scholarly journals Theta Oscillations and Reactivity of Hippocampal Stratum Oriens Neurons

2010 ◽  
Vol 10 ◽  
pp. 930-943 ◽  
Author(s):  
Valentina F. Kitchigina
Keyword(s):  
Hippocampal Neurons ◽  
Theta Rhythm ◽  
Phase Locking ◽  
Theta Oscillations ◽  
Strong Increase ◽  
Information Selection ◽  
Significant Stimulus ◽  
Stratum Oriens ◽  
Hippocampal Activity ◽  
Nonpyramidal Neurons

The supposition was advanced that the neuronal theta rhythmicity is the key mode of signal selection at the hippocampal level. To address this hypothesis, the experimental data on the responses of putative hippocampal interneurons of the stratum oriens CA1-CA3 to stimulation during enhanced theta rhythm and after its blockade are reviewed. Both a strong increase and a decrease of the natural theta rhythm disturbed the reactions of hippocampal neurons; during theta augmentation, the responses were masked or disappeared, and after theta blockade, they lost the ability to habituate. In both cases, two important events were broken: the resetting of the background activity and the phase-locking of theta cycles to stimulus. These data allow one to suppose that only important stimuli are normally capable to evoke these events and these stimuli are selected for recording. When the response to a significant stimulus occurs, the following theta prevents the responses to other stimuli. This probably protects the hippocampal activity from interference from irrelevant signals. Presumably, the absence of the theta deprives the hippocampus of this protection. During enhanced and persistent theta oscillations, the reset disappeared and theta bursts were generated without stimulus locking. In this state, the system is probably closed and the information cannot be recorded. During the theta blockade, the reset was too long and did not habituate. In this case, the system is open for any signals and the hippocampus loses the ability to select signal. This analysis suggests that information selection in the hippocampus may be performed with the participation of nonpyramidal neurons.

scholarly journals Excitatory Inputs Determine Phase-Locking Strength and Spike-Timing of CA1 Stratum Oriens/Alveus Parvalbumin and Somatostatin Interneurons during Intrinsically Generated Hippocampal Theta Rhythm

2016 ◽  
Vol 36 (25) ◽  
pp. 6605-6622 ◽  
Author(s):  
Carey Y. L. Huh ◽  
Bénédicte Amilhon ◽  
Katie A. Ferguson ◽  
Frédéric Manseau ◽  
Susana G. Torres-Platas ◽  
...  
Keyword(s):  
Theta Rhythm ◽  
Phase Locking ◽  
Spike Timing ◽  
Hippocampal Theta Rhythm ◽  
Stratum Oriens ◽  
Hippocampal Theta

scholarly journals tACS Phase Locking of Frontal Midline Theta Oscillations Disrupts Working Memory Performance

2016 ◽  
Vol 10 ◽  
Author(s):  
Bankim S. Chander ◽  
Matthias Witkowski ◽  
Christoph Braun ◽  
Stephen E. Robinson ◽  
Jan Born ◽  
...  
Keyword(s):  
Working Memory ◽  
Phase Locking ◽  
Memory Performance ◽  
Theta Oscillations ◽  
Frontal Midline Theta

scholarly journals Acid-sensing ion channels regulate spontaneous inhibitory activity in the hippocampus: possible implications for epilepsy

2016 ◽  
Vol 371 (1700) ◽  
pp. 20150431 ◽  
Author(s):  
O. Ievglevskyi ◽  
D. Isaev ◽  
O. Netsyk ◽  
A. Romanov ◽  
M. Fedoriuk ◽  
...  
Keyword(s):  
Ion Channels ◽  
Hippocampal Neurons ◽  
Hippocampal Slices ◽  
Synaptic Activity ◽  
Mammalian Brain ◽  
Strong Increase ◽  
Life And Death ◽  
Acid Sensing Ion Channels

Acid-sensing ion channels (ASICs) play an important role in numerous functions in the central and peripheral nervous systems ranging from memory and emotions to pain. The data correspond to a recent notion that each neuron and many glial cells of the mammalian brain express at least one member of the ASIC family. However, the mechanisms underlying the involvement of ASICs in neuronal activity are poorly understood. However, there are two exceptions, namely, the straightforward role of ASICs in proton-based synaptic transmission in certain brain areas and the role of the Ca 2+ -permeable ASIC1a subtype in ischaemic cell death. Using a novel orthosteric ASIC antagonist, we have found that ASICs specifically control the frequency of spontaneous inhibitory synaptic activity in the hippocampus. Inhibition of ASICs leads to a strong increase in the frequency of spontaneous inhibitory postsynaptic currents. This effect is presynaptic because it is fully reproducible in single synaptic boutons attached to isolated hippocampal neurons. In concert with this observation, inhibition of the ASIC current diminishes epileptic discharges in a low Mg 2+ model of epilepsy in hippocampal slices and significantly reduces kainate-induced discharges in the hippocampus in vivo . Our results reveal a significant novel role for ASICs. This article is part of the themed issue ‘Evolution brings Ca 2+ and ATP together to control life and death’.

