Differential influence of hands posture on mental rotation of hands and feet in left and right handers

The representation of the body in the brain is continuously updated with regard to peripheral factors such as position or movement of body parts. In the present study, we investigated the effects of arm posture on the mental rotation of hands and feet. Sixteen right-handed and ten left-handed participants verbally judged the laterality of visually presented pictures of hands and feet in two different postural conditions. In one condition they placed their right hand on their right knee and their left hand behind the back, in the other condition the hand position was reversed. For right-handed participants response times for the laterality judgment of right hands increased when participants kept their right hand behind the back. This was not found for images of the left hand nor for images of the feet. For the left-handed participants, there was no effect of arm posture on hand or feet stimulus judgments. Thus, the body-part posture effect on mental rotation was found to be specific for the side and the body part for which the posture was modified only in right-handed participants, but it was absent for left-handed participants. For both samples, we also found a progressive disruption of the mental rotation function depending on the view from which the body parts were seen (i.e. dorsal, thumb/big toe, palm/plantar, little finger/toe). Posture and view effects on body parts representations are discussed with respect to proprioception, handedness, visual familiarity and the influence of anatomical joint constraints on motor imager

Multi-Sensory and Sensorimotor Foundation of Bodily Self-Consciousness – An Interdisciplinary Approach

Scientific investigations on the nature of the self have so far focused on high-level mechanisms. Recent evidence, however, suggests that low-level bottom-up mechanisms of multi-sensory integration play a fundamental role in encoding specific components of bodily self-consciousness, such as self-location and first-person perspective (Blanke and Metzinger, 2009). Self-location and first-person perspective are abnormal in neurological patients suffering from out-of-body experiences (Blanke et al., 2004), and can be manipulated experimentally in healthy subjects by imposing multi-sensory conflicts (Lenggenhager et al., 2009). Activity of the temporo-parietal junction (TPJ) reflects experimentally induced changes in self-location and first-person perspective (Ionta et al., 2011), and dysfunctions in TPJ are causally associated with out-of-body experiences (Blanke et al., 2002). We argue that TPJ is one of the key areas for multi-sensory integration of bodily self-consciousness, that its levels of activity reflect the experience of the conscious “I” as embodied and localized within bodily space, and that these mechanisms can be systematically investigated using state of the art technologies such as robotics, virtual reality, and non-invasive neuroimaging

Anatomically plausible illusory posture affects mental rotation of body parts

During mental rotation (MR) of body parts, people internally simulate the movement of their corresponding body segments. These sensory-motor mechanisms render MR sensitive to proprioceptive information (e.g., posture). Similar mechanisms can alter illusory hand ownership following synchronous visuotactile stimulation (e.g., the rubber hand illusion [RHI]). In the present study, we first showed that illusory ownership for a fake hand can also be induced when the posture of the fake hand (palm-up) does not correspond with the subject's physical hand posture (palm-down). Then we tested whether illusory ownership for a fake hand in such a posture impacts the MR of hands carried out immediately and repeatedly after the RHI. The results showed that MR was altered for the view corresponding to the fake hand's posture, but not for other views. Additionally, these effects depended on illusory ownership, as only synchronous visuotactile stimulation was found to lead to these changes, characterized by a modulation of the rotation-dependent profile of MR response times. These findings show that similar sensory-motor mechanisms are recruited during the MR of hands and illusory hand ownership manipulated through multisensory mismatch, and that bottom-up visuotactile stimulation interferes with high-level imagery processe

Are We the Robots? : Man-Machine Integration

We experience and interact with the world through our body. The founding father of computer science, Alan Turing, correctly realized that one of the most important features of the human being is the interaction between mind and body. Since the original demonstration that electrical activity of the cortical neurons can be employed to directly control a robotic device, the research on the so-called Brain-Machine Interfaces (BMIs) has impressively grown. For example, current BMIs dedicated to both experimental and clinical studies can translate raw neuronal signals into computational commands to reproduce reaching or grasping in artificial actuators. These developments hold promise for the restoration of limb mobility in paralyzed individuals. However, as the authors review in this chapter, before this goal can be achieved, several hurdles have to be overcome, including developments in real-time computational algorithms and in designing fully implantable and biocompatible devices. Future investigations will have to address the best solutions for restoring sensation to the prosthetic limb, which still remains a major challenge to full integration of the limb into the user's self-image

