Brainport - Online Article

Introduction

In the modern phase of rapid engineering the things are moving towards the miniaturization and accuracy to achieve the human comfort and convenience. These all technologies has changed the way of living of human beings by providing them several biomedical and engineering devices which can give a whole new life to a disable person. Science and technology has moved leaps and bounds now and has provided solutions to human's inborn as well as accidental disabilities. This technical paper presentation depicts one such technology that is "THE BRAIN PORT" which uses electrotactile stimulation to help a visually impaired people to see things, a stroke patient to be in control of a vulnerable situation, a mentally disabled (Parkinson disease) patient to have control of its nerves. This technology also provides support to national army and air-force, a heaven to the professional gamers. All these things seem to be a 'miracle', but all these things are true. Let us explore it.

What is Brain Port

The patented Brain Port™ technology is based on the phenomenon of sensory substitution. For the vision application, visual information is perceived via the sense of touch on the human tongue.

Well, not exactly through her tongue, but the device in her mouth sent visual input through her tongue in much the same way that seeing individuals receive visual input through the eyes. In both cases, the initial sensory input mechanism -- the tongue or the eyes -- sends the visual data to the brain, where that data is processed and interpreted to form images. What we're talking about here is electrotactile stimulation for sensory augmentation or substitution, an area of study that involves using encoded electric current to represent sensory information -- information that a person cannot receive through the traditional channel -- and applying that current to the skin, which sends the information to the brain.

The multiple channels that carry sensory information to the brain, from the eyes, ears and skin, for instance, are set up in a similar manner to perform similar activities. All sensory information sent to the brain is carried by nerve fibers in the form of patterns of impulses, and the impulses end up in the different sensory centers of the brain for interpretation. To substitute one sensory input channel for another, you need to correctly encode the nerve signals for the sensory event and send them to the brain through the alternate channel. The brain appears to be flexible when it comes to interpreting sensory input. You can train it to read input from, say, the tactile channel, as visual or balance information, and to act on it accordingly. In JS On line's "Device may be new pathway to the brain,"

The modes of stimulation and its various forms

From the very beginning of the electro tactile stimulation this journey has travelled a lot and the various forms may be described as follows:

  • TVSS-Tactile Vision Substitution Systems.
  • Vibrotactile (FINGERTIPS).
  • Electro Tactile Stimulation for Tongue

Tactile vision substitution system

The TVSS may be characterized as a humanistic intelligence system. It represent a symbiosis between instrumentation-for example, an artificial sensor array (TV camera)-computational equipment, and the human user. Consistent with the terminology of this issue, this is made possible by "instrumental sensory plasticity," the capacity of the brain to reorganize when there is: (a) functional demand,(b) the sensor technology to fill that demand, and (c) the training and psychosocial factors that support the functional demand. To constitute such systems then, it is only necessary to present environmental information from an artificial sensor in a form of energy that can be mediated by the receptors at the human-machine interface, and for the brain, through a motor system (e.g., a head-mounted camera under the motor control of the neck muscles), to determine the origin of the information.

This can now be extended into other domains with modern technology and the availability of artificial sensory receptors, such as:

  1. A miniature TV camera for blind persons,
  2. A MEMS technology accellerometer for providing substitute vestibular information for persons with bilateral vestibular loss,
  3. Touch and shear-force sensors to provide information for spinal cord injured persons,
  4. Instrumented condom for replacing lost sex sensation, or
  5. A sensate robotic hand (Bach-y-Rita, 1999).

In first sensory substitution project, they developed tactile vision substitution Systems (TVSS) to deliver visual information to the brain via arrays of stimulators in contact with the skin of one of several parts of the body (abdomen, back thigh). Optical images picked up by a TV camera were transduced into a form of energy (vibratory or direct electrical stimulation) that could be mediated by the skin receptors. In these sensory substitute systems, the visual information reaches the perceptual levels for analysis and interpretation via somatosensory pathways and structures.

