In vivo studies of cortical organization and networks
The cortex is a laminated structure that is thought to underlie sequential information processing. Sensory input enters layer 4 (L4) from which activity quickly spreads to superficial layers 2/3 (L2/3) and deep layers 5/6 (L5/6). We pioneered in vivo 2-photon imaging in the auditory cortex to study the functional representation of sounds at the single cell level. We use new computational techniques based on dynamic systems and graph-theoretic measures to extract network dynamics at the single neuron and population level. Our work already identified the functional micro-architecture of the auditory cortex revealing the transformation of tonotopic organization in L4 to a more fractured organization in L2/3 (Bandyopadhyay et al Nature Neuroscience 2010, Winkowski & Kanold 2013, Winkowski et al. 2013, Meng et al. 2019, Liu et al. 2019). We also found that populations of neurons in A1 show neuronal avalanches (Bowen et al. 2019) and that they show a fractured columnar small world functional organization (Bowen et al. 2024). Recently, we showed that auditory cortex seems specialized for processing of harmonic stimuli (Jendrichovsky et al. Proceedings of the National Academy 2025, Chen et al. eNeuro 2026).
We pioneered the use of holographic optogenetic neural stimulation in the auditory cortex which allows targeted single-cell stimulation in vivo. We use these new techniques to investigate the 3D single-cell and population activity patterns and identify the influence of single neurons relative to the influence of ensembles of neurons on network dynamics. Using HONS, we showed that co-tuned networks in A1 rapidly rebalance their activity (Kang et al. eLife 2025)
Behavioral plasticity of cortical encoding
Sensory responses themselves depend on ongoing, i.e. spontaneous cortical activity, as well as the state and behavioral context of the animal. We showed that receptive field properties of neurons as well as the networks these neurons are embedded in can rapidly and adaptively be reshaped in a task dependent manner, indicating that even in primary auditory cortex encoding of stimuli is dependent on task- or context-dependent states (Francis et al Neuron 2018, Francis et al. Cell Reports 2022).
Top-down control of auditory cortex function
We do not know what neuronal circuits shape auditory cortical dynamics within and between laminae in a task dependent manner. We thus started to investigate potential sources of such signals and found that the orbitofrontal cortex (OFC) projects to the auditory cortex, sends behaviorally-related information, and can influence auditory cortex responses (Winkowski et al. 2013, Winkowski et al. 2018, Mittelstadt & Kanold Current Biology 2023).
How does learning reshape auditory cortex?
What happens then to the cortex when you learn? We started to investigate this by tracking auditory cortical responses when animals learned an auditory tone discrimination task. We used a fully automated system combining automatic head-fixation and wide field imaging to minimize experimenter interaction with the animal. This way we could track daily performance and neural activity changes. We find that learning recruits higher-order auditory fields and enhances the representation of behavioral variables in these areas (Wang et al. 2024). Moreover, learning increases the functional connectivity between primary and higher-order areas (Wang et al. 2024). Thus learning an auditory task leads to functional reorganization of the auditory cortex.
In vitro studies of cortical micro-circuits
To understand how neuronal circuits function we need to reveal connections within the network. To do this we use in vitro single and 2-photon photostimulation, coupled with patch clamp recordings and 2-photon imaging. Photostimulation allows us to selectively stimulate neurons and we can then observe which other neurons respond. Thus we essentially can create input-output maps of targeted neurons. By performing these studies across layers and ages we aim to assemble a wiring diagram of the adult and developing brain. Our work already identified the micro-circuitry of L2/3 and L4 auditory cortex (Watkins et al. 2014, Meng et al. 2017) and how it can change (Meng et al. 2015, 2017, 2019).
Clinical relevance
This work is aimed at revealing how cortical circuits process sound information in adults. This information is obviously important in understanding how the brain works, but also serves as a crucial reference for evaluating the effects of injury or aging. Moreover, understanding how neural circuits in the auditory cortex process sounds and amplify important sound sources and suppress distractors can also lead to the design of better hearing aids, cochlear implants, and AI systems.
Key Publications
P. Jendrichovsky, S. Khosravi, A. Rupasinghe, K. Maximov, P. Guo, B. Babadi, P.O. Kanold, “Patchy harmonic functional connectivity of the mouse auditory cortex”, Proc. Natl. Acad. Sci. U.S.A. 2025
H. Kang, T. Babola, P.O. Kanold,“Rapid rebalancing of co-tuned ensemble activity in the auditory cortex” eLife 2025
J. Mittelstadt, P.O. Kanold , “Orbitofrontal cortex conveys stimulus and task information to the auditory cortex” Current Biology 2023
G. Calhoun, C.-T. Chen, P.O. Kanold,“Bilateral widefield calcium imaging reveals circuit asymmetries and lateralized functional activation of the mouse auditory cortex” Proc. Natl. Acad. Sci, USA 2023
N. Francis , S. Mukherjee, L. Koçillari , S. Panzeri, B. Babadi, P O. Kanold , “Sequential Transmission of Task-Relevant Information in Cortical Neuronal Networks”, Cell Reports 2022
N. Francis, D. E Winkowski, A. Sheikhattar, K. Armengol, B. Babadi, P.O. Kanold “Small networks Encode Decision-Making in Auditory Cortex”, Neuron 2018
D. Winkowski*, S. Bandyopadhyay*, S. Shamma, P.O. Kanold,”Frontal cortex activation causes rapid plasticity of auditory cortical processing”, Journal of Neuroscience 2013
D. Winkowski, P.O. Kanold,”Laminar transformation of frequency organization in auditory cortex”, Journal of Neuroscience 2013
S. Bandyopadhyay, S. Shamma, P.O. Kanold,”Dichotomy of functional organization in the mouse auditory cortex”, Nature Neuroscience, 2010.
