scholarly journals Connectivity patterns shape sensory representation in a cerebellum-like network

2021 ◽  
Author(s):  
Daniel Zavitz ◽  
Elom A. Amematsro ◽  
Alla Borisyuk ◽  
Sophie J.C. Caron
Keyword(s):  
Learning Outcomes ◽  
Network Architecture ◽  
Mushroom Body ◽  
Structural Features ◽  
Projection Neurons ◽  
Sensory Representation ◽  
Learning Function ◽  
Kenyon Cells ◽  
Connectivity Patterns ◽  
Function Relationship

SUMMARYCerebellum-like structures are found in many brains and share a basic fan-out–fan-in network architecture. How the specific structural features of these networks give rise to their learning function remains largely unknown. To investigate this structure–function relationship, we developed a realistic computational model of an empirically very well-characterized cerebellum-like structure, the Drosophila melanogaster mushroom body. We show how well-defined connectivity patterns between the Kenyon cells, the constituent neurons of the mushroom body, and their input projection neurons enable different functions. First, biases in the likelihoods at which individual projection neurons connect to Kenyon cells allow the mushroom body to prioritize the learning of particular, ethologically meaningful odors. Second, groups of projection neurons connecting preferentially to the same Kenyon cells facilitate the mushroom body generalizing across similar odors. Altogether, our results demonstrate how different connectivity patterns shape the representation space of a cerebellum-like network and impact its learning outcomes.

scholarly journals The anterior paired lateral neuron normalizes odour-evoked activity at the mushroom body calyx

2021 ◽  
Author(s):  
Luigi Prisco ◽  
Stephan Hubertus Deimel ◽  
Hanna Yeliseyeva ◽  
Andre Fiala ◽  
Gaia Tavosanis
Keyword(s):  
Mushroom Body ◽  
Activity Patterns ◽  
Sensory Information ◽  
Input Circuit ◽  
Projection Neurons ◽  
Neuronal Populations ◽  
Kenyon Cells ◽  
Presynaptic Boutons ◽  
Evoked Activity

To identify and memorize discrete but similar environmental inputs, the brain needs to distinguish between subtle differences of activity patterns in defined neuronal populations. The Kenyon cells of the Drosophila adult mushroom body (MB) respond sparsely to complex olfactory input, a property that is thought to support stimuli discrimination in the MB. To understand how this property emerges, we investigated the role of the inhibitory anterior paired lateral neuron (APL) in the input circuit of the MB, the calyx. Within the calyx, presynaptic boutons of projection neurons (PNs) form large synaptic microglomeruli (MGs) with dendrites of postsynaptic Kenyon cells (KCs). Combining EM data analysis and in vivo calcium imaging, we show that APL, via inhibitory and reciprocal synapses targeting both PN boutons and KC dendrites, normalizes odour-evoked representations in MGs of the calyx. APL response scales with the PN input strength and is regionalized around PN input distribution. Our data indicate that the formation of a sparse code by the Kenyon cells requires APL-driven normalization of their MG postsynaptic responses. This work provides experimental insights on how inhibition shapes sensory information representation in a higher brain centre, thereby supporting stimuli discrimination and allowing for efficient associative memory formation.

scholarly journals The anterior paired lateral neuron normalizes odour-evoked activity in the Drosophila mushroom body calyx

eLife ◽  
2021 ◽  
Vol 10 ◽  
Author(s):  
Luigi Prisco ◽  
Stephan Hubertus Deimel ◽  
Hanna Yeliseyeva ◽  
André Fiala ◽  
Gaia Tavosanis
Keyword(s):  
Mushroom Body ◽  
Activity Patterns ◽  
Sensory Information ◽  
Input Circuit ◽  
Projection Neurons ◽  
Neuronal Populations ◽  
Kenyon Cells ◽  
Presynaptic Boutons ◽  
Evoked Activity

To identify and memorize discrete but similar environmental inputs, the brain needs to distinguish between subtle differences of activity patterns in defined neuronal populations. The Kenyon cells of the Drosophila adult mushroom body (MB) respond sparsely to complex olfactory input, a property that is thought to support stimuli discrimination in the MB. To understand how this property emerges, we investigated the role of the inhibitory anterior paired lateral neuron (APL) in the input circuit of the MB, the calyx. Within the calyx, presynaptic boutons of projection neurons (PNs) form large synaptic microglomeruli (MGs) with dendrites of postsynaptic Kenyon cells (KCs). Combining EM data analysis and in vivo calcium imaging, we show that APL, via inhibitory and reciprocal synapses targeting both PN boutons and KC dendrites, normalizes odour-evoked representations in MGs of the calyx. APL response scales with the PN input strength and is regionalized around PN input distribution. Our data indicate that the formation of a sparse code by the Kenyon cells requires APL-driven normalization of their MG postsynaptic responses. This work provides experimental insights on how inhibition shapes sensory information representation in a higher brain centre, thereby supporting stimuli discrimination and allowing for efficient associative memory formation.

