Biology subjects

Nocon, J. C.

Publications and source records attributed to Nocon, J. C..

5 recordsLinked to original sources

bioRxiv2026

Parvalbumin and somatostatin interneurons support distinct computations during auditory scene analysis

Auditory scene analysis requires cortical circuits to preserve target-sound representations while suppressing interference from competing sound sources. Although spatial separation between tar{-}get and masker sounds can substantially improve perception, the inhibitory circuit mechanisms that transform spatial separation into improved target sound representations remain poorly un{-}derstood. Here, we used a multi-speaker auditory environment to present target sounds alone (clean) or together with spatially distributed competing white noise (masked) trials while record{-}ing auditory cortical activity in awake mice. By combining electrophysiology, cell-type-specific optogenetic suppression, and spike-distance-based neural classifiers, we examined how parval{-}bumin (PV) and somatostatin (SST) interneurons contribute to spatial processing in complex auditory scenes. PV and SST interneurons made dissociable, context-dependent contributions. PV suppression broadly altered spatial tuning properties, including tuning width, modulation depth, centroid, and sparseness, and reduced target-sound discriminability under clean condi{-}tions. In contrast, SST suppression produced comparatively modest effects on spatial tuning but selectively impaired neural discrimination only during masked trials thereby weakening the im{-}provement in target discrimination normally associated with spatial release from masking. Thus, the interneuron population that most strongly altered spatial tuning was not the population that most strongly disrupted masked discrimination. This reveals a dissociation between cortical in{-}hibitory mechanisms supporting spatial receptive-field structure and those supporting target-masker segregation. Together, these findings suggest that PV-mediated inhibition refines the fi{-}delity of auditory cortical representations, whereas SST-mediated inhibition enhances separation of simultaneously spatially competing sound sources, providing complementary inhibitory mecha{-}nisms for auditory scene analysis.

neuroscience↗

bioRxiv2022

A Robust, Compact and Diverse Population Code for Competing Sounds in Auditory Cortex

Cortical circuits encoding sensory information consist of populations of neurons, yet how information aggregates via pooling individual cells remains poorly understood. Such pooling may be particularly important in noisy settings where single neuron encoding is degraded. One example is the cocktail party problem, with competing sounds from multiple spatial locations. How populations of neurons in auditory cortex (ACx) code competing sounds have not been previously investigated. Here, we apply a novel information theoretic approach to estimate information in populations of neurons in ACx about competing sounds from multiple spatial locations, including both summed population (SP) and labeled line (LL) codes. We find that a small subset of neurons is sufficient to nearly maximize mutual information over different spatial configurations, with the LL code outperforming the SP code, and approaching information levels attained without noise. Moreover, with a LL code, units with diverse spatial responses, including both regular and narrow-spiking units, constitute the best pool. Finally, information in the population increases with spatial separation between target and masker, in correspondence with behavioral results on spatial release from masking in human and animals. Taken together, our results reveal that a compact and diverse population of neurons in ACx provide a robust code for competing sounds from different spatial locations.

neuroscience↗

bioRxiv2022

Differential Inhibitory Responses to Temporal Features Enhance Cortical Coding of Dynamic Stimuli: A Network Model

