Emotional attention as a modulatory system of perception

Report for the scientific sojourn carried out at the University Medical Center, Swiss, from 2010 to 2012. Abundant evidence suggests that negative emotional stimuli are prioritized in the perceptual systems, eliciting enhanced neural responses in early sensory regions as compared with neutral information. This facilitated detection is generally paralleled by larger neural responses in early sensory areas, relative to the processing of neutral information. In this sense, the amygdala and other limbic regions, such as the orbitofrontal cortex, may play a critical role by sending modulatory projections onto the sensory cortices via direct or indirect feedback.The present project aimed at investigating two important issues regarding these mechanisms of emotional attention, by means of functional magnetic resonance imaging. In Study I, we examined the modulatory effects of visual emotion signals on the processing of task-irrelevant visual, auditory, and somatosensory input, that is, the intramodal and crossmodal effects of emotional attention. We observed that brain responses to auditory and tactile stimulation were enhanced during the processing of visual emotional stimuli, as compared to neutral, in bilateral primary auditory and somatosensory cortices, respectively. However, brain responses to visual task-irrelevant stimulation were diminished in left primary and secondary visual cortices in the same conditions. The results also suggested the existence of a multimodal network associated with emotional attention, presumably involving mediofrontal, temporal and orbitofrontal regions Finally, Study II examined the different brain responses along the low-level visual pathways and limbic regions, as a function of the number of retinal spikes during visual emotional processing. The experiment used stimuli resulting from an algorithm that simulates how the visual system perceives a visual input after a given number of retinal spikes. The results validated the visual model in human subjects and suggested differential emotional responses in the amygdala and visual regions as a function of spike-levels. A list of publications resulting from work in the host laboratory is included in the report.

Emotional attention as a modulatory system of perception

Report for the scientific sojourn carried out at the University Medical Center, Swiss, from 2010 to 2012. Abundant evidence suggests that negative emotional stimuli are prioritized in the perceptual systems, eliciting enhanced neural responses in early sensory regions as compared with neutral information. This facilitated detection is generally paralleled by larger neural responses in early sensory areas, relative to the processing of neutral information. In this sense, the amygdala and other limbic regions, such as the orbitofrontal cortex, may play a critical role by sending modulatory projections onto the sensory cortices via direct or indirect feedback.The present project aimed at investigating two important issues regarding these mechanisms of emotional attention, by means of functional magnetic resonance imaging. In Study I, we examined the modulatory effects of visual emotion signals on the processing of task-irrelevant visual, auditory, and somatosensory input, that is, the intramodal and crossmodal effects of emotional attention. We observed that brain responses to auditory and tactile stimulation were enhanced during the processing of visual emotional stimuli, as compared to neutral, in bilateral primary auditory and somatosensory cortices, respectively. However, brain responses to visual task-irrelevant stimulation were diminished in left primary and secondary visual cortices in the same conditions. The results also suggested the existence of a multimodal network associated with emotional attention, presumably involving mediofrontal, temporal and orbitofrontal regions Finally, Study II examined the different brain responses along the low-level visual pathways and limbic regions, as a function of the number of retinal spikes during visual emotional processing. The experiment used stimuli resulting from an algorithm that simulates how the visual system perceives a visual input after a given number of retinal spikes. The results validated the visual model in human subjects and suggested differential emotional responses in the amygdala and visual regions as a function of spike-levels. A list of publications resulting from work in the host laboratory is included in the report.

Emotionally negative stimuli can overcome attentional deficits in patients with visuo-spatial hemineglect.

Left unilateral spatial neglect resulting from right brain damage is characterized by loss of awareness for stimuli in the contralesional side of space, despite intact visual pathways. We examined using fMRI whether patients with neglect are more likely to consciously detect in the neglected hemifield, emotionally negative complex scenes rather than visually similar neutral pictures and if so, what neural mechanisms mediate this effect. Photographs of emotional and neutral scenes taken from the IAPS were presented in a divided visual field paradigm. As expected, the detection rate for emotional stimuli presented in the neglected field was higher than for neutral ones. Successful detection of emotional scenes as opposed to neutral stimuli in the left visual field (LVF) produced activations in the parahippocampal and anterior cingulate areas in the right hemisphere. Detection of emotional stimuli presented in the intact right visual field (RVF) activated a distributed network of structures in the left hemisphere, including anterior and posterior cingulate cortex, insula, as well as visual striate and extrastriate areas. LVF-RVF contrasts for emotional stimuli revealed activations in right and left attention related prefrontal areas whereas RVF-LVF comparison showed activations in the posterior cingulate and extrastriate visual cortex in the left hemisphere. An additional analysis contrasting detected vs. undetected emotional LVF stimuli showed involvement of left anterior cingulate, right frontal and extrastriate areas. We hypothesize that beneficial role of emotion in overcoming neglect is achieved by activation of frontal and limbic lobe networks, which provide a privileged access of emotional stimuli to attention by top-down modulation of processing in the higher-order extrastriate visual areas. Our results point to the importance of top-down regulatory role of the frontal attentional systems, which might enhance visual activations and lead to greater salience of emotional stimuli for perceptual awareness.

