Neuroprosthetics Lab
Neuroprosthetics Lab
Experiment HN-8: Human To Human Interface Introduction to Neuroprosthetics and Human-to-Human Muscle Control Take control…of your partner that is! An exciting, new technological development has to deal with the science and research into neuroprosthetics. A neuroprosthetic is a device that replaces the function of a damaged body part and interfaces with the nervous system – think of the body suit that Iron Man wears and the new prosthetic devices that are being 3-D printed for use for kids with malformed limbs. These devices can be controlled by the person using them just by thinking about what they want to do, like writing or holding onto something. These devices are controlled in such a way so there is an interface with the nervous system to make the prosthetic work. There are many reasons why this research is so exciting. One has to do with how to help people with spinal cord injuries. Currently, if someone damages their spinal cord above a certain point, they are confined to a wheelchair and could be on supportive mechanisms to help them breathe; this is what happened to Christopher Reeves after his accident from falling off a horse. The interesting thing is that even though the spinal cord is damaged, the muscles in the person’s limbs are still “alive” and can function, but they need to receive information from somewhere to be able to move. With a damaged spinal cord, the information being sent from the brain does not reach the limbs. This is where neuroprosthetics comes into play. Imagine if you could send a signal from the brain directly to a prosthesis, and have it work!! There is currently research out there where this is actually happening. Another method of controlling artificial limbs is by using the electrical activity generated by pectoral or quadriceps muscles to control the sensors and motors right in the robotic arm or leg. | Request a Quote Would you like to speak to an iWorx representative? Give us a call at 603-742-2492 or we’ll call you. Just email your name, telephone number and a convenient time to call. |
So, where does this Human-to-human interface come in? In lab, since we do not have the capability to get Iron Man’s suit or 3-D print a prosthetic, we can use one person as the “brain” and one person as the “prosthesis”. This means that one person will have the ability to actually control the movements of the other!This will be done by using the stimulator on the IX-TA unit and having Person A (the “controller”) squeeze a ball that will in turn signal the interface (the IX-TA) to fire a signal off to Person B. Person B’s hand will be holding the hand dynamometer and when “A” squeezes the ball…Person B will squeeze the hand dynamometer…totally without their own control. The stimulator works like a TENS unit (Transcutaneous Electrical Nerve Stimulation) that is used by physical therapists for interrupting nerve and muscle spasms to promote healing. When Person A squeezes the ball, it will signal the stimulator to send a current to Person B, when that current is received by the muscles in the hand, the hand will twitch.This lab opens up many opportunities for hypothesis testing. Can you hold a pencil, balance a ball, or make a Lego car move?Set-up Equipment Required PC or Mac Computer IX-TA Setup 1. Place the IX-TA on the bench, close to the computer. Start the Software 1. Click on the LabScribe shortcut on the computer’s desktop to open the program. If a shortcut is not available, click on the Windows Start menu, move the cursor to All Programs and then to the listing for iWorx. Select LabScribe from the iWorx submenu. The LabScribe Main window will appear as the program is opens. The Equipment Setup Note – Connect the iWire-B3G cable to the IX-TA prior to turning it on. 1. Attach the connector on the end of the iWire-B3G cable to the iWire 1 input of the front of the IX-TA (HN-8-S1). Figure HN-8-S1: IX-TA with the FT-220, iWire-B3G and stimulator lead wires for performing the Human to Human Interface lab. Person A 1. The subject should remove all jewelry from his/her right arm. Figure HN-8-S2: Electrode and lead placement for Person A, who will be generating the signal to be carried to Person B through the stimulator. 3. Obtain three disposable electrodes.
