Archive for ‘HIV’

Study of Timbre May Lead to Better Hearing Aids

Study of Timbre May Lead to Better Hearing Aids

Study of Timbre May Lead to Better Hearing Aids

By advancing our understanding of how the brain is able to recognize musical sounds, engineers at The Johns Hopkins University could help the makers of hearing aids and cochlear implants do a better job filling the sounds of silence.

The new research, published in the November edition of PLOS Computational Biology, offers insight into how the brain processes timbre, a hard-to-quantify concept loosely defined as everything in music that isn’t duration, loudness or pitch. For instance, timbre comes into play when we are able to instantly decide whether a sound is coming from a violin or a piano.

The information may one day change the design of hearing prosthetics, potentially helping people who suffer from hearing loss to continue to tap into their musical intuition in a way current devices on the market cannot, according to Mounya Elhilali, the study’s lead author and an assistant professor in the Department of Electrical and Computer Engineering in the Whiting School of Engineering.

The result could be music to the ears of millions of people with hearing impairment who lament that their favorite songs don’t sound the way they did before their hearing started to fade.

“Our research has direct relevance to the kinds of responses you want to be able to give people with hearing impairments,” Elhilali said. “People with hearing aids or cochlear implants don’t really enjoy music nowadays, and part of it is that a lot of the little details are being thrown away by hearing prosthetics. By focusing on the characteristics of sound that are most informative, the results have implications for how to come up with improved sound processing strategies and design better hearing prosthetics so they don’t discard a lot of relevant information.”

Thoroughly enjoying a Springsteen concert or a night at the symphony has not been a top priority in hearing-prosthetics design. Current devices tend to mitigate hearing loss during everyday conversations at the office or help people who have trouble picking out nearby voices from a sea of sounds in a noisy, crowded room. If designers could incorporate knowledge of the brain’s timbre receptors, it is possible that they could improve the quality of life for people who rely on hearing aids or cochlear implants, Elhilali said.

The ability to recognize musical instruments has other non-medical applications. It can help build computer systems that can annotate musical multimedia data, or transcribe musical performances for purposes of education, study of musical theory or improved coding and compression. With the explosion of information technology, mining multimedia data is of great interest and there is a pressing need for better processing and sharing of information. To this end, there is much to be learned from how the human brain processes complex information such as musical timbre and translating this knowledge into improved computer systems and hearing technologies, Elhilali said.

The researchers set out to examine the neural underpinnings of musical timbre in an attempt to both define what makes a piano sound different than a violin; and explore the processes underlying the brain’s way of recognizing timbre. The basic idea was to develop a mathematical model that would simulate how the brain works when sound comes in, how it looks for specific features and whether something is there that allows the brain to discern these different qualities.

Based on experiments in both animals and humans, they devised a computer model that can accurately mimic how specific brain regions process sounds as they enter our ears and get transformed into brain signals that allow us to recognize the type of sounds we are listening to. The model was able to correctly identify which instrument is playing (out of a total of 13 instruments) to an accuracy rate of 98.7 percent.

The computer model was also able to mirror how human listeners make judgment calls regarding timbre. These judgments were collected from 20 people who were brought separately into a sound booth and listened to musical notes over headphones. The researchers asked these regular listeners to listen to two sounds played by different musical instruments. The listeners were then asked to rate how similar the sounds seemed. A violin and a cello are perceived as closer to each other than a violin and a flute. The researchers also found that wind and percussive instruments tend to overall be the most different from each other, followed by strings and percussions, then strings and winds. These subtle judgments of timbre quality were also reproduced by the computer model.

The co-investigators are graduate student Kailash Patel from Johns Hopkins; Daniel Pressnitzer of Laboratoire Psychologie de la Perception, CNRS-Université Paris Descartes & DEC, Ecole normale supérieure in Paris; and Shihab Shamma, Department of Electrical and Computer Engineering and Institute for Systems Research, University of Maryland, College Park. Shamma was partly supported by a Blaise-Pascal Chair, Region Ile de France, and by the program Research in Paris, Mairie de Paris.

“Music in our ears: The biological bases of musical timbre perception,” was partly supported by grants from the National Science Foundation, the Air Force Office of Scientific Research, the National Institutes of Health, and the Office of Naval Research.

