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E. Jurkowlaniec - One of the best experts on this subject based on the ideXlab platform.

  • The effect of pharmacological inactivation of the mammillary body and anterior thalamic nuclei on Hippocampal Theta Rhythm in urethane-anesthetized rats.
    Neuroscience, 2017
    Co-Authors: Witold Żakowski, Piotr Zawistowski, Łukasz Braszka, E. Jurkowlaniec
    Abstract:

    The mammillary body (MB) and the anterior thalamic nuclei (ATN) are closely related structures, which take part in learning and memory processes. However, the exact role of these structures has remained unclear. In both structures neurons firing according to Hippocampal Theta Rhythm have been found, mainly in the medial mammillary nucleus (MM) and anteroventral thalamic nucleus (AV). These neurons are driven by descending projections from the Hippocampal formation and are thought to convey Theta Rhythm back to the hippocampus (HP). We argue that the MB-ATN axis not only relays Theta signal, but may also modulate it. To examine it, we performed a pharmacological inactivation of the MM and AV by local infusion of procaine, and measured changes in Theta activity in selected structures of the extended Hippocampal system in urethane-anesthetized rats. The inactivation of the MM resulted in decrease in EEG power in the HP and AV, the most evidently in the lower Theta frequency bands, i.e. 3-5Hz in the HP (down to 9.2% in 3- to 4-Hz band and 37.6% in 4- to 5-Hz band, in comparison to the power in the control conditions) and 3-4Hz in the AV (down to 24.9%). After the AV inactivation, Hippocampal EEG power decreased in Theta frequency bands of 3-8Hz (down to 61.6% in 6- to 7-Hz band and 69.4% in 7- to 8-Hz band). Our results suggest that the role of the MB-ATN axis in regulating Theta Rhythm signaling may be much more important than has been speculated so far.

  • Hippocampal Theta Rhythm after local administration of procaine or amphetamine into the ventral tegmental area in fear conditioned rats
    Neuroscience letters, 2015
    Co-Authors: Paweł Matulewicz, Jolanta Orzeł-gryglewska, Łukasz Braszka, Piotr Zawistowski, E. Jurkowlaniec
    Abstract:

    The ventral tegmental area (VTA) is thought to be an important component in the mesocorticolimbic system involved in the regulation of Theta Rhythm in the hippocampus. In this study we investigate the effect of pharmacological inactivation (local procaine infusion) or activation (local amphetamine infusion) of the VTA on Theta Rhythm parameters during task specific behavior in fear conditioned, freely moving rats. Animals were implanted with bilateral recording electrodes into the dorsal hippocampus (CA1) and bilateral injection cannulas into the VTA. Behavioral activities and Hippocampal local field potentials (LFP) were recorded throughout the experiment, in pre- and post-injection conditions. We found that intra-VTA injection of procaine temporarily suppressed fear conditioned avoidance response (escape from the foot-shock arena) and also influenced Hippocampal Theta Rhythm parameters during immobility linked with arousal and/or attention. Procaine infusion decreased the signal power (Pmax) of Theta Rhythm during immobility behavior, in comparison to the control group (water infusion), whereas administration of amphetamine had no effect on the behavior and Hippocampal LFP. Our results indicate that temporal inactivation of neuronal activity in the VTA affects Hippocampal Theta Rhythm linked with attentional immobility and suppresses avoidance response in fear conditioned animals.

