Jacopo Zenzeri

Istituto Italiano di Tecnologia | IIT · Department of Robotics, Brain and Cognitive Sciences

The contribution to balance of spinal and transcortical processes including the long-latency reflex is well known. The control of balance has been modelled previously as a continuous, state feedback controller representing, long-latency reflexes. However, the contribution of slower, variable delay processes has not been quantified. Compared with fi...

Afferent proprioceptive signals, responsible for body awareness, have a crucial role when planning and executing motor tasks. Increasing evidence suggests that proprioceptive sensory training may improve motor performance. Although this topic had been partially investigated, there was a lack of studies involving the wrist joint. Proprioception at t...

Objective The purpose of this study was to examine the effects of submaximal isometric neck muscle fatigue and manual therapy on wrist joint position sense (JPS) within healthy individuals and individuals with subclinical neck pain (SCNP). Methods Twelve healthy participants and 12 participants with SCNP were recruited. Each group completed 2 sess...

The purpose of this work was to investigate forearm muscle activity and wrist angular displacement during radial and ulnar wrist perturbations across various isometric hand grip demands. Surface electromyography (EMG) was recorded from eight muscles of the upper extremity. A robotic device delivered perturbations to the hand in the radial and ulnar...

Fatigue is a temporary condition that arises as a result of intense and/or prolonged use of muscles and can affect skilled human performance. Therefore, the quantitative analysis of these effects is a topic of crucial interest in both ergonomics and clinical settings. This study introduced a novel protocol, based on robotic techniques, to quantitat...

A positive aging requires placing human changes due to healthy or pathological senescence at the center of gerontechnology design. A set of key solutions for accomplishing this goal is offered by neurotechnologies. These systems can monitor and interpret data related to the central and peripheral nervous systems for understanding the individual con...

This paper describes the design and development of a new mechanical layout for the integration of additional sensors on robots that directly interact with humans. This specific work starts from the need to control human-robot interaction forces in order to ensure safety for users. The activity consisted on the conceptualization and design of a new...

In the last two decades, a growing interest has been focused on gait and balance robot-assisted rehabilitation in children with neurological disabilities. Robotic devices allow the implementation of intensive, task-specific training fostering functional recovery and neuroplasticity phenomena. However, limited attention has been paid to the protocol...

During the interaction with others, action, speech, and touches can communicate positive, neutral, or negative attitudes. Offering an apple can be gentle or rude, a caress can be kind or rushed. These subtle aspects of social communication have been named vitality forms by Daniel Stern. Although they characterize all human interactions, to date it...

In this study, we implemented a protocol for the robotic assessment of the effects of forearm muscle fatigue on wrist dynamics. The potential of robotic devices lies in the possibility to control and measure a wide variety of kinematic and physiological variables, both in repeated sessions over time and during real-time assessments. The implemented...

Robotics can be used to describe wrist kinematics and assess sensorimotor impairments, while the implementation of training algorithms can be aimed at improving neuromuscular control. The purpose of this study was to use a robotic device to develop an adaptive and individualized training program of the distal upper extremity for individuals with mu...

In this study, we designed a robot-based method to compute a mechanical impedance model that could extract the viscoelastic properties of the wrist joint. Thirteen subjects participated in the experiment, testing both dominant and nondominant hands. Specifically, the robotic device delivered position-controlled disturbances in the flexion-extension...

Background: In recent years, many studies focused on the use of robotic devices for both the assessment and the neuro-motor reeducation of upper limb in subjects after stroke, spinal cord injuries or affected by neurological disorders. Contrarily, it is still hard to find examples of robot-aided assessment and rehabilitation after traumatic injuri...

Introduction: The rapid development of electromechanical and robotic devices has profoundly influenced neurorehabilitation. Growth in the scientific and technological aspects thereof is crucial for increasing the number of newly developed devices, and clinicians have welcomed such growth with enthusiasm. Nevertheless, improving the standard for th...

During the interaction with others, action, speech, and touches can communicate positive, neutral, or negative attitudes. Offering an apple can be gentle or rude, a caress can be kind or rushed. These subtle aspects of social communication have been named vitality forms by Daniel Stern. Although they characterize all human interactions, to date it...