Timbre is the attribute of sound that allows humans and other animals to distinguish among different sound sources. Studies based on psychophysical judgments of musical timbre, ecological analyses of sound’s physical characteristics as well as machine learning approaches have all suggested that timbre is a multifaceted attribute that invokes both spectral and temporal sound features. Here, we explored the neural underpinnings of musical timbre. We used a neuro-computational framework based on spectro-temporal receptive fields, recorded from over a thousand neurons in the mammalian primary auditory cortex as well as from simulated cortical neurons, augmented with a nonlinear classifier. The model was able to perform robust instrument classification irrespective of pitch and playing style, with an accuracy of 98.7%. Using the same front end, the model was also able to reproduce perceptual distance judgments between timbres as perceived by human listeners. The study demonstrates that joint spectro-temporal features, such as those observed in the mammalian primary auditory cortex, are critical to provide the rich-enough representation necessary to account for perceptual judgments of timbre by human listeners, as well as recognition of musical instruments.

Author Summary Top

Music is a complex acoustic experience that we often take for granted. Whether sitting at a symphony hall or enjoying a melody over earphones, we have no difficulty identifying the instruments playing, following various beats, or simply distinguishing a flute from an oboe. Our brains rely on a number of sound attributes to analyze the music in our ears. These attributes can be straightforward like loudness or quite complex like the identity of the instrument. A major contributor to our ability to recognize instruments is what is formally called ‘timbre’. Of all perceptual attributes of music, timbre remains the most mysterious and least amenable to a simple mathematical abstraction. In this work, we examine the neural underpinnings of musical timbre in an attempt to both define its perceptual space and explore the processes underlying timbre-based recognition. We propose a scheme based on responses observed at the level of mammalian primary auditory cortex and show that it can accurately predict sound source recognition and perceptual timbre judgments by human listeners. The analyses presented here strongly suggest that rich representations such as those observed in auditory cortex are critical in mediating timbre percepts.

Timbre, a poorly defined characteristic of sound, is a great source of information for people with normal hearing. It allows people to identify the source of a particular sound and makes music enjoyable. Modern hearing aids are still rudimentary devices in terms of providing a rich sound to their users. There’s a lot of potential for improving how elements of timbre are translated to the hearing impaired to improve location and source perception.

An international team of researchers has been studying the way we process sound and they built a software algorithm that can make similar judgements about sound that people with healthy hearing can. This technology should allow hearing aid manufacturers to improve audio processors in their devices, immensely improving their utility and bringing back the pleasures of music to the users.

“Our research has direct relevance to the kinds of responses you want to be able to give people with hearing impairments,” Elhilali said. “People with hearing aids or cochlear implants don’t really enjoy music nowadays, and part of it is that a lot of the little details are being thrown away by hearing prosthetics. By focusing on the characteristics of sound that are most informative, the results have implications for how to come up with improved sound processing strategies and design better hearing prosthetics so they don’t discard a lot of relevant information.”

The researchers set out to examine the neural underpinnings of musical timbre in an attempt to both define what makes a piano sound different than a violin; and explore the processes underlying the brain’s way of recognizing timbre. The basic idea was to develop a mathematical model that would simulate how the brain works when sound comes in, how it looks for specific features and whether something is there that allows the brain to discern these different qualities.

Based on experiments in both animals and humans, they devised a computer model that can accurately mimic how specific brain regions process sounds as they enter our ears and get transformed into brain signals that allow us to recognize the type of sounds we are listening to. The model was able to correctly identify which instrument is playing (out of a total of 13 instruments) to an accuracy rate of 98.7 percent.

The computer model was also able to mirror how human listeners make judgment calls regarding timbre. These judgments were collected from 20 people who were brought separately into a sound booth and listened to musical notes over headphones. The researchers asked these regular listeners to listen to two sounds played by different musical instruments. The listeners were then asked to rate how similar the sounds seemed. A violin and a cello are perceived as closer to each other than a violin and a flute. The researchers also found that wind and percussive instruments tend to overall be the most different from each other, followed by strings and percussions, then strings and winds. These subtle judgments of timbre quality were also reproduced by the computer model.

Source : http://releases.jhu.edu/2012/11/02/new-insights-about-timbre/

Full story

Internet, smartphone apps represent prime venues for adolescent-targeted sexual health programs

Internet, smartphone apps represent prime venues for adolescent-targeted sexual health programs

The use of smartphones is associated with an increased likelihood of being solicited for sex on the internet, and having sex with an internet-met partner among teens, according to new research released today at the American Public Health Association’s 140th Annual Meeting in San Francisco, Calif.

According to the research, young people with smartphones are 1.5 times as likely to report being sexually active, almost two times as likely to have been approached online for sex, and more than twice as likely to engage in sex with an Internet-met partner compared with those who do not access the internet on their cell phones. Additionally, those being solicited online for sex are also found to be engaging in unprotected sex. Five percent of the participants reported using the Internet to seek sex partners and 17 percent of the participants reported being approached online for sex by someone they did not know.