Neuronal adaptation effects in decision making

Recently, there has been an increased interest on the neural mechanisms underlying perceptual decision making. However, the effect of neuronal adaptation in this context has not yet been studied. We begin our study by investigating how adaptation can bias perceptual decisions. We considered behavioral data from an experiment on high-level adaptation-related aftereffects in a perceptual decision task with ambiguous stimuli on humans. To understand the driving force behind the perceptual decision process, a biologically inspired cortical network model was used. Two theoretical scenarios arose for explaining the perceptual switch from the category of the adaptor stimulus to the opposite, nonadapted one. One is noise-driven transition due to the probabilistic spike times of neurons and the other is adaptation-driven transition due to afterhyperpolarization currents. With increasing levels of neural adaptation, the system shifts from a noise-driven to an adaptation-driven modus. The behavioral results show that the underlying model is not just a bistable model, as usual in the decision-making modeling literature, but that neuronal adaptation is high and therefore the working point of the model is in the oscillatory regime. Using the same model parameters, we studied the effect of neural adaptation in a perceptual decision-making task where the same ambiguous stimulus was presented with and without a preceding adaptor stimulus. We find that for different levels of sensory evidence favoring one of the two interpretations of the ambiguous stimulus, higher levels of neural adaptation lead to quicker decisions contributing to a speed–accuracy trade off.

Automatic low baseline stereo in urban areas

In this work we propose a new automatic methodology for computing accurate digital elevation models (DEMs) in urban environments from low baseline stereo pairs that shall be available in the future from a new kind of earth observation satellite. This setting makes both views of the scene similarly, thus avoiding occlusions and illumination changes, which are the main disadvantages of the commonly accepted large-baseline configuration. There still remain two crucial technological challenges: (i) precisely estimating DEMs with strong discontinuities and (ii) providing a statistically proven result, automatically. The first one is solved here by a piecewise affine representation that is well adapted to man-made landscapes, whereas the application of computational Gestalt theory introduces reliability and automation. In fact this theory allows us to reduce the number of parameters to be adjusted, and tocontrol the number of false detections. This leads to the selection of a suitable segmentation into affine regions (whenever possible) by a novel and completely automatic perceptual grouping method. It also allows us to discriminate e.g. vegetation-dominated regions, where such an affine model does not apply anda more classical correlation technique should be preferred. In addition we propose here an extension of the classical ”quantized” Gestalt theory to continuous measurements, thus combining its reliability with the precision of variational robust estimation and fine interpolation methods that are necessary in the low baseline case. Such an extension is very general and will be useful for many other applications as well.

Multisensory facilitation of behavior in monkeys: effects of stimulus intensity.

Multisensory stimuli can improve performance, facilitating RTs on sensorimotor tasks. This benefit is referred to as the redundant signals effect (RSE) and can exceed predictions on the basis of probability summation, indicative of integrative processes. Although an RSE exceeding probability summation has been repeatedly observed in humans and nonprimate animals, there are scant and inconsistent data from nonhuman primates performing similar protocols. Rather, existing paradigms have instead focused on saccadic eye movements. Moreover, the extant results in monkeys leave unresolved how stimulus synchronicity and intensity impact performance. Two trained monkeys performed a simple detection task involving arm movements to auditory, visual, or synchronous auditory-visual multisensory pairs. RSEs in excess of predictions on the basis of probability summation were observed and thus forcibly follow from neural response interactions. Parametric variation of auditory stimulus intensity revealed that in both animals, RT facilitation was limited to situations where the auditory stimulus intensity was below or up to 20 dB above perceptual threshold, despite the visual stimulus always being suprathreshold. No RT facilitation or even behavioral costs were obtained with auditory intensities 30-40 dB above threshold. The present study demonstrates the feasibility and the suitability of behaving monkeys for investigating links between psychophysical and neurophysiologic instantiations of multisensory interactions.

