Brain News – Researchers at the Massachusetts Institute of Technology (MIT) have explored how certain brain neurons respond to singing. The study is published in the journal Current Biology.
The neuroscientists followed up on a 2015 study that used functional magnetic resonance imaging (fMRI) and identified the neurons in the human brain that respond to speech and music, respectively.
In the new study, the researchers used a technique called electrocorticography (ECoG) which records electrical activity in the brain through the electrodes placed inside the skull. They played a collection of 165 sounds (of different types of speech, music, and everyday sounds such as finger tapping or a dog barking) to 15 epileptic patients over many years and collected their intracranial recordings. Then, they used a novel statistical analysis to infer the types of neural populations in the brain that produced the data recorded in each electrode.
The researchers further devised a mathematical method to combine the high-resolution data from the intracranial recordings with the larger set of fMRI data from the preceding study to get better localization of the neuronal responses.
The findings successfully pinpointed the neurons in the human brain that respond to singing. It showed how certain neurons found in the auditory cortex, at the top of the temporal lobe, respond to a certain combination of voice and music. These song-specific populations of neurons also had extremely weak responses to regular speech or instrumental music.
In the words of one of the lead researchers, Sam Norman-Haignere, “[This] work provides evidence for relatively fine-grained segregation of function within the auditory cortex, in a way that aligns with an intuitive distinction within music.”
The song-specific populations of neurons identified in the recent study are very different from the music- and speech-selective neuronal populations identified in the 2015 study. This has led researchers to recognize this newly discovered neuronal hotspot as that brain region that responds to subtle features of speech—like pitch or word-pitch interaction in a voice—before sending information to other parts of the brain for processing.
The researchers look to further understand how singing affects brain development and drives neuronal responses in the different brain areas.
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Norman-Haignere, S. V., Feather, J., Boebinger, D., Brunner, P., Ritaccio, A., McDermott, J. H., Schalk, G., & Kanwisher, N. (2022). A neural population selective for song in human auditory cortex. Current Biology. https://doi.org/10.1016/j.cub.2022.01.069