Building on a Solid Baseline: Anticipatory Biases in Attention.

A brain-imaging paper by Kastner and colleagues in 1999 was the first to demonstrate that merely focusing attention at a spatial location changed the baseline activity level in various regions of human visual cortex even before any stimuli appeared. The study provided a touchstone for investigating cognitive-sensory interactions and understanding the proactive endogenous signals that shape perception

Spatiotemporal dynamics in human visual cortex rapidly encode the emotional content of faces

Recognizing emotion in faces is important in human interaction and survival, yet existing studies do not paint a consistent picture of the neural representation supporting this task. To address this, we collected magnetoencephalography (MEG) data while participants passively viewed happy, angry and neutral faces. Using time-resolved decoding of sensor-level data, we show that responses to angry faces can be discriminated from happy and neutral faces as early as 90 ms after stimulus onset and only 10 ms later than faces can be discriminated from scrambled stimuli, even in the absence of differences in evoked responses. Time-resolved relevance patterns in source space track expression-related information from the visual cortex (100 ms) to higher-level temporal and frontal areas (200–500 ms). Together, our results point to a system optimised for rapid processing of emotional faces and preferentially tuned to threat, consistent with the important evolutionary role that such a system must have played in the development of human social interactions

Spatiotemporal dynamics in human visual cortex rapidly encode the emotional content of faces

Recognizing emotion in faces is important in human interaction and survival, yet existing studies do not paint a consistent picture of the neural representation supporting this task. To address this, we collected magnetoencephalography (MEG) data while participants passively viewed happy, angry and neutral faces. Using time-resolved decoding of sensor-level data, we show that responses to angry faces can be discriminated from happy and neutral faces as early as 90 ms after stimulus onset and only 10 ms later than faces can be discriminated from scrambled stimuli, even in the absence of differences in evoked responses. Time-resolved relevance patterns in source space track expression-related information from the visual cortex (100 ms) to higher-level temporal and frontal areas (200-500 ms). Together, our results point to a system optimised for rapid processing of emotional faces and preferentially tuned to threat, consistent with the important evolutionary role that such a system must have played in the development of human social interactions

Physiology and neuroanatomy of emotional reactivity in frontotemporal dementia

ABSTRACT AND SUMMARY OF EXPERIMENTAL FINDINGS The frontotemporal dementias (FTD) are a heterogeneous group of neurodegenerative diseases that cause variable profiles of fronto-insulo-temporal network disintegration. Loss of empathy and dysfunctional social interaction are a leading features of FTD and major determinants of care burden, but remain poorly understood and difficult to measure with conventional neuropsychological instruments. Building on a large body of work in the healthy brain showing that embodied responses are important components of emotional responses and empathy, I performed a series of experiments to examine the extent to which the induction and decoding of somatic physiological responses to the emotions of others are degraded in FTD, and to define the underlying neuroanatomical changes responsible for these deficits. I systematically studied a range of modalities across the entire syndromic spectrum of FTD, including daily life emotional sensitivity, the cognitive categorisation of emotions, interoceptive accuracy, automatic facial mimicry, autonomic responses, and structural and functional neuroanatomy to deconstruct aberrant emotional reactivity in these diseases. My results provide proof of principle for the utility of physiological measures in deconstructing complex socioemotional symptoms and suggest that these warrant further investigation as clinical biomarkers in FTD. Chapter 3: Using a heartbeat counting task, I found that interoceptive accuracy is impaired in semantic variant primary progressive aphasia, but correlates with sensitivity to the emotions of others across FTD syndromes. Voxel based morphometry demonstrated that impaired interoceptive accuracy correlates with grey matter volume in anterior cingulate, insula and amygdala. Chapter 4: Using facial electromyography to index automatic imitation, I showed that mimicry of emotional facial expressions is impaired in the behavioural and right temporal variants of FTD. Automatic imitation predicted correct identification of facial emotions in healthy controls and syndromes focussed on the frontal lobes and insula, but not in syndromes focussed on the temporal lobes, suggesting that automatic imitation aids emotion recognition only when social concepts and semantic stores are intact. Voxel based morphometry replicated previously identified neuroanatomical correlates of emotion identification ability, while automatic imitation was associated with grey matter volume in a visuomotor network including primary visual and motor cortices, visual motion area (MT/V5) and supplementary motor cortex. Chapter 5: By recording heart rate during viewing of facial emotions, I showed that the normal cardiac reactivity to emotion is impaired in FTD syndromes with fronto-insular atrophy (behavioural variant FTD and nonfluent variant primary progressive aphasia) but not in syndromes focussed on the temporal lobes (right temporal variant FTD and semantic variant primary progressive aphasia). Unlike automatic imitation, cardiac reactivity dissociated from emotion identification ability. Voxel based morphometry revealed grey matter correlates of cardiac reactivity in anterior cingulate, insula and orbitofrontal cortex. Chapter 6: Subjects viewed videos of facial emotions during fMRI scanning, with concomitant recording of heart rate and pupil size. I identified syndromic profiles of reduced activity in posterior face responsive regions including posterior superior temporal sulcus and fusiform face area. Emotion identification ability was predicted by activity in more anterior areas including anterior cingulate, insula, inferior frontal gyrus and temporal pole. Autonomic reactivity related to activity in both components of the central autonomic control network and regions responsible for processing the sensory properties of the stimuli