Spontaneous pre-stimulus fluctuations in the activity of right fronto-parietal areas influence inhibitory control performance.

Inhibitory control refers to the ability to suppress planned or ongoing cognitive or motor processes. Electrophysiological indices of inhibitory control failure have been found to manifest even before the presentation of the stimuli triggering the inhibition, suggesting that pre-stimulus brain-states modulate inhibition performance. However, previous electrophysiological investigations on the state-dependency of inhibitory control were based on averaged event-related potentials (ERPs), a method eliminating the variability in the ongoing brain activity not time-locked to the event of interest. These studies thus left unresolved whether spontaneous variations in the brain-state immediately preceding unpredictable inhibition-triggering stimuli also influence inhibitory control performance. To address this question, we applied single-trial EEG topographic analyses on the time interval immediately preceding NoGo stimuli in conditions where the responses to NoGo trials were correctly inhibited [correct rejection (CR)] vs. committed [false alarms (FAs)] during an auditory spatial Go/NoGo task. We found a specific configuration of the EEG voltage field manifesting more frequently before correctly inhibited responses to NoGo stimuli than before FAs. There was no evidence for an EEG topography occurring more frequently before FAs than before CR. The visualization of distributed electrical source estimations of the EEG topography preceding successful response inhibition suggested that it resulted from the activity of a right fronto-parietal brain network. Our results suggest that the fluctuations in the ongoing brain activity immediately preceding stimulus presentation contribute to the behavioral outcomes during an inhibitory control task. Our results further suggest that the state-dependency of sensory-cognitive processing might not only concern perceptual processes, but also high-order, top-down inhibitory control mechanisms.

Preperceptual and stimulus-selective enhancement of low-level human visual cortex excitability by sounds.

Evidence of multisensory interactions within low-level cortices and at early post-stimulus latencies has prompted a paradigm shift in conceptualizations of sensory organization. However, the mechanisms of these interactions and their link to behavior remain largely unknown. One behaviorally salient stimulus is a rapidly approaching (looming) object, which can indicate potential threats. Based on findings from humans and nonhuman primates suggesting there to be selective multisensory (auditory-visual) integration of looming signals, we tested whether looming sounds would selectively modulate the excitability of visual cortex. We combined transcranial magnetic stimulation (TMS) over the occipital pole and psychophysics for "neurometric" and psychometric assays of changes in low-level visual cortex excitability (i.e., phosphene induction) and perception, respectively. Across three experiments we show that structured looming sounds considerably enhance visual cortex excitability relative to other sound categories and white-noise controls. The time course of this effect showed that modulation of visual cortex excitability started to differ between looming and stationary sounds for sound portions of very short duration (80 ms) that were significantly below (by 35 ms) perceptual discrimination threshold. Visual perceptions are thus rapidly and efficiently boosted by sounds through early, preperceptual and stimulus-selective modulation of neuronal excitability within low-level visual cortex.

Satisfaction in choice as a function of the number of alternatives: When "goods satiate" but "bads escalate"

Whereas people are typically thought to be better off with more choices, studiesshow that they often prefer to choose from small as opposed to large sets of alternatives.We propose that satisfaction from choice is an inverted U-shaped function of thenumber of alternatives. This proposition is derived theoretically by considering thebenefits and costs of different numbers of alternatives and is supported by fourexperimental studies. We also manipulate the perceptual costs of information processingand demonstrate how this affects the resulting satisfaction function. We furtherindicate that satisfaction when choosing from a given set is diminished if people aremade aware of the existence of other choice sets. The role of individual differences insatisfaction from choice is documented by noting effects due to gender and culture. Weconclude by emphasizing the need to have an explicit rationale for knowing how muchchoice is enough.

Generalized canonical correlation analysis of matrices with different row and column orders

A Method is offered that makes it possible to apply generalized canonicalcorrelations analysis (CANCOR) to two or more matrices of different row and column order. The new method optimizes the generalized canonical correlationanalysis objective by considering only the observed values. This is achieved byemploying selection matrices. We present and discuss fit measures to assessthe quality of the solutions. In a simulation study we assess the performance of our new method and compare it to an existing procedure called GENCOM,proposed by Green and Carroll. We find that our new method outperforms the GENCOM algorithm both with respect to model fit and recovery of the truestructure. Moreover, as our new method does not require any type of iteration itis easier to implement and requires less computation. We illustrate the methodby means of an example concerning the relative positions of the political parties inthe Netherlands based on provincial data.

