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Suthard RL, Senne RA, Buzharsky MD, Diep AH, Pyo AY, Ramirez S. Engram reactivation mimics cellular signatures of fear. Cell Rep 2024; 43:113850. [PMID: 38401120 DOI: 10.1016/j.celrep.2024.113850] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2023] [Revised: 01/30/2024] [Accepted: 02/07/2024] [Indexed: 02/26/2024] Open
Abstract
Engrams, or the physical substrate of memory, recruit heterogeneous cell types. Targeted reactivation of neurons processing discrete memories drives the behavioral expression of memory, though the underlying landscape of recruited cells and their real-time responses remain elusive. To understand how artificial stimulation of fear affects intra-hippocampal neuron-astrocyte dynamics as well as their behavioral consequences, we express channelrhodopsin-2 in an activity-dependent manner within dentate gyrus neurons while recording both cell types with fiber photometry in hippocampal ventral CA1 across learning and memory. Both cell types exhibit shock responsiveness, with astrocytic calcium events uniquely modulated by fear conditioning. Optogenetic stimulation of a hippocampus-mediated engram recapitulates coordinated calcium signatures time locked to freezing, mirroring those observed during natural fear memory recall. Our findings reveal cell-type-specific dynamics in the hippocampus during freezing behavior, emphasizing neuronal-astrocytic coupling as a shared mechanism enabling both natural and artificially induced memory retrieval and the behavioral expression of fear.
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Affiliation(s)
- Rebecca L Suthard
- Graduate Program for Neuroscience, Boston University, Boston, MA 02215, USA; Department of Psychological and Brain Sciences, The Center for Systems Neuroscience, Neurophotonics Center, and Photonics Center, Boston University, Boston, MA 02215, USA
| | - Ryan A Senne
- Graduate Program for Neuroscience, Boston University, Boston, MA 02215, USA; Department of Psychological and Brain Sciences, The Center for Systems Neuroscience, Neurophotonics Center, and Photonics Center, Boston University, Boston, MA 02215, USA
| | - Michelle D Buzharsky
- Department of Psychological and Brain Sciences, The Center for Systems Neuroscience, Neurophotonics Center, and Photonics Center, Boston University, Boston, MA 02215, USA
| | - Anh H Diep
- Department of Psychological and Brain Sciences, The Center for Systems Neuroscience, Neurophotonics Center, and Photonics Center, Boston University, Boston, MA 02215, USA
| | - Angela Y Pyo
- Department of Psychological and Brain Sciences, The Center for Systems Neuroscience, Neurophotonics Center, and Photonics Center, Boston University, Boston, MA 02215, USA
| | - Steve Ramirez
- Department of Biomedical Engineering, Boston University, Boston, MA 02215, USA; Department of Psychological and Brain Sciences, The Center for Systems Neuroscience, Neurophotonics Center, and Photonics Center, Boston University, Boston, MA 02215, USA.
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Dorst KE, Senne RA, Diep AH, de Boer AR, Suthard RL, Leblanc H, Ruesch EA, Pyo AY, Skelton S, Carstensen LC, Malmberg S, McKissick OP, Bladon JH, Ramirez S. Hippocampal Engrams Generate Variable Behavioral Responses and Brain-Wide Network States. J Neurosci 2024; 44:e0340232023. [PMID: 38050098 PMCID: PMC10860633 DOI: 10.1523/jneurosci.0340-23.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2023] [Revised: 10/31/2023] [Accepted: 11/13/2023] [Indexed: 12/06/2023] Open
Abstract
Freezing is a defensive behavior commonly examined during hippocampal-mediated fear engram reactivation. How these cellular populations engage the brain and modulate freezing across varying environmental demands is unclear. To address this, we optogenetically reactivated a fear engram in the dentate gyrus subregion of the hippocampus across three distinct contexts in male mice. We found that there were differential amounts of light-induced freezing depending on the size of the context in which reactivation occurred: mice demonstrated robust light-induced freezing in the most spatially restricted of the three contexts but not in the largest. We then utilized graph theoretical analyses to identify brain-wide alterations in cFos expression during engram reactivation across the smallest and largest contexts. Our manipulations induced positive interregional cFos correlations that were not observed in control conditions. Additionally, regions spanning putative "fear" and "defense" systems were recruited as hub regions in engram reactivation networks. Lastly, we compared the network generated from engram reactivation in the small context with a natural fear memory retrieval network. Here, we found shared characteristics such as modular composition and hub regions. By identifying and manipulating the circuits supporting memory function, as well as their corresponding brain-wide activity patterns, it is thereby possible to resolve systems-level biological mechanisms mediating memory's capacity to modulate behavioral states.
