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Müllner FE, Roska B. Individual thalamic inhibitory interneurons are functionally specialized toward distinct visual features. Neuron 2024:S0896-6273(24)00408-2. [PMID: 38917805 DOI: 10.1016/j.neuron.2024.06.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2023] [Revised: 03/22/2024] [Accepted: 06/03/2024] [Indexed: 06/27/2024]
Abstract
Inhibitory interneurons in the dorsolateral geniculate nucleus (dLGN) are situated at the first central synapse of the image-forming visual pathway, but little is known about their function. Given their anatomy, they are expected to be multiplexors, integrating many different retinal channels along their dendrites. Here, using targeted single-cell-initiated rabies tracing, we found that mouse dLGN interneurons exhibit a degree of retinal input specialization similar to thalamocortical neurons. Some are anatomically highly specialized, for example, toward motion-selective information. Two-photon calcium imaging performed in vivo revealed that interneurons are also functionally specialized. In mice lacking retinal horizontal direction selectivity, horizontal direction selectivity is reduced in interneurons, suggesting a causal link between input and functional specialization. Functional specialization is not only present at interneuron somata but also extends into their dendrites. Altogether, inhibitory interneurons globally display distinct visual features which reflect their retinal input specialization and are ideally suited to perform feature-selective inhibition.
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Affiliation(s)
- Fiona E Müllner
- Institute of Molecular and Clinical Ophthalmology Basel, 4031 Basel, Switzerland; Department of Ophthalmology, University of Basel, 4031 Basel, Switzerland; Friedrich Miescher Institute for Biomedical Research, 4056 Basel, Switzerland
| | - Botond Roska
- Institute of Molecular and Clinical Ophthalmology Basel, 4031 Basel, Switzerland; Department of Ophthalmology, University of Basel, 4031 Basel, Switzerland.
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Tworig JM, Morrie RD, Bistrong K, Somaiya RD, Hsu S, Liang J, Cornejo KG, Feller MB. Differential Expression Analysis Identifies Candidate Synaptogenic Molecules for Wiring Direction-Selective Circuits in the Retina. J Neurosci 2024; 44:e1461232024. [PMID: 38514178 PMCID: PMC11063823 DOI: 10.1523/jneurosci.1461-23.2024] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2023] [Revised: 02/16/2024] [Accepted: 02/22/2024] [Indexed: 03/23/2024] Open
Abstract
An organizational feature of neural circuits is the specificity of synaptic connections. A striking example is the direction-selective (DS) circuit of the retina. There are multiple subtypes of DS retinal ganglion cells (DSGCs) that prefer motion along one of four preferred directions. This computation is mediated by selective wiring of a single inhibitory interneuron, the starburst amacrine cell (SAC), with each DSGC subtype preferentially receiving input from a subset of SAC processes. We hypothesize that the molecular basis of this wiring is mediated in part by unique expression profiles of DSGC subtypes. To test this, we first performed paired recordings from isolated mouse retinas of both sexes to determine that postnatal day 10 (P10) represents the age at which asymmetric synapses form. Second, we performed RNA sequencing and differential expression analysis on isolated P10 ON-OFF DSGCs tuned for either nasal or ventral motion and identified candidates which may promote direction-specific wiring. We then used a conditional knock-out strategy to test the role of one candidate, the secreted synaptic organizer cerebellin-4 (Cbln4), in the development of DS tuning. Using two-photon calcium imaging, we observed a small deficit in directional tuning among ventral-preferring DSGCs lacking Cbln4, though whole-cell voltage-clamp recordings did not identify a significant change in inhibitory inputs. This suggests that Cbln4 does not function primarily via a cell-autonomous mechanism to instruct wiring of DS circuits. Nevertheless, our transcriptomic analysis identified unique candidate factors for gaining insights into the molecular mechanisms that instruct wiring specificity in the DS circuit.