Inundações urbanas: desafios ao ordenamento do território. O caso da Cidade da Praia (Cabo Verde)

Pela sua posição geográfica e particulares condições climáticas, devidas à sua inserção na faixa saheliana com caraterísticas de marcada aridez, Cabo Verde é um arquipélago com condições naturais adversas, pautado principalmente pela seca prolongada. Muitas vezes esta conjuntura é interpolada por curtos períodos de fortes chuvadas que podem originar cheias e inundações nos principais centros urbanos. Os eventos ocorridos revelam consequências graves, desde prejuízos na agricultura, perda de animais, destruição de infra-estruturas, perda de bens materiais e, mesmo, vítimas humanas mortais. Este estudo tem como objetivos principais: (i) perceber os problemas e desafios que se colocam à cidade da Praia (maior centro urbano do país, com forte crescimento e expansão urbana) perante situações de inundação; (ii) contribuir para o maior conhecimento das causas e consequências dessas inundações; (iii) definir quais as áreas de maior suscetibilidade às cheias e quais as que possuem um maior risco potencial. Optou-se por uma metodologia integrada, através do levantamento bibliográfico, cartográfico, numérico e percetivo (com base em entrevistas e inquéritos). Para o estudo das bacias hidrográficas foram calculados índices morfométricos, definidas classes de permeabilidade do substrato geológico e aplicado o método multicritério de Reis (2011) para a definição das áreas suscetíveis às cheias. Analisaram-se as precipitações máximas diárias anuais e respetivos períodos de retorno, com a aplicação do método de Gumbel. A análise de notícias de jornais, referentes ao período compreendido entre 1980 e 2011, foi fundamental para o conhecimento da distribuição espácio-temporal dos eventos perigosos de inundação em Cabo Verde e na cidade da Praia. Os resultados obtidos revelam um significativo grau de suscetibilidade às cheias na cidade da Praia. As áreas de maior risco potencial às inundações encontram-se no setor central da cidade, resultante da conjugação da convergência do escoamento das três ribeiras principais, da elevada densidade populacional e de construção desordenada nos leitos de cheia e nas áreas deprimidas, onde se acumulam as águas.

Neural control of vascular reactions: impact of emotion and attention.

This study investigated the neural regions involved in blood pressure reactions to negative stimuli and their possible modulation by attention. Twenty-four healthy human subjects (11 females; age = 24.75 ± 2.49 years) participated in an affective perceptual load task that manipulated attention to negative/neutral distractor pictures. fMRI data were collected simultaneously with continuous recording of peripheral arterial blood pressure. A parametric modulation analysis examined the impact of attention and emotion on the relation between neural activation and blood pressure reactivity during the task. When attention was available for processing the distractor pictures, negative pictures resulted in behavioral interference, neural activation in brain regions previously related to emotion, a transient decrease of blood pressure, and a positive correlation between blood pressure response and activation in a network including prefrontal and parietal regions, the amygdala, caudate, and mid-brain. These effects were modulated by attention; behavioral and neural responses to highly negative distractor pictures (compared with neutral pictures) were smaller or diminished, as was the negative blood pressure response when the central task involved high perceptual load. Furthermore, comparing high and low load revealed enhanced activation in frontoparietal regions implicated in attention control. Our results fit theories emphasizing the role of attention in the control of behavioral and neural reactions to irrelevant emotional distracting information. Our findings furthermore extend the function of attention to the control of autonomous reactions associated with negative emotions by showing altered blood pressure reactions to emotional stimuli, the latter being of potential clinical relevance.