Researchers from the University of Southern California also found that compared with their heterosexual peers, non-heterosexual high school students were five times more likely to seek sex partners online. Overall, one-third of all participants use their cell phones to access the Internet (i.e., have smartphones). Results are from a 2011 survey distributed to high school students (n= 1,839) from the Los Angeles Unified School District and were controlled for independent factors, including age, race, gender and sexual orientation.

“We—parents, health educators, physicians—must recognize that cell phones are yet another new way for adolescents to meet sex partners,” said Hailey Winetrobe, MPH, CHES, researcher at USC and an APHA Annual Meeting presenter. “Parents and school health professionals should talk to their teens about being safe in meeting people online and in using condoms to prevent sexually transmitted infections and unplanned pregnancies.”

The authors note that the Internet and smartphone apps represent prime venues for adolescent-targeted sexual health programs.

Source : http://www.news-medical.net/news/20121030/Internet-smartphone-apps-represent-prime-venues-for-adolescent-targeted-sexual-health-programs.aspx

Full story

Study finds increase in HIV treatment use in the U.S.

Study finds increase in HIV treatment use in the U.S.

Between 2000 and 2008, the proportion of HIV-infected patients in the U.S. receiving effective treatment known as highly active antiretroviral therapy (HAART) increased, and HIV-infected patients appeared to be less infectious and have healthier immune systems at death, according to a study led by researchers at the Johns Hopkins Bloomberg School of Public Health. The study was nested in the NA-ACCORD (North American AIDS Cohort Collaboration on Research and Design), which is the largest cohort of HIV-infected adults in North America. The findings are published in the September 4 edition of Annals of Internal Medicine.

The study included more than 45,000 HIV-infected participants receiving clinical care for HIV. The study population was demographically similar to the U.S. population living with HIV, according to national surveillance data from the Centers for Disease Control and Prevention. Over the study period, the researchers found that the proportion of HIV-infected participants prescribed HAART increased 9 percentage points to 83 percent. During this time, the researchers also observed an increase in viral load suppression among those with HIV, regardless of treatment. Suppression of viral load reduces the likelihood of transmitting HIV to others. Among those taking HAART, the proportion with a suppressed viral load increased from 54 percent to 81 percent.

“This is good news for the HIV epidemic in the U.S., but there is room for improvement,” said Keri N. Althoff, PhD, MPH, lead author of the study and assistant professor in the Bloomberg School’s Department of Epidemiology. “We need to continue to focus on linking HIV-infected adults into care and effective treatment, not only for the individual’s health, but to reduce the likelihood of transmission to others.”

The analysis also found an increase in median CD4 count for participants who died from HIV during the study period. Median counts increased at the time of death from 60 cells/mm3 to 209 cells/mm3. A higher CD4 count suggests a healthier immune system. Additional research is planned to investigate trends in the causes of death.

“Our study demonstrates the data from the NA-ACCORD can be used to monitor important health indicators among adults with HIV, which is needed to evaluate the impact of the Affordable Care Act and to measure progress towards the National HIV Strategy goals,” said Althoff.

Source : http://www.news-medical.net/news/20120904/Study-finds-increase-in-HIV-treatment-use-in-the-US.aspx

Full story

Article describes novel technique to study interactions between HIV-1 and P. falciparum

Article describes novel technique to study interactions between HIV-1 and P. falciparum

The World Health Organization estimates that in 2011 there were 216 million cases of malaria and 34.2 million people living with HIV. These diseases particularly afflict sub-Saharan Africa, where large incidence of co-infection result in high mortality rates. Yet, in spite of this global pandemic, interactions between the parasite that causes malaria, Plasmodium falciparum, and HIV-1 are poorly understood. However, a new video article in JoVE, the Journal of Visualized Experiments, that describes a novel technique to study the interactions between HIV-1 and P. falciparum in cultured human cells, will allow scientists to explore different parameters of co-infection by the two microbes.

The study is led by Dr. David Richard of the Centre Hospitalier Universitaire de Quebec (CHUQ). Dr. Richard explains, “We don’t know much about what is happening at the cellular level when HIV-1-infected immune cells encounter the malaria parasite. Results obtained from the few studies exploring the interaction of these two diseases are sometimes conflicting. We hope that our model will allow us to thoroughly dissect these interactions in a simplified system.”

