Minye Zhan

Neural correlates of body and face perception following bilateral destruction of the primary visual cortices

Non-conscious visual processing of different object categories was investigated in a rare patient with bilateral destruction of the visual cortex (V1) and clinical blindness over the entire visual field. Images of biological and non-biological object categories were presented consisting of human bodies, faces, butterflies, cars, and scrambles. Behaviorally, only the body shape induced higher perceptual sensitivity, as revealed by signal detection analysis. Passive exposure to bodies and faces activated amygdala and superior temporal sulcus. In addition, bodies also activated the extrastriate body area, insula, orbitofrontal cortex (OFC) and cerebellum. The results show that following bilateral damage to the primary visual cortex and ensuing complete cortical blindness, the human visual system is able to process categorical properties of human body shapes. This residual vision may be based on V1-independent input to body-selective areas along the ventral stream, in concert with areas involved in the representation of bodily states, like insula, OFC, and cerebellum.

The Body as a Tool for Anger Awareness—Differential Effects of Angry Facial and Bodily Expressions on Suppression from Awareness

Emotional signals are perceived whether or not we are aware of it. The evidence so far mostly came from studies with facial expressions. Here, we investigated whether the pattern of non-conscious face expression perception is found for whole body expressions. Continuous flash suppression (CFS) was used to measure the time for neutral, fearful, and angry facial or bodily expressions to break from suppression. We observed different suppression time patterns for emotions depending on whether the stimuli were faces or bodies. The suppression time for anger was shortest for bodily expressions, but longest for the facial expressions. This pattern indicates different processing and detection mechanisms for faces and bodies outside awareness, and suggests that awareness mechanisms associated with dorsal structures might play a role in becoming conscious of angry bodily expressions.

Ventral and Dorsal Pathways Relate Differently to Visual Awareness of Body Postures under Continuous Flash Suppression

Abstract Visual perception includes ventral and dorsal stream processes. However, it is still unclear whether the former is predominantly related to conscious and the latter to nonconscious visual perception as argued in the literature. In this study upright and inverted body postures were rendered either visible or invisible under continuous flash suppression (CFS), while brain activity of human participants was measured with functional MRI (fMRI). Activity in the ventral body-sensitive areas was higher during visible conditions. In comparison, activity in the posterior part of the bilateral intraparietal sulcus (IPS) showed a significant interaction of stimulus orientation and visibility. Our results provide evidence that dorsal stream areas are less associated with visual awareness.

Dynamic Interactions between Emotion Perception and Action Preparation for Reacting to Social Threat: A Combined cTBS-fMRI Study

Abstract Expressions of emotion are powerful triggers for situation-appropriate responses by the observer. Of particular interest regarding the preparation of such adaptive actions are parietal and premotor cortices, given their potential for interaction with the amygdala (AMG), which is known to play a crucial role in the processing of affective information and in motor response. We set out to disentangle the respective roles of the inferior parietal lobule (IPL) and ventral premotor cortex (PMv) in humans in the processing of emotional body expressions by assessing remote effects of continuous theta burst stimulation (cTBS) in the action network and in AMG. Participants were presented with blocks of short videos showing either angry or neutral whole-body actions. The experiment consisted of three fMRI sessions: two sessions were preceded by stimulation of either right IPL (rIPL) or right PMv (rPMv); and a third session assessed baseline activity. Interestingly, whereas at baseline the left AMG did not differentiate between neutral and angry body postures, a significant difference between these conditions emerged after stimulation of either rIPL or rPMv, with much larger responses to angry than to neutral stimuli. In addition, the effects of cTBS stimulation and emotion were also observed in two other action-relevant areas, the supplementary motor area and the superior parietal cortex. Together, these results show how areas involved in action and emotion perception and in action preparation interact dynamically.

Looking at the face and seeing the whole body: Neural basis of combined face and body expressions

Abstract In the natural world, faces are not isolated objects but are rather encountered in the context of the whole body. Previous work has studied the perception of combined faces and bodies using behavioural and electrophysiological measurements, but the neural correlates of emotional face–body perception still remain unexplored. Here, we combined happy and fearful faces and bodies to investigate the influence of body expressions on the neural processing of the face, the effect of emotional ambiguity between the two and the role of the amygdala in this process. Our functional magnetic resonance imaging analyses showed that the activity in motor, prefrontal and visual areas increases when facial expressions are presented together with bodies rather than in isolation, consistent with the notion that seeing body expressions triggers both emotional and action-related processes. In contrast, psychophysiological interaction analyses revealed that amygdala modulatory activity increases after the presentation of isolated faces when compared to combined faces and bodies. Furthermore, a facial expression combined with a congruent body enhanced both cortical activity and amygdala functional connectivity when compared to an incongruent face–body compound. Finally, the results showed that emotional body postures influence the processing of facial expressions, especially when the emotion conveyed by the body implies danger.

