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Working memory is composed of different processes and encompasses not only the temporary storage of information but also its manipulation in order to perform complex cognitive activities. During childhood, one of these manipulation processes, namely active controlled retrieval, improves significantly between the age of 6 to 10, suggesting that the neuronal network supporting this function undergoes substantial maturational changes. The present study examined the neural activity of 14 healthy children and 14 adults while performing an active controlled retrieval task. Results showed differences in brain activity according to active controlled retrieval in a 300-500 ms window corresponding to the retrieval period. Active controlled retrieval was associated with a P3b-like potential in parietal sites for both children and adults. In fronto-central sites, children demonstrated a "N400 like" potential associated with active retrieval processing. These results are discussed in terms of maturational development., (Copyright © 2018 Elsevier Inc. All rights reserved.)

The aim of this study was to examine the relationship between motor proficiency and academic achievement in 7 years-old children. A mediating model in which the relation between motor proficiency and academic achievement is mediated by cognitive ability was tested. Participants included 152 children from the longitudinal study Jeunes enfants et leurs milieux de vie (Young Children and their Environments). Motor proficiency was evaluated with the Bruininks-Oseretsky Test of Motor Proficiency (BOT2), cognitive ability with the Wechsler Intelligence Scale for Children-Fourth Edition (WISC-IV) and academic achievement with the Wechsler Individual Achievement Test II (WIAT II). Results showed that motor proficiency, cognitive ability and academic achievement were positively correlated with each other. A structural equation modeling analysis revealed that motor proficiency had a positive effect on academic achievement through an indirect path via cognitive ability. These results highlight the fundamental importance of motor skills in children's academic achievement in early school years., (Copyright © 2017 Elsevier B.V. All rights reserved.)

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., (Copyright © 2013 Elsevier Ireland Ltd. All rights reserved.)

The aim of this study was to examine the development of active controlled memory retrieval in children. Active retrieval is an effortful retrieval required to disambiguate information stored in memory. Brain imaging studies and monkey experiments have shown that the ventrolateral prefrontal cortex (VLPFC) is specifically engaged in this retrieval in both adult humans and monkeys. Three groups of 6-, 8-, and 11-year-old children and adults were tested on an active retrieval task. Results showed a marked difference in performance between 6-year olds, who made more errors and had longer response time, and 8- and 11-year olds, who had performance similar to adults. These results provide evidence that the VLPFC and the network supporting its top-down modulation undergo substantial maturational changes between 6 and 8 years old, giving children better active control of visual memory., (Copyright © 2012 Wiley Periodicals, Inc.)

One of the most important postural challenges in daily life is to continuously correct the destabilizing torque due to gravity that accelerates the body further away from the upright position. This study examined children's (7.9 years old) (n=7) and adults' (n=10) capacity to generate continuous corrective torque during a progressive perturbation. The experimental task was to maintain an upright quiet standing on a platform that gradually and slowly toes-down tilted to a maximum of 14° without visual cues. The vertical forces applied on the platform and the electromyograms from the tibialis anterior and the gastrocnemius were measured. The results showed that children had a different postural response to the perturbation than adults. When the platform was stationary before the inclination, children shifted their body weight backward whereas adults had a more balanced distribution of their weight. During the inclination, children applied a stronger forward force, suggesting a larger postero-anterior displacement of their body weight. Muscular activities were higher in children for both the tibialis anterior and the gastrocnemius, and their tibialis anterior activation profile was different. In conclusion, this study showed that in children aged from 7 to 10 years old neuromuscular responses were not mature enough to generate continuous postural corrective torque in response to the perturbation., (Copyright © 2012 IPEM. Published by Elsevier Ltd. All rights reserved.)

In the ventrolateral frontal lobe of the human brain there is a distinct entity, cytoarchitectonic area 44 (Broca's area), which is crucial in speech production. There has been controversy over whether monkeys possess an area comparable to human area 44. We have addressed this question in the macaque monkey by combining quantitative architectonic analysis of the cortical areas within the ventrolateral frontal region with electrophysiological recording of neuron activity and electrical intracortical microstimulation. Here we show that, immediately in front of the ventral part of the agranular premotor cortical area 6, there is a distinct cortical area that is architectonically comparable to human area 44 and that this monkey area 44 is involved with the orofacial musculature. We suggest that area 44 might have evolved originally as an area exercising high-level control over orofacial actions, including those related to communicative acts, and that, in the human brain, area 44 eventually also came to control certain aspects of the speech act.

