Hippocampal Theta Cells Research Articles

Construction of the rat brain spatial cell firing model on a quadruped robot

Physiological studies have shown that rats in a dark environment rely on the limbs and vestibule for their self-motion information, which can maintain the specific firing patterns of grid cells and hippocampal CA3 place cells. In the development stage of rats, grid cells are considered to come from place cells, and place cells can be encoded by hippocampal theta cells. Based on these, the quadruped robot is used as a platform in this paper. Firstly, the sensing information of the robot's limbs and inertial measurement unit is obtained to solve its position in the environment. Then the position information is encoded by theta cells and mapped to place cells through a neural network. After obtaining the place cells with single-peak firing fields, Hebb learning is used to adjust the connection weight of the neural network between place cells and grid cells. In order to verify the model, 3-D simulation experiments are designed in this paper. The experiment results show that with the robot exploring in space, the spatial cells firing effects obtained by the model are consistent with the physiological research facts, which lay the foundation for the bionic environmental cognition model.

Medial septum regulates the hippocampal spatial representation.

The hippocampal circuitry undergoes attentional modulation by the cholinergic medial septum. However, it is unclear how septal activation regulates the spatial properties of hippocampal neurons. We investigated here what is the functional effect of selective-cholinergic and non-selective septal stimulation on septo-hippocampal system. We show for the first time selective activation of cholinergic cells and their differential network effect in medial septum of freely-behaving transgenic rats. Our data show that depolarization of cholinergic septal neurons evokes frequency-dependent response from the non-cholinergic septal neurons and hippocampal interneurons. Our findings provide vital evidence that cholinergic effect on septo-hippocampal axis is behavior-dependent. During the active behavioral state the activation of septal cholinergic projections is insufficient to evoke significant change in the spiking of the hippocampal neurons. The efficiency of septo-hippocampal processing during active exploration relates to the firing patterns of the non-cholinergic theta-bursting cells. Non-selective septal theta-burst stimulation resets the spiking of hippocampal theta cells, increases theta synchronization, entrains the spiking of hippocampal place cells, and tunes the spatial properties in a timing-dependent manner. The spatial properties are augmented only when the stimulation is applied in the periphery of the place field or 400–650 ms before the animals approached the center of the field. In summary, our data show that selective cholinergic activation triggers a robust network effect in the septo-hippocampal system during inactive behavioral state, whereas the non-cholinergic septal activation regulates hippocampal functional properties during explorative behavior. Together, our findings uncover fast septal modulation on hippocampal network and reveal how septal inputs up-regulate and down-regulate the encoding of spatial representation.

Simultaneous single-cell recording and microdialysis within the same brain site in freely behaving rats: a novel neurobiological method

We present a method for performing intracerebral microdialysis in freely behaving rats while recording the firing of neurons within the dialysis site. Studying hippocampal theta cells and complex-spike cells with this technique, it has been found that: (1) when the microdialysis fluid contained only artificial cerebrospinal fluid, both types of neurons displayed normal electrical activity, (2) the simultaneous single-cell recording/microdialysis procedure could be readily performed for as long as 3 days, and (3) inclusion of drugs into the microdialysis fluid, at appropriate concentrations, caused clear changes in firing pattern. For example, microdialysis with 1% lidocaine completely abolished, whereas that with 50 mM K + markedly increased, the neuronal electrical activity. These cellular changes developed without apparent EEG or behavioral manifestations and were reversible. In some of the experiments, the extracellular concentrations of glutamate and aspartate in the recording/dialysis site were also measured. The described method allows the extracellular environment of recorded brain cells to be manipulated by drugs delivered through the microdialysis probe and simultaneously allows determination of the neurochemical composition of that environment over a remarkably long period of time and in intact, physiologically functioning, neural networks. Such studies will provide new insights into the molecular basis of neuronal activity in the brain in the context of behavior, including learning.