Lesions of the Vestibular System Disrupt Hippocampal Theta Rhythm in the Rat

2006 ◽  
Vol 96 (1) ◽  
pp. 4-14 ◽  
Author(s):  
Noah A. Russell ◽  
Arata Horii ◽  
Paul F. Smith ◽  
Cynthia L. Darlington ◽  
David K. Bilkey
Keyword(s):  
Vestibular System ◽  
Hippocampal Neurons ◽  
Theta Rhythm ◽  
Spatial Information ◽  
Power Spectral Analysis ◽  
Spatial Location ◽  
Lesion Group ◽  
Movement Velocity ◽  
Ca1 Neurons ◽  
Ca1 Region

The hippocampus has a major role in memory for spatial location. Theta is a rhythmic hippocampal EEG oscillation that occurs at ∼8 Hz during voluntary movement and that may have some role in encoding spatial information. We investigated whether, as part of this process, theta might be influenced by self-movement signals provided by the vestibular system. The effects of bilateral peripheral vestibular lesions, made ≥60 days prior to recording, were assessed in freely moving rats. Power spectral analysis revealed that theta in the lesioned animals had a lower power and frequency compared with that recorded in the control animals. When the electroencephalography (EEG) was compared in epochs matched for speed of movement and acceleration, theta was less rhythmic in the lesioned group, indicating that the effect was not a result of between-group differences in this behavior. Blood measurements of corticosterone were also similar in the two groups indicating that the results could not be attributed to changes in stress levels. Despite the changes in theta EEG, individual neurons in the CA1 region of lesioned animals continued to fire with a periodicity of ∼8 Hz. The positive correlation between cell firing rate and movement velocity that is observed in CA1 neurons of normal animals was also maintained in cells recorded from lesion group animals. These findings indicate that although vestibular signals may contribute to theta rhythm generation, velocity-related firing in hippocampal neurons is dependent on nonvestibular signals such as sensory flow, proprioception, or motor efference copy.

scholarly journals A distinctive subpopulation of medial septal slow-firing neurons promote hippocampal activation and theta oscillations

2011 ◽  
Vol 106 (5) ◽  
pp. 2749-2763 ◽  
Author(s):  
Hao Zhang ◽  
Shih-Chieh Lin ◽  
Miguel A. L. Nicolelis
Keyword(s):  
Medial Septum ◽  
Theta Oscillations ◽  
Short Term ◽  
Neuronal Ensembles ◽  
Gamma Range ◽  
Diagonal Band ◽  
Hippocampal Activity ◽  
Diagonal Band Of Broca ◽  
Hippocampal Theta ◽  
Relationship Of

The medial septum-vertical limb of the diagonal band of Broca (MSvDB) is important for normal hippocampal functions and theta oscillations. Although many previous studies have focused on understanding how MSVDB neurons fire rhythmic bursts to pace hippocampal theta oscillations, a significant portion of MSVDB neurons are slow-firing and thus do not pace theta oscillations. The function of these MSVDB neurons, especially their role in modulating hippocampal activity, remains unknown. We recorded MSVDB neuronal ensembles in behaving rats, and identified a distinct physiologically homogeneous subpopulation of slow-firing neurons (overall firing <4 Hz) that shared three features: 1) much higher firing rate during rapid eye movement sleep than during slow-wave (SW) sleep; 2) temporary activation associated with transient arousals during SW sleep; 3) brief responses (latency 15∼30 ms) to auditory stimuli. Analysis of the fine temporal relationship of their spiking and theta oscillations showed that unlike the theta-pacing neurons, the firing of these “pro-arousal” neurons follows theta oscillations. However, their activity precedes short-term increases in hippocampal oscillation power in the theta and gamma range lasting for a few seconds. Together, these results suggest that these pro-arousal slow-firing MSvDB neurons may function collectively to promote hippocampal activation.