A deep investigation of proprioceptive processes is necessary to understand the relationship between sensory afferent inputs and motor outcomes. In this work, we investigate whether and how perception of wrist position is influenced by the direction along which the movement occurs. Most previous studies have tested Joint Position Sense (JPS) throug...

Position sense refers to an aspect of proprioception crucial for motor control and learning. The onset of neurological diseases can damage such sensory afference, with consequent motor disorders dramatically reducing the associated recovery process. In regular clinical practice, assessment of proprioceptive deficits is run by means of clinical scal...

Effective tutoring during motor learning requires to provide the appropriate physical assistance to the learners, but at the same time to assess and adapt to their state, to avoid frustration. With the aim of endowing robot tutors with these abilities, we designed an experiment in which participants had to acquire a new motor ability - balancing an...

We evaluated the effects of muscle fatigue on hand-tracking performance in young adults. Differences were quantified between wrist flexion and extension fatigability, and between males and females. Participants were evaluated on their ability to trace a pattern using a 3-degrees-of-freedom robotic manipulandum before (baseline) and after (0, 1, 2,...

Skilled motor behavior is critical in many human daily life activities and professions. The design of robots that can effectively teach motor skills is an important challenge in the robotics field. In particular, it is important to understand whether the involvement in the training of a robot exhibiting social behaviors impacts on the learning and...

Functioning as wrist stabilizers, the wrist extensor muscles exhibit higher levels of muscle activity than the flexors in most distal upper-limb tasks. However, this finding has been derived mostly from isometric or wrist flexion-extension protocols, with little consideration for wrist dynamics or radial-ulnar wrist deviations. The purpose of this...

Current research suggests that the wrist extensor muscles function as the primary stabilizers of the wrist-joint complex. However, most investigations have utilized isometric study designs, with little consideration for wrist dynamics or changes in posture. The purpose of the present study was to assess forearm muscle activity during the execution...

Balancing the body in upright standing and balancing a stick on the fingertip are two examples of unstable tasks that, in spite of strong motor and sensory differences, appear to share a similar motor control paradigm, namely a state-space intermittent feedback stabilization mechanism. In this study subjects were required to perform the two tasks s...

Due to their stabilizing role, the wrist extensor muscles demonstrate an earlier onset of performance fatigability and may impair movement accuracy more than the wrist flexors. However, minimal fatigue research has been conducted at the wrist. Thus, the purpose of this study was to examine how sustained isometric contractions of the wrist extensors...

Balance requires the centre of mass to be maintained within the base of support. This can be achieved by minimising position sway (stiffness control: SC) or minimising force error (force accuracy control: FAC). Minimising sway reduces exploration of system properties, whereas minimising force error maximizes accurate mapping of the force vs positio...

Sudden disturbances (perturbations) to the hand and wrist are commonplace in daily activities and workplaces when interacting with tools and the environment. It is important to understand how perturbations influence forearm musculature and task performance when identifying injury mechanisms. The purpose of this work was to evaluate changes in forea...

Objective: To determine whether different phenotypes of cervical dystonia (CD) express different types and levels of somatosensory impairment. Methods: We assessed somatosensory function in patients with CD with and without tremor (n = 12 each) and in healthy age-matched controls (n = 22) by measuring tactile temporal discrimination thresholds o...

Proprioception is a crucial sensory modality involved in the control and regulation of coordinated movements and in motor learning. However, the extent to which proprioceptive acuity is influenced by local muscle fatigue is obscured by methodological differences in proprioceptive and fatiguing protocols. In this study, we used high resolution kinem...

The development of robotic devices for rehabilitation is a fast-growing field. Nowadays, thanks to novel technologies that have improved robots’ capabilities and offered more cost-effective solutions, robotic devices are increasingly being employed during clinical practice, with the goal of boosting patients’ recovery. Robotic rehabilitation is als...

Neuromotor disorders negatively affect the sensorimotor system, limiting the ability to perform daily activities autonomously. Rehabilitation of upper limb impairments is therefore essential to improve independence and quality of life. In the last two decades, there has been a growing interest in robot-assisted rehabilitation as a beneficial way to...

Proprioceptive information allows humans to perform smooth coordinated movements by constantly updating one's mind with knowledge of the position of one's limbs in space. How this information is combined with other sensory modalities and centrally processed to form conscious perceptions of limb position remains relatively unknown. What has proven e...

