TY - DATA AB - Open the files in Jupyter Notebook (reccomended https://www.anaconda.com/distribution/#download-section with Python 3.7). AU - Nardin, Michele ID - 6062 TI - Supplementary Code and Data for the paper "The Entorhinal Cognitive Map is Attracted to Goals" ER - TY - THES AB - Brain function is mediated by complex dynamical interactions between excitatory and inhibitory cell types. The Cholecystokinin-expressing inhibitory cells (CCK-interneurons) are one of the least studied types, despite being suspected to play important roles in cognitive processes. We studied the network effects of optogenetic silencing of CCK-interneurons in the CA1 hippocampal area during exploration and sleep states. The cell firing pattern in response to light pulses allowed us to classify the recorded neurons in 5 classes, including disinhibited and non-responsive pyramidal cell and interneurons, and the inhibited interneurons corresponding to the CCK group. The light application, which inhibited the activity of CCK interneurons triggered wider changes in the firing dynamics of cells. We observed rate changes (i.e. remapping) of pyramidal cells during the exploration session in which the light was applied relative to the previous control session that was not restricted neither in time nor space to the light delivery. Also, the disinhibited pyramidal cells had higher increase in bursting than in single spike firing rate as a result of CCK silencing. In addition, the firing activity patterns during exploratory periods were more weakly reactivated in sleep for those periods in which CCK-interneuron were silenced than in the unaffected periods. Furthermore, light pulses during sleep disrupted the reactivation of recent waking patterns. Hence, silencing CCK neurons during exploration suppressed the reactivation of waking firing patterns in sleep and CCK interneuron activity was also required during sleep for the normal reactivation of waking patterns. These findings demonstrate the involvement of CCK cells in reactivation-related memory consolidation. An important part of our analysis was to test the relationship of the identified CCKinterneurons to brain oscillations. Our findings showed that these cells exhibited different oscillatory behaviour during anaesthesia and natural waking and sleep conditions. We showed that: 1) Contrary to the past studies performed under anaesthesia, the identified CCKinterneurons fired on the descending portion of the theta phase in waking exploration. 2) CCKinterneuron preferred phases around the trough of gamma oscillations. 3) Contrary to anaesthesia conditions, the average firing rate of the CCK-interneurons increased around the peak activity of the sharp-wave ripple (SWR) events in natural sleep, which is congruent with new reports about their functional connectivity. We also found that light driven CCK-interneuron silencing altered the dynamics on the CA1 network oscillatory activity: 1) Pyramidal cells negatively shifted their preferred theta phases when the light was applied, while interneurons responses were less consistent. 2) As a population, pyramidal cells negatively shifted their preferred activity during gamma oscillations, albeit we did not find gamma modulation differences related to the light application when pyramidal cells were subdivided into the disinhibited and unaffected groups. 3) During the peak of SWR events, all but the CCK-interneurons had a reduction in their relative firing rate change during the light application as compared to the change observed at SWR initiation. Finally, regarding to the place field activity of the recorded pyramidal neurons, we showed that the disinhibited pyramidal cells had reduced place field similarity, coherence and spatial information, but only during the light application. The mechanisms behind such observed behaviours might involve eCB signalling and plastic changes in CCK-interneuron synapses. In conclusion, the observed changes related to the light-mediated silencing of CCKinterneurons have unravelled characteristics of this interneuron subpopulation that might change the understanding not only of their particular network interactions, but also of the current theories about the emergence of certain cognitive processes such as place coding needed for navigation or hippocampus-dependent memory consolidation. AU - Rangel Guerrero, Dámaris K ID - 6849 SN - 2663-337X TI - The role of CCK-interneurons in regulating hippocampal network dynamics ER - TY - JOUR AB - Grid cells with their rigid hexagonal firing fields are thought to provide an invariant metric to the hippocampal cognitive map, yet environmental geometrical features have recently been shown to distort the grid structure. Given that the hippocampal role goes beyond space, we tested the influence of nonspatial information on the grid organization. We trained rats to daily learn three new reward locations on a cheeseboard maze while recording from the medial entorhinal cortex and the hippocampal CA1 region. Many grid