The effects of changing levels of arousal on the spontaneous activity of cortical neurones II. Relaxation and alarm

1976 ◽  
Vol 194 (1115) ◽  
pp. 239-251 ◽  
Keyword(s):  
Spontaneous Activity ◽  
Temporal Pattern ◽  
Discharge Rate ◽  
Geometric Standard Deviation ◽  
Sudden Increase ◽  
Lateral Cortex ◽  
Infrared Telescope ◽  
Modal Interval ◽  
Log Normal ◽  
Two Parameters

In a previous paper it has been shown that interval distributions derived from the activity of single cortical neurones can be described by log-normal curves. A cell’s temporal pattern of discharge can therefore be defined by the values of two parameters – a modal interval, and a geometric standard deviation (g. s. d.). It has also been shown that the values of both parameters change when an animal falls asleep. The modal interval becomes shorter, and the g. s. d. usually becomes larger. This paper deals with the effects of changes in arousal of animals which are awake; and, in particular, with the effects of the transition from relaxation to alarm. Single unit recordings have been made from neurones in the post-lateral and supra-sylvian gyri of unrestrained cats. In order to eliminate the direct effects of eye-movements, the experiments were carried out in complete darkness, and the animal was observed through an infrared telescope. Alarm was produced by the hiss of compressed air. An animal was said to be alarmed when he stood up abruptly and turned towards the source of the noise. Alarm produced a marked fall in the discharge frequency of those cells in post-lateral cortex which initially showed a low ( < 2 action potentials per second) rate of spontaneous activity. The discharge rate of the remaining neurones (whether in suprasylvian or post-lateral cortex) was unaffected by the sudden increase in arousal. But the temporal pattern of discharge of every cell was altered. The modal interval became longer when the animal was alarmed, and the g. s. d. usually became smaller. Such changes could have been predicted from a knowledge of the neural concomitants of the transition from sleep to wakefulness. These results suggest that the activity of all cortical neurones is affected by the level of arousal of the animal, and that this modulation takes the form of a continuum of possible modal intervals, and possible g.s.ds.

The spontaneous activity of neurones in the cat’s cerebral cortex

1976 ◽  
Vol 194 (1115) ◽  
pp. 211-223 ◽  
Keyword(s):  
Standard Deviation ◽  
Action Potentials ◽  
Quantitative Description ◽  
Primary Auditory Cortex ◽  
Geometric Standard Deviation ◽  
Quiet Sleep ◽  
Modal Interval ◽  
Spontaneous Action ◽  
Log Normal ◽  
Two Parameters

Chronically implanted microelectrodes have been used to obtain extracellular records of trains of spontaneous action potentials from 30 neurones in the cerebral cortices of 13 unrestrained cats. Recorded neurones were in or near to primary visual cortex, primary auditory cortex, and in the supra-sylvian gyrus. Records were made with animals in several different behavioural states, which included sleep with rapid eye-movements and quiet sleep, peacefully awake, and alarmed. Interval distributions derived from trains of 200 action potentials recorded in less than 80 s did not differ significantly from curves in which the probability of any interval is normally distributed about a modal interval, when plotted on a logarithmic time-axis. Thus the complete interval distributions of neurones firing faster than 2.5/s can be described by two parameters – a modal interval, and a geometric standard deviation. This quantitative description of interval distributions proved equally applicable to neurones in all three cortical areas and was valid over the whole range of behavioural states examined. It does not usually hold when the discharge frequency of a neurone is lower than 2.5 action potentials per second. An acceptable fit for a log-normal curve can then only be obtained for intervals that are shorter than about ten times the modal interval. It is pointed out that mean frequency of discharge is a measure of neural activity which is a secondary parameter, since it is dependent upon both modal interval and geometric standard deviation. Our preliminary data show that the two parameters which define the best-fit log-normal curves can vary independently with the behavioural state of the animal in a way that suggests that they may be physiologically important.

The effects of changing levels of arousal on the spontaneous activity of cortical neurones I. Sleep and wakefulness

1976 ◽  
Vol 194 (1115) ◽  
pp. 225-237 ◽  
Keyword(s):  
Preceding Paper ◽  
Geometric Standard Deviation ◽  
Modal Interval ◽  
Efficient Test ◽  
Single Neurones ◽  
Single Interval ◽  
Log Normal ◽  
Two Parameters ◽  
Interval Distribution ◽  
Comparative Measure