Each disease attacks a different component of human blood, thus disturbing normal immune function. P. falciparum infect red blood cells and cause fever, shivering, vomiting, or convulsions in patients. HIV-1 causes acquired immune deficiency syndrome (AIDS) by infecting components of the immune system, including macrophages and helper T cells, and then replicates and destroys the host cells. By studying co-infection at different phases of each disease in vitro, scientists can better understand how different stages of malaria infection and HIV reproduction affect the onset and severity of the other disease. As such, Dr. Richard and his laboratory present a technique that investigates how P. falciparum-infected red blood cells affect the replication of HIV-1 in monocyte-derived macrophages.

Dr. Richard points out that, “by publishing in JoVE, you really see what is happening in the experiment. The visual representation helps succinctly explain a long procedure, and gives you a fuller picture of the schematic complexity.” He hopes that this publication will give the scientific community the tools to look at the interactions on a cellular level, which would be an initial step in improving the quality of life for individuals infected by these deadly diseases. “This protocol provides a tool to examine the interactions between P. falciparium and HIV,” states JoVE editor Dr. Charlotte Frank Sage, “Publication of the protocol in JoVE will allow researchers around the world to see a detailed demonstration of this system which will help in bring the technology to their laboratories.”

Source : http://www.news-medical.net/news/20120816/Article-describes-novel-technique-to-study-interactions-between-HIV-1-and-P-falciparum.aspx

Full story

Computer Simulation Aims to Predict Public Policy Effects on HIV/AIDS

Computer Simulation Aims to Predict Public Policy Effects on HIV/AIDS

Computer Simulation Aims to Predict Public Policy Effects on HIV/AIDS

Policymakers in the fight against HIV/AIDS may have to wait years, even decades, to know whether strategic choices among possible interventions are effective. How can they make informed choices in an age of limited funding? A reliable, well-calibrated, predictive computer simulation would be a great help.

PROVIDENCE, R.I. [Brown University] — Policymakers struggling to stop the spread of HIV grapple with “what if” questions on the scale of millions of people and decades of time. They need a way to predict the impact of many potential interventions, alone or in combination. In two papers to be presented at the 2012 International AIDS Society Conference in Washington, D.C., Brandon Marshall, assistant professor of epidemiology at Brown University, will unveil a computer program calibrated to model accurately the spread of HIV in New York City over a decade and to make specific predictions about the future of the epidemic under various intervention scenarios.

“It reflects what’s seen in the real world,” said Marshall. “What we’re trying to do is identify the ideal combination of interventions to reduce HIV most dramatically in injection drug users.”

In an analysis that he’ll present at 11 a.m. in Session Room 6 on Friday, July 27, Marshall projects that with no change in New York City’s current programs, the infection rate among injection drug users will be 2.1 per 1,000 in 2040. Expanding HIV testing would drop the rate only 12 percent to 1.9 per 1,000; increasing drug treatment would reduce the rate 26 percent to 1.6 per 1,000; providing earlier delivery of antiretroviral therapy and better adherence would drop the rate 45 percent to 1.2 per 1,000; and expanding needle exchange programs would reduce the rate 34 percent to 1.4 per 1,000. Most importantly, doing all four of those things would cut the rate by more than 60 percent, to 0.8 per 1,000.

Brandon Marshall“(The computer model) reflects what’s seen in the real world. What we’re trying to do is identify the ideal combination of interventions to reduce HIV most dramatically in injection drug users.”Brandon Marshall

“(The computer model) reflects what’s seen in the real world. What we’re trying to do is identify the ideal combination of interventions to reduce HIV most dramatically in injection drug users.”“These results show that a comprehensive set of proven interventions must be scaled up immediately if we are to substantially reduce the spread of HIV among drug users,” Marshall said.

Virtual reality, real choices

The model is unique in that it creates a virtual reality of 150,000 “agents,” a programming term for simulated individuals, who in the case of the model, engage in drug use and sexual activity like real people.

Like characters in an all-too-serious video game, the agents behave in a world governed by biological rules, such as how often the virus can be transmitted through encounters such as unprotected gay sex or needle sharing.

With each run of the model, agents accumulate a detailed life history. For example, in one run, agent 89,425, who is male and has sex with men, could end up injecting drugs. He participates in needle exchanges, but according to the built-in probabilities, in year three he shares needles multiple times with another injection drug user with whom he is also having unprotected sex. In the last of those encounters, agent 89,425 becomes infected with HIV. In year four he starts participating in drug treatment and in year five he gets tested for HIV, starts antiretroviral treatment, and reduces the frequency with which he has unprotected sex. Because he always takes his HIV medications, he never transmits the virus further.

That level of individual detail allows for a detailed examination of transmission networks and how interventions affect them.

