Over 59,000 people all over the world have cochlear implants (NIDCD 2006). The cochlea is a rigid, coiled tube that is divided mechanically into two along its length by the basilar membrane. It is an organ in the ear that aids in hearing by transforming a mechanical vibration (input) into action potentials in the fibers of the auditory nerve (Fearn et al. 1999). When people have severe auditory damage that cannot be relieved by hearing aids, they turn to cochlear implants.

Pitch and its Purpose

Pitch is the ear’s response to frequency and is involved in recognition of melody and tone. Without pitch, one would be able to understand the words being spoken to them, but wouldn’t know if they were being asked a question or told a statement (Anon 2005). Pitch is the fundamental frequency, which is the lowest resonant frequency of a vibrating object. All frequencies higher than this are harmonics (multiples) of the fundamental frequency. For example, the third harmonic is the three times larger than the fundamental frequency, while the fourth harmonic is four times larger than the fundamental frequency. The normal frequency range of the human ear is 20-20,000 Hz, this range is often referred to as “hi-fi” (Anon 2005a). Fine structure is a gradually varying envelope, decomposed from the original signal, which modulates an extraordinarily high frequency carrier. It contains more acoustic cue for pitch recognition than a temporal envelope, therefore it is believed that modifying a cochlear implant processor with fine structure may improve pitch perception of the patient (Chen et al. 2006).

In the normal auditory system, after a sound is captured by the outer ear, the three small bones of the middle ear (incus, malleus, and stapes) and the ear drum input a displacement signal into the window of the cochlea. This signal causes a transverse wave to travel down the basilar membrane, which then encodes pitch tonotopically. This means that higher frequencies cause maximum vibrations at the window end and lower frequencies cause maximum vibrations at the apex of the cochlea (place cue). Additionally, the phase locking of the nervous discharge to the pure-tone affects the pitch (timing cue). Then, hair cells on the basilar membrane bend back and forth according to the amount of vibration produced and release an electrochemical substance. This substance causes neurons to fire and action potentials travel down fibers of the auditory nerve. Once the auditory nerve receives these electrical signals, it will send this information about the acoustic signal to the brain to be interpreted (Fearn 1999, O’Reilly 2006, and Loizou 1998).

Cochlear Implants

A cochlear implant, also known as a bionic ear, is a surgically-implanted electronic device that partially restores hearing of deaf people by electric stimulation of the auditory nerve (Fearn 1999). It is different from a hearing aid that simply amplifies sounds that may be detected by damaged ears because a cochlear implant avoids damaged portions of the ear and directly excites the auditory nerve. Cochlear implants carry out the function of the cochlea by using a very specific system. They use an external microphone that attains sound from the environment and delivers it to a speech processor. The speech processor then separates different frequencies by using band-pass filters and sound intensity; it takes this electrical signal down a wire to the transmitter. The transmitter uses electromagnetic induction to transport the processed electric sound to the internal parts of the implant. The receiver and stimulator convert signals into appropriate electrical impulses and send them down internal cables to electrodes. A group of electrodes, called an electrode array, collects the processed and converted signals and sends them to the appropriate parts of the auditory nerve. This electrode array receives an assigned frequency range from about 100 Hz to 8000 Hz (NIDCD 2006a). Due to the electrode array not being able to be inserted entirely into the apex of the cochlea, frequency information cannot be stored in a cochlear implant. This is because there is a mismatch between the assigned speech frequency and the position of the electrodes.

Restoring Pitch

Current cochlear implant devices are poor in pitch perception because they don’t extract and encode spectral or temporal cues appropriately. They have been manufactured to deliver up to 22 frequency channels, however patients haven’t been able to utilize more than eight of those channels (Chen et al. 2006). Many ideas have been introduced to restore pitch in a cochlear implant. Among these ideas are transplantation of the implant, increasing the radius of the electric field of electrodes, bilateral implants, stem cell regeneration of the cochlea, and many more (Smale 2006). This paper will focus mainly on spectral channel enhancements, temporal fine structure, and deep insertion electrode array.

A big way that frequency information can be reintroduced to a cochlear implant is by spectral channel enhancements. Imagine a spectrum of sound that contains many peaks and valleys, depending on the nature of the sound. Patients with damaged hearing have poor auditory filters that allow little decibel difference between these peaks and valleys, causing their perception of speech to be deprived. Spectral channel enhancement increases the difference in decibel level between peaks and valleys that are next to each other. This is done by inhibiting the valleys and enhancing the peaks in the sound spectrum. After spectral channel enhancement, the decibel difference between the peaks and valleys will be more discrete and the patient will be able to distinguish speech in an environment with background noise (Yang et al. 2006). Spectral valleys are reduced by lateral inhibition, which is the suppression of some neurons in order to increase stimulation of other neurons. Lateral inhibition can sharpen average rate profiles by enhancing its output from spatially steep input regions or suppressing its output from spatially smooth input regions (Shamma 1985). Spectral peaks are enhanced by tow-tone suppression, which is reduction in response to one tone due to the presence of another tone. The brain uses tow-tone suppression in audition, as well as vision, to extract vital cues in a noisy environment (Zeng et al. 2005).

