Infants’ Somatotopic Neural Responses to Seeing Human Actions: I’ve Got You under My Skin

Human infants rapidly learn new skills and customs via imitation, but the neural linkages between action perception and production are not well understood. Neuroscience studies in adults suggest that a key component of imitation–identifying the corresponding body part used in the acts of self and other–has an organized neural signature. In adults, perceiving someone using a specific body part (e.g., hand vs. foot) is associated with activation of the corresponding area of the sensory and/or motor strip in the observer’s brain–a phenomenon called neural somatotopy. Here we examine whether preverbal infants also exhibit somatotopic neural responses during the observation of others’ actions. 14-month-old infants were randomly assigned to watch an adult reach towards and touch an object using either her hand or her foot. The scalp electroencephalogram (EEG) was recorded and event-related changes in the sensorimotor mu rhythm were analyzed. Mu rhythm desynchronization was greater over hand areas of sensorimotor cortex during observation of hand actions and was greater over the foot area for observation of foot actions. This provides the first evidence that infants’ observation of someone else using a particular body part activates the corresponding areas of sensorimotor cortex. We hypothesize that this somatotopic organization in the developing brain supports imitation and cultural learning. The findings connect developmental cognitive neuroscience, adult neuroscience, action representation, and behavioral imitation.     

Pain-related somatosensory evoked potentials following CO2 laser stimulation of foot in man

Since our previous study of pain somatosensory evoked potentials (SEPs) following CO₂ laser stimulation of the hand dorsum could not clarify whether the early cortical component NI was generated from the primary somatosensory cortex (SI) or the secondary somatosensory cortex (SII) or both, the scalp topography of SEPs following CO₂ laser stimulation of the foot dorsum was studied in 10 normal subjects and was compared with that of the hand pain SEPs and the conventional SEPs following electrical stimulation of the posterior tibial nerve recorded in 8 and 6 of the 10 subjects, respectively. Three components (N1, N2 and P2) were recorded for both foot and hand pain SEPs. N1 of the foot pain SEPs was maximal at the midline electrodes (Cz or CPz) in all data where that potential was recognized, but the potential field distribution was variable among subjects and even between two sides within the same subject. N1 of the hand pain SEPs was maximal at the contralateral central or midtemporal electrode. The scalp distribution of N2 and P2, however, was not different between the foot and hand pain SEPs. The mean peak latency of N1 following stimulation of foot and hand was found to be 191 msec and 150 msec, respectively, but there was no significant difference in the interpeak latency of Nl-N2 between foot and hand stimulation. It is therefore concluded that NI of the foot pain SEPs is generated mainly from the foot area of SI. The variable scalp distribution of the N7 component of the foot pain SEPs is likely due to an anatomical variability among subjects and even between sides.     

The role of the striatum in adaptation learning: a computational model

To investigate the functional role of the striatum in visuo-motor adaptation, we extend the DIRECT-model for visuo-motor reaching movements formulated by Bullock et al.(J Cogn Neurosci 5:408–435,1993) through two parallel loops, each modeling a distinct contribution of the cortico–cerebellar–thalamo–cortical and the cortico–striato–thalamo–cortical networks to visuo-motor adaptation. Based on evidence of Robertson and Miall(Neuroreport 10(5): 1029–1034, 1999), we implement the function of the cortico–cerebellar–thalamo–cortical loop as a module that gradually adapts to small changes in sensorimotor relationships. The cortico–striato–thalamo–cortical loop on the other hand is hypothesized to act as an adaptive search element, guessing new sensorimotor-transformations and reinforcing successful guesses while punishing unsuccessful ones. In a first step, we show that the model reproduces trajectories and error curves of healthy subjects in a two dimensional center-out reaching task with rotated screen cursor visual feedback. In a second step, we disable learning processes in the cortico–striato– thalamo–cortical loop to simulate subjects with Parkinson’s disease (PD), and show that this leads to error curves typical of subjects with PD. We conclude that the results support our hypothesis, i.e., that the role of the cortico–striato–thalamo–cortical loop in visuo-motor adaptation is that of an adaptive search element.     

