Tool use imagery triggers tool incorporation in the body schema

Baccarini M, Martel M, Cardinali L, Sillan O, Farnè A, Roy AC. Tool use imagery triggers tool incorporation in the body schema. Frontiers in Psychology. 2014;2014(5): 492.Tool-use has been shown to modify the way the brain represents the metrical characteristics of the effector controlling the tool. For example, the use of tools that elongate the physical length of the arm induces kinematic changes affecting selectively the transport component of subsequent free-hand movements. Although mental simulation of an action is known to involve -to a large extent- the same processes as those at play in overt motor execution, whether tool-use imagery can yield similar effects on the body representation remains unknown. Mentally simulated actions indeed elicit autonomic physiological responses and follow motor execution rules that are comparable to those associated with the correspondent overt performance. Therefore, here we investigated the effects of the mental simulation of actions performed with a tool on the body representation by studying subsequent free-hand movements. Subjects executed reach to grasp movements with their hand before and after an imagery task performed with either a tool elongating their arm length or, as a control, with their hand alone. Two main results were found: First, in agreement with previous studies, durations of imagined movements performed with the tool and the hand were similarly affected by task difficulty. Second, kinematics of free-hand movements was affected after tool-use imagery, but not hand-use imagery, in a way similar to that previously documented after actual tool-use. These findings constitute the first evidence that tool-use imagery is sufficient to affect the representation of the user's arm

Inter-hemispheric integration of tactile-motor responses across body parts

In simple detection tasks, reaction times are faster when stimuli are presented to the visual field or side of the body ipsilateral to the body part used to respond. This advantage, the crossed-uncrossed difference (CUD), is thought to reflect inter-hemispheric interactions needed for sensorimotor information to be integrated between the two cerebral hemispheres. However, it is unknown whether the tactile CUD is invariant when different body parts are stimulated. The most likely structure mediating such processing is thought to be the corpus callosum (CC). Neurophysiological studies have shown that there are denser callosal connections between regions that represent proximal parts of the body near the body midline and more sparse connections for regions representing distal extremities. Therefore, if the information transfer between the two hemispheres is affected by the density of callosal connections, stimuli presented on more distal regions of the body should produce a greater CUD compared to stimuli presented on more proximal regions. This is because interhemispheric transfer of information from regions with sparse callosal connections will be less efficient, and hence slower. Here, we investigated whether the CUD is modulated as a function of the different body parts stimulated by presenting tactile stimuli unpredictably on body parts at different distances from the body midline (i.e., Middle Finger, Forearm, or Forehead of each side of the body). Participants detected the stimulus and responded as fast as possible using either their left or right foot. Results showed that the magnitude of the CUD was larger on the finger (~2.6 ms) and forearm (~1.8 ms) than on the forehead (~-0.9 ms). This result suggests that the interhemispheric transfer of tactile stimuli varies as a function of the strength of callosal connections of the body parts

Anonimato del Donante y Derecho a Conocer: un Difìcil Equilibrio (Donor Anonimity and Right to Know: a Challenging Balancing)

This article examines the tension among the anonymity of the gamete donor and the right of the child to know his origin, following the latest trend of the European legal systems. The analysis of legal systems that recognize such a right to children conceived through donated gametes allows us to think further on the hypotheses, now more extended, which consider that traditional arguments for secrecy are out-dated. In this regard, the article also challenges the different treatment granted to adopted children and donor gamete children by legal systems such as the Spanish one. Beyond the possible conflicting rights of children, donors and parents, arguments provided by anonymity supporters, such as moral damages resulting from disclosure or the possible link between disclosure and the decrease in the number of donors, should be also taken into account. However, these arguments require absolute empirical evidence which is not currently conclusive. Alternatively, disclosure of the identity of the donor, once the child has reached enough maturity, is seen as a solution to be studied in detail, as long as it does not lead to the establishment of parentage links. The article suggests that this solution is consistent with the needs of donor families, and with a major trend in family law supporting the right to know one&rsquo;s genetic origin, dissociated from biological and legal parentage spheres. El trabajo plantea la compatibilidad entre la garant&iacute;a de anonimato del donante de gametos y el derecho del nacido a conocer sus or&iacute;genes. A partir del an&aacute;lisis de los ordenamientos que reconocen este derecho a las personas concebidas mediante gametos donados, el trabajo pretende profundizar en las hip&oacute;tesis, cada vez m&aacute;s extendidas, que consideran que las fundamentaciones tradicionales para mantener el secreto han perdido valor y, a su vez, indagar en si est&aacute; justificado el diferente trato que en esta materia dispensan, al concebido mediante gametos donados y al adoptado, legislaciones como la espa&ntilde;ola. M&aacute;s all&aacute; de los derechos en conflicto (de hijos, donantes y padres), deben ser tenidos en cuenta los argumentos que podr&iacute;an legitimar las opciones basadas en el anonimato, como el posible da&ntilde;o derivado de revelar la informaci&oacute;n sobre el propio origen o la posible relaci&oacute;n entre la supresi&oacute;n del anonimato y la disminuci&oacute;n del n&uacute;mero de donantes. Ahora bien, estos argumentos requieren de una absoluta evidencia emp&iacute;rica que no es concluyente al d&iacute;a de hoy. La posibilidad de conocer la identidad del donante de gametos, una vez el nacido ha alcanzado la madurez suficiente, sin que ello deba conducir necesariamente al establecimiento de v&iacute;nculos legales de filiaci&oacute;n, se perfila como una soluci&oacute;n que debe ser explorada en profundidad, puesto que es coherente con la realidad de las familias creadas a partir del recurso a t&eacute;cnicas de reproducci&oacute;n asistida heter&oacute;logas y con la tendencia, cada vez mayor en derecho de familia, hacia el reconocimiento del derecho a conocer el origen gen&eacute;tico, disoci&aacute;ndolo de otras esferas de filiaci&oacute;n biol&oacute;gica y legal. DOWNLOAD THIS PAPER FROM SSRN: https://ssrn.com/abstract=2782321</p

Extending peripersonal space representation without tool-use: evidence from a combined behavioral-computational approach

Stimuli from different sensory modalities occurring on or close to the body are integrated in a multisensory representation of the space surrounding the body, i.e., peripersonal space (PPS). PPS dynamically modifies depending on experience, e.g., it extends after using a tool to reach far objects. However, the neural mechanism underlying PPS plasticity after tool use is largely unknown. Here we use a combined computational-behavioral approach to propose and test a possible mechanism accounting for PPS extension. We first present a neural network model simulating audio-tactile representation in the PPS around one hand. Simulation experiments showed that our model reproduced the main property of PPS neurons, i.e., selective multisensory response for stimuli occurring close to the hand. We used the neural network model to simulate the effects of a tool-use training. In terms of sensory inputs, tool use was conceptualized as a concurrent tactile stimulation from the hand, due to holding the tool, and an auditory stimulation from the far space, due to tool-mediated action. Results showed that after exposure to those inputs, PPS neurons responded also to multisensory stimuli far from the hand. The model thus suggests that synchronous pairing of tactile hand stimulation and auditory stimulation from the far space is sufficient to extend PPS, such as after tool-use. Such prediction was confirmed by a behavioral experiment, where we used an audio-tactile interaction paradigm to measure the boundaries of PPS representation. We found that PPS extended after synchronous tactile-hand stimulation and auditory-far stimulation in a group of healthy volunteers. Control experiments both in simulation and behavioral settings showed that the same amount of tactile and auditory inputs administered out of synchrony did not change PPS representation. We conclude by proposing a simple, biological-plausible model to explain plasticity in PPS representation after tool-use, which is supported by computational and behavioral data