  • NMDA-glutamatergic activation of the ventral tegmental area induces Hippocampal Theta Rhythm in anesthetized rats
    Brain research bulletin, 2014
    Co-Authors: Paweł Matulewicz, Jolanta Orzeł-gryglewska, Magda Kuśmierczak, E. Jurkowlaniec
    Abstract:

    Abstract Glutamate afferents reaching the ventral tegmental area (VTA) affect dopamine (DA) cells in this structure probably mainly via NMDA receptors. VTA appears to be one of the structures involved in regulation of Hippocampal Theta Rhythm, and this work aimed at assessing the role of glutamatergic activation of the VTA in the Theta regulation. Male Wistar rats ( n  = 17) were divided into groups, each receiving intra-VTA microinjection (0.5 μl) of either solvent (water), glutamatergic NMDA agonist (0.2 μg) or antagonist (MK-801, 3.0 μg). Changes in local field potential were assessed on the basis of peak power ( P max ) and corresponding peak frequency ( F max ) for the delta (0.5–3 Hz) and Theta (3–6 Hz) bands. NMDA microinjection evoked long-lasting Hippocampal Theta. The Rhythm appeared with a latency of ca. 12 min post-injection and lasted for over 30 min; P max in this band was significantly increased for 50 min, while simultaneously P max in the delta band remained lower than in control conditions. Theta F max and delta F max were increased in almost entire post-injection period (by 0.3–0.5 Hz and 0.3–0.7 Hz, respectively). MK-801 depressed the sensory-evoked Theta: tail pinch could not induce Theta for 30 min after the injection; P max significantly decreased in the Theta band and at the same time it increased in the delta band. Theta F max decreased 10 and 20 min post injection (by 0.4–0.5 Hz) and delta F max decreased in almost entire post injection period (by 0.3–0.7 Hz). NMDA injection generates Theta Rhythm probably through stimulation of dopaminergic activity within the VTA.

  • Induction of Hippocampal Theta Rhythm by electrical stimulation of the ventral tegmental area and its loss after septum inactivation
    Brain research, 2011
    Co-Authors: Jolanta Orzeł-gryglewska, Magda Kuśmierczak, I. Majkutewicz, E. Jurkowlaniec
    Abstract:

    Abstract The ventral tegmental area (VTA), which may be one of the structures involved in regulation of Hippocampal Theta Rhythm, sends direct projections to the hippocampus and also to the forebrain septum, the key centres involved in Theta generation. In the present study we aimed at assessing which projections from the VTA (direct or through the septum) participate in regulation of Hippocampal electric activity. Experiments were conducted on 3 groups of urethanised male Wistar rats. In the first group (n = 6) electrical stimulation of the VTA was used to evoke Theta Rhythm episodes in hippocampus. Stimulation was repeatedly applied in control conditions and after procainic blockade of the septum. The second group (n = 6), subjected to unilateral electrical stimulation of the VTA (30-s stimulation at 10-min intervals during 2 h) and to subsequent detection of Fos expression, served to measure neuronal activation of the target mesolimbic structures. Activation levels of selected structures were compared to data from analogous stimulation of the zona incerta (ZI, the third group, n = 6). Stimulation of the VTA immediately generated regular Theta Rhythm in both hippocampi. Inactivation of the septum with procaine temporarily abolished this effect. VTA stimulation increased the density of Fos in the ipsilateral nucleus accumbens. Stimulation of the ZI never generated Theta but evoked significant induction of Fos expression in the hippocampus. Our data suggest that the projection through which the VTA enhances Theta Rhythm is not direct but is incorporated into the main route of Theta generation, which involves septum as the main relay node.

  • Involvement of GABAergic transmission in the midbrain ventral tegmental area in the regulation of Hippocampal Theta Rhythm.
    Brain research bulletin, 2010
    Co-Authors: Jolanta Orzeł-gryglewska, Magda Kuśmierczak, E. Jurkowlaniec
    Abstract:

