; Brás, Susana; Silva, Carlos Fernandes da; Soares, Sandra Cristina de OliveiraThe electrocardiogram (ECG) signal has been widely used to study the physiological substrates of emotion. However, searching for better filtering techniques in order to obtain a signal with better quality and with the maximum relevant information remains an important issue for researchers in this field. Signal processing is largely performed for ECG analysis and interpretation, but this process can be susceptible to error in the delineation phase. In addition, it can lead to the loss of important information that is usually considered as noise and, consequently, discarded from the analysis. The goal of this study was to evaluate if the ECG noise allows for the classification of emotions, while using its entropy as an input in a decision tree classifier. We collected the ECG signal from 25 healthy participants while they were presented with videos eliciting negative (fear and disgust) and neutral emotions. The results indicated that the neutral condition showed a perfect identification (100%), whereas the classification of negative emotions indicated good identification performances (60% of sensitivity and 80% of specificity). These results suggest that the entropy of noise contains relevant information that can be useful to improve the analysis of the physiological correlates of emotion.
- Beware the serpent: The advantage of ecologically-relevant stimuli in accessing visual awarenessPublication . Gomes, Nuno; Silva, Samuel; Silva, Carlos Fernandes da; Soares, Sandra Cristina de OliveiraSnakes and spiders constitute fear-relevant stimuli for humans, as many species have deleterious and even fatal effects. However, snakes provoked an older and thus stronger evolutionary pressure than spiders, shaping the vision of earliest primates toward preferential visual processing, mainly in the most complex perceptual conditions. To the best of our knowledge, no study has yet directly assessed the role of ecologically-relevant stimuli in preferentially accessing visual awareness. Using continuous flash suppression (CFS), the present study assessed the role of evolutionary pressure in gaining a preferential access to visual awareness. For this purpose, we measured the time needed for three types of stimuli - snakes, spiders (matched with snakes for rated fear levels, but for which an influence on humans but not other primates is well grounded) and birds - to break the suppression and enter visual awareness in two different suppression intensity conditions. The results showed that in the less demanding awareness access condition (stimuli presented to the participants' dominant eye) both evolutionarily relevant stimuli (snakes and spiders) showed a faster entry into visual awareness than birds, whereas in the most demanding awareness access condition (stimuli presented to the participants' non-dominant eye) only snakes showed this privileged access. Our data suggest that the privileged unconscious processing of snakes in the most complex perceptual conditions extends to visual awareness, corroborating the proposed influence of snakes in primate visual evolution.
- Emotional body odors as context: Effects on cardiac and subjective responsesPublication . Ferreira, Jacqueline; Parma, Valentina; Alho, Laura; Silva, Carlos Fernandes da; Soares, Sandra Cristina de OliveiraMany studies have indicated that the chemical cues from body odors (BOs) of donors experiencing negative emotions can influence the psychophysiological and behavioral response of the observers. However, these olfactory cues have been used mainly as contextual information for processing visual stimuli. Here, for the first time, we evaluate how emotional BO affects the emotional tone of a subsequent BO message. Axillary sweat samples were taken from 20 donors in 3 separate sessions while they watched fear, disgust, or neutral videos. In a double-blind experiment, we assessed the cardiac and subjective responses from 69 participants who were either exposed to negative emotional or neutral BOs. Our results showed a reduced cardiac parasympathetic activity (HF%)-indicating increased stress-when participants smelled the emotional BOs before the neutral BOs, compared to when they smelled neutral followed by emotional BOs. The intensity of the neutral odor also increased following the exposure to both negative BOs. These findings indicate that BOs contain an emotion-dependent chemical cue that affects the perceiver both at the physiological and subjective levels.
- Exogenous attention to fear: Differential behavioral and neural responses to snakes and spidersPublication . Soares, Sandra Cristina de Oliveira; Kessel, Dominique; Lorca, María Hernández; Rubio, María J. García; Rodrigues, Paulo; Gomes, Nuno; Carretié, LuisResearch has consistently shown that threat stimuli automatically attract attention in order to activate the defensive response systems. Recent findings have provided evidence that snakes tuned the visual system of evolving primates for their astute detection, particularly under challenging perceptual conditions. The goal of the present study was to measure behavioral and electrophysiological indices of exogenous attention to snakes, compared with spiders - matched for rated fear levels but for which sources of natural selection are less well grounded, and to innocuous animals (birds), which were presented as distracters, while participants were engaged in a letter discrimination task. Duration of stimuli, consisting in a letter string and a concurrent distracter, was either presented for 180 or 360ms to explore if the stimulus duration was a modulating effect of snakes in capturing attention. Results showed a specific early (P1) exogenous attention-related brain potential with maximal amplitude to snakes in both durations, which was followed by an enhanced late attention-related potential (LPP) showing enhanced amplitudes to spiders, particularly under the longer exposure durations. These results suggest that exogenous attention to different classes of threat stimuli follows a gradual process, with the most evolutionary-driven stimulus, i.e., snakes, being more efficient at attracting early exogenous attention, thus more dependent on bottom-up processes.
