Stereoscopic depth increases intersubject correlations of brain networks

Three-dimensionalmovies presented via stereoscopic displays have becomemore popular in recent years aiming at a more engaging viewing experience. However, neurocognitive processes associated with the perception of stereoscopic depth in complex and dynamic visual stimuli remain understudied. Here, we investigate the influence of stereoscopic depth on both neurophysiology and subjective experience. Using multivariate statistical learning methods, we compare the brain activity of subjects when freely watching the same movies in 2D and in 3D. Subjective reports indicate that 3D movies are more strongly experienced than 2D movies. On the neural level, we observe significantly higher intersubject correlations of cortical networks when subjects are watching 3D movies relative to the same movies in 2D. We demonstrate that increases in intersubject correlations of brain networks can serve as neurophysiologicalmarker for stereoscopic depth and for the strength of the viewing experience

FMRI study of parallax under topic driven stimuli

Little is known regarding the brain regions responsible for the perception of 3 dimensional (3D) versus 2 dimensional (2D) images. Thus, functional magnetic resonance imaging (fMRI) was used to determine activation patterns in the human brain under stereoscopic or monoscopic stimuli (e.g. 3D or 2D). To examine whether these regions differ as a function of subject matter, stimuli were separated based on the image themes: locations, objects, and plants and animals. A block design was used to collect data from subjects who were asked to view images in 2 and 3 dimensions in 6 runs. The goal of this study was to determine whether the activation pattern using passive 3D viewing is similar to what has been previously demonstrated using other 3D viewing techniques. A secondary aim was to determine if the stimulus thematic content altered the brain regions involved. The results revealed that in addition to lateral occipital complex (LOC), which has been previously discussed in literature, the supramarginal gyrus and parietal operculum cortex are involved in 3D image perception

Enhanced processing of aversive stimuli on embodied artificial limbs by the human amygdala

Body perception has been extensively investigated, with one particular focus being the integration of vision and touch within a neuronal body representation. Previous studies have implicated a distributed network comprising the extrastriate body area (EBA), posterior parietal cortex (PPC) and ventral premotor cortex (PMv) during illusory self-attribution of a rubber hand. Here, we set up an fMRI paradigm in virtual reality (VR) to study whether and how the self-attribution of (artificial) body parts is altered if these body parts are somehow threatened. Participants (N = 30) saw a spider (aversive stimulus) or a toy-car (neutral stimulus) moving along a 3D-rendered virtual forearm positioned like their real forearm, while tactile stimulation was applied on the real arm in the same (congruent) or opposite (incongruent) direction. We found that the PPC was more activated during congruent stimulation; higher visual areas and the anterior insula (aIns) showed increased activation during aversive stimulus presentation; and the amygdala was more strongly activated for aversive stimuli when there was stronger multisensory integration of body-related information (interaction of aversiveness and congruency). Together, these findings suggest an enhanced processing of aversive stimuli within the amygdala when they represent a bodily threat

Enhanced processing of aversive stimuli on embodied artificial limbs by the human amygdala

Body perception has been extensively investigated, with one particular focus being the integration of vision and touch within a neuronal body representation. Previous studies have implicated a distributed network comprising the extrastriate body area (EBA), posterior parietal cortex (PPC) and ventral premotor cortex (PMv) during illusory self-attribution of a rubber hand. Here, we set up an fMRI paradigm in virtual reality (VR) to study whether and how the self-attribution of (artificial) body parts is altered if these body parts are somehow threatened. Participants (N = 30) saw a spider (aversive stimulus) or a toy-car (neutral stimulus) moving along a 3D-rendered virtual forearm positioned like their real forearm, while tactile stimulation was applied on the real arm in the same (congruent) or opposite (incongruent) direction. We found that the PPC was more activated during congruent stimulation; higher visual areas and the anterior insula (aIns) showed increased activation during aversive stimulus presentation; and the amygdala was more strongly activated for aversive stimuli when there was stronger multisensory integration of body-related information (interaction of aversiveness and congruency). Together, these findings suggest an enhanced processing of aversive stimuli within the amygdala when they represent a bodily threat

Decoding subjective emotional arousal from eeg during an immersive virtual reality experience

