scholarly journals Generation and Propagation of Subthreshold Waves in a Network of Inferior Olivary Neurons

2002 ◽  
Vol 87 (6) ◽  
pp. 3059-3069 ◽  
Author(s):  
Anna Devor ◽  
Yosef Yarom
Keyword(s):  
Optical Imaging ◽  
Phase Difference ◽  
Maximum Amplitude ◽  
Nmda Receptor Antagonist ◽  
Oscillatory Activity ◽  
Electrotonic Coupling ◽  
Cell Pair ◽  
Subthreshold Oscillations ◽  
High Level ◽  
Inferior Olivary

The cells of the inferior olivary (IO) nucleus generate a large repertoire of electrical signals, among them subthreshold oscillations of the membrane potential (STO). To date, subthreshold oscillations have been studied at the level of single-cell recordings, from which network properties were inferred. In this study we used whole cell patch recordings and optical imaging to address the following issues: 1) synchrony of STO in neighboring neurons; 2) stability of the oscillatory activity in the temporal and spatial domain; and 3) the size of the oscillating network. Recordings were made from 126 pairs of IO neurons in 13- to 30-day-old rats. An additional 262 neurons were recorded individually. The frequency of STO varied from 0.8 to 8.6 Hz. The frequency distribution revealed two subpopulations with peaks at about 3 and 6 Hz. The maximum amplitude among the cells varied from 2 to 25 mV. Oscillations in most neurons showed ongoing modulations in both frequency and amplitude. These modulations were largely abolished following bath application of 40 μM 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX), a competitive non– N-methyl-d-aspartate (non-NMDA) receptor antagonist, suggesting that they were caused by glutamatergic action. In 35 of 61 recorded pairs at least one neuron exhibited STO permitting us to compare frequency and phase relations. In 22 pairs there was coherent activity with zero phase difference between oscillations in the 2 cells. In these pairs, frequency and amplitude modulation occurred simultaneously in both neurons. Electrotonic coupling was tested in 13 pairs, that had coherent STO, and it was detected in 12. An additional seven pairs showed coherent oscillations but with a phase difference of 20–50 ms. Electrotonic coupling was observed in three of these pairs. Electrotonic coupling was also observed in two of five pairs in which only one neuron oscillated. No coupling was detected in one pair where both neurons oscillated but at different frequencies. Optical imaging using a voltage-sensitive dye (RH 414) was performed on 40 IO slices using an array of 128 photodiodes. Patches of oscillatory activity were observed in 10 slices. Among them six showed spontaneous oscillations, and four exhibited oscillations following extracellular stimulation. In agreement with cell pair recording, optical imaging demonstrated phase-shifted activity in the form of propagating waves of activity within an oscillating patch. We conclude that 1) STO exhibit ongoing modulations of frequency and amplitude that are probably caused by extrinsic inputs to the IO nucleus; 2) electrotonically coupled neurons show a high level of STO synchrony; and 3) the oscillatory activity can propagate within a network of coupled olivary neurons.

Subthreshold oscillations of the membrane potential: a functional synchronizing and timing device

1993 ◽  
Vol 70 (5) ◽  
pp. 2181-2186 ◽  
Author(s):  
I. Lampl ◽  
Y. Yarom
Keyword(s):  
Membrane Potential ◽  
Logic Gate ◽  
Maximum Amplitude ◽  
Sine Wave ◽  
Inferior Olivary Nucleus ◽  
Synaptic Potential ◽  
Synaptic Potentials ◽  
Subthreshold Oscillations ◽  
Inferior Olivary ◽  
Olivary Nucleus

1. Subthreshold membrane potential oscillations have been observed in different types of CNS neurons. In this in vitro study, we examined the possible role of these oscillations by analyzing the responses of neurons from the inferior olivary nucleus to a combined stimulation of sine wave and synaptic potentials. 2. A nonlinear summation of the sine wave and the synaptic potential occurred in olivary neurons; a superlinear summation occurred when the synaptic potential was elicited at the trough of the sine wave or during the rising phase. On the other hand, a less than linear summation occurred when the synaptic potentials were evoked during the falling phase of the wave. 3. Significant changes in the delay of the synaptic responses were observed. As a result of these changes, the maximum amplitude of the response occurred at the peak of the sine wave, regardless of the exact time of stimulation. The output of the neuron was therefore synchronized with the sine wave and depended only partly on the input phase. 4. These data demonstrate that neurons from the inferior olivary nucleus are capable of operating as accurate synchronizing devices. Moreover, by affecting the delay line, they act as a logic gate that ensures that the information will be added to the system only at given times.

