Development of Tactile Display Devices Using fMRI under High Magnetic Fields

Development of Tactile Display Devices Using fMRI under High Magnetic Fields

Masayuki Kitazawa (Department of Intelligent Mechanical Engineering, Wakayama National College of Technology, Japan)
DOI: 10.4018/978-1-60960-559-9.ch035
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Abstract

Recently, the physiological function of the human brain has become the subject of several investigations. Several methods have been developed to measure neural functioning. One such method is functional magnetic resonance imaging (fMRI). This approach is utilized under a high magnetic field with an average strength of 1.5T. As a result, special devices are needed to serve as stimuli for subjects in an fMRI study. In particular, devices for the investigation of tactile sense are rare. In this work, the authors report the development of novel tactile display devices. These devices can be used to stimulate the skin of the subject’s hand to produces both pressure and movement stimulation. The devices are manipulated with ultrasonic motors that do not have coils and are constructed with non-magnetic materials, such as stainless steel and acrylic acid resin. Therefore, these devices can be used without disturbing the high magnetic field. To quantify the influence of the devices to the magnetic field, signal to noise ratios (SNR) for images generated by MRI were measured. These experiments confirmed that the SNR was altered by 5% when the devices were present; however, this change is within the acceptable range for the quality of an MRI image. From this work, the authors conclude that the developed devices have sufficient performance under high magnetic field conditions.
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Tactile Display Devices

As mentioned above, two kinds of devices were developed. The first utilizes vertical movement and produces the tactile stimulus by moving the arm of the device up and down with a cam. The shape of the cam is designed to use the weight of the arm to generate a pressure sensation when the tip of the arm touches the surface of the skin. Figure 1a shows the pressure stimulation device, and Figure 1b shows the tip of the arm. The shape of the tip is hemispherical with a diameter of 10 mm. A diameter of less than 10 mm has the potential to generate not only a tactile sense but also a sense of pain. This device is designed to generate only a tactile stimulus.

Figure 1.

Tactile display device that generates pressure. (a) Body of the device. (b) Tactile portion of the device

The second device utilizes back and forth movements and is constructed with a turning block slider crank mechanism. A brush pen mounted on the slider moves horizontally along the skin to give a tactile stimulus. This device produces a transformation that generates a sense of movement. The speed of the pen movement is important. When the approach speed is fast, subjects are often uncomfortable, thus the speed of this device is set at 0.35 m/s from the reference. Figure 2a shows the movement stimulation device, and Figure 2b shows the brush pen.

Figure 2.

Tactile display device that generates movement. (a) Body of the device. (b) Tactile portion of the device

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