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Lucid Dreaming: Induction, Individual Differences, and Benefits

January 13th, 2011 Comments off


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Lucid dreaming is a dream phenomenon in which the dreamer is fully aware he or she is dreaming. It consists of a few distinct characteristics including having most if not all cognitive abilities, a strong sense of conscious awareness, and full memory of reality and previous dream experiences. Evidence of this is shown through Rapid Eye Movement (REM) sleep. In the REM stage of sleep, eye movements in reality correspond with eye movements in the dream state. For example, a participant in a study becomes lucid in a dream, and can make specific eye signals to researchers showing them the participant has entered a lucid dream state. Various techniques can be used to induce lucid dreaming, such as asking throughout the day “am I dreaming? ” in the hopes of asking that same question in a dream. Dream signs, such as teeth falling out, or text changing can serve as a signal that it is a dream, and can induce lucidity in dreamers. There are some individual differences that exist with lucid dreamers. It has been found that those with a high internal locus of control report have more frequent dream recall and lucidity; those with an external locus of control have just the opposite. The benefits of lucid dreaming are potentially vast, but recent research has focused primarily on reducing the frequency of nightmares in those who have frequent night terrors. It has also been shown to potentially lower emotional disturbances such as stress and anxiety if practiced properly.

Lucid Dreaming: Induction, Individual Differences, and Benefits

Defining Lucid Dreaming

Lucid dreaming can be simply defined as an altered dream state. It can also be called conscious dreaming or dreams of clarity, terms stemming from the psychiatrist Fredrik Willems van Eden in 1913 (Holzinger, 2009). More in depth, it can be described as complete awareness while dreaming, so aware that every aspect of the dream can be manipulated and influenced. All sensory input is still available in the dream, and dreamers can touch, feel, taste, see, hear, and smell (Carskadon, 1995). Not only those characteristics, but lucid dreamers can also reason and think clearly; dreamers know they are in this altered state and can do essentially anything they want. This could include anything from flying to walking on the moon. Tholey (1980) describes lucid dreams as having a certain number of specific characteristics: these include being fully aware of the dream, having memory of real life, having most or all cognitive sensory abilities intact, memory of previous lucid dreams, and a strong sense of conscious awareness. In some cases dreamers even report the dream seeming more real than reality itself.

Historically it is a relatively new concept, but Holzinger et al. (2008) notes that Tibetan Buddhists were the first to learn how to induce a similar dream state, by using specific induction techniques. They would use it as a form of meditation and for potentially new abstract experiences. Up until Freud and his theories on dreams would lucid dreaming begin to become a popular and studied subject. On a biological level, Holzinger (et al. 2006) discovered that activity in the left parietal lobe increased during lucid dreaming, an area of the brain related to self-awareness.

Today therapeutic uses for lucid dreaming are being widely studied as well as methods used to induce them. Benefits can range from the treatment of nightmares, or night terrors, to relieving stress in everyday life (Holzing et al. 2009). According to La Berge (1980), lucid dreaming may be difficult, but is indeed a skill that can be learned and applied through various methods. Schredel Erlachor(2004) reported that four out of every five people have reported having at least one lucid dream at some point in their life. How then if so many people report a lucid dream, along with those who can do it on demand while sleeping, can it be proven to exist?

Evidence of Lucid Dreaming

In 1978, Hearne conducted his famous experiment in which he recorded eye movements while a subject was sleeping, becoming the first to discover Rapid Eye

Movement (REM) sleep. This gave way to the first scientific evidence of lucid dreaming in 1988 as Piller (2009) notes that a group of researchers through an experiment discovered that while dreaming REM sleep corresponds with the eye movements the subject was making in their dream. They also discovered that breathing patterns and intensity was the same in the dream as in reality depending on the activity.

In another study, Erlacher Schredl (2004) conducted an experiment to determine whether or not cardiovascular exercise in a lucid dream had any physical cardiovascular correlates in reality. They had five participants who could consistently and reliably lucid dream and had them stay in a controlled environment sleep laboratory for 2-4 consecutive nights. While dreaming they were to perform a specific exercise while lucid, that exercise being squats. The participants were monitored while sleeping, and when they became lucid they were to give a specific eye command, in this case moving their eyes left to right a number of times, signaling to the researchers that they were going to begin performing the exercise. They would then begin performing the squats, ten repetitions, then do the specific eye signal, wait 25 seconds, then perform the exercise again, then stop giving the eye signal in each stage.

