Unexpected sound omissions are signaled in human posterior superior temporal gyrus: an intracranial study

Our brains are excellent at making predictions about what we should hear next, based on context. These predictions help us understand and interact with our surroundings. For example, when listening to a melody, we may predict the next note in a sequence.

Dr. Gerwin Schalk, Director of the Chen Frontier Lab for Applied Neurotechnology, and his fellow researchers wanted to understand what happens in the brain when an expected sound is omitted. They used a tool called electrocorticography, recording brain activity directly from the surface of the brain, and studied a particular region called the superior temporal gyrus (STG). Their findings are published in the July 15 edition of the journal Cerebral Cortex.

In the study, participants listened to a sequence of syllables that were mostly predictable, but occasionally one was left out. The researchers looked at the high-frequency activity in the brain when the expected sound was omitted. They discovered that the brain did react to the missing sounds, indicating a sort of mismatch detection or an alerting process. They could also distinguish heard syllables but not the identity of the omitted ones. These responses were found not only in the STG but also in the prefrontal cortex.

The study suggests that the STG is a key area in the brain responsible for predicting sounds in our environment. The high-frequency activity seems to be a sign of our brains signaling that something didn’t match up with what was expected.

In simpler terms, think of listening to a familiar song and expecting to hear a particular lyric next, but it’s suddenly skipped or omitted. This study looks at how the brain detects that “something is off” and tries to identify the parts of the brain involved in that process. It helps in understanding how our brains process sound and make predictions based on what we hear.

Read the paper on the journal Cerebral Cortex