Article
Neurosciences
Erwan Leprince, Robin F. Dard, Salome Mortet, Caroline Filippi, Marie Giorgi-Kurz, Romain Bourboulou, Pierre-Pascal Lenck-Santini, Michel A. Picardo, Marco Bocchio, Agnes Baude, Rosa Cossart
Summary: The adult CA1 region of the hippocampus produces coordinated neuronal dynamics with minimal reliance on its extrinsic inputs. Neonatal CA1, on the other hand, is tightly linked to externally generated sensorimotor activity, but the circuit mechanisms underlying early synchronous activity in CA1 remain unclear. In this study, researchers use a combination of in vivo and ex vivo circuit mapping, calcium imaging, and electrophysiological recordings in mouse pups to investigate the dynamics in the ventro-intermediate CA1. They find that these dynamics are influenced by both the entorhinal (EC) and thalamic (VMT) inputs, but movement-related population bursts are exclusively driven by the EC. The differential effects reflect the different intrahippocampal targets of these inputs, suggesting distinct contributions to the development of the hippocampal microcircuit and related cognitive maps.
Article
Biochemistry & Molecular Biology
Laurel Watkins de Jong, Mohammadreza Mohagheghi Nejad, Euisik Yoon, Sen Cheng, Kamran Diba
Summary: Recurrent connectivity and feedback inhibition from inhibitory neurons play crucial roles in determining the dynamics and computational properties of neuronal circuits. Through optogenetic manipulations and large-scale unit recordings, paradoxical responses were observed in both CA1 and CA3 regions of the hippocampus, where subsets of cells increased firing during photoinhibition while others decreased firing during photoexcitation. These paradoxical responses were more prominent in CA3 and simulations confirmed that both CA1 and CA3 hippocampal regions exhibit inhibition-stabilized networks with strong recurrent excitation.
Article
Cell Biology
Michele Nardin, Karola Kaefer, Federico Stella, Jozsef Csicsvari
Summary: This study investigated the circuit mechanism of neuronal assembly interactions between the hippocampus and the medial prefrontal cortex (mPFC) in adult rats during a rule-switching task. The results revealed functionally coupled CA1-mPFC cells that synchronized their activity beyond spatial coding or oscillatory firing. These functionally connected cells formed interconnected assemblies, and the upregulated theta oscillatory firing of mPFC cells enabled transient interactions with specific CA1 assemblies for distributed computations.
Article
Biology
Shinya Ohara, Stefan Blankvoort, Rajeevkumar Raveendran Nair, Maximiliano J. Nigro, Eirik S. Nilssen, Clifford Kentros, Menno P. Witter
Summary: Research indicates the presence of different operational principles in the connections from layer Vb to Va in the entorhinal cortex, with these connections being stronger in dorsal LEC compared to dorsal MEC. This suggests a potential difference in how LEC and MEC mediate episodic memory consolidation in the brain.
Article
Anatomy & Morphology
Oyvind Wilsgard Simonsen, Rafal Czajkowski, Menno P. Witter
Summary: The medial entorhinal cortex (MEC) and the retrosplenial cortex (RSC) are both involved in spatial processing, and this study reveals that RSC projections synapse onto MEC layer V neurons, which also receive input from the hippocampal formation. These findings suggest that convergent information from RSC and the subiculum contributes to the signal sent from superficial layers of the MEC to the hippocampal formation.
BRAIN STRUCTURE & FUNCTION
(2022)
Article
Neurosciences
Ipshita Zutshi, Manuel Valero, Antonio Fernandez-Ruiz, Gyorgy Buzsaki
Summary: The extent to which neuronal spiking reflects local computation or responses to upstream inputs in circuit operations is a key problem in understanding. By performing experiments on the hippocampus, this study revealed that silencing the medial entorhinal cortex (mEC) largely abolished theta and gamma currents in CA1, while CA3 and local CA1 silencing strongly decreased firing of CA1 neurons. Despite these perturbations, the CA1 circuit was still able to support place field activity and maintain the spatial map.