In conclusion of their study it was reported that physical exercise performed while lucid dreaming does moderately correlate with physical activity in waking life such as a

moderately increased heart rate.

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Lucid Dreaming: Induction, Individual Differences, and Benefits (Part 2)

January 13th, 2011 Comments off


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They also found that respiration rates, such as breathing faster, would increase while performing intense dream exercise. This particular study clearly shows the evidence for the existence of lucid dreaming, with the lucid dreaming participants performing specific eye movement tasks being recorded while dreaming that cannot be disregarded.

Lucid Dreaming Induction

There are a variety of ways for one to induce lucidity in oneself. While there are many techniques to choose from, and many may have evidence of success, but there have been few studies that evaluate the effectiveness of such techniques. Paulson Parker (2006) mention this fact, they also note that the specific conditions required for studying lucid dreaming are hard to come by, and many researchers are unable to have the opportunity to be in such an environment. This environment usually consists of using a sleep laboratory with specific control conditions and a large number of participants. With this controlled environment, researchers have to rely on participants own recollection of their dreams. They also mention that the majority of lucid dreams are induced by some type of dream sign. This sign is usually abstract in nature and serves as a visual key that the dreamer is in a dream. An example could be looking at a watch one moment, and then looking at it again; after looking at it the second time, the time on the watch may change

drastically signaling to the dreamer they are in a dream. Dream signs are key to recognizing being in a dream.

A dream journal is one of the most common methods used to help a dreamer recognize these dream signs. Dreams are written in a journal everyday immediately upon waking to recall as much of the dream as possible. Over time, after amassing a collection of dream entries, the journal is scanned thoroughly for common occurrences which can be considered dream signs. Of course to maintain such a journal, the dreamer needs to have a great motivation to do so (Paulson Parker, 2006).

This dream journal technique is usually maintained for a number of weeks, over this time dream recall, or simply having a better memory of dreams, tends to greatly improve. Once successful dream recall has occurred, a variety of methods can utilize this information and help the dreamer achieve consistent lucid dreaming. Tholey (1989) came up with the technique of reflection. This involves the dreamer constantly asking themselves throughout the day “Am I awake? ”, “Am I dreaming? ” This is done in the hope of the dreamer asking the same questions while dreaming to induce lucidity. This same technique can be used in different ways as well, such as pinching an arm throughout the day, and if done in a dream, no pain is felt serving as a signal for the dreamer. Research on this technique has found that it is somewhat effective in non-lucid dreamers, but only truly shines when used with

consistent dreams who can already achieve lucidity. Price et al. (1991) notes that while techniques such as reflection may have some use, there are nearly no studies that provide valid and significant research that they always work.

LaBerge Levitan (1995) performed research on such reality testing techniques, but no statistical significances were found. LaBerge (1980) also added to the reflection technique, making it a reflection-intention method. In this extended method there are four stages. These include planning to reality test, acting it out, thinking about dreaming, and then think about what to dream about while lucid. Yet still with this technique, there is a lack of legitimate research proving its effectiveness. Another technique discussed was the wake-initiated lucid dream, termed WILD. With this technique dreamers may wake themselves during a REM cycle, and then go back to sleep. Yet the key here is to remain completely aware while going back to sleep such that the dreamer may instantaneously enter a lucid dream. The body needs to be relaxed while the mind awake and aware. Dreamers may envision something such as constantly going down a set of stairs to keep their mind from wandering and drifting into sleep without knowing it.

To elaborate on some recent induction research, Paulson Parker (2006) conducted a two week study with 31 participants to evaluate their lucidity progression after introducing them to some induction techniques. They first gave the participants an

elaborate questionnaire to assess the participants dreaming habits, and ability to recall dreams. The technique used was similar to the reflection-intention method, instructing the participants to do reality checks morning, day, and night at least 5-10 times throughout the day. For this reality check they were to read a section of text, and then look back at it, if it’s the same it’s not a dream. This is because in a dream read text will often completely change spontaneously. They also were made to imagine what they would do while dreaming, and had to fill out a journal entry immediately after waking up. The journals were to include the

time of going to sleep and awakening, along with the amount of dreams recalled. To gather data the researchers had the participants submit all information gathered on-line through the use of elaborate e-mails. Out of the 31 participants, 11 dropped out mainly for no given reasons. Of the remaining 20, none had any significant experience lucid dreaming, with only 13 of them ever having remembered having a lucid dream.