Mushroom Body of the Honeybee

2017 ◽  
pp. 353-360
Author(s):  
Jürgen Rybak ◽  
Randolf Menzel
Keyword(s):  
Mushroom Body ◽  
Higher Order ◽  
Insect Species ◽  
Insect Brain ◽  
Projection Neurons ◽  
Kenyon Cells ◽  
Output Neurons ◽  
The Brain

The mushroom body (MB) in the insect brain is composed of a large number of densely packed neurons called Kenyon cells (KCs) (Drosophila, 2200; honeybee, 170,000). In most insect species, the MB consists of two caplike dorsal structures, the calyces, which contain the dendrites of KCs, and two to four lobes formed by collaterals of branching KC axons. Although the MB receives input and provides output throughout its whole structure, the neuropil part of the calyx receives predominantly multimodal input from sensory projection neurons (PNs) of second or a higher order, and the lobes send output neurons to many other parts of the brain, including recurrent neurons to the MB calyx. Widely branching, supposedly modulatory neurons (serotonergic, octopaminergic) innervate the MB at all levels (calyx, peduncle, and lobes), including the somata of KCs in the calyx (dopamine).

scholarly journals Sparsening and Temporal Sharpening of Olfactory Representations in the Honeybee Mushroom Bodies

2005 ◽  
Vol 94 (5) ◽  
pp. 3303-3313 ◽  
Author(s):  
Paul Szyszka ◽  
Mathias Ditzen ◽  
Alexander Galkin ◽  
C. Giovanni Galizia ◽  
Randolf Menzel
Keyword(s):  
Mushroom Body ◽  
Antennal Lobe ◽  
Activity Patterns ◽  
Projection Neuron ◽  
Insect Brain ◽  
Projection Neurons ◽  
Similar Response ◽  
Kenyon Cell ◽  
Cell Responses ◽  
Kenyon Cells

We explored the transformations accompanying the transmission of odor information from the first-order processing area, the antennal lobe, to the mushroom body, a higher-order integration center in the insect brain. Using Ca2+ imaging, we recorded activity in the dendrites of the projection neurons that connect the antennal lobe with the mushroom body. Next, we recorded the presynaptic terminals of these projection neurons. Finally, we characterized their postsynaptic partners, the intrinsic neurons of the mushroom body, the clawed Kenyon cells. We found fundamental differences in odor coding between the antennal lobe and the mushroom body. Odors evoked combinatorial activity patterns at all three processing stages, but the spatial patterns became progressively sparser along this path. Projection neuron dendrites and boutons showed similar response profiles, but the boutons were more narrowly tuned to odors. The transmission from projection neuron boutons to Kenyon cells was accompanied by a further sparsening of the population code. Activated Kenyon cells were highly odor specific. Furthermore, the onset of Kenyon cell responses to projection neurons occurred within the first 200 ms and complex temporal patterns were transformed into brief phasic responses. Thus two types of transformations occurred within the MB: sparsening of a combinatorial code, mediated by pre- and postsynaptic processing within the mushroom body microcircuits, and temporal sharpening of postsynaptic Kenyon cell responses, probably involving a broader loop of inhibitory recurrent neurons.

scholarly journals Inhibitory muscarinic acetylcholine receptors enhance aversive olfactory learning in adult Drosophila

eLife ◽  
2019 ◽  
Vol 8 ◽  
Author(s):  
Noa Bielopolski ◽  
Hoger Amin ◽  
Anthi A Apostolopoulou ◽  
Eyal Rozenfeld ◽  
Hadas Lerner ◽  
...  
Keyword(s):  
Synaptic Plasticity ◽  
Mushroom Body ◽  
Acetylcholine Receptors ◽  
Olfactory Learning ◽  
Muscarinic Acetylcholine Receptors ◽  
Projection Neurons ◽  
Kenyon Cell ◽  
Muscarinic Acetylcholine ◽  
Kenyon Cells ◽  
Output Neurons

