Grip Type Research Articles

Functional evaluation of early tendon transfer for thumb opposition in median nerve palsy

BackgroundThere is paucity of literature on early tendon transfer in surgical rehabilitation of hands with median nerve injuries. Since the single most important functional deficit in median nerve palsy is the loss of thumb opposition, we evaluated the results of early tendon transfer in restoration of thumb opposition. MethodsThis prospective study involved 10 cases of isolated median nerve paralysis (axonotmesis or neurotmesis) that underwent early tendon transfer for restoration of thumb opposition. A pre- and post-operative evaluation in terms of power and precision grip strength and range of opposition of thumb was done. Median nerve exploration was performed in 4 cases and was supplemented by a tendon transfer for thumb opposition. The extensor indicis proprius (EIP) opponensplasty was performed in nine out of ten cases. In one case where the patient had scarring over the EIP tendon, palmaris longus (PL) opponensplasty was performed. ResultsThe median age at injury was 29 years (range; 8 years–57 years). Minimum period of follow-up was 6 months. Six patients who underwent EIP transfer had excellent opposition while 3 had good opposition. The patient, in whom PL opponensplasty was done, had an excellent opposition. The median time for return to work was 2.75 months.There was significant improvement in the power grip and all three types of precision grip at 6 months follow-up. The percentage deficit in the affected hand compared to the normal hand was significantly reduced. There was no case of tendon pull out in our study, nor did any of our patients have an extensor lag following EIP transfer. ConclusionEarly tendon transfer has a unique role in the management of median nerve palsy hand and we suggest this procedure should be considered in both high and low lesions.

Analysis of Different Hand and Finger Grip Patterns using Surface Electromyography and Hand Dynamometry

Recording an Electromyogram (EMG) signal is essential for diagnostic procedures like muscle health assessment and motor neurons control. The EMG signals have been used as a source of control for powered prosthetics to support people to accomplish their activities of daily living (ADLs). This work deals with studying different types of hand grips and finding their relationship with EMG activity. Five subjects carried out four functional movements (fine pinch, tripod grip and grip with the middle and thumb finger, as well as the power grip). Hand dynamometer has been used to record the EMG activity from three muscles namely; Flexor Carpi Radialis (FCR), Flexor Digitorum Superficialis (FDS), and Abductor Pollicis Brevis (ABP) with different levels of Maximum Voluntary Contraction (MVC) (10-100%). In order to analyze the collected EMG and force data, the mean absolute value of each trial is calculated followed by a calculation of the average of the 3 trials for each grip for each subject across the different MVC levels utilized in the study. Then, the mean and the standard deviation (SD) across all participants (3 males and 2 females) are calculated for FCR, FDS and APB muscles with multiple % MVC, i.e 10, 30, 50, 70 % MVC for each gesture. The results showed that APB muscle has the highest mean EMG activity across all grips, followed by FCR muscle. Furthermore, the grip with the thumb and middle fingers is the grip with the highest EMG activity for 10-70% MVC than the power grip. As for the 100% MVC, thumb and middle fingers grip achieved the highest EMG activity for APB muscle, while the power grip has the highest EMG activity for both FCR and FDS muscles.

Forearm electromyographic activity during the deadlift exercise is affected by grip type and sex

Muscle activation, peak velocity (PV) and perceived technical difficulty while using three grip variations and three loads during a deadlift exercise (DL) were examined. Twenty-nine resistance-trained athletes (15 males, age: 22.2 ± 2.7 years; 14 females, age: 24.8 ± 7.0 years) performed the DL with 50%, 70% and 90% of their one repetition maximum (1RM) using hook grip (HG), mixed grip (MG) and double overhand (DOH) grip. Surface electromyography (EMG) of the brachialis (BS), brachioradialis (BR) and flexor carpi ulnaris (FCU) was recorded. PV and perceived technical difficulty of each grip were also measured. Regardless of load and grip, females exhibited greater BS activation compared to males (p < 0.05; ES = 0.69) while males displayed greater BR activation, significant at 90% load (p < 0.01; ES = 1.01). MG elicited the least BR and FCU activation regardless of load and sex (p < 0.01; ES = 0.64–0.68) and was consistently ranked as the easiest grip for any load. Males achieved significantly greater PV than females at 50% and 70% (p < 0.01; ES = 1.72–1.92). Hand orientation did not significantly impact PV. A MG may be beneficial in reducing the overall perceived technical difficulty when performing a maximal DL. Athletes aiming to maximise muscle activation and potentially develop their grip strength should utilise a DOH grip or HG.

