New York- Scientists have given physiological evidence that a pervasive neuromodulation system - a group of neurons that regulate the functioning of more specialized neurons - strongly influences sound processing in an important auditory region of the brain.
The neuromodulator -- acetylcholine -- may even help the main auditory brain circuitry distinguish speech from noise.
"While the phenomenon of these modulators' influence has been studied at the level of the neocortex, where the brain's most complex computations occur, it has rarely been studied at the more fundamental levels of the brain," said study author R Michael Burger from the Lehigh University in the US.
The study, published in the JNeurosci: The Journal of Neuroscience, will likely bring new attention in the field to the ways in which circuits like this, widely considered a 'simple' one, are in fact highly complex and subject to modulatory influence like higher regions of the brain.
The team conducted electrophysiological experiments and data analysis to demonstrate that the input of the neurotransmitter acetylcholine, a pervasive neuromodulator in the brain, influences the encoding of acoustic information by the medial nucleus of the trapezoid body (MNTB), the most prominent source of inhibition to several key nuclei in the lower auditory system.
MNTB neurons have previously been considered computationally simple, driven by a single large excitatory synapse and influenced by local inhibitory inputs.
The team demonstrated that in addition to these inputs, acetylcholine modulation enhances neural discrimination of tones from noise stimuli, which may contribute to processing important acoustic signals such as speech.
Additionally, they describe novel anatomical projections that provide acetylcholine input to the MNTB.
Burger studies the circuit of neurons that are "wired together" in order to carry out the specialized function of computing the locations from which sounds emanate in space.
He described neuromodulators as broader, less specific circuits that overlay the more highly-specialized ones.
"This modulation appears to help these neurons detect faint signals in noise. You can think of this modulation as akin to shifting an antenna's position to eliminate static for your favourite radio station," Burger said.
"In this paper, we show that modulatory circuits have a profound effect on neurons in the sound localization circuitry, at the very low foundational level of the auditory system," the authors wrote. (IANS)
London - Researchers have revealed that tinnitus, a common condition that causes the perception of noise in the ear and head, is being exacerbated by Covid-19 -- as well as the measures taken to stop its spread.
The study, published in the journal Frontiers in Public Health, involved 3,103 participants from 48 countries, with the vast majority coming from the UK and the US.
"We found that 40 per cent of those displaying symptoms of Covid-19 simultaneously experience a worsening of their tinnitus," said study authors from Anglia Ruskin University (ARU) in the UK.
Although the study focused on people with pre-existing tinnitus, a small number of participants also reported that their condition was initially triggered by developing Covid-19 symptoms, suggesting that tinnitus could be a 'long Covid' symptom in some cases.
The study also found that a large proportion of people believe their tinnitus is being made worse by social distancing measures introduced to help control the spread of the virus.
These measures have led to significant changes to work and lifestyle routines.
UK respondents reported this to be a greater issue compared to people from other countries, with 46 per cent of UK respondents saying that lifestyle changes had negatively impacted their tinnitus compared to 29 per cent in North America.
Females and the under-50s found tinnitus significantly more bothersome during the pandemic.
The study noted that as well as increasing the severity of tinnitus symptoms, the Covid-19 pandemic has also made it more difficult for people to access healthcare support for the condition.
This could further increase emotional distress and worsen tinnitus symptoms, creating a vicious cycle.
The findings highlight the complexities associated with experiencing tinnitus and how both internal factors, such as increased anxiety and feelings of loneliness, and external factors, such as changes to daily routines, can have a significant effect on the condition.
"Some of the changes brought about by Covid-19 appear to have had a negative impact on the lives of people with tinnitus and participants in this study reported that Covid-19 symptoms are worsening or, in some cases, even initiating tinnitus and hearing loss," the researchers wrote.
"This is something that needs to be closely examined by both clinical and support services," they noted. (IANS)
London - Whether it is loud machinery at work, a busy freeway, a nearby airport or loud music, many people are exposed to high levels of noise, say researchers, adding that exposure to loud noise is not only annoying but also bad for your health.
Large studies have linked noise exposure to various health problems in people.
Now, two new mouse studies provide new insight into how this type of noise exposure can lead to high blood pressure and cancer-related DNA damage.
"Our new data provide additional mechanistic insights into these adverse health effects, especially high blood pressure and potentially cancer development, both leading causes of global death," said study researcher Matthias Oelze from the University Medical Centre of Mainz in Germany.
Published in The FASEB Journal, the research found that healthy mice exposed to four days of aircraft noise were more likely to develop high blood pressure.
For mice with pre-established high blood pressure, this noise exposure aggravated heart damage because of a synergistic increase of oxidative stress and inflammation in the cardiovascular and neuronal systems.
In another study, the researchers observed that the same noise exposure induced oxidative DNA damage in mice. This damage led to a highly mutagenic DNA lesion that was previously associated with the development of cancer in other settings.
They are currently conducting several studies on the health effects of noise, including interactions of pre-established cardiovascular diseases with noise as well as behavioural effects of noise exposure in mice.
"These new findings, together with our other work on noise-associated cardiovascular effects, could lead to a better understanding of how noise influences health," said Oelze.
"This information could help inform policies and regulations that better protect people against diseases related to noise exposure," Oelze noted.(Agency)