Dynamics underlying auditory‐object‐boundary detection in primary auditory cortex

Описание: Reference:
Pradeep Dheerendra, Nicolas Barascud, Sukhbinder Kumar, Tobias Overath, and Timothy D. Griffiths. "Dynamics underlying auditory‐object‐boundary detection in primary auditory cortex." European Journal of Neuroscience (2021).

https://doi.org/10.1111/ejn.15471

Our brain can identify any new sound as it appears in the environment, separate it from other existing sounds and represent it as a distinct object in our mind.  Thus auditory object analysis requires the fundamental perceptual process of detecting boundaries between auditory objects. However, the dynamics underlying the identification of discontinuities at object boundaries are not well understood.

Since sounds may contain multiple components that vary in frequency and time, this process requires a mechanism that monitors the statistics of the time-frequency space. So we employed an artificial sound composed of frequency modulated ramps, where boundaries were created by changing the underlying spectro-temporal statistics. Subjects were tasked to detect auditory object boundary. Behaviour results show robust performance.

We collected magnetoencephalographic data from human volunteers. We observed a slow less than 1 Hz drift in the neuromagnetic signal after the auditory object boundary. This response evoking this drift signal was source localised close to Heschl’s gyrus bilaterally, which is in agreement with a previous functional magnetic resonance imaging study that found Heschl’s gyrus to be involved in the detection of similar auditory object boundaries.

Time–frequency analysis demonstrated suppression in alpha and beta bands that occurred after the drift signal. The induced alpha suppression was source localised to Right supramarginal gyrus, and Right superior frontal gyrus, while beta suppression was source localised to Right angular gyrus.

So we conclude that new auditory objects in a complex acoustic scene can be signalled by changes in the spectro-temporal coherence.

This accumulation of evidence occurs in the primary auditory cortex

Thank you.