The results of the research concluded with positive correlations.

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Lucid Dreaming: Induction, Individual Differences, and Benefits (Part 3)

January 13th, 2011 Comments off


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After using repeated measures within-groups statistical tests, it was found that there were slight increases in dream recall frequency in week one. After week two significant increases in dream recall frequency were shown, along with some participants reporting having one or more lucid dreams within the short two week time span of the study. Overall, the study proved to be a success, but due to the lack of participants, more research on the methods

used would of course be needed. The methods described as compared to the many others, have proven to be the most effective, and have had the most significant research which correlates to lucidity success. Yet with this variety of methods, some still cannot lucid dream, some learn to after months of time, some almost immediately, and some seem to have the innate ability to become lucid at will while dreaming. With this variety of individual dreaming, then what individual differences contribute to the varying degrees of lucidity?

Individual Differences in Lucid Dreaming

In looking at the individual differences in lucid dreams, there have been very few studies that have looked at specific personality differences that may contribute to more or less lucid dreaming. Patrick and Durdell (2004) conducted a study that showed the differences in non-lucid dreams, frequent lucid dreamers, and occasional lucid dreams. They first give some background on the topic, mentioning that it was Freud who introduced the continuity hypothesis, which states that dreams reflect waking occurrences in daily life. This would mean that daily experiences are reflected in dreaming. They also mention that conflicts in daily life may have an impact on frequency of bad dreams, or nightmares. These factors are important to consider because they may all have an effect on the ability to lucid dream. Such as one who has consistent conflicts throughout the day may have trouble

sleeping with nightmares and such therefore impairing their ability to easily recognize dream signs in their dreams.

Internal locus of control was another notable characteristic that frequent lucid dreamers have (Lefcourt, 1982). An external locus of control is a characteristic in which one consistently believes their life is controlled by fate, or destiny. It seems obvious that this would lead toward less control in dreams, as the dreamer would feel they are unable to control their dreams, and indeed it is true. Internal locus of control, a personality characteristic which is essentially the opposite of the external locus of control, involves the

person consistently believing they have complete control over their lives and every decision they make and events that happen are not fate, but a combination of expected scenarios.

Blagrove and Tucker (1994) noted that individuals with a strong internal locus of control do have much more frequent lucid dreams than those with an external locus of control. Those who had an internal locus of control had a strong belief of control, that belief is reflected in their dreaming, in that they believe they have the power and control to change and modify their environment. While those with the external locus of control felt as though they had no power to control what happens in their

dreams, when control the most essential facet of lucid dreaming. They also mention that frequent dream recall is essential for dreaming, whether or not it is from using a dream journal, those with an internal locus of control were shown to have stronger dream recall.

In Patrick and Durrdell’s (2004) study they had 50 participants who were split into three grouped categories above. The three groups of dreamers were analyzed on their locus of control, need for cognition, and field independence-dependence. They were analyzed using a written test which contained a variety of questions concerning dreaming in general, lucid dreaming, and personality characteristics.

Their results indicated, just as mentioned above, that those with an internal locus of control showed strong statistical significance in having most lucid type dreams. Need for cognition was defined as paying attention to environment, and paying close attention to things, such as listening to what a speaker giving a speech is saying rather than how good they look. A low need for cognition was defined as not being as aware of things as one should, such as listening to a speaker while only thinking about the speakers looks or their attire rather than actually listening to what they have to say. It was found that those with a higher need for cognition reported more dream activity and lucidity as opposed to those with a low need for cognition. In comparing field independence, which was described as being independent towards ones environment, and field dependence, which was described

as characteristic in which one feels they have no control over their environment and the events that occur, field independence was found to be a prominent feature in the frequent lucid dreamers.