The Effects of Visual Control and Distance in Modulating Peripersonal Spatial Representation

In the presence of vision, finalized motor acts can trigger spatial remapping, i.e., reference frames transformations to allow for a better interaction with targets. However, it is yet unclear how the peripersonal space is encoded and remapped depending on the availability of visual feedback and on the target position within the individual’s reachable space, and which cerebral areas subserve such processes. Here, functional magnetic resonance imaging (fMRI) was used to examine neural activity while healthy young participants performed reach-to-grasp movements with and without visual feedback and at different distances of the target from the effector (near to the hand–about 15 cm from the starting position–vs. far from the hand–about 30 cm from the starting position). Brain response in the superior parietal lobule bilaterally, in the right dorsal premotor cortex, and in the anterior part of the right inferior parietal lobule was significantly greater during visually-guided grasping of targets located at the far distance compared to grasping of targets located near to the hand. In the absence of visual feedback, the inferior parietal lobule exhibited a greater activity during grasping of targets at the near compared to the far distance. Results suggest that in the presence of visual feedback, a visuo-motor circuit integrates visuo-motor information when targets are located farther away. Conversely in the absence of visual feedback, encoding of space may demand multisensory remapping processes, even in the case of more proximal targets.     

Palmar and Plantar Pressure While Walking on a Horizontal Ladder and Single Pole in <Emphasis Type="Italic">Macaca fuscata</Emphasis>

To investigate biomechanical function in the hand and foot during quadrupedal locomotion in nonhuman primates, physical anthropologists and primatologists measure the pressure under them. We collected hand and foot pressure data while a Japanese macaque (Macaca fuscata), a semiterrestrial anthropoid, walked on 2 different simulated arboreal substrates, a horizontal ladder and a single pole, to explore differences in hand and foot use between the 2 substrates. The ladder rungs were perpendicular to the craniocaudal axis of the subject, and the pole was parallel to the subject’s craniocaudal axis. We tested the hypothesis that the pole was a more challenging substrate for the macaque than the ladder. Focusing on a diagonal sequence, diagonal couplets gait, we calculated gait characteristics and computed mean peak-pressure images of the hand and foot for each substrate from individual peak images via translation registration. We found several substrate differences that supported the hypothesis. The Japanese macaque walked at significantly slower speeds when traveling on the pole than on the ladder. Slower travel speed on the pole suggests that the Japanese macaque needed a wider support base to maintain balance on this substrate. Mean peak-pressure images suggest that the ladder invoked a more stepping-like behavior, but the pole invoked a more grasping-like behavior, especially of the foot. We show that the hand and foot use of the Japanese macaque would be adaptable to biomechanical challenges posed by different substrates.     

What experimental experience affects dogs’ comprehension of human communicative actions?

Studies of dogs report that individuals reliably respond to the goal-directed communicative actions (e.g., pointing) of human experimenters. All of these studies use some version of a multi-trial approach, thereby allowing for the possibility of rapid learning within an experimental session. The experiments reported here ask whether dogs can respond correctly to a communicative action based on only a single presentation, thereby eliminating the possibility of learning within the experimental context. We tested 173 dogs. For each dog reaching our test criteria, we used a single presentation of six different goal-directed actions within a session, asking whether they correctly follow to a target goal (container with concealed food) a (1) distal hand point, (2) step toward one container, (3) hand point to one container followed by step toward the other, (4) step toward one container and point to the other, (5) distal foot point with the experimenter's hands free, and (6) distal foot point with the experimenter's hands occupied. Given only a single presentation, dogs selected the correct container when the experimenter hand pointed, foot pointed with hands occupied, or stepped closer to the target container, but failed on the other actions, despite using the same method. The fact that dogs correctly followed foot pointing with hands occupied, but not hands free, suggests that they are sensitive to environmental constraints, and use this information to infer rational, goal-directed action. We discuss these results in light of the role of experience in recognizing communicative gestures, as well as the significance of coding criteria for studies of canine competence.     