Balancing a stick on the fingertip while standing upright is a dual balancing task that requires the integration of two independent control systems. This is a completely novel experimental paradigm for attempting to understand how the brain deals with equilibrium in a general way. Preliminary results are presented and interpreted in the framework o...

Many complex activities of daily living are characterized by instabilities. From a motor control point of view, there are two alternative stabilization mechanisms that require to integrate multi-joint coordination aspects: stiffness and positional stabilization strategies. The aim of this work is to understand how the central nervous system can swi...

Innovative research in the fields of prosthetic, neurorehabilitation, motor control and human physiology has been focusing on the study of proprioception, the sense through which we perceive the position and movement of our body, and great achievements have been obtained regarding its assessment and characterization. However, how proprioceptive sig...

This study utilized a 3-degree of freedom robotic device (Wristbot) to examine wrist proprioception and eye-hand coordination in a cross-sectional sample of sixty-three young adults (19-29 years), 20 older young adults (30-49), and 17 older adults (50 years and older). Results indicated differences in the emergence of age-related declines in sensor...

The aim of this work is to present a novel robot-based method to assess the sources of a lack of functionality in patients with recent traumatic wrist injuries. Post-traumatic patients experience limited range of motion as well as strength and proprioceptive deficits. These dysfunctions are related to different complications that usually follow the...

Stabilization of the CIP (Cart Inverted Pendulum) is an analogy to stick balancing on a finger and is an example of unstable tasks that humans face in everyday life. The difficulty of the task grows exponentially with the decrease of the length of the stick and a stick length of 32 cm is considered as a human limit even for well-trained subjects. M...

In the study of balance and postural control the (Single) Inverted Pendulum model (SIP) has been taken for a long time as an acceptable paradigm, with the implicit assumption that only ankle rotations are relevant for describing and explaining sway movements. However, more recent kinematic analysis of quiet standing revealed that hip motion cannot...

Data from the simulation of the DIP/VIP hybrid model. In the Table are presented the angles and angular accelerations of Ankle (q1) and Hip (q2.). (ZIP)

The assessment of muscle fatigue could provide crucial information to monitor the progression of a neuromuscular disease, as well as evidences about the efficacy of an eventual therapeutic approach. The aim of the present work is to test the feasibility of a novel method based on a robotic wrist device and sEMG, on neuromuscular pediatric subjects...

Quiet standing has been modeled many times as an unstable task of controlling an inverted pendulum in a gravity divergent force field. Multiple sensory systems and motor components of the nervous system are involved in postural balancing and the stabilization problem becomes even more complex in presence of perturbations. In the present work, we re...

Background Several neuromuscular disorders present muscle fatigue as a typical symptom. Therefore, a reliable method of fatigue assessment may be crucial for understanding how specific disease features evolve over time and for developing effective rehabilitation strategies. Unfortunately, despite its importance, a standardized, reliable and objecti...

Regarding our voluntary control of movement, if identification of joint position, that is independent of the starting condition, is stronger than kinaesthetic movement reproduction, that implies knowledge of the starting position and movement's length for accuracy, is still a matter of debate in motor control theories and neuroscience. In the prese...

Proprioceptive signals from cutaneous, joint, tendon and muscle receptors create the basis for bodily perception and are known to be essential for motor control. However, which are the mechanisms underlying the proprioceptive signals and which are the variables that affect them is still a matter of debate. In particular, what is worth to investigat...

In daily life it is necessary to learn skills that can be applied in different tasks and different contexts. Usually these skills are acquired by observation or by direct physical training with another expert person. The critical point is to know which is the best possible way to achieve this knowledge acquisition. In this work we have proposed a c...

In this work we propose a novel method based on sEMG signals, easy and fast to perform, administered with a robotic device to maximize repeatability and objectivity. Muscle fatigue, which is frequently experienced by healthy subjects, can be a highly debilitating symptom in case of neuromuscular disorders. Its assessment provides crucial informatio...

It is known that physical coupling between two subjects may be advantageous in joint tasks. However, little is known about how two people mutually exchange information to exploit the coupling. Therefore we adopted a reversed, novel perspective to the standard one that focuses on the ability of physically coupled subjects to adapt to cooperative con...

