Here are the original research articles published in September 2018 that make our must-read list from across journals. We hope this list will help guide discovery of papers relevant to the neural circuit research community.
1. Touch and tactile neuropathic pain sensitivity are set by corticospinal projections by Yuanyuan Liu, Alban Latremoliere, Xinjian Li, Zicong Zhang, Mengying Chen, Xuhua Wang, Chao Fang, Junjie Zhu, Chloe Alexandre, Zhongyang Gao, Bo Chen, Xin Ding, Jin-Yong Zhou, Yiming Zhang, Chinfei Chen, Kuan Hong Wang, Clifford J. Woolf & Zhigang He. Nature.
They used Inscopix nVista technology to examine direct cortical modulation of normal & pathological tactile sensory processing in the spinal cord, opening opportunities for neuropathic pain treatments. The study points to a mechanism by which the mind can control pain sensitivity. Pretty cool.
2. A gut-brain neural circuit for nutrient sensory transduction by Melanie Maya Kaelberer, Kelly L. Buchanan, Marguerita E. Klein, Bradley B. Barth, Marcia M. Montoya, Xiling Shen, Diego V. Bohórquez. Science.
The human gut is lined with over 100 million nerve cells. They determined whether gut cells and neurons communicate via synapses by injecting a fluorescent rabies virus into the colons of mice to find out whether their neuronal counterparts would become fluorescent too―which they did. The partner neurons were discovered to be vagal neurons, and newly named neuropod cells of the gut were shown to stretch out and interact with them to form synaptic connections.
3. A Neural Circuit for Gut-Induced Reward by Wenfei Han, Luis A. Tellez, Matthew H. Perkins, Isaac O. Perez, Taoran Qu, Jozelia Ferreira, Tatiana L. Ferreira, Daniele Quinn, Zhong-Wu Liu, Xiao-Bing Gao, Melanie M. Kaelberer, Diego V. Bohórquez, Sara J. Shammah-Lagnado, Guillaume de Lartigue, Ivan E. de Araujo. Cell.
They used optogenetics to stimulate sensory neurons linked to the gut, which produced reward sensations that mice worked hard to repeat. The stimulation also increased dopamine levels in the brains of rodents.
4. Functional modulation of primary visual cortex by the superior colliculus in the mouse by Mehran Ahmadlou, Larry S. Zweifel & J. Alexander Heimel. Nature Communications.
They examined the influence of the superior colliculus (SC) on visual responses in primary visual cortex (V1) and found that optogenetically silencing superior colliculus reduced response in V1 to optimal stimuli. Surprisingly, this effect was not via the strong SC to lateral posterior pathway, but via the anatomically smaller tectogeniculate pathway. A size-independent gain modulation of the dLGN by the superior colliculus is transformed into a size-dependent gain modulation in V1.
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5. Dopamine neurons projecting to the posterior striatum reinforce avoidance of threatening stimuli by William Menegas, Korleki Akiti, Ryunosuke Amo, Naoshige Uchida & Mitsuko Watabe-Uchida. Nature Neuroscience.
They demonstrate a role for midbrain dopamine neurons projecting to the tail of the striatum in encoding stimulus novelty and threat avoidance, but not reward value.
6. Recurrent circuits within medial entorhinal cortex superficial layers support grid cell firing by Ipshita Zutshi, Maylin L. Fu, Varoth Lilascharoen, Jill K. Leutgeb, Byung Kook Lim & Stefan Leutgeb. Nature Communications.
They record neuronal activity in medial entorhinal cortex (EC) layers II and III and optogenetically perturb locally projecting layer II pyramidal cells. They find that sharp head direction (HD) cells are embedded in a separate mEC sub-network from broad HD cells, speed cells, and grid cells. Furthermore, grid tuning is not only dependent on local processing but also rapidly updated by HD, speed, or other afferent inputs to mEC.
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7. Restoring wild-type-like CA1 network dynamics and behavior during adulthood in a mouse model of schizophrenia by Thomas Marissal, Rodrigo F. Salazar, Cristina Bertollini, Sophie Mutel, Mathias De Roo, Ivan Rodriguez, Dominique Müller & Alan Carleton. Nature Neuroscience.
Rescuing parvalbumin interneuron excitability with pharmacological or chemogenetic approaches was sufficient to restore wild-type-like CA1 network dynamics and hippocampal-dependent behavior during adulthood in an animal model of the human 22q11 deletion syndrome, the mutation that represents the highest genetic risk of developing schizophrenia.
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8. Recurrent cortical circuits implement concentration-invariant odor coding by KEVIN A. BOLDING, KEVIN M. FRANKS. Science.
