Search results for "hippocampal"
showing 10 items of 352 documents
Theta and gamma oscillations in the rat hippocampus during attentive lever pressing
2018
AbstractThe hippocampus is known to be pivotal for spatial memory but emerging evidence suggests its contribution to temporal memories as well. However, it is not clear how the hippocampus represents time and how it synchronizes spatial and temporal presentations into a coherent memory. We assessed the specific role of hippocampal theta and gamma oscillations and their interaction in short-term timing of motor reactions. Rats were trained to maintain lever pressing for 2.5 s and then to quickly release the lever and retrieve water reward from a nearby water port guided by a cue light. In essence, this task allows observation of hippocampal rhythms during timed anticipation when no overt mov…
An update to Hippocampome.org by integrating single-cell phenotypes with circuit function in vivo.
2021
Understanding brain operation demands linking basic behavioral traits to cell-type specific dynamics of different brain-wide subcircuits. This requires a system to classify the basic operational modes of neurons and circuits. Single-cell phenotyping of firing behavior during ongoing oscillations in vivo has provided a large body of evidence on entorhinal–hippocampal function, but data are dispersed and diverse. Here, we mined literature to search for information regarding the phase-timing dynamics of over 100 hippocampal/entorhinal neuron types defined in Hippocampome.org. We identified missing and unresolved pieces of knowledge (e.g., the preferred theta phase for a specific neuron type) a…
Coincident glutamatergic depolarizations enhance GABAA receptor-dependent Cl- influx in mature and suppress Cl- efflux in immature neurons.
2021
The impact of GABAergic transmission on neuronal excitability depends on the Cl--gradient across membranes. However, the Cl--fluxes through GABAA receptors alter the intracellular Cl- concentration ([Cl-]i) and in turn attenuate GABAergic responses, a process termed ionic plasticity. Recently it has been shown that coincident glutamatergic inputs significantly affect ionic plasticity. Yet how the [Cl-]i changes depend on the properties of glutamatergic inputs and their spatiotemporal relation to GABAergic stimuli is unknown. To investigate this issue, we used compartmental biophysical models of Cl- dynamics simulating either a simple ball-and-stick topology or a reconstructed CA3 neuron. Th…
Nigral influence on focal epilepsy.
1990
The substantia nigra (SN) has been proposed as a structure involved in epileptiform phenomena. Previous investigations demonstrated that SN is able to elicit hippocampal rhythmic slow activity (RSA) as well as to inhibit hippocampal interictal spikes induced by parenteral administration of penicillin. The present series of experiments was carried out in order to characterize the action of SN on a focal model of hippocampal epilepsy. Experiments were performed on encephale isole cats in which steady epileptiform activity was induced by locally applied penicillin. Electrical stimulation of SN pars reticulata (pr) caused a statistically significant decrease of hippocampal spike frequency and a…
A study of caudate inhibition on an epileptic focus in the cat hippocampus
1988
The mechanisms whereby the caudate nucleus modifies hippocampal spiking activity have been studied. Epileptiform activity was induced in the cat hippocampus by topical application of sodium penicillin in different concentrations. The frequency of induced spikes appeared to be directly correlated to the two doses of epileptogenic agent. The inhibitory effect of 10 Hz caudate stimulation on spike frequency was present even when stimulation lasted for 180 s. Likewise 25 Hz caudate stimulation brought about an inhibition which was maintained by stimulus trains lasting up to 90 s, while the degree of inhibition was reduced by trains of longer duration (120, 150 and 180 s); similar results were a…
Negative occurrence between hippocampal rhythmic slow activity and epileptiform spikes: Influence of the striatum
1986
AbstractThe effects of caudate and septal stimulation on hippocampal activity were studied. Sodium penicillin was intravenously injected in order to induce a steady rate of in-terictal epileptic activity. Penicillin injection caused significant reduction of the rate of occurrence and duration of hippocampal rhythmic slow activity (RSA). Spontaneous RSA as well as RSA-eliciting caudate and septal stimulation induced a marked inhibition on frequency of epileptiform complexes. Lesions of the medial septal nucleus made it impossible to record RSA or to observe any sort of influence on hippocampal epileptiform activity by caudate stimulation. This result suggests that the septum is important for…
The oscillatory profile induced by the anxiogenic drug fg-7142 in the amygdala-hippocampal network is reversed by infralimbic deep brain stimulation:…
2021
Anxiety and depression exhibit high comorbidity and share the alteration of the amygdala-hippocampal-prefrontal network, playing different roles in the ventral and dorsal hippocampi. Deep brain stimulation of the infralimbic cortex in rodents or the human equivalent-the subgenual cingulate cortex-constitutes a fast antidepressant treatment. The aim of this work was: (1) to describe the oscillatory profile in a rodent model of anxiety, and (2) to deepen the therapeutic basis of infralimbic deep brain stimulation in mood disorders. First, the anxiogenic drug FG-7142 was administered to anaesthetized rats to characterize neural oscillations within the amygdala and the dorsoventral axis of the …
Synaptic release of zinc from brain slices: factors governing release, imaging, and accurate calculation of concentration.
2006
Cerebrocortical neurons that store and release zinc synaptically are widely recognized as critical in maintenance of cortical excitability and in certain forms of brain injury and disease. Through the last 20 years, this synaptic release has been observed directly or indirectly and reported in more than a score of publications from over a dozen laboratories in eight countries. However, the concentration of zinc released synaptically has not been established with final certainty. In the present work we have considered six aspects of the methods for studying release that can affect the magnitude of zinc release, the imaging of the release, and the calculated concentration of released zinc. We…
Hippocampal reversible lesions in a case of transient global amnesia
2018
We report the case of 55-year-old man that after an emotional stress showed retrograde and anterograde amnesia with impairment of orientation in space and time but undisturbed consciousness. A neurological examination excluded other neurological signs or symptoms. The amnesic syndrome resolved spontaneously within 24 hours and the hypothesis of transient global amnesia was placed. Brain CT scan and conventional MRI sequences did not show any relevant pathological findings but diffusion-weighted imaging (DWI) showed two millimetric bright spot of restricted diffusion in the right hippocampus; in a brain MRI follow-up those findings were no more appreciable. The diagnosis of transient global …
Enhanced habit-based learning and decreased neurogenesis in the adult hippocampus in a murine model of chronic social stress
2009
Abstract Stress can induce preferential engagement of habit learning mediated by the basal ganglia, relative to learning that involves complex spatial associations contributed by the hippocampal formation. We explored in mice the influence that chronic episodes of social stress exert on the selection of cognitive/spatial vs. habit-based learning strategies. Male mice were exposed to repeated episodes of social confrontation and were categorized as dominant, subordinate or undetermined according to quantitative ethologically relevant parameters of aggression. Mice were then trained in a conditional discrimination task in the T-maze in the presence of allocentric cues until five correct choic…