Vibrotactile

After sufficient training with the TVSS, our subjects reported experiencing the image in space, instead of on the skin (see, e.g., Figure 1). They learn to make perceptual judgments using visual means of analysis, such as perspective, parallax, looming and zooming, and depth judgments (Bach-y-Rita, Collins, Saunders, White, & Scadden, 1969; cf., Bach-y-Rita, 1972, 1989, 1995, 1996, 1999; Bach-y-Rita, Kaczmarek, & Meier, 1998; Bach-y-Rita, Kaczmarek, Tyler, & Garcia-Lara, 1998; Bach-y-Rita, Webster, Tompkins, & Crabb, 1987; Kaczmarek & Bach-y-Rita, 1995; White, Saunders, Scadden, Bach-y-Rita, & Collins, 1970). Although the TVSS systems have only had between 100 and 1032 point arrays, the low resolution has been sufficient to perform complex perception and "eye"-hand coordination tasks. These have included facial recognition, accurate judgment of speed and direction of a rolling ball with over 95% accuracy in batting a ball as it rolls over a table edge, and complex inspection-assembly tasks. The latter were performed on an electronics company assembly line with a 100 point vibrotactile array clipped to the work-bench against which the blind worker pressed the skin of his abdomen, and through which information from a TV camera (substituting for the ocular piece of a dissection microscope) was delivered to the human-machine interface (Bach-y-Rita, 1995, pp. 187-193).

Image1

Child reproducing perceived image of a teachers hand as displayed on a modified Optacon. The tactile image is picked up with one finger statically placed on the 6 × 24 vibrotactile array. LED monitor in foreground is visual representation of active pattern on the tactile display, which is obtained by the child's head-mounted camera.

Electrotactile Stimulation for Tongue

In the TVSS studies cited above, the stimulus arrays presented only black-white information, without gray scale. However, the tongue electrotactile system does present gray-scaled pattern information, and multimodal and multidimensional stimulation is possible. Simultaneously, we have also modeled the electrotactile stimulation parameter space to determine how we might elicit tactile "colors."

Aiello (1998a, 1998b) has identified six stimulus parameters: the current level, the pulse width, the interval between pulses, the number of pulses in a burst, the burst interval, and the frame rate. All six parameters in the waveforms can, in principle, be varied independently within certain ranges, and may elicit potentially distinct responses. For example, in a study of electrical stimulation of the skin of the abdomen, Aiello (1998a) suggested that the best way to encode intensity information independent of other percept qualities with a multidimensional stimulus waveform was through modulation of the energy delivered by the stimulus. In that case, the energy was varied in such a way that the displacement in the parameter space, corresponding to a given transition between energy levels, was minimal (gradient mode of stimulation). Although the gradient mode of stimulation requires a real-time fulfillment of mathematical constraints among all the parameters, its implementation could be included within a microelectronic package for signal treatment. The tongue interface overcomes many of these. The tongue is very sensitive and highly mobile. Since it is in the protected environment of the mouth, the sensory receptors are close to the surface. The presence of an electrolytic solution, saliva, assures good electrical contact. The results obtained with a small electrotactile array developed for a study of form perception with a finger tip demonstrated that perception with electrical stimulation of the tongue is somewhat better than with finger-tip electrotactile stimulation, and the tongue requires only about 3% of the voltage (5-15 V), and much less current (0.4-2.0 mA), than the finger-tip. The electronic system has been described elsewhere (Bach-y-Rita, Kaczmarek, Tyler, et al., 1998).

Electrotactile stimuli are delivered to the dorsum of the tongue via flexible electrode arrays (Figure 3) placed in the mouth, with connection to the stimulator apparatus (TDU) via a flat cable passing out of the mouth. The tongue electrode array and cable are made of a thin (100 μm) strip of polyester material (Mylar®) onto which a rectangular matrix of gold-plated copper circular electrodes has been deposited by a photolithographic process similar to that used to make printed circuit boards. The electrotactile stimulus consists of 40-μs pulses delivered sequentially to each of the active electrodes in the pattern. Bursts of three pulses each are delivered at a rate of 50 Hz with a 200 Hz pulse rate within a burst. This structure was shown previously to yield strong, comfortable electrotactile percepts (Kaczmarek et al., 1992). Positive pulses are used because they yield lower thresholds and a superior stimulus quality on the fingertips.