Editor summary: We still don’t know how odors retain their identities over a range of concentrations. Working in mice, Bolding and Franks simultaneously recorded spiking activity from neurons in the olfactory bulb and piriform cortex, two important brain regions for olfaction. Odor information was transformed from a representation that was highly concentration dependent in the olfactory bulb to a representation that was largely concentration invariant in the piriform cortex. The underlying mechanism involves a “winner-takes-all” lateral inhibition. In the collateral network of the piriform cortex, the principal cells responded promptly to output from the olfactory bulb, and recurrent inhibition curtailed the intensity dependence of the signal.
9. A Map-like Micro-Organization of Grid Cells in the Medial Entorhinal Cortex by Yi Gu, Sam Lewallen, Amina A. Kinkhabwala, Cristina Domnisoru, Kijung Yoon, Jeffrey L. Gauthier, Ila R. Fiete, David W. Tank. Cell.
10. Learning-Related Plasticity in Dendrite-Targeting Layer 1 Interneurons by Elisabeth Abs, Rogier B. Poorthuis, Daniella Apelblat, Karzan Muhammad, M. Belen Pardi, Leona Enke, Dahlia Kushinsky, De-Lin Pu, Max Ferdinand Eizinger, Karl-Klaus Conzelmann, Ivo Spiegel, Johannes J. Letzkus. Neuron.
Using Neuron-Derived Neurotrophic Factor (NDNF) as a selective marker of L1 interneurons (INs) and in vivo 2-photon calcium imaging, electrophysiology, viral tracing, optogenetics, and associative memory, they “find that L1 NDNF-INs mediate a prolonged form of inhibition in distal pyramidal neuron dendrites that correlates with the strength of the memory trace. Conversely, inhibition from Martinotti cells remains unchanged after conditioning but in turn tightly controls sensory responses in NDNF-INs. These results define a genetically addressable form of dendritic inhibition that is highly experience dependent and indicate that in addition to disinhibition, salient stimuli are encoded at elevated levels of distal dendritic inhibition.”
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11. Fear extinction reverses dendritic spine formation induced by fear conditioning in the mouse auditory cortex by Cora Sau Wan Lai, Avital Adler, and Wen-Biao Gan. PNAS.
Whether learning-induced changes in neuronal circuits are inhibited or erased during the process of unlearning remains unclear. In this study, we examined the impact of auditory-cued fear conditioning and extinction on the remodeling of synaptic connections in the living mouse auditory cortex. We found that fear conditioning leads to cue-specific formation of new postsynaptic dendritic spines, whereas fear extinction preferentially eliminates these new spines in a cue-specific manner. Our findings suggest that learning-related changes of synaptic connections in the cortex are at least partially reversed after unlearning.”
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12. Hippocampal-evoked feed-forward inhibition in the nucleus accumbens by Samantha L. Scudder, Corey Baimel, Emma E. Macdonald and Adam G. Carter. Journal of Neuroscience.
Given the importance of the nucleus accumbens (NAc) in reward learning and drug-seeking behaviors, it is critical to understand what controls the activity of cells in this region. While excitatory inputs to projection neurons in the NAc have been identified, it is unclear how the local inhibitory network becomes engaged. Here, we identify a sparse population of interneurons responsible for feed-forward inhibition evoked by ventral hippocampal input and characterize their connections within the NAc. We also demonstrate that the balance of excitation and inhibition that projection neurons experience is altered by exposure to cocaine. Together, this work provides insight into the fundamental circuitry of this region as well as the effects of drugs of abuse.”
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13. Light Affects Mood and Learning through Distinct Retina-Brain Pathways by Diego Carlos Fernandez, P. Michelle Fogerson, Lorenzo Lazzerini Ospri, Michael B. Thomsen, Robert M. Layne, Daniel Severin, Jesse Zhan, Joshua H. Singer, Alfredo Kirkwood, Haiqing Zhao, David M. Berson, Samer Hattar. Cell.
14. Dynamics and functional role of dopaminergic neurons in the ventral tegmental area during itch processing by Lei Yuan, Tong-Yu Liang, Juan Deng and Yan-Gang Sun. Journal of Neuroscience.
Itchiness is an unpleasant sensation that evokes a scratching response for relief. However, the neural mechanism underlying the modulation of itch-evoked scratching in the brain remains elusive. Here, by combining fiber photometry, extracellular recording and optogenetic manipulation, we show that the dopaminergic neurons in the ventral tegmental area play a modulatory role in itch-evoked scratching behavior. These results reveal a potential target for suppressing excessive scratching responses in patients with chronic itch.”