Electrophysiological Representations of Odor Identity Study 2

January 27, 2026 updated by: Christina Zelano, Northwestern University

Electrophysiological Representations of Odor in the Human Brain Study 2

To identify a neural representation of odor identity, it is necessary to dissociate molecular structure from perceptual identity/similarity.

Whether the olfactory system employs a coding scheme in which the similarity between neural features is systematically related to perceptual similarity is unknown. Experiments for this aim will acquire perceptual responses while manipulating perceptual similarity. In Experiment 1A, we will examine features of neural responses during natural behavior of freely naming odors. In Experiment 1B, we will manipulate perceptual similarity with odor metamers and collect perceptual and neural data on each trial. Preliminary data suggest that the earliest, high-frequency components of the piriform response can optimally decode perceptual identity.

Study Overview

Status

Recruiting

Conditions

Intervention / Treatment

Detailed Description

Olfactory perception relies on the brain's ability to extract and represent different features of an odor stimulus.

For example, intensity and identity are fundamental features of the olfactory percept that must be encoded separately for accurate perception; the same odor can be encountered at different strengths. Understanding neural representations of olfactory perceptual features is fundamental to understanding the olfactory system, however the neural correlates of odor intensity and identity are poorly understood in the human brain.

The field of olfaction typically uses chemistry as a proxy for perception and focuses on manipulating physical properties of a stimulus to look for neural correlates. For example, chemical concentration and molecular identity are typically used as proxies for odor intensity and identity. However, the world that animals perceive is not a complete representation of physical reality; it is a product of the particular sensory systems that each species has acquired in the course of evolution. To understand how the brain forms representations of perceptual features of odors, we must identify relationships between features of neural responses and perceptual ratings.

While novel behavioral paradigms in rodents can provide good estimates of perceptual ratings of different features of odors (intensity, identity), humans can directly provide perceptual ratings of different features of an odor. Therefore, human work is necessary to fully understand olfactory perception.

The missing link between neural signatures and perceptual properties of odor is a critical gap in our understanding of odor coding. Here, we will combine human intracranial recordings-including direct neural recordings from human olfactory cortex-with simultaneous delivery of precisely controlled odors of varying intensity/identity and trial-by-trial collection of psychophysical ratings to understand how odors are represented in the human brain. Accurate olfactory psychophysical ratings are a critical part of our proposal. Therefore, we will work with leading experts in human psychophysics at Monel Chemical Senses Center, Dr. Pamela Dalton and Dr. Joel Mainland. As Co-Investigators on this grant, their expertise in human psychophysics will combine with my lab's expertise in human olfactory electrophysiology to provide the field with an understanding of the mappings between olfactory perception and neural codes in the human brain. To identify a neural representation of odor identity, it is necessary to dissociate molecular structure from perceptual identity/similarity.

Whether the olfactory system employs a coding scheme in which the similarity between neural features is systematically related to perceptual similarity is unknown. Experiments for this aim will acquire perceptual responses while manipulating perceptual similarity. In Experiment 1A, we will examine features of neural responses during natural behavior of freely naming odors. In Experiment 1B, we will manipulate perceptual similarity with odor metamers and collect perceptual and neural data on each trial. Preliminary data suggest that the earliest, high-frequency components of the piriform response can optimally decode perceptual identity.

Study Type

Interventional

Enrollment (Estimated)

28

Phase

  • Not Applicable

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Contact

Study Locations

  • United States
    • Illinois
      • Chicago, Illinois, United States, 60611
        • Recruiting
        • Northwestern University
        • Contact:

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Ages Eligible for Study

  • Child
  • Adult
  • Older Adult

Accepts Healthy Volunteers

No

Description

Inclusion Criteria:

  • Ages 12 to 65, english speaker, patients undergoing brain surgery for treatment of medically intractable epilepsy

Exclusion Criteria:

  • screening for history of smell or taste problems

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

  • Primary Purpose: Basic Science
  • Allocation: N/A
  • Interventional Model: Single Group Assignment
  • Masking: None (Open Label)

Arms and Interventions

Participant Group / Arm
Intervention / Treatment
Experimental: Investigating representations of odor identity in human piriform cortex.
Odors will be presented and identified
Behavioral: odor
present odor

What is the study measuring?

Primary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Perceived odor identity
Time Frame: 15 minutes
Odors of different identities will be presented, and we will obtain behavioral perceptual ratings
15 minutes

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

Northwestern University

Investigators

  • Principal Investigator: christina zelano, Northwestern University

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Actual)

March 5, 2025

Primary Completion (Estimated)

March 1, 2028

Study Completion (Estimated)

October 1, 2028

Study Registration Dates

First Submitted

January 27, 2026

First Submitted That Met QC Criteria

January 27, 2026

First Posted (Actual)

February 4, 2026

Study Record Updates

Last Update Posted (Actual)

February 4, 2026

Last Update Submitted That Met QC Criteria

January 27, 2026

Last Verified

January 1, 2026

More Information

Terms related to this study

Additional Relevant MeSH Terms

Other Study ID Numbers

  • 60067814-2

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

NO

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

No

Studies a U.S. FDA-regulated device product

No

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

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