Temporal fine structure cueing is also a way to reintroduce frequency information to a cochlear implant. Temporal fine structure constructs a carrier signal for each frequency band after band-pass filtration of the speech signal into multiple frequency bands. This process is carried out by using high-rate sinusoidal pulses from the peak positions of the fine structure. Then, the signal is amplitude modulated by the temporal envelope in the band to create a decomposed band-specific output signal. This improvement for cochlear implants is beneficial when the patient’s temporal envelope contains between four and 16 frequency bands, like when communicating in tonal languages or listening to music (Chen et al. 2006). This method also allows for the same modulation to be applied to all channels, however it is better if channels are stimulated at the same time rather than alone then alone (Green et al. 2005).

A widely proposed method to reintroduce pitch into cochlear implants is to insert the electrode array deeper into the cochlea. This method is currently being tested at the University of Michigan with ribbon film technology. The idea is to use thin film electrode sites that will directly stimulate the auditory nerve. The reason that this model will be able to be inserted more deeply into the cochlea than current models is that it is smaller and more flexible than the traditional model. Additionally, insertion of the device minimizes damage to healthy tissue in the cochlea. An advantage of this device is improved pitch perception by adding more electrodes along the length of it. While traditional devices contain about 20 stimulating sites, this model has 128 stimulating sites to increase tonal range and improve frequency perception (Bailey 2006).

Alongside the previous ideas curtail many other ideas everyday to improve cochlear implants. Many models are in line to be available on the market, while some ideas are still years away. Nevertheless, cochlear implants are under improvement for the thousands of patients all around the world that are counting on them.

-Amy Shah

Every year, 25,000 people in the United States have entire arm amputations and 61,000 people have partial hand amputations (Kulley 2003). These unfortunate victims must approach all daily activities differently for the rest of their lives. What can we do to help them? Metal prosthetics were used during the Renaissance Period and the rubber hand was invented in response to Civil War victims (Kulley 2003). Over time, these inventions have evolved into amazing tools for victims all around the world. There are many ways for patients to control their upper extremity prostheses available on the market, as well as experiments being tested off the market. In which of these experiments does the future of control for upper extremity prostheses lie?

Current Techniques for Controlling Upper Extremity Prostheses

There are several different types of upper extremity prosthetics from the Boston Arm to the Utah Arm to arms made of memory alloy to plastic arms. Many are available on the market and proven effective as prosthetic devices. However, what are the patient’s options for controlling their new limbs?

Myoelectric signal processing is currently the most widely-used mode of control for prosthetics. Myoelectric prosthetic devices take the muscles’ electrical signals and apply them to multifunctional prosthetics to provide patient control. The myoelectric method has been proven to be quite reliable in multiple cases and is often considered the best form of prosthetic control. However, this mode of control is often preferred by below elbow amputees only because myoelectric processing is limited to controlling only one joint at a time, thus having limited degrees of freedom (Parker 2006).

Neuroelectric signal processing is another mode of control that overcomes the myoelectric method’s shortcomings. Neuroelectric prosthetic devices take nerve-signal patterns and match them with motions commonly performed by the limb, the prosthetic is then programmed to generate a desired response. The neuroelectric method has the advantage of controlling multiple degrees of freedom, however it is more expensive than myoelectric signal processing (Sorensen 2005).

Targeted Reinnervation

Targeted reinnervation is a largely improved version of myoelectric control that produces more signals to control the prosthetic. It involves the invasive denervation of the amputated muscle and the anastomosis of those peripheral nerve endings to parts of muscles that are functionless in the body. This is an incredibly constructive procedure that employs functionless muscle areas to amplify nerve signals so that the patient can control their external prosthesis (Kuiken 2006).

This procedure, unlike myoelectric control, allows the patient to have multiple degrees of freedom. Targeted reinnervation doesn’t harm other muscles in the body and no function is lost because it only involves non-functional muscles. The biggest advantage of targeted reinnervation is that it may give real sensory feedback to the patient. A prosthetic arm that uses targeted reinnervation is already on the market and provides users with 20 degrees of freedom, it’s light and compact, and contains shape memory alloy (Kulley 2003).