fields moved toward goal location, leading to long-lasting deformations of the entorhinal map. Therefore, distortions in the grid structure contribute to goal representation during both learning and recall, which demonstrates that grid cells participate in mnemonic coding and do not merely provide a simple metric of space. AU - Boccara, Charlotte N. AU - Nardin, Michele AU - Stella, Federico AU - O'Neill, Joseph AU - Csicsvari, Jozsef L ID - 6194 IS - 6434 JF - Science SN - 0036-8075 TI - The entorhinal cognitive map is attracted to goals VL - 363 ER - TY - JOUR AB - 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. AU - Käfer, Karola AU - Malagon-Vina, Hugo AU - Dickerson, Desiree AU - O'Neill, Joseph AU - Trossbach, Svenja V. AU - Korth, Carsten AU - Csicsvari, Jozsef L ID - 5949 IS - 9 JF - Hippocampus TI - Disrupted-in-schizophrenia 1 overexpression disrupts hippocampal coding and oscillatory synchronization VL - 29 ER - TY - THES AB - The solving of complex tasks requires the functions of more than one brain area and their interaction. Whilst spatial navigation and memory is dependent on the hippocampus, flexible behavior relies on the medial prefrontal cortex (mPFC). To further examine the roles of the hippocampus and mPFC, we recorded their neural activity during a task that depends on both of these brain regions. With tetrodes, we recorded the extracellular activity of dorsal hippocampal CA1 (HPC) and mPFC neurons in Long-Evans rats performing a rule-switching task on the plus-maze. The plus-maze task had a spatial component since it required navigation along one of the two start arms and at the maze center a choice between one of the two goal arms. Which goal contained a reward depended on the rule currently in place. After an uncued rule change the animal had to abandon the old strategy and switch to the new rule, testing cognitive flexibility. Investigating the coordination of activity between the HPC and mPFC allows determination during which task stages their interaction is required. Additionally, comparing neural activity patterns in these two brain regions allows delineation of the specialized functions of the HPC and mPFC in this task. We analyzed neural activity in the HPC and mPFC in terms of oscillatory interactions, rule coding and replay. We found that theta coherence between the HPC and mPFC is increased at the center and goals of the maze, both when the rule was stable or has changed. Similar results were found for locking of HPC and mPFC neurons to HPC theta oscillations. However, no differences in HPC-mPFC theta coordination were observed between the spatially- and cue-guided rule. Phase locking of HPC and mPFC neurons to HPC gamma oscillations was not modulated by maze position or rule type. We found that the HPC coded for the two different rules with cofiring relationships between cell pairs. However, we could not find conclusive evidence for rule coding in the mPFC. Spatially-selective firing in the mPFC generalized between the two start and two goal arms. With Bayesian positional decoding, we found that the mPFC reactivated non-local positions during awake immobility periods. Replay of these non-local positions could represent entire behavioral trajectories resembling trajectory replay of the HPC. Furthermore, mPFC trajectory-replay at the goal positively correlated with rule-switching performance. Finally, HPC and mPFC trajectory replay occurred independently of each other. These results show that the mPFC can replay ordered patterns of activity during awake immobility, possibly underlying its role in flexible behavior. AU - Käfer, Karola ID - 6825 SN - 2663-337X TI - The hippocampus and medial prefrontal cortex during flexible behavior ER - TY - JOUR AB - With the advent of optogenetics, it became possible to change the activity of a targeted population of neurons in a temporally controlled manner. To combine the advantages of 60-channel in vivo tetrode recording and laser-based optogenetics, we have developed a closed-loop recording system that allows for the actual electrophysiological signal to be used as a trigger for the laser light mediating the optogenetic intervention. We have optimized the weight, size, and shape of the corresponding implant to make it compatible with the size, force, and movements of a behaving mouse, and we have shown that the system can efficiently block sharp wave ripple (SWR) events using those events themselves as a trigger. To demonstrate the full potential of the optogenetic recording system we present a pilot study addressing the contribution of SWR events to learning in a complex behavioral task. AU - Rangel Guerrero, Dámaris K AU - Donnett, James G. AU - Csicsvari, Jozsef L AU - Kovács, Krisztián ID - 5914 IS - 4 JF - eNeuro TI - Tetrode recording from the hippocampus of behaving mice coupled with four-point-irradiation closed-loop optogenetics: A technique to study the contribution of Hippocampal SWR events to learning VL - 5 ER - TY - THES AB - The hippocampus is a key brain