19 posts · 25,295 views
I study olfaction and taste perception at the University of Geneva. As I dive into the literature, I post summaries of interesting papers, and sometimes cover bigger issues in science.
Recording from individual cells in genetically identified populations is the hottest technique in systems neuroscience right now (I am, of course, totally biased since that's what I'm trying to do). To record from identified populations, you first choose a mouse line that expresses Cre driven by a cell-specific marker like D1R. Then you transduce those cells with floxed ChR2 or GCaMP so you can ... Read more »
Betley, J., Xu, S., Cao, Z., Gong, R., Magnus, C., Yu, Y., & Sternson, S. (2015) Neurons for hunger and thirst transmit a negative-valence teaching signal. Nature, 521(7551), 180-185. DOI: 10.1038/nature14416
Chen Y, Lin YC, Kuo TW, & Knight ZA. (2015) Sensory detection of food rapidly modulates arcuate feeding circuits. Cell, 160(5), 829-41. PMID: 25703096
Jennings, J., Ung, R., Resendez, S., Stamatakis, A., Taylor, J., Huang, J., Veleta, K., Kantak, P., Aita, M., Shilling-Scrivo, K.... (2015) Visualizing Hypothalamic Network Dynamics for Appetitive and Consummatory Behaviors. Cell, 160(3), 516-527. DOI: 10.1016/j.cell.2014.12.026
Liu, T., Kong, D., Shah, B., Ye, C., Koda, S., Saunders, A., Ding, J., Yang, Z., Sabatini, B., & Lowell, B. (2012) Fasting Activation of AgRP Neurons Requires NMDA Receptors and Involves Spinogenesis and Increased Excitatory Tone. Neuron, 73(3), 511-522. DOI: 10.1016/j.neuron.2011.11.027
Yang, Y., Atasoy, D., Su, H., & Sternson, S. (2011) Hunger States Switch a Flip-Flop Memory Circuit via a Synaptic AMPK-Dependent Positive Feedback Loop. Cell, 146(6), 992-1003. DOI: 10.1016/j.cell.2011.07.039
I have been growing more interested in genomics, so this quarter I took a
class on new techniques in genomics.* What I learned is that the most important aspect of modern
genomics is cost. Sequencing gets exponentially cheaper every year, which makes
answering old questions less expensive, and opens up new experimental
possibilities. For example for cancer, in the past doctors might have ... Read more »
Lovatt, D., Ruble, B., Lee, J., Dueck, H., Kim, T., Fisher, S., Francis, C., Spaethling, J., Wolf, J., Grady, M.... (2014) Transcriptome in vivo analysis (TIVA) of spatially defined single cells in live tissue. Nature Methods, 11(2), 190-196. DOI: 10.1038/nmeth.2804
Pollen, A., Nowakowski, T., Shuga, J., Wang, X., Leyrat, A., Lui, J., Li, N., Szpankowski, L., Fowler, B., Chen, P.... (2014) Low-coverage single-cell mRNA sequencing reveals cellular heterogeneity and activated signaling pathways in developing cerebral cortex. Nature Biotechnology, 32(10), 1053-1058. DOI: 10.1038/nbt.2967
Two years ago, I wrote a post about the common mistakes I notice in channelrhodopsin papers. Since then, two labs have developed improved photoactivatable chloride channels for inhibition, binary logic has been introduced to neurons, and you can use one vector to photostimulate and record from a neuron type. Beyond those headline advances, though, were some smaller papers that highlight some of ... Read more »
Kravitz, A., Tye, L., & Kreitzer, A. (2012) Distinct roles for direct and indirect pathway striatal neurons in reinforcement. Nature Neuroscience, 15(6), 816-818. DOI: 10.1038/nn.3100
Kravitz AV, Owen SF, & Kreitzer AC. (2013) Optogenetic identification of striatal projection neuron subtypes during in vivo recordings. Brain research, 21-32. PMID: 23178332
The Isaacson lab just published a paper about feedback connections from piriform cortex to the olfactory bulb. To do this, they expressed ChR2 in cortex, then cut slices of the olfactory bulb, patched various cells, and photostimulated the cortical axon terminals. Standard optogenetics in 2013.
