Category: Tinnitus

Young people who listen to personal music players for several hours a day at high volume could be putting their hearing at risk, warns an expert in an editorial published online in the British Medical Journal.

Professor Peter Rabinowitz from Yale University School of Medicine says that personal music devices such as MP3 players can generate levels of sound at the ear in excess of 120 decibels, similar in intensity to a jet engine, especially when used with earphones that insert into the ear canal.

The use of these devices is high in young people — more than 90% in surveys from Europe and the United States — and "has grown faster than our ability to assess their potential health consequences," he writes.

However, evidence that music players are causing hearing loss in young people is mixed, suggesting that the true population effects may only now be starting to be detectable, says the author.

Other health effects may also need to be considered. For example, some studies have shown that use of personal music players can interfere with concentration and performance when driving, in a similar way to mobile phones.

Although evidence based guidance is lacking, Rabinowitz believes that the importance of hearing loss as a public health problem makes it reasonable to encourage patients of all ages to promote "hearing health" through avoidance of excessive noise exposure.

He also suggests it would be prudent to remove earphones while driving and performing other safety sensitive tasks, and calls for more comprehensive and ongoing surveys of the hearing health of young people.

"Personal music players provide a reminder that our hunger for new technology should be accompanied by equally vigorous efforts to understand and manage the health consequences of changing lifestyles," he concludes.

Heightened activity between the emotional and auditory parts of the brain explains why the sound of chalk on a blackboard or a knife on a bottle is so unpleasant.

In a study published today in the Journal of Neuroscience and funded by the Wellcome Trust, Newcastle University scientists reveal the interaction between the region of the brain that processes sound, the auditory cortex, and the amygdala, which is active in the processing of negative emotions when we hear unpleasant sounds.

Brain imaging has shown that when we hear an unpleasant noise the amygdala modulates the response of the auditory cortex heightening activity and provoking our negative reaction.

"It appears there is something very primitive kicking in," says Dr Sukhbinder Kumar, the paper's author from Newcastle University. "It's a possible distress signal from the amygdala to the auditory cortex."

Researchers at the Wellcome Trust Centre for Neuroimaging at UCL and Newcastle University used functional magnetic resonance imaging (fMRI) to examine how the brains of 13 volunteers responded to a range of sounds. Listening to the noises inside the scanner they rated them from the most unpleasant — the sound of knife on a bottle — to pleasing — bubbling water. Researchers were then able to study the brain response to each type of sound.

Researchers found that the activity of the amygdala and the auditory cortex varied in direct relation to the ratings of perceived unpleasantness given by the subjects. The emotional part of the brain, the amygdala, in effect takes charge and modulates the activity of the auditory part of the brain so that our perception of a highly unpleasant sound, such as a knife on a bottle, is heightened as compared to a soothing sound, such as bubbling water.

Analysis of the acoustic features of the sounds found that anything in the frequency range of around 2,000 to 5,000 Hz was found to be unpleasant. Dr Kumar explains: "This is the frequency range where our ears are most sensitive. Although there's still much debate as to why our ears are most sensitive in this range, it does include sounds of screams which we find intrinsically unpleasant."

Scientifically, a better understanding of the brain's reaction to noise could help our understanding of medical conditions where people have a decreased sound tolerance such as hyperacusis, misophonia (literally a "hatred of sound") and autism when there is sensitivity to noise.

Professor Tim Griffiths from Newcastle University, who led the study, says: "This work sheds new light on the interaction of the amygdala and the auditory cortex. This might be a new inroad into emotional disorders and disorders like tinnitus and migraine in which there seems to be heightened perception of the unpleasant aspects of sounds."

Most Unpleasant Sounds

Rating 74 sounds, people found the most unpleasant noises to be:

1. Knife on a bottle
2. Fork on a glass
3. Chalk on a blackboard
4. Ruler on a bottle
5. Nails on a blackboard
6. Female scream
7. Anglegrinder
8. Brakes on a cycle squealing
9. Baby crying
10. Electric drill

Least Unpleasant Sounds

• Applause
• Baby laughing
• Thunder
• Water flowing

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Journal Reference:

1. S. Kumar, K. von Kriegstein, K. Friston, T. D. Griffiths. Features versus Feelings: Dissociable Representations of the Acoustic Features and Valence of Aversive Sounds. Journal of Neuroscience, 2012; 32 (41): 14184 DOI: 10.1523/JNEUROSCI.1759-12.2012

Noise can be distracting, especially to a person trying to concentrate on a difficult task. Studying annoying noises helps architects design better building environments and policy makers choose effective noise regulations. To better understand how short noise bursts affect humans' mental state, researchers from the University of Nebraska-Lincoln played quarter-second-long white noise clips to test subjects as they worked on arithmetic problems. The researchers noticed a slight general trend toward lower performance when louder noises were played, and also identified sound level ranges that caused participants to report significant levels of annoyance.