Smash the dichotomy of Skeuomorphism and flat design: Designing an affordable interface to correspond with the human perceptuomotor process

Abstract Skeuomorphism and flat design, which are the most prevalent design styles, have both striven for supremacy in interface design. A consensus has not been reached due to inconsistent findings in academia and groundless arguments on the internet. In this article, we aim to explore perceptuomotor differences between these two design styles via object-based correspondence effects. Experiments with object-based correspondence effects allow the affordance to be measured quantitatively, comparing both perceptual and operational aspects of each design style. In Experiment 1, the two design styles are compared in terms of the correspondence effect between handle-orientation (left/right) and a user's responding hand (right hand/left hand). In Experiment 2, the two design styles are compared in terms of the correspondence effect between object size (big/small) and grip type (power grip/precision grip). The results in both experiments indicate that the two design styles are not different at the perceptuomotor level. This demonstrates that an affordance is similarly evoked in digital objects designed with either skeuomorphism or flat design. Further, we discuss the reason for the inconsistent findings in previous research, concluding that results have been influenced by unfamiliar forms and inappropriate real-world metaphors. Based on the conclusions, we suggest three design principles that designers can use to avoid confusion related to the design styles. In our discussion, we determine that the design styles are muddled with dimensionality and metaphor, which increases the inconsistent research findings in the literature. Finally, we suggest that the dichotomy between skeuomorphism and flat design is discarded.

3D Printing: The Effect of Adapted Mallets on the Participation of Children with Severe and Multiple Disabilities

The purpose of this study was to determine the changes in two measures of participation for a small sample of children with severe and multiple disabilities when using adapted mallets for instruments. The two measures of participation were: decibel level (dB) and frequency of sound produced. Three children between the ages of 5 and 11 years old participated in a single music therapy session testing four different popular adapted mallets, and a control mallet. A 3D-printed mallet grip was among the adapted mallets and was customized to the individual’s hand contour. The sessions tested all five mallets in random order on the each of the three children. Although no noticeable pattern of preference was found for any type of mallet grip, the data indicated that across all the subjects, they produced the lowest dB level and the least frequency of sounds on the control mallet. The results show that there are different preferences for each individual child based on the material and design, not just the hand contour. There are several implications for future research on customizing the 3D-printed adaptive grips to not only their hand contour but the material and design preferences of each child to further increase their participation in music making.

Grip Force Measurement as a Complement to High-Resolution Ultrasound in the Diagnosis and Follow-Up of A2 and A4 Finger Pulley Injuries.

The ability of finger flexors to generate force has been studied in relation to climbing performance. However, not much attention has been paid to the decrease in finger grip force in relation to annular pulley injuries. The purpose of the present study was to determine if an injured annular pulley implies a finger flexor force decrease, as well as its relation to clinical and sonographic changes. We performed an observational study in 39 rock climbers with A2 or A4 pulley injuries to the 3rd or 4th fingers. The variables considered were pain upon palpation, ultrasound tendon–bone distance, and finger grip strength decrease. Three rock climbing grip types were considered: the one finger crimp, open crimp, and close crimp. Injured rock climbers presented a decrease in finger grip strength compared to non-injured controls when performing a one finger crimp (p < 0.001). There exists a significant correlation between a tendon–bone distance at the level of the injured pulley and a decreased finger grip strength measured by performing a one finger crimp (p = 0.006). A decrease in finger grip strength could be considered in the diagnostic and follow-up process of A2 and A4 pulley injuries to the 3rd and 4th fingers.

Manual dexterity of mice during food-handling involves the thumb and a set of fast basic movements.

The small first digit (D1) of the mouse's hand resembles a volar pad, but its thumb-like anatomy suggests ethological importance for manipulating small objects. To explore this possibility, we recorded high-speed close-up video of mice eating seeds and other food items. Analyses of ethograms and automated tracking with DeepLabCut revealed multiple distinct microstructural features of food-handling. First, we found that mice indeed made extensive use of D1 for dexterous manipulations. In particular, mice used D1 to hold food with either of two grip types: a pincer-type grasp, or a "thumb-hold" grip, pressing with D1 from the side. Thumb-holding was preferentially used for handling smaller items, with the smallest items held between the two D1s alone. Second, we observed that mice cycled rapidly between two postural modes while feeding, with the hands positioned either at the mouth (oromanual phase) or resting below (holding phase). Third, we identified two highly stereotyped D1-related movements during feeding, including an extraordinarily fast (~20 ms) "regrip" maneuver, and a fast (~100 ms) "sniff" maneuver. Lastly, in addition to these characteristic simpler movements and postures, we also observed highly complex movements, including rapid D1-assisted rotations of food items and dexterous simultaneous double-gripping of two food fragments. Manipulation behaviors were generally conserved for different food types, and for head-fixed mice. Wild squirrels displayed a similar repertoire of D1-related movements. Our results define, for the mouse, a set of kinematic building-blocks of manual dexterity, and reveal an outsized role for D1 in these actions.