The influence of locomotor training on dynamic balance during steady-state walking post-stroke

Slow walking speed and lack of balance control are common impairments post-stroke. While locomotor training often improves walking speed, its influence on dynamic balance is unclear. The goal of this study was to assess the influence of a locomotor training program on dynamic balance in individuals post-stroke during steady-state walking and determine if improvements in walking speed are associated with improved balance control. Kinematic and kinetic data were collected pre- and post-training from seventeen participants who completed a 12-week locomotor training program. Dynamic balance was quantified biomechanically (peak-to-peak range of frontal plane whole-body angular-momentum) and clinically (Berg-Balance-Scale and Dynamic-Gait-Index). To understand the underlying biomechanical mechanisms associated with changes in angular-momentum, foot placement and ground-reaction-forces were quantified. As a group, biomechanical assessments of dynamic balance did not reveal any improvements after locomotor training. However, improved dynamic balance post-training, observed in a sub-group of 10 participants (i.e., Responders), was associated with a narrowed paretic foot placement and higher paretic leg vertical ground-reaction-force impulse during late stance. Dynamic balance was not improved post-training in the remaining seven participants (i.e., Non-responders), who did not alter their foot placement and had an increased reliance on their nonparetic leg during weight-bearing. As a group, increased walking speed was not correlated with improved dynamic balance. However, a higher pre-training walking speed was associated with higher gains in dynamic balance post-training. These findings highlight the importance of the paretic leg weight bearing and mediolateral foot placement in improving frontal plane dynamic balance post-stroke.     

Pointing errors in immediate and delayed conditions in unilateral optic ataxia

The present paper provides an analysis of the pointing errors of a patient with unilateral optic ataxia (O.K.) following right hemispheric damage, revealing the type of errors related tothe use of the contralesional hand and/or to the reaching of targets located in the contralesional visual field. In addition, comparison between immediate and delayed pantomime pointing allow testing of whether pointing deficits of this patient are specific to real-time visuo-motor control and, subsequently, whether delay could improve his pointing performance. The results show different patterns in the four hand-field combinations. The following conclusion can be drawn from the results of the delayed condition. In the case of patient O. K., the delay reduced the pointing variability for both hands in the left visual field but not in the right visual field. However, the pointing biases did not improve accordingly. As in healthy subjects, target locations tended to be coded in memory with a bias directed toward the fixation point. These results are discussed and contrasted with respect to those previously obtained in the literature in patients with bilateral optic ataxia.     

Generalization of Dexterous Manipulation Is Sensitive to the Frame of Reference in Which It Is Learned

Studies have shown that internal representations of manipulations of objects with asymmetric mass distributions that are generated within a specific orientation are not generalizable to novel orientations, i.e., subjects fail to prevent object roll on their first grasp-lift attempt of the object following 180° object rotation. This suggests that representations of these manipulations are specific to the reference frame in which they are formed. However, it is unknown whether that reference frame is specific to the hand, the body, or both, because rotating the object 180° modifies the relation between object and body as well as object and hand. An alternative, untested explanation for the above failure to generalize learned manipulations is that any rotation will disrupt grasp performance, regardless if the reference frame in which the manipulation was learned is maintained or modified. We examined the effect of rotations that (1) maintain and (2) modify relations between object and body, and object and hand, on the generalizability of learned two-digit manipulation of an object with an asymmetric mass distribution. Following rotations that maintained the relation between object and body and object and hand (e.g., rotating the object and subject 180°), subjects continued to use appropriate digit placement and load force distributions, thus generating sufficient compensatory moments to minimize object roll. In contrast, following rotations that modified the relation between (1) object and hand (e.g. rotating the hand around to the opposite object side), (2) object and body (e.g. rotating subject and hand 180°), or (3) both (e.g. rotating the subject 180°), subjects used the same, yet inappropriate digit placement and load force distribution, as those used prior to the rotation. Consequently, the compensatory moments were insufficient to prevent large object rolls. These findings suggest that representations of learned manipulation of objects with asymmetric mass distributions are specific to the body- and hand-reference frames in which they were learned.     

