Olfactory Object Processing

Olfaction
Neural Circuits
All-Optical Imaging
How the olfactory bulb transforms molecular inputs into concentration-invariant odor representations.

Overview

A central challenge in sensory neuroscience is understanding how the brain constructs stable percepts of objects despite enormous variability in the physical stimulus. For olfaction, the same odor can arrive at vastly different concentrations yet be immediately recognized as the same smell — a feat the brain accomplishes effortlessly.

We study how the olfactory bulb (OB) solves this problem, acting as the first central relay where raw molecular signals from thousands of olfactory sensory neurons are transformed into representations that downstream cortical regions can use for recognition and decision-making.

Figure 1: Olfactory object processing in mammals. Left: odor objects activate a distributed molecular space sampled by sensory neurons. Center: the olfactory bulb integrates input and projects to piriform cortex (PirC), OFC, AON, mPFC, and limbic regions (AM, LEC, HPC). Right: the OB microcircuit showing glomerular layer, mitral/tufted cells, feedback and cortical output pathways.

Scientific Questions

  • How does the OB network achieve concentration invariance in odor coding?
  • What is the role of temporal sequence geometry in odor recognition and generalization?
  • How do feedback projections from piriform cortex and mPFC modulate early olfactory processing?
  • How does the OB interact with hippocampal and limbic circuits during odor-guided behavior?

Approach

We combine large-scale all-optical interrogation with electrophysiology to simultaneously read and write population activity across the olfactory bulb circuit during active odor sampling in head-fixed mice.

Recording

  • Large-scale two-photon calcium imaging (GCaMP)
  • Multi-site silicon probe electrophysiology
  • Fiber photometry for bulk neuromodulator signals

Perturbation

  • Targeted optogenetic stimulation (ChrimsonR, GtACR)
  • Chemogenetic silencing of feedback pathways
  • Closed-loop all-optical stimulus-response mapping

Key Findings

NoteRapid temporal processing underlies concentration invariance

The OB encodes odor identity in the precise temporal sequence of mitral/tufted cell activation within the first sniff. This timing-based code is robust to concentration changes that dramatically alter firing rates, providing a substrate for invariant recognition.

Karadas, M, Gill, JV, Ceballo, S, Shoham, S, Rinberg, D. Nature Neuroscience, 29(5):1109–1121 (2026). DOI 10.1038/s41593-026-02250-y

NoteSequence geometry enables odor generalization

The geometry of population activity trajectories in neural state space predicts perceptual similarity and generalization across odor pairs — linking circuit-level dynamics to behavior.

Gill, JV, Karadas, M, Shoham, S, Rinberg, D. bioRxiv (2026). DOI 10.64898/2026.01.20.700611

Team

This project is led by Mursel Karadas in collaboration with the Rinberg Lab and Shoham Lab at NYU.


Interested in collaborating? Get in touch.