Multivariable intermittent control (MIC) combines stability with flexibility in the control of unstable systems. Using an underlying continuous-time optimal control design, MIC uses models of the physical system to generate multivariate open-loop control signals between samples of the observed state. Using accurate model values of physical system p...

In everyday life the brain must adapt to variable situations that may require a mixture of approaches including anticipatory synergy formation, through an internal body schema, and different control strategies. Unstable tasks are particularly challenging because deteriorate the predictive power of internal models and further enhance the instability...

Physical interaction between man and machines is increasing the interest of the research as well as the industrial community. It is known that physical coupling between active persons can be beneficial and increase the performance of the dyad compared to an individual. However, the factors that may result in performance benefits are still poorly un...

Previous works have shown that, when dealing with instabilities in a bimanual manipulation paradigm, humans modulate the stiffness of the arms according to feedforward or feedback mechanisms as a function of the dynamics of the task. The aim of this work is to complement these results getting insights on how the CNS controls the muscles to achieve...

In the context of unstable tasks, whenever the dynamics of the interaction are unknown, our ability to control an object depends on the predictability of the sensory feedback generated from the physical coupling at the interface with the object. In the case of physical human-human interaction, the haptic sensory feedback plays a primary role in the...

The body-schema concept is revisited in the context of embodied cognition, further developing the theory formulated by Marc Jeannerod that the motor system is part of a simulation network related to action, whose function is not only to shape the motor system for preparing an action (either overt or covert) but also to provide the self with informa...

The stabilization of the human standing posture was originally attributed to the stiffness of the ankle muscles but direct measurements of the ankle stiffness ruled out this hypothesis, leaving open the possibility for a feedback stabilization strategy driven by proprioceptive signals. This solution, however, could be implemented with two different...

Although proprioceptive impairment is likely to affect in a significant manner the capacity of stroke patients to recover functionality of upper limb, clinical assessment methods currently in use are rather crude, with a low level of reliability and a limited capacity to discriminate the relevant features of this severe deficit. In the present pape...

Since action and perception are tightly coupled and the dysfunction of one of the two channels necessary give rise to different degrees of impairment in the other, we believe that the recovery process would significantly benefit from training protocols able to evaluate and consistently recruit both motor aspects and proprioception concurrently. The...

Purpose – The working hypothesis, on which this paper is built, is that it is advantageous to look at protocols of robot rehabilitation in the general context of human-robot interaction in haptic dyads. The purpose of this paper is to propose a new method to detect and evaluate an index of active participation (AC index), underlying the performance...

Human-human physical interaction has proven to be advantageous especially in contexts with high coordination requirements. But under which conditions can haptic communication bring to performance benefits in a challenging cooperative environment? In this work we investigate which are the dynamics that intervene when two subjects are required to swi...

In order to understand mechanisms of strategy switching in the stabilization of unstable dynamics, this work investigates how human subjects learn to become skilled users of an underactuated bimanual tool in an unstable environment. The tool, which consists of a mass and two hand-held non-linear springs, is affected by a saddle-like force-field. Th...

The term Robotic Rehabilitation defines a class of machines employed for different scenarios, ranging from therapeutic and assistive applications to robots devoted to neuroscience, behavioral research, and cognitive aspects. The first use of such technology dates back to early 1990s, with a relatively long history and it remains linked to the idea...

Proprioception has a crucial role in promoting or hindering motor learning. In particular, an intact position sense strongly correlates with the chances of recovery after stroke. A great majority of neurological patients present both motor dysfunctions and impairments in kinesthesia, but traditional robot and virtual reality training techniques foc...

In this preliminary study we compare continuous with pulsed robot assistance in five chronic stroke survivors with a mild degree of spasticity, with the aim of promoting volitional effort and reducing assistance during a reaching task. The protocol consists of one familiarization session and a single training session during which a manipulandum pro...

The goal of this paper is to analyze the static stability of a computational architecture, based on the Passive Motion Paradigm, for coordinating the redundant degrees of freedom of a humanoid robot during whole-body reaching movements in bipedal standing. The analysis is based on a simulation study that implements the Functional Reach Test, origin...