人肠道病毒71型动物模型研究进展

人肠道病毒71型是婴幼儿手足口病的致病原之一,其严重的并发症可导致神经系统疾病,甚至死亡,是近期威胁中国儿童健康的因素之一。目前尚无临床疫苗可以预防该病毒感染,而EV71的动物模型是进行致病机理、疫苗评价和药物等研究的基础。本文对EV71的两种常用动物模型：小鼠和猕猴（Macaca mulatta）模型进行了描述,并对其在研究中的应用给与概括,为研究者选择合适的动物模型提供了依据。     

Increased and Imbalanced dNTP Pools Symmetrically Promote Both Leading and Lagging Strand Replication Infidelity

The fidelity of DNA replication requires an appropriate balance of dNTPs, yet the nascent leading and lagging strands of the nuclear genome are primarily synthesized by replicases that differ in subunit composition, protein partnerships and biochemical properties, including fidelity. These facts pose the question of whether imbalanced dNTP pools differentially influence leading and lagging strand replication fidelity. Here we test this possibility by examining strand-specific replication infidelity driven by a mutation in yeast ribonucleotide reductase, rnr1-Y285A, that leads to elevated dTTP and dCTP concentrations. The results for the CAN1 mutational reporter gene present in opposite orientations in the genome reveal that the rates, and surprisingly even the sequence contexts, of replication errors are remarkably similar for leading and lagging strand synthesis. Moreover, while many mismatches driven by the dNTP pool imbalance are efficiently corrected by mismatch repair, others are repaired less efficiently, especially those in sequence contexts suggesting reduced proofreading due to increased mismatch extension driven by the high dTTP and dCTP concentrations. Thus the two DNA strands of the nuclear genome are at similar risk of mutations resulting from this dNTP pool imbalance, and this risk is not completely suppressed even when both major replication error correction mechanisms are genetically intact.     

Predicted threshold against backward balance loss following a slip in gait

The purpose of this study was to use a 7-link, moment-actuated human model to predict, at liftoff of the trailing foot in gait, the threshold of the center of mass (COM) velocity relative to the base of support (BOS) required to prevent backward balance loss during single stance recovery from a slip. Five dynamic optimization problems were solved to find the minimum COM velocities that would allow the simulation to terminate with the COM above the BOS when the COM started 0.25, 0.5, 0.75, 1.0, and 1.25 foot lengths behind the heel of the stance foot (i.e., behind the BOS). The initial joint angles of the model were based on averaged data from experimental trials. Foot-ground contact was modeled using 16 visco-elastic springs distributed under the stance foot. Slipping was modeled by setting the sliding coefficient of friction of these springs to 0.02. The forward velocity of the COM necessary to avoid a backward balance loss is nearly two times larger under slip conditions under non-slip conditions. The predicted threshold for backward balance loss following a slip agreed well with experimental data collected from 99 young adults in response to 927 slips during walking. In all trials in which a subject's COM had a velocity below the predicted threshold, the subject's recovery foot landed posterior to the slipping foot as predicted. Finally, combining experimental data with optimization, we verified that the 7-link model could more accurately predict gait stability than a 2-link model.     

The versatile temporoparietal fascial flap: adaptability to a variety of composite defects

The unique properties of the temporoparietal fascial flap (TPFF) offer adaptability in reconstruction of a variety of composite defects. The broad, thin sheet of vascularized tissue may be transferred alone or as a carrier of subjacent bone or overlying skin and scalp. As a pedicled flap, it is ideal for defects of the orbital, malar, mandibular, and mastoid regions. As a free-tissue transfer, the large vessels and lack of bulk find broad utility in reconstruction of the extremities. This flap is our choice for reconstruction of the dorsal hand and non-weight-bearing surfaces of the foot. A viscous gliding surface decreases friction for tendon excursion. The thin contour is aesthetically superior to thicker flaps, allowing unmodified footwear or gloves. The pliable fascia convolutes into surface defects (e.g., bone craters) or drapes over skeletal frameworks (e.g., ear cartilage). The rich capillary network offers nutrition to saucerized bone, cartilage or tendon grafts, and overlying skin grafts. The geometry of the skull lends to fabrication of membranous bone for complex facial puzzles. The donor site is well disguised by hair growth. Twelve cases performed over a 2-year period demonstrate the versatility of this flap. These include complex foot reconstruction, ear and scalp avulsion, shotgun wound of the cheek and orbit, posttraumatic jaw recontouring, chronic osteomyelitis of the hand and foot, and acute resurfacing of dorsal hand with tendon reconstruction.     

