Catching the news: Processing strategies in listening to dialogs as measured by ERPs

<p>Abstract</p> <p>Background</p> <p>The online segmentation of spoken single sentences has repeatedly been associated with a particular event-related brain potential. The brain response could be attributed to the perception of major prosodic boundaries, and was termed Closure Positive Shift (CPS). However, verbal exchange between humans is mostly realized in the form of cooperative dialogs instead of loose strings of single sentences. The present study investigated whether listeners use prosodic cues for structuring larger contextually embedded utterances (i.e. dialogs) like in single sentence processing.</p> <p>Methods</p> <p>ERPs were recorded from listeners (n = 22) when presented with question-answer dialogs in German. The prosody of the answer (target sentence) either matched the context provided by a question or did not match the context question.</p> <p>Results</p> <p>CPS responses to the processing of the target sentences are elicited, first, when listeners encounter information comprising 'novelties', i.e. information not mentioned in the preceding question but facts corrected between context and target. Thereby it is irrelevant whether the actual prosody of the target sentence is in congruence with the informative status or not. Second, when listeners encounter target sentences which do not convey any novelties but only previously 'given' already known information, the structuring of the speech input is driven by prosody again. The CPS is then elicited when listeners perceive major prosodic boundaries similar as for the processing of context-free single sentences.</p> <p>Conclusion</p> <p>The study establishes a link between the on-line structuring of context-free (single sentences) and context-embedded utterances (dialogs) as measured by ERPs. Moreover, the impact of prosodic phrasing and accentuation on the perception of spoken utterances on and beyond sentence level is discussed.</p

Context- and Prosody-Driven ERP Markers for Dialog Focus Perception in Children

The development of language proficiency extends late into childhood and includes not only producing or comprehending sounds, words and sentences, but likewise larger utterances spanning beyond sentence borders like dialogs. Dialogs consist of information units whose value constantly varies within a verbal exchange. While information is focused when introduced for the first time or corrected in order to alter the knowledge state of communication partners, the same information turns into shared knowledge during the further course of a verbal exchange. In many languages, prosodic means are used by speakers to highlight the informational value of information foci. Our study investigated the developmental pattern of event-related potentials (ERPs) in three age groups (12, 8 and 5years) when perceiving two information focus types (news and corrections) embedded in short question-answer dialogs. The information foci contained in the answer sentences were either adequately marked by prosodic means or not. In so doing, we questioned to what extent children depend on prosodic means to recognize information foci or whether contextual means as provided by dialog questions are sufficient to guide focus processing. Only 12-year-olds yield prosody-independent ERPs when encountering new and corrective information foci, resembling previous findings in adults. Focus processing in the 8-year-olds relied upon prosodic highlighting, and differing ERP responses as a function of focus type were observed. In the 5-year-olds, merely prosody-driven ERP responses were apparent, but no distinctive ERP indicating information focus recognition. Our findings reveal substantial alterations in information focus perception throughout childhood that are likely related to long-lasting maturational changes during brain developmen

Visual-Gustatory Interaction: Orbitofrontal and Insular Cortices Mediate the Effect of High-Calorie Visual Food Cues on Taste Pleasantness

Vision provides a primary sensory input for food perception. It raises expectations on taste and nutritional value and drives acceptance or rejection. So far, the impact of visual food cues varying in energy content on subsequent taste integration remains unexplored. Using electrical neuroimaging, we assessed whether high- and low-calorie food cues differentially influence the brain processing and perception of a subsequent neutral electric taste. When viewing high-calorie food images, participants reported the subsequent taste to be more pleasant than when low-calorie food images preceded the identical taste. Moreover, the taste-evoked neural activity was stronger in the bilateral insula and the adjacent frontal operculum (FOP) within 100 ms after taste onset when preceded by high- versus low-calorie cues. A similar pattern evolved in the anterior cingulate (ACC) and medial orbitofrontal cortex (OFC) around 180 ms, as well as, in the right insula, around 360 ms. The activation differences in the OFC correlated positively with changes in taste pleasantness, a finding that is an accord with the role of the OFC in the hedonic evaluation of taste. Later activation differences in the right insula likely indicate revaluation of interoceptive taste awareness. Our findings reveal previously unknown mechanisms of cross-modal, visual-gustatory, sensory interactions underlying food evaluation

Generating Controlled Image Sets in Cognitive Neuroscience Research

The investigation of perceptual and cognitive functions with non-invasive brain imaging methods critically depends on the careful selection of stimuli for use in experiments. For example, it must be verified that any observed effects follow from the parameter of interest (e.g. semantic category) rather than other low-level physical features (e.g. luminance, or spectral properties). Otherwise, interpretation of results is confounded. Often, researchers circumvent this issue by including additional control conditions or tasks, both of which are flawed and also prolong experiments. Here, we present some new approaches for controlling classes of stimuli intended for use in cognitive neuroscience, however these methods can be readily extrapolated to other applications and stimulus modalities. Our approach is comprised of two levels. The first level aims at equalizing individual stimuli in terms of their mean luminance. Each data point in the stimulus is adjusted to a standardized value based on a standard value across the stimulus battery. The second level analyzes two populations of stimuli along their spectral properties (i.e. spatial frequency) using a dissimilarity metric that equals the root mean square of the distance between two populations of objects as a function of spatial frequency along x- and y-dimensions of the image. Randomized permutations are used to obtain a minimal value between the populations to minimize, in a completely data-driven manner, the spectral differences between image sets. While another paper in this issue applies these methods in the case of acoustic stimuli (Aeschlimann etal., Brain Topogr 2008), we illustrate this approach here in detail for complex visual stimul

