Sensitization and hippocampal type 2 theta in the rat

Sainsbury, Robert S.; Harris, Jill L.; Rowland, Guy L.

doi:10.1016/0031-9384(87)90085-0

Cited by 40 publications

(21 citation statements)

References 13 publications

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“…Overall, ATN spectral power revealed no correlation between FP slope and low T-ratio, and a significant positive correlation between FP parameters and high T-ratio. The observed result could be related to the physiological role of the ascending flow of Papez's circuit to mediate motion-dependent theta, in which values fall within a range of 8-12 Hz (high theta) (Bland et al, 1984;Bland, 1986;Sainsbury et al, 1987).…”

Section: Discussionmentioning

confidence: 87%

“…The first step in exploring this hypothesis is to compare the effect of fornix and mammillothalamic fiber activation on thalamic theta oscillation, an issue addressed in this paper. Theta rhythm can be subdivided into two types: the first is dependent on motor activity and falls within a range of 8-12 Hz (high theta), while the second type consists of a slightly lower frequency (4-8 Hz, slow theta) and is dependent on the release of acetylcholine into the hippocampus from the septum (Bland et al, 1984;Bland, 1986;Sainsbury et al, 1987). The medial septum is commonly accepted as the pacemaker of theta in the limbic system (Brazhnik and Vinogradova, 1986), and inactivation of medial septum abolishes theta rhythmic discharge in hippocampus and mammillary bodies (Kirk et al, 1996).…”

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confidence: 99%

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Hippocampal inputs mediate theta-related plasticity in anterior thalamus

et al. 2011

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Hippocampally-driven oscillatory activity at theta frequency is found in the diencephalon, but an understanding of the fundamental role of theta in the hippocampo-diencephalic circuit remains elusive. An important strategy in determining how activity modifies oscillatory properties of hippocampo-diencephalic circuitry comprises investigations of anterior thalamic responses to their main inputs: the descending dorsal fornix and the ascending mammillothalamic tract. Here, we show that the amplitude of thalamic theta spectral power selectively increases after plasticityinducing stimulation of the dorsal fornix, but not of the mammillothalamic tract in urethaneanaesthetized young male rats. Furthermore, we show that low-frequency stimulation (LFS) significantly augments the fornix-driven theta ratio (theta over delta power, T-ratio), in parallel with depressing thalamic synaptic responses. However, the mammillothalamic synaptic response after LFS did not correlate with the slow band of theta oscillation (low T-ratio), but did correlate positively with the fast band of theta oscillation (high T-ratio). Our data demonstrate that the descending direct fornix projection is a pathway that modulates theta rhythm in the hippocampodiencephalic circuit, resulting in dynamic augmentation of thalamic neuronal responsiveness. These findings suggest that hippocampal theta differentially affects synaptic integration in the different structures with which the hippocampus is reciprocally connected. Keywordsanterior thalamic nuclei; fornix; mammillothalamic tract; synaptic plasticity; theta oscillation; LTP The functioning of the thalamus and the hippocampus cannot be fully elucidated without considering them as a unified network (Steriade, 2001;Warburton et al., 2001). In this context, hippocampal oscillations would be expected to have an impact on the neuronal activity of the anterior thalamic nuclei (ATN) but how the signals are actually processed through the hippocampo-diencephalic loop remains poorly understood. Large neuronal populations in ATN oscillate with frequency of 6-11 Hz, in the range of theta rhythm (Vertes et al., 2001;Tsanov et al., 2011a). Theta oscillations are a characteristic feature also of the main regions providing anterior thalamic inputs: the hippocampal formation and the medial mammillary bodies, that is the "medial" hippocampo-diencephalic system Theta rhythm has been especially related to the processes of episodic memory formation in the extended hippocampal system (Buzsáki, 2005). The hippocampus receives two main types of input: the first one is the theta input from the medial septum, which reverberates through hippocampo-diencephalic loop (Fig. 1A). The second hippocampal input is a highly-processed sensory information originating from multiple neocortical regions. The temporal convergence of activity from neocortical and diencephalic inputs would result in long-term storage of the encoded information. Because theta activity induces a fluctuation in cellular excitability, the probability tha...

