UNIT ACTIVITY IN THE PARAVENTRICULAR NUCLEUS OF FEMALE RATS AT DIFFERENT STAGES OF THE REPRODUCTIVE CYCLE AND AFTER OVARIECTOMY, WITH OR WITHOUT OESTROGEN OR PROGESTERONE TREATMENT

1973 ◽  
Vol 59 (3) ◽  
pp. 545-558 ◽  
Author(s):  
H. NEGORO ◽  
S. VISESSUWAN ◽  
R. C. HOLLAND
Keyword(s):  
Firing Rate ◽  
Paraventricular Nucleus ◽  
Reproductive Cycle ◽  
Refractory Period ◽  
Full Term ◽  
Ovariectomized Rats ◽  
Oestrogen Treatment ◽  
Absolute Refractory Period ◽  
Firing Rates ◽  
The Mean

SUMMARY Spontaneous firing rates were determined from extracellular recordings made from 878 antidromically identified units in the paraventricular nucleus (PVN) during the reproductive cycle of the female rat and in analytical experiments. In the latter, rats were ovariectomized and subsequently received either no treatment or oestrogen and/or progesterone. Among rats at metoestrus, dioestrus, mid-pregnancy and in ovariectomized progesterone-treated groups there was no significant difference in the firing rates. However, they were significantly lower than the rates recorded during pro-oestrus, oestrus, full-term pregnancy, the day of parturition, during lactation and in ovariectomized, oestrogen-treated rats. In spayed rats the mean firing rate was significantly lower than at pro-oestrus, oestrus, fullterm pregnancy, the 24 h period after parturition, during lactation and after oestrogen treatment. When progesterone was given subcutaneously to oestrogenized rats, the PVN activity, increased by oestrogen, was significantly depressed 4 h after administration. By 8 h the firing rate had completely recovered. The frequency distribution of the firing rates in pro-oestrus and oestrus showed an approximately normal distribution while those in metoestrus and dioestrus and mid-pregnancy had a Poisson distribution. At full term there were two peaks: one in the range of 3–5 spikes/s and the other less than one spike/s. The distribution was approximately normal on the day of parturition and subsequently the pattern became irregular. In ovariectomized rats and those treated with progesterone it was of a Poisson type while there was a distinct shift to higher frequencies after oestrogen treatment. The mean absolute refractory period, measured for each unit, varied and appears to be dependent on hormonal conditions. It was short in oestrus and long in dioestrus and mid-pregnancy. Oestrogen treatment significantly shortened the absolute refractory period of ovariectomized rats.

REFLEX ACTIVATION OF PARAVENTRICULAR NUCLEUS UNITS DURING THE REPRODUCTIVE CYCLE AND IN OVARIECTOMIZED RATS TREATED WITH OESTROGEN OR PROGESTERONE

1973 ◽  
Vol 59 (3) ◽  
pp. 559-567 ◽  
Author(s):  
H. NEGORO ◽  
S. VISESSUWAN ◽  
R. C. HOLLAND
Keyword(s):  
Firing Rate ◽  
Paraventricular Nucleus ◽  
Reproductive Cycle ◽  
Treated Group ◽  
Female Rats ◽  
Ovariectomized Rats ◽  
Spontaneous Firing ◽  
Pregnancy And Lactation ◽  
Pattern Of Variation ◽  
Vaginal Distension