    Abstract Previously we indicated that the ventral tegmental area (VTA) may belong to the system regulating Hippocampal Theta Rhythm. In the present study, we aimed at assessing the role of the GABAergic system of the VTA in regulation of Hippocampal electric activity. Male Wistar rats received unilateral intra-VTA microinjection of either bicuculline (50 ng/0.5 μl, n  = 9), muscimol (100 ng/0.5 μl, n  = 10) or phaclofen (500 ng/0.5 μl, n  = 9). 1-min tail pinch stimulations were applied at 10-min intervals to evoke Theta Rhythm episodes in hippocampus. We analysed peak power ( P max ) and corresponding frequency ( F max ) of EEG signal at delta and Theta bands. Bicuculline induced Theta Rhythm in both hippocampi with 0 latency, continuous for ca. 33 min. Phaclofen also induced Theta but in this group it appeared with latency (17.45 ± 3.16 min on average), lasted for ca. 33.6 min and during this time was interrupted by periods of irregular activity of variable length. Tail pinch was not applied in these groups. Muscimol induced an opposite effect: depression of Theta P max with simultaneous increase in delta P max and a decrease in F max delta during episodes of tail pinch-evoked Theta. This effect had variable latency and no return to the control EEG could be observed. We propose that GABA activity in the VTA is of tonic character, so that abolition of this mechanism produces immediate effect, i.e. Theta induction (strong by GABA A and weak by GABA B receptors blockade), whereas enhancing the already present GABAergic inhibition causes delayed, prolonged changes expressed as gradual loss of Theta synchronisation.

Marisa Pedemonte - One of the best experts on this subject based on the ideXlab platform.

  • Temporal correlation between auditory neurons and the Hippocampal Theta Rhythm induced by novel stimulations in awake guinea pigs.
    Brain research, 2009
    Co-Authors: Tamara Liberman, Ricardo A Velluti, Marisa Pedemonte
    Abstract:

    Abstract The Hippocampal Theta Rhythm is associated with the processing of sensory systems such as touch, smell, vision and hearing, as well as with motor activity, the modulation of autonomic processes such as cardiac Rhythm, and learning and memory processes. The discovery of temporal correlation (phase locking) between the Theta Rhythm and both visual and auditory neuronal activity has led us to postulate the participation of such Rhythm in the temporal processing of sensory information. In addition, changes in attention can modify both the Theta Rhythm and the auditory and visual sensory activity. The present report tested the hypothesis that the temporal correlation between auditory neuronal discharges in the inferior colliculus central nucleus (ICc) and the Hippocampal Theta Rhythm could be enhanced by changes in sensory stimulation. We presented chronically implanted guinea pigs with auditory stimuli that varied over time, and recorded the auditory response during wakefulness. It was observed that the stimulation shifts were capable of producing the temporal phase correlations between the Theta Rhythm and the ICc unit firing, and they differed depending on the stimulus change performed. Such correlations disappeared approximately 6 s after the change presentation. Furthermore, the power of the Hippocampal Theta Rhythm increased in half of the cases presented with a stimulation change. Based on these data, we propose that the degree of correlation between the unitary activity and the Hippocampal Theta Rhythm varies with – and therefore may signal – stimulus novelty.

  • Sleep Hippocampal Theta Rhythm and Sensory Processing
    Sleep and Sleep Disorders, 2006
    Co-Authors: Marisa Pedemonte, Ricardo A Velluti
    Abstract:

    Introduction Ancient human cultures have developed diverse forms of a device that, based on sensory stimulation, is used to put babies to sleep: the rocking cradle. Vestibular and somatosensory stimulation produced by the rocking movements, complemented by eye closure and other stimulation such as constant temperature and the mothers voice/song (lullaby) activating the auditory system, are able to induce sleep. On the other hand, it is a common experience that reducing the sensory afferent volleys to the brain can facilitate sleep. A series of experimental data will be presented demonstrating the sensory input relevance in the organization of the sleep and wakefulness cycle. Firing rate shifts in auditory and visual neurones, changes in the pattern of discharge, and, most important, the temporal correlation of the spike timing with the Hippocampal Theta Rhythm, will be set forth. Sleep, a huge change in the brain physiology, depends on both, a series of active processes and passive mechanisms, e.g., functional sensory deafferentation^'^^ and neural networks changing organization. Although many signs of active processes have been shown, there are not enough experimental data to support a final decision about the relative contribution of passive processes. ' However, both approaches may be partially reconciled conceding that the deafferentation may be provoked by an inhibitory influence acting, e.g., upon the ascending activating reticular system. Our main purpose is to provide an experimental aspect of sensory data analysis, its relation to sleep and the Hippocampal Theta Rhythm as an internal zeitgeher (time giver) for auditory and visual information processing.