Differential effects of age on subpopulations of hippocampal theta cells

The possible contribution of age-related changes in the firing properties of hippocampal theta cells to spatial learning deficits was addressed in the present study. The behavioral correlates of theta cells in strata oriens, pyramidale, and granulosum were compared as young and old rats performed a radial maze spatial working memory task. Behaviorally, the old animals made significantly more errors on the maze and required more time to solve the task than did young animals. Firing rates were compared in four different locomotion states: still, running radially inward and radially outward, and forwadd motion. The discharge rates of theta cells in strata pyramidale and granulosum were significantly modulated by these movements in both age groups. Stratum oriens theta cells recorded from young animals, on the other hand, were not movement-sensitive, while similar cells from old animals demonstrated exaggerated responses to movement. In old animals, the mean discharge rates were higher in stratum granulosum and lower in stratum oriens than in the young rats. The discharge rates of cells in stratum pyramidale did not differ between age groups. These region specific changes in the firing characteristics of hippocampal theta cells are likely to have important consequences for information processing in this structure.

Effects of atropine on hippocampal theta cells and complex-spike cells

The medial septal nuclei are essential for the naturally occuring hippocampal theta rhythm. Evidence that the rhythmic activity of the septum is carried via cholinergic afferents to the hippocampus has been: (a) the existence of a cholinergic septo-hippocampal projection, and (b) the sensitivity of one type of theta rhythm to antimuscaranic agents or cholinergic depletion. The muscarinic action of acetylcholine on pyramidal cells, however, is too slow to carry even a 4 Hz signal. Recent in vitro studies have confirmed a fast excitatory response by some hippocampal interneurons to muscarinic agonists. In urethane anesthetized rats, iontophoretic application of atropine to 17 hippocampal theta cells (presumed interneurons) during the theta rhythm, reduced their firing rates to an average of 24% of control rates. The effect of iontophoretic atropine application to 4 CA1 complex-spike cells (presumed pyramidal cells) was a selective elimination of their bursting activity with no significant effect on overall firing rate. The data suggest that: (1) interneuronal firing, during the hippocampal theta rhythm, is dominated by an excitatory cholinergic input and not by exctatory collaterals of pyramidal cells; (2) somatic burst firing by CA1 pyramidal cells requires the presence of acetylcholine.

Spatial firing properties of hippocampal theta cells

Previous studies have shown that complex-spike cells, the most common cell type recorded in the hippocampus of freely moving rats, have the property of spatial firing--that is, a cell will fire rapidly only when the animal is in a particular part of its environment (O'Keefe and Dostrovsky, 1971). In the current study, we analyze the spatial firing of theta cells, the second major class of cells in the hippocampus, which are thought to correspond to nonpyramidal neurons (Fox and Ranck, 1975, 1981). Our purposes were to extend findings from earlier spatial analyses (McNaughton et al., 1983; Christian and Deadwyler, 1986), and to determine whether the spatial firing is cell specific and independent of behavior. Theta cells were recorded from rats in a cylindrical enclosure using techniques previously used for the analysis of spatial firing in complex-spike cells (Muller et al., 1987). The spatial firing patterns of individual neurons appeared as a complex surface with several regions of high and low firing. The ratio of firing from high- to low-rate regions averaged 2.5. These spatial firing patterns were smooth and reproducible, but less so than for complex-spike cells. When a cue card on the wall was moved, theta cell firing patterns remained in register with the cue. Two analyses were performed to determine whether spatial firing patterns were secondary to spatial distributions of behavior. When only locomotor data segments were selected, spatial variations were more clear-cut. In an attempt to test whether theta cells had cell-specific patterns of firing, pairs of theta cells were recorded simultaneously. On all occasions, the firing distribution for each of the cells in a pair was clearly distinctive. These findings support the conclusions that theta cell activity contains a spatial signal that is cell specific and not secondary to other firing correlates.

Fluctuations in spontaneous discharge of hippocampal theta cells during sleep-waking states and PCPA-induced insomnia.