SUMMARY Three hundred and seventy-seven neurones in the paraventricular nucleus (PVN) were antidromically identified in female rats during various stages of the reproductive cycle and in ovariectomized rats with or without oestrogen or progesterone pretreatment. The units were tested for their responses to vaginal distension and pinching of the foot. Unit responses to vaginal distension varied during the oestrous cycle, pregnancy and lactation. The percentages of PVN units recorded at each stage which increased their firing rate in response to vaginal distension were 64·1% in pro-oestrus, 56·7% in oestrus, 33·3% in metoestrus, 42·4% in dioestrus, 6·9% in mid-pregnancy (day 12) which was significantly lower than in any other stage or condition, 72·0% at full term, 55·5% immediately (<24 h) after parturition and 40·0% during lactation. Furthermore, when tested in mid-pregnancy, there was a period of interruption of spontaneous firing in 13·8% of PVN units during vaginal distension. The percentage of units which increased their firing rate during vaginal distension in ovariectomized rats was 42·4% and in ovariectomized, oestrogen-treated rats was 69·2% and thus significantly higher. While the percentage in progesterone-treated rats (35·1%) was not significantly different from that in ovariectomized rats, it was significantly lower than in the oestrogen-treated group. In addition, 18·9% of the units had a period of interruption of spontaneous firing in response to vaginal distension constituting the only group besides the mid-pregnancy group in which this was observed. Pinching the foot also excited PVN unit activity in some cases. It was more frequently evoked by pinching a foot contralateral to the PVN nucleus from which the recording was taken. The response to stimulation of the ipsilateral foot was weaker or absent. The responsiveness of PVN units to pinching varied throughout the reproductive cycle as well as in ovariectomized rats with or without treatment with oestrogen or progesterone. The pattern of variation was dissimilar from that observed after vaginal distension and the magnitude of variation was smaller. Interruption of spontaneous firing was observed in seven different groups.

Variability in somatosensory cortical neuron discharge: effects on capacity to signal different stimulus conditions using a mean rate code

1978 ◽  
Vol 41 (2) ◽  
pp. 338-349 ◽  
Author(s):  
R. C. Schreiner ◽  
G. K. Essick ◽  
B. L. Whitsel
Keyword(s):  
Firing Rate ◽  
Linear Equation ◽  
Cortical Neuron ◽  
Single Neuron ◽  
Rate Code ◽  
Firing Rates ◽  
Discrimination Criterion ◽  
The Mean ◽  
Change In Mean ◽  
The Relationship

1. The present study is based on the demonstration (8, 9) that the relationship between mean interval (MI) and standard deviation (SD) for stimulus-driven activity recorded from SI neurons is well fitted by the linear equation SD = a X MI + b and on the observations that the values of the slope (a) and y intercept (b) parameters of this relationship are independent of stimulus conditions and may vary widely from one neuron to the next (8). 2. A criterion for the discriminability of two different mean firing rates requiring that the mean intervals of their respective interspike interval (ISI) distributions be separated by a fixed interval (expressed in SD units) is developed and, on the basis of this criterion, a graphical display of the capacity of a neuron with a known SD-MI relationship to reflect a change in stimulus conditions with a change in mean firing rate is derived. Using this graphical approach, it is shown that the parameters of the SD-MI relationship for a single neuron determine a range of firing frequencies, within which that neuron exhibits the greatest capacity to signal differences in stimulus conditions using a frequency code. 3. The discrimination criterion is modified to incorporate the changes in the symmetry of the ISI distribution observed to accompany changes in mean firing rate. It is shown that, although the observed symmetry changes do influence the capacity of a cortical neuron to signal a change in stimulus conditions with a change in mean firing rate, they do not alter the range of firing rates (determined by the parameters of the SD-MI relationship) within which the capacity for discrimination is maximal. 4. The maximal number of firing levels that can be distinguished by a somatosensory cortical neuron (using the same discrimination criterion described above) discharging within a specified range of mean frequencies also is demonstrated to depend on the parameters of the linear equation which relates SD to MI. 5. Two approaches based on the t test for differences between two means are developed in an attempt to ascertain the minimum separation of the mean intervals of the ISI distributions necessary for two different mean firing rates to be discriminated with 80% certainty.

