Action verbs drive motor activity in adolescents but not in children.

In adults, grip force has reliably been used to investigate motor simulation evoked by linguistic action, suggesting that motor phenomena are linked to semantic action. The parietal and frontal lobes and their connexions are essential neural structures for pragmatic aspects of hand semantic action. In this perspective, the aim of the study was to determine the extent to which two groups of children and adolescents, classically characterized by degree of axonal myelination in fronto-parietal circuits, monitored the occurrence of nouns and manual action verbs presented auditorily while holding a grip force sensor. Differential effects of grip force were seen only in the adolescents when monitoring action verbs. Interestingly, weaker effects of grip force were modulated by noun targets only in the younger children, revealing that the ability to profit from a full semantic representation of verbs is not clearly established in the younger children. Grip force modulation was observed as early as 300 ms post target onset and peaked at the 500-750 ms window of observation for both groups. These group differences are in line with the motor simulation difficulties seen in younger children. The results may also indicate that degree of grip force in response to specific linguistic categories parallels the maturation of the parietal-frontal circuits, including the anterior intra-parietal area which plays a determining role in semantic aspects of hand action.

Assessing language-induced motor activity through Event Related Potentials and the Grip Force Sensor, an exploratory study.

The link between language processing and motor systems has been the focus of increasing interest to Cognitive Neuroscience. Some classical papers studying Event Related Potentials (ERPs) induced by linguistic stimuli have found differences in electrophysiological activity when comparing action and non-action words; more specifically, a bigger p200 for action words. On the other hand, a series of studies have validated the use of a grip force sensor (GFS) to measure language-induced motor activity during both isolated words and sentence listening, finding that action words induce an augmentation in the grip force around 250-300 ms after the onset of the stimulus. The purpose of the present study is to combine both techniques to assess if the p200 is related to the augmentation of the grip force measured by a GFS. We measured ERP and GFS changes elicited by listening to action and non-action words while maintaining an active grasping task. Our results show that both the p200 and the grip force around 300 ms are bigger for action words, compared to non-action. We also report a statistical correlation between these measures. To our knowledge, this is the first study where the electrophysiological activity and the changes in the grip force induced by auditory language processing are put together, opening new venues of interpretation for the sensorimotor interaction in language processing.

Contributions of the Left and the Right Hemispheres on Language-Induced Grip Force Modulation of the Left Hand in Unimanual Tasks.

Background andObjectives: Language-induced grip force modulation (LGFM) can be used to better understand the link between language and motor functions as an expression of embodied language. However, the contribution of each brain hemisphere to LGFM is still unclear. Using six different action verbs as stimuli, this study evaluated the grip force modulation of the left hand in a unimanual task to characterize the left and right hemispheres' contributions. Materials and Methods: Left-hand LGFM of 20 healthy and consistently right-handed subjects was evaluated using the verbs "to write", "to hold", "to pull" (left-lateralized central processing actions), "to draw", "to tie", and "to drive" (bihemispheric central processing actions) as linguistic stimuli. The time between the word onset and the first interval of statistical significance regarding the baseline (here as reaction time, RT) was also measured. Results: The six verbs produced LGFM. The modulation intensity was similar for the six verbs, but the RT was variable. The verbs "to draw", "to tie", and "to drive", whose central processing of the described action is bihemispheric, showed a longer RT compared to the other verbs. Conclusions: The possibility of a given manual action being performed by the left hand in consistent right-handers does not interfere with the occurrence of LGFM when the descriptor verb of this action is used as a linguistic stimulus, even if the possibility is remote. Therefore, LGFM seems to mainly rely on the left hemisphere, while a greater activation of the right hemisphere in action processing appears to slow the increase in LGFM intensity.

A simple technique to study embodied language processes: the grip force sensor.

Research in cognitive neuroscience has shown that brain structures serving perceptual, emotional, and motor processes are also recruited during the understanding of language when it refers to emotion, perception, and action. However, the exact linguistic and extralinguistic conditions under which such language-induced activity in modality-specific cortex is triggered are not yet well understood. The purpose of this study is to introduce a simple experimental technique that allows for the online measure of language-induced activity in motor structures of the brain. This technique consists in the use of a grip force sensor that captures subtle grip force variations while participants listen to words and sentences. Since grip force reflects activity in motor brain structures, the continuous monitoring of force fluctuations provides a fine-grained estimation of motor activity across time. In other terms, this method allows for both localization of the source of language-induced activity to motor brain structures and high temporal resolution of the recorded data. To facilitate comparison of the data to be collected with this tool, we present two experiments that describe in detail the technical setup, the nature of the recorded data, and the analyses (including justification about the data filtering and artifact rejection) that we applied. We also discuss how the tool could be used in other domains of behavioral research.