Immersive virtual reality (VR) enables naturalistic neuroscientific studies while maintaining experimental control, but dynamic and interactive stimuli pose methodological challenges. We here probed the link between emotional arousal, a fundamental property of affective experience, and parieto-occipital alpha power under naturalistic stimulation: 37 young healthy adults completed an immersive VR experience, which included rollercoaster rides, while their EEG was recorded. They then continuously rated their subjective emotional arousal while viewing a replay of their experience. The association between emotional arousal and parieto-occipital alpha power was tested and confirmed by (1) decomposing the continuous EEG signal while maximizing the comodulation between alpha power and arousal ratings and by (2) decoding periods of high and low arousal with discriminative common spatial patterns and a Long Short-Term Memory recurrent neural network. We successfully combine EEG and a naturalistic immersive VR experience to extend previous findings on the neurophysiology of emotional arousal towards real-world neuroscience

Improving Stimulus Realism: The effect of visual dimension on affective responding

For decades researchers have used 2D stimuli under the assumption that they accurately represent real objects. This assumption has been challenged by recent vision and neuroeconomics research which has found that 2D images can evoke different neural and behavioural responses than real objects. The current study continues this line of research in the field of affective cognitive neuroscience; a field where small effect sizes are common and rapid habituation to affective stimuli used in the lab often occurs. The present study uses realistic 2D and 3D emotional images to determine the impact of visual dimension on affective responding. Subjective ratings revealed a perceptual advantage for 3D images which were rated more realistic and received some higher ratings of emotion than 2D images. Conversely, there were no differences in psychophysiological responding (i.e. skin conductance and electromyography) between 2D and 3D images. The implications of these results and future directions are discussed

Social perception in the real world : employing visual adaptation paradigms in the investigation of mechanisms underlying emotion and trustworthiness perception

Social context can substantially influence our perception and understanding of emotion and action of observed individuals. However, less is known about how temporal context can affect our judgement of behaviour of other people. The aim of this thesis was to explore how immediate perceptual history influences social perception. Further aims were: (i) to examine whether prior visual experience influences the perception of behaviour of other individuals in a naturalistic virtual environment resembling the real world; (ii) to determine whether our judgement of emotional state or trustworthiness of observed individuals is influenced by perceptual history, and (iii) by cognitive processes such as mental state attribution to the observer; (iv) to investigate whether processing of emotion information from dynamic, whole-body action is dependent on the processing of body identity, and (v) dependent on the body part that conveys it. Here, visual adaptation paradigms were used to examine systematic biases in social perception following prior visual experience, and to infer potential neural mechanisms underlying social perception. The results presented in this thesis suggest that perception and understanding of behaviour of other individuals in the naturalistic virtual environment are influenced by the behaviour of other individuals within the shared social environment. Specifically, in Chapter 3, I presented data suggesting that visual adaptation mechanisms examined thus far in laboratory settings may influence our everyday perception and judgement of behaviour of other people. In Chapters 4 and 5, I showed that these biases in social perception can be attributed to visual adaptation mechanisms, which code emotions and intentions derived from actions with respect to specific action kinematics and the body part that conveyed the given emotion. The results of experiments presented in Chapter 4 demonstrated that emotions conveyed by actions are represented with respect to, and independently of, actors’ identity. These finding suggest that the mechanisms underlying processing of action emotion may operate in parallel with the mechanisms underlying processing emotion from other social signals such as face and voice. In Chapter 6, I showed that cognitive processes underlying Theory of Mind, such as mental state attribution, can also influence perceptual processing of emotional signals. Finally, results presented in Chapter 7 suggest that judgments of complex social traits such as trustworthiness derived from faces are also influenced by perceptual history. These results also yielded strong sex differences in assessing trustworthiness of an observed individual; female observers showed a strong bias in perception resulting from adaptation to (un)trustworthiness, while male observers were less influenced by prior visual context. Together these findings suggest that social perception in the real world may be sensitive not only to the social context in which an observed act is embedded, but also to the prior visual context and the observer’s beliefs regarding the observed individual. Visual adaptation mechanisms may therefore operate during our everyday perception, in order to adjust our visual system to allow for efficient and accurate judgement of socially meaningful stimuli. The findings presented in this thesis highlight the importance of studying social perception using naturalistic stimuli embedded in a meaningful social scene, in order to gain a better understanding of the mechanisms that underlie our judgement of behaviour of other people. They also demonstrate the utility of visual adaptation paradigms in studying social perception and social cognition