Head forward flexion, lateral bending and viewing distance in smartphone users: A comparison between sitting and standing postures

Smartphones (SPs) are widely used by people of all age groups and genders. Users spend many hours per day on the SPs for different purposes, which imposes significant stress on their musculoskeletal system. This study explored head forward flexion, lateral bending angle, and viewing distance while working with a SP in sitting/standing postures and one-handed/two-handed grips. The users' performance as well as pain development were also investigated. Participants answered a questionnaire on pain experience before and after SP usage. Neck kinematics of 20 SP users were monitored by a motion analysis system while doing three tasks (typing, video watching, and reading) in sitting and standing postures. Performance was evaluated by number of typed words, amount of errors in typing, and total read words. The results indicated a significant increase in pain complaints in neck and upper limbs after test completion. Working with SPs in sitting and standing postures were, respectively, associated with greater head forward flexion for watching and viewing distance for two-handed typing tasks. Higher left lateral bending values were measured for one-handed watching and reading tasks in standing posture. The performance measures were superior for two-handed grips in all conditions. Overall, using SPs in sitting posture creates greater head forward flexion and lower lateral bending angles in all tasks and grip types. The findings of this study can be used to provide recommendations for SP users.

Tactile Signatures and Hand Motion Intent Recognition for Wearable Assistive Devices.

Within the field of robotics and autonomous systems where there is a human in the loop, intent recognition plays an important role. This is especially true for wearable assistive devices used for rehabilitation, particularly post-stroke recovery. This paper reports results on the use of tactile patterns to detect weak muscle contractions in the forearm while at the same time associating these patterns with the muscle synergies during different grips. To investigate this concept, a series of experiments with healthy participants were carried out using a tactile arm brace (TAB) on the forearm while performing four different types of grip. The expected force patterns were established by analysing the muscle synergies of the four grip types and the forearm physiology. The results showed that the tactile signatures of the forearm recorded on the TAB align with the anticipated force patterns. Furthermore, a linear separability of the data across all four grip types was identified. Using the TAB data, machine learning algorithms achieved a 99% classification accuracy. The TAB results were highly comparable to a similar commercial intent recognition system based on a surface electromyography (sEMG) sensing.

Improving bimanual interaction with a prosthesis using semi-autonomous control

BackgroundThe loss of a hand is a traumatic experience that substantially compromises an individual’s capability to interact with his environment. The myoelectric prostheses are state-of-the-art (SoA) functional replacements for the lost limbs. Their overall mechanical design and dexterity have improved over the last few decades, but the users have not been able to fully exploit these advances because of the lack of effective and intuitive control. Bimanual tasks are particularly challenging for an amputee since prosthesis control needs to be coordinated with the movement of the sound limb. So far, the bimanual activities have been often neglected by the prosthetic research community.MethodsWe present a novel method to prosthesis control, which uses a semi-autonomous approach in order to simplify bimanual interactions. The approach supplements the commercial SoA two-channel myoelectric control with two additional sensors. Two inertial measurement units were attached to the prosthesis and the sound hand to detect the movement of both limbs. Once a bimanual interaction is detected, the system mimics the coordination strategies of able-bodied subjects to automatically adjust the prosthesis wrist rotation (pronation, supination) and grip type (lateral, palmar) to assist the sound hand during a bimanual task. The system has been evaluated in eight able-bodied subjects performing functional uni- and bi-manual tasks using the novel method and SoA two-channel myocontrol. The outcome measures were time to accomplish the task, semi-autonomous system misclassification rate, subjective rating of intuitiveness, and perceived workload (NASA TLX).ResultsThe results demonstrated that the novel control interface substantially outperformed the SoA myoelectric control. While using the semi-autonomous control the time to accomplish the task and the perceived workload decreased for 25 and 27%, respectively, while the subjects rated the system as more intuitive then SoA myocontrol.ConclusionsThe novel system uses minimal additional hardware (two inertial sensors) and simple processing and it is therefore convenient for practical implementation. By using the proposed control scheme, the prosthesis assists the user’s sound hand in performing bimanual interactions while decreasing cognitive burden.

