Olfactory system

  • Article
    | Open Access

    Despite the profound knowledge of sex pheromones, little is known about the coevolutionary mechanisms and constraints on their production and detection. Whole-genome sequences from 99 drosophilids, with chemical and behavioural data, show that sex pheromones and their cognate olfactory channels evolve rapidly and independently.

    • Mohammed A. Khallaf
    • , Rongfeng Cui
    •  & Markus Knaden
  • Article
    | Open Access

    The physical distance between synaptic Ca2+ channels and sensors modulates short-term plasticity (STP). Here, the authors show that synaptic release factors Unc13A and Unc13B distinctly couple with Ca2+ channels and contribute to the neural decoding of distinct sensory information in Drosophila.

    • Atefeh Pooryasin
    • , Marta Maglione
    •  & Stephan J. Sigrist
  • Article
    | Open Access

    Shani-Narkiss et al. established an experimental system to test the functional role of adult born neurons (ABNs) on Mitral Cell (MC) coding. Silencing ABNs, unexpectedly, quenched MC odor responses. A computational model provides a mechanistic explanation to the functional role of adult-born neurons in circuit computation of the olfactory bulb.

    • H. Shani-Narkiss
    • , A. Vinograd
    •  & A. Mizrahi
  • Article
    | Open Access

    This study shows that cerebellar molecular layer interneurons (MLIs) develop responses encoding for identity of the stimulus in an associative learning task. Chemogenetic inhibition of MLIs decreased the ability of mice to discriminate stimuli suggesting that MLIs encode for stimulus valence.

    • Ming Ma
    • , Gregory L. Futia
    •  & Diego Restrepo
  • Article
    | Open Access

    It is not entirely understood how network plasticity produces the coding of predicted value during stimulus-outcome learning. Here, the authors reveal a reinforcing loop in distributed limbic circuits, transforming sensory stimuli into reward prediction coding broadcasted by dopamine neurons to the brain.

    • Lars-Lennart Oettl
    • , Max Scheller
    •  & Wolfgang Kelsch
  • Article
    | Open Access

    Here, the authors show that rats’ performance on olfactory decision tasks is best explained by a Bayesian model that combines reinforcement-based learning with accumulation of uncertain sensory evidence. The results suggest that learning is a critical factor contributing to speed-accuracy tradeoffs.

    • André G. Mendonça
    • , Jan Drugowitsch
    •  & Zachary F. Mainen
  • Article
    | Open Access

    Odours are powerful stimuli used by most organisms to guide behaviour. Here, the authors identify populations of neurons within the anterior olfactory nucleus (AON) which are necessary and sufficient for the behavioural expression of odour memory.

    • Afif J. Aqrabawi
    •  & Jun Chul Kim
  • Article
    | Open Access

    Measures of neural processing can be obtained non-invasively from all areas of the human brain but one, the olfactory bulb. Here, the authors show that signals obtained from EEG electrodes at the nasal bridge represent responses from the human olfactory bulb, the so-called Electrobulbogram.

    • Behzad Iravani
    • , Artin Arshamian
    •  & Johan N. Lundström
  • Article
    | Open Access

    Male orchid bees collect scents from the environment to attract females for mating. Here, Brand et al. combine population genomic, perfume chemistry, and functional analyses to show how divergence in odorant receptor genes may be driving reproductive divergence between two orchid bee species.

    • Philipp Brand
    • , Ismael A. Hinojosa-Díaz
    •  & Santiago R. Ramírez
  • Article
    | Open Access

    Olfactory bulb neurogenesis raises the question of how persistent olfactory memories are retained while remaining flexible to encode new memories. Here, the authors show that new neurons can only support a single odor memory within their critical period of integration into the circuit.

    • Jérémy Forest
    • , Mélissa Moreno
    •  & Nathalie Mandairon
  • Article
    | Open Access

    The precise cell-type specific role of inhibitory interneurons in regulating sensory responses in the olfactory bulb is not known. Here, the authors report that removing GABAergic inhibition from one layer differentially affects response dynamics of the two main output cell types and changes odor mixture processing.