region for spatial memory and navigation and is needed at all stages of memory, including encoding, consolidation, and recall. Hippocampal place cells selectively discharge at specific locations of the environment to form a cognitive map of the space. During the rest period and sleep following spatial navigation and/or learning, the waking activity of the place cells is reactivated within high synchrony events. This reactivation is thought to be important for memory consolidation and stabilization of the spatial representations. The aim of my thesis was to directly test whether the reactivation content encoded in firing patterns of place cells is important for consolidation of spatial memories. In particular, I aimed to test whether, in cases when multiple spatial memory traces are acquired during learning, the specific disruption of the reactivation of a subset of these memories leads to the selective disruption of the corresponding memory traces or through memory interference the other learned memories are disrupted as well. In this thesis, using a modified cheeseboard paradigm and a closed-loop recording setup with feedback optogenetic stimulation, I examined how the disruption of the reactivation of specific spiking patterns affects consolidation of the corresponding memory traces. To obtain multiple distinctive memories, animals had to perform a spatial task in two distinct cheeseboard environments and the reactivation of spiking patterns associated with one of the environments (target) was disrupted after learning during four hours rest period using a real-time decoding method. This real-time decoding method was capable of selectively affecting the firing rates and cofiring correlations of the target environment-encoding cells. The selective disruption led to behavioural impairment in the memory tests after the rest periods in the target environment but not in the other undisrupted control environment. In addition, the map of the target environment was less stable in the impaired memory tests compared to the learning session before than the map of the control environment. However, when the animal relearned the task, the same map recurred in the target environment that was present during learning before the disruption. Altogether my work demonstrated that the reactivation content is important: assembly-related disruption of reactivation can lead to a selective memory impairment and deficiency in map stability. These findings indeed suggest that reactivated assembly patterns reflect processes associated with the consolidation of memory traces. AU - Gridchyn, Igor ID - 48 SN - 2663-337X TI - Reactivation content is important for consolidation of spatial memory ER - TY - JOUR AB - Orientation in space is represented in specialized brain circuits. Persistent head direction signals are transmitted from anterior thalamus to the presubiculum, but the identity of the presubicular target neurons, their connectivity and function in local microcircuits are unknown. Here, we examine how thalamic afferents recruit presubicular principal neurons and Martinotti interneurons, and the ensuing synaptic interactions between these cells. Pyramidal neuron activation of Martinotti cells in superficial layers is strongly facilitating such that high-frequency head directional stimulation efficiently unmutes synaptic excitation. Martinotti-cell feedback plays a dual role: precisely timed spikes may not inhibit the firing of in-tune head direction cells, while exerting lateral inhibition. Autonomous attractor dynamics emerge from a modelled network implementing wiring motifs and timing sensitive synaptic interactions in the pyramidal - Martinotti-cell feedback loop. This inhibitory microcircuit is therefore tuned to refine and maintain head direction information in the presubiculum. AU - Simonnet, Jean AU - Nassar, Mérie AU - Stella, Federico AU - Cohen, Ivan AU - Mathon, Bertrand AU - Boccara, Charlotte AU - Miles, Richard AU - Fricker, Desdemona ID - 514 JF - Nature Communications SN - 20411723 TI - Activity dependent feedback inhibition may maintain head direction signals in mouse presubiculum VL - 8 ER - TY - THES AB - The hippocampus is a key brain region for memory and notably for spatial memory, and is needed for both spatial working and reference memories. Hippocampal place cells selectively discharge in specific locations of the environment to form mnemonic represen tations of space. Several behavioral protocols have been designed to test spatial memory which requires the experimental subject to utilize working memory and reference memory. However, less is known about how these memory traces are presented in the hippo campus, especially considering tasks that require both spatial working and long -term reference memory demand. The aim of my thesis was to elucidate how spatial working memory, reference memory, and the combination of both are represented in the hippocampus. In this thesis, using a radial eight -arm maze, I examined how the combined demand on