They quantified the strength of the cortical feedback onto various cell types, and they found that the... Read more »
McNaughton BL, Barnes CA, & Andersen P. (1981) Synaptic efficacy and EPSP summation in granule cells of rat fascia dentata studied in vitro. Journal of neurophysiology, 46(5), 952-66. PMID: 7299453
While I am no Boyden-level expert in channelrhodopsin, I have photostimulated neurons in the olfactory bulb, and now am trying to use the delightfully named PINP technique to record from specific layers of cortex. Given this rudimentary experience, I am increasingly frustrated by the sloppiness of optogenetic research in good journals. Today I would like to highlight four articles that used ... Read more »
Atallah BV, Bruns W, Carandini M, & Scanziani M. (2012) Parvalbumin-expressing interneurons linearly transform cortical responses to visual stimuli. Neuron, 73(1), 159-70. PMID: 22243754
Kravitz AV, Tye LD, & Kreitzer AC. (2012) Distinct roles for direct and indirect pathway striatal neurons in reinforcement. Nature neuroscience, 15(6), 816-8. PMID: 22544310
Tan KR, Yvon C, Turiault M, Mirzabekov JJ, Doehner J, Labouèbe G, Deisseroth K, Tye KM, & Lüscher C. (2012) GABA neurons of the VTA drive conditioned place aversion. Neuron, 73(6), 1173-83. PMID: 22445344
With my olfaction research ending at Zeno speed, I've started pilot experiments for everyone's favourite sensory modality, taste! The idea is to record from each layer of taste (insular) cortex, and compare the "taste receptive fields" of neurons from each layer. To identify the layer I record from, I'm using channelrhodopsin-aided cell identification: I record extracellulary from random neurons ... Read more »
Lima SQ, Hromádka T, Znamenskiy P, & Zador AM. (2009) PINP: a new method of tagging neuronal populations for identification during in vivo electrophysiological recording. PloS one, 4(7). PMID: 19584920
On a basic level, feeding (viz. eating) is regulated by opponent pathways: for example the hormone leptin is anorexigenic (prevents feeding), whereas cannabinoids are orexigenic (causes feeding); in the lateral hypothalamus, AGRP-expressing neurons are orexigenic, while POMC neurons are anorexigenic. Many of the players in feeding regulation are known, and the current task in the field is tying ... Read more »
This is part 2 in an arbitrarily long series where I review papers from Gilles Laurent's lab.
Last time I looked at four early papers from Laurent's lab, which described the basics of how insect olfaction works. They showed that when you present a locust with an odor, their olfactory centers' LFPs oscillate at 20Hz, and antennal lobe (AL) neurons fire action potentials in sync with the LFP. ... Read more »
Stopfer M, Bhagavan S, Smith BH, & Laurent G. (1997) Impaired odour discrimination on desynchronization of odour-encoding neural assemblies. Nature, 390(6655), 70-4. PMID: 9363891
Stopfer M, Jayaraman V, & Laurent G. (2003) Intensity versus identity coding in an olfactory system. Neuron, 39(6), 991-1004. PMID: 12971898
Like Casablanca on an AFI top 100 list, you knew this was coming: the Laurent lab overview. Gilles Laurent is the forefather the dynamics of olfactory coding, and his neurotree includes descendants like Rainer Friedrich and Rachel Wilson. In the next few posts I'm going to cover the significant papers since he started his lab. Today I will cover results from four papers that initially described ... Read more »
Laurent G, Wehr M, & Davidowitz H. (1996) Temporal representations of odors in an olfactory network. The Journal of neuroscience : the official journal of the Society for Neuroscience, 16(12), 3837-47. PMID: 8656278
MacLeod K, & Laurent G. (1996) Distinct mechanisms for synchronization and temporal patterning of odor-encoding neural assemblies. Science (New York, N.Y.), 274(5289), 976-9. PMID: 8875938
Wehr M, & Laurent G. (1996) Odour encoding by temporal sequences of firing in oscillating neural assemblies. Nature, 384(6605), 162-6. PMID: 8906790
