scholarly journals Silencing of hippocampal synaptic transmission impairs spatial reward search on a head-fixed tactile treadmill task

2021 ◽  
Author(s):  
Jake T. Jordan ◽  
J. Tiago Gonçalves
Keyword(s):  
Synaptic Transmission ◽  
Spatial Memory ◽  
Hippocampal Neurons ◽  
Designer Drugs ◽  
Spatial Cues ◽  
Place Fields ◽  
Local Cues

AbstractHead-fixed linear treadmill tasks have been used to study hippocampal physiology in mice. Although some hippocampal neurons establish place fields along linear treadmills, it is not clear if the hippocampus is required for spatial memory on this task. Using a Designer Receptors Exclusively Activated by Designer Drugs (DREADDs) approach, we found that silencing hippocampal output on rewarded treadmill tasks impaired search for rewards signaled by spatial cues but did not impair search for rewards signaled by local cues, recapitulating findings from other behavior tasks. These findings serve to contextualize data on hippocampal physiology from mice performing this task.

Task-Dependent Representations in Rat Hippocampal Place Neurons

1997 ◽  
Vol 78 (2) ◽  
pp. 597-613 ◽  
Author(s):  
Tsuneyuki Kobayashi ◽  
Hisao Nishijo ◽  
Masaji Fukuda ◽  
Jan Bures ◽  
Taketoshi Ono
Keyword(s):  
Open Field ◽  
Hippocampal Neurons ◽  
Hippocampal Formation ◽  
Movement Speed ◽  
Neuron Activity ◽  
Place Field ◽  
Complex Spike ◽  
Place Fields ◽  
Sequential Trials ◽  
Self Stimulation

Kobayashi, Tsuneyuki, Hisao Nishijo, Masaji Fukuda, Jan Bures, and Taketoshi Ono. Task-dependent representations in rat hippocampal place neurons. J. Neurophysiol. 78: 597–613, 1997. It is suggested that the hippocampal formation is essential to spatial representations by flexible encoding of diverse information during navigation, which includes not only externally generated sensory information such as visual and auditory sensation but also ideothetic information concerning locomotion (i.e., internally generated information such as proprioceptive and vestibular sensation) as well as information concerning reward. In the present study, we investigated how various types of information are represented in the hippocampal formation, by recording hippocampal complex-spike cells from rats that performed three types of place learning tasks in a circular open field with the use of intracranial self-stimulation as reward. The intracranial self-stimulation reward was delivered in the following three contexts: if the rat 1) entered an experimenter-determined reward place within the open field, and this place was randomly varied in sequential trials; 2) entered two specific places, one within and one outside the place field (an area identified by change in activity of a place neuron); or 3) entered an experimenter-specified place outside the place field. Because the behavioral trails during navigation were more constant in the second task than in the first task, ideothetic information concerning locomotion was more relevant to acquiring reward in the second task than in the first task. Of 43 complex-spike cells recorded, 37 displayed place fields under the first task. Of these 37 place neurons, 34 also had significant reward correlates only inside the place field. Although reward and place correlates of the place neuron activity did not change between the first and second tasks, neuronal correlates to behavioral variables for locomotion such as movement speed, direction, and turning angle significantly increased in the second task. Furthermore, 6 of 31 place neurons tested with the third task, in which the reward place was located outside the original place field, shifted place fields. The results indicated that neuronal correlates of most place neurons flexibly increased their sensitivity to relevant information in a given context and environment, and some place neurons changed the place field per se with place reward association. These results suggest two strategies for how hippocampal neurons incorporate an incredible variety of perceptions into a unified representation of the environment: through flexible use of information and the creation of new representations.