    • Gary Liu
    • , Emmanouil Froudarakis
    •  & Benjamin R. Arenkiel
  • Article
    | Open Access

    Inter-organismal signaling is essential for animals to navigate and survive in their natural environment, yet is unclear how these chemical communication channels may have evolved. Here, authors show that TYRA-2, an endogenous tyramine/octopamine receptor, is required for the chemosensation of an octopamine-derived pheromone and that this signaling system represents an inter-organismal communication channel that evolved via co-option of a neurotransmitter and its cognate receptor

    • Christopher D. Chute
    • , Elizabeth M. DiLoreto
    •  & Jagan Srinivasan
  • Article
    | Open Access

    In Drosophila antenna, an unusual non-synaptic form of lateral inhibition occurs between subtypes of compartmentalized olfactory receptor neurons (ORNs). Here, authors show that direct electrical (ephaptic) interactions mediate lateral inhibition between ORNs, with physically larger ORNs dominating ephaptic interactions.

    • Ye Zhang
    • , Tin Ki Tsang
    •  & Chih-Ying Su
  • Article
    | Open Access

    Neural architecture may be shaped by selection, but is likely also constrained by development. Here, Keesey and colleagues find an inverse relationship between allocation towards visual and olfactory sensory systems across the genus Drosophila, which may reflect a developmental trade-off.

    • Ian W. Keesey
    • , Veit Grabe
    •  & Bill S. Hansson
  • Article
    | Open Access

    Neuronal activity leads to a local increase in blood flow and volume, a process termed hyperaemia. Here, the authors employ multiple imaging approaches of neuronal and vascular activity at varying resolution to delineate the spatiotemporal dynamics of neurovascular coupling evoked by odours in the olfactory bulb.

    • Davide Boido
    • , Ravi L. Rungta
    •  & Serge Charpak
  • Article
    | Open Access

    Olfactory experience can alter the relative abundance of neurons expressing specific chemoreceptors. Here, the authors demonstrate that the distinct odor experiences of sex-separated male and female mice induce sex-specific differences in the abundance of neurons that detect sexually dimorphic odors.

    • Carl van der Linden
    • , Susanne Jakob
    •  & Stephen W. Santoro
  • Article
    | Open Access

    Olfactory marker protein (OMP) expressed in all olfactory sensory neurons (OSN) is required for proper signal transduction and odor discrimination. Here, the authors report that OMP deletion leads to formation of glomeruli with axons from heterogeneous OSNs due to local axonal mistargeting.

    • Dinu F. Albeanu
    • , Allison C. Provost
    •  & Venkatesh N. Murthy
  • Article
    | Open Access

    It is now possible to predict what a chemical smells like based on its chemical structure, however to date, this has only been done for a small number of odor descriptors. Here, using natural-language semantic representations, the authors demonstrate prediction of a much wider range of descriptors.

    • E. Darío Gutiérrez
    • , Amit Dhurandhar
    •  & Guillermo A. Cecchi
  • Article
    | Open Access

    Olfaction, the sense of smell, may have originally evolved to aid navigation in space, but there is no direct evidence of a link between olfaction and navigation in humans. Here the authors show that olfaction and spatial memory abilities are correlated and rely on similar brain regions in humans.

    • Louisa Dahmani
    • , Raihaan M. Patel
    •  & Véronique D. Bohbot
  • Article
    | Open Access

    Increasing evidence suggest that olfactory receptors can carry additional functions besides olfaction. Here, Chéret et al. show that stimulation of the olfactory receptor ORT2A4 by the odorant Sandalore® stimulates growth of human scalp hair follicles ex vivo, suggesting the use of ORT2A4-targeting odorants as hair growth-promoting agents.

    • Jérémy Chéret
    • , Marta Bertolini
    •  & Ralf Paus
  • Article
    | Open Access

    Sensory stimuli are encountered in multiple ways necessitating a flexible and adaptive neural population code for identification. Here, the authors show that the dynamics of odor coding in the locust antennal lobe varies with stimulus context so as to enhance the target stimulus representation.

    • Srinath Nizampatnam
    • , Debajit Saha
    •  & Baranidharan Raman
  • Article
    | Open Access

    Odorous chemicals broadly activate subsets of olfactory receptors in the nose, but how individual receptors contribute to behavioral sensitivity is not clear. Here, the authors demonstrate that detection thresholds in mice are set solely by the highest affinity receptor for a given odorant.

    • Adam Dewan
    • , Annika Cichy
    •  & Thomas Bozza
  • Article
    | Open Access

    Hippocampus is necessary for integrating the context with sensory cues to retrieve memory for unique episodes. Here, the authors show that inhibiting topographically organized projections from hippocampus to the anterior olfactory nucleus independently impairs spatial and temporal odour memory recall.

