Brain networks enable human conversation: study


The researchers found that the brain circuitry is active while we plan our oral responses during a conversation. The research was published in the “Nature Journal”.

The study focused on the brain calculations that enable such responses, which are planned before the end of the speaker’s turn and spoken in a fraction of a second. Led by researchers from NYU Grossman School of Medicine and the University of Iowa, the study found that distinct brain areas are active when planning speech for split-second verbal exchanges , including regions previously unrelated to this feature.

“Our study identifies the brain networks behind the planning that makes this back-and-forth possible, which have been elusive until now,” said lead author Michael Long, PhD, Thomas and Suzanne Murphy Professor of Neuroscience and physiology at NYU Grossman School of Medicine. He added that “the work promises to guide the design of new therapies for the 7.5 million Americans who have difficulty using their voice, including those who suffer from apraxia, difficulty planning the movements of the speech and aphasia, difficulties in processing language, which can accompany conditions like autism or result from trauma caused by a stroke.

For years, researchers have attempted to link speech functions to brain circuitry using electroencephalograms or EEGs, which place electrodes on the scalp. Such devices measure the rapid fluctuations in electrical signals seen as large groups of nerve cells “fire up” to transmit electrical signals. But EEG couldn’t pinpoint the location of nerve circuits with sufficient resolution, and functional magnetic resonance — another commonly used technology — wasn’t fast enough to capture activity patterns related to planning. conversational responses, the study authors said.

These noninvasive methods leave a critical blind spot in the field’s ability to track what the brain is doing during everyday conversation, the authors say. Another technology, electrocorticography (ECoG), overcomes these barriers by placing electrodes not on the scalp, but directly on the surface of the brain. Rapid and accurate ECoG measurements revealed that the brain achieves natural conversation by combining perception of what is heard, planning a response, and producing the sounds (articulation) that make up words. While other ECoG studies have determined the networks related to perception and production, the current study is the first to capture brain activity during the response planning phase between them, which has been the most difficult. to study, the authors said.

“Researchers can talk to patients and observe brain circuit activity while they talk or listen, but planning has no physical correlate,” Long said. “When we combined the ECoG measures with a technique that asks patients structured questions, we exposed an underlying planning network,” Long added.

To conduct the study, the research team placed electrodes on patients’ brain surfaces during ongoing surgeries to remove a tumor or brain tissue causing seizures. In either case, surgeons initially place patients under local anesthesia only so they can determine which brain regions are active when patients speak, thereby avoiding damage to the patient’s speech centers. The researchers placed ECoG electrode arrays on the language-dominant left cerebral hemispheres of eight patient volunteers. Next, they measured planning responses using a paradigm developed by another lab called the Critical Information (CI) task, which was designed to control planning timing. Within each block of questions, a changing keyword, the CI, determines when response planning begins so that brain activity can be tracked within that time window.

1. What common word is the opposite of sweet? 2. The opposite of hot is which common word? By altering the wording of each question to sooner or later present the key information needed to begin planning a response, the researchers were able to distinguish brain activity related to perceptual and production planning. Importantly, the majority of cortical responses were related to only one of these three speech processes, showing that the networks were widely separated for each function.

Additionally, the researchers found that 95.5% of planning electrodes were clustered in a spatially distinct region of the brain, with most planning electrodes centered in the caudal inferior frontal gyrus (cIFG) and caudal middle frontal gyrus ( cMFG). Although cIFG, commonly referred to as “Broca’s region”, has long been known to be important for language, a role for cMFG had not previously been established. Additionally, the team found that the planning network identified with the CI task is also active when patients prepare to speak in natural, unscripted conversations.

After the patients finished answering the structured questions, the researchers engaged them in several minutes of informal conversation, during which the same patterns related to perception, planning, and speaking emerged in brain activity. of the patient. “This study provides a first description of the specific brain mechanisms that generate language when we speak in natural, everyday contexts,” said Gregg Castellucci, PhD, postdoctoral fellow in Long’s lab.

“Essentially, brain mapping that we found using simple, controlled tasks retained in tests of natural human behavior,” he added. Along with Long and Castellucci, the study authors were Christopher Kovach, Matthew Howard III and Jeremy Greenlee, from the Department of Neurosurgery at the University of Iowa. Funding was provided by National Institute of Health grants R01 NS113071 and R01 DC015260, and the Simons Collaboration on the Global Brain. (ANI)

(This story has not been edited by the Devdiscourse team and is auto-generated from a syndicated feed.)


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