From features to concepts: tracking the neural dynamics of visual perception

The visual system is thought to accomplish categorization through a series of hi- erarchical feature extraction steps, ending with the formation of high-level cate- gory representations in occipitotemporal cortex; however, recent evidence has chal- lenged these assumptions. The experiments described in this thesis address the question of categorization in face and scene perception using magnetoencephalog- raphy and multivariate analysis methods. The first three chapters investigate neural responses to emotional faces from different perspectives, by varying their relevance to task. First, in a passive view- ing paradigm, angry faces elicit differential patterns within 100 ms in visual cortex, consistent with a threat-related bias in feedforward processing. The next chap- ter looks at rapid face perception in the context of an expression discrimination task which also manipulates subjective awareness. A neural response to faces, but not expressions is detected outside awareness. Furthermore, neural patterns and behavioural responses are shown to reflect both facial features and facial config- uration. Finally, the third chapter employs emotional faces as distractors during an orientation discrimination task, but finds no evidence of expression processing outside of attention. The fourth chapter focuses on natural scene perception, using a passive view- ing paradigm to study the contribution of low-level features and high-level cat- egories to MEG patterns. Multivariate analyses reveal a categorical response to scenes emerging within 200 ms, despite ongoing processing of low-level features. Together, these results suggest that feature-based coding of categories, opti- mized for both stimulus relevance and task demands, underpins dynamic high- level representations in the visual system. The findings highlight new avenues in vision research, which may be best pursued by bridging the neural and behavioural levels within a common computational framework

Mechanisms of auditory signal decoding in the progressive aphasias

The primary progressive aphasias (PPA) are a diverse group of neurodegenerative disorders that selectively target brain networks mediating language. The pathophysiology of PPA remains poorly understood, but emerging evidence suggests that deficits in auditory processing accompany and may precede language symptoms in these patients. In four studies, I have probed the pathophysiology of auditory signal decoding in patient cohorts representing all major PPA syndromes – nonfluent variant PPA (nfvPPA), semantic variant PPA (svPPA), and logopenic variant PPA (lvPPA) – in relation to healthy age-matched controls. In my first experiment, I presented sequences of spoken syllables manipulated for temporal regularity, spectrotemporal structure and entropy. I used voxel-based morphometry to define critical brain substrates for the processing of these attributes, identifying correlates of behavioural performance within a cortico-subcortical network extending beyond canonical language areas. In my second experiment, I used activation functional magnetic resonance imaging (fMRI) with the same stimuli. I identified network signatures of particular signal attributes: nfvPPA was associated with reduced activity in anterior cingulate for processing temporal irregularity; lvPPA with reduced activation of posterior superior temporal cortex for processing spectrotemporal structure; and svPPA with reduced activation of caudate and anterior cingulate for processing signal entropy. In my third experiment, I manipulated the auditory feedback via which participants heard their own voices during speech production. Healthy control participants spoke significantly less fluently under delayed auditory feedback, but patients with nfvPPA and lvPPA were affected significantly less. In my final experiment, I probed residual capacity for dynamic auditory signal processing and perceptual learning in PPA, using sinewave speech. Patients with nfvPPA and lvPPA showed severely attenuated learning to the degraded stimuli, while patients with svPPA showed intact early perceptual processing, but deficient integration of semantic knowledge. Together, these experiments represent the most concerted and comprehensive attempt to date to define the pathophysiology of auditory signal decoding in PPA