  • Novelty-induced correlation between visual neurons and the Hippocampal Theta Rhythm in sleep and wakefulness.
    Brain research, 2005
    Co-Authors: Marisa Pedemonte, Juan P Gambini, Ricardo A Velluti
    Abstract:

    Various Rhythms have been shown to affect sensory processing such as the waking-sleep cycle and the Hippocampal Theta waves. Changes in the firing of visual lateral geniculate nucleus neurons have been reported to be dependent on the animal's behavioral state. The lateral geniculate extracellular neuronal firing and Hippocampal field activity were recorded in chronically implanted animals to analyze the relationship during quiet wakefulness and sleep associated with stimulation shifts that may introduce novelty. During wakefulness, a change in light flash stimulation pattern (stimuli frequency shift, stimuli on and off) caused an increment in the Theta band power in 100% of the cases and a phase-locking of the spikes in 53% of the recorded neurons. During slow wave sleep, there were no consistent changes in the Theta power notwithstanding 13% of the neurons exhibited phase-locking, i.e., novelty may induce changes in the temporal correlation of visual neuronal activity with the Hippocampal Theta Rhythm in sleep. The present results suggest that visual processing in slow wave sleep exists, while auditory information and learning were reported during slow wave sleep in animals and newborn humans. The changes in the Theta power as well as in the neuronal phase-locking amount indicate that in slow wave sleep, the ability of the hippocampus to detect/process novelty, although present, may be decreased. This is consistent with the noticeable decrease in awareness of the environment during sleep.

  • Hippocampal Theta Rhythm synchronizes visual neurons in sleep and waking.
    Brain research, 2002
    Co-Authors: Juan P Gambini, Ricardo A Velluti, Marisa Pedemonte
    Abstract:

    The Hippocampal Theta Rhythm (Theta) was reported to be associated with movements, attention, auditory processing, autonomic functions, learning and memory and postulated as an associator of discontiguous events. Since visual information includes temporal cues, our study was centered on the correlation between Hippocampal Theta Rhythm and lateral geniculate activity. Phase relationships between Hippocampal Theta and unit firing were found with both spontaneous and light evoked activity during wakefulness, slow wave and paradoxical sleep. This temporal correlation was dynamic, exhibiting changes related to the sleep-waking cycle and perhaps to attention shifts. Hippocampal Theta Rhythm may supply a low frequency temporal dimension to the processing of visual information.

  • Research report Hippocampal Theta Rhythm synchronizes visual neurons in sleep and waking
    2002
    Co-Authors: Juan P Gambini, Ricardo A Velluti, Marisa Pedemonte
    Abstract:

    The Hippocampal Theta Rhythm (u) was reported to be associated with movements, attention, auditory processing, autonomic functions, learning and memory and postulated as an associator of discontiguous events. Since visual information includes temporal cues, our study was centered on the correlation between Hippocampal u Rhythm and lateral geniculate activity. Phase relationships between Hippocampal u and unit firing were found with both spontaneous and light evoked activity during wakefulness, slow wave and paradoxical sleep. This temporal correlation was dynamic, exhibiting changes related to the sleep-waking cycle and perhaps to attention shifts. Hippocampal u Rhythm may supply a low frequency temporal dimension to the processing of visual information. © 2002 Elsevier Science B.V. All rights reserved. Theme: Neural basis of behavior Topic: Biological Rhythms and sleep

Chiaki Kamei - One of the best experts on this subject based on the ideXlab platform.

