# Learning-mediated plasticity in cortical feedback projections to the olfactory bulb

> **NIH NIH K99** · HARVARD UNIVERSITY · 2021 · $128,574

## Abstract

PROJECT SUMMARY/ABSTRACT
 To reliably encode information about the environment, neurons must modify their activity profiles and even
connectivity to accurately interpret complex stimuli. Cortical feedback projections to the olfactory bulb are
uniquely positioned at the interface between detection-based processing that is driven by sensory input and
analytical processing occurring in the piriform cortex. This arrangement makes these projections an ideal target
to study how learning reshapes neuronal activity profiles. I have developed an approach that will allow for a
comprehensive analysis of the axonal activity of principal neurons in the piriform cortex, while mice learn a task
requiring them to identify a specific odor embedded in complex mixtures, thereby providing unique insight into
olfactory scene analysis. My approach will also provide a detailed analysis of the connectivity between cortical
axons and their postsynaptic targets in the olfactory bulb, which will reveal how the olfactory bulb integrates
processed information from the piriform cortex. The hypothesis I will test is that learning reshapes cortico-fugal
input to the olfactory bulb, leading to enhanced odor-scene segmentation through the disambiguation of
olfactory bulb output neuron activity profiles. The outcomes of these studies will provide novel insight to how
the brain to updates its stimulus-encoding scheme from a synthetic to analytical representation of a stimulus
environment. The studies proposed here are novel technically as well as conceptually, and the results will be
broadly applicable to other sensory systems. In Aim 1, I will characterize how learning shapes the activity of
cortical feedback projections to the olfactory bulb. Aim 2 will determine how the synaptic strength and number
of cortical inputs to individual olfactory modules are updated during learning. Finally, Aim 3 will determine how
cortical input shapes the activity profiles of bulbar output neurons. The training phase of this award will be
conducted at Harvard University in the laboratories of Prof. Venkatesh Murthy and Prof. Naoshige Uchida.
Together with my mentors and advisory committee, I have developed a comprehensive training plan that will
provide me with new technical skills and provide professional development that will enable my successful
transition to an independent investigator. The completion of this project will provide the basis for future
experiments related to learning-mediated plasticity in the olfactory system and other sensory systems.

## Key facts

- **NIH application ID:** 10075901
- **Project number:** 5K99DC017754-02
- **Recipient organization:** HARVARD UNIVERSITY
- **Principal Investigator:** Joseph Donald Zak
- **Activity code:** K99 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2021
- **Award amount:** $128,574
- **Award type:** 5
- **Project period:** 2020-01-01 → 2021-12-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10075901

## Citation

> US National Institutes of Health, RePORTER application 10075901, Learning-mediated plasticity in cortical feedback projections to the olfactory bulb (5K99DC017754-02). Retrieved via AI Analytics 2026-05-25 from https://api.ai-analytics.org/grant/nih/10075901. Licensed CC0.

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