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Affiliation(s)
- Joshua M Tworig
- Department of Molecular and Cell Biology, University of California Berkeley, Berkeley, California 94720
| | - Ryan D Morrie
- Department of Molecular and Cell Biology, University of California Berkeley, Berkeley, California 94720
| | - Karina Bistrong
- Helen Wills Neuroscience Institute, University of California Berkeley, Berkeley, California 94720
| | - Rachana D Somaiya
- Department of Molecular and Cell Biology, University of California Berkeley, Berkeley, California 94720
| | - Shaw Hsu
- Department of Molecular and Cell Biology, University of California Berkeley, Berkeley, California 94720
| | - Jocelyn Liang
- Department of Molecular and Cell Biology, University of California Berkeley, Berkeley, California 94720
| | - Karen G Cornejo
- Department of Molecular and Cell Biology, University of California Berkeley, Berkeley, California 94720
| | - Marla B Feller
- Department of Molecular and Cell Biology, University of California Berkeley, Berkeley, California 94720
- Helen Wills Neuroscience Institute, University of California Berkeley, Berkeley, California 94720
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Wu S, Wardak A, Khan MM, Chen CH, Regehr WG. Implications of variable synaptic weights for rate and temporal coding of cerebellar outputs. eLife 2024; 13:e89095. [PMID: 38241596 PMCID: PMC10798666 DOI: 10.7554/elife.89095] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2023] [Accepted: 12/27/2023] [Indexed: 01/21/2024] Open
Abstract
Purkinje cell (PC) synapses onto cerebellar nuclei (CbN) neurons allow signals from the cerebellar cortex to influence the rest of the brain. PCs are inhibitory neurons that spontaneously fire at high rates, and many PC inputs are thought to converge onto each CbN neuron to suppress its firing. It has been proposed that PCs convey information using a rate code, a synchrony and timing code, or both. The influence of PCs on CbN neuron firing was primarily examined for the combined effects of many PC inputs with comparable strengths, and the influence of individual PC inputs has not been extensively studied. Here, we find that single PC to CbN synapses are highly variable in size, and using dynamic clamp and modeling we reveal that this has important implications for PC-CbN transmission. Individual PC inputs regulate both the rate and timing of CbN firing. Large PC inputs strongly influence CbN firing rates and transiently eliminate CbN firing for several milliseconds. Remarkably, the refractory period of PCs leads to a brief elevation of CbN firing prior to suppression. Thus, individual PC-CbN synapses are suited to concurrently convey rate codes and generate precisely timed responses in CbN neurons. Either synchronous firing or synchronous pauses of PCs promote CbN neuron firing on rapid time scales for nonuniform inputs, but less effectively than for uniform inputs. This is a secondary consequence of variable input sizes elevating the baseline firing rates of CbN neurons by increasing the variability of the inhibitory conductance. These findings may generalize to other brain regions with highly variable inhibitory synapse sizes.
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Affiliation(s)
- Shuting Wu
- Department of Neurobiology, Harvard Medical SchoolBostonUnited States
| | - Asem Wardak
- Department of Neurobiology, Harvard Medical SchoolBostonUnited States
| | - Mehak M Khan
- Department of Neurobiology, Harvard Medical SchoolBostonUnited States
| | - Christopher H Chen
- Department of Neurobiology, Harvard Medical SchoolBostonUnited States
- Department of Neural and Behavioral Sciences, Pennsylvania State University College of MedicineHersheyUnited States
| | - Wade G Regehr
- Department of Neurobiology, Harvard Medical SchoolBostonUnited States
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Gorin AS, Miao Y, Ahn S, Suresh V, Su Y, Ciftcioglu UM, Sommer FT, Hirsch JA. Local interneurons in the murine visual thalamus have diverse receptive fields and can provide feature selective inhibition to relay cells. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.08.10.549394. [PMID: 37609295 PMCID: PMC10441385 DOI: 10.1101/2023.08.10.549394] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/24/2023]
Abstract
By influencing the type and quality of information that relay cells transmit, local interneurons in thalamus have a powerful impact on cortex. To define the sensory features that these inhibitory neurons encode, we mapped receptive fields of optogenetically identified cells in the murine dorsolateral geniculate nucleus. Although few in number, local interneurons had diverse types of receptive fields, like their counterpart relay cells. This result differs markedly from visual cortex, where inhibitory cells are typically less selective than excitatory cells. To explore how thalamic interneurons might converge on relay cells, we took a computational approach. Using an evolutionary algorithm to search through a library of interneuron models generated from our results, we show that aggregated output from different groups of local interneurons can simulate the inhibitory component of the relay cell's receptive field. Thus, our work provides proof-of-concept that groups of diverse interneurons can supply feature-specific inhibition to relay cells.