The researchers report their findings at the 164th meeting of the Acoustical Society of America (ASA), held Oct. 22 — 26 in Kansas City, Missouri.

The motivation for the research came from NASA's low-boom supersonic aircraft program. Sonic booms, generated when aircraft traveling faster than the speed of sound leave cones of compressed air in their wake, are loud and potentially unnerving. In 1964, when the Federal Aviation Administration starting flying supersonic jets regularly over Oklahoma City as part of a test called Operation Bongo, many citizens filed complaints and damage claims. NASA is now working on developing aircraft that create softer booms, but is it not clear at what volume regular booms, as might be created by commercial supersonic aircraft flying over land, would be acceptable.

Lily Wang, an architectural acoustician at the University of Nebraska — Lincoln, worked with her graduate student Christopher Ainley to design an experiment to test how noise bursts affect the performance and perceptions of test subjects. Previous studies had looked at loud noises of more than 80 decibels (dB), louder than an average vacuum cleaner, and found a clear effect on subjects' ability to solve arithmetic problems. Wang and her team reduced the volume to see if they could find a threshold value under which the noise would not significantly affect the participants. Twenty-seven test subjects were asked to memorize 6-digit numbers, and then, when shown a 4-digit number, the subjects had to subtract the second number from the first number in their heads and type the answer on a keyboard. Occasionally the researchers would play a quarter-second burst of noise while the second number appeared on the screen.

The researchers tested noise bursts in the range of approximately 50 — 80 dBA. The dBA unit indicates that the volume was measured with a filter used to approximate the human ear's response to sound. The noise levels were comparable to about the sound level on a suburban street corner at the low end, to vacuum-cleaner loud at the high end. While the test subjects solved a lower percentage of problems correctly when interrupted with a noise at the louder end of the spectrum, the difference was not enough to be statistically significant. However, there was a significant difference in the levels of annoyance that the participants reported when quizzed afterwards about their perceptions of the noise environment. "The test subjects sort of adjusted to the quieter booms, but the louder ones remained jolting," says Wang. "This suggests that the acceptable noise from sonic booms should not be higher than 70 dBA once it gets inside the house."

The researchers' lab did not have the necessary equipment to mimic the very low-frequency component of the noise produced by sonic booms, Wang notes, but the work helped to quantify the effect of the short duration characteristic of the booms. As a next step, the researchers hope to study perceptions of the rattling component of noise that is often associated with supersonic jets passing overhead.

BUFFALO, N.Y. — Researchers in the University at Buffalo Center for Hearing and Deafness have shown for the first time that a compound called leupeptin may help protect against the noise-induced hearing loss caused by living in noisy industrialized societies.

Using an animal model, researchers found that treating the inner ear with leupeptin before exposure to high-level noise, comparable to a jet engine, reduced the loss of sensory hair cells by 60 percent. Hair cells convert sound waves into electrical impulses that are sent to the brain.

Leupeptin, however, did not protect against the damaging effects of the anti-cancer drug carboplatin that can cause deafness in treated patients.

Results of the study, lead by Richard J. Salvi, Ph.D., professor of communicative disorders and sciences in UB's College of Arts and Sciences and co-director of the center, appear in the current issue (Vol. 10, No. 4) of NeuroReport.

"The results are very exciting for two reasons," Salvi said. "First, they provide clues to the cellular events that lead to sensory-cell death in the inner ear. Second, they suggest a potential drug-therapy approach to protecting the ear against sound damage."

Salvi and his colleagues at UB and his collaborators, Alfred Stracher, Ph.D., and Abraham Shulman, Ph.D., both at the SUNY Health Science Center at Brooklyn, have been investigating ways to protect the auditory system from damage via noise and ototoxic drugs, common causes of deafness in Western societies.