Overall, the study shows and supports the fact that those who are more confident, independent, aware, and feel in control of themselves and their surroundings reflect those characteristics in their dreams showing more lucidity and dream recall. Individual differences clearly have an effect on the ability to lucid dream, as the various personality traits that people have, along with the vastly different lives people have which may or may not involve frequent conflicts throughout the day or no conflicts, can all have an effect on lucid dreaming (Patrick Durrdell, 2004).

Benefits of Lucid Dreaming

The potential benefits of lucid dreaming are vast, but the most recent and reliable research has mainly focused on the reduction of nightmares for those who experience them frequently.

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Lucid Dreaming: Induction, Individual Differences, and Benefits (Part 4)

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Along with reduction of nightmares, emotional disturbances such anxiety or depression have been shown to decrease with frequent lucid dreaming training. Roberts (et al. 2009) notes that constant nightmares may increase rates of anxiety in everyday life. Learning how to lucid dream may reduce the frequency of nightmares, in turn decreasing

rates of anxiety. Galvin (1993) did an in depth study using hypnotic techniques on 8 participants with frequent nightmares in an intensive 9 week program.

Participants were made to keep a frequent dream journal throughout the testing period, concluding with 446 dream reports after the study. They also all had some distinct characteristics, being that they all were involved in some sort of creative work, such as an artist or musician. It is noted that those characteristics led the participants to thinking of themselves in an unusual way, as in thinking they are not quite normal. This possibly had an effect on the frequent night terrors they reported. Emotional sensitivity was another distinct characteristic they all possessed, possibly leading them to be constantly frightened, and in turn leading them towards having frequent nightmares. The most common characteristic all participants had was a troubled adolescence, such as being bullied or picked on.

Their main goal was to teach the participants techniques on lucid dreaming, and use these techniques to face and conquer the fears they have in their nightmares. Usually, nightmares are uncontrollable and bring intense fear to the dreamer, with the ability to frequently dream recall, and eventually lucid dream frequently, those effects of the nightmare are the complete opposite. The results of this study support the hypothesis that

teaching techniques of lucid dream are indeed effective in reduction the frequency and intensity of nightmares.

In a similar study done by Victor Jan Van Den (2006), 23 consistent nightmare victims suffering from posttraumatic stress disorder participated in a study using lucid dreaming induction methods to overcome their frequent nightmares. A questionnaire was given at the start of the study to assess the participants stress levels along with their sleeping and dreaming habits. Participants were then given training and instruction on lucid dreaming treatment. This treatment not only consisted of lucid dreaming induction techniques, but also basic psychological information on how to control and change nightmares. At the 12 week follow up of the intervention, the participants were required to fill out another similar questionnaire. It was found that the participants had a significant reduction in nightmare frequency; however, they had no changes in sleep quality, or lucidity. The results indicated that it was unclear whether it was the lucid dreaming techniques or therapeutic intervention that provided the changes in nightmare frequency.


The field of lucid dreaming is continuously progressing. It is still relatively new, and may offer a vast amount of potential therapeutic and individual benefits. Much of the

current scientific research being done is unreliable and hard to come by. Many specific conditions are required for lucid dreaming research, such as sleep laboratories if research is to be done in the lab, which requires much of a participants time. The techniques required to induce lucid dreaming are time consuming and often unsuccessful. Personal accounts of their therapeutic lucid dreaming interventions are also often unreliable, and much is expected from the participant. Through constant updating and improving, those techniques will continue to work better and more efficient. Benefits such as the reduction of night terrors in nightmare sufferers are only the beginning (Holzinger, 2009).


Blagrove, M. and Tucker, M. 1994. Individual differences in locus of control and the reporting of lucid dreaming. Personality and Individual Differences 16, pp. 981–984.

Carskadon MA (1995) Encyclopedia of Sleep and Dreaming. New York: Simon Schuster MacMillan.

Erlacher, D. Schredl, M. (2008). Cardiovascular Responses to Dreamed Physical Exercise During REM Lucid Dreaming. Dreaming, 18(2), 112-121.

Galvin, Franklin Jerome (1993). The effects of lucid dream training upon the frequency and severity of nightmares. Ph. D. dissertation, Boston University, United States Massachusetts. Retrieved March 24, 2010, from Dissertations Theses: Full Text.

Holzinger, B. (2009). Lucid dreaming – dreams of clarity. Contemporary Hypnosis, 26(4), 216-224.