Activation of type-identified motor units during centrally evoked contractions in the cat medial gastrocnemius muscle. II. Motoneuron firing-rate modulation

1996 ◽  
Vol 75 (1) ◽  
pp. 38-50 ◽  
Author(s):  
K. E. Tansey ◽  
B. R. Botterman
Keyword(s):  
Firing Rate ◽  
Motor Unit ◽  
Muscle Force ◽  
Motor Units ◽  
Medial Gastrocnemius ◽  
Firing Rates ◽  
Rate Modulation ◽  
The Mean ◽  
Fast Twitch ◽  
The Relationship

1. The aim of this study was to examine the nature of motoneuron firing-rate modulation in type-identified motor units during smoothly graded contractions of the cat medial gastrocnemius (MG) muscle evoked by stimulation of the mesencephalic locomotor region (MLR). Motoneuron discharge patterns, firing rates, and the extent of firing-rate modulation in individual units were studied, as was the extent of concomitant changes in firing rates within pairs of simultaneously active units. 2. In 21 pairs of simultaneously active motor units, studied during 41 evoked contractions, the motoneurons' discharge rates and patterns were measured by processing the cells' recorded action potentials through windowing devices and storing their timing in computer memory. Once recruited, most motoneurons increased their firing rates over a limited range of increasing muscle tension and then maintained a fairly constant firing rate as muscle force continued to rise. Most motoneurons also decreased their firing rates over a slightly larger, but still limited, range of declining muscle force before they were derecruited. Although this was the most common discharge pattern recorded, several other interesting patterns were also seen. 3. The mean firing rate for slow twitch (type S) motor units (27.8 imp/s, 5,092 activations) was found to be significantly different from the mean firing rate for fast twitch (type F) motor units (48.4 imp/s, 11,272 activations; Student's t-test, P < 0.001). There was no significant difference between the mean firing rates of fast twitch, fatigue-resistant (type FR) and fast twitch, fatigable (type FF) motor units. When the relationship between motoneuron firing rate and whole-muscle force was analyzed, it was noted that, in general, smaller, lower threshold motor units began firing at lower rates and reached lower peak firing rates than did larger, higher threshold motor units. These results confirm both earlier experimental observations and predictions made by other investigators on the basis of computer simulations of the cat MG motor pool, but are in contrast to motor-unit discharge behavior recorded in some human motor-unit studies. 4. The extent of concomitant changes in firing rate within pairs of simultaneously active motor units was examined to estimate the extent of simultaneous motoneuron firing-rate modulation across the motoneuron pool. A smoothed (5 point sliding average) version of the two motoneurons' instantaneous firing rates was plotted against each other, and the slope and statistical significance of the relationship was determined. In 16 motor-unit pairs, the slope of the motoneurons' firing-rate relationship was significantly distinct from 0. Parallel firing-rate modulation (< 10-fold difference in firing rate change reflected by a slope of > 0.1) was noted only in pairs containing motor units of like physiological type and then only if they were of similar recruitment threshold. 5. Other investigators have demonstrated that changes in a motoneuron's "steady-state" firing rate predictably reflect changes in the amount of effective synaptic current that cell is receiving. The finding in the present study of limited parallel firing-rate modulation between simultaneously active motoneurons would suggest that changes in the synaptic drive to the various motoneurons of the pool is unevenly distributed. This finding, in addition to the findings of orderly motor-unit recruitment and the relationship between motor-unit recruitment threshold and motoneuron firing rate, cannot be adequately accommodated for by the existing models of the synaptic organization in motoneuron pools. Therefore a new model of the synaptic organization within the motoneuron pool has been proposed.

scholarly journals Neuronal firing rates diverge during REM and homogenize during non-REM

2016 ◽  
Author(s):  
Hiroyuki Miyawaki ◽  
Brendon Watson ◽  
Kamran Diba
Keyword(s):  
Firing Rate ◽  
Frontal Cortex ◽  
Rem Sleep ◽  
Cortical Neurons ◽  
Nrem Sleep ◽  
Regression To The Mean ◽  
Firing Rates ◽  
The Mean ◽  
High Firing ◽  
Interneuron Activity