Article
Neurosciences
Tsukasa Funane, Heechul Jun, Stephanie Sutoko, Takaomi C. Saido, Akihiko Kandori, Kei M. Igarashi
Summary: Clinical evidence suggests that disruptions in the coordination of sharp-wave ripples (SWRs) between the entorhinal cortex and hippocampal CA1 may serve as an early network symptom that precedes memory impairment in Alzheimer's disease. This study found that the coordination of SWRs between the medial entorhinal cortex (MEC) layers and CA1 was disrupted in amyloid precursor protein knock-in (APP-KI) mice, even before the emergence of spatial memory impairments. These findings provide insight into the underlying brain circuit mechanisms of memory impairments in Alzheimer's disease.
FRONTIERS IN SYSTEMS NEUROSCIENCE
(2022)
Article
Multidisciplinary Sciences
Heather C. Ratigan, Seetha Krishnan, Shai Smith, Mark E. J. Sheffield
Summary: The NR-CA1 pathway actively suppresses fear by disrupting contextual fear memory retrieval in CA1 during fearful freezing behavior, which also reduces fear generalization and accelerates extinction.
NATURE COMMUNICATIONS
(2023)
Article
Neurosciences
Sebi Rolotti, Heike Blockus, Fraser T. Sparks, James B. Priestley, Attila Losonczy
Summary: The hippocampus plays a critical role in memory consolidation, particularly during sharp-wave ripple (SWR) events. This study investigated the relationship between network state and information processing in dendrites, the primary sites of synaptic input integration and plasticity. The researchers found that immobility led to increased dendritic activity, which was concentrated during SWR events. Concurrent dendritic and somatic activity during SWRs predicted increased coupling during subsequent exploration of a novel environment. Somatic-dendritic coupling and SWR recruitment also varied based on cells' tuning distance to reward location during a goal-learning task.
Article
Biophysics
Daniela Bianchi, Rosanna Migliore, Paola Vitale, Machhindra Garad, Paula A. Pousinha, Helene Marie, Volkmar Lessmann, Michele Migliore
Summary: This paper highlights an electrophysiological feature observed in mouse CA1 pyramidal cells that has been ignored by researchers. The increase in membrane potential during sustained inputs cannot be explained by current computational models. A new model is proposed to address this issue.
BIOPHYSICAL JOURNAL
(2022)
Article
Cell Biology
Aditya Srinivasan, Arvind Srinivasan, Justin S. Riceberg, Michael R. Goodman, Kevin G. Guise, Matthew L. Shapiro
Summary: This article investigates how the hippocampus and prefrontal cortex describe events using spatial structures in the execution of memory tasks. The study found that ensembles in both brain regions can distinguish task features by the distances between state-space locations, and prefrontal modulation of hippocampal activity may guide decision-making.
Article
Biochemistry & Molecular Biology
Ipshita Zutshi, Gyorgy Buzsaki
Summary: The entorhinal cortex (EC) plays a crucial role in controlling the occurrence and neuronal content of hippocampal sharp-wave ripples (SPW-Rs), which are important for memory consolidation and retrieval.
Article
Neurosciences
Marissa C. Applegate, Konstantin S. Gutnichenko, Dmitriy Aronov
Summary: The mammalian hippocampal formation is organized based on different functions and inputs. These inputs contribute to the organization along the long axis and the transverse axis of the hippocampus. In this study, retrograde tracing was used to map the inputs into the hippocampal formation of a food-caching bird, the black-capped chickadee. The results revealed unique patterns of inputs, similar to those observed in mammals, highlighting the anatomical similarities across distantly related species.
JOURNAL OF COMPARATIVE NEUROLOGY
(2023)
Article
Biochemical Research Methods
Sam C. Berens, Chris M. Bird
Summary: This study investigates the mechanisms of memory generalisation and finds that humans tend to use encoding-based mechanisms to store relational codes for memory generalisation. The study also reveals the impact of training schedules and hierarchical distances on these mechanisms.