these memories influenced place cell assemblies while reference memories were partially updated by changing some of the reward- arms. This was contrasted with task varian ts requiring working or reference memories only. Reference memory update led to gradual place field shifts towards the rewards on the switched arms. Cells developed enhanced firing in passes between newly -rewarded arms as compared to those containing an unchanged reward. The working memory task did not show such gradual changes. Place assemblies on occasions replayed trajectories of the maze; at decision points the next arm choice was preferentially replayed in tasks needing reference memory while in the pure working memory task the previously visited arm was replayed. Hence trajectory replay only reflected the decision of the animal in tasks needing reference memory update. At the reward locations, in all three tasks outbound trajectories of the current arm were preferentially replayed, showing the animals’ next path to the center. At reward locations trajectories were replayed preferentially in reverse temporal order. Moreover, in the center reverse replay was seen in the working memory task but in the other tasks forward replay was seen. Hence, the direction of reactivation was determined by the goal locations so that part of the trajectory which was closer to the goal was reactivated later in an HSE while places further away from the goal were reactivated earlier. Altogether my work demonstrated that reference memory update triggers several levels of reorganization of the hippocampal cognitive map which are not seen in simpler working memory demand s. Moreover, hippocampus is likely to be involved in spatial decisions through reactivating planned trajectories when reference memory recall is required for such a decision. AU - Xu, Haibing ID - 837 SN - 2663-337X TI - Reactivation of the hippocampal cognitive map in goal-directed spatial tasks ER - TY - JOUR AB - Sharp wave-ripple (SWR) oscillations play a key role in memory consolidation during non-rapid eye movement sleep, immobility, and consummatory behavior. However, whether temporally modulated synaptic excitation or inhibition underlies the ripples is controversial. To address this question, we performed simultaneous recordings of excitatory and inhibitory postsynaptic currents (EPSCs and IPSCs) and local field potentials (LFPs) in the CA1 region of awake mice in vivo. During SWRs, inhibition dominated over excitation, with a peak conductance ratio of 4.1 ± 0.5. Furthermore, the amplitude of SWR-associated IPSCs was positively correlated with SWR magnitude, whereas that of EPSCs was not. Finally, phase analysis indicated that IPSCs were phase-locked to individual ripple cycles, whereas EPSCs were uniformly distributed in phase space. Optogenetic inhibition indicated that PV+ interneurons provided a major contribution to SWR-associated IPSCs. Thus, phasic inhibition, but not excitation, shapes SWR oscillations in the hippocampal CA1 region in vivo. AU - Gan, Jian AU - Weng, Shih-Ming AU - Pernia-Andrade, Alejandro AU - Csicsvari, Jozsef L AU - Jonas, Peter M ID - 1118 IS - 2 JF - Neuron TI - Phase-locked inhibition, but not excitation, underlies hippocampal ripple oscillations in awake mice in vivo VL - 93 ER - TY - JOUR AB - The hippocampus is thought to initiate systems-wide mnemonic processes through the reactivation of previously acquired spatial and episodic memory traces, which can recruit the entorhinal cortex as a first stage of memory redistribution to other brain areas. Hippocampal reactivation occurs during sharp wave-ripples, in which synchronous network firing encodes sequences of places.We investigated the coordination of this replay by recording assembly activity simultaneously in the CA1 region of the hippocampus and superficial layers of the medial entorhinal cortex. We found that entorhinal cell assemblies can replay trajectories independently of the hippocampus and sharp wave-ripples. This suggests that the hippocampus is not the sole initiator of spatial and episodic memory trace reactivation. Memory systems involved in these processes may include nonhierarchical, parallel components. AU - O'Neill, Joseph AU - Boccara, Charlotte AU - Stella, Federico AU - Schönenberger, Philipp AU - Csicsvari, Jozsef L ID - 1132 IS - 6321 JF - Science SN - 00368075 TI - Superficial layers of the medial entorhinal cortex replay independently of the hippocampus VL - 355 ER - TY - JOUR AB - In real-world applications, observations are often constrained to a small fraction of a system. Such spatial subsampling can be caused by the inaccessibility or the sheer size of the system, and cannot be overcome by longer sampling. Spatial subsampling can strongly bias inferences about a system’s aggregated properties. To overcome the bias, we derive analytically a subsampling scaling framework that is applicable to different observables, including distributions of neuronal avalanches, of number of people infected during an epidemic