Scholars@Duke
Kevin M. Franks

Kevin M. Franks

Associate Professor of Neurobiology
Neurobiology
franks@neuro.duke.edu
Box 3209, Durham, NC 27710
Bryan Research Building, 311 Research Drive Room 401D, Durham, NC 27710

Selected Publications

Distinct Neural Representations of Hunger and Thirst in Neonatal Mice before the Emergence of Food- and Water-seeking Behaviors.

Journal Article bioRxiv · February 13, 2025 Hunger and thirst are two fundamental drives for maintaining homeostasis and elicit distinct food- and water-seeking behaviors essential for survival. For neonatal mammals, however, both hunger and thirst are sated by consuming milk from their mother. Whil ... Full text Link to item Cite

Embryonically active piriform cortex neurons promote intracortical recurrent connectivity during development.

Journal Article Neuron · September 4, 2024 Neuronal activity plays a critical role in the maturation of circuits that propagate sensory information into the brain. How widely does early activity regulate circuit maturation across the developing brain? Here, we used targeted recombination in active ... Full text Link to item Cite

The spiking output of the mouse olfactory bulb encodes large-scale temporal features of natural odor environments.

Journal Article bioRxiv · July 1, 2024 In natural odor environments, odor travels in plumes. Odor concentration dynamics change in characteristic ways across the width and length of a plume. Thus, spatiotemporal dynamics of plumes have informative features for animals navigating to an odor sour ... Full text Open Access Link to item Cite

Neuroscience: Seq-ing maps in the olfactory cortex.

Journal Article Curr Biol · April 10, 2023 Many cortical brain regions are spatially organized to optimize sensory representation. Such topographic maps have so far been elusive in the olfactory cortex. A high-throughput tracing study reveals that the neural circuits connecting olfactory regions ar ... Full text Link to item Cite

Electrophysiological Recordings from Identified Cell Types in the Olfactory Cortex of Awake Mice.

Journal Article Methods Mol Biol · 2023 Neural circuits consist of a myriad of distinct cell types, each with specific intrinsic properties and patterns of synaptic connectivity, which transform neural input and convey this information to downstream targets. Understanding how different features ... Full text Link to item Cite

Parallel processing by distinct classes of principal neurons in the olfactory cortex.

Journal Article Elife · December 16, 2021 Understanding how distinct neuron types in a neural circuit process and propagate information is essential for understanding what the circuit does and how it does it. The olfactory (piriform, PCx) cortex contains two main types of principal neurons, semilu ... Full text Open Access Link to item Cite

Chronic loss of inhibition in piriform cortex following brief, daily optogenetic stimulation.

Journal Article Cell Rep · April 20, 2021 It is well established that seizures beget seizures, yet the cellular processes that underlie progressive epileptogenesis remain unclear. Here, we use optogenetics to briefly activate targeted populations of mouse piriform cortex (PCx) principal neurons in ... Full text Link to item Cite

Synaptic Organization of Anterior Olfactory Nucleus Inputs to Piriform Cortex.

Journal Article J Neurosci · December 2, 2020 Odors activate distributed ensembles of neurons within the piriform cortex, forming cortical representations of odor thought to be essential to olfactory learning and behaviors. This odor response is driven by direct input from the olfactory bulb, but is a ... Full text Link to item Cite

Neuroscience: Illuminating Principles of Odor Coding.

Journal Article Curr Biol · October 19, 2020 Neuroscientists still are not sure what makes any two odors smell alike. A new study uses light to manipulate the sensory cells in our nose that respond to odors and reveals that both the timing and identity of activated cells influence odor perception. ... Full text Link to item Cite

Odor coding in piriform cortex: mechanistic insights into distributed coding.

Journal Article Curr Opin Neurobiol · October 2020 Olfaction facilitates a large variety of animal behaviors such as feeding, mating, and communication. Recent work has begun to reveal the logic of odor transformations that occur throughout the olfactory system to form the odor percept. In this review, we ... Full text Link to item Cite

Author Correction: Structure and flexibility in cortical representations of odour space.

Journal Article Nature · August 2020 An amendment to this paper has been published and can be accessed via a link at the top of the paper. ... Full text Link to item Cite

Recurrent circuitry is required to stabilize piriform cortex odor representations across brain states.