This study was based on the knowledge that, in many cases, degeneration of nerve function is caused by a cascade of events, beginning with a trauma that induces an increase of calcium in nerve cells. Excess calcium, in turn, increases the level of enzymes called calpains, which promote the breakdown of proteins and other factors critical to nerve functioning.

"Drugs that inhibit the action of calpains — leupeptin is one — have been shown to decrease or prevent destruction of nerve functioning that results in neuromuscular atrophy in cases of trauma or genetic disorders," Stracher noted.

Salvi and colleagues set out to determine if leupeptin also could protect the sensory hair cells in the ear from noise and ototoxic drugs such as carboplatin — knowing that such insults cause an increase in calpains — and thus prevent hearing loss.

The researchers treated the right cochlea of chinchillas with leupeptin for 14 days. On the fifth day, some of the animals were exposed to noise, at 100 decibels or 105 decibels. The left ears of all animals served as controls. Results from the noise exposure study showed massive loss of hair cells in the ears not treated with leupeptin, while only a few hair cells were missing in the treated ear.

A similar study, designed to determine if leupeptin would protect against hair-cell loss caused by carboplatin, showed leupeptin offered no protection, Salvi said.

Additional researchers on the study were Jain Wang and Dalian Ding, research scientists in the UB Center for Hearing and Deafness.

The research was supported in part by the Martha Entenmann Tinnitus Research Foundation.

ROSSLYN, Va., Sept. 11, 1998 – Imagine an invisible hearing aid that never squeals with feedback and digitally enhances speech while silencing background noise.

Such a device is under development and has been tested in animals with encouraging results. Jonathan Spindel, Ph.D., a biomedical engineer and assistant professor at the University of Virginia's Department of Otolaryngology, is preparing to take the next step toward developing a fully implanted prototype for humans. "Our tests to date have shown that the signals produced with our magnetic hearing device are very nearly those of natural acoustic sound," said Spindel.

The unique device would capture sounds with a miniature microphone implanted in the ear. After passing through a small processing unit and an electromagnetic coil, both also implanted, amplified vibrations would be sent to the inner ear via a tiny magnet attached to the inner ear's round window, a thin membrane at one end of the cochlea.

About as large as a pencil point, the tiny magnet would send vibrations through the cochlea, the fluid-filled organ shaped like a snail shell, and stimulate its thousands of hair cells used in normal hearing. The new device is the first to use an electromagnet to stimulate the inner ear via the round window.

A major feature of Spindel's approach is that the device doesn't obstruct the normal hearing process. "Leaving the middle ear system intact and establishing a second independent input pathway to the inner ear opens the possibility for using the normal acoustic pathway and round window electromagnet simultaneously to establish constructive and destructive sound patterns in the inner ear," said Spindel.

The device could enhance the sound of a person's voice, for example, by generating sound waves matching those of the voice as it reaches the ear. What ultimately reaches the brain and what the user actually hears is the net effect of combining the natural sound patterns with those generated by the magnetic hearing device. In this way, the sound waves from the device amplify the desired sound.

To reduce background noise, however, the device simply generates a sound pattern that mirrors the pattern of the undesirable sound. In this case, when coupled with the natural sound pattern, the net effect the user actually hears is little or no sound at all; each sound wave is the opposite of the other and they cancel each other out.

Spindel said he envisions a human prototype with a separate external control device used to tune in the desired frequencies and tune out unwanted sounds and noise. Changes in the settings would be relayed to the fully implanted hearing device remotely. Further development depends on future funding, said Spindel.

Another advantage of the new magnetic hearing device is eliminating acoustic feedback, or the high-pitched "squeal." "Conventional hearing aids are essentially a microphone, an amplifier and a speaker, very similar to the sound systems at concerts or a public speech," said Spindel. And like those systems, he added, acoustic hearing aids are susceptible to feedback. With feedback, the microphone picks up much of the sound produced from the speaker and feeds it back through the system in a repeating loop, causing a high-pitched squeal. But hearing aids are much more susceptible "because the components of the system are so incredibly close together," said Spindel.

To overcome this, modern acoustic hearing aids rely on a very tight fit to ensure that the sounds produced on one end don't reach the microphone on the other end. But even modern, custom-fitted acoustic hearing aids can loosen with activity and become susceptible to the "squeal", said Spindel.