outbreak, and of node degrees. We demonstrate how to infer the correct distributions of the underlying full system, how to apply it to distinguish critical from subcritical systems, and how to disentangle subsampling and finite size effects. Lastly, we apply subsampling scaling to neuronal avalanche models and to recordings from developing neural networks. We show that only mature, but not young networks follow power-law scaling, indicating self-organization to criticality during development. AU - Levina (Martius), Anna AU - Priesemann, Viola ID - 993 JF - Nature Communications SN - 20411723 TI - Subsampling scaling VL - 8 ER - TY - JOUR AB - During hippocampal sharp wave/ripple (SWR) events, previously occurring, sensory inputdriven neuronal firing patterns are replayed. Such replay is thought to be important for plasticity- related processes and consolidation of memory traces. It has previously been shown that the electrical stimulation-induced disruption of SWR events interferes with learning in rodents in different experimental paradigms. On the other hand, the cognitive map theory posits that the plastic changes of the firing of hippocampal place cells constitute the electrophysiological counterpart of the spatial learning, observable at the behavioral level. Therefore, we tested whether intact SWR events occurring during the sleep/rest session after the first exploration of a novel environment are needed for the stabilization of the CA1 code, which process requires plasticity. We found that the newly-formed representation in the CA1 has the same level of stability with optogenetic SWR blockade as with a control manipulation that delivered the same amount of light into the brain. Therefore our results suggest that at least in the case of passive exploratory behavior, SWR-related plasticity is dispensable for the stability of CA1 ensembles. AU - Kovács, Krisztián AU - O'Neill, Joseph AU - Schönenberger, Philipp AU - Penttonen, Markku AU - Rangel Guerrero, Dámaris K AU - Csicsvari, Jozsef L ID - 1279 IS - 10 JF - PLoS One TI - Optogenetically blocking sharp wave ripple events in sleep does not interfere with the formation of stable spatial representation in the CA1 area of the hippocampus VL - 11 ER - TY - JOUR AB - Hippocampal neurons encode a cognitive map of space. These maps are thought to be updated during learning and in response to changes in the environment through activity-dependent synaptic plasticity. Here we examine how changes in activity influence spatial coding in rats using halorhodopsin-mediated, spatially selective optogenetic silencing. Halorhoposin stimulation leads to light-induced suppression in many place cells and interneurons; some place cells increase their firing through disinhibition, whereas some show no effect. We find that place fields of the unaffected subpopulation remain stable. On the other hand, place fields of suppressed place cells were unstable, showing remapping across sessions before and after optogenetic inhibition. Disinhibited place cells had stable maps but sustained an elevated firing rate. These findings suggest that place representation in the hippocampus is constantly governed by activity-dependent processes, and that disinhibition may provide a mechanism for rate remapping. AU - Schönenberger, Philipp AU - O'Neill, Joseph AU - Csicsvari, Jozsef L ID - 1334 JF - Nature Communications TI - Activity dependent plasticity of hippocampal place maps VL - 7 ER - TY - JOUR AB - Rhythms with time scales of multiple cycles per second permeate the mammalian brain, yet neuroscientists are not certain of their functional roles. One leading idea is that coherent oscillation between two brain regions facilitates the exchange of information between them. In rats, the hippocampus and the vibrissal sensorimotor system both are characterized by rhythmic oscillation in the theta range, 5–12 Hz. Previous work has been divided as to whether the two rhythms are independent or coherent. To resolve this question, we acquired three measures from rats—whisker motion, hippocampal local field potential (LFP), and barrel cortex unit firing—during a whisker-mediated texture discrimination task and during control conditions (not engaged in a whisker-mediated memory task). Compared to control conditions, the theta band of hippocampal LFP showed a marked increase in power as the rats approached and then palpated the texture. Phase synchronization between whisking and hippocampal LFP increased by almost 50% during approach and texture palpation. In addition, a greater proportion of barrel cortex neurons showed firing that was phase-locked to hippocampal theta while rats were engaged in the discrimination task. Consistent with a behavioral consequence of phase synchronization, the rats identified the texture more rapidly and with lower error likelihood on trials in which there was an increase in theta-whisking coherence at the moment of texture palpation. These results suggest that coherence between the whisking rhythm, barrel