Milliseconds time windows can be the key to how we hear, study discoveries

What happens when you listen to the speech at a different speed? Neuroscientists thought your brain could also increase its treatment speed. But it turns out that at least the hearing part of the brain continues to “listen” or block at a fixed moment. This is the key conclusion of new research appearing in Nature neuroscience.

The Research Was Led by Sam Norman-Haignere, Ph.D., Assistant Professor of Biostatistes and Computational Biology, Biomedical Engineering, and Neuroscience at the Del Monte Institute for Neuroscience at the University of Rochester, in Collacration With Researchers at Columbia University, Including Main Investigator Nima Mesgarani, Ph.D., of the Zuckerman Institute, and Menoua Keshishian, Who Completed His Ph.D. in electrical engineering in his laboratory.

“It was surprising. It turns out that when you slow down a word, the auditory cortex does not change the temporal window it deals with. It is as if the auditory cortex is integrating on this fixed time scale,” said Norman-Haignere, the first author of the study, who started study as a postdoctoral researcher in Columbia.

“One of the key objectives of this type of research is to create better models for calculating how the brain processes information in speech, which will increase our set of scientific tools and will ultimately help us understand what is wrong when someone has trouble understanding the treatment of speech and language.”

The complexities of speech understanding and modeling

The auditory cortex, which consists of several layers and regions, is the brain area responsible for the processing and interpretation of sounds. Researchers know that there are several regions in the brain that treat speech – the main auditory cortex, the secondary auditory cortex and linguistic areas beyond the auditory cortex. A fundamental understanding of the functioning of each region and the hierarchy between and in these different regions is not well understood.

Understanding the complexities of the brain has been helped by the development of calculation models. These IT models use mathematical formulas or algorithms to understand and predict neural responses and human behavior.

The authors of this study used computer models to test if their research method would distinguish their two hypotheses: does the auditory cortex integrate information on vocal structures – for example, words – or time? It turned out that certain IT models have learned to integrate through vocal structures, unlike the auditory cortex. This observation was in part in part because it helped to validate the methods that the authors used to study the structure and time.

Access the human brain

Neuroscientists are generally limited in the types of neural data that they can record from the human brain. The electroencephalograms or EEGs offer researchers the electrical activity of the read brain of the scalp, which is far from the real cells that produce this activity. Functional MRIs measure blood flow in the brain, which is an indirect brain activity. The two tools have transformed our understanding of the function and disease of the human brain. However, no method is capable of recording the precise spatial and temporal neuronal activity.

Researchers have worked with patients with epilepsy of Nyu Langone Medical Center, Columbia University Irving Medical Center and the University of Rochester Medical Center to measure a precise neuronal activity of the interior of the human brain. They worked with patients admitted to hospital for epilepsy monitoring.

As part of their surveillance, the electrodes have been temporarily implanted inside their brain so that doctors can better determine the area of ​​the brain where their crises come. These electrodes measure the electrical responses right next to where the neurons are active, offering much higher precision than standard methods such as EEG and IRMF.

The recruited participants were responsible for listening to a passage from an audio book at normal speed, then they were played at the same time at a slower speed. The researchers thought they might see a change in the neuronal time window that varied with the speed of speech. However, the differences they observed were not at least, indicating that the fundamental treatment unit is physical time – for example, 100 milliseconds – and not vocal structures such as words.

“This observation calls into question the intuitive idea that the treatment of our brain should be attached to the structures of the speech we hear, like the syllables or the words,” said Mesgarani, the main study of the study and an associate professor of electrical engineering in Columbia. “Instead, we have shown that the hearing cortex works on a fixed and internal time scale, independent of the sound structure. This provides a systematically timed flow of information that the higher brain regions must then interpret to derive linguistic sense.”

“The better we understand the treatment of speech, the better we think we will be able to understand what causes deficits in speaking,” said Norman-Haignere. “One thing that is exciting in this work line is that there are many people who have studied hearing, and many people who have studied language, but your brain needs to transform sounds that reach your ear in words, sentences and sentences.

“So understanding how the brain goes from something more based on something more based on language and how to model this transformation, is an exciting space in which we work.”

The other researchers include Guy McKhann and Catherine Schevon of Columbia University, and Orrin Devinsku, Werner Doyle and Adeen Flinker, Nyu Langone Medical Center.