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Section: Discussionmentioning

confidence: 87%

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confidence: 99%

Hippocampal inputs mediate theta-related plasticity in anterior thalamus

et al. 2011

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“…Episodes of high amplitude and regular theta rhythm typically appear during movement-related behavior like running or exploration (Pickenhain and Klingberg, 1967;Vandenvolf, 1969;Whishaw and Vandenvolf, 1973;Arnolds et al, 1979aArnolds et al, , 1979b but not during grooming, drinking or eating (Buzsiki et al, 1983). Theta rhythm can also be evoked in immobile animals by novel, startling or relevant events (Sainsbury and Montoya, 1984;Fontani et al, 1984;Sainsbury et al, 1987). In our experiments we did not observe a clear correlation between the rat's movement and the P300.…”

Section: Difference (R-i)mentioning

confidence: 99%

Task-relevant late positive component in rats: Is it related to hippocampal theta rhythm?

Brankačk

Seidenbecher²,

Müller‐Gärtner

1996

Hippocampus

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“…In rats, the presence of theta rhythm with a characteristic frequency of 7-9 Hz is strongly correlated with what Vandenvolf et al (1975) called type I movements, which include locomotion, orienting, rearing, or exploratory sniffing; a strong theta rhythm is also invariably present during REM sleep (Winson, 1972). During light dissociative anesthesia, and occasionally during still alert states, theta oscillations with a lower frequency range and distinctive pharmacological properties can be recorded Sainsbury et al, 1987). All types of theta are eliminated from the hippocampal formation if the medial sepral area is lesioned or inactivated, but the sources and sinks of the extracellular electric currents are generated mainly in the CA1 layer, fascia dentata, and entorhinal cortex (for recent reviews see Vandenvolf and Leung, 1983;Buzsiki et al, 1983;Bland, 1986;Vandenvolf, 1988;Stewart and Fox, 1990;Bland and Colom, 1993).…”

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Theta phase precession in hippocampal neuronal populations and the compression of temporal sequences

et al. 1996

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O'Keefe and Recce [ I 9931 Hippocampus 3:317-330 described an interaction between the hippocampal theta rhythm and the spatial firing of pyramidal cells in the CAI region of the rat hippocampus: they found that a cell's spike activity advances to earlier phases of the theta cycle as the rat passes through the cell's place field. The present study makes use of large-scale parallel recordings to clarify and extend this finding in several ways: 1) Most CA1 pyramidal cells show maximal activity at the same phase of the theta cycle. Although individual units exhibit deeper modulation, the depth of modulation of CAI population activity i s about 50%. The peak firing of inhibitory interneurons in CAI occurs about 60" in advance of the peak firing of pyramidal cells, but different interneurons vary widely in their peak phases. 2) The first spikes, as the rat enters a pyramidal cell's place field, come 90"-120" after the phase of maximal pyramidal cell population activity, near the phase where inhibition is least. 3) The phase advance is typically an accelerating, rather than linear, function of position within the place field. 4) These phenomena occur both on linear tracks and in two-dimensional environments where locomotion is not constrained to specific paths. 5) In two-dimensional environments, place-related firing is more spatially specific during the early part of the theta cycle than during the late part. This is also true, to a lesser extent, on a linear track. Thus, spatial selectivity waxes and wanes over the theta cycle. 6 ) Granule cells of the fascia dentata are also modulated by theta. The depth of modulation for the granule cell population approaches 1 OO%, and the peak activity of the granule cell population comes about 90" earlier in the theta cycle than the peak firing of CAI pyramidal cells. 7) Granule cells, like pyramidal cells, show robust phase precession. 8) Cross-correlation analysis shows that portions of the temporal sequence of CA1 pyramidal cell place fields are replicated repeatedly within individual theta cycles, in highly compressed form. The compression ratio can be as much as 1O:l.These findings indicate that phase precession is a very robust effect, distributed across the entire hippocampal population, and that it is likely to be inherited from the fascia dentata or an earlier stage in the hippocampal circuit, rather than generated intrinsically within CA1. It i s hypothesized that the compression of temporal sequences of place fields within individual theta cycles permits the use of long-term potentiation for learning of sequential structure, thereby giving a temporal dimension to hippocampal memory traces.

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Sensitization and hippocampal type 2 theta in the rat

Cited by 40 publications

References 13 publications

Hippocampal inputs mediate theta-related plasticity in anterior thalamus

Hippocampal inputs mediate theta-related plasticity in anterior thalamus

Task-relevant late positive component in rats: Is it related to hippocampal theta rhythm?

Theta phase precession in hippocampal neuronal populations and the compression of temporal sequences

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