Replay

Liset de la Prida discusses hippocampal sharp-wave ripples and their relationship to replay and memory. The conversation connects different ripple patterns and neuron types to population activity, asking how particular cells help shape the lower-dimensional dynamics used to describe neural computation.

…cells in the hippocampus are known to replay past trajectories. These recapitulations of previous experiences are proposed to spread across cortical areas, constituting a hallmark of system-level consolidation theories and providing clear predictions about how hippocampus and cortex coordinate during sleep. We aimed to test these predictions by answering the following questions: 1) Can replay be detected in V1 during sleep?

…place cells, replay).In order to u

…The reactivation or “replay” of previously active place cell sequences during sharp wave-ripples (SWRs) is believed to be important for spatial memory-guided planning and spatial memory consolidation. Previous research has shown that SWRs are abnormal in a mouse model of FXS (Boone et al. 2018), but to our knowledge the replay of place cell sequence

The hippocampus reinstates learned sequences in temporally compressed "replay" epochs inside sharp-wave ripples (SWRs), which occur while an animal is at rest. Replay is required for the long-term consolidation of memories. However, the content of these replay episodes, and in particular whether specific experiences or an abstract representation of the world are consolidated, remains controversial. Using two-photon calcium imaging of CA3 outputs combined with simultaneous local field potential recordings, we show that the statistics of replay deviate significantly from those of experience: hig

Although hippocampal place cells prominently "replay" nonlocal trajectories, the computational function of these events remains elusive. One hypothesis holds that replay plans routes to current goals by propagating information about rewards over space. An alternative view contends that replay learns and maintains routes more generally, separate from current goals or plans, to update a "cognitive map". The former view has been formalized in a reinforcement learning framework (Mattar and Daw, 2018), which predicts which trajectories should be replayed preferentially ("prioritized") to support pl

Replay, a phenomenon whereby cells reactivate representations of spatial trajectories, is thought to be crucial for the storage and consolidation of spatial memories. This phenomenon is commonly studied with respect to a single spatial environment. However, sleeping rats can replay trajectories of the spatial environment they previously experienced and awake rats can replay spatial trajectories of the spatial environment they are in and previously experienced environments. This means that care is needed when interpreting replay, as it may represent a replay of the current environment or anothe

New tasks are often similar in structure to old ones. Animals that take advantage of such conserved or “abstract” task structures can master new tasks with minimal training. To understand the neural basis of this abstraction, we developed a novel behavioural paradigm for mice: the “ABCD” task, and recorded from their medial frontal neurons as they learned. Animals learned multiple tasks where they had to visit 4 rewarded locations on a spatial maze in sequence, which defined a sequence of four “task states” (ABCD). Tasks shared the same circular transition structure (… ABCDABCD …) but differed

…through the environment called replays that resemble the animal's behavior. Replay has been proposed as a form of virtual experience that supplements real experience for the purposes of learning and planning. However, it is unknown whether the precise spatial tuning of place cells as a function of animal position is preserved as a function of encoded replay position, independent of the animal's location. This is far from obviou

Replay, the sequential reactivation of a neuronal ensemble, is thought to play a central role in the hippocampus during the consolidation of a recent experience into a long-term memory. Following a contextual change (e.g. entering a novel environment), hippocampal place cells typically modulate their in-field firing rate and shift the position of their place field, providing a rate and place representation for the behavioral episode, respectively. However, replay has been largely defined by only the latter- based on the fidelity of sequential activity across neighboring place fields. Here we s

The hippocampus reinstates learned sequences in temporally compressed "replay" epochs inside sharp-wave ripples (SWRs), which occur while an animal is at rest. Replay is required for the long-term consolidation of memories. However, the content of these replay episodes, and in particular whether specific experiences or a task-optimized representation of the world are consolidated, remains controversial. Using two-photon calcium imaging of CA3 outputs combined with simultaneous local field potential (LFP) recordings, our group has shown that the statistics of replay deviate significantly from t

…recapitulate past trajectories (‘replay’). Replay has been hypothesised to support systems consolidation – the stabilisation of new memories via maturation of complementary cortical memory traces. Indeed, in recent work we found place and grid cells, from the deep medial entorhinal cortex (dMEC, the principal c

…in the hippocampus take part in replay sequences, time-compressed reactivations of trajectories through space the animal has previously explored. These replay sequences have been proposed to be a form of memory for previously experienced places. I will present work exploring how these replays appear and change with experience. By recording from large ensembles of hippocampal neurons as rats explored novel and familiar linear tracks in various experiments, we found that hippocampal replays appear after a single experience and slow d