Holzinger, B. LaBerge, S. Levitan, L. (2006). Psychophysiological Correlates of Lucid Dreaming. Dreaming, 16(2), 88-95.

Huston, Holly Louise. 1997. Personality characteristics influencing archetypal dream recall in vivid dream types. Ph. D. dissertation, Texas A&M University, United States Texas.

Kueny, Sallie Reid. 1985. An Examination of Auditory Cueing in REM Sleep for the Induction of Lucid Dreams. Ph. D. dissertation, Pacific Graduate School of Psychology, United States California.

LaBerge, S. (1980). Lucid dreaming as a learnable skill: A case study. Perceptual and Motor Skills, 51, 1039-1042.

LaBerge, S. Levitan, L. (1995). Validity established of dreamlight cues for eliciting lucid dreaming. Dreaming, 5, 159-168.

Paulsson, T. Parker, A. (2006). The effects of a two-week reflection-intention training program on lucid dream recall. Dreaming, 16, 22-35 10.

Piller, Robert. (2009). Cerebral Specialization During Lucid Dreaming: A Right Hemisphere Hypothesis. Dreaming. Vol 19(4), pp. 273-286.

Price, R. LaBerge, S. Bouchet, C. Ripert, R. Dane, J. (1991). The problem of induction: A panel discussion. Tenth Anniversary Issue of Lucidity Letter.

Roberts, Jan; Lennings, C. J. Heard R. (2009). Nightmares, Life Stress, and Anxiety: An Examination of Tension Reduction. Dreaming. 16(4), 81-107.

Schredl, M. Erlacher, D. (2004). Lucid dreaming frequency and personality.

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Lucid Dreaming: Induction, Individual Differences, and Benefits (Part 5)

January 13th, 2011 Comments off


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Personality and Individual Differences, 37, 1463–1473.

Tholey, P. (1989). Overview of the development of lucid dream research in Germany. Lucidity Letter, 8, 1-30.

Tholey, P. (1980). Conscious Dreams as an Object of Emperical Examination. Gestalt Theory, 2, 175-191.

Victor I. S. Jan van den, B. (2006). Lucid Dreaming Treatment for Nightmares: A Pilot Study. Psychotherapy Psychosomatics, 75(6), 389-394.

Zadra, Antonio (1991). Lucid dreaming as a learnable skill: Empirical and clinical findings. M. A. dissertation, McGill University (Canada), Canada.

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Is Hair Cell Regeneration in Humans Possible?

September 5th, 2010 Comments off


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Hair cell damage in the inner ear is becoming increasingly more common. More children, and adults, are exposing themselves to loud noises via concerts or headphones, and there are other various environmental factors as well. There are medicines and ototoxins, diseases, and overstimulization issues that also contribute to hair cell damage. Since this is becoming a more common issue, researchers are developing ways to regenerate the hair cells within the inner ear. This is necessary because the loss of hair cells can lead to hearing loss. Additionally, it can lead to problems with balance and the overall quality of life. While hair cell regeneration in humans is a possibility of the future, it will not be successful without further research and development.


The loss of hair cells in the inner ear leads to a sensorineural hearing loss. This type of loss usually occurs in the cochlea, which is within the inner ear and it is vital to processing sound as it is the primary organ of hearing (Cotanche, 2008). This type of loss is very difficult to treat as hair cells do not reproduce on their own, so once they are lost, the loss is permanent. Sensorineural hearing loss occurs due to hair cell loss, damage, hair cell degeneration, and other various sources (Izumikawa, Minoda, Kawamoto, Abrashkin, Swiderski, Dolan, et al. 2005).

To explain the difficulty in regenerating hair cells, it is best to cover some of the anatomy of how the cochlea works in the hearing process. This will provide a better understanding of treatment. Once sound enters the ear, it changes from acoustic to mechanical energy in the middle ear. From the middle ear, it is sent to the inner ear where it changes from mechanical to hydraulic energy. When the wave of energy reaches the cochlea, it changes back to mechanical energy, and then chemical energy within the hair cells. The transduction process is vital for hearing, as the brain cannot process acoustic energy. If the chemical process is absent or minimal, the brain cannot process the sound, and thus hearing will be impaired. (Hume, Oesterlie, Raible, Rubel, & Stone, 2010).

