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Journal ArticleDOI

The role of the dentate gyrus in mnemonic functions

26 Nov 2020-Neuroforum (De Gruyter)-Vol. 26, Iss: 4, pp 247-254
TL;DR: How memory engrams emerge during learning is addressed in the dentate gyrus as the input gate of the hippocampus, which has an indispensable role in conscious memory formation, and how GABAergic interneurons may contribute to this process is examined.
Abstract: Abstract The hippocampus is decisive for the storage of conscious memories. Current theories suggest that experience-dependent modifications in excitation–inhibition balance enable a select group of neurons to form a new cell association during learning which represents the new memory trace. It was further proposed that particularly GABAergic-inhibitory interneurons have a large impact on population activity in neuronal networks by means of their inhibitory output synapses. They synchronize active principal cells at high frequencies, thereby supporting their binding to cell assemblies to jointly encode information. However, how cell associations emerge in space and time and how interneurons may contribute to this process is still largely unknown. We started to address this fundamental question in the dentate gyrus (DG) as the input gate of the hippocampus, which has an indispensable role in conscious memory formation. We used a combination of in vivo chronic two-photon imaging of population activity in the DG and the hippocampal areas CA1–3 of mice exposed to a virtual reality, in which they perform a goal-oriented spatial memory tasks, with high-density in vivo recordings and multiple whole-cell recordings in acute slice preparations, to determine how memory engrams emerge during learning. We further examine how GABAergic interneurons may contribute to this process. We believe that these lines of research will add to a better understanding on the mechanisms of memory formation in cortical networks.
Citations
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01 Jul 2018
TL;DR: Recently, several studies have provided insight into the brain networks driving SCM through the characterization of memory engram cells, their biochemical and physiological changes and the circuits in which they operate, and it is described how these findings have led to a revamped understanding of SCM in the brain.
Abstract: What happens to memories as days, weeks and years go by has long been a fundamental question in neuroscience and psychology. For decades, researchers have attempted to identify the brain regions in which memory is formed and to follow its changes across time. The theory of systems consolidation of memory (SCM) suggests that changes in circuitry and brain networks are required for the maintenance of a memory with time. Various mechanisms by which such changes may take place have been hypothesized. Recently, several studies have provided insight into the brain networks driving SCM through the characterization of memory engram cells, their biochemical and physiological changes and the circuits in which they operate. In this Review, we place these findings in the context of the field and describe how they have led to a revamped understanding of SCM in the brain.

172 citations

References
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Journal ArticleDOI
TL;DR: Preliminary observations on the behaviour of hippocampusal units in the freely moving rat provide support for this theory of hippocampal function.

5,549 citations

Journal ArticleDOI
25 Jun 2004-Science
TL;DR: Recent findings indicate that network oscillations bias input selection, temporally link neurons into assemblies, and facilitate synaptic plasticity, mechanisms that cooperatively support temporal representation and long-term consolidation of information.
Abstract: Clocks tick, bridges and skyscrapers vibrate, neuronal networks oscillate. Are neuronal oscillations an inevitable by-product, similar to bridge vibrations, or an essential part of the brain’s design? Mammalian cortical neurons form behavior-dependent oscillating networks of various sizes, which span five orders of magnitude in frequency. These oscillations are phylogenetically preserved, suggesting that they are functionally relevant. Recent findings indicate that network oscillations bias input selection, temporally link neurons into assemblies, and facilitate synaptic plasticity, mechanisms that cooperatively support temporal representation and long-term consolidation of information.

5,512 citations

Journal ArticleDOI
TL;DR: It is shown that rather general numerical constraints roughly determine the dimensions of memorizing models for the mammalian brain, and from these is derived a general model for archicortex.
Abstract: It is proposed that the most important characteristic of archicortex is its ability to perform a simple kind of memorizing task. It is shown that rather general numerical constraints roughly determine the dimensions of memorizing models for the mammalian brain, and from these is derived a general model for archicortex.

2,671 citations

Journal ArticleDOI
04 Jun 2009-Nature
TL;DR: Optogenetics opens the door to a new kind of informational analysis of brain function, permitting quantitative delineation of the functional significance of individual elements in the emergent operation and function of intact neural circuitry.
Abstract: Synchronized oscillations and inhibitory interneurons have important and interconnected roles within cortical microcircuits. In particular, interneurons defined by the fast-spiking phenotype and expression of the calcium-binding protein parvalbumin have been suggested to be involved in gamma (30-80 Hz) oscillations, which are hypothesized to enhance information processing. However, because parvalbumin interneurons cannot be selectively controlled, definitive tests of their functional significance in gamma oscillations, and quantitative assessment of the impact of parvalbumin interneurons and gamma oscillations on cortical circuits, have been lacking despite potentially enormous significance (for example, abnormalities in parvalbumin interneurons may underlie altered gamma-frequency synchronization and cognition in schizophrenia and autism). Here we use a panel of optogenetic technologies in mice to selectively modulate multiple distinct circuit elements in neocortex, alone or in combination. We find that inhibiting parvalbumin interneurons suppresses gamma oscillations in vivo, whereas driving these interneurons (even by means of non-rhythmic principal cell activity) is sufficient to generate emergent gamma-frequency rhythmicity. Moreover, gamma-frequency modulation of excitatory input in turn was found to enhance signal transmission in neocortex by reducing circuit noise and amplifying circuit signals, including inputs to parvalbumin interneurons. As demonstrated here, optogenetics opens the door to a new kind of informational analysis of brain function, permitting quantitative delineation of the functional significance of individual elements in the emergent operation and function of intact neural circuitry.

2,383 citations

Journal ArticleDOI
TL;DR: Experimental analysis in the hippocampus and the neocortex and computational analysis suggests that synaptic specialization turns interneuron networks into robust gamma frequency oscillators.
Abstract: Gamma frequency oscillations are thought to provide a temporal structure for information processing in the brain. They contribute to cognitive functions, such as memory formation and sensory processing, and are disturbed in some psychiatric disorders. Fast-spiking, parvalbumin-expressing, soma-inhibiting interneurons have a key role in the generation of these oscillations. Experimental analysis in the hippocampus and the neocortex reveals that synapses among these interneurons are highly specialized. Computational analysis further suggests that synaptic specialization turns interneuron networks into robust gamma frequency oscillators.

1,916 citations

Trending Questions (1)
Whate is the role of the dentate gyrus during trace conditioning?

The provided paper does not mention the role of the dentate gyrus during trace conditioning.