  • Effects of histamine H1 receptor antagonists on Hippocampal Theta Rhythm during spatial memory performance in rats
    European Journal of Pharmacology, 2007
    Co-Authors: Takayoshi Masuoka, Azusa Mikami, Masa Yasuda, Kazuaki Shinomiya, Chiaki Kamei
    Abstract:

    Abstract The effects of histamine H 1 receptor antagonists (promethazine, diphenhydramine, chlorphenilamine and triprolidine) on Hippocampal Theta Rhythm during eight-arm radial maze performance were investigated using rats. Promethazine showed a significant increase in the number of total errors and working memory errors at doses of 10 and 20 mg/kg, and a significant increase was also observed in reference memory errors at a dose of 20 mg/kg. Diphenhydramine and chlorphenilamine at a dose of 20 mg/kg and triprolidine at a dose of 35 mg/kg also caused significant increases in the number of total, reference memory and working memory errors. Promethazine, diphenhydramine and chlorphenilamine, having potent anti-muscarinic receptor properties, increased Hippocampal Theta power during radial maze performance at a dose of 20 mg/kg. On the other hand, triprolidine, which has weak anti-muscarinic receptor properties compared with other histamine H 1 receptor antagonists, decreased Theta power at a dose of 35 mg/kg. These results suggest that anti-muscarinic receptor properties rather than anti-histamine H 1 receptor properties may affect Hippocampal Theta power during spatial memory deficit induced by promethazine, diphenhydramine and chlorphenilamine.

  • Effects of histamine H(1) receptor antagonists on Hippocampal Theta Rhythm during spatial memory performance in rats.
    European journal of pharmacology, 2007
    Co-Authors: Takayoshi Masuoka, Azusa Mikami, Masa Yasuda, Kazuaki Shinomiya, Chiaki Kamei
    Abstract:

    The effects of histamine H(1) receptor antagonists (promethazine, diphenhydramine, chlorphenilamine and triprolidine) on Hippocampal Theta Rhythm during eight-arm radial maze performance were investigated using rats. Promethazine showed a significant increase in the number of total errors and working memory errors at doses of 10 and 20 mg/kg, and a significant increase was also observed in reference memory errors at a dose of 20 mg/kg. Diphenhydramine and chlorphenilamine at a dose of 20 mg/kg and triprolidine at a dose of 35 mg/kg also caused significant increases in the number of total, reference memory and working memory errors. Promethazine, diphenhydramine and chlorphenilamine, having potent anti-muscarinic receptor properties, increased Hippocampal Theta power during radial maze performance at a dose of 20 mg/kg. On the other hand, triprolidine, which has weak anti-muscarinic receptor properties compared with other histamine H(1) receptor antagonists, decreased Theta power at a dose of 35 mg/kg. These results suggest that anti-muscarinic receptor properties rather than anti-histamine H(1) receptor properties may affect Hippocampal Theta power during spatial memory deficit induced by promethazine, diphenhydramine and chlorphenilamine.

  • Participation of the Hippocampal Theta Rhythm in memory formation for an eight-arm radial maze task in rats
    Brain research, 2006
    Co-Authors: Takayoshi Masuoka, Yoko Fujii, Chiaki Kamei
    Abstract:

    Participation of the Hippocampal Theta Rhythm in memory formation was studied using an eight-arm radial maze task in rats. The numbers of reference memory and working memory errors were decreased gradually by daily training from session 10 and 6, respectively. On the other hand, the decrease in running time per choice was recognized from session 3. Theta power in the Hippocampal CA1 area was gradually decreased from session 9, and there is a close relationship between the changes in Theta power in the hippocampus and the number of reference memory errors. Based on those observations, it can be concluded that the Hippocampal Theta wave is intimately associated with the reference memory of the eight-arm radial maze in rats.