Electrotonic Coupling in the Inferior Olivary Nucleus Revealed by Simultaneous Double Patch Recordings

2002 ◽  
Vol 87 (6) ◽  
pp. 3048-3058 ◽  
Author(s):  
Anna Devor ◽  
Yosef Yarom
Keyword(s):  
Coupling Coefficient ◽  
Direct Calculation ◽  
Physiological Data ◽  
Inferior Olivary Nucleus ◽  
Potential Oscillations ◽  
Electrotonic Coupling ◽  
Cell Pair ◽  
Coupling Resistance ◽  
The Difference ◽  
Inferior Olivary

Electrotonic coupling in the inferior olivary (IO) nucleus is assumed to play a crucial role in generating the subthreshold membrane potential oscillations in olivary neurons and in synchronizing climbing fiber input into the cerebellar cortex. We studied the strength and spatial distribution of the coupling by simultaneous double patch recordings from olivary neurons in the brain slice preparation. Electrotonic coupling was observed in 50% of the cell pairs. The coupling coefficient ( CC), defined as the ratio between voltage responses of the post- and the prejunctional cell, varied between 0.002 and 0.17; most of the pairs were weakly coupled. In more than 75% of the pairs, the CCwas <0.05. The coupling resistance varied between 0.7 to 19.8 GΩ, and 68% of the values fell between 0.7 to 8 GΩ. The difference between the coupling coefficient measured on stimulation of cell 1 or cell 2 of a coupled pair was 27 ± 16%. Direct calculation of the coupling resistance revealed an asymmetry of 24 ± 12%, suggesting a directional preference of coupling. The coupling was voltage independent, although depolarization of either the pre- or the postjunctional neuron reduced the CC. The chance of a cell pair being coupled was 80% in immediate neighboring cells, but dropped to about 30% at a distance of 40 μm. No coupled pairs were observed at distances larger than 70 μm. In 52% of staining experiments neurobiotin injection into an olivary neuron produced indirect labeling of 1–11 nearby cells with an average of 3.8 ± 2.9. All indirectly labeled cells were found in, or immediately adjacent, to the dendritic field of the directly stained neuron. Two distinct morphological types of olivary neurons, “curly” and “straight” cells, were found. In each case all neurons stained indirectly by dye passage through gap junctions belonged to the same type. Using the physiological data we estimated that each olivary neuron is directly coupled to about 50 neurons. Since somatic recordings may not reveal coupling through remote dendrites, we conclude that each neuron is directly connected to ≥50 neurons forming two distinct networks of curly and straight cells.

scholarly journals The Rapid Extraction of Gist—Early Neural Correlates of High-level Visual Processing

2012 ◽  
Vol 24 (2) ◽  
pp. 521-529 ◽  
Author(s):  
Frank Oppermann ◽  
Uwe Hassler ◽  
Jörg D. Jescheniak ◽  
Thomas Gruber
Keyword(s):  
Visual Processing ◽  
Time Course ◽  
Occipital Cortex ◽  
Stimulus Onset ◽  
Gamma Band ◽  
Oscillatory Activity ◽  
Rapid Extraction ◽  
The Right ◽  
High Level ◽  
Individual Objects

The human cognitive system is highly efficient in extracting information from our visual environment. This efficiency is based on acquired knowledge that guides our attention toward relevant events and promotes the recognition of individual objects as they appear in visual scenes. The experience-based representation of such knowledge contains not only information about the individual objects but also about relations between them, such as the typical context in which individual objects co-occur. The present EEG study aimed at exploring the availability of such relational knowledge in the time course of visual scene processing, using oscillatory evoked gamma-band responses as a neural correlate for a currently activated cortical stimulus representation. Participants decided whether two simultaneously presented objects were conceptually coherent (e.g., mouse–cheese) or not (e.g., crown–mushroom). We obtained increased evoked gamma-band responses for coherent scenes compared with incoherent scenes beginning as early as 70 msec after stimulus onset within a distributed cortical network, including the right temporal, the right frontal, and the bilateral occipital cortex. This finding provides empirical evidence for the functional importance of evoked oscillatory activity in high-level vision beyond the visual cortex and, thus, gives new insights into the functional relevance of neuronal interactions. It also indicates the very early availability of experience-based knowledge that might be regarded as a fundamental mechanism for the rapid extraction of the gist of a scene.