1. The spontaneous activity of hippocampal theta cells in head-restrained cats was recorded during slow-wave sleep (SWS), paradoxical sleep (PS), and the attentive state of bird watching (BW). We also recorded theta cell activity during a state of insomnia with pontogeniculoocipital (PGO) waves, which was induced by the administration of p-chlorophenylalanine (PCPA), a selective inhibitor of serotonin synthesis. 2. The time-dependent structure of fluctuations in theta cell activity was evaluated by power spectral analysis and Markovian analysis. The coefficient of variation for these time series was used as a measure of the variability of theta cell activity, which indicates the relative amplitude of fluctuations. 3. During SWS, theta cell activity showed a larger variability and a flat spectrum, i.e., low Markovian properties. During PS, this activity exhibited smaller variability and high spectral density in a low-frequency band (0.01-1.0 Hz), i.e., high Markovian properties. During BW, variability, spectral and Markovian properties were intermediate. 4. The firing pattern of theta cells during PCPA-induced insomnia was similar to that during PS. However, after the administration of either a serotonin agonist, 5-Methoxy-N,N-dimethyltryptamine, or a choline antagonist, atropine sulfate, theta cell activity no longer exhibited PS-like fluctuations, revealing instead a firing pattern similar to that during SWS. 5. During PS and PCPA-induced insomnia, not only the unit activity of theta cells, but PGO activity and theta wave frequency exhibited slow fluctuations, i.e., the high spectral density in the low-frequency band (0.01-1.0 Hz). 6. Cross-correlation analyses were performed between the fluctuations in theta cell activity, theta wave frequency, and PGO activity. These fluctuations correlated with each other during both PS and PCPA-induced insomnia. Bursts of PGO waves especially contributed to these cross-correlations. 7. These results suggest, first, that the slow fluctuations of the theta cell activity during PS and PCPA-induced insomnia is the physiological expression of the removal of aminergic influences and, secondly, that they are dependent on cholinergic mechanisms, including PGO generators.

Medial septal modulation of hippocampal theta cell discharges

The effect of small electrolytic lesions in various areas of the septum on the behavioral correlates and firing repertoires of hippocampal theta cells, was investigated in the freely moving rabbit. Lesions localized to the medial septum were found to abolish both slow wave theta and the rhythmic firing of CA1 and dentate layer theta cells, in both the type 1 theta (movement) and type 2 theta (sensory processing) behavior conditions. Small lesions of the diagonal band, lateral septum and fimbria/fornix regions only affected rhythmicity to the extent that they also involved the medial septal region. The same medial septal lesions that abolished rhythmicity were also shown to reduce the mean discharge rate of theta cells occurring during the type 1 movement condition by approximately 50%, while the discharge rate occurring during the type 2 sensory processing condition did not change significantly. Behavioral changes were also only observed for lesions involving the medial septum. The importance of afferent input from the medial septum in the generation of hippocampal theta cell rhythmicity was discussed.

The pharmacology of hippocampal theta cells: Evidence that the sensory processing correlate is cholinergic

The firing repertoires of theta cells in the CA1 and dentate layers of the hippocampal formation of the freely moving rabbit were analyzed during 3 behavioral conditions: (1) voluntary motor patterns, termed type 1 theta behaviors; (2) automatic motor patterns, termed type 2 LIA behaviors; (3) alert immobility with presentation of sensory stimuli, termed type 2 theta behavior. Cholinergic manipulations were shown to effect the firing repertoires of theta cells during the type 2 theta behavior condition (sensory processing) and not the other two behavioral conditions. A hypothesis of a sensorimotor processing function of the hippocampal formation is presented and discussed.

Theta-Cells in CA1 and dentate layers of hippocampal formation: relations to slow-wave activity and motor behavior in the freely moving rabbit.