  • effect of scopolamine on the Hippocampal Theta Rhythm during an eight arm radial maze task in rats
    European Journal of Pharmacology, 2006
    Co-Authors: Takayoshi Masuoka, Yoko Fujii, Chiaki Kamei
    Abstract:

    Abstract The changes in the Hippocampal Theta Rhythm during an impairment of reference and working memory of radial maze task induced by scopolamine administration were studied. Intraperitoneal injection of scopolamine at doses of 0.5 and 1.0 mg/kg caused a significant increase in the number of total, reference memory and working memory errors. On the other hand, scopolamine significantly increased the Hippocampal Theta power (5–12 Hz) at doses (0.5 and 1.0 mg/kg) that caused an impairment of reference and working memory. A significant increase in the peak frequency of the Hippocampal Theta Rhythm was also observed with scopolamine, even at a dose of 0.2 mg/kg. At doses of 0.2, 0.5 and 1.0 mg/kg, scopolamine caused a decrease in the locomotor activity during the radial maze task. From these results, it may be concluded that an increase in amplitude of the Hippocampal Theta Rhythm induced by scopolamine is closely associated with memory/learning function of the eight-arm radial maze.

Sylvain Williams - One of the best experts on this subject based on the ideXlab platform.

  • Self-generated Theta oscillations in the hippocampus
    Nature Neuroscience, 2009
    Co-Authors: Romain Goutagny, Jesse Jackson, Sylvain Williams
    Abstract:

    Hippocampal Theta Rhythm is crucial for spatial memory and is thought to be generated by extrinsic inputs. In contrast, using a complete rat hippocampus in vitro, we found several intrinsic, atropine-resistant Theta generators in CA1. These oscillators were organized along the septotemporal axis and arose independently from CA3. Our results suggest that CA1 Theta Rhythm can emerge from the coupling of multiple autonomous Hippocampal Theta oscillators.

  • In vitro activation of the medial septum—Diagonal band complex generates atropine-sensitive and atropine-resistant Hippocampal Theta Rhythm: An investigation using a complete septoHippocampal preparation
    Hippocampus, 2008
    Co-Authors: Romain Goutagny, Frédéric Manseau, Jesse Jackson, Marc Danik, Sylvain Williams
    Abstract:

    The medial septum and diagonal band complex (MS-DB) is believed to play a key role in generating Theta oscillations in the hippocampus, a phenomenon critical for learning and memory. Although the importance of the MS-DB in Hippocampal Theta Rhythm generation is generally accepted, it remains to be determined whether the MS-DB alone can generate Hippocampal oscillations or is only a transducer of Rhythmic activity from other brain areas. Secondly, it is known that Hippocampal Theta Rhythm can be separated into an atropine-sensitive and insensitive component. However, it remains to be established if the MS-DB can generate both types of Rhythm. To answer these questions, we used a new in vitro rat septoHippocampal preparation placed in a hermetically separated two side recording chamber. We showed that carbachol activation of the MS-DB generated large Theta oscillations in the CA1 and CA3 regions of the hippocampus. These oscillations were blocked by applying either the GABA(A) receptor antagonist bicuculline or the AMPA/kainate antagonist DNQX to the hippocampus. Interestingly, the application of the muscarinic receptor antagonist atropine produced only a partial decrease in the amplitude, without modification of the frequency, of Theta. These results show for the first time, that upon optimal excitation, the MS-DB alone is able to generate Hippocampal oscillations in the Theta frequency band. Moreover, these MS-DB generated Theta oscillations are mediated by muscarinic and nonmuscarinic receptors and have a pharmacological profile similar to Theta Rhythm observed in awake animals.