In cell development, there are sensory and nonsensory supporting cells (Ozeki, Oshima, Senn, Kurihara, & Kaga, 2007).   They alternate in their development, with nonsensory supporting cells at the bottom holding the sensory hair cells into place.   According to the lateral inhibition theory of cell development, the supporting cells replace the hair cells when they are damaged, and then more supporting cells are recreated as needed.   The supporting cells divide without assistance to replace the missing cells.   This is the ideal cure to hair cell regeneration and knowledge of how this process works is vital to researchers.   With this information, it enables them to find a way to recreate this cell division process.   In the bird’s organ of hearing, they are capable of this self repair.   However, in humans it is still being assessed as merely a possibility.   The problem is that this type of cell division does not happen spontaneously in the human organ of hearing.   Researchers are still developing ways to make this event happen through the use of growth hormones, stem cells, genes, etc.   (Walshe, et al. 2003)

            As mentioned, human hair cells do not regenerate on their own, and this was because not all cells have the ability to divide (White, Doetzlhofer, Yun Shain, Groves, & Segil, 2006).   One of the biggest challenges for researchers was getting cells to divide that normally do not possess this ability.   Once the hair cells were damaged or lost, it resulted in hearing loss, or even the possibility of a cochlear implant to enable hearing.   Again, hearing loss may cause balance issues as there are hair cells in the vestibular system.   (Ozeki, et al. 2007)

            Why are birds able to regenerate cells and humans cannot?   Birds, however, had the ability to regenerate hair cells automatically, once they were lost or damaged.   Researchers are currently still studying these animals to find out why they possess this ability.   Thus far, they have discovered that birds were able to restore neural connections as a functional unit.   This means that instead of having different cells, performing various functions and regenerating separately, in birds they regenerated as a whole. (Walshe, et al. 2003).

            A more in-depth look at bird’s regenerative ability revealed that once a bird’s hair cell was lost or damaged, the auditory nerve retreated from the cell (Matsui & Ryals, 2005).   Once the innervation was removed, the process of replacing the cell could begin.   A signal came down from the Notch, notifying the bird’s organ of hearing to begin the replacement process (Stone & Rubel, 2000).   Bird’s have a different organ of hearing than humans.   The basilar papilla in a bird is similar to the cochlea in a human.   It controls the hearing process and in their case, hair cell regeneration.   (Hume, Oesterlie, Raible, Rubel, & Stone, 2010). Their hair cells then had the ability to proliferate, or to multiply excessively as needed to repair themselves.   After the cells multiply, they transdifferated or replaced the dead cells, and then they were re-innervated by the auditory nerve.   This is an amazing process that occurs automatically within birds. (Stone & Rubel, 2000)

            When looking at possibilities for hair cell regeneration within humans, proliferation and transdifferation are two proposed options for repair and both are dependent upon each other.   During the proliferation process, cells multipled rapidly in order to replace the damaged or dead cells.   However, in the transdiffereration process, the proliferated cells were stimulated in an attempt to repair the damaged cell.   Stimulation allowed the cell to divide, and while the new division replaced the supporting cell, the supporting cell took place of the damaged hair cell.   One of the main concerns with this process was the restructuring of the cells.   Would this change alter the organ of Corti in humans?   If it does, what is the affect this would have on hearing?   The only way this process will be effective is if the transdifferated cell replaces itself.   What could happen if the cell does not replace itself?   Would there be a bunching of supporting cells, or even possibly missing supporting cells?   If supporting cells are missing, will there be a space and nothing to hold on to the newly generated hair cell?   These are questions that researchers are still trying to answer before conducting experiments in humans, and most definitely before approving this type of resolution as valid for hair cell regeneration. (Mastui, et al. 2005).

                To recreate the proliferation process in humans, genes must be present or injected as this does not happen naturally (Matsui, et al. 2005).     Additionally, Kopke, Jackson, Geming, Rasmussen, Hoffer, & Frenz (2001) found that insulin can increase the cell response.   Thus, if the cell does not proliferate after being exposed to the gene, insulin can be added to increase the likelihood that it will divide.