cortex firing, and hippocampal LFP is augmented selectively during epochs in which the rat collects sensory information and that such coherence enhances the efficiency of integration of stimulus information into memory and decision-making centers. AU - Grion, Natalia AU - Akrami, Athena AU - Zuo, Yangfang AU - Stella, Federico AU - Diamond, Mathew ID - 1487 IS - 2 JF - PLoS Biology TI - Coherence between rat sensorimotor system and hippocampus is enhanced during tactile discrimination VL - 14 ER - TY - JOUR AB - CREB-binding protein (CBP) and p300 are transcriptional coactivators involved in numerous biological processes that affect cell growth, transformation, differentiation, and development. In this study, we provide evidence of the involvement of homeodomain-interacting protein kinase 2 (HIPK2) in the regulation of CBP activity. We show that HIPK2 interacts with and phosphorylates several regions of CBP. We demonstrate that serines 2361, 2363, 2371, 2376, and 2381 are responsible for the HIPK2-induced mobility shift of CBP C-terminal activation domain. Moreover, we show that HIPK2 strongly potentiates the transcriptional activity of CBP. However, our data suggest that HIPK2 activates CBP mainly by counteracting the repressive action of cell cycle regulatory domain 1 (CRD1), located between amino acids 977 and 1076, independently of CBP phosphorylation. Our findings thus highlight a complex regulation of CBP activity by HIPK2, which might be relevant for the control of specific sets of target genes involved in cellular proliferation, differentiation and apoptosis. AU - Kovács, Krisztián AU - Steinmann, Myriam AU - Halfon, Olivier AU - Magistretti, Pierre AU - Cardinaux, Jean ID - 1663 IS - 11 JF - Cellular Signalling TI - Complex regulation of CREB-binding protein by homeodomain-interacting protein kinase 2 VL - 27 ER - TY - JOUR AB - The hippocampal region, comprising the hippocampal formation and the parahippocampal region, has been one of the most intensively studied parts of the brain for decades. Better understanding of its functional diversity and complexity has led to an increased demand for specificity in experimental procedures and manipulations. In view of the complex 3D structure of the hippocampal region, precisely positioned experimental approaches require a fine-grained architectural description that is available and readable to experimentalists lacking detailed anatomical experience. In this paper, we provide the first cyto- and chemoarchitectural description of the hippocampal formation and parahippocampal region in the rat at high resolution and in the three standard sectional planes: coronal, horizontal and sagittal. The atlas uses a series of adjacent sections stained for neurons and for a number of chemical marker substances, particularly parvalbumin and calbindin. All the borders defined in one plane have been cross-checked against their counterparts in the other two planes. The entire dataset will be made available as a web-based interactive application through the Rodent Brain WorkBench (http://www.rbwb.org) which, together with this paper, provides a unique atlas resource. AU - Boccara, Charlotte AU - Kjønigsen, Lisa AU - Hammer, Ingvild AU - Bjaalie, Jan AU - Leergaard, Trygve AU - Witter, Menno ID - 1874 IS - 7 JF - Hippocampus TI - A three-plane architectonic atlas of the rat hippocampal region VL - 25 ER - TY - JOUR AB - Learning can be facilitated by previous knowledge when it is organized into relational representations forming schemas. In this issue of Neuron, McKenzie et al. (2014) demonstrate that the hippocampus rapidly forms interrelated, hierarchical memory representations to support schema-based learning. AU - O'Neill, Joseph AU - Csicsvari, Jozsef L ID - 2003 IS - 1 JF - Neuron TI - Learning by example in the hippocampus VL - 83 ER - TY - JOUR AB - By eliciting a natural exploratory behavior in rats, head scanning, a study reveals that hippocampal place cells form new, stable firing fields in those locations where the behavior has just occurred. AU - Dupret, David AU - Csicsvari, Jozsef L ID - 2005 IS - 5 JF - Nature Neuroscience TI - Turning heads to remember places VL - 17 ER - TY - JOUR AB - Sharp wave/ripple (SWR, 150–250 Hz) hippocampal events have long been postulated to be involved in memory consolidation. However, more recent work has investigated SWRs that occur during active waking behaviour: findings that suggest that SWRs may also play a role in cell assembly strengthening or spatial working memory. Do such theories of SWR function apply to animal learning? This review discusses how general theories linking SWRs to memory-related function may explain circuit mechanisms related to rodent spatial learning and to the associated stabilization of new cognitive maps. AU - Csicsvari, Jozsef L AU - Dupret, David ID - 2251 IS - 1635 JF - Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences SN - 09628436 TI - Sharp wave/ripple network oscillations and learning-associated hippocampal maps VL - 369 ER -