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. 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. 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. 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. 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.

Manual action verbs modulate the grip force of each hand in unimanual or symmetrical bimanual tasks.

Manual action verbs modulate the right-hand grip force in right-handed subjects. However, to our knowledge, no studies demonstrate the ability to accomplish this modulation during bimanual tasks nor describe their effect on left-hand behavior in unimanual and bimanual tasks. Using load cells and word playlists, we evaluated the occurrence of grip force modulation by manual action verbs in unimanual and symmetrical bimanual tasks across the three auditory processing phases. We found a significant grip force increase for all conditions compared to baseline, indicating the occurrence of modulation. When compared to each other, the grip force variation from baseline for the three phases of both hands in the symmetrical bimanual task was not different from the right-hand in the unimanual task. The left-hand grip force showed a lower amplitude for auditory phases 1 and 2 when compared to the other conditions. The right-hand grip force modulation became significant from baseline at 220 ms after the word onset in the unimanual task. This moment occurred earlier for both hands in bimanual task (160 ms for the right-hand and 180 for the left-hand). It occurred later for the left-hand in unimanual task (320 ms). We discuss the hypothesis that Broca's area and Broca's homologue area likely control the left-hand modulation in a unilateral or a bilateral fashion. These results provide new evidence for understanding the linguistic function processing in both hemispheres.

Effects of Excitatory Repetitive Transcranial Magnetic Stimulation of the P3 Point in Chronic Stroke Patients-Case Reports.

OBJECTIVE: To evaluate the effects of excitatory repetitive transcranial magnetic stimulation (rTMS) of the international 10⁻20 system P3 point (intraparietal sulcus region) in chronic patients with a frontal lesion and parietal sparing due to stroke on the impaired upper (UL) and lower limb (LL) as measured by the Fugl-Meyer Assessment (FMA). METHODS: Three patients (C1: 49.83/2.75, C2: 53.17/3.83, C3: 63.33/3.08-years-old at stroke/years post-stroke, respectively) received two weeks (five days/week) of rTMS at 10 Hz of P3. A patient was treated in similar conditions with a sham coil (S1: 56.58/4.33). Patients were evaluated before, after, and two months post-treatment (A1, A2, and A3, respectively). RESULTS: For LL, the scores of the motor function subsection of C1 and C3 as well as the sensory function of C2 increased by A2 and remained by A3. For UL, the score of the motor function of C2 and C3 also increased, but the score of C3 decreased by A3. The score of the range of motion subsection of C3 increased by the two follow-up evaluations. CONCLUSION: This study suggests excitatory rTMS over P3 may be of use for some chronic stroke patients, but these findings need to be verified in a future clinical trial.

A dissociation between real and simulated movements in Parkinson's disease.

Subcortical lesions have been simultaneously implicated in both real and simulated movement deficits. However, the analysis of the simulated opposition axis in precision grasping reveals that, in individuals with idiopathic bilateral Parkinson' disease motor imagery is impaired and that execution of overt movements is spared. This constitutes the first lesion observation congruent with the anatomical and functional dichotomy between real and simulated movements seen in experimental studies. These results underline the modality-specific nature of motor imagery and show that subcortical damage differentially impacts on motor activity.

Action relevance in linguistic context drives word-induced motor activity.

Many neurocognitive studies on the role of motor structures in action-language processing have implicitly adopted a "dictionary-like" framework within which lexical meaning is constructed on the basis of an invariant set of semantic features. The debate has thus been centered on the question of whether motor activation is an integral part of the lexical semantics (embodied theories) or the result of a post-lexical construction of a situation model (disembodied theories). However, research in psycholinguistics show that lexical semantic processing and context-dependent meaning construction are narrowly integrated. An understanding of the role of motor structures in action-language processing might thus be better achieved by focusing on the linguistic contexts under which such structures are recruited. Here, we therefore analyzed online modulations of grip force while subjects listened to target words embedded in different linguistic contexts. When the target word was a hand action verb and when the sentence focused on that action (John signs the contract) an early increase of grip force was observed. No comparable increase was detected when the same word occurred in a context that shifted the focus toward the agent's mental state (John wants to sign the contract). There mere presence of an action word is thus not sufficient to trigger motor activation. Moreover, when the linguistic context set up a strong expectation for a hand action, a grip force increase was observed even when the tested word was a pseudo-verb. The presence of a known action word is thus not required to trigger motor activation. Importantly, however, the same linguistic contexts that sufficed to trigger motor activation with pseudo-verbs failed to trigger motor activation when the target words were verbs with no motor action reference. Context is thus not by itself sufficient to supersede an "incompatible" word meaning. We argue that motor structure activation is part of a dynamic process that integrates the lexical meaning potential of a term and the context in the online construction of a situation model, which is a crucial process for fluent and efficient online language comprehension.

