Kevin Franks, PhD

Department of Neurobiology, Duke University

We use the rodent olfactory system to study how the brain forms internal representations of the external world. We analyze small, functional neural circuits in the olfactory bulb and piriform cortex. We record and image odor-evoked responses in vivo, employ optogenetic circuit mapping in vitro, and use olfactory behavioral assays.


Our research is driven by the idea that the nervous systems evolved to solve specific computational problems using relatively simple, small neural circuits, and that these circuits form motifs that are combined and repeated throughout the nervous system.


To understand how these circuits are assembled, how they transform neural information, and how they ultimately guide behavior, we study the representation of odor in the rodent primary olfactory, or piriform cortex. The piriform cortex is a relatively simple, evolutionary ancient, three-layered cortex. Yet, despite its simplicity, circuitry within piriform cortex is thought to support many of the computations required for odor recognition and discrimination, including gain control, pattern separation, and pattern completion. In addition to revealing its role in odor perception, a mechanistic understanding of how this simple circuit solves these common computational problems can reveal general principles of brain function.

The Lab

Shiva Nagappan

Graduate Student

Robin Blazing

Graduate Student

Achint Kumar

Graduate Student

Fernando Santos Valencia


Selected Publications

Single-cell genetic transfection via in vivo whole-cell recording: bridging physiology, genetics and connectomics.
Rancz EA*, Franks KM*, Schwartz, M Schaefer AT, Seeburg P, Margrie TW. (2011) Nature Neuroscience. 14: 527-532. [pdf]


Pattern recovery by recurrent circuits in piriform cortex.
Bolding KA, Nagappan S, Han, BX, Wang F & Franks KM. (2019) bioRxiv 10.1101/694331. [bioRxiv]


Recurrent cortical circuits implement concentration-invariant odor coding.
Bolding KA & Franks KM. (2018) Science 361: eaat6904. [pdf]


A transformation from temporal to ensemble coding in a model of piriform cortex.
Stern M, Bolding KA, Abbott LF & Franks KM. (2018) eLife 10.7554/eLife.34831. [pdf]

Learning: Plasticity without Stabilization in Olfactory Cortex.
Nagappan S & Franks KM. (2018) Curr. Biol. 28: R23-R25. [pdf]


Complementary codes for odor identity and odor intensity in olfactory cortex.
Bolding KA & Franks KM. (2017) eLife 10.7554/eLife.22630. [pdf]


Odor identity coding by distributed ensembles of neurons in the mouse olfactory cortex.
Roland B, Deneux T, Franks KM, Bathellier B, Fleischmann A. (2017) eLife 10.7554/eLife.26337. [pdf]


Massive normalization of olfactory bulb output in mice with a “monoclonal nose”.
Roland B, Jordan R, Sosulski DL, Diodato A, Fukunaga I, Wickersham I, Franks KM, Schaefer AT & Fleischmann A. (2016) eLife 10:7554/eLife.16335. [pdf]


I Want It All and I Want It Now: How a Neural Circuit Encodes Odor with Speed and Accuracy. Franks KM. (2015) Neuron. 88: 852-4. [pdf]


Multi-step signaling from sensory neurons onto olfactory bulb mitral cells. Gire DH*, Franks KM*, Zak JD, Tanaka KF, Whitesell JD, Mulligan AA, Hen R, Schoppa NE. (2012) J. Neurosci. 32: 2964-75. [pdf]

Recurrent circuitry dynamically shapes the activation of piriform cortex.
Franks KM, Russo MJ, Sosulski DL, Mulligan AA, Siegelbaum SA, Axel, R. (2011) . Neuron. 72: 49-56. [pdf]

Mice with a "monoclonal nose": perturbations in an olfactory map impair odor discrimination.
Fleischmann A, Shykind BM, Sosulski DL, Franks KM, Glinka ME, Mei DF, Sun Y, Kirkland J, Mendelsohn M, Albers MW, Axel R. (2008) Neuron. 60: 1068-81. [pdf]


Strong single-fiber sensory inputs to olfactory cortex: implications for olfactory coding.
Franks KM, Isaacson JS. (2006) Neuron. 49: 357-363. [pdf]


Synapse specific downregulation of NMDA receptors by early experience: a critical period for plasticity of sensory input to olfactory cortex.
Franks KM, Isaacson JS. (2005) Neuron. 47: 101-114. [pdf]

* denotes equal authorship


A BRAIN Initiative Research Team

Funded by NINDS U19NS112953

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