Project

Back to overview

Bottom-up and top-down neuronal computations in olfaction

English title Bottom-up and top-down neuronal computations in olfaction
Applicant Friedrich Rainer
Number 172925
Funding scheme Project funding (Div. I-III)
Research institution Friedrich Miescher Institute for Biomedical Research
Institution of higher education Institute Friedrich Miescher - FMI
Main discipline Neurophysiology and Brain Research
Start/End 01.04.2018 - 31.03.2022
Approved amount 992'597.00
Show all

Keywords (8)

Olfactory system; In vivo imaging; Top-down processing; Learning; Neuronal circuit; Circuit reconstruction; Neuronal computation; Zebrafish

Lay Summary (German)

Lead
Die Informationsverarbeitung von den Sinnesorganen zu höheren Gehirnarealen wird als «bottom-up» bezeichnet, während die umgekehrte Richtung «top-down» genannt wird. Dieser gegenläufige Informationsaustausch liegt wahrscheinlich der Integration von sensorischer Information mit Information aus dem Gedächtnis zugrunde. Dieses Projekt analysiert die Koordination von bottom-up und top-down Prozessen während des Lernens mithilfe neuer Methoden zur Rekonstruktion komplexer neuronaler Netzwerke.
Lay summary

Inhalt und Ziele des Forschungsprojekts

Das Projekt untersucht die Verarbeitung von Geruchsinformation im olfaktorischen System des Zebrafisches. Sensorische Information aus der Nase (bottom-up) konvergiert mit Information aus höheren Gehirnarealen (top-down) in den Körnerzellen des Riechkolbens. Wir werden die Entwicklung der top-down Verbindungen und des Körnerzell-Netzwerks studieren und dessen Struktur mithilfe neuer dreidimensionaler Elektronenmikroskopieverfahren rekonstruieren. Durch diese und weitere Experimente werden wir untersuchen, wie Struktur und Funktion dieses Netzwerks durch Erfahrung und Lernen moduliert werden. Die daraus entstehenden neuen Hypothesen werden in weiteren Experimenten überprüft.

 

Wissenschaftlicher und gesellschaftlicher Kontext des Forschungsprojekts

Das Projekt dient der Grundlagenforschung und untersucht komplexe Mechanismen der Informationsverarbeitung im Gehirn. Es wird erwartet, dass das Projekt neue Einsichten in die Informationsverarbeitung und Plastizität von mehrschichtigen Nervenzell-Netzwerken liefert. Dies ist essentiell um zu verstehen, wie höhere Gehirnfunktionen durch Kommunikation zwischen Nervenzellen entstehen. Die Ergebnisse sollten eine Basis zum Verständnis pathophysiologischer Vorgänge liefern und von direkter Relevanz für Systeme künstlicher Intelligenz sein.

Direct link to Lay Summary Last update: 08.02.2018

Responsible applicant and co-applicants

Employees

Associated projects

Number Title Start Funding scheme
130470 Neural Circuit Reconstruction 01.01.2011 Sinergia
135196 Elementary computational functions of inhibitory neuronal circuits 01.10.2011 Project funding (Div. I-III)
152833 Computational functions of inhibitory neuronal circuits 01.10.2014 Project funding (Div. I-III)

Abstract

Background and general aim. Higher neuronal circuits of vertebrates integrate sensory input with previous experience to control intelligent behavior. This integration relies on the interaction between “bottom-up” pathways, which convey sensory information, and “top-down” pathways, which modulate sensory processing based on memory, attention, and other factors. We will mechanistically analyze the interaction between these pathways in the olfactory bulb (OB) which receives bottom-up input from the nose and top-down input from olfactory cortex. Models assume that the interaction between these pathways optimizes information processing based on an individual’s experience by activity-dependent modifications of synaptic connectivity in a multi-layer network. To address key predictions of such models we will take advantage of novel methods for “functional connectomics” in zebrafish. We will determine how top-down feedback is integrated with bottom-up input in the OB, how information is processed in the pathway from the OB to cortex and back, and how these processes are modified by learning. We will train zebrafish in an odor discrimination task, optically measure activity patterns in the OB and its targets, and reconstruct the underlying circuits by volumetric electron microscopy. Top-down inputs will be manipulated by opto- and chemogenetics to study effects on computations and behavior. Specific aims.1.Juvenile development of circuit structure and function. We will analyze the development of top-down projections to the OB and the associated functional consequences. We will test the hypothesis that top-down inputs modulate and refine neuronal computations by a core circuitry that arises early in development. 2.Plasticity and behavioral functions of top-down circuits. We will examine how discrimination learning modifies odor responses in bottom-up and top-down pathways, and how manipulations of top-down input affect neuronal computations in the OB and behavior. These studies address the hypothesis that top-down input to the OB is modified during learning and supports the identification of behaviorally relevant stimuli.3.Topology and specificity of cortical feedback. We will measure odor-evoked activity patterns in trained juvenile fish and reconstruct wiring diagrams of the multisynaptic circuit from the OB to its cortical targets and back. We will analyze structural modifications of intra- and inter-areal circuits underlying olfactory memory and test predictions of theoretical models, including the hypothesis that feedback pathways to the OB contain specific multisynaptic loops. We will analyze the inter-individual variability of wiring diagrams and address the hypothesis that structural variability does not preclude stability of function.Expected value. Exhaustive circuit reconstructions will provide fundamental insights into the topology of wiring diagrams, their inter-individual variability, and the functional consequences. Activity measurements, circuit reconstructions and functional manipulations will provide mechanistic insights into experience-dependent computations such as predictive coding that are of key importance for higher brain functions and in disease.
-