The present study examined the role of the prefrontal cortex in retrieval processing using functional magnetic resonance imaging in human subjects. Ten healthy subjects were scanned while they performed a task that required retrieval of specific aspects of visual information. In order to examine brain activity specifically associated with retrieval, we designed a task that had retrieval and control conditions that were perfectly matched in terms of depth of encoding, decision making and postretrieval monitoring and differed only in terms of whether retrieval was required. In the retrieval condition, based on an instructional cue, the subjects had to retrieve either the particular stimulus that was previously presented or its location. In the control condition, the cue did not instruct retrieval but shared with the instructional cues the function of alerting the subjects of the impending test phase. The comparison of activity between the retrieval and control conditions demonstrated a significant and selective increase in activity related to retrieval processes within the ventrolateral prefrontal cortical region, more specifically within area 47/12. These activity increases were bilateral but stronger in the right hemisphere. The present study by strictly controlling the level of encoding, postretrieval monitoring, and decision making has demonstrated a specific increase in the ventrolateral prefrontal region that could be clearly related to active retrieval processing, i.e. the active selection of particular stored visual representations.

The aim of this study was to determine whether relatively long-term changes in skin friction induced by a pharmacological blockade of sweat excretion would alter the grip forces applied to objects of a variety of different surface textures and frictions. Five men and three women were asked to lift the vertically mounted armature of a linear motor between the thumb and index finger and to hold it against an opposing force for 2 s. A 1.0-kHz tone indicated to the subject that the manipulandum had been correctly positioned between the upper and lower position limits. The linear motor generated a 2.5-N force tangential to the skin surface simulating an object weighing approximately 250 g. Three different polyamide plastic surfaces (either smooth or etched with 1.0 mm high Braille beads evenly spaced at 2- or 3-mm intervals) contacted the fingers in these experiments. Subjects lifted and held in a precision grip one of the three surfaces for blocks of ten consecutive trials, but the order of presentation of the three different textures was varied to offset the effect of expectancy. On a second block of ten trials the subjects were requested to release the object slowly to measure the ratio of the grip force normal to the grasped surface to the tangential load force at the moment of slip. This ratio or its inverse provided the coefficient of friction or the slip ratio for a particular subject and surface condition. Twelve hours prior to a second recording session all subjects placed transdermal patches of 1.5 mg scopolamine behind each ear to reduce palmar sweating by blocking the muscarinic receptors of exocrine sweat glands. The subjects were re-tested following procedures that were identical to the first session. Scopolamine significantly reduced the friction of the skin on the smooth and 2-mm beaded surfaces, but the friction of the 3-mm beaded texture was unaffected. Scopolamine also caused subjects to increase both the peak and static grip forces for all the textures including the 3-mm beaded surface, suggesting that for two of the three surfaces they were responding to the increased slipperiness of the skin due to reduced sweat production.

Two monkeys were trained to use the thumb and forefinger to lift and hold an instrumented apparatus within a narrow position window for 1 s. The device was equipped to measure the position and the grip and lifting forces exerted by the animal. On blocks of trials the weight and surface texture could be varied or a force-pulse perturbation could be systematically delivered 750 ms after the object entered the window. If unopposed, the perturbation would displace the hand from the position window, and in preparation for this perturbation the monkeys either increased their grip force before the perturbation or raised the object higher within the position window. Two clearly separated clusters of cells in the medial wall of the frontal lobe were found to be active in relation to the task. One group of cells (n = 115) was located in the caudal and medial part of area 6, in the supplementary motor area (SMA), and the other (n = 92) was located in the ventral bank of the cingulate sulcus (CMAv), in area 23c. In each area, neurons were characterized by their sensorimotor features clearly related to the hand in addition to their modulated activity in the task. In the SMA, 71% (42 of 59) of the neurons tested for receptive fields responded to peripheral and mainly proprioceptive stimulation, and 71% of them (30 of 42) received inputs from the hand. In the CMAv, 77% (48 of 62) of the neurons responded to peripheral proprioceptive stimulation, and 77% (37 of 48) exhibited receptive fields originating from the hand. Intracortical microstimulation applied to 43 sites in the SMA evoked discrete hand movements at 12 loci, whereas in the CMAv hand movements were observed at 8 of 27 sites tested with an average threshold of > 15 microA. A strong similarity was observed between the SMA and CMAv neurons in their sensorimotor features as well as the modulation of their activity in relation to the prehension task. In both areas the activity was poorly related to grip force and significant correlation with peak grip force was observed for only 9 and 7% of the CMAv and SMA neurons, respectively. In the SMA only five cells exhibited increased activity before the perturbation and in the CMAv no changes in activity were found despite the presence of clear preparatory increases in grip force in anticipation of the perturbation. The perturbation evoked reflexlike excitation of 38% (25 of 65) of the neurons in the CMAv and 28% (20 of 71) of the cells in the SMA; these cells were similar in magnitude and latency (approximately 50 ms) in both areas. In both the SMA and CMAv, most of the neurons increased their firing rate < 200 ms before the grip force onset and the overlap in the distribution of neuronal response times suggests a parallel activation of the SMA and CMAv neurons during the prehension task.