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Affiliation(s)
- Kaitlyn E Dorst
- Department of Psychological and Brain Sciences, Boston University, Boston 02215, Massachusetts
- Graduate Program for Neuroscience, Boston University, Boston 02215, Massachusetts
| | - Ryan A Senne
- Department of Psychological and Brain Sciences, Boston University, Boston 02215, Massachusetts
- Graduate Program for Neuroscience, Boston University, Boston 02215, Massachusetts
| | - Anh H Diep
- Department of Psychological and Brain Sciences, Boston University, Boston 02215, Massachusetts
| | - Antje R de Boer
- Department of Psychological and Brain Sciences, Boston University, Boston 02215, Massachusetts
| | - Rebecca L Suthard
- Department of Psychological and Brain Sciences, Boston University, Boston 02215, Massachusetts
- Graduate Program for Neuroscience, Boston University, Boston 02215, Massachusetts
| | - Heloise Leblanc
- Department of Psychological and Brain Sciences, Boston University, Boston 02215, Massachusetts
- Graduate Program for Neuroscience, Boston University, Boston 02215, Massachusetts
| | - Evan A Ruesch
- Department of Psychological and Brain Sciences, Boston University, Boston 02215, Massachusetts
| | - Angela Y Pyo
- Department of Psychological and Brain Sciences, Boston University, Boston 02215, Massachusetts
| | - Sara Skelton
- Department of Psychological and Brain Sciences, Boston University, Boston 02215, Massachusetts
| | - Lucas C Carstensen
- Department of Psychological and Brain Sciences, Boston University, Boston 02215, Massachusetts
- Graduate Program for Neuroscience, Boston University, Boston 02215, Massachusetts
| | - Samantha Malmberg
- Department of Psychological and Brain Sciences, Boston University, Boston 02215, Massachusetts
- Graduate Program for Neuroscience, Boston University, Boston 02215, Massachusetts
| | - Olivia P McKissick
- Department of Psychological and Brain Sciences, Boston University, Boston 02215, Massachusetts
| | - John H Bladon
- Department of Psychological and Brain Sciences, Boston University, Boston 02215, Massachusetts
| | - Steve Ramirez
- Department of Psychological and Brain Sciences, Boston University, Boston 02215, Massachusetts
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Suthard RL, Senne RA, Buzharsky MD, Pyo AY, Dorst KE, Diep AH, Cole RH, Ramirez S. Basolateral Amygdala Astrocytes Are Engaged by the Acquisition and Expression of a Contextual Fear Memory. J Neurosci 2023; 43:4997-5013. [PMID: 37268419 PMCID: PMC10324998 DOI: 10.1523/jneurosci.1775-22.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2022] [Revised: 05/11/2023] [Accepted: 05/18/2023] [Indexed: 06/04/2023] Open
Abstract
Astrocytes are key cellular regulators within the brain. The basolateral amygdala (BLA) is implicated in fear memory processing, yet most research has entirely focused on neuronal mechanisms, despite a significant body of work implicating astrocytes in learning and memory. In the present study, we used in vivo fiber photometry in C57BL/6J male mice to record from amygdalar astrocytes across fear learning, recall, and three separate periods of extinction. We found that BLA astrocytes robustly responded to foot shock during acquisition, their activity remained remarkably elevated across days in comparison to unshocked control animals, and their increased activity persisted throughout extinction. Further, we found that astrocytes responded to the initiation and termination of freezing bouts during contextual fear conditioning and recall, and this behavior-locked pattern of activity did not persist throughout the extinction sessions. Importantly, astrocytes do not display these changes while exploring a novel context, suggesting that these observations are specific to the original fear-associated environment. Chemogenetic inhibition of fear ensembles in the BLA did not affect freezing behavior or astrocytic calcium dynamics. Overall, our work presents a real-time role for amygdalar astrocytes in fear processing and provides new insight into the emerging role of these cells in cognition and behavior.SIGNIFICANCE STATEMENT We show that basolateral amygdala astrocytes are robustly responsive to negative experiences, like shock, and display changed calcium activity patterns through fear learning and memory. Additionally, astrocytic calcium responses become time locked to the initiation and termination of freezing behavior during fear learning and recall. We find that astrocytes display calcium dynamics unique to a fear-conditioned context, and chemogenetic inhibition of BLA fear ensembles does not have an impact on freezing behavior or calcium dynamics. These findings show that astrocytes play a key real-time role in fear learning and memory.