scholarly journals Low-Amplitude Oscillations in the Inferior Olive: A Model Based on Electrical Coupling of Neurons With Heterogeneous Channel Densities

1997 ◽  
Vol 77 (5) ◽  
pp. 2736-2752 ◽  
Author(s):  
Yair Manor ◽  
John Rinzel ◽  
Idan Segev ◽  
Yosef Yarom
Keyword(s):  
Inferior Olive ◽  
Electrical Coupling ◽  
The Other ◽  
Sustained Oscillation ◽  
Large Coupling ◽  
Model Based ◽  
Subthreshold Oscillations ◽  
Coupling Current ◽  
Low Amplitude ◽  
Inferior Olivary

Manor, Yair, John Rinzel, Idan Segev, and Yosef Yarom. Low-amplitude oscillations in the inferior olive: a model based on electrical coupling of neurons with heterogeneous channel densities. J. Neurophysiol. 77: 2736–2752, 1997. The mechanism underlying subthreshold oscillations in inferior olivary cells is not known. To study this question, we developed a single-compartment, two-variable, Hodgkin-Huxley-like model for inferior olive neurons. The model consists of a leakage current and a low-threshold calcium current, whose kinetics were experimentally measured in slices. Depending on the maximal calcium and leak conductances, we found that a neuron model's response to current injection could be of four qualitatively different types: always stable, spontaneously oscillating, oscillating with injection of current, and bistable with injection of current. By the use of phase plane techniques, numerical integration, and bifurcation analysis, we subdivided the two-parameter space of channel densities into four regions corresponding to these behavioral types. We further developed, with the use of such techniques, an empirical rule of thumb that characterizes whether two cells when coupled electrically can generate sustained, synchronized oscillations like those observed in inferior olivary cells in slices, of low amplitude (0.1–10 mV) in the frequency range 4–10 Hz. We found that it is not necessary for either cell to be a spontaneous oscillator to obtain a sustained oscillation. On the other hand, two spontaneous oscillators always form an oscillating network when electrically coupled with any arbitrary coupling conductance. In the case of an oscillating pair of electrically coupled nonidentical cells, the coupling current varies periodically and is nonzero even for very large coupling values. The coupling current acts as an equalizing current to reconcile the differences between the two cells' ionic currents. It transiently depolarizes one cell and/or hyperpolarizes the other cell to obtain the regenerative response(s) required for the synchronized oscillation. We suggest that the subthreshold oscillations observed in the inferior olive can emerge from the electrical coupling between neurons with different channel densities, even if the inferior olive nucleus contains no or just a small proportion of spontaneously oscillating neurons.

GABAergic and Glutamatergic Modulation of Spontaneous and Motor-Cortex-Evoked Complex Spike Activity

2002 ◽  
Vol 87 (4) ◽  
pp. 1993-2008 ◽  
Author(s):  
Eric J. Lang
Keyword(s):  
Motor Cortex ◽  
Banding Pattern ◽  
Spike Activity ◽  
Afferent Input ◽  
Excitatory Input ◽  
Relative Strength ◽  
Spike Synchrony ◽  
Complex Spike ◽  
Electrotonic Coupling ◽  
Inferior Olivary