Olfactory associative learning in Drosophila is mediated by synaptic plasticity between the Kenyon cells of the mushroom body and their output neurons. Both Kenyon cells and their inputs from projection neurons are cholinergic, yet little is known about the physiological function of muscarinic acetylcholine receptors in learning in adult flies. Here, we show that aversive olfactory learning in adult flies requires type A muscarinic acetylcholine receptors (mAChR-A), particularly in the gamma subtype of Kenyon cells. mAChR-A inhibits odor responses and is localized in Kenyon cell dendrites. Moreover, mAChR-A knockdown impairs the learning-associated depression of odor responses in a mushroom body output neuron. Our results suggest that mAChR-A function in Kenyon cell dendrites is required for synaptic plasticity between Kenyon cells and their output neurons.

scholarly journals Mechanisms underlying homeostatic plasticity in theDrosophilamushroom body in vivo

2020 ◽  
Vol 117 (28) ◽  
pp. 16606-16615 ◽  
Author(s):  
Anthi A. Apostolopoulou ◽  
Andrew C. Lin
Keyword(s):  
Mushroom Body ◽  
Feedback Inhibition ◽  
Homeostatic Plasticity ◽  
Projection Neurons ◽  
Kenyon Cell ◽  
Network Function ◽  
Kenyon Cells ◽  
Central Brain ◽  
Artificial Activation

Neural network function requires an appropriate balance of excitation and inhibition to be maintained by homeostatic plasticity. However, little is known about homeostatic mechanisms in the intact central brain in vivo. Here, we study homeostatic plasticity in theDrosophilamushroom body, where Kenyon cells receive feedforward excitation from olfactory projection neurons and feedback inhibition from the anterior paired lateral neuron (APL). We show that prolonged (4-d) artificial activation of the inhibitory APL causes increased Kenyon cell odor responses after the artificial inhibition is removed, suggesting that the mushroom body compensates for excess inhibition. In contrast, there is little compensation for lack of inhibition (blockade of APL). The compensation occurs through a combination of increased excitation of Kenyon cells and decreased activation of APL, with differing relative contributions for different Kenyon cell subtypes. Our findings establish the fly mushroom body as a model for homeostatic plasticity in vivo.

scholarly journals The complete connectome of a learning and memory center in an insect brain

2017 ◽  
Author(s):  
Katharina Eichler ◽  
Feng Li ◽  
Ashok Litwin-Kumar ◽  
Youngser Park ◽  
Ingrid Andrade ◽  
...  
Keyword(s):  
Learning And Memory ◽  
Mushroom Body ◽  
Negative Reinforcement ◽  
Insect Brain ◽  
Projection Neurons ◽  
Functional Studies ◽  
Output Neuron ◽  
Kenyon Cells ◽  
Output Neurons ◽  
Complete Circuit

Associating stimuli with positive or negative reinforcement is essential for survival, but a complete wiring diagram of a higherorder circuit supporting associative memory has not been previously available. We reconstructed one such circuit at synaptic resolution, theDrosophilalarval mushroom body, and found that most Kenyon cells integrate random combinations of inputs but a subset receives stereotyped inputs from single projection neurons. This organization maximizes performance of a model output neuron on a stimulus discrimination task. We also report a novel canonical circuit in each mushroom body compartment with previously unidentified connections: reciprocal Kenyon cell to modulatory neuron connections, modulatory neuron to output neuron connections, and a surprisingly high number of recurrent connections between Kenyon cells. Stereotyped connections between output neurons could enhance the selection of learned responses. The complete circuit map of the mushroom body should guide future functional studies of this learning and memory center.

scholarly journals Mushroom body input connections form independently of sensory activity in Drosophila melanogaster

2021 ◽  
Author(s):  
Tatsuya Hayashi ◽  
Alexander John MacKenzie ◽  
Ishani Ganguly ◽  
Hayley Smihula ◽  
Miles Solomon Jacob ◽  
...  
Keyword(s):  
Drosophila Melanogaster ◽  
Mushroom Body ◽  
Activity Patterns ◽  
Sensory Information ◽  
Population Level ◽  
Connectivity Pattern ◽  
Projection Neurons ◽  
Efficient Manner ◽  
Kenyon Cells ◽  
Sensory Activity