Gender-specific brain activation during visual art perception

The human body is the most common object of pictorial representation in western art. The goal of this study was to probe its evolutionary basis of visual art perception by investigating neural markers of gender-specific brain activity triggered by paintings of male and female images. Our results show significant activity in brain areas other than those recently associated with visual arts perception. Novel findings concern participant-general as well as gender specific brain activity. Although our participants were fully aware that they were viewing artworks, the inferior parietal lobule - known for its role in the perception of emotional body images - and the somatosensory cortex – which is related to touch - were selectively active for female body paintings in all participants. The most interesting finding as regards gender was that the sight of female bodies activates the subgenual anterior cingulate cortex in males, an area known to subserve autonomic arousal. In contrast, in females the sight of the male body activated reward and control related parts of the dorsal anterior cingulate cortex. This supports the notion that basic evolutionary processes operate when we view body images, also when they are paintings far removed from daily experience.

Layer-specific ultra-high field 7T fMRI showing that threat anticipation is mediated by the pulvinar input to the superficial layers of primary visual cortex (V1)

The perceptual system gives priority to threat-relevant signals with survival value. Its mechanism may not only include the processing initiated in the presence of threat signals but also in the mere anticipation of such signals. Here, we show that the pulvinar modulates activity in the early visual cortex (V1) specifically in threat anticipation. Using ultra-high-field 7T fMRI, we examined the layer-specific interaction between V1 and the pulvinar, while taking advantage of the fact that the directionality of such interaction is anatomically constrained in specific V1 layers. Only in anticipation of a fearful face target, but not of a control happy face target, was false perception of anticipated-yet-unpresented target face accompanied by stronger activity in the V1 superficial-cortical-depth (layers 1-3), which was preceded by pre-target-onset pulvinar activity. The pulvinar may contribute to the visual processing initiated in the anticipation of threat, and play an important role in anxiety.

Influence of continuous flash suppression mask frequency on stimulus visibility

The continuous flash suppression (CFS) paradigm is increasingly used in consciousness research, but its mechanisms are still not fully understood. To better understand its temporal properties, we presented the CFS masks at 9 frequencies, and examined their influence on stimuli visibility, while taking into account the inter-individual variability and the change of CFS suppression as the experiment progressed. The frequencies consisted of fundamental frequencies of 3, 4 and 5 Hz, and their 2nd and 3rd harmonics, which included the 10 Hz frequency typically used in most of the CFS studies. We found that the suppression of stimulus awareness was stronger under 4, 6 and 8 Hz than 10 Hz. After controlling for inter-individual variability with mixed-effects analysis, we found that the number of seen trials was lower for the 4 Hz-basis frequencies than the 5 Hz ones, and was lower for the 2nd than 3rd harmonic. We propose that this may be caused by an interaction between the CFS masks and the ongoing sampling of the attentional mechanism. Examining individual data, we also found a habituation effect that the participants saw significantly more stimuli as the experiment progressed. Our results suggest that these factors need to be taken care of in future CFS studies in order to achieve optimal visual awareness suppression and ensure the generalizability of results.

The Influence of Conscious and Unconscious Body Threat Expressions on Motor Evoked Potentials Studied With Continuous Flash Suppression

The observation of threatening expression in others is a strong cue for triggering an action response. One method of capturing such action responses is by measuring the amplitude of motor evoked potentials (MEPs) elicited with single pulse TMS over the primary motor cortex. Indeed, it has been shown that viewing whole body expressions of threat modulate the size of MEP amplitude. Furthermore, emotional cues have been shown to act on certain brain areas even outside of conscious awareness. In the current study, we explored if the influence of viewing whole body expressions of threat extends to stimuli that are presented outside of conscious awareness in healthy participants. To accomplish this, we combined the measurement of MEPs with a continuous flash suppression task. In experiment 1, participants were presented with images of neutral bodies, fearful bodies, or objects that were either perceived consciously or unconsciously, while single pulses of TMS were applied at different times after stimulus onset (200, 500, or 700 ms). In experiment 2 stimuli consisted of neutral bodies, angry bodies or objects, and pulses were applied at either 200 or 400 ms post stimulus onset. In experiment 1, there was a general effect of the time of stimulation, but no condition specific effects were evident. In experiment 2 there were no significant main effects, nor any significant interactions. Future studies need to look into earlier effects of MEP modulation by emotion body stimuli, specifically when presented outside of conscious awareness, as well as an exploration of other outcome measures such as intracortical facilitation.

Classical paintings may trigger pain and pleasure in the gendered brain

The human body is the most common object of pictorial representation in western art and its representations trigger a vast range of experiences from pain to pleasure. The goal of this study was to investigate brain activity triggered by paintings of male and female body images exemplifying conditions associated with pleasure or pain. Our findings show participant-general as well as gender specific brain activity for either the pain or the pleasure conditions. Although our participants were fully aware that they were viewing artworks, the inferior parietal lobule - known for its role in the perception of emotional body images - and the somatosensory cortex related to touch were selectively active for female body paintings in all participants in the pleasure conditions. As regards gender we observed that the sight of female bodies activated the subgenual anterior cingulate cortex in males, an area known to subserve autonomic arousal. In contrast, in females the sight of the male body activated reward and control related parts of the dorsal anterior cingulate cortex. This study supports the notion that some basic evolutionary processes operate when we view body images, also when they are cultural heritage paintings far removed from daily experience.