PLOS COMPUTATIONAL BIOLOGY
(2022)
Article
Geriatrics & Gerontology
Nicholas M. DiCola, Alexa L. Lacy, Omar J. Bishr, Kathryn M. Kimsey, Jenna L. Whitney, Sarah D. Lovett, Sara N. Burke, Andrew P. Maurer
Summary: Sharp wave/ripples/high frequency events (HFEs) are bursts of depolarization that occur in the hippocampal subregions CA3 and CA1 during rest and pauses in behavior. While the frequency of CA1 ripples decreases with age, there are no age differences in the frequency of CA3 HFEs. Age-related differences in CA1 ripples cannot be explained by alterations in CA3 HFE characteristics.
NEUROBIOLOGY OF AGING
(2022)
Article
Computer Science, Artificial Intelligence
Christian Leibold
Article
Neurosciences
Marta Sabariego, Nina S. Tabrizi, Greer J. Marshall, Ali N. McLagan, Safa Jawad, Jena B. Hales
Summary: The study found that hippocampal lesions resulted in a selective impairment in discriminating elapsed time, especially during longer delay trials. Additionally, rats with hippocampal lesions performed worse under the 20-second delay condition compared to sham-lesioned rats.
Article
Neurosciences
Alexander R. Callan, Martin Hess, Felix Felmy, Christian Leibold
Summary: Researchers have found that neurons in the medial superior olive (MSO) have highly integrated synaptic inputs on their dendrites, enabling secure transmission through coordinated release of neurotransmitters at multiple independent active zones. The anatomical arrangement increases the amplitude and sharpens the time course of excitatory postsynaptic potentials, leading to improved binaural coincidence detection compared with single large synapses at the soma.
JOURNAL OF NEUROSCIENCE
(2021)
Article
Cell Biology
Prateep Beed, Roberto de Filippo, Constance Holman, Friedrich W. Johenning, Christian Leibold, Antonio Caputi, Hannah Monyer, Dietmar Schmitz
Article
Neurosciences
Xin Liu, Chi Ren, Yichen Lu, Yixiu Liu, Jeong-Hoon Kim, Stefan Leutgeb, Takaki Komiyama, Duygu Kuzum
Summary: The authors introduced a flexible, insertable, and transparent microelectrode array, Neuro-FITM, for multimodal recordings of cortical and hippocampal activity patterns. They demonstrated that diverse cortical activity patterns accompanied hippocampal sharp-wave ripples, with cortical activation often preceding the ripples. This suggests a selective and diverse interaction between hippocampal and large-scale cortical activity during sharp-wave ripples, underlying various cognitive functions.
NATURE NEUROSCIENCE
(2021)
Article
Computer Science, Cybernetics
Michael Rebhan, Christian Leibold
Summary: This paper proposes a modeling approach to simulate the responses of octopus cells to arbitrary sound pressure waves, revealing that octopus cells are particularly sensitive to high-frequency transients in natural sounds and provide a population code for sound level through sustained firing to phonemes.
BIOLOGICAL CYBERNETICS
(2021)
Article
Cell Biology
Dustin Fetterhoff, Andrey Sobolev, Christian Leibold
Summary: The study explores how hippocampal ensembles combine multimodal sensory cues, focusing on hippocampal CA1 remapping in Mongolian gerbils in a 1D virtual reality experiment. It is observed that self-motion cues are over-represented, while responsiveness to allocentric visual cues elicits rate and global remapping in the hippocampal ensemble, even when task-irrelevant.
Article
Neurosciences
Yuk-Hoi Yiu, Jill K. Leutgeb, Christian Leibold
Summary: The study reveals that rate and spike timing codes in the hippocampus are related, and the directionality of place field correlations is also associated. This suggests that encoding of directional information in the hippocampus may involve multiple mechanisms, contributing to a better understanding of how directional information is encoded.