Word-induced postural changes reflect a tight interaction between motor and lexico-semantic representations.

A tight coupling between lexico-semantic access and motor control has been established on the basis of neuropsychological, neurophysiological, and behavioral evidence. For example, sensory and motor cortices have been shown to be active when subjects listen to words denoting bodily actions. Kinematic analyses of subjects' motor actions during the processing of linguistic stimuli provide further insights into the nature and time-course of this relationship. However, such studies have largely focused on individual body parts, in particular the upper limbs, thus neglecting the effect of language processing on lower or whole body representations. The present study bridges this gap by evaluating the interaction between linguistic processing and whole-body postural control during quiet standing. The results reveal a systematic influence of passive listening to action verbs, but not mental-state verbs, on measures of postural control, pointing to a clear and specific neural link between words conveying action concepts and whole-body motor functions.

Grip force reveals the context sensitivity of language-induced motor activity during "action words" processing: evidence from sentential negation.

BACKGROUND: Studies demonstrating the involvement of motor brain structures in language processing typically focus on 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. METHODOLOGY/PRINCIPAL FINDINGS: Participants listened to spoken action target words in either affirmative or negative sentences while holding a sensor in a precision grip. The participants were asked to count the sentences containing the name of a country to ensure attention. The grip force signal was recorded continuously. The action words elicited an automatic and significant enhancement of the grip force starting at approximately 300 ms after target word onset in affirmative sentences; however, no comparable grip force modulation was observed when these action words occurred in negative contexts. CONCLUSIONS/SIGNIFICANCE: 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 governed by the linguistic context and not vice versa.

Grip force is part of the semantic representation of manual action verbs.

Motor actions and action verbs activate similar cortical brain regions. A functional interference can be taken as evidence that there is a parallel treatment of these two types of information and would argue for the biological grounding of language in action. A novel approach examining the relationship between language and grip force is presented. With eyes closed and arm extended, subjects listened to words relating (verbs) or not relating (nouns) to a manual action while holding a cylinder with an integrated force sensor. There was a change in grip force when subjects heard verbs that related to manual action. Grip force increased from about 100 ms following the verb presentation, peaked at 380 ms and fell abruptly after 400 ms, signalling a possible inhibition of the motor simulation evoked by these words. These observations reveal the intimate relationship that exists between language and grasp and show that it is possible to elucidate online new aspects of sensorimotor interaction.

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.

Prehension movements in a patient (AC) with posterior parietal cortex damage and posterior callosal section.

Prehension movements of the right hand were recorded in a right-handed man (AC), with an injury to the left posterior parietal cortex (PPC) and with a section of the left half of the splenium. The kinematic analysis of AC's grasping movements in direct and perturbed conditions was compared to that of five control subjects. A novel effect in prehension was revealed--a hemispace effect--in healthy controls only. Movements to the left hemispace were faster, longer, and with a smaller grasp aperture; perturbation of both object position and distance resulted in the attenuation of the direction effect on movement time and the time to velocity peak, with a reverse pattern in the time to maximum grip aperture. Nevertheless, the correlation between transport velocity amplitude and grasp aperture remained stable in both perturbed and non-perturbed movements, reflecting the coordination between reaching and grasping in control subjects. In contrast, transport and grasp, as well as their coordination in both direct and perturbed conditions, were negatively affected by the PPC and splenium lesion in AC, suggesting that transport and grasp rely on two functionally identifiable subsystems.

Influencias ambientales sobre el desempeño cognitivo en la prueba A no B de una población de niños argentinos de entre 6 y 14 Meses / Environmental effects on cognitive performance in a 6 to 14 month-old child population

En el presente trabajo se plantea la utilización de la prueba A no B de Piaget con retardo como instrumento para diferenciar el desempeño cognitivo dependiente del desarrollo y maduración de sistemas cerebrales en poblaciones infantiles pertenecientes a ambientes de crianza diferenciados por sus características socioeconómicas (INDEC). Luego de la administración de dicha prueba a 250 niños de entre 6 y 14 meses, los resultados indican que el impacto de la insatisfacción de las necesidades básicas, tal como son definidas por el método de medición de pobreza NBI, afecta una medida del procesamiento cognitivo que incluye un componente de memoria de trabajo espacial involucrado con los circuitos ubicados en la corteza prefrontal dorsolateral.