Image2

Close-up of 144-point (12 x 12) "virtual ground" electrotactile tongue display

Action potentials (AP's) thus recorded had amplitudes from 0.1 to 1.0 mV and a 5 : 1 signal-to-noise ratio (SNR).A circular electrode surrounding the recording site served as the ground reference. Following pre amplification and band pass filtering (200-10 000 Hz), a differential amplitude detector identified AP's, producing an output pulse whenever the recorded signal entered a predefined amplitude-time window. In the first experiment, electrotactile entrainment currents (iEN) were determined by adjusting the stimulation current from near zero to the minimal value resulting in one AP for each stimulation pulse. These currents exceeded the absolute thresholds (the currents causing occasional AP's) by approximately 5%. The entrainment current was determined twice for positive- and negative-polarity stimulation pulses of ten different widths: 20, 30, 40, 50, 70, 100, 150, 200, 300, and 500 _s, delivered at a rate of 10 pulses/s. The width sequence was reversed during the second run on each of the three fibers.

Image3

Relative timing between simultaneous mechanical and electrotactile stimulation. The top trace represents the sinusoidal, 30-Hz, 50-100-_m (0-P) mechanical displacement.

Brain Port Image Device

The Brain Port vision system consists of a postage stamp size tongue display, a control box and a video camera. Visual information is collected from a head mounted video camera and sent to the Brain Port control box. The control box translates the visual information into an electrical pattern for display on the tongue. With the current system, study participants have been able to recognize high contrast objects, their locations, movements, as well as aspects of perspective and depth. All participants involved in the study have enjoyed the training and were excited to perceive things that they had not been able to perceive without the Brain Port device.

For one thing, Brain Port uses the tongue instead of the fingertips, abdomen or back used by other systems. The tongue is more sensitive than other skin areas -- the nerve fibers are closer to the surface, there are more of them and there is no stratum corneum (an outer layer of dead skin cells) to act as an insulator. It requires less voltage to stimulate nerve fibers in the tongue -- 5 to 15 volts compared to 40 to 500 volts for areas like the fingertips or abdomen. Also, saliva contains electrolytes, free ions that act as electrical conductors, so it helps maintain the flow of current between the electrode and the skin tissue. And the area of the cerebral cortex that interprets touch data from the tongue is larger than the areas serving other body parts, so the tongue is a natural choice for conveying tactile-based data to the brain.

a simplified view of the BrainPort vision components prototype

To produce tactile vision, BrainPort uses a camera to capture visual data. The optical information -- light that would normally hit the retina -- that the camera picks up is in digital form, and it uses radio signals to send the ones and zeroes to the CPU for encoding. Each set of pixels in the camera's light sensor corresponds to an electrode in the array. The CPU runs a program that turns the camera's electrical information into a spatially encoded signal. The encoded signal represents differences in pixel data as differences in pulse characteristics such as frequency, amplitude and duration. Multidimensional image information takes the form of variances in pulse current or voltage, pulse duration, intervals between pulses and the number of pulses in a burst, among other parameters.

To produce tactile vision, BrainPort uses a camera to capture visual data. The optical information -- light that would normally hit the retina -- that the camera picks up is in digital form, and it uses radio signals to send the ones and zeroes to the CPU for encoding. Each set of pixels in the camera's light sensor corresponds to an electrode in the array. The CPU runs a program that turns the camera's electrical information into a spatially encoded signal. The encoded signal represents differences in pixel data as differences in pulse characteristics such as frequency, amplitude and duration. Multidimensional image information takes the form of variances in pulse current or voltage, pulse duration, intervals between pulses and the number of pulses in a burst, among other parameters.

Brain Port Balancing Device

Wicab is currently seeking FDA approval for a balance-correction BrainPort application. A person whose vestibular system, the overall balance mechanism that begins in the inner ears, is damaged has little or no sense of balance -- in severe cases, he may have to grip the wall to make it down a hallway, or be unable to walk at all. Some inner-ear disorders include bilateral vestibular disorders (BVD), acoustic neuroma and Meniere's disease, and the sense of balance can also be affected by common conditions like migraines and strokes. The BrainPort balance device can help people with balance problems to retrain their brains to interpret balance information coming from their tongue instead of their inner ear.