theta-Cells in CA1 and dentate layers of hippocampal formation: relations to slow-wave activity and motor behavior in the freely moving rabbit.B R Sinclair, M G Seto, and B H BlandB R Sinclair, M G Seto, and B H BlandPublished Online:01 Nov 1982https://doi.org/10.1152/jn.1982.48.5.1214MoreSectionsPDF (2 MB)Download PDF ToolsExport citationAdd to favoritesGet permissionsTrack citations ShareShare onFacebookTwitterLinkedInWeChat Previous Back to Top Next Download PDF FiguresReferencesRelatedInformation Cited ByA new perspective of the hippocampus in the origin of exercise–brain interactions18 April 2018 | Brain Structure and Function, Vol. 223, No. 6Theta- and movement velocity-related firing of hippocampal neurons is disrupted by lesions centered on the perirhinal cortex6 January 2003 | Hippocampus, Vol. 13, No. 1Relationship Between Membrane Potential Oscillations and Rhythmic Discharges in Identified Hippocampal Theta-Related CellsBrian H. Bland, Jan Konopacki, and Richard H. Dyck1 December 2002 | Journal of Neurophysiology, Vol. 88, No. 6Cholecystokinin (CCK-8S) prolongs ‘unsaturated’ θ-pulse induced long-term potentiation in rat hippocampal CA1 in vitroNeuropeptides, Vol. 26, No. 6Extrinsic and intrinsic properties underlying oscillation and synchrony in limbic cortexProgress in Neurobiology, Vol. 41, No. 2Current source density analysis of the hippocampal theta rhythm: associated sustained potentials and candidate synaptic generatorsBrain Research, Vol. 615, No. 2Hippocampal plasticity during jaw movement conditioning in the rabbitBrain Research, Vol. 608, No. 1Relay stations and neurotransmitters between the pallidal region and the hippocampusElectroencephalography and Clinical Neurophysiology, Vol. 78, No. 4Effects of transient cerebral ischemia on the hippocampal dentate theta (θ) profile in the acute rat: a study 4–5 months following recirculationBrain Research, Vol. 508, No. 1Phase shifting of CA1 and dentate EEG theta rhythms in hippocampal formation slicesBrain Research, Vol. 417, No. 2Cross-correlation analysis of septohippocampal neurons during ≡-rhythmBrain Research, Vol. 413, No. 1Temporal changes in hippocampal theta activity following twenty minutes of forebrain ischemia in the chronic ratBrain Research, Vol. 378, No. 2Medial septal modulation of hippocampal theta cell dischargesBrain Research, Vol. 375, No. 1The physiology and pharmacology of hippocampal formation theta rhythmsProgress in Neurobiology, Vol. 26, No. 1Pathways through cingulate, neo-and entorhinal cortices mediate atropine-resistant hippocampal rhythmical slow activityBrain Research, Vol. 347, No. 1A digital sound editorComputers and Biomedical Research, Vol. 18, No. 5Single-cell activity and synchronous bursting in the rat hippocampus during waking behavior and sleepExperimental Neurology, Vol. 89, No. 1Hippocampal-dentate Θ disturbance after selective CA1 pyramidal cell damage in the ratBrain Research, Vol. 328, No. 2The pharmacology of hippocampal theta cells: Evidence that the sensory processing correlate is cholinergicBrain Research, Vol. 299, No. 1Extracellular fields influence transmembrane potentials and synchronization of hippocampal neuronal activityBrain Research, Vol. 294, No. 2Hippocampal excitability related to the phase of the theta rhythm in urethanized ratsBrain Research, Vol. 294, No. 2Interrelations between globus pallidus and hippocampal epilepsy in the cat ( 1 )26 September 2008 | Archives Internationales de Physiologie et de Biochimie, Vol. 92, No. 4Spectral analysis of hippocampal unit train in relation to hippocampal EEGElectroencephalography and Clinical Neurophysiology, Vol. 56, No. 6Cellular bases of hippocampal EEG in the behaving ratBrain Research Reviews, Vol. 6, No. 2The relation of mutliple hippocampal theta cell discharge rates to slow wave theta frequencyPhysiology & Behavior, Vol. 31, No. 1 More from this issue > Volume 48Issue 5November 1982Pages 1214-25 https://doi.org/10.1152/jn.1982.48.5.1214PubMed7175568History Published online 1 November 1982 Published in print 1 November 1982 Metrics

Direct afferent excitation and long-term potentiation of hippocampal interneurons.

Direct afferent excitation and long-term potentiation of hippocampal interneurons.