Journal Article Elife · July 14, 2020 Pattern completion, or the ability to retrieve stable neural activity patterns from noisy or partial cues, is a fundamental feature of memory. Theoretical studies indicate that recurrently connected auto-associative or discrete attractor networks can perfo ... Full text Open Access Link to item Cite

Structure and flexibility in cortical representations of odour space.

Journal Article Nature · July 2020 The cortex organizes sensory information to enable discrimination and generalization1-4. As systematic representations of chemical odour space have not yet been described in the olfactory cortex, it remains unclear how odour relationships are encoded to pl ... Full text Open Access Link to item Cite

Th17 lymphocytes drive vascular and neuronal deficits in a mouse model of postinfectious autoimmune encephalitis.

Journal Article Proc Natl Acad Sci U S A · March 24, 2020 Antibodies against neuronal receptors and synaptic proteins are associated with a group of ill-defined central nervous system (CNS) autoimmune diseases termed autoimmune encephalitides (AE), which are characterized by abrupt onset of seizures and/or moveme ... Full text Link to item Cite

Recurrent cortical circuits implement concentration-invariant odor coding.

Journal Article Science · September 14, 2018 Animals rely on olfaction to find food, attract mates, and avoid predators. To support these behaviors, they must be able to identify odors across different odorant concentrations. The neural circuit operations that implement this concentration invariance ... Full text Link to item Cite

A transformation from temporal to ensemble coding in a model of piriform cortex.

Journal Article Elife · March 29, 2018 Different coding strategies are used to represent odor information at various stages of the mammalian olfactory system. A temporal latency code represents odor identity in olfactory bulb (OB), but this temporal information is discarded in piriform cortex ( ... Full text Link to item Cite

Learning: Plasticity without Stabilization in Olfactory Cortex.

Journal Article Curr Biol · January 8, 2018 A new study reports unsupervised, experience-dependent reorganization, but not stabilization, of neural odor representations in the zebrafish olfactory system. ... Full text Link to item Cite

Odor identity coding by distributed ensembles of neurons in the mouse olfactory cortex.

Journal Article Elife · May 10, 2017 Olfactory perception and behaviors critically depend on the ability to identify an odor across a wide range of concentrations. Here, we use calcium imaging to determine how odor identity is encoded in olfactory cortex. We find that, despite considerable tr ... Full text Link to item Cite

Complementary codes for odor identity and intensity in olfactory cortex.

Journal Article Elife · April 5, 2017 The ability to represent both stimulus identity and intensity is fundamental for perception. Using large-scale population recordings in awake mice, we find distinct coding strategies facilitate non-interfering representations of odor identity and intensity ... Full text Link to item Cite

Massive normalization of olfactory bulb output in mice with a 'monoclonal nose'.

Journal Article Elife · May 13, 2016 Perturbations in neural circuits can provide mechanistic understanding of the neural correlates of behavior. In M71 transgenic mice with a "monoclonal nose", glomerular input patterns in the olfactory bulb are massively perturbed and olfactory behaviors ar ... Full text Link to item Cite

I Want It All and I Want It Now: How a Neural Circuit Encodes Odor with Speed and Accuracy.

Journal Article Neuron · December 2, 2015 A study by Jeanne and Wilson (2015) describes a circuit and determines the distinct neural circuit mechanisms that allow a signal to be represented with both speed and accuracy in the Drosophila olfactory system. ... Full text Link to item Cite

Mitral cells in the olfactory bulb are mainly excited through a multistep signaling path.

Journal Article J Neurosci · February 29, 2012 Within the olfactory system, information flow from the periphery onto output mitral cells (MCs) of the olfactory bulb (OB) has been thought to be mediated by direct synaptic inputs from olfactory sensory neurons (OSNs). Here, we performed patch-clamp measu ... Full text Link to item Cite

Recurrent circuitry dynamically shapes the activation of piriform cortex.