Theoretically, each animal's taste repertoire is determined by the food it eats. For herbivores, the important tastes are sweet and bitter, which lets animals distinguish between calories and poison. For carnivores, they are umami and sour, which help identify whether meat is fresh. Flies, for whatever reason, detect carbonation in water. As omnivores, humans combine the taste repertoires of ... Read more »
Rather than repine about the worst Cell paper I've ever read*, let's cover a new Cell paper from David Anderson's lab. In my past posts on taste, I've covered a lot of the Zuker lab's work on mammalian taste receptors, and other labs' work on how neuromodulators can effect taste receptors. Parallel with the work on mammalian receptors, many taste receptors have been identified in the fly, ... Read more »
Inagaki HK, Ben-Tabou de-Leon S, Wong AM, Jagadish S, Ishimoto H, Barnea G, Kitamoto T, Axel R, & Anderson DJ. (2012) Visualizing Neuromodulation In Vivo: TANGO-Mapping of Dopamine Signaling Reveals Appetite Control of Sugar Sensing. Cell, 148(3), 583-95. PMID: 22304923
It's been too long since I wrote about, you know, actual science. Today I'm going to cover two recent papers from the Rinberg lab, which has been on fire lately.
"Precise" temporal coding in the olfactory bulb
While the core coding strategies used in the visual, auditory, and somatosensory systems are generally well defined, much less is known about coding in olfaction. Many people have imaged... Read more »
The Zuker lab recently reported the existence of taste hotspots in gustatory cortex. I go through the paper, and look at what that means.... Read more »
I haven't done many walkalongs about new papers, so let's review a new paper from Charles Zuker's lab.
First, two pieces of background. There are two diametrically opposed theories of taste coding. The "labeled line" theory states that each taste quality (sweet, salty, bitter, etc.) is encoded by a single cell type, and individual cells respond to single taste qualities. In contrast,... Read more »
Taste receptors on the tongue transduce the chemical information of food into neuronal signals. As of now, people have identified a wide variety of receptors for sweet, sour, salty, bitter, umami, fat, carbonation, and water. Three of the taste qualities - bitter, sweet, and umami - are transduced by G-protein coupled receptors. This is the story of how the sweet and umami receptors were ... Read more »
In the last trek we took, I wrote about two seminal papers that describe taste coding in gustatory cortex. Today I'm going to cover a followup paper which described satiety's effects on gustatory coding.
... Read more »
While the last few walks have covered taste receptors, I'm more interested in the central representation of taste. When you taste something the information is relayed from the taste receptors by three facial nerves to the brainstem (NST), then to the thalamus (VPMpc), and from there to gustatory cortex (GC). The NST also projects to the amygdala and lateral hypothalamus, sending reward and ... Read more »
Katz DB, Simon SA, & Nicolelis MA. (2001) Dynamic and multimodal responses of gustatory cortical neurons in awake rats. The Journal of neuroscience : the official journal of the Society for Neuroscience, 21(12), 4478-89. PMID: 11404435
Katz DB, Simon SA, & Nicolelis MA. (2002) Taste-specific neuronal ensembles in the gustatory cortex of awake rats. The Journal of neuroscience : the official journal of the Society for Neuroscience, 22(5), 1850-7. PMID: 11880514
It's grant writing time here at the Paper Trail, which means reading lots of papers to cite in the background section of the grant. I'm going to cover my favourite paper that I've discovered, which shows that endocannabinoids can directly modulate taste receptors.
More than meets the tongue
Flavour is a tricky perception. It's obviously dominated by how things taste, but also influenced by ... Read more »
A summary of one of the first papers to report the bitter taste receptrs... Read more »
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