Parallel processing by distinct classes of principal neurons in the olfactory cortex

Nagappan, Shivathmihai; Franks, Kevin M.

doi:10.7554/elife.73668

Cited by 13 publications

(11 citation statements)

References 57 publications

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“…Previous work has shown that only deeper layer neurons send projections to the OB, and the superficial semilunar cells lack feedback projections (Mazo et al, 2017, Diodato et al, 2016. A recent study (Nagappan and Franks, 2021) indicated that semilunar and principal cells have many common properties, with only subtle differences in response tuning -therefore, our results are likely to generalize to other principal cells in PC. A third caveat is that the axonal and bouton activity could be influenced by local bulbar circuitry and may not faithfully represent somatic activity in PC neurons.…”

Section: Limitations Of Our Studysupporting

confidence: 61%

Distinct information conveyed to the olfactory bulb by feedforward input from the nose and feedback from the cortex

Zak,

Reddy,

Konanur

et al. 2023

Preprint

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Sensory systems are organized hierarchically, but feedback projections frequently disrupt this order. In the olfactory bulb (OB), cortical feedback projections numerically match sensory inputs. To unravel information carried by these two streams, we imaged the activity of olfactory sensory neurons (OSNs) and cortical axons in the mouse OB using calcium indicators, multiphoton microscopy, and diverse olfactory stimuli. Odorant mixtures of increasing complexity evoked progressively denser OSN activity, yet cortical feedback activity was of similar sparsity for all stimuli. Representations of complex mixtures were similar in OSNs but were decorrelated in cortical axons. While OSN responses to increasing odorant concentrations exhibited a sigmoidal relationship, cortical axonal responses were complex and non-monotonic, which could be explained by a model with activity-dependent feedback inhibition in the cortex. Our study indicates that early-stage olfactory circuits have access to both local feedforward signals and global, efficiently formatted information about odor scenes through cortical feedback.

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Section: Limitations Of Our Studysupporting

confidence: 61%

Distinct information conveyed to the olfactory bulb by feedforward input from the nose and feedback from the cortex

Zak,

Reddy,

Konanur

et al. 2023

Preprint

View full text Add to dashboard Cite

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“…The study of the role of the PCx in olfaction has recently been boosted by selective genetic techniques, allowing researchers to examine how the individual cellular components relate to olfaction ( Franks et al, 2011 ; Nagappan and Franks, 2021 ). The PCx, also known as the olfactory cortex, receives inputs from the OB and constructs a robust odor representation ( Bolding et al, 2020 ).…”

Section: Discussionmentioning

confidence: 99%

Mechanisms and functions of respiration-driven gamma oscillations in the primary olfactory cortex

González

Torterolo

Tort

2023

eLife

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Gamma oscillations are believed to underlie cognitive processes by shaping the formation of transient neuronal partnerships on a millisecond scale. These oscillations are coupled to the phase of breathing cycles in several brain areas, possibly reflecting local computations driven by sensory inputs sampled at each breath. Here, we investigated the mechanisms and functions of gamma oscillations in the piriform (olfactory) cortex of awake mice to understand their dependence on breathing and how they relate to local spiking activity. Mechanistically, we find that respiration drives gamma oscillations in the piriform cortex, which correlate with local feedback inhibition and result from recurrent connections between local excitatory and inhibitory neuronal populations. Moreover, respiration-driven gamma oscillations are triggered by the activation of mitral/tufted cells in the olfactory bulb and are abolished during ketamine/xylazine anesthesia. Functionally, we demonstrate that they locally segregate neuronal assemblies through a winner-take-all computation leading to sparse odor coding during each breathing cycle. Our results shed new light on the mechanisms of gamma oscillations, bridging computation, cognition and physiology.

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“…We found that the yield decreases across days, perhaps due to a move from layer 2 towards 1 (2b to 2a), which would correspond to increasing proportion of semilunar cells. However, prior work has shown that semilunar cells are less selective for odors [ 56 ]. Thus, this hypothetical is not consistent with the current knowledge of how layers and selectivity interact.…”

Section: Discussionmentioning

confidence: 99%

Experience-dependent evolution of odor mixture representations in piriform cortex

et al. 2023

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Rodents can learn from exposure to rewarding odors to make better and quicker decisions. The piriform cortex is thought to be important for learning complex odor associations; however, it is not understood exactly how it learns to remember discriminations between many, sometimes overlapping, odor mixtures. We investigated how odor mixtures are represented in the posterior piriform cortex (pPC) of mice while they learn to discriminate a unique target odor mixture against hundreds of nontarget mixtures. We find that a significant proportion of pPC neurons discriminate between the target and all other nontarget odor mixtures. Neurons that prefer the target odor mixture tend to respond with brief increases in firing rate at odor onset compared to other neurons, which exhibit sustained and/or decreased firing. We allowed mice to continue training after they had reached high levels of performance and find that pPC neurons become more selective for target odor mixtures as well as for randomly chosen repeated nontarget odor mixtures that mice did not have to discriminate from other nontargets. These single unit changes during overtraining are accompanied by better categorization decoding at the population level, even though behavioral metrics of mice such as reward rate and latency to respond do not change. However, when difficult ambiguous trial types are introduced, the robustness of the target selectivity is correlated with better performance on the difficult trials. Taken together, these data reveal pPC as a dynamic and robust system that can optimize for both current and possible future task demands at once.

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Parallel processing by distinct classes of principal neurons in the olfactory cortex

Cited by 13 publications

References 57 publications

Distinct information conveyed to the olfactory bulb by feedforward input from the nose and feedback from the cortex

Distinct information conveyed to the olfactory bulb by feedforward input from the nose and feedback from the cortex

Mechanisms and functions of respiration-driven gamma oscillations in the primary olfactory cortex

Experience-dependent evolution of odor mixture representations in piriform cortex

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