AbstractNeurons fire at highly variable innate rates and recent evidence suggests that low and high firing rate neurons display different plasticity and dynamics. Furthermore, recent publications imply possibly differing rate-dependent effects in hippocampus versus neocortex, but those analyses were carried out separately and with possibly important differences. To more effectively synthesize these questions, we analyzed the firing rate dynamics of populations of neurons in both hippocampal CA1 and frontal cortex under one framework that avoids pitfalls of previous analyses and accounts for regression-to-the-mean. We observed remarkably consistent effects across these regions. While rapid eye movement (REM) sleep was marked by decreased hippocampal firing and increased neocortical firing, in both regions firing rates distributions widened during REM due to differential changes in high-firing versus low-firing cells in parallel with increased interneuron activity. In contrast, upon non-REM (NREM) sleep, firing rate distributions narrowed while interneuron firing decreased. Interestingly, hippocampal interneuron activity closely followed the patterns observed in neocortical principal cells rather than the hippocampal principal cells, suggestive of long-range interactions. Following these undulations in variance, the net effect of sleep was a decrease in firing rates. These decreases were greater in lower-firing hippocampal neurons but higher-firing frontal cortical neurons, suggestive of greater plasticity in these cell groups. Our results across two different regions and with statistical corrections indicate that the hippocampus and neocortex show a mixture of differences and similarities as they cycle between sleep states with a unifying characteristic of homogenization of firing during NREM and diversification during REM.Significance StatementMiyawaki and colleagues analyze firing patterns across low-firing and high-firing neurons in the hippocampus and the frontal cortex throughout sleep in a framework that accounts for regression-to-the-mean. They find that in both regions REM sleep activity is relatively dominated by high-firing neurons and increased inhibition, resulting in a wider distribution of firing rates. On the other hand, NREM sleep produces lower inhibition, and results in a more homogenous distribution of firing rates. Integration of these changes across sleep results in net decrease of firing rates with largest drops in low-firing hippocampal pyramidal neurons and high-firing neocortical principal neurons. These findings provide insights into the effects and functions of different sleep stages on cortical neurons.

Transmembrane potentials and atrial fibrillation

1960 ◽  
Vol 199 (2) ◽  
pp. 346-348 ◽  
Author(s):  
Richard L. Klein ◽  
William C. Holland
Keyword(s):  
Atrial Fibrillation ◽  
Ion Transport ◽  
Firing Rate ◽  
Electrical Excitation ◽  
Firing Rates ◽  
Transmembrane Potentials ◽  
Atrial Cells ◽  
Microelectrode Technique ◽  
The Mean

The mean maximum following frequency of single atrial cells as determined by the microelectrode technique was found to be 820/min. with a range of 600–1050. The mean ‘firing’ rate of atrial cells during acetylcholine induced fibrillation was 900/min. with a range of 600–1250/min. The data are interpreted to mean that the observed changes in ion transport during fibrillation are not the result of higher firing rates of atrial cells as compared to those during rapid electrical excitation.

Electrophysiological effects of testosterone on the medial preoptic–anterior hypothalamus of the rat

1983 ◽  
Vol 96 (1) ◽  
pp. 35-42 ◽  
Author(s):  
K. M. Kendrick
Keyword(s):  
Firing Rate ◽  
Conduction Velocity ◽  
Refractory Period ◽  
Medial Forebrain Bundle ◽  
Testosterone Propionate ◽  
Lateral Septum ◽  
Firing Rates ◽  
Additional Input ◽  
Corticomedial Amygdala ◽  
Electrophysiological Effects

Castration in the rat significantly lengthened the refractory period of medial preoptic–anterior hypothalamic neurones with outputs into the medial forebrain bundle but not of those with outputs to the lateral septum. Treatment with testosterone propionate reduced the neuronal refractory period to its lowest level at the same time as it restored mounts and intromissions (after 5 days). Equally, when treatment was ended at 15 days, mounts and intromissions were no longer shown when the refractory period lengthened again 14 days later. The sub-population of neurones which also received inputs from the contralateral fimbria (through the corticomedial amygdala) showed the same results as the overall population. Castration also significantly increased the baseline firing rates of medial preoptic–anterior hypothalamic neurones receiving inputs from the medial forebrain bundle. The same effect was observed for the sub-population of neurones which also had inputs from the contralateral fimbria, but castration significantly reduced the percentage of neurones responding to this additional input. The neurones having inputs with the fastest conduction velocity were responsible for these changes in firing rate and the input neurones were therefore probably non-dopaminergic.

