The invisible body:the neural mechanisms of non-conscious and conscious processing of emotional bodies

How do we process emotions expressed by bodies when we don’t realize we are looking at them? This research made body postures invisible for participants by using the “continuous flash suppression” method. It turned out that processing bodily emotions is very different from processing faces, and is different across emotions (e.g. neutral, fearful, angry), both when participants consciously see them and when they see them outside their awareness. The research also looked in detail at the brain activity with the 7T MRI scanner, and found that understanding bodily actions involves a large network across the brain. This research provides insights in the way we understand actions and emotions

Unconscious fearful body perception enhances discrimination of conscious anger expressions under continuous flash suppression

The continuous flash suppression (CFS) paradigm is increasingly used to study unconscious visual perception. Our goal was to use CFS and to to compare the results with previous findings from patients with brain lesions, and studies of healthy participants. We used an emotion discrimination task and bilaterally presented whole-body postures expressing fear or anger, rendering the stimuli invisible in either one of the visual fields. We found that the CFS presentation did not yield the classical redundant target effect of response facilitation when the unconsciously seen stimuli had congruent emotions; instead we found a facilitation effect in reaction times by body stimuli of incongruent emotions, especially by the unconscious fearful body facilitating discrimination of conscious angry body. Our results with healthy participants showed similarities to hemianopia patients without blindsight, but not to blindsight or neglect patients, indicating that unconscious visual processing is not a single phenomenon, but is likely to involve multiple mechanisms, processes and brain regions. Further studies are necessary to validate the facilitation effect of fearful bodies on other tasks, and to study the neural substrates of this effect

Data for: Gradual relation between perceptual awareness, recognition and pupillary responses to social threat

Project investigating perceptual awareness of social threat with behavioral and pupil measures. Contents include both the raw and processed behavioral and pupil size data

One step beyond! The conjunction-bias between non-spatial (Color) and spatial Grouping cues over approximate number perception extends to Symmetry and Connectedness.

Humans and animals share the cognitive ability to quickly extract approximate number information from sets. Main psychophysical models suggest that approximate numerosity relies on segmented units, which can be affected by Gestalt rules. Indeed, arrays with spatial grouping cues, such as connectedness, closure, and even symmetry, are underestimated compared to ungrouped arrays with the same low-level features. Recent evidence suggests that also non-spatial cues, such as color-similarity, trigger numerosity underestimation. However, in natural vision, several grouping cues may coexist in the same stimulus. Notably, conjunction of grouping cues (e.g., color + closure) reduces perceived numerosity following an additive rule. Here we investigated the effect of two Gestalt cues, connectedness and symmetry, over numerosity perception both in isolation and, critically, in conjunction with color. Participants performed a comparison-task between a reference and a test stimulus varying in numerosity. In Experiment 1, test stimuli contained two isolated groupings (connectedness or color-similarity), a conjunction (connectedness and color-similarity), and a neutral condition (no groupings). We found that the point of subjective equality (PSE) was higher in both isolated grouping conditions compared to the neutral condition. Importantly, in the conjunction condition, the biases from single grouping cues added linearly, resulting in a numerosity underestimation equal to the sum of the isolated biases. In Experiment 2 we found that conjunction of symmetry & color followed the same rule. These findings strongly suggest that both spatial and non-spatial isolated cues affect numerosity perception. Crucially, we show that their conjunction-effect extends to Symmetry and Connectedness

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 5Hz, and their 2nd and 3rd harmonics, which included the 10Hz frequency typically used in most of the CFS studies. We found that the suppression of stimulus awareness was stronger under 4, 6 and 8Hz than 10Hz. 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 5Hz 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

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

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

Gradual relation between perceptual awareness, recognition and pupillary responses to social threat

There is substantial evidence supporting the processing of affective stimuli outside of conscious awareness in both healthy individuals and brain-damaged patients. However, the methodologies used to assess awareness are still a matter of debate, with also implications for dichotomous or gradual theories. In two experiments, we investigated how social threat is processed in healthy participants by combining the continuous flash suppression paradigm and the perceptual awareness scale, a fine-grained measure of perceptual awareness. Our findings revealed a gradual relationship between emotional recognition and perceptual awareness, with higher recognition sensitivity for fearful than angry bodies across all visual awareness levels, except during perceptual unawareness where performance was at chance level. Interestingly, angry body expressions were suppressed for a shorter duration than neutral and fearful ones. Furthermore, pupil dilation responses were influenced by affective expression, suppression duration and perceptual awareness level. In conclusion, our results highlight a gradual relationship between behavioral and pupillary responses and perceptual awareness, which is further influenced by the specific stimulus category being processed. In addition, our results illustrate that certain experimental choices, such as stimulus type or the method used to assess awareness, are important factors to be considered in consciousness studies

Does the visual word form area split in bilingual readers? A millimeter-scale 7T fMRI study

In expert readers, a brain region known as the visual word form area (VWFA) is highly sensitive to written words, exhibiting a posterior-to-anterior gradient of increasing sensitivity to orthographic stimuli whose statistics match those of real words. Using high-resolution 7T fMRI, we ask whether, in bilingual readers, distinct cortical patches specialize for different languages. In 21 English-French bilinguals, unsmoothed 1.2 mm fMRI revealed that the VWFA is actually composed of several small cortical patches highly selective for reading, with a posterior-to-anterior word similarity gradient, but with near-complete overlap between the two languages. In 10 English-Chinese bilinguals, however, while most word-specific patches exhibited similar reading specificity and word-similarity gradients for reading in Chinese and English, additional patches responded specifically to Chinese writing and, surprisingly, to faces. Our results show that the acquisition of multiple writing systems can indeed tune the visual cortex differently in bilinguals, sometimes leading to the emergence of cortical patches specialized for a single language