Associative brain centers, such as the insect mushroom body, need to represent sensory information in an efficient manner. In Drosophila melanogaster, the Kenyon cells of the mushroom body integrate inputs from a random set of olfactory projection neurons, but some projection neurons, namely those activated by a few ethologically meaningful odors, connect to Kenyon cells more frequently than others. This biased and random connectivity pattern is conceivably advantageous, as it enables the mushroom body to represent a large number of odors as unique activity patterns while prioritizing the representation of a few specific odors. How this connectivity pattern is established remains largely unknown. Here, we test whether the mechanisms patterning the connections between Kenyon cells and projection neurons depend on sensory activity or whether they are hardwired. We mapped a large number of mushroom body input connections in anosmic flies, flies lacking the obligate odorant co-receptor Orco, and in wildtype flies. Statistical analyses of these datasets reveal that the random and biased connectivity pattern observed between Kenyon cells and projection neurons forms normally in the absence of most olfactory sensory activity. This finding supports the idea that even comparatively subtle, population-level patterns of neuronal connectivity can be encoded by fixed genetic programs and are likely to be the result of evolved prioritization of ecologically and ethologically salient stimuli.

scholarly journals Predictive olfactory learning in Drosophila

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Chang Zhao ◽  
Yves F. Widmer ◽  
Sören Diegelmann ◽  
Mihai A. Petrovici ◽  
Simon G. Sprecher ◽  
...  
Keyword(s):  
Synaptic Plasticity ◽  
Dopaminergic Neurons ◽  
Mushroom Body ◽  
Trace Conditioning ◽  
Fruit Fly ◽  
Olfactory Learning ◽  
Shock Strength ◽  
Behavioral Experiments ◽  
Kenyon Cells ◽  
Output Neurons

AbstractOlfactory learning and conditioning in the fruit fly is typically modelled by correlation-based associative synaptic plasticity. It was shown that the conditioning of an odor-evoked response by a shock depends on the connections from Kenyon cells (KC) to mushroom body output neurons (MBONs). Although on the behavioral level conditioning is recognized to be predictive, it remains unclear how MBONs form predictions of aversive or appetitive values (valences) of odors on the circuit level. We present behavioral experiments that are not well explained by associative plasticity between conditioned and unconditioned stimuli, and we suggest two alternative models for how predictions can be formed. In error-driven predictive plasticity, dopaminergic neurons (DANs) represent the error between the predictive odor value and the shock strength. In target-driven predictive plasticity, the DANs represent the target for the predictive MBON activity. Predictive plasticity in KC-to-MBON synapses can also explain trace-conditioning, the valence-dependent sign switch in plasticity, and the observed novelty-familiarity representation. The model offers a framework to dissect MBON circuits and interpret DAN activity during olfactory learning.

scholarly journals Structural Features for Furan-Derived Fruity and Meaty Aroma Impressions

2016 ◽  
Vol 11 (10) ◽  
pp. 1934578X1601101
Author(s):  
Bettina Wailzer ◽  
Johanna Klocker ◽  
Peter Wolschann ◽  
Gerhard Buchbauer
Keyword(s):  
Neural Networks ◽  
Artificial Neural Networks ◽  
Network Architecture ◽  
Structural Features ◽  
Classification Rule ◽  
Classification Rate ◽  
Furan Derivatives ◽  
Information Index ◽  
The Neural Network ◽  
Artificial Neural

Furan derivatives are part of nearly all food aromas. They are mainly formed by thermal degradation of carbohydrates and ascorbic acid and from sugar-amino acid interactions during food processing. Caramel-like, sweet, fruity, nutty, meaty, and burnt odor impressions are associated with this class of compounds. In the presented work, structure-activity relationship (SAR) investigations are performed on a series of furan derivatives in order to find structural subunits, which are responsible for the particular characteristic flavors. Therefore, artificial neural networks are applied on a set of 35 furans with the aroma categories “meaty” or “fruity” to calculate a classification rule and class boundaries for these two aroma impressions. By training a multilayer perceptron network architecture with a backpropagation algorithm, a correct classification rate of 100% is obtained. The neural network is able to distinguish between the two studied groups by using the following significant descriptors as inputs: number of sulfur atoms, Looping Centric Information Index, Folding Degree Index and Petitjean Shape Indices. Finally, the results clearly demonstrate that artificial neural networks are successful tools to investigate non-linear qualitative structure-odor relationships of aroma compounds.

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