Inundações Urbanas - Desafios ao Ordenamento do Território - O

Pela sua posição geográfica e particulares condições climáticas, devidas à sua inserção na faixa saheliana com caraterísticas de marcada aridez, Cabo Verde é um arquipélago com condições naturais adversas, pautado principalmente pela seca prolongada. Muitas vezes esta conjuntura é interpolada por curtos períodos de fortes chuvadas que podem originar cheias e inundações nos principais centros urbanos. Os eventos ocorridos revelam consequências graves, desde prejuízos na agricultura, perda de animais, destruição de infra-estruturas, perda de bens materiais e, mesmo, vítimas humanas mortais. Este estudo tem como objetivos principais: (i) perceber os problemas e desafios que se colocam à cidade da Praia (maior centro urbano do país, com forte crescimento e expansão urbana) perante situações de inundação; (ii) contribuir para o maior conhecimento das causas e consequências dessas inundações; (iii) definir quais as áreas de maior suscetibilidade às cheias e quais as que possuem um maior risco potencial. Optou-se por uma metodologia integrada, através do levantamento bibliográfico, cartográfico, numérico e percetivo (com base em entrevistas e inquéritos). Para o estudo das bacias hidrográficas foram calculados índices morfométricos, definidas classes de permeabilidade do substrato geológico e aplicado o método multicritério de Reis (2011) para a definição das áreas suscetíveis às cheias. Analisaram-se as precipitações máximas diárias anuais e respetivos períodos de retorno, com a aplicação do método de Gumbel. A análise de notícias de jornais, referentes ao período compreendido entre 1980 e 2011, foi fundamental para o conhecimento da distribuição espácio-temporal dos eventos perigosos de inundação em Cabo Verde e na cidade da Praia. Os resultados obtidos revelam um significativo grau de suscetibilidade às cheias na cidade da Praia. As áreas de maior risco potencial às inundações encontram-se no setor central da cidade, resultante da conjugação da convergência do escoamento das três ribeiras principais, da elevada densidade populacional e de construção desordenada nos leitos de cheia e nas áreas deprimidas, onde se acumulam as águas.

Noise in Brain Activity Engenders Perception and Influences Discrimination Sensitivity.

Behavioral and brain responses to identical stimuli can vary with experimental and task parameters, including the context of stimulus presentation or attention. More surprisingly, computational models suggest that noise-related random fluctuations in brain responses to stimuli would alone be sufficient to engender perceptual differences between physically identical stimuli. In two experiments combining psychophysics and EEG in healthy humans, we investigated brain mechanisms whereby identical stimuli are (erroneously) perceived as different (higher vs lower in pitch or longer vs shorter in duration) in the absence of any change in the experimental context. Even though, as expected, participants' percepts to identical stimuli varied randomly, a classification algorithm based on a mixture of Gaussians model (GMM) showed that there was sufficient information in single-trial EEG to reliably predict participants' judgments of the stimulus dimension. By contrasting electrical neuroimaging analyses of auditory evoked potentials (AEPs) to the identical stimuli as a function of participants' percepts, we identified the precise timing and neural correlates (strength vs topographic modulations) as well as intracranial sources of these erroneous perceptions. In both experiments, AEP differences first occurred ∼100 ms after stimulus onset and were the result of topographic modulations following from changes in the configuration of active brain networks. Source estimations localized the origin of variations in perceived pitch of identical stimuli within right temporal and left frontal areas and of variations in perceived duration within right temporoparietal areas. We discuss our results in terms of providing neurophysiologic evidence for the contribution of random fluctuations in brain activity to conscious perception.

Construcción y redefinición de identidades, prácticas culturales yComunicación. Estudio de caso del Centro Cultural Comunitario de PlayaAncha (Valparaíso)

Esta investigación se enmarca en el estudio de la vida cotidiana de las personas y se pregunta específicamente por el proceso de construcción y redefinición de identidades, es decir los cambios en la vida de las personas. Un tema que podría ser demasiado general se encuadra en un caso concreto: El Centro Cultural Comunitario de Playa Ancha (CCPA)1.Entendemos todo proceso de construcción y redefinición identitaria como una experiencia de aprendizaje perceptual. En el marco específico del CCPA, los participantes han construido una comunidad de práctica a través de sus interacciones comunicativas recurrentes en el tiempo, prácticas comunicativas y significativas para los miembros del CCPA. Comparten una serie de repertorios simbólicos, relaciones de participación y cooperación, entre otras cosas. Aprendizaje que logrado que los integrantes del CCPA sean reconocidos por su entorno como practicantes y miembros del CCPA.Para explorar este proceso nos posicionamos desde un abordaje cualitativo. Por lo mismo, intentamos objetivar esta experiencia de aprendizaje perceptual desde las percepciones y las prácticas de los sujetos estudiados. Se contempla el desarrollo de un trabajo de campo de 6 meses que contempla un período de inmersión en la comunidad a través de la observación participante.Por medio de esta herramienta, se explorará en las formas que organizan su espacio, sus tiempos, sus prácticas y por ende, sus interacciones comunicativas. Es decir, como establecen y coordinan el vivir en común. Posteriormente, para objetivar el proceso de construcción y redefinición identitaria se realizarán 10 historias orales temáticas a los miembros más antiguos y experimentados del CCPA.