Auditory deviation detection has not only proven itself evolutionarily, it is also still vital for survival. This is because validly identifying and immediately processing deviating acoustic stimuli within a repetitive and familiar background noise environment can save lives in traffic, for example, and simply contributes to better orientation overall.

But how exactly does the brain enable this differentiated perception of stimuli? Until now, this has primarily been investigated for processes within the cortex, the higher brain region where complex cognitive functions are processed. Although recent studies have provided evidence that deviation detection is also controlled by deeper, subcortical regions, methodological limitations have so far prevented further insights.

Researchers at the Ernst Strüngmann Institute (ESI), Goethe University, and the MPI for Brain Research, all located in Frankfurt, have now made significant progress in this area. In a study published in the Journal of Neuroscience, they investigated stimulus processing within the inferior colliculus (IC), a brain stem region that has already been identified as playing a role in auditory processing. The researchers made use of auditory brainstem response (ABR) measurements, non-invasive EEG examinations that are characterized by excellent temporal resolution of subcortical processing and enabled them to obtain first-class measurement results.

The study results now suggest that not only the human cortex, but also deeper brain regions can quickly detect stimulus-specific deviations. The researchers were able to show that deviating acoustic stimuli are detected and processed very quickly, especially within the inferior colliculus. Depending on how the stimuli differ in terms of pitch, loudness, or timbre, for example, the brain stem can also recognize the type of deviation and respond to it in a stimulus-specific manner.

The researchers therefore suggest that, in addition to the cortex, the brainstem also plays a crucial role in controlling auditory attention. At the same time, the findings expand our understanding of how the human brain quickly detects deviating sounds within a familiar background noise and directs attention to relevant information.

This knowledge could have a lasting impact on improving hearing diagnostics, for example in the development of hearing tests that detect functional disorders in the auditory system much earlier and in a more personalized way, or in the further development of hearing devices and cochlear implants that can detect changes in acoustic stimuli much more sensitively. The findings also open up opportunities for the further development of diagnostic and therapeutic approaches for ADHD and other attention disorders.

In addition, the further development of technical systems such as voice assistants, alarm systems, and intelligent audio filters could also benefit from this knowledge by learning to recognize important acoustic signals more quickly and respond to them in a more targeted manner thanks to brain-inspired AI.

Original Publication
Johannes Wetekam, Nell Gotta, Luciana López-Jury, Julio Hechavarría, Manfred Kössl. Rapid and Stimulus-Specific Deviance Detection in the Human Inferior Colliculus Journal of Neuroscience 9 April 2025, 45 (15) e1846242025 [https://www.jneurosci.org/content/45/15/e1846242025]