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Affiliation(s)
- Rebecca L Suthard
- Graduate Program for Neuroscience, Boston University, Boston, Massachusetts 02215
- Department of Psychological and Brain Sciences, Center for Systems Neuroscience, Neurophotonics Center, and Photonics Center, Boston University, Boston, Massachusetts 02215
| | - Ryan A Senne
- Graduate Program for Neuroscience, Boston University, Boston, Massachusetts 02215
- Department of Psychological and Brain Sciences, Center for Systems Neuroscience, Neurophotonics Center, and Photonics Center, Boston University, Boston, Massachusetts 02215
| | - Michelle D Buzharsky
- Undergraduate Program in Neuroscience, Boston University, Boston, Massachusetts 02215
| | - Angela Y Pyo
- Department of Psychological and Brain Sciences, Center for Systems Neuroscience, Neurophotonics Center, and Photonics Center, Boston University, Boston, Massachusetts 02215
| | - Kaitlyn E Dorst
- Graduate Program for Neuroscience, Boston University, Boston, Massachusetts 02215
- Department of Psychological and Brain Sciences, Center for Systems Neuroscience, Neurophotonics Center, and Photonics Center, Boston University, Boston, Massachusetts 02215
| | - Anh H Diep
- Undergraduate Program in Neuroscience, Boston University, Boston, Massachusetts 02215
| | - Rebecca H Cole
- Undergraduate Program in Neuroscience, Boston University, Boston, Massachusetts 02215
| | - Steve Ramirez
- Department of Biomedical Engineering, Boston University, Boston, Massachusetts 02215
- Department of Psychological and Brain Sciences, Center for Systems Neuroscience, Neurophotonics Center, and Photonics Center, Boston University, Boston, Massachusetts 02215
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Suthard RL, Jellinger AL, Surets M, Shpokayte M, Pyo AY, Buzharsky MD, Senne RA, Dorst K, Leblanc H, Ramirez S. Chronic Gq activation of ventral hippocampal neurons and astrocytes differentially affects memory and behavior. Neurobiol Aging 2023; 125:9-31. [PMID: 36801699 DOI: 10.1016/j.neurobiolaging.2023.01.007] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2022] [Revised: 12/20/2022] [Accepted: 01/13/2023] [Indexed: 02/01/2023]
Abstract
Network dysfunction is implicated in numerous diseases and psychiatric disorders, and the hippocampus serves as a common origin for these abnormalities. To test the hypothesis that chronic modulation of neurons and astrocytes induces impairments in cognition, we activated the hM3D(Gq) pathway in CaMKII+ neurons or GFAP+ astrocytes within the ventral hippocampus across 3, 6, and 9 months. CaMKII-hM3Dq activation impaired fear extinction at 3 months and acquisition at 9 months. Both CaMKII-hM3Dq manipulation and aging had differential effects on anxiety and social interaction. GFAP-hM3Dq activation impacted fear memory at 6 and 9 months. GFAP-hM3Dq activation impacted anxiety in the open field only at the earliest time point. CaMKII-hM3Dq activation modified the number of microglia, while GFAP-hM3Dq activation impacted microglial morphological characteristics, but neither affected these measures in astrocytes. Overall, our study elucidates how distinct cell types can modify behavior through network dysfunction, while adding a more direct role for glia in modulating behavior.
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Affiliation(s)
- Rebecca L Suthard
- Graduate Program for Neuroscience, Boston University, Boston, MA, USA; Department of Psychological and Brain Sciences, The Center for Systems Neuroscience, Neurophotonics Center, and Photonics Center, Boston University, Boston, MA, USA
| | - Alexandra L Jellinger
- Department of Psychological and Brain Sciences, The Center for Systems Neuroscience, Neurophotonics Center, and Photonics Center, Boston University, Boston, MA, USA
| | - Michelle Surets
- Undergraduate Program in Neuroscience, Boston University, Boston, MA, USA
| | - Monika Shpokayte
- Graduate Program for Neuroscience, Boston University, Boston, MA, USA; Department of Psychological and Brain Sciences, The Center for Systems Neuroscience, Neurophotonics Center, and Photonics Center, Boston University, Boston, MA, USA
| | - Angela Y Pyo
- Department of Psychological and Brain Sciences, The Center for Systems Neuroscience, Neurophotonics Center, and Photonics Center, Boston University, Boston, MA, USA
| | | | - Ryan A Senne
- Graduate Program for Neuroscience, Boston University, Boston, MA, USA; Department of Psychological and Brain Sciences, The Center for Systems Neuroscience, Neurophotonics Center, and Photonics Center, Boston University, Boston, MA, USA
| | - Kaitlyn Dorst
- Graduate Program for Neuroscience, Boston University, Boston, MA, USA; Department of Psychological and Brain Sciences, The Center for Systems Neuroscience, Neurophotonics Center, and Photonics Center, Boston University, Boston, MA, USA
| | - Heloise Leblanc
- Graduate Program for Neuroscience, Boston University, Boston, MA, USA; Department of Psychological and Brain Sciences, The Center for Systems Neuroscience, Neurophotonics Center, and Photonics Center, Boston University, Boston, MA, USA
| | - Steve Ramirez
- Department of Biomedical Engineering, Boston University, Boston, MA, USA; Department of Psychological and Brain Sciences, The Center for Systems Neuroscience, Neurophotonics Center, and Photonics Center, Boston University, Boston, MA, USA.
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