Interlimb transfer of unimanual grasping movement in upper limb amputees - A pilot study.

Background. Inter-hemispheric communication is necessary during uni- manual grip of an object (1). The right and left hands share a level of representation in the motor program that is common to both (2). It could be essential to take into consideration bi- hemispheric activity to adapt prosthesis of individuals with upper limb amputation.\ud Objective. To determine the relevance of the inter-hemispheric dependence in the programing and execution of uni-manual grip in individuals with upper limb amputation.\ud Methods. Five adults with amputation of the upper limb above and below the elbow participated in this study. Each participant was seated and asked to grab and lift an instrumented cylinder with the sound hand 15 times (Figure 1). The cylinder enabled to record in real time the apposition axis (AO) passing by the thrum, the centre of the cylinder and the first finger as well as the forces applied during the griping period of 2000 ms. The participants were assessed during the temporary (PP) and definitive (PD) phases of prosthesis fitting the after the amputation. Student t-tests were used to determine the effect of different prosthetic phases on the force and orientation of the griping hand.\ud Results\ud 1. A significant reduction (p<0.01) of the forces applied by the sound hand between the two prosthetic phase for 4/5 of the participants (Figure 2)\ud 2. Some changes in the gripping orientation when the amputated hand was dominant for 2/3 of the participants (Figure 3) 3. No changes in the gripping orientation when the amputated hand was not dominant\ud Conclusion. Grip programming and execution with sound hand:\ud 1. Change between two prosthetic fitting phases\ud 2. Depend on the inter-hemispheric transfer related to the force regardless on the amputated hand.\ud 3. Depend on the inter-hemispheric transfer related to the gripping orientation only when the amputated side is dominant.\ud Adjustments in griping force and orientation of the prosthesis depending on the grip correction of the sound hand might be respectively more necessary regardless of the amputated hand and when the amputated hand is dominant.\ud Because of the variability between participants concerning the side of amputation and manual dominance, other studies will be required to generalise these results

An instrumented cylinder measuring pinch force and orientation

Background: The function of a cylinder allowing simultaneous measurements of the opposition axis of the index finger and thumb of the hand and the magnitude of pinch force is described.\ud Methods: The apparatus is made of two half-cylinders that are bonded together through a 6-axis force/torque sensor and allows the measurement of 3D orthogonal forces and moments of force. The amplitude of the pinch force exerted on the cylinder by the fingers is defined as the resultant of the forces in the different axes. A software program was developed to measure the barycentre of the forces on the instrumented cylinder, allowing calculation of the angle of the opposition axis between the fingers and the location of the resulting pinch force on the cylinder, assuming that the pinch or grip forces are co-linear through the center of the cylinder.\ud In order to assess the validity and reliability of the measurements, the cylinder was mounted on a milling table and seven calibrated weights (from 100 to 500 g) were successively applied perpendicularly to a 9*9 matrix of sites separated by 1 cm. With the exception of the extreme lateral parts of the cylinder, the dispersion of the calculated vertical position of the resulting force was always within 1 mm of the application point, suggesting a high reliability of these measurements. In addition, the errors in the angles of the applied force were calculated and found to be less than 2 degree with no clear patterns of variation across the different locations of the cylinder.\ud Results: The usefulness of the cylinder is demonstrated by evaluating the pinch force and the opposition axis in six healthy subjects lifting the cylinder from the table using three different orientations of their right hand. The magnitude of the grip force was not significantly different across orientations (45, 22 and -22 degrees relative to the midline of the subject) suggesting that force grip is controlled.\ud Conclusion: From these results, it has been concluded that the cylinder is a valid, reliable and precise instrument that may prove useful for evaluating opposition axis and grip force in healthy and pathological populations

Online monitoring of the impact of language processing on motor processes: prehensile grip-force measures during passive listening of manual action.

A large number of recent behavioural studies have established that processing linguistic descriptions of motor actions affect overt motor behaviour. For instance, when participants are asked to make sensibility judgments on sentences that describe action toward the body (“Mark gave the book to yo

The role of the temporal cortex in long-latency auditory evoked potentials

Existen aun controversias sobre los posibles generadores de los potenciales evocados auditivos de larga latencia (PEAL). Algunas evidencias sugieren que la cortez auditiva juega un rol en la definición de dichos potenciales. A partir de esta hipótesis nos propusimos investigar la existencia de eventuales modificaciones en el procesamiento de la información auditiva, cuando ese área de la corteza está alterada, tal como sucede en la epilepsia temporal. Se estudió una población de 19 pacientes con diagnóstico de epilepsia temporal primaria, en base a los datos clínicos y EEG y comparamos los resultados, con una población control de 17 sujetos, y también con un grupo control de 4 pacientes con epilepsia jacksoniana que recibía medicación anticonvulsivante similar a la del grupo probando. En todos los casos se hicieron potenciales auditivos de corta latencia (PEAT) y PEAL. Los PEAL, se exploraron a partir del estímulo monoaural de un tono de 1000 Hz de 50 ms de duración, a 50 db. El intervalo interestímulo fue de 1 s. La actividad eléctrica cerebral fue recogida por electrodos colocados en Cz, F3 y F4, con referencia a la región mastoidea. Se promediaron 50 estímulos sobre una base de tiempo de 500 ms; se utilizó una banda de filtro de 125 a 1 Hz. Se analizaron las latencias y amplitudes de los componentes de los 2 tipos de potenciales evocados estudiados. En los PEAT no se hallaron diferencias entre controles y pacientes. Para el análisis de los resultados de los PEAL dividimos la poblacion de enfermos en 3 grupos, epilepsia temporal derecha (D), epilepsia temporal izquierda (I) y epilepsia temporal, en la que no pudo determinarse el lado (N). En los pacientes (D) se observo un retardo en la latencia al estimular el oido izquierdo en los componentes P1 (F4 X87+-10.4 ms) y N1 (F4 X 122.33 +- 6.1 ms; Cz X 170.75 +- 18.8 ms). En los enfermos (I) al estimular el oido derecho, el retardo se evidencio en el componente N1 (Cz X 134.8 +-22.9 ms). En el grupo (N) no se observaron alteraciones significativas. Estos resultados sugieren que la corteza temporal participa en la génesis de este tipo de potenciales