Social Motor Priming: when offline interference facilitates motor execution.

Many daily activities involve synchronizing with other people’s actions. Previous literature has revealed that a slowdown of performance occurs whenever the action to be carried out is different to the one observed (i.e., visuomotor interference). However, action execution can be facilitated by observing a different action if it calls for an interactive gesture (i.e., social motor priming). The aim of this study is to investigate the costs and benefits of spontaneously processing a social response and then executing the same or a different action. Participants performed two different types of grips, which could be either congruent or not with the socially appropriate response and with the observed action. In particular, participants performed a precision grip (PG; thumb-index fingers opposition) or a whole-hand grasp (WHG; fingers-palm opposition) after observing videos showing an actor performing a PG and addressing them (interactive condition) or not (non-interactive condition). Crucially, in the interactive condition, the most appropriate response was a WHG, but in 50 percent of trials participants were asked to perform a PG. This procedure allowed us to measure both the facilitator effect of performing an action appropriate to the social context (WHG)—but different with respect to the observed one (PG)—and the cost of inhibiting it. These effects were measured by means of 3-D kinematical analysis of movement. Results show that, in terms of reaction time and movement time, the interactive request facilitated (i.e., speeded) the socially appropriate action (WHG), whereas interfered with (i.e., delayed) a different action (PG), although observed actions were always PGs. This interference also manifested with an increase of maximum grip aperture, which seemingly reflects the concurrent representation of the socially appropriate response. Overall, these findings extend previous research by revealing that physically incongruent action representations can be integrated into a single action plan even during an offline task and without any training.

Evaluation of Load Distributions and Contact Areas in 4 Common Grip Types Used in Daily Living Activities

Grip analysis systems, with sensors quantifying load distributions and contact areas applied by the hand while grasping objects, are useful for collecting and recording instant data; these systems are popular in hand assessment. The purpose of this study was to determine the load distribution (LD) and contact area (CA) size of the palmar surface of the hand during 4 common grip types used in activities of daily living (standard, lateral, pinch, and tripod grips). A convenience sample of 80 right-handed subjects were enrolled in this study. Participants wore special gloves equipped with sensors and grasped a variety of objects. Contact area size and LD were determined for the 4 grip types. The CA and the LD were different for each grip. For standard grip, although the largest CA occurred at the metacarpophalangeal joint level, the largest LD was over the middle finger pulp. For standard grip, index, middle, and ring fingers appear to be loaded with almost the same frequency as the thumb. Although CA on the thumb was maximum in the pinch, lateral and tripod grip types, the LD on the thumb was not. This study shows that the LD and CA patterns differ widely among standard, pinch, lateral, and tripod grips. The percentage of CA occurring on the thumb was maximum in all grip types. This information is important to optimize the design of artificial manipulators or assistive devices and to optimize the hand rehabilitation process. In addition, results of the study can be used to guide the design of prostheses and biomedical implants better.

Looking beyond proportional control: The relevance of mode switching in learning to operate multi-articulating myoelectric upper-limb prostheses

ObjectiveOperating a multi-articulating myoelectric prosthetic hand requires both proportional control of surface electromyography (sEMG) signals and accurately producing triggers to switch between grip types. Proportional control, used for hand opening/closing, has been studied extensively but the grip-switching control far less so. Can switching be trained and if so, how early on can improvement be seen? And is the ability to produce precise switches related to proficiency in proportional control? We examined individual learning differences, monitored improvements in switching control, and assessed whether skilful proportional control predicts proficient switching. MethodsTwenty-three unimpaired participants fitted with sEMG electrodes on the wrist flexors/extensors performed two 10-minute tasks: an adaptive virtual catching task (proportional control) and an sEMG- feedback-based switching task, with multiple performance measures being recorded and compared. ResultsMost outcome measures revealed large individual differences, with 47–87% of the participants showing improvement in switching and 14% deteriorating. As hypothesized, no correlations were found between mode-switching and proportional-control skills. ConclusionLearning to generate accurate grip-switching control proved difficult and might not be feasible for all individuals with upper-limb amputations. Unaffected participants showing proficient proportional control were not automatically good at producing well-tuned mode switches. SignificanceIn rehabilitation, clients with good proportional control are often offered a multi-articulating hand prosthesis. Since we found no clear associations between the proficiency in proportional movements and mode switches, this rationale may warrant reconsideration. Rather, when selecting the most optimal prosthesis, an individual’s skills in both control types should be examined separately.