Gender and Weight Shape Brain Dynamics during Food Viewing

Hemodynamic imaging results have associated both gender and body weight to variation in brain responses to food-related information. However, the spatio-temporal brain dynamics of gender-related and weight-wise modulations in food discrimination still remain to be elucidated. We analyzed visual evoked potentials (VEPs) while normal-weighted men (n = 12) and women (n = 12) categorized photographs of energy-dense foods and non-food kitchen utensils. VEP analyses showed that food categorization is influenced by gender as early as 170 ms after image onset. Moreover, the female VEP pattern to food categorization co-varied with participants' body weight. Estimations of the neural generator activity over the time interval of VEP modulations (i.e. by means of a distributed linear inverse solution [LAURA]) revealed alterations in prefrontal and temporo-parietal source activity as a function of image category and participants' gender. However, only neural source activity for female responses during food viewing was negatively correlated with body-mass index (BMI) over the respective time interval. Women showed decreased neural source activity particularly in ventral prefrontal brain regions when viewing food, but not non-food objects, while no such associations were apparent in male responses to food and non-food viewing. Our study thus indicates that gender influences are already apparent during initial stages of food-related object categorization, with small variations in body weight modulating electrophysiological responses especially in women and in brain areas implicated in food reward valuation and intake control. These findings extend recent reports on prefrontal reward and control circuit responsiveness to food cues and the potential role of this reactivity pattern in the susceptibility to weight gain

Dynamic Changes in Brain Functional Connectivity during Concurrent Dual-Task Performance

This study investigated the spatial, spectral, temporal and functional proprieties of functional brain connections involved in the concurrent execution of unrelated visual perception and working memory tasks. Electroencephalography data was analysed using a novel data-driven approach assessing source coherence at the whole-brain level. Three connections in the beta-band (18–24 Hz) and one in the gamma-band (30–40 Hz) were modulated by dual-task performance. Beta-coherence increased within two dorsofrontal-occipital connections in dual-task conditions compared to the single-task condition, with the highest coherence seen during low working memory load trials. In contrast, beta-coherence in a prefrontal-occipital functional connection and gamma-coherence in an inferior frontal-occipitoparietal connection was not affected by the addition of the second task and only showed elevated coherence under high working memory load. Analysis of coherence as a function of time suggested that the dorsofrontal-occipital beta-connections were relevant to working memory maintenance, while the prefrontal-occipital beta-connection and the inferior frontal-occipitoparietal gamma-connection were involved in top-down control of concurrent visual processing. The fact that increased coherence in the gamma-connection, from low to high working memory load, was negatively correlated with faster reaction time on the perception task supports this interpretation. Together, these results demonstrate that dual-task demands trigger non-linear changes in functional interactions between frontal-executive and occipitoparietal-perceptual cortices

Spatiotemporal Brain Signatures of Risk and Reward

Rational economics and finance surmise that choices decree from a conscious arbitration between alternatives based on decision-theoretically computed values. Implicit in the computation of these option values are the perception and integration of different mathematical components (e.g., magnitude, valence, expected value and risk) of monetary rewards. Functional neuroimaging studies have consistently revealed that spatially distributed brain areas encode such mathematical moments that are the cornerstones of modern financial theory. However, the dynamics of the neurophysiological mechanisms whereby these computational parameters influence behavior remains poorly understood. To unravel the spatio-temporal electrophysiological (EEG) correlates of these computational statistics, we devised a novel experimental approach with sequentially presented information. Subjects decided whether or not to buy into a series of independent gambles while 128-channels EEG was acquired. Within a parallel factor (PARAFAC) analytical framework, constrained to take into account the physiological features of EEG signals and financial theoretic structure in the behavioral data, we identified for the first time and within a single experiment the EEG markers of mathematical moments and action values. Specifically, risk-related features - variance and skewness - are extracted within the first 350ms post-stimulus onset. EEG modulations predictive of choice and sensitive to expected value were observed 200ms prior to overt/registered choice. Distinct topographic maps indicate that the different processes are subserved by distinct networks of intracranial sources; the associated time courses occur at times in parallel albeit peaking at different latencies. Importantly, unlike option value computation and decision-making, information retrieval and choice implementation have time-consistent EEG signatures across subjects

Spatiotemporal Brain Signatures of Risk and Reward

Rational economics and finance surmise that choices decree from a conscious arbitration between alternatives based on decision-theoretically computed values. Implicit in the computation of these option values are the perception and integration of different mathematical components (e.g., magnitude, valence, expected value and risk) of monetary rewards. Functional neuroimaging studies have consistently revealed that spatially distributed brain areas encode such mathematical moments that are the cornerstones of modern financial theory. However, the dynamics of the neurophysiological mechanisms whereby these computational parameters influence behavior remains poorly understood. To unravel the spatio-temporal electrophysiological (EEG) correlates of these computational statistics, we devised a novel experimental approach with sequentially presented information. Subjects decided whether or not to buy into a series of independent gambles while 128-channels EEG was acquired. Within a parallel factor (PARAFAC) analytical framework, constrained to take into account the physiological features of EEG signals and financial theoretic structure in the behavioral data, we identified for the first time and within a single experiment the EEG markers of mathematical moments and action values. Specifically, risk-related features - variance and skewness - are extracted within the first 350ms post-stimulus onset. EEG modulations predictive of choice and sensitive to expected value were observed 200ms prior to overt/registered choice. Distinct topographic maps indicate that the different processes are subserved by distinct networks of intracranial sources; the associated time courses occur at times in parallel albeit peaking at different latencies. Importantly, unlike option value computation and decision-making, information retrieval and choice implementation have time-consistent EEG signatures across subjects