Stimulation of single unit activity in the preoptic area and anterior hypothalamus, and secretion of luteinizing hormone, by ovarian steroids in ovariectomized rats with diencephalic islands

1982 ◽  
Vol 216 (1205) ◽  
pp. 461-473 ◽  
Keyword(s):  
Luteinizing Hormone ◽  
Firing Rate ◽  
Ovariectomized Rats ◽  
Lh Surge ◽  
Neural Connections ◽  
Recording Session ◽  
Subsequent Measurement ◽  
The Mean ◽  
Oil Injection ◽  
First Time

The spontaneous activity of 454 single hypothalamic neurons was recorded in 42 chronically ovariectomized rats after severance of all neural connections with the diencephalon. In 15 of these diencephalic island preparations progesterone was administered immediately before the recording session (and just after deafferentation of the diencephalon) and oestrogen 72 h beforehand. Thirteen rats were given two injections of oestrogen at these times and the remaining 14 rats were similarly treated with equal volumes of oil. Blood samples were obtained from all rats just before each hormone or oil injection, and 4, 5, 6 and 7 h after the second one, for subsequent measurement of plasma luteinizing hormone (LH) concentration. Only the group of rats given progesterone at the time of the second injection showed a significant increase in plasma LH concentration during the recording period. There was however some individual variation and the greatest LH surge was obtained from a rat given two injections of oestrogen. For steroid-treated rats the size of the LH surge was significantly correlated ( P < 0.01) with the mean firing rate of the neurons recorded in the preoptic and anterior hypothalamic areas (p. o. -a. h.). No similar correlation could be established for p. o. -a. h. cells recorded in oil-treated rats or for cells recorded in other parts of the hypothalamus in steroid-treated rats. The mean firing rate of all p. o. -a. h. cells recorded from rats treated with oestrogen followed by progesterone was significantly higher ( P < 0.05) than in either of the other two groups of animals. The oestrogen-progesterone treatment also significantly changed the regularity of discharge of the slow firing (< 2 Hz) p. o. -a. h. cells, but this phenomenon could not be related to any alteration in plasma LH concentration. The experiments have demonstrated for the first time that the magnitude of the steroid-stimulated LH surge in ovariectomized rats is significantly correlated with the increase in the electrical activity of p. o. -a. h. neurons.

Rate Limitations of Unitary Event Analysis

2000 ◽  
Vol 12 (9) ◽  
pp. 2063-2082 ◽  
Author(s):  
A. Roy ◽  
P. N. Steinmetz ◽  
E. Niebur
Keyword(s):  
Firing Rate ◽  
Random Variable ◽  
Event Analysis ◽  
Neural Firing ◽  
Time Intervals ◽  
Relative Variation ◽  
Firing Rates ◽  
Inhomogeneous Poisson Processes ◽  
The Mean ◽  
Unitary Events

Unitary event analysis is a new method for detecting episodes of synchronized neural activity (Riehle, Grüun, Diesmann, & Aertsen, 1997). It detects time intervals that contain coincident firing at higher rates than would be expected if the neurons fired as independent inhomogeneous Poisson processes; all coincidences in such intervals are called unitary events (UEs). Changes in the frequency of UEs that are correlated with behavioral states may indicate synchronization of neural firing that mediates or represents the behavioral state. We show that UE analysis is subject to severe limitations due to the underlying discrete statistics of the number of coincident events. These limitations are particularly stringent for low (0–10 spikes/s) firing rates. Under these conditions, the frequency of UEs is a random variable with a large variation relative to its mean. The relative variation decreases with increasing firing rate, and we compute the lowest firing rate, at which the 95% confidence interval around the mean frequency of UEs excludes zero. This random variation in UE frequency makes interpretation of changes in UEs problematic for neurons with low firing rates. As a typical example, when analyzing 150 trials of an experiment using an averaging window 100 ms wide and a 5ms coincidence window, firing rates should be greater than 7 spikes per second.