Two Mechanisms That Raise Free Intracellular Calcium in Rat Hippocampal Neurons During Hypoosmotic and Low NaCl Treatment

2000 ◽  
Vol 83 (1) ◽  
pp. 81-89 ◽  
Author(s):  
Aren J. Borgdorff ◽  
George G. Somjen ◽  
Wytse J. Wadman
Keyword(s):  
Synaptic Transmission ◽  
Intracellular Calcium ◽  
Hippocampal Neurons ◽  
Pyramidal Neurons ◽  
Hippocampal Slices ◽  
Cell Swelling ◽  
Tissue Slices ◽  
Extracellular Medium ◽  
Calcium Activity ◽  
Hippocampal Pyramidal Neurons

Previous studies have shown that exposing hippocampal slices to low osmolarity (πo) or to low extracellular NaCl concentration ([NaCl]o) enhances synaptic transmission and also causes interstitial calcium ([Ca2+]o) to decrease. Reduction of [Ca2+]o suggests cellular uptake and could explain the potentiation of synaptic transmission. We measured intracellular calcium activity ([Ca2+]i) using fluorescent indicator dyes. In CA1 hippocampal pyramidal neurons in tissue slices, lowering πo by ∼70 mOsm caused “resting” [Ca2+]i as well as synaptically or directly stimulated transient increases of calcium activity (Δ[Ca2+]i) to transiently decrease and then to increase. In dissociated cells, lowering πo by ∼70 mOsm caused [Ca2+]i to almost double on average from 83 to 155 nM. The increase of [Ca2+]i was not significantly correlated with hypotonic cell swelling. Isoosmotic (mannitol- or sucrose-substituted) lowering of [NaCl]o, which did not cause cell swelling, also raised [Ca2+]i. Substituting NaCl with choline-Cl or Na-methyl-sulfate did not affect [Ca2+]i. In neurons bathed in calcium-free medium, lowering πo caused a milder increase of [Ca2+]i, which was correlated with cell swelling, but in the absence of external Ca2+, isotonic lowering of [NaCl]o triggered only a brief, transient response. We conclude that decrease of extracellular ionic strength (i.e., in both low πo and low [NaCl]o) causes a net influx of Ca2+ from the extracellular medium whereas cell swelling, or the increase in membrane tension, is a signal for the release of Ca2+ from intracellular stores.

Hippocampal Place-Cell Firing During Movement in Three-Dimensional Space

2001 ◽  
Vol 85 (1) ◽  
pp. 105-116 ◽  
Author(s):  
James J. Knierim ◽  
Bruce L. McNaughton
Keyword(s):  
Hippocampal Neurons ◽  
Horizontal Plane ◽  
Three Dimensional ◽  
Place Cell ◽  
Place Cells ◽  
Limbic Cortex ◽  
Head Direction ◽  
Head Direction Cells ◽  
Recording Apparatus ◽  
Place Fields

“Place” cells of the rat hippocampus are coupled to “head direction” cells of the thalamus and limbic cortex. Head direction cells are sensitive to head direction in the horizontal plane only, which leads to the question of whether place cells similarly encode locations in the horizontal plane only, ignoring the z axis, or whether they encode locations in three dimensions. This question was addressed by recording from ensembles of CA1 pyramidal cells while rats traversed a rectangular track that could be tilted and rotated to different three-dimensional orientations. Cells were analyzed to determine whether their firing was bound to the external, three-dimensional cues of the environment, to the two-dimensional rectangular surface, or to some combination of these cues. Tilting the track 45° generally provoked a partial remapping of the rectangular surface in that some cells maintained their place fields, whereas other cells either gained new place fields, lost existing fields, or changed their firing locations arbitrarily. When the tilted track was rotated relative to the distal landmarks, most place fields remapped, but a number of cells maintained the same place field relative to the x-y coordinate frame of the laboratory, ignoring the z axis. No more cells were bound to the local reference frame of the recording apparatus than would be predicted by chance. The partial remapping demonstrated that the place cell system was sensitive to the three-dimensional manipulations of the recording apparatus. Nonetheless the results were not consistent with an explicit three-dimensional tuning of individual hippocampal neurons nor were they consistent with a model in which different sets of cells are tightly coupled to different sets of environmental cues. The results are most consistent with the statement that hippocampal neurons can change their “tuning functions” in arbitrary ways when features of the sensory input or behavioral context are altered. Understanding the rules that govern the remapping phenomenon holds promise for deciphering the neural circuitry underlying hippocampal function.

scholarly journals Effect of chemogenetic modulation of hippocampal neurons on depression and spatial memory impairment in a rat model for temporal lobe epilepsy.

