RICERCA ITALIANA     

Research program

Computational and neural mechanisms of sensorimotor learning and control

University Co-ordinator

Politecnico di TORINO - ELETTRONICA - TORINO(TO)

Research Unit Leader

Marco KNAFLITZ

Description

The activities of this UR will cover 24 months. This UR is leader of WP5 and will contribute to the experimental parts of WP4, WP6, and WP8.
Specifically, this UR will carry out the following tasks:
a) design and development of a multichannel stimulator that will include a closed-loop control based on the on-line monitoring of physiological variables;
b) definition of new techniques for the closed–loop functional electrical stimulation (FES) to study motor learning and to be used for rehabilitation of upper-limb motor impaired subjects;
c) cooperation with other URs for the execution of sets of experiments and the analysis of the results.

WP5: FUNCTIONAL ELECTRICAL STIMULATION (FES)

The goal of this WP is the development of an innovative approach based on closed – loop FES for the rehabilitation of patients affected by upper – limb coordination problems or motor impairment and suitable to be used to study how the brain learns motor control.
When applying closed – loop FES, the stimulation parameters (stimulation frequency, amplitude and impulse duration) must be constantly adjusted on the basis of measurements carried out on the subject performing the exercise. We have analyzed the characteristics of the electrical stimulators available on the market at this time and we were not able to find a product suitable for our project. Because of this we plan to design and build a multichannel closed-loop controlled stimulator to be used to identify task- or performance-dependent functional stimulation techniques. These techniques will be applied to subject executing upper-limb reaching or tracking exercises. We plan to perform a new check of the stimulators available on the market before starting the development of the new one.
The specific tasks of this UR will be: a) the development of the multichannel stimulator with the corresponding control software, and b) the execution of a set of experiments with the VHE in cooperation with UR_UniGE1 aimed to identify the stimulation strategies that give better results.
The first step will be the design of the stimulator. An important requirement is the possibility of controlling the instruments by means of a pc or any other device that is able to produce the correct control signals. The number of stimulation channels will be defined taking into account data available in literature, the movements that are expected to be tested during the experiments, and the real possibility of selectively stimulating different muscle by means of surface electrodes. The final decision on the number of channels will be taken discussing with the other URs. The user will be able to control the stimulation frequency, and the duration and intensity of the stimulus; we will investigate the necessity and the possibility to control some of the stimulation parameters independently for each stimulation channel. The link between the stimulator and the external device will probably be by means of a USB connector.
The circuitry of both the stimulation channels and the interface to the external device is very complex and needs to be maintained as small as possible. The only way to obtain a reliable system is the use of multilayer printed circuits (from eight to ten layers) realized with a 100µm routes and 300-500µm vias. The complexity of the realization is the reason of the costs of the printed circuits.
This device should follow the European safety requirements for medical devices and should be electrically insulated from the piloting workstations that will generate the control signals and will measure biomechanical and physiological parameters.
Besides the hardware components we will start the realizations of the control interface that in this phase will be on a pc and the stimulator firmware.
The stimulation sequences to be used will be based on the analysis of the typical activation patterns of healthy subjects. The control signals will be obtained on the basis of "error" signals or physiological variables on-line measured on the subject (muscle activation, joint angles, velocity, acceleration signals, ...) As we will deal with movements obtained by means of the joint activation of different muscles the number of possible control variables will be elevated. To deal with this other complexity an algorithm for determining the minimum number of signals to be acquired is envisioned. The algorithm should take into account both the pathology of the patient, and the typology of exercise to be performed. During the last few years, this UR developed an algorithm to suggests the better choice of the muscles to be investigated during a session of gait analysis on the basis of an observational analysis of gait. This decision aiding system uses genetic algorithms with a fitness function in which the number of sensors is minimize while the informative capacity of the gait analysis results is maximized. This algorithm will be modified to make it suitable to the analysis of the movements of the upper – limb. By means of this procedure we aim at finding the minimum number of muscles required for an effective quantification of the sensorimotor performance, hence minimizing the complexity of the experiment and data acquisition, and limiting the patient discomfort.
Accelerometric, goniometric, and myoelectric signals will be acquired on the subject performing the motor tasks by means of sensors commercially available and/or previously designed and/or especially designed. Muscle activity will be identified by means of a activation intervals statistical detector previously developed in cooperation with UR_Roma3 (Bonato 1998) and the results obtained into WP4.
The fist experiments will be carried out in the VHE. The goal of this pilot set of experiments, which will be carried on normal subjects, will be the identification of preliminary stimulation methodologies, meaning the control strategies to be used in case of simple movements.

Percentual resource allocation: 50%
Deliverables:
D5.1: Release of the first version of the multichannel stimulator (month 9; UR_Polito)
D5.2: Report on experiments with the VHE (month 15; UR_Polito, UR_UniGE1)

WP4: ELECTRICAL MUSCLE ACTIVITY (EMG)

This UR will contribute to the executions of the experiments planned for this WP for the parts including electrical functional stimulation. The specific goal will be to better understand how the use of electrical stimulation could contribute to increase the knowledge on motor learning and on motor control.

Allocazione percentuale di riserse: 10%
Deliverables:
D4.2: Report on experiments on the construction of muscle synergies in the VHE (month 15; UR_UniRoma3, UR_Polito,UR_UniGE1)
D4.3: Report on experiments on the construction of muscle synergies in the VVE (month 12; UR_UniRoma3, UR_Polito,UR_UniBO)
D4.4: Report on experiments on muscle fatigue in the VHE (month 14; UR_UniRoma3, UR_Polito,UR_UniGE1)

WP6: INTEGRATION OF THE TWO VIRTUAL PLATFORMS

The activities of this WP will be carried out in cooperation with the others URs to effectively integrate the developed functional stimulation techniques with the VHE e VVE.
The literature on this topic is quite limited and so it is difficult to envision a precise scenario. In general the goal is to gain some understanding on how visuomotor learning and force field adaptation can facilitate each other or enter in conflict.
Given the complexity of the experimental setup and the limited time span of the project only a preliminary pilot study will be carried out but we think that its novelty could open the door to an important new road in the study of motor learning.
The activities in this WP will be split into two steps, an implementation step and an experimental step that includes several pilot experiments. The contribution of this UR will focus on the aspects related to functional electrical stimulation and in particularly it will contribute to pilot study 4: evaluation of some neural correlates of the combined haptic, visual adaptation; this activity will focus on the most promising experimental protocol (determined in the two previous activities) and the most promising procedures of estimation of neural correlates evaluated in WP3 or WP4.

Allocazione percentuale di riserse: 15%
Deliverables:
D6.4: Report on the estimation of some neural correlates during the combined adaptation experiments (month 24; all URs )

WP8: NEUROREHABILITATION

This UR will participate to the pilot study no 3. If the experiments performed in WP5 will give positive results we shall carryout a pilot study in which the innovative approach based on closed - loop FES for facilitating the process of motor learning is applied to patients affected by upper – limb incoordination or paralysis.

Allocazione percentuale di riserse: 25%
Deliverables:
D8.3: Report on rehabilitation experiments focused on closed-loop FES (month 24; UR_Polito, UR_UniGE1)