            The primary gene involved in proliferation is Atoh1.   Once injected into the organ of Corti, it can function as a non-expressing supporting cell, an expressing hair cell, or it can even be expressed but not function as a sensory cell (Ozeki, et al. 2007).   Atoh1 regulates “common cellular precursor’s” in cell differentiation, which is why it is seen as the primary gene in hair cell regeneration.   (Izumikawa, et al. 2005).

                Matsui et al. (2005) used microarray to establish which gene was expressed and its location.   This assessment was great for inner ear analysis given the specificity and intricate structures.   Additionally, they were able to look at transcription factors to determine which genes played specific roles.   Their results found that there were six-hundred factors in both the vestibular and auditory system, and only forty in one organ.  

            Another theory involved in hair cell regeneration or cell development, is the use of growth factors.   They are associated with the differentiation and proliferation process, but suggest that instead of genes, these growth factors cause the regeneration (Kopke, et al. 2001). Matsui et al. (2001) suggests that macrophages, or white blood cells, are housed within tissue and they go to the dying cells.   Once in the vicinity, they either repair or remove the dying cell.   This process most frequently occurs after some type of trauma.   A flaw with this theory was that the researchers were unclear of the current function of the macrophages within the inner ear of humans.   Obviously, this process was not currently working spontaneously, as humans cannot regenerate cells without assistance.   However, researchers would like to better understand this process within the inner ear to determine if hair cell regeneration is possible by the production of growth factors in general. (Oregon Health & Sciences University, 2008).

                Other significant contributors to the process of proliferation are leukocytes-activators or “progenitor cell proliferation” (Stone & Rubel, 2000).   There were three subtypes of progenitors that may play a role in this process.   The first was the neuronal-colony-forming type which were the most similar to stem cells (Stone, Choi, Wooley, Yamashita, Rubel, 1999).   The second and third type were the progency and mash1 which had very little proliferate ability. These variances in progenitor cells may explain the differences in regeneration.   Furthermore, it may also explain why other animals can regenerate while humans cannot.   Additional research needs to be conducted to determine the exact role these ‘activators’ play in the proliferation process.   (Stone & Rubel, 2000).

            The transdifferation process, in comparison to proliferation, is about as complex.   In this process, the cells are transformed from supporting cells into hair cells (Ozeki, et al. 2007).   This process can be initiated by the use of the gene Atoh1 as well as Retinoic acid (Kopke, et al. 2001) and (White, et al. 2006).   One flaw in this process is that the hair cell may not always be functional after transformation (Kopke, et al. 2001).   This is because the cell needs a brain-derived neurotrophic factor which is provides a neurological connection and lack of it can prevent function of the generated hair cell.     Furthermore, it is important for vestibular ganglion neurons to survive, it protects neurons from ototoxins which may cause future damage to the cell, and when combined with insulin and retinoic it is known to cause vestibular function.   Ideally, this means once we get control of how this process works, we could possibly treat some balance disorders.   Given all of this information, it is important to note that neural elements are not needed for the regeneration process itself and it does not affect the production of hair cells; it is only necessary for function and innervations of the hair cell (Stone & Rubel, 2000).

            Now that there is a better understanding of the anatomical process involved in the inner ear, it is best to assess the proposed treatments for human hair cell regeneration.   The first treatment was the reconstruction of the organ of Corti.   Ideally, Ozeki et al. (2007) found that doctors should inject progenitor cells into the inner ear.   After the injections, the hope was that the cells would differentiate on their own into supporting or hair cells as necessary.   This meant that the supporting cells would differentiate into hair cells, and more supporting cells would be created.

The second proposed treatment was stem cell transplant. This became a possibility because stem cells had many properties that were beneficial to humans. Additionally, they had very similar properties to supporting cells, could generate in large numbers, and could take the form of different types of cells (Matsui, et al. 2005). One drawback of this treatment was the uncertainty if the new cell would be functional. An additional avenue of this type of treatment was to find out if progenitor cells could act like stem cells (Stone & Rubel, 2000).

