Theses Doctoral

Multidimensional encoding of context in auditory cortex

Shymkiv, Yuriy

The brain is a complex system that seamlessly solves intricate problems with unprecedented efficiency. Part of the brain’s task is gathering sensory information from its environment, processing and representing it in a highly efficient manner. One of the key mechanisms used by sensory pathways is to process information by its context, disregarding redundancies and selectively focusing on novelty (deviance/change detection). A quantitative measure for how well the brain can detect novel stimuli is measured with the oddball paradigm and the mismatch negativity component (MMN). Deficits in context modulation and reduced MMN components are associated with mental disorders such as schizophrenia.

Typically, oddball studies are done with coarse recording methods like EEG and MEG, and the network response dynamics underlying novelty detection is still unclear. In this work we used two-photon calcium imaging in awake mice listening to acoustic oddball stimuli, and recorded from large populations of neurons in primary and secondary auditory cortex (AC). We analyzed single cell and population representations of contextual information and found robust context modulation across all recorded AC regions. Responses to redundant stimuli were strongly suppressed while those to novel stimuli amplified. Furthermore, responses to identical stimuli in deviant, neutral, or redundant contexts were encoded by distinct populations of neurons, indicating an even stronger context encoding than seen in average population activity.

Finally, we found that stimulus complexity also has an effect on where and to what extent context information is most robustly expressed. A2 was the most engaged in context processing for simple tones, while for complex frequency gratings A1 was doing novelty detection to the largest extent. My results provide a circuit basis for novelty detection in the auditory cortex, as a stepping stone to understand how processing of sensory stimuli is carried out by the brain.


This item is currently under embargo. It will be available starting 2025-02-01.

More About This Work

Academic Units
Biological Sciences
Thesis Advisors
Yuste, Rafael
Ph.D., Columbia University
Published Here
February 8, 2023