scholarly journals Population and Individual Firing Behaviors in Sparsely Synchronized Rhythms in The Hippocampal Dentate Gyrus

2021 ◽  
Author(s):  
Sang-Yoon Kim ◽  
Woochang Lim
Keyword(s):  
Dentate Gyrus ◽  
Granule Cells ◽  
Phase Locking ◽  
Random Phase ◽  
Firing Activity ◽  
Hippocampal Dentate Gyrus ◽  
Population Frequency ◽  
Mossy Cells ◽  
Winner Take All ◽  
Take All

We investigate population and individual firing behaviors in sparsely synchronized rhythms (SSRs) in a spiking neural network of the hippocampal dentate gyrus (DG). The main encoding granule cells (GCs) are grouped into lamellar clusters. In each GC cluster, there is one inhibitory (I) basket cell (BC) along with excitatory (E) GCs, and they form the E-I loop. Winner-take-all competition, leading to sparse activation of the GCs, occurs in each GC cluster. Such sparsity has been thought to enhance pattern separation performed in the DG. During the winner-take-all competition, SSRs are found to appear in each population of the GCs and the BCs through interaction of excitation of the GCs with inhibition of the BCs. Sparsely synchronized spiking stripes appear successively with the population frequency fp (= 13 Hz) in the raster plots of spikes. We also note that excitatory hilar mossy cells (MCs) control the firing activity of the GC-BC loop by providing excitation to both the GCs and the BCs. SSR also appears in the population of MCs via interaction with the GCs (i.e., GC-MC loop). Population behaviors in the SSRs are quantitatively characterized in terms of the synchronization measures. In addition, we investigate individual firing activity of GCs, BCs, and MCs in the SSRs. Individual GCs exhibit random spike skipping, leading to a multi-peaked inter-spike-interval histogram, which is well characterized in terms of the random phase-locking degree. In this case, population-averaged mean-firing-rate (MFR) <fi(GC)> is less than the population frequency fp. On the other hand, both BCs and MCs show "intrastripe" burstings within stripes, together with "interstripe" random spike skipping. Thus, the population-averaged MFR <fi(X)> (X= MC and BC) is larger than fp, in contrast to the case of the GCs. MC loss may occur during epileptogenesis. With decreasing the fraction of the MCs, changes in the population and individual firings in the SSRs are also studied. Finally, quantitative association between the population/individual firing behaviors in the SSRs and the winner-take-all competition is discussed.

scholarly journals Disynaptic Effect of Hilar Cells on Pattern Separation in A Spiking Neural Network of Hippocampal Dentate Gyrus

2021 ◽  
Author(s):  
Sang-Yoon Kim ◽  
Woochang Lim
Keyword(s):  
Neural Network ◽  
Dentate Gyrus ◽  
Phase Locking ◽  
Random Phase ◽  
The Other ◽  
Pattern Separation ◽  
Spiking Neural Network ◽  
Hippocampal Dentate Gyrus ◽  
Other Hand ◽  
Separation Degree

We investigate the disynaptic effect of the hilar cells on pattern separation in a spiking neural network of the hippocampal dentate gyrus (DG). The principal granule cells (GCs) in the DG perform pattern separation, transforming similar input patterns into less-similar output patterns. In our DG network, the hilus consists of excitatory mossy cells (MCs) and inhibitory HIPP (hilar perforant path-associated) cells. Here, we consider the disynaptic effects of the MCs and the HIPP cells on the GCs, mediated by the inhibitory basket cells (BCs) in the granular layer; MC → BC → GC and HIPP → BC → GC. Disynaptic inhibition from the MCs tends to decrease the firing activity of the GCs. On the other hand, the HIPP cells disinhibit the intermediate BCs, which leads to increasing the activity of the GCs. By changing the synaptic strength K(BC, X) [from the presynaptic X (= MC or HIPP) to the postsynaptic BC] from the default value K(BC, X)*, we study the change in the pattern separation degree Sd. When decreasing K(BC, MC) or independently increasing K(BC, HIPP) from their default values, Sd is found to decrease (i.e., pattern separation is reduced). On the other hand, as K(BC, MC) is increased or independently K(BC, HIPP) is decreased from their default values, pattern separation becomes enhanced (i.e., Sd increases). In this way, the disynaptic effects of the MCs and the HIPP cells on the pattern separation are opposite ones. Thus, when simultaneously varying both K(BC, MC) and K(BC, HIPP), as a result of balance between the two competing disynaptic effects of the MCs and the HIPP cells, Sd forms a bell-shaped curve with an optimal maximum at their default values. Moreover, we also investigate population and individual behaviors of the sparsely synchronized rhythm of the GCs, and find that the amplitude measure Ma (representing population synchronization degree) and the random-phase-locking degree Ld (denoting individual activity degree) are strongly correlated with the pattern separation degree Sd. Consequently, the larger the synchronization and the random phase-locking degrees of the sparsely synchronized rhythm is, the more the pattern separation becomes enhanced.