Although targeted reinnervation has many positive aspects, it carries some disadvantages as well. It is an invasive procedure that involves a long, detailed surgical procedure. All the nerves must be consistently reinnervated over each surface area of the muscle because too little nerves per unit area of the muscle will not cause sufficient stimulation. It is also difficult to get separate signals from each muscle area, therefore the signals are hard to interpret and there is too much noise for the prosthetic to interpret the signal (Kuiken 2006).

Brain-Computer Interfaces

Brain-computer interfaces (BCIs) are a largely improved type of neuroelectric control and are a way for the brain to communicate directly with computers. BCIs use electrodes (sensors) to detect and analyze neural signals from the brain and convert them into electronic impulses that computers can understand (Cichocki 2003). There are three main types of BCIs that all have the same function and use the same basic methods.

Invasive BCIs have an electrode that’s smaller than a contact lens implanted directly on the brain’s grey matter, usually on the primary motor cortex. The electrode picks up extremely clear signals since it reads neuron firing directly from the brain. This can be disadvantageous as well because increasing amounts of scar tissue develop on the surface of the brain and the signal that the BCI receives gets weaker over time (Reinberg 2006). Additionally, this electrode must be surgically implanted into the patient’s head, which brings about all the complications of brain surgery such as hemorrhaging, weakness, brain damage, infection, and in rare cases even death (Medline Plus 2005).

Partially invasive BCIs use the same electrode as invasive BCIs, but it is not implanted directly on the brain even though it lies inside the skull. The electrode picks up neural firing from the surface of the brain (Fitzpatrick 2006). Partially invasive BCIs also have the problem of scar tissue build-up, but less builds up since the electrode is not in direct contact with the brain (Tresco 2006). They also have all the same complications of brain surgery as invasive BCIs do.

Non-invasive BCIs have electrodes carefully placed on a cap that the patient wears on their head. The electrodes pick up sensorimotor rhythms recorded from the scalp (McFarland 2004). This method has no complications of brain surgery and does not involve any direct contact with the brain, just the scalp. Because these BCIs are not picking up neuron firing directly from the brain, they often don’t pick up clear signals. Since there are always multiple neurons firing simultaneously in the brain, the signals that non-invasive BCIs pick up from the scalp are very noisy and are often misunderstood or not understood at all by the computer. Additionally, the cap cannot be worn for long periods of time due to electrode and skin problems with long recording times and the fact that when the patient gets sweaty, signals cannot be properly attained by the cap (Birbaumer 2006).

Limb Regeneration

Limb regeneration is the restoration of a lost or damaged limb via tissue repair. Many lower species have the ability to regenerate their limbs and these species have been studied in great depth to figure out why humans don’t have the same ability. Humans have the ability to regenerate epithelial tissue, but only in single cell layers like mucosa and epidermis. An exception to this is the phenomenon of children being able to regenerate their distal fingertips with no medical intervention (Gurtner 2006).

This is possible because the body reactivates developmental pathways by which the original tissue was created. The original tissue gets recreated by stem cells that have the potency to differentiate into various tissues in our bodies. Embryonic stem cells have the most potential because they have not fully differentiated, therefore researchers can manipulate them to develop into whatever tissue desired. This theory has been proven in vitro with embryonic stem cells, however the role of stem cells in the adult body is still ambiguous. It has been proposed that one somatic cell has enough genetic information to create an entire organism all on its own; hence reprogramming this somatic cell to differentiate into a desired product is possible. The idea of using retroviruses through gene therapy has been introduced to reprogram the DNA of a somatic cell, unfortunately this is a very controversial issue that the body’s immune system may even reject (Gurtner 2006).

Another possibility of limb regeneration lies in tissue engineering, which is the biological development of replacements and restorations for damaged tissues (Gurtner 2006). Tissue engineering of artificial skin has already been proven successful for thousands of burn victims across the country (MacFarlane 1997). Any artificial tissue or organ can be manufactured through tissue engineering, the trick is to make it compatible with the adult human body.

When scientists combine these two amazing discoveries of stem cells and tissue engineering, regenerative limbs may be created. A bioengineered scaffold can be created via tissue engineering to stick to and blend in with the area of the body in which the limb will be regenerated onto. This scaffold will be made of nature and artificial substances as well as growth factors that stimulate the proliferation of cells. If stem cells are incorporated into this scaffold, they will be able to proliferate and blend in to the wound as the scaffold degrades. With the aid of the proper growth factors and constant regulation, the stem cells can then potentially grow an entire limb! Disadvantages to this theory include, but are not limited to immune rejection of the limb, a vascular system going through the limb, regeneration in response to wounds, and the limb’s response to the environment (Gurtner 2006).