Because the new hearing device uses magnetic rather than acoustic vibrations, feedback is virtually eliminated.

 ST. PAUL, MN – Tinnitus -– a ringing in the ears that affects millions of people -– may be related to visual as well as auditory brain activity, according to a study in the February 27 issue of Neurology, the scientific journal of the American Academy of Neurology. Researchers made the connection while studying the origin of this unwanted sound.

The study focused on eight patients with gaze-evoked tinnitus (GET), an unusual condition in which tinnitus loudness and pitch increase during lateral gaze. GET may develop after surgical removal of tumors of the auditory nerve. The researchers expect that the findings from their study of this rare condition will open the door to a broader understanding of the brain abnormalities that cause tinnitus.

As researchers mapped the brains of GET patients, they found an unexpected imbalance between the auditory and visual parts of the brain.

Normally, these different brain areas communicate with each other to determine which perception should be given priority. In normal subjects, lateral gaze suppresses auditory brain activity, but not so with GET patients. This failure of one sensory system to suppress the activity of another may be an important feature of tinnitus.

"This is the first research to show that a failure of the complicated way our brain systems talk to each other contributes to the cause of tinnitus. Tinnitus is not the simple problem we hoped for," said Alan H. Lockwood, MD, study co-author. Lockwood, Professor of Neurology, Nuclear Medicine and Communicative Disorders and Sciences at the State University of New York at Buffalo, and the Veterans Administration Western New York Healthcare System, also co-authored the first research which showed tinnitus sensations came from the brain in the central auditory system, and not the cochlea.

"It remains to be seen what other parts of the brain are involved in the cause of tinnitus," added Lockwood. "However, this is an important step in unraveling this complicated story."

Tinnitus is a perception of ringing or buzzing in the ears that affects 50 million people in the US according to the American Tinnitus Association. Tinnitus is more common in men and in people over the age of 65. Severe tinnitus is associated with depression, anxiety, sleep disruption and other symptoms that significantly impact patients' quality of life.

A neurologist is a medical doctor with specialized training in diagnosing, treating and managing disorders of the brain and nervous system.

The American Academy of Neurology, an association of more than 17,000 neurologists and neuroscience professionals, is dedicated to improving patient care through education and research.

GAINESVILLE, Fla. — It is well known that unborn babies can recognize their mothers' voices and distinguish music from noise. But exactly what they hear remains unclear.

Now, scientists at the University of Florida have added a piece to the puzzle. In a series of unique experiments on a pregnant ewe designed to record exactly what sounds reach the fetal ear, UF research has bolstered previous findings suggesting that human fetuses likely hear mostly low-frequency rather than high-frequency sounds. That means they hear vowels rather than consonants and are more sensitive to the melodic parts of speech than to pitch, said Ken Gerhardt, a UF professor of communication sciences and disorders and an associate dean of the Graduate School.

As for music, "they're not going to hear the violins, but they will hear the drums," said Gerhardt, who led the research reported in the November-December issue of the journal Audiology and Neuro Otology.

Anthony DeCasper, a professor of developmental psychology at the University of North Carolina-Greensboro, said the UF results are noteworthy because they were obtained from the inner ear, which presumably would register sounds exactly as a sheep fetus would hear them. The findings – which resulted from implanting a tiny electronic device in the inner ear of a fetal sheep that tapped into the signal the ear sends to the brain – dovetail with what other researchers have concluded based on less invasive studies involving human fetuses, he said.

"The way I put it is, the way the mother's voice would sound in utero would be like Lauren Bacall speaking from behind a heavy curtain," DeCasper said.

The research also may have implications for the care of premature babies. Neonatal care units are traditionally relatively noisy places, replete with beeping machines and the hum of conversation, and research by Gerhardt, DeCasper and others is raising awareness and questions about how the sounds "premies" are exposed to may influence normal growth and development, researchers said.

Gerhardt said he began researching fetal hearing in response to inquiries from law enforcement agencies and the U.S. Navy. Both were concerned about how loud noises, such as gunfire or the rumble of a ship's engine, could affect the hearing of babies being carried by pregnant servicewomen.

