Self-consciousness has mostly been approached by philosophical enquiry and not by empirical neuroscientific study, leading to an overabundance of diverging theories and an absence of data-driven theories. Using robotic technology, we achieved specific bodily conflicts and induced predictable changes in a fundamental aspect of self-consciousness by altering where healthy subjects experienced themselves to be (self-location). Functional magnetic resonance imaging revealed that temporo-parietal junction (TPJ) activity reflected experimental changes in self-location that also depended on the first-person perspective due to visuo-tactile and visuo-vestibular conflicts. Moreover, in a large lesion analysis study of neurological patients with a well-defined state of abnormal self-location, brain damage was also localized at TPJ, providing causal evidence that TPJ encodes self-location. Our findings reveal that multisensory integration at the TPJ reflects one of the most fundamental subjective feelings of humans: the feeling of being an entity localized at a position in space and perceiving the world from this position and perspective.
ABSTRACT:The choice of an adequate actuation method is a central issue in the development of any mechatronic device and strongly determines the dynamic performances of the system. This choice is particularly difficult for robotic systems working within a magnetic resonance (MR) environment because of the safety and compatibility constraints imposed by the high magnetic field, switching gradients, electromagnetic pulses, and sensitive measuring equipment involved. This article analyzes actuation methods for robotic systems to be used within a magnetic resonance environment, such as systems for diagnostic and interventional MRI, neuroscience studies during functional MRI, and diagnostic fMRI. In the case of functional MRI, actuation is also required during imaging, whereas current MR-compatible interventional systems are typically moved between imaging phases. Our analysis is based on a variety of actuation principles that we have tested both for MR compatibility and for the quality of force feedback that can be realized, including hydrostatic, belt, and cable transmissions as well as electrostatic and piezoelectric actuators. The results are completed with developments of other groups. A good solution to a given application often involves a combination of several actuation principles. A synthesis of characteristics and three comparative tables aid in the choice of an adequate actuation method for a given task or application.
In the perspective of the laser lightning rod, the ability of femtosecond filaments to trigger and to guide large scale discharges has been studied for several years. The present paper reports recent experimental results showing for the first time that filaments are able not only to trigger and guide but also to divert an electric discharge from its normal path. Laser filaments are also able to divert the spark without contact between laser and electrodes at large distance from the laser. A comparison between negative and positive discharge polarities also reveals important discrepancies in the guiding mechanism
Abstract-We are developing haptic interfaces compatible with functional Magnetic Resonance Imaging (fMRI) for neuroscience studies. The presented prototype with one rotary degree of freedom is actuated by a traveling wave ultrasonic motor operating under admittance control. Torque is sensed from the deflection of an elastic polymer probe via light intensity measurement over optical fibers. This concept allows us to place all electronic components outside the shielded MR room. Hence, the device can be used in conjunction with fMRI, providing torque and motion feedback simultaneously with imaging. Its compactness and simplicity facilitate the construction of multiple degree of freedom systems.
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