  • In vitro activation of the medial septum-diagonal band complex generates atropine-sensitive and atropine-resistant Hippocampal Theta Rhythm: an investigation using a complete septoHippocampal preparation.
    Hippocampus, 2008
    Co-Authors: Romain Goutagny, Frédéric Manseau, Jesse Jackson, Marc Danik, Sylvain Williams
    Abstract:

    The medial septum and diagonal band complex (MS-DB) is believed to play a key role in generating Theta oscillations in the hippocampus, a phenomenon critical for learning and memory. Although the importance of the MS-DB in Hippocampal Theta Rhythm generation is generally accepted, it remains to be determined whether the MS-DB alone can generate Hippocampal oscillations or is only a transducer of Rhythmic activity from other brain areas. Secondly, it is known that Hippocampal Theta Rhythm can be separated into an atropine-sensitive and insensitive component. However, it remains to be established if the MS-DB can generate both types of Rhythm. To answer these questions, we used a new in vitro rat septoHippocampal preparation placed in a hermetically separated two side recording chamber. We showed that carbachol activation of the MS-DB generated large Theta oscillations in the CA1 and CA3 regions of the hippocampus. These oscillations were blocked by applying either the GABA(A) receptor antagonist bicuculline or the AMPA/kainate antagonist DNQX to the hippocampus. Interestingly, the application of the muscarinic receptor antagonist atropine produced only a partial decrease in the amplitude, without modification of the frequency, of Theta. These results show for the first time, that upon optimal excitation, the MS-DB alone is able to generate Hippocampal oscillations in the Theta frequency band. Moreover, these MS-DB generated Theta oscillations are mediated by muscarinic and nonmuscarinic receptors and have a pharmacological profile similar to Theta Rhythm observed in awake animals.

Ricardo A Velluti - One of the best experts on this subject based on the ideXlab platform.

  • Temporal correlation between auditory neurons and the Hippocampal Theta Rhythm induced by novel stimulations in awake guinea pigs.
    Brain research, 2009
    Co-Authors: Tamara Liberman, Ricardo A Velluti, Marisa Pedemonte
    Abstract:

    Abstract The Hippocampal Theta Rhythm is associated with the processing of sensory systems such as touch, smell, vision and hearing, as well as with motor activity, the modulation of autonomic processes such as cardiac Rhythm, and learning and memory processes. The discovery of temporal correlation (phase locking) between the Theta Rhythm and both visual and auditory neuronal activity has led us to postulate the participation of such Rhythm in the temporal processing of sensory information. In addition, changes in attention can modify both the Theta Rhythm and the auditory and visual sensory activity. The present report tested the hypothesis that the temporal correlation between auditory neuronal discharges in the inferior colliculus central nucleus (ICc) and the Hippocampal Theta Rhythm could be enhanced by changes in sensory stimulation. We presented chronically implanted guinea pigs with auditory stimuli that varied over time, and recorded the auditory response during wakefulness. It was observed that the stimulation shifts were capable of producing the temporal phase correlations between the Theta Rhythm and the ICc unit firing, and they differed depending on the stimulus change performed. Such correlations disappeared approximately 6 s after the change presentation. Furthermore, the power of the Hippocampal Theta Rhythm increased in half of the cases presented with a stimulation change. Based on these data, we propose that the degree of correlation between the unitary activity and the Hippocampal Theta Rhythm varies with – and therefore may signal – stimulus novelty.

  • Sleep Hippocampal Theta Rhythm and Sensory Processing
    Sleep and Sleep Disorders, 2006
    Co-Authors: Marisa Pedemonte, Ricardo A Velluti
    Abstract:

    Introduction Ancient human cultures have developed diverse forms of a device that, based on sensory stimulation, is used to put babies to sleep: the rocking cradle. Vestibular and somatosensory stimulation produced by the rocking movements, complemented by eye closure and other stimulation such as constant temperature and the mothers voice/song (lullaby) activating the auditory system, are able to induce sleep. On the other hand, it is a common experience that reducing the sensory afferent volleys to the brain can facilitate sleep. A series of experimental data will be presented demonstrating the sensory input relevance in the organization of the sleep and wakefulness cycle. Firing rate shifts in auditory and visual neurones, changes in the pattern of discharge, and, most important, the temporal correlation of the spike timing with the Hippocampal Theta Rhythm, will be set forth. Sleep, a huge change in the brain physiology, depends on both, a series of active processes and passive mechanisms, e.g., functional sensory deafferentation^'^^ and neural networks changing organization. Although many signs of active processes have been shown, there are not enough experimental data to support a final decision about the relative contribution of passive processes. ' However, both approaches may be partially reconciled conceding that the deafferentation may be provoked by an inhibitory influence acting, e.g., upon the ascending activating reticular system. Our main purpose is to provide an experimental aspect of sensory data analysis, its relation to sleep and the Hippocampal Theta Rhythm as an internal zeitgeher (time giver) for auditory and visual information processing.