In the preceding paper (Burns & Webb 1976), it was shown that the interval distributions derived from the activity of single cortical neurones can be described by log-normal curves. This description proved satisfactory for cells in visual parietal and auditory cortex. Thus, two parameters – a modal interval and a geometric standard deviation (g. s. d.) – are sufficient to define the whole temporal pattern of discharge for neurones that fire faster than 2.5/s. The same two parameters may be used to describe the first parts of the interval distributions of cells firing less frequently. The purpose of the present paper is to find out whether the values of these two parameters vary systematically with an animal’s state of alertness. Records have therefore been made from single neurones in various parts of the cerebral cortex of unrestrained male cats, when the animals were awake and when they were sleeping. A cat was said to be asleep when he lay with his head supported by some part of the apparatus, with eyes shut, and pinnae unresponsive to laboratory noises. R. e. m. sleep was identified by jerky movements of limbs and eyes. If one records from the same neurone when the cat is awake and when he is asleep, the values of both mode and g. s. d. change with the onset of sleep. Thus either parameter will provide a comparative measure of the animal’s state of alertness. On average the modal interval shortens by a factor of three when an animal falls asleep. This coincides with an increase of 42 % in the size of the g. s. d. The geometric coefficient of variation, which is a dimensionless measure of scatter about the mode - g. c. v. = [log (g. s. d. )]/[log (modal interval)] - also showed systematic changes. On average the g. c. v. increased by a factor of 2.4 when an animal fell asleep. The animal’s state of arousal could also be assessed by examining a single train of action potentials. Interval distributions with modal intervals which are shorter than 20 ms appear to be characteristic of neural activity recorded from a sleeping cat. This rule offers an 88 % chance of successfully classifying a single interval distribution. The size of the g. c. v. can also serve as an efficient ‘test’ of arousal. If one assumes that g. c. vs larger than 0.32 are diagnostic of records taken from animals which are asleep, one’s chance of making an accurate classification is also 88 %. No similar distinction could be made between quiet and r. e. m. sleep.

The effects of sleep on neurons in isolated cerebral cortex

1979 ◽  
Vol 206 (1164) ◽  
pp. 281-291 ◽  
Keyword(s):  
Cerebral Cortex ◽  
Neural Activity ◽  
Geometric Standard Deviation ◽  
Neural Connections ◽  
Modal Interval ◽  
Isolated Cortex ◽  
Log Normal ◽  
Intact Cortex ◽  
The Brain ◽  
Unrestrained Animal

Slabs of cat parietal cortex with some 2 mm of underlying white matter were surgically isolated from the rest of the nervous system, without interference with the superficial blood supply. Wire micro-recording electrodes were inserted into the isolated cortex; bone, muscle and skin wounds were repaired and the animal allowed to recover from anaesthesia. The adequacy of surgical isolation was examined histologically 8-12 weeks after operation. Only one of the six preparations reported here showed surviving neural connections with the rest of the brain. Soon after operation, spontaneous bursts of neural activity appeared within the isolated area. These became more frequent until neural dis­charge was continuous but irregular. Our records were made from this time onwards. The interval distributions obtained from neurons within the isolated area did not differ significantly from log-normal curves. When the unrestrained animal fell asleep, there was no significant alteration in the modal interval or geometric standard deviation of interval distributions recorded from cells in isolated cortex. The interval distributions of neurons in isolated cerebral cortex resembled those of neurons in the intact cortex of an alarmed animal. It is concluded that the reduction of modal interval that is shown by neurons in intact cortex when an animal falls asleep is probably due to the neural influence of infracortical structures.

Prediction of Haemoglobin Level by Some Probability Distribution

2020 ◽  
Vol 9 (1) ◽  
pp. 84-88
Author(s):  
Govinda Prasad Dhungana ◽  
Laxmi Prasad Sapkota
Keyword(s):  
Probability Distribution ◽  
Normal Distribution ◽  
Goodness Of Fit ◽  
Continuous Variable ◽  
Hemoglobin Level ◽  
Chi Square ◽  
Chi Square Test ◽  
Log Normal ◽  
Two Parameters ◽  
Best Fit

 Hemoglobin level is a continuous variable. So, it follows some theoretical probability distribution Normal, Log-normal, Gamma and Weibull distribution having two parameters. There is low variation in observed and expected frequency of Normal distribution in bar diagram. Similarly, calculated value of chi-square test (goodness of fit) is observed which is lower in Normal distribution. Furthermore, plot of PDFof Normal distribution covers larger area of histogram than all of other distribution. Hence Normal distribution is the best fit to predict the hemoglobin level in future.