Journal Article Neuron · October 6, 2011 In the piriform cortex, individual odorants activate a unique ensemble of neurons that are distributed without discernable spatial order. Piriform neurons receive convergent excitatory inputs from random collections of olfactory bulb glomeruli. Pyramidal c ... Full text Link to item Cite

Transfection via whole-cell recording in vivo: bridging single-cell physiology, genetics and connectomics.

Journal Article Nat Neurosci · April 2011 Single-cell genetic manipulation is expected to substantially advance the field of systems neuroscience. However, existing gene delivery techniques do not allow researchers to electrophysiologically characterize cells and to thereby establish an experiment ... Full text Link to item Cite

NGF is essential for hippocampal plasticity and learning.

Journal Article J Neurosci · September 2, 2009 Nerve growth factor (NGF) is produced in the hippocampus throughout life and is retrogradely trafficked to septal cholinergic neurons, providing a potential mechanism for modulating cholinergic inputs and, thereby, hippocampal plasticity. To explore NGF mo ... Full text Link to item Cite

Mice with a "monoclonal nose": perturbations in an olfactory map impair odor discrimination.

Journal Article Neuron · December 26, 2008 We have altered the neural representation of odors in the brain by generating a mouse with a "monoclonal nose" in which greater than 95% of the sensory neurons express a single odorant receptor, M71. As a consequence, the frequency of sensory neurons expre ... Full text Link to item Cite

Calmodulin activation by calcium transients in the postsynaptic density of dendritic spines.

Journal Article PLoS One · April 30, 2008 The entry of calcium into dendritic spines can trigger a sequence of biochemical reactions that begins with the activation of calmodulin (CaM) and ends with long-term changes to synaptic strengths. The degree of activation of CaM can depend on highly local ... Full text Link to item Cite

Strong single-fiber sensory inputs to olfactory cortex: implications for olfactory coding.

Journal Article Neuron · February 2, 2006 Olfactory information is first encoded in a combinatorial fashion by olfactory bulb glomeruli, which individually represent distinct chemical features of odors. This information is then transmitted to piriform (olfactory) cortex, via axons of olfactory bul ... Full text Link to item Cite

Synapse-specific downregulation of NMDA receptors by early experience: a critical period for plasticity of sensory input to olfactory cortex.

Journal Article Neuron · July 7, 2005 Olfaction is required at birth for survival; however, little is known about the maturation of olfactory cortical circuits. Here we show that in vivo sensory experience mediates the development of excitatory transmission in pyramidal neurons of rat olfactor ... Full text Link to item Cite

Independent sources of quantal variability at single glutamatergic synapses.

Journal Article J Neurosci · April 15, 2003 Variability in the size of single postsynaptic responses is a feature of most central neurons, although the source of this variability is not completely understood. The dominant source of variability could be either intersynaptic or intrasynaptic. To quant ... Full text Link to item Cite

Complexity of calcium signaling in synaptic spines.

Journal Article Bioessays · December 2002 Long-term potentiation and long-term depression are thought to be cellular mechanisms contributing to learning and memory. Although the physiological phenomena have been well characterized, little consensus of their underlying molecular mechanisms has emer ... Full text Link to item Cite

A Monte Carlo model reveals independent signaling at central glutamatergic synapses.

Journal Article Biophys J · November 2002 We have developed a biophysically realistic model of receptor activation at an idealized central glutamatergic synapse that uses Monte Carlo techniques to simulate the stochastic nature of transmission following release of a single synaptic vesicle. For th ... Full text Link to item Cite

An MCell model of calcium dynamics and frequency-dependence of calmodulin activation in dendritic spines

Journal Article Neurocomputing · June 1, 2001 Pairing action potentials in synaptically coupled cortical pyramidal cells induces LTP in a frequency-dependent manner (H. Markram et al., Science 275 (1997) 213). Using Mcell, which simulated the 3D geometry of the spine and the diffusion and binding of C ... Full text Cite

Synaptic plasticity in morphologically identified CA1 stratum radiatum interneurons and giant projection cells.

Journal Article Hippocampus · 2000 Long-term potentiation (LTP) of synaptic efficacy was examined in interneurons and giant cells in the stratum radiatum region of the hippocampal CA1 subfield. Cells were visually selected using differential interference contrast (DIC) optics and filled wit ... Full text Link to item Cite