The brain distinguishes noise from speech: a unique neural circuit was discovered

The human brain is able to separate noise from speech

How does the human brain distinguishes noise from speech? Investigating this feature, the scientists discovered a new neural circuit and were able to provide the first evidence that the center of the brain is capable of processing any sound and identifying it. And this process involves a unique and mysterious neural connection. The neuromodulator acetylcholine helped to distinguish speech from noise.

Michael Burger, professor of neuroscience, believes that the effects of these modulators were studied at the neocortex level. It was involved in the brain's complex computing processes, but was hardly studied at the fundamental levels of the brain.

Together with colleagues at Northeastern Ohio University, he conducted the research that could raise awareness of how schemas thought to be simple are actually highly complex and subject to changing influences.

The scientists conducted a series of experiments and data analysis, finding that the input of a neurotransmitter affects the coding of acoustic data by the medial nucleus of the trapezius body. It is the most prominent source of inhibition of several key nuclei in the auditory system.

These neurons were considered simple, controlled by a single excitatory synapse, influenced by local inhibitory inputs. The scientists determined that acetylcholine modulation is in addition to the input signals. It improves neural discrimination of tones from noise stimuli.

And this, in turn, facilitates the processing of important acoustic signals such as speech. The researchers continue to study a chain of neurons that are practically wired together to perform a special function of calculating locations that become the source of various signals and sounds in space.

Apparently, the modulations help neurons to detect weak signals in noise. Thus, for the first time, the scientists were able to determine time a set of new, previously completely unknown, neural connections located between the modulation centers and an important area of the auditory system.

Reference: “Endogenous Cholinergic Signaling Modulates Sound-evoked Responses of Medial Nucleus of Trapezoid Body” by Chao Zhang, Nichole L. Beebe, Brett R. Schofield, Michael Pecka and R. Michael Burger, 2 December 2020, JNeurosci: The Journal of Neuroscience. DOI: 10.1523/JNEUROSCI.1633-20.2020