Development of spontaneous activity and mechanosensitivity in axotomized afferent nerve fibers during the first hours after nerve transection in rats

1995 ◽  
Vol 74 (3) ◽  
pp. 1020-1027 ◽  
Author(s):  
M. Michaelis ◽  
K. H. Blenk ◽  
W. Janig ◽  
C. Vogel
Keyword(s):  
Spontaneous Activity ◽  
Discharge Rate ◽  
Nerve Fibers ◽  
Nerve Lesion ◽  
Nerve Transection ◽  
Unmyelinated Fibers ◽  
C Fibers ◽  
Afferent Nerve Fibers ◽  
Irregular Frequency ◽  
The Mean

1. Spontaneous activity and ectopic mechanical excitability of axotomized unmyelinated and myelinated fibers in the sural nerve were examined in anesthetized rats. The analysis was performed within 30 h after the nerve lesion using single-fiber recordings that were performed proximal to the severed nerve end. 2. Among all unmyelinated fibers tested (n = 865), 4-8% exhibited persistent spontaneous activity of low and irregular frequency. The percentage of spontaneously active C fibers did not change significantly during the first 30 h. Only 6 of 796 A fibers had spontaneous activity. 3. Mechanical stimulation of the cut nerve end excited 5-8% of all C fibers under investigation. No development with time could be detected in the frequency of mechanically excitable C fibers. In contrast, beginning 6 h after nerve transection, the number of mechanically excitable A fibers rose with time, reaching 27% after 22-30 h. 4. Among the A fibers (C fibers) that exhibited mechanical excitability or spontaneous activity, only 4% (25%) had both properties, whereas 96% (75%) were either mechanosensitive or spontaneously active. 5. With time after the nerve lesion, the mean discharge rate of all spontaneously discharging C fibers decreased significantly from 49 imp/min (0.5-9 h after nerve lesion) to 11 imp/min after 22-30 h. The mean discharge rate of C fibers exhibiting solely spontaneous activity and those C fibers that were additionally mechanosensitive did not differ significantly.(ABSTRACT TRUNCATED AT 250 WORDS)

scholarly journals A Quantitative Retrospective Exposure Assessment for Former Chrysotile Asbestos Miners and Millers from Baie Verte, NL, Canada

2020 ◽  
Author(s):  
Tina Giles Murphy ◽  
Stephen Bornstein ◽  
John Oudyk ◽  
Paul A Demers
Keyword(s):  
Exposure Assessment ◽  
Asbestos Exposure ◽  
Epidemiologic Study ◽  
Geometric Standard Deviation ◽  
Chrysotile Asbestos ◽  
Adequate Quality ◽  
Compensation Claims ◽  
Job Title ◽  
Log Normal ◽  
Work Histories

Abstract Despite numerous studies of asbestos workers in the epidemiologic literature, there are very few cohort studies of chrysotile asbestos miners/millers that include high-quality retrospective exposure assessments. As part of the creation of the Baie Verte Miners’ Registry in 2008, a two-dimensional job exposure matrix (JEM) was developed for estimating asbestos exposures for former chrysotile asbestos miners/millers. Industrial hygiene data collected between 1963 and 1994 were analysed to assess validity for use in a retrospective exposure assessment and epidemiologic study. Registered former employees were divided into 52 exposure groups (EGs) based on job title and department and mean asbestos concentrations were calculated for each EG. The resulting exposure estimates were linked to individual registrants’ work histories allowing for the calculation of cumulative asbestos exposure for each registrant. The distribution of exposure for most EGs (82.6%) could be described as fitting a log-normal distribution, although variability within some EGs (55%) exceeded a geometric standard deviation (GSD) of 2.5. Overall, the data used to create EGs in the development of the JEM were deemed to be of adequate quality for estimating cumulative asbestos exposures for the former employees of the Baie Verte asbestos mine/mill. The variability between workers in the same job was often high and is an important factor to be considered when using estimates of cumulative asbestos exposure to adjudicate compensation claims. The exposures experienced in this cohort were comparable to those of other chrysotile asbestos miners/millers cohorts, specifically Italian and Québec cohorts.