Simulation Modifies Prehension: Evidence for a Conjoined Representation of the Graspable Features of an Object and the Action of Grasping It

Movement formulas, engrams, kinesthetic images and internal models of the body in action are notions derived mostly from clinical observations of brain-damaged subjects. They also suggest that the prehensile geometry of an object is integrated in the neural circuits and includes the object's graspable characteristics as well as its semantic properties. In order to determine whether there is a conjoined representation of the graspable characteristics of an object in relation to the actual grasping, it is necessary to separate the graspable (low-level) from the semantic (high-level) properties of the object. Right-handed subjects were asked to grasp and lift a smooth 300-g cylinder with one hand, before and after judging the level of difficulty of a “grasping for pouring” action, involving a smaller cylinder and using the opposite hand. The results showed that simulated grasps with the right hand exert a direct influence on actual motor acts with the left hand. These observations add to the evidence that there is a conjoined representation of the graspable characteristics of the object and the biomechanical constraints of the arm

Grip Force Reveals the Context Sensitivity of Language-Induced Motor Activity during “Action Words

Studies demonstrating the involvement of motor brain structures in language processing typically focus on \ud time windows beyond the latencies of lexical-semantic access. Consequently, such studies remain inconclusive regarding whether motor brain structures are recruited directly in language processing or through post-linguistic conceptual imagery. In the present study, we introduce a grip-force sensor that allows online measurements of language-induced motor activity during sentence listening. We use this tool to investigate whether language-induced motor activity remains constant or is modulated in negative, as opposed to affirmative, linguistic contexts. Our findings demonstrate that this simple experimental paradigm can be used to study the online crosstalk between language and the motor systems in an ecological and economical manner. Our data further confirm that the motor brain structures that can be called upon during action word processing are not mandatorily involved; the crosstalk is asymmetrically\ud governed by the linguistic context and not vice versa

Environmental Effects on Cognitive Performance in a 6 to 14 Month-Old Child Population.

The use of the A not B task with delays is presented as an instrument for the evaluation of cognitive performance depending on the prefrontal dorsolateral cerebral cortex. This task was admnistered to 250 children from 6 to 14 months old, from different socio-economical rearing environments (as classified by the Instituto Nacional de Estadística y Censo, INDEC). Results showed an impact of environmental variables on child performance: as a group children from homes providing unsatisfied basic needs homes were less efficient than those who were reared in homes in which their basic needs were satisfied

Grasp It Loudly! Supporting Actions with Semantically Congruent Spoken Action Words

Evidence for cross-talk between motor and language brain structures has accumulated over the past several years. However, while a significant amount of research has focused on the interaction between language perception and action, little attention has been paid to the potential impact of language production on overt motor behaviour

The Grasping Side of Odours

Background: Research on multisensory integration during natural tasks such as reach-to-grasp is still in its infancy. Crossmodal links between vision, proprioception and audition have been identified, but how olfaction contributes to plan and control reach-to-grasp movements has not been decisively shown. We used kinematics to explicitly test the influence of olfactory stimuli on reach-to-grasp movements. Methodology/Principal Findings: Subjects were requested to reach towards and grasp a small or a large visual target (i.e., precision grip, involving the opposition of index finger and thumb for a small size target and a power grip, involving the flexion of all digits around the object for a large target) in the absence or in the presence of an odour evoking either a small or a large object that if grasped would require a precision grip and a whole hand grasp, respectively. When the type of grasp evoked by the odour did not coincide with that for the visual target, interference effects were evident on the kinematics of hand shaping and the level of synergies amongst fingers decreased. When the visual target and the object evoked by the odour required the same type of grasp, facilitation emerged and the intrinsic relations amongst individual fingers were maintained. Conclusions/Significance: This study demonstrates that olfactory information contains highly detailed information able to elicit the planning for a reach-to-grasp movement suited to interact with the evoked object. The findings offer a substantia

The cognitive neuroscience of prehension: recent developments

Prehension, the capacity to reach and grasp, is the key behavior that allows humans to change their environment. It continues to serve as a remarkable experimental test case for probing the cognitive architecture of goal-oriented action. This review focuses on recent experimental evidence that enhances or modifies how we might conceptualize the neural substrates of prehension. Emphasis is placed on studies that consider how precision grasps are selected and transformed into motor commands. Then, the mechanisms that extract action relevant information from vision and touch are considered. These include consideration of how parallel perceptual networks within parietal cortex, along with the ventral stream, are connected and share information to achieve common motor goals. On-line control of grasping action is discussed within a state estimation framework. The review ends with a consideration about how prehension fits within larger action repertoires that solve more complex goals and the possible cortical architectures needed to organize these actions