Differential influence of hands posture on mental rotation of hands and feet in left and right handers

The representation of the body in the brain is continuously updated with regard to peripheral factors such as position or movement of body parts. In the present study, we investigated the effects of arm posture on the mental rotation of hands and feet. Sixteen right-handed and ten left-handed participants verbally judged the laterality of visually presented pictures of hands and feet in two different postural conditions. In one condition they placed their right hand on their right knee and their left hand behind the back, in the other condition the hand position was reversed. For right-handed participants response times for the laterality judgment of right hands increased when participants kept their right hand behind the back. This was not found for images of the left hand nor for images of the feet. For the left-handed participants, there was no effect of arm posture on hand or feet stimulus judgments. Thus, the body-part posture effect on mental rotation was found to be specific for the side and the body part for which the posture was modified only in right-handed participants, but it was absent for left-handed participants. For both samples, we also found a progressive disruption of the mental rotation function depending on the view from which the body parts were seen (i.e. dorsal, thumb/big toe, palm/plantar, little finger/toe). Posture and view effects on body parts representations are discussed with respect to proprioception, handedness, visual familiarity and the influence of anatomical joint constraints on motor imagery

Insights and Perspectives on Sensory-Motor Integration and Rehabilitation

The present review focuses on the flow and interaction of somatosensory-motor signals in the central and peripheral nervous system. Specifically, where incoming sensory signals from the periphery are processed and interpreted to initiate behaviors, and how ongoing behaviors produce sensory consequences encoded and used to fine-tune subsequent actions. We describe the structure-function relations of this loop, how these relations can be modeled and aspects of somatosensory-motor rehabilitation. The work reviewed here shows that it is imperative to understand the fundamental mechanisms of the somatosensory-motor system to restore accurate motor abilities and appropriate somatosensory feedback. Knowledge of the salient neural mechanisms of sensory-motor integration has begun to generate innovative approaches to improve rehabilitation training following neurological impairments such as stroke. The present work supports the integration of basic science principles of sensory-motor integration into rehabilitation procedures to create new solutions for sensory-motor disorders

Mental Imagery for Full and Upper Human Bodies: Common Right Hemisphere Activations and Distinct Extrastriate Activations

The processing of human bodies is important in social life and for the recognition of another person's actions, moods, and intentions. Recent neuroimaging studies on mental imagery of human body parts suggest that the left hemisphere is dominant in body processing. However, studies on mental imagery of full human bodies reported stronger right hemisphere or bilateral activations. Here, we measured functional magnetic resonance imaging during mental imagery of bilateral partial (upper) and full bodies. Results show that, independently of whether a full or upper body is processed, the right hemisphere (temporo-parietal cortex, anterior parietal cortex, premotor cortex, bilateral superior parietal cortex) is mainly involved in mental imagery of full or partial human bodies. However, distinct activations were found in extrastriate cortex for partial bodies (right fusiform face area) and full bodies (left extrastriate body area). We propose that a common brain network, mainly on the right side, is involved in the mental imagery of human bodies, while two distinct brain areas in extrastriate cortex code for mental imagery of full and upper bodie

Editorial: Psychology and Neuropsychology of Perception, Action, and Cognition

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Egocentric and object-based transformations in the laterality judgement of human and animal faces and of non-corporeal objects

Mental rotation of body parts is influenced by specific sensory-motor information, and may be performed using an egocentric (subject-based) or an object-based mental transformation. Neurologically healthy volunteers were asked to verbally judge the laterality of visually presented human face, owl face and front of a car with a black patch over one eye/headlight, presented in one of eight orientations. Subjects may or may not have their head held in a head brace. The transformation used to solve the task was assessed with a questionnaire. Response times were non-monotonical at 180 degrees for the object-based group, but not for the group using egocentric transformation. Having head movement constrained by the use of a head brace ("fixed") or not ("moving") did not influence performance. Within the two groups, no differences were found between the three types of stimuli. Hence, the response profile for mental rotation of human faces and face-like stimuli depended on the type of mental spatial transformation used to solve the task, independently from the possibility to move the head and from the kind of stimuli processed