Survival of mossy cells of the hippocampal dentate gyrus in humans with mesial temporal lobe epilepsy

2009 ◽  
Vol 111 (6) ◽  
pp. 1237-1247 ◽  
Author(s):  
László Seress ◽  
Hajnalka Ábrahám ◽  
Zsolt Horváth ◽  
Tamás Dóczi ◽  
József Janszky ◽  
...  
Keyword(s):  
Temporal Lobe Epilepsy ◽  
Dentate Gyrus ◽  
Temporal Lobe ◽  
Pyramidal Neurons ◽  
Hippocampal Sclerosis ◽  
Mesial Temporal Lobe Epilepsy ◽  
Drug Resistant ◽  
Hippocampal Dentate Gyrus ◽  
Mossy Cells ◽  
Mesial Temporal Lobe

Object Hippocampal sclerosis can be identified in most patients with mesial temporal lobe epilepsy (TLE). Surgical removal of the sclerotic hippocampus is widely performed to treat patients with drug-resistant mesial TLE. In general, both epilepsy-prone and epilepsy-resistant neurons are believed to be in the hippocampal formation. The hilar mossy cells of the hippocampal dentate gyrus are usually considered one of the most vulnerable types of neurons. The aim of this study was to clarify the fate of mossy cells in the hippocampus in epileptic humans. Methods Of the 19 patients included in this study, 15 underwent temporal lobe resection because of drug-resistant TLE. Four patients were used as controls because they harbored tumors that had not invaded the hippocampus and they had experienced no seizures. Histological evaluation of resected hippocampal tissues was performed using immunohistochemistry. Results Mossy cells were identified in the control as well as the epileptic hippocampi by using cocaine- and amphetamine-regulated transcript peptide immunohistochemistry. In most cases the number of mossy cells was reduced and thorny excrescences were smaller in the epileptic hippocampi than in controls; however, there was a significant loss of pyramidal cells and a partial loss of granule cells in the same epileptic hippocampi in which mossy cell loss was apparent. The loss of mossy cells could be correlated with the extent of hippocampal sclerosis, patient age at seizure onset, duration of epilepsy, and frequency of seizures. Conclusions In many cases large numbers of mossy cells were present in the hilus of the dentate gyrus when most pyramidal neurons of the CA1 and CA3 areas of the Ammon's horn were lost, suggesting that mossy cells may not be more vulnerable to epileptic seizures than the hippocampal pyramidal neurons.

scholarly journals Substance P Enhances NMDA Channel Function in Hippocampal Dentate Gyrus Granule Cells

1998 ◽  
Vol 80 (1) ◽  
pp. 113-119 ◽  
Author(s):  
David N. Lieberman ◽  
Istvan Mody
Keyword(s):  
Substance P ◽  
Dentate Gyrus ◽  
Granule Cells ◽  
Excitatory Amino Acid ◽  
Calcium Influx ◽  
Network Activity ◽  
Hippocampal Dentate Gyrus ◽  
Adult Rat ◽  
Channel Function ◽  
Nmda Channel

Lieberman, David N. and Istvan Mody. Substance P enhances NMDA channel function in hippocampal dentate gyrus granule cells. J. Neurophysiol. 80: 113–119, 1998. Substance P (SP)–containing afferents and the NK-1 tachykinin receptor to which SP binds are present in the dentate gyrus of the rat; however, direct actions of SP on principal cells have not been demonstrated in this brain region. We have examined the effect of SP on N-methyl-d-aspartate (NMDA) channels from acutely isolated dentate gyrus granule cells of adult rat hippocampus to assess the ability of SP to regulate glutamatergic input. SP produces a robust enhancement of single NMDA channel function that is mimicked by the NK-1–selective agonist Sar9, Met(O2)11-SP. The SP-induced prolongation of NMDA channel openings is prevented by the selective NK-1 receptor antagonist (+)-(2 S,3 S)-3-(2-methoxybenzylamino)-2-phenylpiperidine (CP-99,994). Calcium influx or activation of protein kinase C were not required for the SP-induced increase in NMDA channel open durations. The dramatic enhancement of excitatory amino acid–mediated excitability by SP places this neuropeptide in a key position to gate activation of hippocampal network activity.