Dual polarized antennas with reduced user effects for LTE-U MIMO mobile terminals

A concept of using dual-polarized, three dimensional antenna elements with minimized current distribution on ground plane to reduce the effects of user’s hand on a mobile terminal operating in LTE-U 5G band is proposed. This method which also minimizes mutual coupling (MC) is studied using a structure consisting of two non-identical antenna elements based on folded monopole topology, fed using distinct feeding mechanisms and consequently resulting in dual-polarization. For validation, the performance of this proposed MIMO antenna (MA1) is compared with a pair of dual-polarized conventional PIFA (MA2) placed orthogonally on an identical mobile terminal chassis. Both structures are assessed in terms of radiation efficiency (ƞrad), envelop correlation coefficient (ECC) and multiplexing efficiency (ME). Moreover, due to large radiation coverage, a multitude of hand phantoms and types of grips are used in simulations and experimental evaluations to validate users’ effect. Despite the presence of human hand in various modes and grips, the proposed antenna indicated decreased ƞrad and ME of about 27% and 25%, respectively. This is due to the near negligible difference in current distributions on ground plane. In comparison, conventional PIFA which exhibited ƞrad and ME decrease of up to 71% and 70%, respectively.

Design and Use of an Apparatus for Presenting Graspable Objects in 3D Workspace.

Reaching and grasping are highly-coupled movements, and their underlying neural dynamics have been widely studied in the last decade. To distinguish reaching and grasping encodings, it is essential to present different object identities independent of their positions. Presented here is the design of an automatic apparatus that is assembled with a turning table and three-dimensional (3D) translational device to achieve this goal. The turning table switches different objects corresponding to different grip types while the 3D translational device transports the turning table in 3D space. Both are driven independently by motors so that the target position and object are combined arbitrarily. Meanwhile, wrist trajectory and grip types are recorded via the motion capture system and touch sensors, respectively. Furthermore, representative results that demonstrate successfully trained monkey using this system are described. It is expected that this apparatus will facilitate researchers to study kinematics, neural principles, and brain-machine interfaces related to upper limb function.

OCCUPATIONAL EXPOSURE TO LOCALIZED VIBRATIONS USING PORTABLE MECHANICAL BRUSH CUTTER IN COFFEE CROP

The use of portable brush cutter may expose workers to localized vibrations, from the transfer of mechanical vibration of the tool to the operator’s hands and arms. With this in mind, the objective in this study was to quantify the levels of occupational vibration transmitted to the hands and arms of the portable brush cutter operators under routine working conditions in the coffee crop. The vibration levels transmitted to the operator’s hands were measured during activity with portable brush cutters. The experimental design was completely randomized (CRD) in a factorial scheme (2 x 2) combined with two types of grip (Circular cable (CC) and double grip handle (DGH) with two types of tip cutting blades (2TB and 3TB). The data acquisition occurred from the use of the vibration meter SV 103, SVANTEK with triaxial accelerometer, installed on each of the worker’s hand at the contact point with the tool. The results demonstrated that the 2.5 ms-2 action level determined by NR 09 and NHO 10 was exceeded under all conditions of the present study. The highest accelerations were quantified in the operation of the brush cutter equipment with CC, reaching the daily exposure limit of 5 ms-2 allowed for an 8-hour of working day. The resulting acceleration of the DGH equipment was on average 37.45% lower than the operation with the CC equipment. The results bring indicatives of occupational advantages in the selection of these types of accessories for brush cutters, in order to mitigate the effects of exposure to HAV in extended use situations

The Multiple Representations of Complex Digit Movements in Primary Motor Cortex Form the Building Blocks for Complex Grip Types in Capuchin Monkeys.