屯堡人7项不对称行为特征

在贵州省安顺市对359例屯堡人(男145例,女214例)中学生的7项不对称行为特征(扣手、利手、叠臂、叠腿、利足、起步类型和优势眼)进行了调查。研究结果显示:1)屯堡人除叠臂左型率高于右型率外,其他6项不对称行为特征均为右型率高于左型率;2)屯堡人7项不对称行为特征的出现率均无性别差异;3)与其他族群比较,屯堡人利足右型率和叠臂右型率中等,叠腿右型率和扣手右型率高;4)屯堡人两两不对称行为中,扣手与利手、扣手与叠臂、扣手与叠腿、叠腿与起步相关,利手、利足、起步三种行为彼此相关。     

Lateralisation in birds of prey: adaptive and phylogenetic considerations

Lateralisation, the different use of one or other side or appendix of the body, is basically determined by brain asymmetry which, in turn, is likely to be due to adaptive reasons. Several studies have been carried out on birds in general. However, birds of prey in particular, although they are very good candidates, have not been investigated from the sensory lateralisation point of view. In fact, many species scan for prey while perched and capture terrestrial prey with the feet, having at the same time the obvious necessity to keep their balance. This paper, therefore, investigates the existence of some sort of lateralisation in several species of both Falconiformes and Strigiformes temporarily in captivity. Attention is given to: (a) the direction of body rotation when perceiving a sound stimulus from behind the body and (b) the use of the feet when grasping a terrestrial prey. Lateralisation was found to be clearly present in both types of tests, although with some difference in its expression. In fact, almost every species tested rotated its body anti-clockwise, i.e. to the left, both in the first test and in repeated tests, with no noticeable difference between Falconiformes and Strigiformes. Also prey grasping showed a preferential use of one foot. Falconiformes preferred clearly to grasp the prey with one foot only in both the first test and in subsequent ones. Strigiformes, on the other hand, preferred using both feet, although a not insignificant proportion of individuals used one foot. Only the little owl seemed to have the tendency to prefer to use the right foot only, in a similar manner to Falconiformes. In fact, this bird is the most "diurnal" owl species among those tested, suggesting that lateralisation in footedness might be affected by adaptive constraints more than by phylogenetic similarities. Lateralisation, therefore, seems to be very widespread among birds of prey. Preferential use of the right foot also appears to be a general habit, and this is probably connected to the use of left hemisphere when manipulating food items.     

Learned Manipulation at Unconstrained Contacts Does Not Transfer across Hands

Recent studies about sensorimotor control of the human hand have focused on how dexterous manipulation is learned and generalized. Here we address this question by testing the extent to which learned manipulation can be transferred when the contralateral hand is used and/or object orientation is reversed. We asked subjects to use a precision grip to lift a grip device with an asymmetrical mass distribution while minimizing object roll during lifting by generating a compensatory torque. Subjects were allowed to grasp anywhere on the object’s vertical surfaces, and were therefore able to modulate both digit positions and forces. After every block of eight trials performed in one manipulation context (i.e., using the right hand and at a given object orientation), subjects had to lift the same object in the second context for one trial (transfer trial). Context changes were made by asking subjects to switch the hand used to lift the object and/or rotate the object 180° about a vertical axis. Therefore, three transfer conditions, hand switch (HS), object rotation (OR), and both hand switch and object rotation (HS+OR), were tested and compared with hand matched control groups who did not experience context changes. We found that subjects in all transfer conditions adapted digit positions across multiple transfer trials similar to the learning of control groups, regardless of different changes of contexts. Moreover, subjects in both HS and HS+OR group also adapted digit forces similar to the control group, suggesting independent learning of the left hand. In contrast, the OR group showed significant negative transfer of the compensatory torque due to an inability to adapt digit forces. Our results indicate that internal representations of dexterous manipulation tasks may be primarily built through the hand used for learning and cannot be transferred across hands.     