An accelerometer is a device that measures, among other things, tilt with respect to the pull of gravity. The accelerometer on the underside of the 10-by-10 electrode array transmits data about head position to the CPU through the communication circuitry. When the head tilts right, the CPU receives the "right" data and sends a signal telling the electrode array to provide current to the right side of the wearer's tongue. When the head tilts left, the device buzzes the left side of the tongue. When the head is level, BrainPort sends a pulse to the middle of the tongue. After multiple sessions with the device, the subject's brain starts to pick up on the signals as indicating head position -- balance information that normally comes from the inner ear -- instead of just tactile information.

a simplified view of the BrainPort balance components

BrainPort balance components simplified

Clinical trial with the balance device in 2005 with 28 subjects suffering from bilateral vestibular disorders (BVD). After training on BrainPort, all of the subjects regained their sense of balance for a period of time, sometimes up to six hours after each 20-minute BrainPort session. They could control their body movements and walk steadily in a variety of environments with a normal gait and with fine-motor control. They experienced muscle relaxation, emotional calm, improved vision and depth perception and normalized sleep patterns.

More current and potential Application

While the full spectrum of BrainPort applications has yet to realized, the device has the potential to lessen an array of sensory limitations and to alleviate the symptoms of a variety of disorders. Just a few of the current or foreseeable medical applications include:

  • Providing elements of sight for the visually impaired.
  • Providing sensory-motor training for stroke patients.
  • Providing tactile information for a part of the body with nerve damage.
  • Alleviating balance problems, posture-stability problems and muscle rigidity in people with balance disorders and Parkinson's disease.
  • Enhancing the integration and interpretation of sensory information in autistic people.

Beyond medical applications, there has been exploring potential military uses with a grant from the Defense Advanced Research Projects Agency (DARPA). The company is looking into underwater applications that could provide the Navy SEALs with navigation information and orientation signals in dark, murky water (this type of setup could ultimately find a major commercial market with recreational SCUBA divers). The BrainPort electrodes would receive input from a sonar device to provide not only directional cues but also a visual sense of obstacles and terrain. Military-navigation applications could extend to soldiers in the field when radio communication is dangerous or impossible or when their eyes, ears and hands are needed to manage other things -- things that might blow up. BrainPort may also provide expanded information for military pilots, such as a pulse on the tongue to indicate approaching aircraft or to indicate that they must take immediate action. With training, that pulse on their tongue could elicit a faster reaction time than a visual cue from a light on the dashboard, since the visual cue must be processed by the retina before it's forwarded to the brain for interpretation.

Other potential BrainPort applications include robotic surgery. The surgeon would wear electrotactile gloves to receive tactile input from robotic probes inside someone's chest cavity. In this way, the surgeon could feel what he's doing as he controls the robotic equipment. Race car drivers might use a version of BrainPort to train their brains for faster reaction times, and gamers might use electrotactile feedback gloves or controllers to feel what they're doing in a video game. A gaming BrainPort could also use a tactile-vision process to let gamers perceive additional information that isn't displayed on the screen.

BrainPort is currently conducting a second round of clinical trials as it works its way through the FDA approval process for the balance device. The company has made a commercial release of its product in late 2006, with a roughly estimated selling price of $10,000 per unit.

Already more streamlined than any previous setup using electrotactile stimulation for sensory substitution, BrainPort envisions itself even smaller and less obtrusive in the future. In the case of the balance device, all of the electronics in the handheld part of the system might fit into a discreet mouthpiece. A dental-retainer-like unit would house a battery, the electrode array and all of the microelectronics necessary for signal encoding and transmitting. In the case of the BrainPort vision device, the electronics might be completely embedded in a pair of glasses along with a tiny camera and radio transmitter, and the mouthpiece would house a radio receiver to receive encoded signals from the glasses. It's not exactly a system on a chip, but give it 20 years -- we might be seeing a camera the size of a grain of rice embedded in people's foreheads by then.

Conclusions

Technology is a boon in biomedical and can work for all the field like defence, sports, robotics, spy gadgets, and is able to change the life of physically and mentally impaired persons. In comparison to biology, human-machine interface technology is in its early infancy.

The brain is much more complex and efficient than any present or even foreseeable electronic device. Even the nervous systems of insects-which allow highly developed functions such as the ability to identify and localize potential mates at great distances in moths, and the pattern perception and homing and complex motor and social behavior of Monarch butterflies-defy simulation on the most advanced computers (Bach-y-Rita, 1995), and all of that is managed in a tiny speck of a "brain." This can only improve in the future, and thus technology will provide access to biological-like capabilities.

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