@article{14314,
  abstract     = {The execution of cognitive functions requires coordinated circuit activity across different brain areas that involves the associated firing of neuronal assemblies. Here, we tested the circuit mechanism behind assembly interactions between the hippocampus and the medial prefrontal cortex (mPFC) of adult rats by recording neuronal populations during a rule-switching task. We identified functionally coupled CA1-mPFC cells that synchronized their activity beyond that expected from common spatial coding or oscillatory firing. When such cell pairs fired together, the mPFC cell strongly phase locked to CA1 theta oscillations and maintained consistent theta firing phases, independent of the theta timing of their CA1 counterpart. These functionally connected CA1-mPFC cells formed interconnected assemblies. While firing together with their CA1 assembly partners, mPFC cells fired along specific theta sequences. Our results suggest that upregulated theta oscillatory firing of mPFC cells can signal transient interactions with specific CA1 assemblies, thus enabling distributed computations.},
  author       = {Nardin, Michele and Käfer, Karola and Stella, Federico and Csicsvari, Jozsef L},
  issn         = {2211-1247},
  journal      = {Cell Reports},
  number       = {9},
  publisher    = {Elsevier},
  title        = {{Theta oscillations as a substrate for medial prefrontal-hippocampal assembly interactions}},
  doi          = {10.1016/j.celrep.2023.113015},
  volume       = {42},
  year         = {2023},
}

@unpublished{10080,
  abstract     = {Hippocampal and neocortical neural activity is modulated by the position of the individual in space. While hippocampal neurons provide the basis for a spatial map, prefrontal cortical neurons generalize over environmental features. Whether these generalized representations result from a bidirectional interaction with, or are mainly derived from hippocampal spatial representations is not known. By examining simultaneously recorded hippocampal and medial prefrontal neurons, we observed that prefrontal spatial representations show a delayed coherence with hippocampal ones. We also identified subpopulations of cells in the hippocampus and medial prefrontal cortex that formed functional cross-area couplings; these resembled the optimal connections predicted by a probabilistic model of spatial information transfer and generalization. Moreover, cross-area couplings were strongest and had the shortest delay preceding spatial decision-making. Our results suggest that generalized spatial coding in the medial prefrontal cortex is inherited from spatial representations in the hippocampus, and that the routing of information can change dynamically with behavioral demands.},
  author       = {Nardin, Michele and Käfer, Karola and Csicsvari, Jozsef L},
  booktitle    = {bioRxiv},
  publisher    = {Cold Spring Harbor Laboratory},
  title        = {{The generalized spatial representation in the prefrontal cortex is inherited from the hippocampus}},
  doi          = {10.1101/2021.09.30.462269},
  year         = {2021},
}

@article{7472,
  abstract     = {Temporally organized reactivation of experiences during awake immobility periods is thought to underlie cognitive processes like planning and evaluation. While replay of trajectories is well established for the hippocampus, it is unclear whether the medial prefrontal cortex (mPFC) can reactivate sequential behavioral experiences in the awake state to support task execution. We simultaneously recorded from hippocampal and mPFC principal neurons in rats performing a mPFC-dependent rule-switching task on a plus maze. We found that mPFC neuronal activity encoded relative positions between the start and goal. During awake immobility periods, the mPFC replayed temporally organized sequences of these generalized positions, resembling entire spatial trajectories. The occurrence of mPFC trajectory replay positively correlated with rule-switching performance. However, hippocampal and mPFC trajectory replay occurred independently, indicating different functions. These results demonstrate that the mPFC can replay ordered activity patterns representing generalized locations and suggest that mPFC replay might have a role in flexible behavior.},
  author       = {Käfer, Karola and Nardin, Michele and Blahna, Karel and Csicsvari, Jozsef L},
  issn         = {0896-6273},
  journal      = {Neuron},
  number       = {1},
  pages        = {P154--165.e6},
  publisher    = {Elsevier},
  title        = {{Replay of behavioral sequences in the medial prefrontal cortex during rule switching}},
  doi          = {10.1016/j.neuron.2020.01.015},
  volume       = {106},
  year         = {2020},
}

@article{5949,
  abstract     = {Aberrant proteostasis of protein aggregation may lead to behavior disorders including chronic mental illnesses (CMI). Furthermore, the neuronal activity alterations that underlie CMI are not well understood. We recorded the local field potential and single-unit activity of the hippocampal CA1 region in vivo in rats transgenically overexpressing the Disrupted-in-Schizophrenia 1 (DISC1) gene (tgDISC1), modeling sporadic CMI. These tgDISC1 rats have previously been shown to exhibit DISC1 protein aggregation, disturbances in the dopaminergic system and attention-related deficits. Recordings were performed during exploration of familiar and novel open field environments and during sleep, allowing investigation of neuronal abnormalities in unconstrained behavior. Compared to controls, tgDISC1 place cells exhibited smaller place fields and decreased speed-modulation of their firing rates, demonstrating altered spatial coding and deficits in encoding location-independent sensory inputs. Oscillation analyses showed that tgDISC1 pyramidal neurons had higher theta phase locking strength during novelty, limiting their phase coding ability. However, their mean theta phases were more variable at the population level, reducing oscillatory network synchronization. Finally, tgDISC1 pyramidal neurons showed a lack of novelty-induced shift in their preferred theta and gamma firing phases, indicating deficits in coding of novel environments with oscillatory firing. By combining single cell and neuronal population analyses, we link DISC1 protein pathology with abnormal hippocampal neural coding and network synchrony, and thereby gain a more comprehensive understanding of CMI mechanisms.},
  author       = {Käfer, Karola and Malagon-Vina, Hugo and Dickerson, Desiree and O'Neill, Joseph and Trossbach, Svenja V. and Korth, Carsten and Csicsvari, Jozsef L},
  journal      = {Hippocampus},
  number       = {9},
  pages        = {802--816},
  publisher    = {Wiley},
  title        = {{Disrupted-in-schizophrenia 1 overexpression disrupts hippocampal coding and oscillatory synchronization}},
  doi          = {10.1002/hipo.23076},
  volume       = {29},
  year         = {2019},
}