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Many perceptual studies focus on the brain's capacity to discriminate between stimuli. However, our normal experience of the world also involves integrating multiple stimuli into a single perceptual event. Neural mechanisms such as lateral inhibition are believed to enhance local differences between sensory inputs from nearby regions of the receptor surface. However, this mechanism would seem dysfunctional when sensory inputs need to be combined rather than contrasted. Here, we investigated whether the brain can

Alternating between static images of human bodies with an appropriate interstimulus interval (ISI) produces apparent biological motion. Here we investigate links between apparent biological motion and time perception. We presented two pictures of the initial and final positions of a human movement separated by six different ISIs. The shortest movement path between two positions was always biomechanically impossible. Participants performed two tasks: In an explicit task, participants judged whether they saw the longer, feasible movement path between the two postures, or the shorter, biomechanically impossible path. In an implicit task, participants judged the duration of a white square surrounding the picture sequence. At longer ISIs participants were more likely to see a longer, feasible movement path (explicit task) and underestimated the duration of body picture pairs, compared to trials displaying degraded body pictures (implicit task). We argue that perceiving apparent biological motion involves temporal binding of two static pictures into a continuous movement. Such temporal binding may be mediated by a top-down mechanism that produces a percept of biological motion in the absence of any retinal motion.

Self-face recognition is crucial for sense of identity and self-awareness. Finding self-face recognition disorders mainly in neurological and psychiatric diseases suggests that modifying sense of identity in a simple, rapid way remains a "holy grail" for cognitive neuroscience. By touching the face of subjects who were viewing simultaneous touches on a partner's face, we induced a novel illusion of personal identity that we call "enfacement": The partner's facial features became incorporated into the representation of the participant's own face. Subjects reported that morphed images of themselves and their partner contained more self than other only after synchronous, but not asynchronous, stroking. Therefore, we modified self-face recognition by means of a simple psychophysical manipulation. While accommodating gradual change in one's own face is an important form of representational plasticity that may help maintaining identity over time, the surprisingly rapid changes induced by our procedure suggest that sense of facial identity may be more malleable than previously believed. "Enfacement" correlated positively with the participant's empathic traits and with the physical attractiveness the participants attributed to their partners. Thus, personality variables modulate enfacement, which may represent a marker of the tendency to be social and may be absent in subjects with defective empathy.

Performing an action and observing it activate the same internal representations of action. The representations are therefore shared between self and other (shared representations of action, SRA). But what exactly is shared? At what level within the hierarchical structure of the motor system do SRA occur? Understanding the content of SRA is important in order to decide what theoretical work SRA can perform. In this paper, we provide some conceptual clarification by raising three main questions: (i) are SRA semantic or pragmatic representations of action?; (ii) are SRA sensory or motor representations?; (iii) are SRA representations of the action as a global unit or as a set of elementary motor components? After outlining a model of the motor hierarchy, we conclude that the best candidate for SRA is intentions in action, defined as the motor plans of the dynamic sequence of movements. We shed new light on SRA by highlighting the causal efficacy of intentions in action. This in turn explains phenomena such as inhibition of imitation.

The human brain may contain "mirror systems" allowing mental simulation of the sensorimotor states of others. Most research has focused on interpersonal sharing of motor representations, with relatively little focus on sensation. Here we show that viewing the body of another person significantly enhances the spatial resolution of touch on the corresponding body part. Thirty subjects judged the orientation of gratings presented to the index finger tip, either when viewing their own hand, when viewing a neutral object presented in approximately the same location, or when viewing the undisguised hand of a third person standing behind them. Orientation discrimination was significantly more accurate when viewing one's own body compared to when viewing a neutral object. The same enhancement effect was found when viewing another's body. Performance when viewing one's own body did not differ significantly from performance when viewing the body of another person. This result suggests a purely sensory interpersonal sharing of body representations. It also suggests a specifically interpersonal modulation of primary sensory functions within the brain.

Recent neuroscientific research has developed the concept of the embodied agent as a scientifically viable approach to the psychological concept of the self. Both the awareness of one's own actions and awareness of one's own body are necessary conditions for the experience of selfhood. The relative contributions of efferent and afferent information in self-awareness are yet to be fully understood. We review experimental evidence that highlights the phenomenological and functional differences between the "acting self" and the "sensory self." These differences may underlie the ubiquitous modulation of perception in voluntary action. We focus on three main research fields: somatosensory perception, time-awareness, and self-recognition. A series of experiments, designed so as to dissociate afferent from efferent information, are reviewed. As a whole the results suggest that intentional action functions as a general context for awareness, modulating the perception of one's own body. The "acting self," owner of the efferent information, modulates the phenomenal experience of the "sensory self" because of the intrinsically agentic nature of voluntary movement. Finally, it is suggested that this sense of agency is efferent-driven, originating from pre-action processes.

Although in many circumstances motor control and cognitive tasks can be performed simultaneously without significant decrement to either, there is evidence that performance is impaired under certain conditions. This study set out to investigate the effects of concomitant demands from cognitive and motor control tasks on patients recovering from acquired brain injury. In line with findings in ageing and physical rehabilitation we found significant interference from a motor tracking task on a simultaneously performed spatial reasoning task among seven subjects undergoing neurological rehabilitation, with lesser interference to a category generation and a number addition task. Tracking performance was also affected by concurrent performance of the spatial reasoning task. We suggest these effects may arise because motor control tasks become less automatic, and require increased cognitive processing resources, following acquired brain injury. This leads to potential interference with other cognitive tasks. Finally, we argue that this dual-task interference may be clinically relevant, as it may determine patients' responsiveness to rehabilitation.

Jeannerod (1981) proposed that prehensile movements involve two independent visuomotor channels that are responsible for hand transport and hand aperture. In many studies, the movement of a marker placed on the wrist has been used as an index of hand transport because wrist movement is unaffected by the movements of the digits responsible for hand aperture. In the present study, the spatial paths of the wrist, index finger, and thumb of 5 adults, each performing 50 reaching movements, were measured with a WATSMART movement tracking system, and their variability was analyzed. The measures of movement variability suggest that the motor system is more concerned with thumb position than with wrist position during hand transport. Although the wrist is a technically convenient index of hand transport, the thumb may be a more appropriate index from the point of view of motor control

Movement patterns may be complex in the sense of being composed of separable component tasks. These components may be coordinated at some level by the voluntary motor system, in order to combine tasks into appropriate actions. This study describes the use of task interference methods and phase transition curves (PTCs) to quantify task interference in tasks that may have two components. Comparison of the effects of task interference on the different components suggests how these may be coordinated during normal movements. These techniques can be applied to the coordination of hand transport and grasp aperture components in the reaching and grasping movements that people make in order to pick things up. Five subjects made cyclical movements that involved either composite reaching or just the transport or grasp component in isolation, according to condition. The cyclical movements were "perturbed" by requiring a rapid transport or grasping response to an auditory signal by the contralateral hand. The pattern of phase shifts, or changes in the timing of the cyclical task introduced by these perturbations was modeled using phase transition curves, in order to assess the nature of the functional linkage between transport and aperture in normal prehensile movement. The results suggest a functional linkage between grasp aperture and hand transport in normal prehensile movement.

Hertenstein, M. J., & Weiss, S. J. (Eds.) (2011). The handbook of touch: Neuroscience, behavioral, and health perspectives. New York: Springer Publishing Company. ISBN: 9780826121912. 520 pp. US $1...