As researchers progress in finding a successful treatment for regenerating hair cells within the inner ear, there are still many questions to be answered about the process. For one, why do only our vestibular cells show the possibility of regeneration (Matsui, et al. 2005)? This is interesting because Matsui et al. (2005) found that hair cells regenerate spontaneously in the vestibule but not in the cochlea. Is it possible that vestibular cells do not need a replacement cell? Why is it that the auditory system cells do not regenerate (Rubel, 2005)? Do supporting cells lack a replacement cell; are there unknown gene functions; are signals being blocked that regulate cell regeneration (White, et al. 2006)? Until these questions are answered, significant research still needs to be conducted in this area of treatment.

The possibility that hair cell regeneration will someday lead to the restoration of hearing still exists. Many avenues have been addressed by various researchers ranging in everything from genes, growth factors, and stem cell replacement. However, if research reaches the point where hair cell regeneration is successful, this does not resolve the issue of whether hair cell regeneration alone can restore hearing in a hearing impaired individual. There is still the idea that not all regenerated cells will be functional and innervated, and the regeneration process may not provide full regeneration. Thus, the result will still be a hearing impairment. Unless hair cell regeneration can overcome all of these obstacles, the need for a cochlear implant may still be necessary.


1. Cotanche, D. (2008). Genetic and pharmacological intervention for treatment/prevention of hearing loss. Journal of Communication Disorders, 41(5): 421-43.

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Is Hair Cell Regeneration in Humans Possible? (Part 2)

September 5th, 2010 Comments off


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2. Hume, Oesterlie, Raible, Rubel, & Stone. (2010). Inner ear hair cell regeneration. Virginia Merrill Bloedel Hearing Research Center. Retrieved March 20, 2010 from http:// depts. washington. edu/hearing/InnerEarHairCellRegeneration. php

3. Izumikawa, M. Minoda, R. Kawamoto, K. Abrashkin, K. Swiderski, D. Dolan, D. et al.

(2005). Auditory hair cell replacement and hearing improvement by Atoh1 gene therapy in deaf mammals. Nature Medicine, 11(3), 271-276.

4. Kopke, R. Jackson, R. Geming, L. Rasmussen, M. Hoffer, M. Frenz, D. et al. (2001). Growth factor treatment enhances vestibular hair cell renewal and results in improved vestibular. Proceedings of the National Academy of Sciences of the United States of America, 98(10), 5886.

5. Matsui, J. & Ryals, B. (2005). Hair cell regeneration: An exciting phenomenon … But will restoring hearing and balance be possible? Journal of Rehabilitation Research & Development, 42187-198. Doi:10. 1682/JRRD. 2005. 01. 0008.

6. Oregon Health & Sciences University. (2008). Treatment for hearing loss? Scientists grow hair cells involved in hearing. ScienceDaily. Retrieved March 20, 2010 from www. sciencedaily. com/releases/2008/08/080830005613. htm

7. Ozeki, H. Oshima, K. Senn, P. Kurihara, H. & Kaga, K. (2007). Development and regeneration of hair cells. Acta Oto-Laryngologica (Supplement), 12738-44. Doi: 10. 1080/03655230701597200

8. Rubel, E. (2005). Hair cell regeneration: look into the future. Journal of Acoustical Society of America, 117(4), 2377-2377.

9. Stone, J. Choi, Y. Wooley, S. Yamashita, H. Rubel, E. (1999). Progenitor cell cycling during hair cell regeneration in the vestibular and auditory epithelia of the chick. Journal of Neurocytology, 28, 863-876.

10. Stone, J. & Rubel, E. (2000). Cellular studies of auditory hair cell regeneration in birds. Proceedings of the National Academy of Sciences of the United States of America, 97(22), 11714.

References Continued

11. Walshe, P. Walsh, M. & McConn Walsh, R. (2003). Hair cell regeneration in the inner ear: a review. Clinical Otolaryngology & Allied Sciences, 28(1), 5-13. Doi:10. 1046/j. 1365-2273. 2003. 00658. x.

12. White, P. Doetzlhofer, A. Yun Shain, L. Groves, A. & Segil, N. (2006). Mammalian cochlear supporting cells can divide and trans-differentiate into hair cells. Nature, 441(7096), 984-987. Doi: 10. 1038/nature04849.

13. Viastarakos, P. Nikolopoulos, T. Tavoulari, E. Papacharalambous, G. (2008). Sensory cell regeneration and stem cells: what we have already achieved in the management of deafness. Otology & Neurotology, 29(6): 758-68.

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