Social and Affective Neuroscience of Everyday Human Interaction

This Open Access book presents the current state of the art knowledge on social and affective neuroscience based on empirical findings. This volume is divided into several sections first guiding the reader through important theoretical topics within affective neuroscience, social neuroscience and moral emotions, and clinical neuroscience. Each chapter addresses everyday social interactions and various aspects of social interactions from a different angle taking the reader on a diverse journey. The last section of the book is of methodological nature. Basic information is presented for the reader to learn about common methodologies used in neuroscience alongside advanced input to deepen the understanding and usability of these methods in social and affective neuroscience for more experienced readers

Towards a view from within: The contribution of Francisco Varela to the study of consciousness

The contents of consciousness are complex and dynamic and are embedded in perception and cognition. The study of consciousness and subjective experience has been central to philosophy for centuries. However, despite its relevance for understanding cognition and behaviour, the empirical study of consciousness is relatively new, embroiled by the seemingly opposing subjective and objective sources of data. Francisco Varela (1946-2001) pioneered the empirical study of consciousness by developing novel, naturalised and rich approaches in a non-reductive and comprehensive manner. In this article, we review the main conceptual distinctions and philosophical challenges of consciousness research and highlight the main contributions of Varela and his associates: the development of neurophenomenology as a methodological framework that builds a bridge between subjective and objective sources of data and the discovery of gamma-band phase synchronisation as a neural marker of perceptual awareness. Finally, we describe the work of Varela on time consciousness, his philosophical approach and the implementation of his neurophenomenological framework for its study by integrating subjective reports with neural measures

Intrinsic brain activity in health and disease

The main part of the brain’s energy need is to support housekeeping functions and internal information processing, regardless of external tasks. Cognitive brain imaging, aimed at relating mental phenomena to neurophysiological processes, has conventionally investigated the brain activity induced by external stimuli. In contrast, resting state functional Magnetic Resonance Imaging (rs-fMRI) aims to characterize the spatiotemporal properties of the ongoing baseline brain activity. In the projects constituting the current thesis, we have used rs-fMRI to investigate effects of neuropharamcological administrations, long-term physical exercise and to characterize central pain processing in rheumatic pain conditions. Study I is a randomized, cross sectional placebo study, in which healthy subjects were administered Parkinson medications (L-dopa), anxiolytics (oxazepam), or placebo. Our a priori hypothesis of preferential modulations of connectivity of brain regions with high density of target receptors was not confirmed. Instead, oxazepam was associated with increased connectivity of cardinal hubs within the default mode network, and interestingly, a decoupling of the amygdala. L-dopa, on the other hand, primarily decreased connectivity, particularly between amygdala and bilateral prefrontal gyri. In studies II-IV we investigated rheumatic pain patients. In study II we compared a fibromyalgia (FM) cohort and healthy controls (HC) with regard to functional brain connectivity of particularly cerebral pain regions. Conducting both data driven independent component analysis (ICA) and seed correlation analysis (SCA), we observed a weaker coupling between pain regions and sensorimotor brain areas in the FM group. Across groups, pain sensitivity correlated with e.g. increased connectivity between insula and the posterior cingulate cortex. Physical exercise is a potent reliever of FM symptoms. In study III, we investigated the effects a three months physical training intervention for FM patients. Following exercise, patients reported decreased symptom gravity, and the FM associated hyper-connectivity identified at baseline was partly normalized. In study IV, we investigated the extent to which exposure to chronic pain for patients with rheumatoid arthritis (RA) was reflected in functional connectivity of pain regions. Overall, RA patients had elevated connectivity, particularly between frontal midline areas and bilateral sensorimotor cortex. Taken together, we have shown that short-term neuropharmachological interventions, a three months physical exercise intervention as well as long-term rheumatic pain exposure, all are accompanied by changes in intrinsic brain activity. Although the functional significance of the observed group differences in connectivity warrants further investigations, the evidences presented here support the notion that rs-fMRI could prove useful for diagnosing neuropsychiatric conditions and evaluating interventions in the future