5. Person A should also hold a tennis ball or other squeezable object. Person B 1. Obtain two disposable electrodes.
4. Have Person B lightly cup the FT-220 hand dynamometer in the palm of their hand, trying not to hold on to it too tightly. It should be just resting in their grip. Figure HN-8-S3: Placement of the stimulating electrodes for Person B. IX-TA Isolated Stimulator The IX-TA has a high voltage stimulus isolator designed to deliver constant current to the nerve or muscle being studied. In situations where the resistance (R) along the path of the current increases, the voltage (V) increases to maintain the current (I in V = IR, Ohm’s Law). The ability of the IX-TA to adjust the voltage to deliver the required current is known as voltage compliance. The upper limit of this compliance by the IX-TA is set at 100 Volts. Constant current devices differ from constant voltage devices when presented with an increase in resistance, like the dehydration of the conductive gel under the electrodes. As pointed out earlier, a constant current stimulator is voltage compliant. In constant voltage stimulators, the current delivered to the tissue decreases as the resistance increases because the power supply of the constant voltage device is not designed to deliver additional current. Although the IX-TA can generate up to 100 Volts, the current delivered by the unit is limited to a maximum of 20 milliamperes, for a maximum duration of 10 milliseconds per pulse, and a maximum frequency of 50 pulses per second (Hz). At these levels, the maximum amount of power delivered by the IX-TA will not cause injury or tissue damage. The current is selected using the Stimulator Control Panel. The HV Stimulator can deliver a maximum output of twenty milliamperes. The duration, frequency, and number of stimulus pulses generated by the stimulator are also controlled by making changes to the values in the Stimulator Control Panel. The initial values of the pulses generated by the IX-TA are programmed by the same settings file that configured the recording software. For example, if a pulse from the IX-TA is programmed for a duration of 1 millisecond and a frequency of 1 Hz, the stimulator will generate a stimulus pulse with the same duration and frequency. IX-TA Stimulator Setup 1. Place the IX-TA (Figure HN-8-S1) on the bench near the subject. Warning: Before connecting the IX-TA stimulating electrodes to the subject, check the Stimulator Control Panel to make sure the amplitude value is set to zero (0). Note: Disconnect the subject from the IX-TA prior to powering off the device 2. Instruct the subject to remove all jewelry before beginning the experiment. Figure HN-8-S4: The IX-TA stimulating electrodes. 3. For any of the HVS labs, the stimulator preferences panel will initially come up showing S1, even if S1 is off – use the menu to select the HVS settings. 4. Connect the color-coded stimulator lead wires to the High Voltage Current Stimulator. Make sure you push the safety connector of each lead wire into the appropriate socket as far as possible (Figure HN-8-S4). 5. Connect the 2 stimulating electrodes as stated above. 6. Start with the stimulator programmed in this manner (Table HN-8-S1):
Table HN-8-S1: Settings on the Stimulator Window Used to Configure the Stimulator of the IX-TA for Experiment HN-8. Experiment HN-8: Human to Human Interface WARNING – The Stimulator should only be used for the method of application for which it is intended as shown in the directions below. Note: Disconnect the subject from the IX-TA prior to powering off the device. NOTE: Any changes in amplitude are entered directly into the Stimulator Control Panel. Click “APPLY” to make the change. Exercise 1: Human to Human Muscle Control Aim: To determine the effect of a “squeeze” by Person A on Person B’s response. Procedure 1. Ask Person A to hold a tennis ball, or other squeezable object, in his or her hand. Lay the hand on the bench with the palm up. Make sure Person A is not squeezing the ball and to relax.
Note: Person A should make sure to relax his/her forearm and hand completely. Any tensing of the muscles will interfere with the recording and could elicit an unexpected response from Person B. 2. Ask Person B to sit quietly, with their hand lightly cradling the hand dynamometer. Little to no pressure from the fingers should be holding the sensor. 3. Click Record button on the LabScribe Main window. 4. Instruct Person A to squeeze the ball or curl his or her hand towards the wrist. It should be a quick, firm reaction. 5. Click the AutoScale All button on the toolbar to improve the display of the stimulus and the muscle’s response (Figure HN-8-L1). 6. Have Person A squeeze the ball or flex the hand five (5) times. Note: Person B should have a response each time Person A flexes or squeezes. 7. Select Save As in the File menu, type a name for the file. Choose a destination onthe computer in which to save the file (e.g. the iWorx or class folder). Click the Save button to save the file (as an *.iwxdata file). Figure HN-8-L1: A recording showing Person A squeezing or flexing and the subsequent response from Person B. The red vertical cursors are in position to measure the time from the peak of the Integral to the response from Person B. Data Analysis 1. Use the display time icons to double the display time to get the entire data set on screen (Figure HN-8-L2). Figure HN-8-L2: The LabScribe toolbar. 2. Click the Analysis icon in the LabScribe toolbar ( Figure HN- 8 -L 3) to view the recorded responses. 3. Note that T2-T1 is shown in the bar across the tops of all the channels. Measure T2-T1 by placing the two red vertical cursors on the peak of the Integral from Person A and the subsequent response from Person B. Data analysis can also be performed on the main window. Figure HN-8-L3: T2-T1 for the time between the stimulus from Person A to the response from Person B. In this example the time is 0.110 seconds between stimulation and response. 4. The functions in the channel pull-down menus of the Analysis window can also be used to enter the names and values of the parameters from the recording to the Journal. To use these functions:
Question 1. Is the time of response from Person B the same for each stimulus by Person A? If not, what could be the reason? | |