To a human, hearing the perceptual feature of sound known as pitch is vital. This pitch allows individuals to enjoy music and recognize the inflection of speech. According to prior investigations, there is a particular region in the brain that may be accountable for perceiving pitch. Although, whether this “pitch center” really exists is currently being debated by auditory neuroscientists.
In a review report published in the Journal of Neurophysiology, Dr Daniel Bendor, of the Massachusetts Institute of Technology, writes about a recent investigation that claimed this pitch center might not exist after all, or that it might not be located where thought it was.
Dr. Bendor outlines previous cases of scientists who claimed to have discovered a pitch processing center in an area of human auditory cortex located in lateral Heschl’s gyrus. Dr. Bendor also outlines additional more recent studies that revealed data contradicting these earlier discoveries.
The study highlights decades-old investigations, indicating that the auditory cortex plays a crucial role in perceiving pitch. This finding was originally discovered by researchers training cats to distinguish pitch. The researchers then removed the auditory cortex on both sides of the brain – rendering the cats unable to distinguish pitch, even though the animals could still discriminate other aspects of sound, such as frequency.
According to experiments using functional Magnetic Resonance Imaging (fMRI), a method that analyzes brain activity while patients are actively performing tasks in an MRI scanner, the lateral Heschl’s gyrus is the principle player in pitch perception. Numerous fMRI investigations have scanned individuals’ brains whilst participants listen to noise, after which they compared the brain activity to when subjects listened to a sound called iterated ripple noise (IRN), comparable to noise, but with a pitch component. Yet, recent ones comparing IRN and an IRN stimulus modified to have no pitch discovered that both sounds appear to stimulate the same area of the brain, indicating that this region might not contribute to pitch perception after all.
Bendor highlights that it is too early to dismiss the existence of a pitch center, although further examinations are required in order to verify its existence. According to Bendor, even though auditory cortex overlaps Heschl’s gyrus, between subjects the exact placement can vary. Intersubject variability presents a considerable problem when averaging data across multiple subjects, and could be one reason why an fMRI study fails to replicate a result.
Bendor states that other studies indicate that a different region in the brain behind the lateral Heschl’s gyrus (the anterior planum temporale), might contribute in pitch perception – a subject that requires additional research.
The existence of a pitch center, particularly one located in the lateral Heschl’s gyrus, remains an open question.
Dr. Bendor, explains:
“Although there is general agreement that the auditory cortex is essential for pitch perception, whether pitch processing is localized within a single functionally-specific region within the auditory cortex remains a controversial issue among auditory neuroscientists.”
Dr. Bendor is affiliated with the Picower Institute for Learning and Memory, Department of Brain and Cognitive Science at the Massachusetts Institute of Technology.
Written by Grace Rattue