June was a hot month for neural circuit research papers! Check out our list of the neural circuit research studies from last month that really impact our understanding of how neural circuits develop and function in vivo. We gain novel insights into the neural circuits relevant to stress and fear, memory, reward coding, and more.
1. Hippocampal neurogenesis confers stress resilience by inhibiting the ventral dentate gyrus by Christoph Anacker, Victor M. Luna, Gregory S. Stevens, Amira Millette, Ryan Shores, Jessica C. Jimenez, Briana Chen & René Hen. Nature.
They used nVista in vivo calcium imaging to record neuronal activity from large cell populations in the ventral dentate gyrus (vDG) and saw that increased neurogenesis resulted in a decrease in the activity of stress-responsive cells that were active preferentially during attacks or while mice explored anxiogenic environments. Direct silencing of the vDG conferred resilience whereas excitation promoted susceptibility, suggesting that the activity of the vDG may be a key factor in determining individual levels of vulnerability to stress and related psychiatric disorders.
2. Dorsal tegmental dopamine neurons gate associative learning of fear by Florian Groessl, Thomas Munsch, Susanne Meis, Johannes Griessner, Joanna Kaczanowska, Pinelopi Pliota, Dominic Kargl, Sylvia Badurek, Klaus Kraitsy, Arash Rassoulpour, Johannes Zuber, Volkmar Lessmann & Wulf Haubensak. Nature Neuroscience.
By using nVista in vivo calcium imaging, they identified a circuit that reciprocally connects the ventral periaqueductal gray and dorsal raphe region with the central amygdala and that gates fear learning. They found that ventral periaqueductal gray and dorsal raphe dopaminergic (vPdRD) neurons encode a positive prediction error in response to unpredicted shocks and may reshape intra-amygdala connectivity via a dopamine-dependent form of long-term potentiation.
3. Optogenetic editing reveals the hierarchical organization of learned action sequences by Claire E. Geddes, Hao Li, Xin Jin. Cell.
They discovered how learned behaviors are organized and controlled by direct and indirect striatal pathways, offering insight into disorders such as Parkinson's disease or obsessive-compulsive disorder.
4. A dedicated population for reward coding in the hippocampus by Jeffrey L. Gauthier, David W. Tank. Neuron.
They described a novel dedicated population of neurons in two major hippocampal output structures, CA1 and the subiculum, specialized for encoding reward location across environments.
Read more here
5. How diverse retinal functions arise from feedback at the first visual synapse by Antonia Drinnenberg, Felix Franke, Rei K. Morikawa, Josephine Jüttner, Daniel Hillier, Peter Hantz, Andreas Hierlemann, Rava Azeredo da Silveira, Botond Roska. Neuron.
They asked how an interneuron type contributes to the input-output transformations in the mouse retina by chemogenetically perturbing horizontal cells, an interneuron type providing feedback at the first visual synapse, while monitoring the light-driven spiking activity in thousands of ganglion cells, the retinal output neurons. They uncovered six reversible perturbation-induced effects in the response dynamics and response range of ganglion cells. Their combined experimental and theoretical work reveals how a single interneuron type can differentially shape the dynamical properties of distinct output channels of a brain region.
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6. Layer I interneurons sharpen sensory maps during neonatal development by Alicia Che, Rachel Babij, Andrew F. Iannone, Robert N. Fetcho, Monica Ferrer, Conor Liston, Gord Fishell, Natalia V. De Marco García. Neuron.
They showed that activation of 5HT3a serotonin receptor Reelin neurons restricts the activation of upper layer excitatory neurons during sensory stimulation and refines the barrel map in the somatosensory cortex. These results point to an inhibitory role of GABA in the functional and structural establishment of developing somatosensory circuits.
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7. A visual-cue-dependent memory circuit for place navigation by Han Qin, Ling Fu, Bo Hu, Xiang Liao, Jian Lu, Wenjing He, Shanshan Liang, Kuan Zhang, Ruijie Li, Jiwei Yao, Junan Yan, Hao Chen, Hongbo Jia, Benedikt Zott, Arthur Konnerth, Xiaowei Chen. Neuron.
They probed learning-dependent changes in neuronal activity in the medial entorhinal cortex (MEC)-hippocampal circuits by using optic fiber photometry in freely behaving mice. They discovered the experience-dependent induction of a persistent-task-associated (PTA) activity. This PTA activity critically depends on learned visual cues and builds up selectively in the MEC layer II-dentate gyrus, but not in the MEC layer III-CA1 pathway, and its optogenetic suppression disrupts navigation to the target location. The findings suggest that the visual system, the MEC layer II, and the dentate gyrus are essential hubs of a memory circuit for visually guided navigation.
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8. Cocaine inhibition of synaptic transmission in the ventral pallidum Is pathway-specific and mediated by serotonin by Aya Matsui, Veronica A. Alvarez. Cell Reports.
They showed that cocaine increases endogenous serotonin in the ventral pallidum (VP) to suppress synaptic transmission selectively from indirect pathway projections to VP neurons.
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9. The locus coeruleus drives disinhibition in the midline thalamus via a dopaminergic mechanism by B. Sofia Beas, Brandon J. Wright, Miguel Skirzewski, Yan Leng, Jung Ho Hyun, Omar Koita, Nicholas Ringelberg, Hyung-Bae Kwon, Andres Buonanno & Mario A. Penzo. Nature Neuroscience.
They showed that stress exposure drives a rapid and persistent reduction of inhibitory transmission onto projection neurons of the posterior paraventricular nucleus of the thalamus (pPVT). This stress-induced disinhibition of the pPVT was associated with a locus coeruleus-mediated rise in the extracellular concentration of dopamine in the midline thalamus, required the function of dopamine D2 receptors on PVT neurons, and increased sensitivity to stress. Thus, the locus coeruleus is an important modulator of PVT function: by controlling the inhibitory tone of the pPVT, it modulates the excitability of pPVT projection neurons and controls stress responsivity.
10. Brain circuits mediating opposing effects on emotion and pain by You-Qing Cai, Wei Wang, Adriana Paulucci-Holthauzen and Zhizhong Z Pan. Journal of Neuroscience.
Using optogenetics, they demonstrated that the pain signal conveyed through the parabrachial nucleus that relays peripheral pain signals to the central nucleus of amygdala (PBN-CeA) pathway is sufficient to drive negative emotion and that the corticolimbic signal via the basolateral amygdala (BLA)-CeA pathway counteracts the negative emotion, suggesting a top-down brain mechanism for cognitive control of negative emotion under stressful environmental conditions such as pain.