Olivocerebellar activity is organized such that synchronous complex spikes occur primarily among Purkinje cells located within the same parasagittally oriented strip of cortex. Previous findings have shown that this synchrony distribution is modulated by the release of GABA and glutamate within the inferior olive, which probably act by controlling the efficacy of the electrotonic coupling between olivary neurons. The relative strengths of these two neurotransmitters in modulating the patterns of synchrony were compared by obtaining multiple electrode recordings of spontaneous crus 2a complex spike activity during intraolivary injection of solutions containing a GABAA (picrotoxin) and/or AMPA [1,2,3,4-tetrahydro-6-nitro-2,3-dioxo-benzo[f]quinoxaline-7-sulfonamide disodium (NBQX)] receptor antagonist. Injection of either antagonist led to increased synchrony between cells located within the same parasagittally oriented ≈250-μm-wide cortical strip. Picrotoxin also increased complex spike synchrony among cells located in different cortical strips, leading to a less prominent banding pattern, whereas injections of NBQX tended to decrease complex spike synchrony among such cells, enhancing the banding pattern. The relative strength of these two classes of olivary afferents was assessed by first injecting one of the antagonists alone and then in combination with the other. The enhanced banding pattern of complex spike synchrony following injection of NBQX alone remained during the subsequent combined injection of both antagonists. Furthermore, the widespread synchronization of complex spike activity following injection of picrotoxin alone was partially or completely reversed by combined injection of picrotoxin and NBQX. Changes in the climbing fiber reflex induced by the intraolivary injections paralleled the changes observed for spontaneous complex spike activity, indicating that the effects of picrotoxin and NBQX on the synchrony distribution reflect changes in the pattern of effective coupling of inferior olivary neurons and demonstrating that synchronous complex spike activity does not require simultaneous excitatory input to olivary cells. Finally the pattern of synchrony during motor cortical stimulation was examined. It was found that the patterns of synchrony for motor-cortex-evoked complex spike activity were similar to those of spontaneous activity, indicating an important role for electrotonic coupling in determining the response of the olivocerebellar system to afferent input. Moreover, intraolivary injections of picrotoxin increased the spatial distribution of the evoked response. In sum, the results provide evidence for the hypothesis that electrotonic coupling of inferior olivary neurons via gap junctions is the mechanism underlying complex spike synchrony and that this coupling plays an important role in determining the responses of the olivocerebellar system to synaptic input.

scholarly journals Serotonin suppresses subthreshold and suprathreshold oscillatory activity of rat inferior olivary neurones in vitro

2000 ◽  
Vol 524 (3) ◽  
pp. 833-851 ◽  
Author(s):  
Dimitris G. Placantonakis ◽  
Cornelius Schwarz ◽  
John P. Welsh
Keyword(s):  
Oscillatory Activity ◽  
Inferior Olivary

Increased Electrotonic Coupling in Spinal Motoneurons After Transient Botulinum Neurotoxin Paralysis in the Neonatal Rat

2003 ◽  
Vol 89 (2) ◽  
pp. 793-805 ◽  
Author(s):  
Angel M. Pastor ◽  
George Z. Mentis ◽  
Rosa R. De la Cruz ◽  
Eugenia Díaz ◽  
Roberto Navarrete
Keyword(s):  
Neuromuscular Transmission ◽  
Botulinum Neurotoxin ◽  
Maximum Amplitude ◽  
Neonatal Rat ◽  
Intracellular Recordings ◽  
Light Microscope Level ◽  
Electrotonic Coupling ◽  
Junctional Coupling ◽  
Gap Junctional ◽  
Gap Junctional Coupling

The effect of early postnatal blockade of neuromuscular transmission using botulinum neurotoxin (BoNT) type A on motoneuron gap junctional coupling was studied by means of intracellular recordings and biocytin labeling using the in vitro hemisected spinal cord preparation of neonatal rats. The somata of tibialis anterior (TA) motoneurons were retrogradely labeled at birth (P0) by intramuscular injection of fluorescent tracers. Two days later, BoNT was injected unilaterally into the TA muscle. The toxin blocked neuromuscular transmission for the period studied (P4–P7) as shown by tension recordings of the TA muscle. Retrograde horseradish peroxidase tracing in animals reared to adulthood demonstrated no significant cell death or changes in the soma size of BoNT-treated TA motoneurons. Intracellular recordings were carried out in prelabeled control and BoNT-treated TA motoneurons from P4 to P7. Graded stimulation of the ventral root at subthreshold intensities elicited short-latency depolarizing (SLD) potentials that consisted of several discrete components reflecting electrotonic coupling between two or more motoneurons. BoNT treatment produced a significant increase (67%) in the maximum amplitude of the SLD and in the number of SLD components as compared with control (3.1 ± 1.7 vs. 1.4 ± 0.7; means ± SD). The morphological correlates of electrotonic coupling were investigated at the light microscope level by studying the transfer of biocytin to other motoneurons and the putative sites of gap junctional interaction. The dye-coupled neurons clustered around the injected cell with close somato-somatic, dendro-somatic and -dendritic appositions that might represent the sites of electrotonic coupling. The size of the motoneuron cluster was, on average, 2.2 times larger after BoNT treatment. Our findings demonstrate that a short-lasting functional disconnection of motoneurons from their target muscle delays motoneuron maturation by halting the elimination of gap junctional coupling that normally occurs during early postnatal development.