scholarly journals Spatial Representations of Granule Cells and Mossy Cells of the Dentate Gyrus

Neuron ◽  
2017 ◽  
Vol 93 (3) ◽  
pp. 677-690.e5 ◽  
Author(s):  
Douglas GoodSmith ◽  
Xiaojing Chen ◽  
Cheng Wang ◽  
Sang Hoon Kim ◽  
Hongjun Song ◽  
...  
Keyword(s):  
Dentate Gyrus ◽  
Granule Cells ◽  
Spatial Representations ◽  
Mossy Cells

scholarly journals Bidirectional regulation of cognitive and anxiety-like behaviors by dentate gyrus mossy cells in male and female mice

2020 ◽  
Author(s):  
Justin J Botterill ◽  
K Yaragudri Vinod ◽  
Kathleen J Gerencer ◽  
Cátia M Teixeira ◽  
John J LaFrancois ◽  
...  
Keyword(s):  
Dentate Gyrus ◽  
Cognitive Performance ◽  
Granule Cells ◽  
Gabaergic Neurons ◽  
Designer Drugs ◽  
Early Gene ◽  
Loss Of Function ◽  
Cell Type ◽  
Mossy Cells ◽  
Bidirectional Regulation

ABSTRACTThe dentate gyrus (DG) of the hippocampus is important for cognitive and affective behaviors. However, the circuits underlying these behaviors are unclear. DG mossy cells (MCs) have been a focus of attention because of their excitatory synapses on the primary DG cell type, granule cells (GCs). However, MCs also activate DG GABAergic neurons which inhibit GCs. We took advantage of specific methods and a gain- and loss-of function strategy with Designer Receptors Exclusively Activated by Designer Drugs (DREADDs) to study MCs in diverse behaviors. Using this approach, manipulations of MCs could bidirectionally regulate behavior. The results suggest that inhibiting MCs can reduce anxiety-like behavior and improve cognitive performance. However, not all cognitive or anxiety-related behaviors were influenced, suggesting specific roles of MCs in some but not all types of cognition and anxiety. Notably, several behaviors showed sex-specific effects, with females often showing more pronounced effects than the males. We also used the immediate early gene c-Fos to address whether DREADDs bidirectionally regulated MC or GC activity. We confirmed excitatory DREADDs increased MC c-Fos. However, there was no change in GC c-Fos, consistent with MC activation leading to GABAergic inhibition of GCs. In contrast, inhibitory DREADDs led to a large increase in GC c-Fos, consistent with a reduction in MC excitation of GABAergic neurons, and reduced inhibition of GCs. Taken together, these results suggest that MCs regulate anxiety and cognition in specific ways. We also raise the possibility that cognitive performance may be improved by reducing anxiety.SIGNIFICANCE STATEMENTThe dentate gyrus (DG) has many important cognitive roles as well as being associated with affective behavior. This study addressed how a glutamatergic DG cell type called mossy cells (MCs) contributes to diverse behaviors, which is timely because it is known that MCs regulate the activity of the primary DG cell type, granule cells (GCs), but how MC activity influences behavior is unclear. We show, surprisingly, that activating MCs can lead to adverse behavioral outcomes, and inhibiting MCs have an opposite effect. Importantly, the results appeared to be task-dependent and showed that testing both sexes was important. Additional experiments indicated what MC and GC circuitry was involved. Taken together, the results suggest how MCs influence behaviors that involve the DG.

scholarly journals Dentate Gyrus Mossy Cells Share a Role in Pattern Separation with Dentate Granule Cells and Proximal CA3 Pyramidal Cells

2019 ◽  
Vol 39 (48) ◽  
pp. 9570-9584 ◽  
Author(s):  
Douglas GoodSmith ◽  
Heekyung Lee ◽  
Joshua P. Neunuebel ◽  
Hongjun Song ◽  
James J. Knierim
Keyword(s):  
Dentate Gyrus ◽  
Granule Cells ◽  
Pyramidal Cells ◽  
Pattern Separation ◽  
Dentate Granule Cells ◽  
Mossy Cells ◽  
Ca3 Pyramidal Cells
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