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Wu S, Wardak A, Khan MM, Chen CH, Regehr WG. Implications of variable synaptic weights for rate and temporal coding of cerebellar outputs. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.05.25.542308. [PMID: 37292884 PMCID: PMC10245953 DOI: 10.1101/2023.05.25.542308] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Purkinje cell (PC) synapses onto cerebellar nuclei (CbN) neurons convey signals from the cerebellar cortex to the rest of the brain. PCs are inhibitory neurons that spontaneously fire at high rates, and many uniform sized PC inputs are thought to converge onto each CbN neuron to suppress or eliminate firing. Leading theories maintain that PCs encode information using either a rate code, or by synchrony and precise timing. Individual PCs are thought to have limited influence on CbN neuron firing. Here, we find that single PC to CbN synapses are highly variable in size, and using dynamic clamp and modelling we reveal that this has important implications for PC-CbN transmission. Individual PC inputs regulate both the rate and timing of CbN firing. Large PC inputs strongly influence CbN firing rates and transiently eliminate CbN firing for several milliseconds. Remarkably, the refractory period of PCs leads to a brief elevation of CbN firing prior to suppression. Thus, PC-CbN synapses are suited to concurrently convey rate codes, and generate precisely-timed responses in CbN neurons. Variable input sizes also elevate the baseline firing rates of CbN neurons by increasing the variability of the inhibitory conductance. Although this reduces the relative influence of PC synchrony on the firing rate of CbN neurons, synchrony can still have important consequences, because synchronizing even two large inputs can significantly increase CbN neuron firing. These findings may be generalized to other brain regions with highly variable sized synapses.
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Affiliation(s)
- Shuting Wu
- Department of Neurobiology, Harvard Medical School, Boston, MA 02115, USA
| | - Asem Wardak
- Department of Neurobiology, Harvard Medical School, Boston, MA 02115, USA
| | - Mehak M. Khan
- Department of Neurobiology, Harvard Medical School, Boston, MA 02115, USA
| | | | - Wade G. Regehr
- Department of Neurobiology, Harvard Medical School, Boston, MA 02115, USA
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Krizan JM, Kerschensteiner D. Vision: Rules of thalamic mixology. Curr Biol 2022; 32:R779-R781. [PMID: 35882198 PMCID: PMC9888587 DOI: 10.1016/j.cub.2022.06.029] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
The retina generates rich feature representations of the visual world that pass through the thalamus on their way to cortex and perception. A new study reveals rules that govern the separation and combination of retinal inputs in the thalamus.
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Affiliation(s)
- Jenna M Krizan
- John F. Hardesty, MD Department of Ophthalmology and Visual Sciences, Washington University School of Medicine, Saint Louis, MO 63110, USA; Graduate Program in Neuroscience, Washington University School of Medicine, Saint Louis, MO 63110, USA
| | - Daniel Kerschensteiner
- John F. Hardesty, MD Department of Ophthalmology and Visual Sciences, Washington University School of Medicine, Saint Louis, MO 63110, USA; Department of Neuroscience, Washington University School of Medicine, Saint Louis, MO 63110, USA; Department of Biomedical Engineering, Washington University School of Medicine, Saint Louis, MO 63110, USA; Hope Center for Neurological Disorders, Washington University School of Medicine, Saint Louis, MO 63110, USA.
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