Differential electroresponsiveness of stellate and pyramidal-like cells of medial entorhinal cortex layer II

1993 ◽  
Vol 70 (1) ◽  
pp. 128-143 ◽  
Author(s):  
A. Alonso ◽  
R. Klink
Keyword(s):  
Membrane Potential ◽  
Entorhinal Cortex ◽  
Morphological Characteristics ◽  
Oscillatory Activity ◽  
Inward Rectification ◽  
Projection Neurons ◽  
Medial Entorhinal Cortex ◽  
Mean Frequency ◽  
Subthreshold Oscillations

1. The electroresponsive properties of neurons from layer II of the rat medial entorhinal cortex (MEC) were studied by intracellular recording under current clamp in an in vitro brain slice preparation. From a total of 184 cells that fulfilled our criteria for recording stability, two groups of projection neurons were distinguished on the basis of their intrinsic biophysical properties and morphological characteristics (demonstrated by intracellular biocytin injection; n = 34). 2. Stellate cells (SCs) were the most abundant (69%). They were highly electroresponsive, and minimal changes (1-3 mV) of membrane potential generated an active response. Subthreshold depolarizing or hyperpolarizing current pulse injection always caused the membrane potential to attain an early peak and then sag to a lower level. Depolarization-induced "sags" were larger and determined early firing in all cells. The voltage-current relationship of SCs was markedly non-linear, demonstrating robust inward rectification in the hyperpolarizing and depolarizing range. 3. SCs generated persistent rhythmic subthreshold voltage oscillations on DC depolarization positive to -60 mV. The mean frequency of the oscillations was 8.6 Hz (theta range) at a membrane potential of approximately -55 mV, at which level occasional single spiking also occurred. At slightly more positive potentials, a striking 1- to 3-Hz repetitive bursting pattern emerged. This consisted of nonadapting trains of spikes ("clusters") interspersed with subthreshold oscillations that had a mean frequency of 21.7 Hz (beta range). 4. Nonstellate cells (39%; mostly pyramidal-like) displayed time-dependent inward rectification that was less pronounced than that of SCs, and minimal depolarization-induced sags. On threshold depolarization, firing was always preceded by a slowly rising ramp depolarization and thus occurred with a long delay. Inward rectification in the depolarizing range was very pronounced. However, non-SCs did not generate persistent rhythmic subthreshold oscillatory activity or spike clusters. 5. Of the electrophysiological parameters quantified, spike threshold, spike duration, depolarizing afterpotential amplitude and apparent membrane time constant demonstrated statistically significant differences between SCs and non-SCs. 6. The repetitive hiring properties in response to square current pulses of short duration (< 500 ms) were also different between SCs and non-SCs. First, most SCs displayed a bilinear frequency-current (f-I) relationship for only the first interspike interval, whereas most non-SCs displayed a bilinear relationship for all intervals. Second, SCs had a much steeper primary f-I slope for early intervals than non-SCs. Finally, SCs displayed more pronounced and faster spike frequency adaptation than non-SCs.(ABSTRACT TRUNCATED AT 400 WORDS)

Local/Global Effects of Mistuning on the Forced Response of Bladed Disks

2004 ◽  
Vol 126 (1) ◽  
pp. 131-141 ◽  
Author(s):  
A. J. Rivas-Guerra ◽  
M. P. Mignolet
Keyword(s):  
Maximum Amplitude ◽  
High Accuracy ◽  
Forced Response ◽  
Entire Population ◽  
Modeling Technique ◽  
Bladed Disks ◽  
High Level

The focus of the present investigation is on the assessment and modeling of the local (spanning only a few blades) and global (encompassing the entire disk) effects of mistuning on the forced response of bladed disks. To this end, the concept of localization is first revisited and a new measure of this effect is introduced in terms of the number of blades the mistuning of which actually affects the forced response of a central blade. Using this new metric, it is demonstrated that high responding blades typically exhibit a high level of localization and that the reverse is not necessarily true. Thus, localization is not only disk dependent but also varies from blade-to-blade on the same disk. This observation is then used to validate a partial mistuning approach to the determination of the maximum amplitude of response over the entire population of disks. The results of this study indicate that the largest amplification due to the mistuning occurs at very strong blade-to-blade coupling levels, at the contrary of a general perception, but is associated with large mistuning levels. Finally, the above phenomenological observations are used to devise a modeling technique of both local and global components of mistuning. An example of application is presented that demonstrates the high accuracy of this approach through the entire blade-to-blade coupling domain.

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