Adaptive changes in firing rates in goldfish auditory fibers as related to changes in mean amplitude of excitatory postsynaptic potentials

1983 ◽  
Vol 50 (3) ◽  
pp. 573-581 ◽  
Author(s):  
M. Kuno
Keyword(s):  
Firing Rate ◽  
Linear Relation ◽  
Mean Amplitude ◽  
Excitatory Postsynaptic Potentials ◽  
Adaptive Changes ◽  
Postsynaptic Potentials ◽  
Firing Rates ◽  
Threshold Amplitude ◽  
The Mean ◽  
Probabilistic Nature

Relationship between the firing rate in the auditory fibers and the amplitude of the excitatory postsynaptic potentials (EPSPs) that trigger afferent impulses was investigated. The unitary EPSPs and spike potentials were extracellularly recorded from the goldfish large auditory fibers by means of a microelectrode placed close to the distal terminals. The relation between the firing rate and the amplitude of the EPSPs was studied using a variety of stimulus conditions. The firing probability of phase-locked impulses was linearly related to the mean amplitude of the EPSPs determined for the same time bins. The same linear relation was applicable for the firings elicited by different intensities of sound and observed at various times after onset and also for the firings produced by applying step increments in intensity. The threshold amplitude of the EPSPs required for initiation of afferent impulses was unchanged in these different situations. Random changes in the amplitude of successively evoked EPSPs were found to underlie the probabilistic nature of the sequence of afferent firings. The present results indicate that the per stimulus adaptation and incremental and decremental responses, as observed in the firing probability of afferent impulses, are largely attributable to adaptive changes in the mean amplitude of the evoked EPSPs and not to changes in excitability of the auditory fibers.

Control of colonic motility using electrical stimulation to modulate enteric neural activity

2021 ◽  
Author(s):  
Bradley Barth ◽  
Lee Travis ◽  
Nick J Spencer ◽  
Warren M. Grill
Keyword(s):  
Electrical Stimulation ◽  
Refractory Period ◽  
Colonic Motility ◽  
Gastrointestinal Transit ◽  
Absolute Refractory Period ◽  
Refractory Periods ◽  
Colonic Motor ◽  
The Mean ◽  
Insight Into

Electrical stimulation of the enteric nervous system (ENS) is an attractive approach to modify gastrointestinal transit. Colonic motor complexes (CMCs) occur with a periodic rhythm, but the ability to elicit a premature CMC depends, at least in part, upon the intrinsic refractory properties of the ENS, which are presently unknown. The objectives of this study were to record myoelectric complexes (MCs, the electrical correlates of CMCs) in the smooth muscle and (i) determine the refractory periods of MCs, (ii) inform and evaluate closed-loop stimulation to repetitively evoke MCs, and (iii) identify stimulation methods to suppress MC propagation. We dissected the colon from male and female C57BL/6 mice, preserving the integrity of intrinsic circuitry while removing the extrinsic nerves, and measured properties of spontaneous and evoked MCs in vitro. Hexamethonium abolished spontaneous and evoked MCs, confirming the necessary involvement of the ENS for electrically-evoked MCs. Electrical stimulation reduced the mean interval between evoked and spontaneous CMCs (24.6 ± 3.5 vs 70.6 ± 15.7 s, p = 0.0002, n = 7). The absolute refractory period was 4.3 s (95% CI = 2.8 - 5.7 s, R2 = 0.7315, n = 8). Electrical stimulation applied during fluid distention-evoked MCs led to an arrest of MC propagation, and following stimulation, MC propagation resumed at an increased velocity (n = 9). The timing parameters of electrical stimulation increased the rate of evoked MCs and the duration of entrainment of MCs, and the refractory period provides insight into timing considerations for designing neuromodulation strategies to treat colonic dysmotility.

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