“With this model you can really look at the microconnections between people,” said Marshall, who began working on the model as a postdoctoral fellow at Columbia University and has continued to develop it since coming to Brown in January. “That’s something that we’re really excited about.”

To calibrate the model, Marshall and his colleagues found the best New York City data they could about how many people use drugs, what percentage of people were gay or lesbian, the probabilities of engaging in unprotected sex and needle sharing, viral transmission, access to treatment, treatment effectiveness, participation in drug treatment, progression from HIV infection to AIDS, and many more behavioral, social and medical factors. They also continuously calibrated it until the model could faithfully reproduce the infection rates among injection drug users that were known to occur in New York between 1992 and 2002.

And they don’t just run the simulation once. They run it thousands of times on a supercomputer at Brown to be sure the results they see are reliable.

Future applications

At Brown, Marshall is continuing to work on other aspects of the model, including an analysis of the cost effectiveness of each intervention and their combinations. Cost is, after all, another fact of life that policymakers and public health officials must weigh.

And then there’s the frustrating insight that the infection rate, even with four strengthened interventions underway, didn’t reduce the projected epidemic by much more than half.

“I actually expected something larger,” Marshall said. “That speaks to how hard we have to work to make sure that drug users can access and benefit from proven interventions to reduce the spread of HIV.”

Marshall’s collaborators on the model include Magdalena Paczkowski, Lars Seemann, Barbara Tempalski, Enrique Pouget, Sandro Galea, and Samuel Friedman.

The National Institutes of Health and the Lifespan/Tufts/Brown Center for AIDS Research provide financial support for the model’s continued development.

The spread of infectious diseases can be mitigated by properly targeted public policies that actually change people’s behaviors. HIV infections and their distribution are particularly susceptible to how they are addressed by public health officials, but it usually takes years to measure the actual results of the policies taken.

In order to help predict which set of policies is most effective, Brandon Marshall, assistant professor of epidemiology at Brown University, developed a computer simulation that involves thousands of virtual humans with unique behavioral patterns. At last week’s International AIDS Society Conference in Washington, D.C., Marshall presented findings from thousands of completed simulations of how New York City’s HIV/AIDS population becomes infected. By using historical data gathered in years past, Marshall was able to tune and calibrate the algorithms to correctly predict the past, and so hopefully the future.

Marshall projects that with no change in New York City’s current programs, the infection rate among injection drug users will be 2.1 per 1,000 in 2040. Expanding HIV testing would drop the rate only 12 percent to 1.9 per 1,000; increasing drug treatment would reduce the rate 26 percent to 1.6 per 1,000; providing earlier delivery of antiretroviral therapy and better adherence would drop the rate 45 percent to 1.2 per 1,000; and expanding needle exchange programs would reduce the rate 34 percent to 1.4 per 1,000. Most importantly, doing all four of those things would cut the rate by more than 60 percent, to 0.8 per 1,000.

The model is unique in that it creates a virtual reality of 150,000 “agents,” a programming term for simulated individuals, who in the case of the model, engage in drug use and sexual activity like real people.

Like characters in an all-too-serious video game, the agents behave in a world governed by biological rules, such as how often the virus can be transmitted through encounters such as unprotected gay sex or needle sharing.

With each run of the model, agents accumulate a detailed life history. For example, in one run, agent 89,425, who is male and has sex with men, could end up injecting drugs. He participates in needle exchanges, but according to the built-in probabilities, in year three he shares needles multiple times with another injection drug user with whom he is also having unprotected sex. In the last of those encounters, agent 89,425 becomes infected with HIV. In year four he starts participating in drug treatment and in year five he gets tested for HIV, starts antiretroviral treatment, and reduces the frequency with which he has unprotected sex. Because he always takes his HIV medications, he never transmits the virus further.

To calibrate the model, Marshall and his colleagues found the best New York City data they could about how many people use drugs, what percentage of people were gay or lesbian, the probabilities of engaging in unprotected sex and needle sharing, viral transmission, access to treatment, treatment effectiveness, participation in drug treatment, progression from HIV infection to AIDS, and many more behavioral, social and medical factors. They also continuously calibrated it until the model could faithfully reproduce the infection rates among injection drug users that were known to occur in New York between 1992 and 2002.

Source : http://news.brown.edu/pressreleases/2012/07/hiv

Related Posts Plugin for WordPress, Blogger...

Full story

Copyright © 2017 Medical Technology & Gadgets Blog MedicalBuy.net. All rights reserved.
Proudly powered by WordPress. Developed by Deluxe Themes