JOURNAL OF NEUROSCIENCE
(2022)
Article
Behavioral Sciences
Annette Vo, Nina S. Tabrizi, Thomas Hunt, Kayla Cayanan, Saee Chitale, Lucy G. Anderson, Sarah Tenney, Andre O. White, Marta Sabariego, Jena B. Hales
Summary: This study examined the role of the medial entorhinal cortex (MEC) in rats performing a time duration discrimination task (TDD). The results showed that MEC neural computations are essential for time processing only for delays exceeding 10 seconds.
NEUROBIOLOGY OF LEARNING AND MEMORY
(2021)
Article
Neurosciences
Pascal Jorratt, Jan Ricny, Christian Leibold, Saak V. Ovsepian
Summary: The impairment of N-methyl-D-aspartate receptor (NMDAR) activity has been associated with various neuropsychiatric disorders, such as schizophrenia. This study examined the effects of different endogenous modulators of NMDAR on neuronal viability, glutamate release, and dendritic morphology in rat cortical cultures. The results showed that the exposure to NMDAR modulators did not affect glutamate release or neuronal viability. However, prolonged treatment with physiological concentrations of NMDAR modulators led to enhanced dendritic field expansion, particularly with spermidine and pregnenolone sulfate. These findings suggest that constitutive glutamatergic activity mediated by NMDAR controls dendritic field expansion and may influence the integrative properties of cortical neurons.
MOLECULAR NEUROBIOLOGY
(2023)
Editorial Material
Neurosciences
Alexander Borst, Christian Leibold
Summary: With volumetric EM techniques, large connectomic datasets are created, providing knowledge about neural circuit connectivity. This allows for numerical simulation of detailed neuron models. However, the large number of parameters in these models makes it difficult to determine essential circuit functions. Two mathematical strategies, namely linear dynamical systems analysis and matrix reordering techniques, are reviewed to gain insight into connectomics data and make predictions about information processing and functional units in large networks.
JOURNAL OF NEUROSCIENCE
(2023)
Review
Neurosciences
Ileana L. Hanganu-Opatz, Thomas Klausberger, Torfi Sigurdsson, Andreas Nieder, Simon N. Jacob, Marlene Bartos, Jonas-Frederic Sauer, Daniel Durstewitz, Christian Leibold, Ilka Diester
Summary: The prefrontal cortex is responsible for complex behaviors and its cellular ensembles play a crucial role in coordinating stability and flexibility of neural representations. Recent research suggests that temporal coordination and prefrontal connectivity patterns are important for adaptive cognitive behavior.
Article
Neurosciences
Xu Huang, Magdalene Isabell Schlesiger, Isabel Barriuso-Ortega, Christian Leibold, Duncan Archibald Allan MacLaren, Nina Bieber, Hannah Monyer
Summary: The lateral entorhinal cortex (LEC) is a crucial cortical input area to the hippocampus, responsible for associative object-place-context memories. Recent studies have found a gradient of spatial selectivity along the antero-posterior axis of the LEC, with distinct spatial maps generated for different contexts. Additionally, there are neurons in the LEC that encode both space and objects conjunctively.
Article
Computer Science, Cybernetics
Christian Leibold
Summary: This paper proposes a theory that the retrieval of episodic memories involves the reactivation of neuronal activity patterns, with the content of the memories stored in synaptic connections. The theory suggests that the temporal order information in neuronal reservoir sequences is conveyed to sensory-motor cortical areas, resulting in the subjective impression of memory retrieval of sensory motor events. The theory is supported by the use of a recursive version of support vector regression for continuous learning, limited only by the representational capacity of the reservoir. It is also consistent with confabulations and post hoc alterations of existing memories.
BIOLOGICAL CYBERNETICS
(2022)
Article
Biology
Sarah Tenney, Eleftheria Vogiatzoglou, Deena Chohan, Annette Vo, Thomas Hunt, Kayla Cayanan, Jena B. Hales, Marta Sabariego
Summary: Research indicates that both spatial and temporal information are crucial for episodic memory. While spatial tasks have been extensively used to study the behavioral relevance of place cells, the study of time cells has often overlooked the duration of time as a key variable in behavioral paradigms. Through the novel TDD task, researchers aim to directly investigate the neurological mechanisms underlying temporal processing.