Gerhardt and Robert Abrams, a UF professor emeritus of obstetrics and gynecology, decided to study the issue using sheep because experiments by other researchers had shown that properties of sound transmission in pregnant women and sheep are similar. Their experiments revealed the womb dampened all but the loudest sounds. Even loud rock concerts are probably not noisy enough to pose a threat to fetal hearing development, Gerhardt said. The research, which has received more than $1 million from the Navy, the National Institutes of Health and the March of Dimes, contributed to federal workplace safety guidelines that today limit the duration of extremely loud noise exposure for pregnant women.

In their recently reported research, Gerhardt and Abrams focused specifically on the kinds of sounds fetal sheep hear. Their method was unique: They implanted an electronic "pickup" inside the inner ear of a fetal sheep, then played 64 recorded sentences on a loudspeaker in the open air near the mother sheep. The sounds the pickups detected were recorded and played back to 30 human adult listeners in order to determine how much or what portions of the sentences the fetus actually heard. For comparison, the researchers also placed a microphone inside the uterus of the ewe and in the open air, then performed identical tests with human listeners.

The results were surprising, with the intelligibility of sentences "actually much higher than we anticipated," Gerhardt said.

In part, that was unexpected because much of the noise that reaches a fetus comes from its mother's own voice, movement, breathing and digestive processes. Even in a quiet room, the womb can be noisy place, he said. Also, fetuses don't "hear" as much with their ears as children or adults do because their ears are filled with fluid, he said. Rather, much noise is transmitted to their inner ears through vibrations in their skulls. As a result, the mother's voice tends to be the most dominant and recurring sound in the womb.

The listeners understood all of the sentences recorded in the open air, about 70 percent of the sentences recorded in the womb and about 30 percent of the sentences recorded in the fetal sheep's inner ear.

The recordings revealed the reason the inner ear-recorded sentences proved so much less intelligible was that the higher-frequency consonants in words tended to be absent or confused. In other words, "ship" could easily be heard as "slit" or "sit." Lower-frequency vowels, by contrast, tended to penetrate the inner ear to a much greater extent.

Charlene Krueger, a UF assistant professor of nursing who works with premature babies, said that while a fetus hears its mother's voice whenever she speaks and is insulated from higher frequencies, infants born prematurely don't hear their mother's voices all the time because their mothers usually can't be at the bedside 24 hours a day. Also, while unborn children are insulated from many frequencies, premies are exposed to all the frequencies of the sounds in the nursery. She is interested in finding out how this added exposure, combined with the loss of the mother's voice, might influence the premies' development.

Unexplained and severe tinnitus–a ringing or buzzing in the ears–can be temporarily reduced in some patients by "jamming" the brain's electrical activity with focused magnetic stimulation, according to a preliminary study in the Annals of Neurology. The results confirm that some phantom sounds are generated by abnormal activity in the brain itself.

"Controlled clinical trials are now necessary to evaluate whether this method can permanently reduce and thus cure tinnitus," said senior author Christian Gerloff, M.D, of the University of Tuebingen in Germany.

Many people experience tinnitus, defined as the perception of sound in the absence of an obvious source, at some point in their lives. For most of us, it is a temporary and benign oddity with a host of causes, such as ear infection, blockage of the ear canal, or medications such as antibiotics.

For more than forty million Americans, however, tinnitus is an ongoing problem. It is especially prevalent among the elderly and those with some degree of hearing loss. According to the American Tinnitus Association, a patient advocacy group, some twelve million Americans seek medical attention for the disorder, and about one million are affected to the point of disability.

In some cases a mechanical sound source, such as a damaged artery or other blood vessel disorder, can be identified and treated, but for most forms of tinnitus there is little effective treatment.

"Recently, neuroscientists have brought forward a new concept which postulates similarities between tinnitus and chronic pain. According to this concept, sounds that only the patient can detect might be some sort of 'phantom' auditory perception similar to phantom pain," said Gerloff.

By this theory, abnormal brain activity is creating the illusion of sound in the absence of acoustic stimuli.

In order to investigate this possibility, Gerloff and his colleagues used focused magnetic stimulation to temporarily interfere with the activity of specific brain regions in 14 patients with intractable, chronic tinnitus. They focused their attention on auditory association areas, regions of the brain known to specialize in the processing of auditory input.

The researchers found that when they stimulated a region called the left temporoparietal cortex, which contains several auditory association areas, tinnitus was temporarily reduced in most of the patients. There was no statistically significant reduction when other brain areas were stimulated.