  • Novelty-induced correlation between visual neurons and the Hippocampal Theta Rhythm in sleep and wakefulness.
    Brain research, 2005
    Co-Authors: Marisa Pedemonte, Juan P Gambini, Ricardo A Velluti
    Abstract:

    Various Rhythms have been shown to affect sensory processing such as the waking-sleep cycle and the Hippocampal Theta waves. Changes in the firing of visual lateral geniculate nucleus neurons have been reported to be dependent on the animal's behavioral state. The lateral geniculate extracellular neuronal firing and Hippocampal field activity were recorded in chronically implanted animals to analyze the relationship during quiet wakefulness and sleep associated with stimulation shifts that may introduce novelty. During wakefulness, a change in light flash stimulation pattern (stimuli frequency shift, stimuli on and off) caused an increment in the Theta band power in 100% of the cases and a phase-locking of the spikes in 53% of the recorded neurons. During slow wave sleep, there were no consistent changes in the Theta power notwithstanding 13% of the neurons exhibited phase-locking, i.e., novelty may induce changes in the temporal correlation of visual neuronal activity with the Hippocampal Theta Rhythm in sleep. The present results suggest that visual processing in slow wave sleep exists, while auditory information and learning were reported during slow wave sleep in animals and newborn humans. The changes in the Theta power as well as in the neuronal phase-locking amount indicate that in slow wave sleep, the ability of the hippocampus to detect/process novelty, although present, may be decreased. This is consistent with the noticeable decrease in awareness of the environment during sleep.

  • Hippocampal Theta Rhythm synchronizes visual neurons in sleep and waking.
    Brain research, 2002
    Co-Authors: Juan P Gambini, Ricardo A Velluti, Marisa Pedemonte
    Abstract:

    The Hippocampal Theta Rhythm (Theta) was reported to be associated with movements, attention, auditory processing, autonomic functions, learning and memory and postulated as an associator of discontiguous events. Since visual information includes temporal cues, our study was centered on the correlation between Hippocampal Theta Rhythm and lateral geniculate activity. Phase relationships between Hippocampal Theta and unit firing were found with both spontaneous and light evoked activity during wakefulness, slow wave and paradoxical sleep. This temporal correlation was dynamic, exhibiting changes related to the sleep-waking cycle and perhaps to attention shifts. Hippocampal Theta Rhythm may supply a low frequency temporal dimension to the processing of visual information.

  • Research report Hippocampal Theta Rhythm synchronizes visual neurons in sleep and waking
    2002
    Co-Authors: Juan P Gambini, Ricardo A Velluti, Marisa Pedemonte
    Abstract:

    The Hippocampal Theta Rhythm (u) was reported to be associated with movements, attention, auditory processing, autonomic functions, learning and memory and postulated as an associator of discontiguous events. Since visual information includes temporal cues, our study was centered on the correlation between Hippocampal u Rhythm and lateral geniculate activity. Phase relationships between Hippocampal u and unit firing were found with both spontaneous and light evoked activity during wakefulness, slow wave and paradoxical sleep. This temporal correlation was dynamic, exhibiting changes related to the sleep-waking cycle and perhaps to attention shifts. Hippocampal u Rhythm may supply a low frequency temporal dimension to the processing of visual information. © 2002 Elsevier Science B.V. All rights reserved. Theme: Neural basis of behavior Topic: Biological Rhythms and sleep