In the present study, we investigated motor cortex (M1) and a small portion of premotor and parietal cortex using intracortical microstimulation in anesthetized capuchin monkeys. Capuchins are the only New World monkeys that have evolved an opposable thumb and use tools in the wild. Like most Old World monkeys and humans, capuchin monkeys have highly dexterous hands. We surveyed a large extent of M1 and found that ~22% of all evoked movements in M1 involved the digits, and the majority of these consisted of finger flexions and extensions. Different subtypes of movements could be identified, including opposable movements of digits 1 and 2 (D1 and D2). Interestingly, the pattern of such movements varied between animals. In one case, movements involved the adduction of the medial surface of D1 toward the lateral surface of D2, whereas in the other case, the tips of D1 and D2 came in contact. Unlike other primates examined, we also found extensive representations of the prehensile foot and tail. We propose that the manual behavioral repertoire of capuchin monkeys, which includes the use of tools in the wild, is well represented within the motor cortex in the form of muscle synergies between different body parts that compose these larger, complex behaviors.SIGNIFICANCE STATEMENT The ability to use tools is a milestone in human evolution. Capuchin monkeys are one of the few non-human primates that use tools in the wild. The present study is the first detailed exploration of the motor cortex of these primates using long-train intracortical microstimulation. Within primary motor cortex, we evoked finger movements involving flexions and extensions of multiple digits, or of the first and second digits alone. Interestingly, flexion of tail and toes could also be evoked. Together, these results suggest that the functional organization of the motor cortex represents not just muscles of the body, but muscle synergies that form the building blocks of the complex behavioral repertoire of these animals.

Reciprocal cortical activation patterns during incisal and molar biting correlated with bite force levels: an fMRI study

In humans, the incisors and molars have distinct functions during mastication, analogous to the two main types of handgrip, the precision and power grips. In the present study, we investigated cortical activation and masticatory muscle activity during incisal and molar biting via simultaneous functional magnetic resonance imaging and electromyogram (EMG) recordings. We conducted recordings in 15 healthy adult participants while they performed incisal and molar biting tasks at three step-wise force levels using two custom-made splints. Regarding the results of the ROI analysis, we found a significantly stronger positive linear correlation between the blood oxygenation level dependent signal and EMG activity during molar biting than incisal biting, which was particularly prominent in the primary sensorimotor cortex and the cerebellum. We also found a significantly stronger negative linear correlation during incisal biting than molar biting, which was particularly prominent in the rostral cingulate motor area, superior frontal gyrus, and caudate nucleus. These findings indicate that molar biting enables powerful chewing: brain activity in several brain areas related to motor function was increased with increasing bite force levels, while incisal biting enables fine motor control: brain activity in several brain areas related to motor control was increased with reduced bite force levels.

Neurons Modulated by Action Execution and Observation in the Macaque Medial Parietal Cortex

The observation of an action evokes discharges in a rich network of cortical areas [1-14]. In the present study, we have evaluated the effect of grasp execution and of the observation of others' grasping on the activity of neurons in the medial parietal area V6A, an area of the reach-to-grasp network never explored to date in this regard. Although V6A neurons are typically active during one's own grasping execution but not while one observes another's grasping, a minority of neurons showed mirror properties, active both when monkeys performed the taskand when they observed it being performed by the experimenter. Recent studies have shown that the discharge of mirror neurons may vary from congruent to noncongruent [7, 10, 15-17], but most mirror neurons show a clear relation between the visual action they respond to and the motor response they code [10], thus matching the sensory description of an observed action with its corresponding internal motor representation. In all V6A putative mirrorneurons, instead, neural representations during execution and observation were highly dissimilar, discounting the possibility that V6A specifically encodes the grip type performed by another agent. Notably, we have found that in these neurons, the neural representation of an object changed according to whether grasping was allowed or performed and whether the object was the target of another agent's grasping. In other words, rather than code another agent's observed action, V6A neurons appear to primarily encode the relevance, in the grasping context, of the target object.

Anterior Intraparietal Area: A Hub in the Observed Manipulative Action Network.

Current knowledge regarding the processing of observed manipulative actions (OMAs) (e.g., grasping, dragging, or dropping) is limited to grasping and underlying neural circuitry remains controversial. Here, we addressed these issues by combining chronic neuronal recordings along the anteroposterior extent of monkeys’ anterior intraparietal (AIP) area with tracer injections into the recorded sites. We found robust neural selectivity for 7 distinct OMAs, particularly in the posterior part of AIP (pAIP), where it was associated with motor coding of grip type and own-hand visual feedback. This cluster of functional properties appears to be specifically grounded in stronger direct connections of pAIP with the temporal regions of the ventral visual stream and the prefrontal cortex, as connections with skeletomotor related areas and regions of the dorsal visual stream exhibited opposite or no rostrocaudal gradients. Temporal and prefrontal areas may provide visual and contextual information relevant for manipulative action processing. These results revise existing models of the action observation network, suggesting that pAIP constitutes a parietal hub for routing information about OMA identity to the other nodes of the network.