scholarly journals Accumulation of Calcium and Loss of Potassium in the Hippocampus following Transient Cerebral Ischemia: A Proton Microprobe Study

1988 ◽  
Vol 8 (4) ◽  
pp. 531-538 ◽  
Author(s):  
Eduardo Martins ◽  
Kenji Inamura ◽  
Klas Themner ◽  
Klas G. Malmqvist ◽  
Bo K. Siesjö
Keyword(s):  
Hippocampal Neurons ◽  
Plasma Membranes ◽  
Total Calcium ◽  
Calcium Cycling ◽  
Transient Ischemia ◽  
Neuronal Necrosis ◽  
X Ray ◽  
Proton Microprobe ◽  
Calcium Accumulation ◽  
Stratum Oriens

This study explored (a) whether postischemic accumulation of calcium in hippocampal neurons precedes or occurs pari passu with light microscopical signs of delayed neuronal necrosis, and (b) whether calcium initially accumulates in dendritic domains, presumed to have a high density of agonist-operated calcium channels. Transient ischemia of 10-min duration was induced in rats, and the animals were studied after 1, 2, 3, and 4 days of recovery. We measured total calcium and potassium contents in the stratum oriens, pyramidale, radiatum, and moleculare of the CA1 and CA3 sectors, using particle induced x-ray emission (PIXE) in the proton microprobe mode. The results showed significant accumulation of calcium and loss of potassium after 3 and 4 days of recovery in the CA1 sector, which developed neuronal necrosis, but not in the CA3 sector, which showed only occasional damage. In a few animals, calcium accumulation (and loss of potassium) was observed with no or only mild visible damage, but in the majority of animals the accumulation of calcium correlated to signs of neuronal necrosis. Since calcium accumulation was similar in all strata examined, the results failed to reveal preferential accumulation in dendritic or somal regions. Based on our results and those of Dux et al., we emphasize the possibility that delayed neuronal death is, at least in part, caused by increased calcium cycling of plasma membranes and gradual calcium overload of mitochondria.

scholarly journals Medial frontal theta is entrained to rewarded actions

2017 ◽  
Author(s):  
Linda M. Amarante ◽  
Marcelo S. Caetano ◽  
Mark Laubach
Keyword(s):  
Frontal Cortex ◽  
Theta Rhythm ◽  
Phase Locking ◽  
Medial Frontal Cortex ◽  
Male Rats ◽  
Cortical Region ◽  
Incentive Contrast ◽  
Opposite Hemisphere ◽  
Fluid Delivery ◽  
Reward Value

AbstractRodents lick to consume fluids. The reward value of ingested fluids is likely to be encoded by neuronal activity entrained to the lick cycle. Here, we investigated relationships between licking and reward signaling by the medial frontal cortex [MFC], a key cortical region for reward-guided learning and decision-making. Multi-electrode recordings of spike activity and field potentials were made in male rats as they performed an incentive contrast licking task. Rats received access to higher and lower value sucrose rewards over alternating 30 sec periods. They learned to lick persistently when higher value rewards were available and to suppress licking when lower value rewards were available. Spectral analysis of spikes and fields revealed evidence for reward value being encoded by the strength of phase-locking of a 6-12 Hz theta rhythm to the rats’ lick cycle. Recordings during the initial acquisition of the task found that the strength of phase-locking to the lick cycle was strengthened with experience. A modification of the task, with a temporal gap of 2 sec added between reward deliveries, found that the rhythmic signals persisted during periods of dry licking, a finding that suggests the MFC encodes either the value of the currently available reward or the vigor with which rats act to consume it. Finally, we found that reversible inactivations of the MFC in the opposite hemisphere eliminated the encoding of reward information. Together, our findings establish that a 6-12 Hz theta rhythm, generated by the rodent medial frontal cortex, is synchronized to rewarded actions.Significance StatementThe cellular and behavioral mechanisms of reward signaling by the medial frontal cortex [MFC] have not been resolved. We report evidence for a 6-12 Hz theta rhythm that is generated by the MFC and synchronized with ongoing consummatory actions. Previous studies of MFC reward signaling have inferred value coding upon temporally sustained activity during the period of reward consumption. Our findings suggest that MFC activity is temporally sustained due to the consumption of the rewarding fluids, and not necessarily the abstract properties of the rewarding fluid. Two other major findings were that the MFC reward signals persist beyond the period of fluid delivery and are generated by neurons within the MFC.

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