2019 ◽  
Vol 13 ◽  
Author(s):  
Erine Craey ◽  
Marie-Gabrielle Goossens ◽  
Jana Desloovere ◽  
Caroline Merckx ◽  
Chris Van Den Haute ◽  
...  
Keyword(s):  
Temporal Lobe Epilepsy ◽  
Spatial Memory ◽  
Temporal Lobe ◽  
Rat Model ◽  
Hippocampal Neurons ◽  
Memory Impairment

scholarly journals Latent learning drives sleep-dependent plasticity in distinct CA1 subpopulations

2020 ◽  
Author(s):  
Wei Guo ◽  
Jie J. Zhang ◽  
Jonathan P. Newman ◽  
Matthew A. Wilson
Keyword(s):  
Hippocampal Neurons ◽  
Dimensional Manifold ◽  
Latent Learning ◽  
Neural Ensembles ◽  
Correlated Activity ◽  
Place Fields ◽  
Internal States ◽  
Low Dimensional ◽  
Low Dimensional Manifold ◽  
The Brain

AbstractLatent learning allows the brain the transform experiences into cognitive maps, a form of implicit memory, without reinforced training. Its mechanism is unclear. We tracked the internal states of the hippocampal neural ensembles and discovered that during latent learning of a spatial map, the state space evolved into a low-dimensional manifold that topologically resembled the physical environment. This process requires repeated experiences and sleep in-between. Further investigations revealed that a subset of hippocampal neurons, instead of rapidly forming place fields in a novel environment, remained weakly tuned but gradually developed correlated activity with other neurons. These ‘weakly spatial’ neurons bond activity of neurons with stronger spatial tuning, linking discrete place fields into a map that supports flexible navigation.

scholarly journals The Dose-dependent Dual Effects of Corticosterone on Spatial Memory Ability After Traumatic Brain Injury Are Mediated by Two Corticosteroid Receptor Systems

2021 ◽  
Author(s):  
Bin Zhang ◽  
Mengshi Yang ◽  
Qiongyu Yan ◽  
Xiaojian Xu ◽  
Fei Niu ◽  
...  
Keyword(s):  
Traumatic Brain Injury ◽  
Brain Injury ◽  
Spatial Memory ◽  
Signaling Pathways ◽  
Hippocampal Neurons ◽  
High Dose ◽  
Short Term ◽  
Memory Ability ◽  
Neurotoxic Effects ◽  
Dose Dependent

Abstract Background: Our recent studies reported the opposite effects of mineralocorticoid receptor (MR) and glucocorticoid receptor (GR) on neuron survival after traumatic brain injury (TBI). However, as a mixed agonist for MR and GR, whether short term use of high-dose endogenous glucocorticoids exerts neurotoxic effects by excessive activation of GR, what is the set-point, and the possible signaling pathways remain unclear. This study examined the dose-dependent dual effects of corticosterone (CORT) on the spatial memory, the survival of hippocampal neurons and the possible receptor-mediated downstream signaling pathways after TBI.Methods: Based on controlled cortical impact (CCI) and CORT treatments, Sprague-Dawley rats (n=168) were randomly divided into the sham, CCI, CCI + CORT1 (0.3 mg/kg), CCI + CORT2 (3 mg/kg), CCI + CORT3 (30 mg/kg), CCI + CORT1 + spirolactone (spirolactone: 50 mg/kg/d), and CCI + CORT3 + RU486 (RU486: 50 mg/kg/d) groups. Brain tissues were collected on postinjury day 3 and processed for histology and western blot analysis.Results: On postinjury day 3, we tested the learning and memory ability, neuronal apoptosis in the hippocampus, activation levels of MR and GR, Bcl-2 family proteins, and apoptosis-related intracellular signaling pathways. We found that different doses of CORT exhibited dual effects on the survival of hippocampal neurons and the spatial memory. Lower doses of CORT (0.3, 3 mg/kg) significantly increased the activation of MR, upregulated the phosphorylation of Akt/CREB/Bad and the Bcl-2 expression, reduced the number of apoptotic neurons, and subsequently improved the spatial memory. In contrast, higher dose of CORT (30 mg/kg) exerted opposite effect by over activating GR, upregulating the expressions of P53/Bax, and inhibiting the Erk/CREB activities. Conclusion: The results suggest that there is a threshold between the neuroprotective and neurotoxic effects of endogenous GC, higher dose of which, even for short-term use, should also be avoided after TBI.

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