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Results for “Theta Rhythm”

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At least 19 recordsLinked to original sources

PubMed1976

Hippocampal theta rhythm. II. Depth profiles in the freely moving rabbit.

Depth profiles of hippocampal theta rhythm were investigated in the freely moving rabbit during three behavioral conditions: REM sleep, voluntary movement, and during sensory stimulation applied to the motionless animal. Profiles were found to be the same in all three conditions. Dorsoventral microelectrode penetration of the dorsal hippocampus revealed an approximately uniform amplitude of theta rhythm in strata oriens and pyramidal of CA1. Further microelectrode advancement revealed a sharp reversal of phase and a coincident null in amplitude in the proximal stratum radiatum. There was also a peak of theta rhythm amplitude which occurred in the molecular layer of the dorsal blade of the dentate gyrus. These data imply that in the rabbit, as in the freely moving rat, there are two generators of theta rhythm in the dorsal hippocampus, one in the dentate gyrus and the other in the overlying CA1 layer. The data also indicate the existence of a species difference in generating systems between the rabbit and the rat.

Animals↗

PubMed1978

Loss of hippocampal theta rhythm results in spatial memory deficit in the rat.

Rats learned, using distal room cues, to run to a goal on an elevated, circular track starting from any position on the track. The goal was one of eight equidistant, recessed cups set around the track, the goal cup being distinguished from the others solely by its position in the room. After learning, electrolytic lesions were made in the medial septal nucleus eliminating hippocampal theta rhythm in some animals but not in others. Rats without theta rhythm were no longer able to perform the spatial task, whereas rats with undisturbed theta rhythm retrained normal performance. Although rats without theta rhythm could not find their way directly to the goal, they recognized its location when they came upon it by chance. This type of spatial deficit appears similar to that shown by hippocampally lesioned patient H.M. Subsequent tests demonstrated that rats deprived of theta rhythm before training could nevertheless learn the task.

Animals↗

PubMed1977

[Ontogenetic analysis of the theta rhythm during paradoxical sleep in rats].

In the rat, an ontogenetic study of theta rhythm during paradoxical sleep shows a clear evolution between the 14th and the 30th postnatal day. During this period, its mean frequency increases from 5 to 7 cycles per second, and its spectrum shows significant changes. These parameters (mean frequency and spectral components) of the theta rhythm could be a useful index of brain maturation in the rat.

Animals↗

PubMed1978

[Effects of bilateral dorsolateral pontine tegmentum lesions on hippocampus theta rhythm during paradoxical sleep in the rat].

Electrolytic lesions of the dorsolateral pontine tegmentum aimed at the locus coeruleus (LC) were performed bilaterally in 13 chronically implanted Rats. Following lesions, transient alterations of characteristic components of theta rhythm appeared. No shortening of duration of paradoxical sleep (PS) was observed. These results do not support the hypothesis that neurons of LC are directly involved in the production of theta rhythm during PS; moreover they seem not to be necessary to the normal appearance of this state of sleep.

Animals↗

PubMedDate not supplied

[Posterior theta rhythms during waking state activity in man (author's transl)].

Telemetric recordings were made of 44 subjects divided into 4 groups according to age and occupation (35 and 50 years--skilled workers and university personel), during a period of 8 hours working activity. Short sequences of posterior theta rhythms were observed in all cases. They appear mainly during continuous work activity and diminish or disappear when work ceases. They are more frequent in the 50-year-old subjects than in those aged 35 years. They are neither pathological nor related to immaturity or emotion, and their etiology is related to visual perception and attention.

Adult↗

PubMed1979

Septo-hippocampal connections and the hippocampal theta rhythm.

Recordings were made of spontaneous hippocampal theta activity in free-moving rats, before and after a variety of lesions. Three recording sites were used to monitor activity in the dorsal hippocampus, the ventral hippocampus, or close to the site of the hippocampal flexure. Electrolytic lesions were made in the medial septal area or the dorso-lateral septal area; surgical transections were made of the fimbria or dorso-medial area of the fornix. Following lesions restricted to the medial septal area, theta was abolished throughout the hippocampus; after lesions restricted to the dorso-lateral septal area theta was retained. Fimbria lesions abolished it in the dorsal, but not the ventral, hippocampus. In some subjects the hippocampal formation was subsequently stained for cholinesterase: cholinesterase staining loss was generally associated with theta loss, but this was not clear at the flexure recording site. It was confirmed that theta is dependent upon the integrity of the medial septal area. It was concluded that damage to hippocampal afferents from the septum does abolish theta, while damaging the feedback efferents does not.

Animals↗

PubMed1979

Dipole-like neuronal sources of theta rhythm in dorsal hippocampus, dentate gyrus and cingulate cortex of the urethane-anesthetized rat.

Spatial distribution of theta activity was investigated in the dorsal hippocampal formation and overlying neocortex of the urethane-anesthetized rat. Laminar phase profiles from semi-microelectrode penetartions showed approximately 180 degrees phase shifts combined with small amplitude values in stratum radiatum of CA1, instratum moleculare of the dentate gyrus and in layer V/VI of the cingulate cortex at theta peak frequency. Evidence has been presented that layers of neurons in CA1, in the dorsal granular layer and in the cingulate cortex are the sources of dipole-like theta field potentials. A strong linear relationship between the neuronal theta sources in hippocampal CA1, dentate area and cingulate cortex was found.

Animals↗

PubMedDate not supplied