Learning by Observation: Insights from Williams Syndrome

Observing another person performing a complex action accelerates the observer’s acquisition of the same action and limits the time-consuming process of learning by trial and error. Observational learning makes an interesting and potentially important topic in the developmental domain, especially when disorders are considered. The implications of studies aimed at clarifying whether and how this form of learning is spared by pathology are manifold. We focused on a specific population with learning and intellectual disabilities, the individuals with Williams syndrome. The performance of twenty-eight individuals with Williams syndrome was compared with that of mental age- and gender-matched thirty-two typically developing children on tasks of learning of a visuo-motor sequence by observation or by trial and error. Regardless of the learning modality, acquiring the correct sequence involved three main phases: a detection phase, in which participants discovered the correct sequence and learned how to perform the task; an exercise phase, in which they reproduced the sequence until performance was error-free; an automatization phase, in which by repeating the error-free sequence they became accurate and speedy. Participants with Williams syndrome beneficiated of observational training (in which they observed an actor detecting the visuo-motor sequence) in the detection phase, while they performed worse than typically developing children in the exercise and automatization phases. Thus, by exploiting competencies learned by observation, individuals with Williams syndrome detected the visuo-motor sequence, putting into action the appropriate procedural strategies. Conversely, their impaired performances in the exercise phases appeared linked to impaired spatial working memory, while their deficits in automatization phases to deficits in processes increasing efficiency and speed of the response. Overall, observational experience was advantageous for acquiring competencies, since it primed subjects’ interest in the actions to be performed and functioned as a catalyst for executed action.     

Fooling the Eyes: The Influence of a Sound-Induced Visual Motion Illusion on Eye Movements

The question of whether perceptual illusions influence eye movements is critical for the long-standing debate regarding the separation between action and perception. To test the role of auditory context on a visual illusion and on eye movements, we took advantage of the fact that the presence of an auditory cue can successfully modulate illusory motion perception of an otherwise static flickering object (sound-induced visual motion effect). We found that illusory motion perception modulated by an auditory context consistently affected saccadic eye movements. Specifically, the landing positions of saccades performed towards flickering static bars in the periphery were biased in the direction of illusory motion. Moreover, the magnitude of this bias was strongly correlated with the effect size of the perceptual illusion. These results show that both an audio-visual and a purely visual illusion can significantly affect visuo-motor behavior. Our findings are consistent with arguments for a tight link between perception and action in localization tasks.     

The Impact of Augmented Information on Visuo-Motor Adaptation in Younger and Older Adults

Background

Adjustment to a visuo-motor rotation is known to be affected by ageing. According to previous studies, the age-related differences primarily pertain to the use of strategic corrections and the generation of explicit knowledge on which strategic corrections are based, whereas the acquisition of an (implicit) internal model of the novel visuo-motor transformation is unaffected. The present study aimed to assess the impact of augmented information on the age-related variation of visuo-motor adjustments.

Methodology/Principal Findings

Participants performed aiming movements controlling a cursor on a computer screen. Visual feedback of direction of cursor motion was rotated 75° relative to the direction of hand motion. Participants had to adjust to this rotation in the presence and absence of an additional hand-movement target that explicitly depicted the input-output relations of the visuo-motor transformation. An extensive set of tests was employed in order to disentangle the contributions of different processes to visuo-motor adjustment. Results show that the augmented information failed to affect the age-related variations of explicit knowledge, adaptive shifts, and aftereffects in a substantial way, whereas it clearly affected initial direction errors during practice and proprioceptive realignment.

Conclusions

Contrary to expectations, older participants apparently made no use of the augmented information, whereas younger participants used the additional movement target to reduce initial direction errors early during practice. However, after a first block of trials errors increased, indicating a neglect of the augmented information, and only slowly declined thereafter. A hypothetical dual-task account of these findings is discussed. The use of the augmented information also led to a selective impairment of proprioceptive realignment in the younger group. The mere finding of proprioceptive realignment in adaptation to a visuo-motor rotation in a computer-controlled setup is noteworthy since visual and proprioceptive information pertain to different objects.     

More and more generalists: two decades of changes in the European avifauna

Biotic homogenization (BH) is a process whereby some species (losers) are systematically replaced by others (winners). While this process has been related to the effects of anthropogenic activities, whether and how BH is occurring across regions and the role of native species as a driver of BH has hardly been investigated. Here, we examine the trend in the community specialization index (CSI) for 234 native species of breeding birds at 10 111 sites in six European countries from 1990 to 2008. Unlike many BH studies, CSI uses abundance information to estimate the balance between generalist and specialist species in local assemblages. We show that bird communities are more and more composed of native generalist species across regions, revealing a strong, ongoing BH process. Our result suggests a rapid and non-random change in community composition at a continental scale is occurring, most likely driven by anthropogenic activities.