An f-MRI Study of an Adaptable EMG Prosthetic Hand with Biofeedback

An f-MRI Study of an Adaptable EMG Prosthetic Hand with Biofeedback

Alejandro Hernandez Arieta (The University of Tokyo, Japan), Ryu Kato (The University of Tokyo, Japan), Hiroshi Yokoi (The University of Tokyo, Japan), Tamio Arai (The University of Tokyo, Japan), Wenwei Yu (University of Chiba, Japan) and Rolf Pfeifer (University of Zurich, Switzerland)
Copyright: © 2008 |Pages: 9
DOI: 10.4018/978-1-59904-889-5.ch075
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Abstract

The mutual adaptation between man-machine opens new possibilities in the development of better userfriendly interfaces that not only adapt to the user’s characteristics, but also permits the adaptation of the user to the machine. There are several examples of the use of feedback to improve the man-machine interface. One example is the use of sound to acquire cues in the interaction with the machine (Rauterberg, 1999). These studies show the improvement in the interaction when we increase the number of communication channels between the man and the machine. The problem with sound cues is that need the conscious effort to be recognized. Hunter, Katz, and Davis (2003) show another example of the importance of increasing the communication channels in the interaction between man and machine. In this study, they show how the multiple sensory stimuli contribute to the conscious awareness of the body, and how it can be used to change the abnormal body awareness that occurs after limb amputation. This effect is also known as cortical reorganization, where the brain after losing the stimuli from the amputated limb, due to the cross-modality, received input signals from the adjacent neurons, resulting in what is called “phantom limb.”

Key Terms in this Chapter

Proprioception: From latin proprius, meaning “one’s own” and perception) is the sense of the relative position of neighboring parts of the body. Proprioception is an interception sense that provides feedback solely on the status of the body internally.

Transcutaneous Electrical Nerve Stimulation: More commonly referred as TENS unit and pronounced tens, is an electronic device that produces electrical signals used to stimulate nerves through unbroken skin. The name was coined by Dr. Charles Burton. The unit s usually connected to the skin using two or more electrodes.

f-MRI: Functional MRI (fMRI) measures signal changes in the brain that are due to changing neural activity, by a mechanism referred to as BOLD (blood-oxygen-level dependent) effect. Increased neural activity causes an increased demand for oxygen, and the vascular system actually overcompensates for this, increasing the amount of oxygenated hemoglobin (haemoglobin) relative to deoxygenated hemoglobin. Because deoxygenated hemoglobin attenuates the MR signal, the vascular response leads to a signal increase that is related to the neural activity.

Myoelectric: Also called a motor action potential, is an electrical impulse that produces contraction of muscle fibers in the body. The term is most often used in reference to skeletal muscles that control voluntary movements. Myolectric signals have frequencies ranging from a few Hertz too about 300Hz, and voltages ranging from approximately 10 microvolts to 1 milivolt.

Primary Somatosensory Area (S1): Brodmann areas 3,1 and 2 comprise the primary somatosensory cortex of the human brain. This area of cortex, as shown by Wilder Oenfield and others, has the pattern of a homunculus. That is, the legs and trunk fold over the midline; the arms and hands are along the middle of the areas shown here; and the face is near the bottom of the figure.

Hemodynamic: Literally “blood dynamics,” or hemorheology, is the study if the properties and flow of blood. The study of hemodynamics with regard to neural function (the hemodynamic response) is the basis for functional magnetic resonance imaging.

Primary Motor Cortex (M1): Works in association with pre-motor areas to plan an execute movements. M1 contains large neurons known as Betz cells which send long axons down the spinal cord to synapse onto alpha motor neurons which connect to the muscles. Pre-motor areas are involved in planning actions (in concert with the basal ganglia) and refining movements based upon sensory input (this requires the cerebellum).

Sensory Substitution: Is the principle to transform characteristics of one sensor modality into stimuli of another sensory modality. It is hoped that systems that base on sensory substitution can help handicapped people restore the ability to perceive certain sensory modality.

Cortical Reorganization: Process believed to occur after a limb amputation due to the lack of stimuli from usual channels. Cause of phantom limbs and phantom pain.

Frontal Lobe: Located at the front of each cerebral hemisphere, frontal lobes are positioned in front of the parietal lobes.

Duty Rate: In electronics is the percentage of time where an square signal presents “On” state.

Echo-Planar Imaging(EPI): MRI Protocol developed by Peter Mansfield to increase the collection speed for T2* weighted images.

Electromyography (EMG): A medical technique for evaluating and recording properties of muscles at rest and while contracting. EMG is performed using an instrument called electromyograph, to produce a record called electromyogram. An electromyography detects the electrical potential generated by muscle cells when these cells contract, and also when the cell are at rest.

Epoch: A reference date. An instant of origin chosen as the date from which time is measured in a computer system.

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