The authors note that only 8 of the 14 patients experienced tinnitus relief during more than one of the five stimulations of the left temporoparietal cortex. Indeed, one patient reported a slight temporary worsening of the tinnitus, which suggests that the situation is not as simple as the nerve cells in the temporoparietal cortex being the source of all tinnitus sounds. However, the findings do provide clues for further research.

"Knowing that these brain areas are functionally relevant for tinnitus makes them a primary target for modern therapeutic approaches based on brain stimulation methods," said Gerloff.

BUFFALO, N.Y. — A novel rat behavioral model of tinnitus that will allow researchers to study this debilitating condition in a manner never before possible and to test potential treatments has been developed by researchers with the University at Buffalo's Center for Hearing & Deafness.

Center researchers, who have been studying tinnitus for more than a decade, will use this animal model to monitor the activity of individual neurons in the animals' brains where the phantom sounds of tinnitus are thought to occur in a new study funded by a $167,000 grant from the American Tinnitus Association.

The novel behavior paradigm, which involved training the animals to abstain from drinking when they perceive sound, is described in the April issue of Hearing Research.

"Having this animal model to work with and to observe will allow us to make significant strides in identifying the underlying neural mechanisms of this condition," said Richard Salvi, Ph.D., director of the Center for Hearing & Deafness and primary researcher on the new study. "We hope this research will bring us closer to finding a treatment for tinnitus and to providing relief to the millions who suffer from it.

"The neural mechanisms that give rise to the phantom sound of tinnitus are not well understood because of the limited number of animal models available to work with," continued Salvi, professor in the Department of Communicative Disorders and Sciences in the UB College of Arts and Sciences. "This new model gives us the ability to have an animal make a behavioral response to tell us it hears the phantom sound of tinnitus and to measure what is going on in the brain at the same time. No one has been able to do this before in a 'behaving' animal."

The model was developed by Edward Lobarinas, a doctoral student in the UB Department of Communicative Disorders and Sciences and a member of the center. The rats were trained to drink from their water dispenser during periods of quiet, but to refrain from drinking during actual noise, defined as "licks in sound."

Once this pattern was established, researchers injected each animal with saline or a solution containing increasing concentrations of sodium salicylate, or aspirin, which is known to induce the phantom sounds of tinnitus. Each dose of aspirin — 50, 100, 150 and 350 milligrams per kilogram of body weight (mg/kg) — was given for two days. Doses were separated by a week to allow behavior to return to baseline between treatments. Researchers hypothesized that when trained animals sensed the phantom sound of tinnitus during quiet periods, they would interpret it as "real sound" and would refuse to drink.

Results showed that when animals received saline or the 50 mg/kg aspirin solution, they drank during quiet as they were conditioned to do, indicating no evidence of tinnitus. The 100 mg/kg dose produced a slight suppression of licking during quiet. However, the 150 mg/kg and 350 mg/kg treatments almost completely suppressed licking during the quiet interval, indicating the rats were hearing a phantom sound. The high dose of sodium salicylate produced behaviors in quiet that were similar to a real sound of 40 decibels, Salvi said.

"This cessation of licking during quiet would appear to indicate the animals are sensing a phantom noise, the condition that defines tinnitus, although no noise was present," said Lobarinas. "After the salicylate treatment ended, the rats gradually returned to their normal conditioned behavior in two-to-three days, indicating the disappearance of tinnitus."

With the two-year grant from the American Tinnitus Association, the researchers will monitor and correlate changes in neural activity in the auditory cortex, a region of the brain responsible for processing and interpreting sound, by taking readings from individual neurons before, during and after inducing tinnitus.

"We expect to see that a subpopulation of neurons in the auditory cortex will increase their activity when the rats experience tinnitus and that the activity will decrease when the tinnitus disappears," said Salvi.

Additional researchers on the project to develop an animal behavioral model of tinnitus were Wei Sun, research assistant professor, and Ross Cushing, AuD, both in the UB Department of Communicative Disorders and Sciences.

Their research was supported in part by grants from the National Institute on Deafness and Other Communication Disorders and the Royal National Institute for Deaf People.

The University at Buffalo is a premier research-intensive public university, the largest and most comprehensive campus in the State University of New York.