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Amplitude and phase laminar profiles of theta in the hippocampal formation in vitro

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Kowalczyk T., Konopacki J.
Postępy Higieny i Medycyny Doświadczalnej
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2002
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vol. 56
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issue 3
353-360
EN
Amplitude and phase profiles of theta rhythm induced in the hippocampal formation slices by bath perfusion of carbachol was studied. Amplitude and phase profiles obtained in vitro closely resemble profiles of spontaneous theta rhythm recorded in freely behaving or anaesthetised rats. Electrotonic mechanism underlying the in vivo and in vitro theta are discussed
2
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Electrical hippocampal activity during danger and safety signals in classical conditioning in the rat

80%
Kasicki S., Jelen P., Olszewski M., Slawinska U.
Acta Neurobiologiae Experimentalis
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2009
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vol. 69
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issue 1
119-128
EN
The effect of stimuli predicting danger (DS) and safety (SS) in Pavlovian aversive conditioning on hippocampal local field potentials (LFP) was studied in 25 partially restrained adult male rats (Long-Evans). DS lasting 5 s preceded tail-shock, while SS overlapping DS during DS last 3 s predicted omission of shock. The power spectra of LFPs during trials were analyzed in theta and delta frequency bands. In DS, theta frequency during the last 3 s was lower that in first 2 s. In danger and safety situation theta peak frequency was different for dorsal CA1 activity (5.99 Hz vs. 6.86 Hz, respectively), while delta peak frequency was different for ventral CA1 (1.56 Hz vs. 1.07 Hz) for the last 3 s of trial. Differences in theta frequency in danger and safety situation may reflect differences in sensory processing during induced emotional states and/or related differences in motor behavior.
3
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In vitro recorded theta-like activity in the limbic cortex: comparison with spontaneous theta and epileptiform discharges

80%
Konopacki J., Golebiewski H., Eckersdorf B., Kowalczyk T., Bocian R.
Acta Neurobiologiae Experimentalis
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2000
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vol. 60
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issue 1
67-85
EN
The generation of EEG theta rhythm in the mammalian limbic cortex is a prime example of rhythmic activity that involves central mechanisms of oscillations and synchrony. This EEG pattern has been extensively studied since 1938, when Jung and Kornmller (1938) demonstrated the first theta recordings in the hippocampal formation of rabbits. In 1986 in collaboration with Drs. B.H. Bland, S.H. Roth and B.M. MacIver we demonstrated for the first time that bath perfusion of hippocampal slices with the cholinergic agonist, carbachol, resulted in theta-like oscillations. Since this initial demonstration of in vitro theta-like activity, we have carried out a number of experiments in an attempt to answer the basic question: what are the similarities between cholinergic-induced in vitro theta-like activity and theta rhythm which naturally occurs in the in vivo preparation. Thus far, our studies have provided strong evidence that theta-like activity recorded in vitro shares many of the physiological and pharmacological properties of theta rhythm observed in vivo. The question whether in vitro theta-like oscillations reflect features of epileptiform activity is also adressed in this review.
4
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Effect of posterior hypothalamic injection of procaine on the hippocampal theta rhythm in freely moving cats

70%
Bocian R., Konopacki J.
Acta Neurobiologiae Experimentalis
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2001
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vol. 61
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issue 2
125-134
EN
Earlier in vivo studies conducted on freely moving and anesthetized rats demonstrated that the posterior hypothalamus (PH) comprises pathways critical for producing the synchronous hippocampal formation (HPC) theta rhythm. In addition, these findings suggested that the frequency of the HPC theta was encoded in the PH and then was fed via the medial forebrain bundle to the medial septum and HPC. In the present study we attempted to verify this hypothesis with use of a different in vivo model - freely moving cats. The microinjection of the local anaesthetic, procaine, into the PH region reversibly suppressed the spontaneous as well as sensory and electrically induced HPC theta. However, in contrast to rats, in freely moving cats microinjection of procaine into the PH reduced the amplitude of the HPC theta but had no effect on theta frequency. We conclude that in freely moving cats the PH region comprises a critical part of the ascending brainstem pathway, for production of the HPC theta rhythm. In contrast to rats, in freely moving cats ascending inputs from the brainstem to the PH contribute mainly to the amplitude of the HPC theta rhythm.
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