Cortical circuits feature both excitatory and inhibitory cells that underlie the encoding of dynamic sensory stimuli, e.g., speech, music, odors, and natural scenes. While previous studies have shown that inhibition plays an important role in shaping the neural code, how excitatory and inhibitory cells coordinate to enhance encoding of temporally dynamic stimuli is not fully understood. Recent experimental recordings in mouse auditory cortex have shown that optogenetic suppression of parvalbumin neurons results in a decrease of neural discriminability of dynamic stimuli. Here, we present a multilayer model of a cortical circuit that mechanistically explains these results. The model is based on parvalbumin neurons which respond to both stimulus onsets and offsets, as observed experimentally, and incorporates characteristic shortterm synaptic plasticity profiles of excitatory and parvalbumin neurons. We reveal that by tuning the relative strengths of onset and offset inputs to parvalbumin neurons, the model generates different regimes of coding dominated by rapid firing rate modulations or spike timing. Moreover, the model replicates the experimentally observed reduction in neural discrimination performance during optogenetic suppression of parvalbumin neurons. These results suggest that distinct onset and offset inputs to parvalbumin neurons enhance cortical discriminability of dynamic stimuli by encoding distinct temporal features, enhancing temporal coding, and reducing cortical noise. New & NoteworthyHere we propose a model for the mechanisms that underlie neuron responses in the auditory cortex. This study focuses on single channel tuning of simple interactions between neurons. Using physiologically relevant parameters that underly parvalbumin and excitatory neurons, in the proposed artificial network, we show that we can recreate observed results in live studies.

neuroscience↗

bioRxiv2021

PV neurons improve cortical complex scene analysis by enhancing timing-based coding

Cortical representations supporting many cognitive abilities emerge from underlying circuits comprised of several different cell types. However, cell type-specific contributions to rate and timing-based cortical coding are not well-understood. Here, we investigated the role of parvalbumin (PV) neurons in cortical complex scene analysis. Many complex scenes contain sensory stimuli which are highly dynamic in time and compete with stimuli at other spatial locations. PV neurons play a fundamental role in balancing excitation and inhibition in cortex and sculpting cortical temporal dynamics; yet their specific role in encoding complex scenes via timing-based coding, and the robustness of temporal representations to spatial competition, has not been investigated. Here, we address these questions in auditory cortex using a cocktail party-like paradigm, integrating electrophysiology, optogenetic manipulations, and a family of spike-distance metrics, to dissect PV neurons contributions towards rate and timing-based coding. We find that suppressing PV neurons degrades cortical discrimination of dynamic sounds in a cocktail party-like setting via changes in rapid temporal modulations in rate and spike timing, over a wide range of time-scales. Our findings suggest that PV neurons play a critical role in enhancing cortical temporal coding and reducing cortical noise, thereby improving representations of dynamic stimuli in complex scenes. Significance StatementOne impressive example of sensory perception by the brain is its ability to analyze complex scenes, e.g., following what a friend is saying at a party amongst other speakers. Although some humans can solve this problem with relative ease, it remains very difficult for humans with a variety of impairments, e.g., hearing impairments, ADHD, and autism. The brain mechanisms underlying complex scene analysis remain poorly understood. Here, we recorded neural activity in auditory cortex in a complex auditory scene. When we suppressed PV neuron activity in auditory cortex, cortical performance decreased, and the timing of cortical responses was degraded. Our findings suggest that PV neurons improve the brains ability to analyze complex scenes by enhancing the timing of cortical responses while reducing cortical noise.

neuroscience↗

bioRxiv2020

Oscillatory activity in alpha/beta frequencies coordinates auditory and prefrontal cortices during extinction learning

Cortical synchrony is theorized to contribute to communication between connected networks during executive functioning. To understand the functional role of neural synchrony in cognitive flexibility, we recorded from auditory cortex (AC) and medial prefrontal cortex (mPFC), while mice performed an auditory extinction learning task. We found that while animals gradually showed reduced responding to the unrewarded tone over hundreds of trials, the power of local field potential (LFP) oscillations (8-18 Hz, centered at alpha/beta frequencies) in AC and mPFC exhibited immediate and robust increases, prior to behavioral changes. The strength of LFP alpha/beta power in the mPFC, but not AC, was strongly correlated with the behavioral performance that mice would achieve later in the training session. Further, we found that coherence between AC and mPFC at 8-18Hz was selectively enhanced only after mice learned to suppress licking, and this LFP coherence increase coincided with a reduction in spiking rate for the unrewarded tone in AC. These results reveal that enhanced interactions between PFC and AC is an inherent property of auditory discrimination learning, and that coordinated alpha/beta oscillations contribute to cognitive flexibility.

neuroscience↗