Others' Actions Reduce Crossmodal Integration in Peripersonal Space

Multisensory integration across the menstrual cycle

Evidence suggests that spatial processing changes across time in naturally cycling women, which is likely due to neuromodulatory effects of steroid hormones. Yet, it is unknown whether crossmodal spatial processes depend on steroid hormones as well. In the present experiment, the crossmodal congruency task was used to assess visuo-tactile interactions in naturally cycling women, women using hormonal contraceptives and men. Participants adopted either a crossed or uncrossed hands posture. It was tested whether a postural effect of hand crossing on multisensory interactions in the crossmodal congruency task is modulated by women's cycle phase. We found that visuotactile interactions changed according to cycle phase. Naturally cycling women showed a significant difference between the menstrual and the luteal phase for crossed, but not for uncrossed hands postures. The two control groups showed no test sessions effects. Regression analysis revealed a positive relation between estradiol levels and the size of crossmodal congruency effects (CCE), indicating that estradiol seems to have a neuromodulatory effect on posture processing.

A shared representation of the space near oneself and others in the human premotor cortex

Interactions between people require shared high-level cognitive representations of action goals, intentions, and mental states, but do people also share their representation of space? The human ventral premotor (PMv) and parietal cortices contain neuronal populations coding for the execution and observation of actions, analogous to the mirror neurons identified in monkeys. This neuronal system is tuned to the location of the acting person relative to the observer and the target of the action. Therefore, it can be theorized that the observer's brain constructs a low-level, body-centered representation of the space around others similar to one's own peripersonal space representation. Single-cell recordings have reported that parietal visuotactile neurons discharge for objects near specific parts of a monkey's own body and near the corresponding body parts of another individual. In humans, no neuroimaging study has investigated this issue. Here, we identified neuronal populations in the human PMv that encode the space near both one's own hand and another person's hand. The shared peripersonal space representation could support social interactions by coding sensory events, actions, and cognitive processes in a common spatial reference frame.

Being moved by the self and others: influence of empathy on self-motion perception

BACKGROUND

The observation of conspecifics influences our bodily perceptions and actions: Contagious yawning, contagious itching, or empathy for pain, are all examples of mechanisms based on resonance between our own body and others. While there is evidence for the involvement of the mirror neuron system in the processing of motor, auditory and tactile information, it has not yet been associated with the perception of self-motion.

METHODOLOGY/PRINCIPAL FINDINGS

We investigated whether viewing our own body, the body of another, and an object in motion influences self-motion perception. We found a visual-vestibular congruency effect for self-motion perception when observing self and object motion, and a reduction in this effect when observing someone else's body motion. The congruency effect was correlated with empathy scores, revealing the importance of empathy in mirroring mechanisms.

CONCLUSIONS/SIGNIFICANCE

The data show that vestibular perception is modulated by agent-specific mirroring mechanisms. The observation of conspecifics in motion is an essential component of social life, and self-motion perception is crucial for the distinction between the self and the other. Finally, our results hint at the presence of a "vestibular mirror neuron system".

A satisficing and bricoleur approach to sensorimotor cognition

In this manuscript I present a set of neural processing principles and evolutionary constraints that should be taken into account in the characterization of sensorimotor cognition. I review evidence supporting the choice of the set of principles, and then I assess how such principles apply to two cases, object perception-action and peripersonal space. The aim is to emphasize the importance of focusing cognitive models on how evolution shapes functional paths to adaptations, as well as to adopt fitness maximization analyses of cognitive functions. Such an approach contrasts with the widespread reverse-engineering assumption that the neural system comprises a set of specialized circuits designed to comply with its assumed functions. The evidence presented in the manuscript points to the fact that neural systems should not be seen as a seat of optimal processes and circuits addressing particular problems in sensorimotor cognition, but as a set of satisficing and tinkered components, mostly not addressing the problems that are supposed to solve, but solving them as secondary effects of the engaged processes. I conclude with a corollary of the challenges lying ahead of the proposed approach.

Massive somatic deafferentation and motor deefferentation of the lower part of the body impair its visual recognition: a psychophysical study of patients with spinal cord injury

Embodied cognition theories postulate that perceiving and understanding the body states of other individuals are underpinned by the neural structures activated during first-hand experience of the same states. This suggests that one's own sensorimotor system may be used to identify the actions and sensations of others. Virtual and real brain lesion studies show that visual processing of body action and body form relies upon neural activity in the ventral premotor and the extrastriate body areas, respectively. We explored whether visual body perception may also be altered in the absence of damage to the above cortical regions by testing healthy controls and spinal cord injury (SCI) patients whose brain was unable to receive somatic information from and send motor commands to the lower limbs. Participants performed tasks investigating the ability to visually discriminate changes in the form or action of body parts affected by somatosensory and motor disconnection. SCI patients showed a specific, cross-modal deficit in the visual recognition of the disconnected lower body parts. This deficit affected both body action and body form perception, hinting at a pervasive influence of ongoing body signals on the brain network dedicated to visual body processing. Testing SCI patients who did or did not practise sports allowed us to test the influence of motor practice on visual body recognition. We found better upper body action recognition in sport-practising SCI patients, indicating that motor practice is useful for maintaining visual representation of actions after deafferentation and deefferentation. This may be a potential resource to be exploited for rehabilitation.