- Fast detector/ first responder: Interactions between the superior colliculus-pulvinar pathway and stimuli relevant to primatesPublication . Soares, Sandra Cristina de Oliveira; Maior, Rafael S.; Isbell, Lynne A.; Tomaz, Carlos; Nishijo, HisaoPrimates are distinguished from other mammals by their heavy reliance on the visual sense, which occurred as a result of natural selection continually favoring those individuals whose visual systems were more responsive to challenges in the natural world. Here we describe two independent but also interrelated visual systems, one cortical and the other subcortical, both of which have been modified and expanded in primates for different functions. Available evidence suggests that while the cortical visual system mainly functions to give primates the ability to assess and adjust to fluid social and ecological environments, the subcortical visual system appears to function as a rapid detector and first responder when time is of the essence, i.e., when survival requires very quick action. We focus here on the subcortical visual system with a review of behavioral and neurophysiological evidence that demonstrates its sensitivity to particular, often emotionally charged, ecological and social stimuli, i.e., snakes and fearful and aggressive facial expressions in conspecifics. We also review the literature on subcortical involvement during another, less emotional, situation that requires rapid detection and response-visually guided reaching and grasping during locomotion-to further emphasize our argument that the subcortical visual system evolved as a rapid detector/first responder, a function that remains in place today. Finally, we argue that investigating deficits in this subcortical system may provide greater understanding of Parkinson's disease and Autism Spectrum disorders (ASD).
- Influence of body odors and gender on perceived genital arousalPublication . Oliveira, Patrícia Alves; Carvalho, Joana; Ferreira, Jacqueline; Alho, Laura; Nobre, Pedro; Olsson, Mats J.; Soares, Sandra Cristina de OliveiraOlfaction is often linked to mating behavior in nonhumans. Additionally, studies in mating behavior have shown that women seem to be more affected by odor cues than men. However, the relationship between odor cues and sexual response-specifically, sexual arousal-has not been studied yet. The aim of this study was to evaluate the impact of the exposure to human body odors (from individuals of the opposite gender) on perceived genital arousal, while these were presented concomitantly to sexually explicit video clips. Eighty university students (40 women) rated their perceived genital arousal (perceived degree of erection/genital lubrication) in response to an audiovisual sexual stimulus, while simultaneously exposed to a body odor from an opposite-gender donor or no odor. Participants also rated each odor sample's (body odor and no odor) perceived pleasantness, intensity, and familiarity. Findings indicated that odor condition had an effect on women's (but not men's) perceived genital arousal, with women showing higher levels of perceived genital arousal in the no odor condition. Also, results showed that women rated body odors as less pleasant than no odor. Notwithstanding, the odor ratings do not seem to explain the association between body odor and perceived genital arousal. The current results support the hypothesis that women, rather than men, are sensitive to odors in the context of sexual response. The findings of this study have relevance for the understanding of human sexuality with respect to chemosensory communication.
- The effects of emotional visual context on the encoding and retrieval of body odor informationPublication . Parma, Valentina; Macedo, Stephanie; Rocha, Marta; Alho, Laura; Ferreira, Jacqueline; Soares, Sandra Cristina de OliveiraConditions during information encoding and retrieval are known to influence the sensory material stored and its recapitulation. However, little is known about such processes in olfaction. Here, we capitalized on the uniqueness of body odors (BOs) which, similar to fingerprints, allow for the identification of a specific person, by associating their presentation to a negative or a neutral emotional context. One hundred twenty-five receivers (68 F) were exposed to a male BO while watching either criminal or neutral videos (encoding phase) and were subsequently asked to recognize the target BO within either a congruent or an incongruent visual context (retrieval phase). The results showed that criminal videos were rated as more vivid, unpleasant, and arousing than neutral videos both at encoding and retrieval. Moreover, in terms of BO ratings, we found that odor intensity and arousal allow to distinguish the target from the foils when congruent criminal information is presented at encoding and retrieval. Finally, the accuracy performance was not significantly different from chance level for either condition. These findings provide insights on how olfactory memories are processed in emotional situations.
- Unconscious influence over executive control: Absence of conflict detection and adaptationPublication . Silva, Fábio; Dias, Joana; Silva, Samuel; Bem-Haja, Pedro; Silva, Carlos Fernandes da; Soares, Sandra Cristina de OliveiraExecutive control and its modulation of attentional mechanisms allow us to detect and adapt to conflicting information. According to recent studies, executive control functions may be modulated by unconsciously perceived information, although the available evidence is not consistent. In this study, we used a Flanker Task and employed Chromatic Flicker Fusion, a suppression technique that has been proposed as more adequate to elicit executive control functions, to assess conflict and conflict adaptation effects. Our results showed that, when suppressed, flankers did not evoke conflict related effects on performance. However, in trials where most flankers were incongruent, longer response times in congruent trials were observed, consistent with orienting responses. Our results help to support earlier theories regarding the inherent limitations of unconsciously perceived information, though future studies should further investigate why and under which conditions is the executive control system modulated by unconscious information.