Sensory Representation of Temperature in Mosquito Warm and Cold Cells

2005 ◽  
Vol 94 (1) ◽  
pp. 176-185 ◽  
Author(s):  
Ewald Gingl ◽  
Armin Hinterwirth ◽  
Harald Tichy
Keyword(s):  
Radiation Power ◽  
Discharge Rate ◽  
Radiant Heat ◽  
Cell Types ◽  
Sudden Increase ◽  
Change Analysis ◽  
Temperature Changes ◽  
Discharge Rates ◽  
Air Stream ◽  
Instantaneous Values

A pair of antagonistic thermoreceptive cells is associated with each of two peg-in-pit sensilla located on the antennal tip of Aedes aegypti. One, the warm cell, responds to rapid warming with a sudden increase in the rate of discharge. The other, a cold cell, responds to rapid cooling with a sudden increase in the discharge rate. When temperature changes are provided by oscillating changes in the convective heat contained in the stimulating air stream, the oscillating discharge rates of both cell types are in advance of the oscillations in temperature and slightly behind the oscillations in the rate of temperature change. Analysis of these phase relationships shows that both cell types respond not only to the actual temperature at particular instants in time (instantaneous temperature) but also to the rate with which temperature changes. Individual responses are therefore ambiguous and signal tendencies rather than precise instantaneous values. When the temperature oscillations are delivered by changes in radiation power, however, the oscillating discharge rates of the warm and cold cells are in step with the oscillations in temperature. Here, individual responses signal instantaneous values of temperature rather than tendencies. The power of radiant heat required to modulate the discharge rates is relatively high, suggesting that infrared radiation is not a significant cue in distant host location.

Spontaneous Pallidal Neuronal Activity in Human Dystonia: Comparison With Parkinson’s Disease and Normal Macaque

2005 ◽  
Vol 93 (6) ◽  
pp. 3165-3176 ◽  
Author(s):  
Philip A. Starr ◽  
Geoff M. Rau ◽  
Valerie Davis ◽  
William J. Marks ◽  
Jill L. Ostrem ◽  
...  
Keyword(s):  
Parkinson’S Disease ◽  
Parkinson's Disease ◽  
Spontaneous Activity ◽  
Discharge Rate ◽  
Oscillatory Activity ◽  
High Background ◽  
Repetitive Movements ◽  
Discharge Patterns ◽  
Lower Discharge ◽  
Bursting Activity

Dystonia is a movement disorder defined by sustained muscle contractions, causing twisting and repetitive movements and abnormal postures. To understand the abnormalities in pallidal discharge in dystonia, we have analyzed the spontaneous activity of 453 neurons sampled from the internal or external pallidum (GPi or GPe) of 22 patients with dystonia, 140 neurons from 11 patients with Parkinson’s disease (PD), and 157 neurons from two normal non-human primates (NHPs; Macacca mulatta). All recordings were performed without systemic sedation. Mean GPi discharge rate in dystonia was 55.3 ± 1.3 (SE) Hz. This was significantly lower than in the normal NHPs (82.5 ±2.5 Hz) and lower than in PD patients (95.2 ± 2.3 Hz). Mean GPe discharge rate in dystonia (54.0 ± 1.9 Hz) was lower than in the normal NHPs (69.7 ± 3.3 Hz) and was indistinguishable from that in PD patients (56.6 ± 3.5 Hz). Mean GPi discharge rate was inversely correlated with dystonia severity. GPi showed increased oscillatory activity in the 2- to 10-Hz range and increased bursting activity in both dystonia and PD as compared with the normal NHPs. Because the abnormalities in discharge patterns were similar in dystonia compared with PD, we suggest that bursting and oscillatory activity superimposed on a high background discharge rate are associated with parkinsonism, whereas similar bursting and oscillations superimposed on a lower discharge rate are associated with dystonia. Our findings are most consistent with a model of dystonia pathophysiology in which the two striatal cell populations contributing to the direct and indirect intrinsic pathways of the basal ganglia both have increased spontaneous activity.

scholarly journals Spontaneous Activity in Isolated Somata of Aplysia Pacemaker Neurons

1968 ◽  
Vol 51 (1) ◽  
pp. 29-45 ◽  
Author(s):  
Barbara O. Alving
Keyword(s):  
Spontaneous Activity ◽  
Time Course ◽  
Discharge Rate ◽  
Current Injection ◽  
Spontaneous Discharge ◽  
Pacemaker Neurons ◽  
Pacemaker Neuron ◽  
Transient Change ◽  
Transmembrane Potentials ◽  
Trigger Zone

Somata of pacemaker and nonpacemaker neurons were isolated by ligatures tied around the axons between the somata and the synaptic regions, and the transmembrane potentials of the isolated somata were recorded. Isolated somata of pacemaker neurons had a spontaneous discharge while isolated somata of nonpacemaker neurons were quiescent. In addition, the time course of accommodation in isolated somata of pacemaker and nonpacemaker neurons was found to be different. In pacemaker neurons, injection of current produced a change in rate of discharge sustained for the duration of current injection, while in nonpacemakers, current injection produced only a transient change in discharge rate. Evidence is presented that the pacemaker locus and spike trigger zone in the intact pacemaker neuron are located on the soma.

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