Business Analysis of this Technology

From a business perspective, this is an undying field. In the United States, about 10,000 upper limb prosthetics are sold per year, doctors and patients alike will always be looking for a better way to control their new prosthetic body parts (Kulley 2003). An entire prosthetic arm costs the patient $10,000-$15,000 on average, but can potentially cost up to $35,000. The average insurance company covers up to $1,500 a year for prosthetics and the patient pays for the remainder. It will only cost approximately $1000 to manufacture a prosthetic limb (Freeman 1998). Targeted reinnervation surgery costs over $2000 per patient (Kuiken 2006a) and a noninvasive BCI currently costs patients about $5000 per unit (Anon 2006).

Recommendation About Which Path to Follow for New Products

I believe that this company should invest their time and money into BCIs rather than targeted muscle reinnervation. The strategy of myoelectric control has been underway for many years and now it’s time for neuroelectric control to take over this industry. Neuroelectric control is in fact the more advanced way of monitoring impulses between the motor system and the brain and can ensure multiple degree of freedom movement (Kulley 2003). If we support this technique, it will open up many doors for our company to make new prosthetic devices that will collaborate with it. Think of the possibilities of a person that can’t even use the restroom on their own being able to work online independently. This is a revolutionary possibility that will change the lives of thousands of people and our company should definitely be a part of it.

-Amy Shah

Just imagine not being able to feel any physical pain. The good part is, of course, that you can’t feel any pain. The bad part is that you can bleed to death and probably wouldn’t even think of going to a hospital.

Voltage-gated sodium channels are essential in pain perception. A gene called SCN9A is responsible for creating these channels so that when something painful strikes the skin, these voltage-gated sodium channels can open up and stimulate sensory neurons to send a pain signal to the brain.

No Pain!

A six-year-old Pakistani boy is a street performer who can stick knives in his body day in and day out and still be perfectly fine without fainting. He posses a rare genetic mutation that leaves gene SCN9A functionless, which in turn leaves him incapable of feeling any pain. He has no other defects or abnormalities; everything else in his body is perfectly fine. This turned on a light bulb in Dr. Geoffrey Woods’ head. He had been studying this SCN9A gene at the University of Cambridge for quite a while now and was linking this idea to the morphine receptor we possess in our bodies. The gears in Dr. Woods’ brain were grinding until he came up with a wonderful idea. Just as this SCN9A gene is blocked in the Pakistani street performer, he could temporarily block it in patients during surgery and other procedures. Dr. Woods studied this boy and six of his young relatives, who also had the mutation in their bodies. This would be better than using Morphine, which can cause addiction and drowsiness, or Celebrex, which can cause heart damage. Many researchers continue on this idea to try to find a healthy and effective way of temporarily blocking the SCN9A gene. This discovery will lead to a very helpful pain killer in medical settings in the recent future.

-Amy Shah

What does the brain have to do with autism? The neurodevelopmental disorder (autism) has something to do with the brain, but scientists didn’t know the exact connection until now. The amygdala is a deep part of the brain associated with the perception of fear. It has been found that men with severe autism have smaller amygdalas than healthy men. Autistic men are fearful in social situations, this hyperactivates their amygdala and leads to toxic adaptation that kills amygdala cells. As more cells die over the years, the amygdala becomes smaller and the person’s ability to perceive dangerous situations decreases. Several studies have been conducted at the University of Wisconsin and the study group members with a small amygdala had trouble discerning fearful, happy and sad facial expressions. On average, they took 40% longer to recognize emotional facial expressions than the healthy control group. Many tests proved that a smaller amygdala lead to delay in social interaction, which is the biggest symptom of autism.

Read more information on autism and small amygdala

-Amy Shah

Imagine having a beautiful baby, ten years later your child gets cancer and needs a bone marrow donor who can match their bone marrow (25% chance of a sibling match and only 1% chance that a stranger’s will match!) If only you had deposited your baby’s stem cells into the cord blood bank!

The umbilical cord (and all the blood that’s in it) is usually trashed right after the baby is born! But this blood has millions of stem cells in it that can repopulate your baby’s bone marrow after any cancer therapy treatment up to however many years later! Cord blood collection is the extraction of about 250 mL of blood from a baby’s umbilical cord right after they’re born.

This can be done through several different companies. At Cord Partners, it costs about $1700 to use their stem cell bank, but if you have twins, there’s a multiple birth discount! Saving your newborn’s stem cell cord blood in a bank could be the miracle that saves their life!

-Amy Shah