    • Afif J. Aqrabawi
    •  & Jun Chul Kim
  • Article
    | Open Access

    The molecular mechanisms underlying synapse formation in the olfactory bulb are not fully understood. Here the authors demonstrate that semaphorin 7A on olfactory sensory neurons, and its receptor plexin C1 expressed on mitral and tufted cells, is required for correct synapse formation.

    • Nobuko Inoue
    • , Hirofumi Nishizumi
    •  & Hitoshi Sakano
  • Article
    | Open Access

    Mitral/tufted (MT) cells connect to a single glomerulus and receive inputs from sensory neurons expressing the same odorant receptor. Here the authors report that sister MT cells connected to the M72 glomerulus exhibit variable responses to most M72 ligands but respond in a reproducible and stereotyped way to a high-affinity M72 ligand.

    • Ezequiel M. Arneodo
    • , Kristina B. Penikis
    •  & Dmitry Rinberg
  • Article
    | Open Access

    Time-lapse imaging studies of more than a day in the fly brain have been infeasible until now. Here the authors present a laser microsurgery approach to create a permanent window in the fly cuticle to enable time-lapse imaging of neural architecture and dynamics for up to 10–50 days.

    • Cheng Huang
    • , Jessica R. Maxey
    •  & Mark J. Schnitzer
  • Article
    | Open Access

    Odor-guided spatial behaviours are difficult to study due to the challenge of controlling chemical concentrations in space and time. Here the authors present a precise odor delivery system to generate a olfactory virtual landscape that engages hippocampal place cells in mice.

    • Brad A. Radvansky
    •  & Daniel A. Dombeck
  • Article
    | Open Access

    Microcircuit tracing reconstructions often rely on statistical labeling that may not detect all inputs and outputs of a microcircuit. Here the authors employ a novel electroporation approach to densely label neurons and demonstrate its ability to identify sparse anatomical features in the olfactory glomerulus.

    • D. Schwarz
    • , M. Kollo
    •  & A. T. Schaefer
  • Article
    | Open Access

    Odor identity remains stable despite changes in concentration yet the neural mechanisms are relatively unknown. Here the authors test a primacy coding model using an optogenetic masking paradigm in mice to show that a set of earliest activated receptors are sufficient to make decisions about odor identity across concentrations.

    • Christopher D. Wilson
    • , Gabriela O. Serrano
    •  & Dmitry Rinberg
  • Article
    | Open Access

    “Each olfactory sensory neuron expresses a single odorant receptor gene from either class I or class II genes. Here, the authors identify an enhancer for mouse class I genes, that is highly conserved, and regulates most class I genes expression by acting over ~ 3 megabases within the whole cluster.”

    • Tetsuo Iwata
    • , Yoshihito Niimura
    •  & Junji Hirota
  • Article
    | Open Access

    Cholinergic neurons innervate multiple layers in the main olfactory bulb but the precise circuitry of this input is not known. Here the authors show that VGLUT3+ cholinergic neurons selectively innervate deep short axon cells in specific layers and elicit robust monosynaptic GABAergic and nicotinic postsynaptic currents.

    • Daniel T. Case
    • , Shawn D. Burton
    •  & Rebecca P. Seal
  • Article
    | Open Access

    How neuronal migration and axon growth coordinate during development is only partially understood. Here the authors use quantitative imaging to characterise the morphogenesis of the zebrafish olfactory placode and report an unexpected phenomenon, whereby axons extend through the passive movement of neuron cell bodies away from tethered axon tips.

    • M. A. Breau
    • , I. Bonnet
    •  & S. Schneider-Maunoury
  • Article
    | Open Access

    Cuticular hydrocarbons (CHC) mediate the interactions between individuals in eusocial insects, but the sensory receptors for CHCs are unclear. Here the authors show that in ants such as H. saltator, the 9-exon subfamily of odorant receptors (HsOrs) responds to CHCs, and ectopic expression of HsOrs in Drosophila neurons imparts responsiveness to CHCs.

    • Gregory M. Pask
    • , Jesse D. Slone
    •  & Anandasankar Ray
  • Article
    | Open Access

    Humans and animals recognize an odorant across a range of odorant concentrations, but where in the olfactory processing pathway this invariance is generated is unclear. By measuring and comparing olfactory bulb outputs to inputs, the authors show that the olfactory bulb participates in generating the perception of odorant concentration invariance.

    • Douglas A. Storace
    •  & Lawrence B. Cohen