Cerebellar Nodulectomy Impairs Spatial Memory of Vestibular and Optokinetic Stimulation in Rabbits

2002 ◽  
Vol 87 (2) ◽  
pp. 962-975 ◽  
Author(s):  
N. H. Barmack ◽  
P. Errico ◽  
A. Ferraresi ◽  
H. Fushiki ◽  
V. E. Pettorossi ◽  
...  
Keyword(s):  
Pitch Angle ◽  
Time Course ◽  
Vestibular Stimulation ◽  
Slow Phase ◽  
Optokinetic Stimulation ◽  
Movement Velocity ◽  
Vertical Drift ◽  
Before And After ◽  
Sinusoidal Optokinetic Stimulation

Natural vestibular and optokinetic stimulation were used to investigate the possible role of the cerebellar nodulus in the regulation and modification of reflexive eye movements in rabbits. The nodulus and folium 9d of the uvula were destroyed by surgical aspiration. Before and after nodulectomy the vertical and horizontal vestibuloocular reflexes (VVOR, HVOR) were measured during sinusoidal vestibular stimulation about the longitudinal (roll) and vertical (yaw) axes. Although the gain of the HVOR (GHVOR = peak eye movement velocity/peak head velocity) was not affected by the nodulectomy, the gain of the VVOR (GVVOR) was reduced. The gains of the vertical and horizontal optokinetic reflexes (GVOKR, GHOKR) were measured during monocular, sinusoidal optokinetic stimulation (OKS) about the longitudinal and vertical axes. Following nodulectomy, there was no reduction in GVOKR or GHOKR. Long-term binocular OKS was used to generate optokinetic afternystagmus, OKAN II, that lasts for hours. After OKAN II was induced, rabbits were subjected to static pitch and roll, to determine how the plane and velocity of OKAN II is influenced by a changing vestibular environment. During static pitch, OKAN II slow phase remained aligned with earth-horizontal. This was true for normal and nodulectomized rabbits. During static roll, OKAN II remained aligned with earth-horizontal in normal rabbits. During static roll in nodulectomized rabbits, OKAN II slow phase developed a centripetal vertical drift. We examined the suppression and recovery of GVVOR following exposure to conflicting vertical OKS for 10–30 min. This vestibular-optokinetic conflict reduced GVVOR in both normal and nodulectomized rabbits. The time course of recovery of GVVOR after conflicting OKS was the same before and after nodulectomy. In normal rabbits, the head pitch angle, at which peak OKAN II velocity occurred, corresponded to the head pitch angle maintained during long-term OKS. If the head was maintained in a “pitched-up” or “pitched-down” orientation during long-term OKS, the subsequently measured OKAN II peak velocity occurred at the same orientation. This was not true for nodulectomized rabbits, who had OKAN II peak velocities at head pitch angles independent of those maintained during long-term OKS. We conclude that the nodulus participates in the regulation of compensatory reflexive movements. The nodulus also influences “remembered” head position in space derived from previous optokinetic and vestibular stimulation.

Long-term facilitation alters transmitter releasing properties at the crayfish neuromuscular junction

1986 ◽  
Vol 55 (3) ◽  
pp. 484-498 ◽  
Author(s):  
J. M. Wojtowicz ◽  
H. L. Atwood
Keyword(s):  
Neuromuscular Junction ◽  
Synaptic Transmission ◽  
Time Course ◽  
Muscle Fibers ◽  
Low Frequencies ◽  
Before And After ◽  
Binomial Parameter ◽  
Small Muscle ◽  
Long Term Facilitation

Synaptic transmission at the neuromuscular junction of the excitatory axon supplying the crayfish opener muscle was examined before and after induction of long-term facilitation (LTF) by a 10-min period of stimulation at 20 Hz. Induction of LTF led to a period of enhanced synaptic transmission, which often persisted for many hours. The enhancement was entirely presynaptic in origin, since quantal unit size and time course were not altered, and quantal content of transmission (m) was increased. LTF was not associated with any persistent changes in action potential or presynaptic membrane potential recorded in the terminal region of the excitatory axon. The small muscle fibers of the walking-leg opener muscle were almost isopotential, and all quantal events could be recorded with an intracellular microelectrode. In addition, at low frequencies of stimulation, m was small. Thus it was possible to apply a binomial model of transmitter release to events recorded from individual muscle fibers and to calculate values for n (number of responding units involved in transmission) and p (probability of transmission for the population of responding units) before and after LTF. In the majority of preparations analyzed (6/10), amplitude histograms of evoked synaptic potentials could be described by a binomial distribution with a small n and moderately high p. LTF produced a significant increase in n, while p was slightly reduced. The results can be explained by a model in which the binomial parameter n represents the number of active synapses and parameter p the mean probability of release at a synapse. Provided that a pool of initially inactive synapses exists, one can postulate that LTF involves recruitment of synapses to the active state.

Role of the cervico-ocular reflex in the “flying” pigeon: Interactions with the optokinetic reflex

2004 ◽  
Vol 21 (2) ◽  
pp. 167-180 ◽  
Author(s):  
M. MAURICE ◽  
H. GIOANNI
Keyword(s):  
Time Course ◽  
Reverse Direction ◽  
Slow Phase ◽  
Phase Lag ◽  
Optokinetic Stimulation ◽  
Optokinetic Response ◽  
Velocity Amplitude ◽  
Ocular Reflex ◽  
Optokinetic Reflex ◽  
Cervical Stimulation

We studied the cervico-ocular reflex (COR) alone and in combination with the optokinetic (OKN) reflex in head-fixed pigeons. We analyzed these responses in two behavioral conditions: (1) animals were hung in a harness (“resting” condition); and (2) animals were additionally submitted to a frontal airflow that provoked a flight posture (“flying” condition). In both conditions, cervical stimulation provoked a slow phase of very low gain (around 0.05) in the opposite direction to that of the stimulation and fast phases triggered near the head–body alignment in the same direction as the stimulation. The slow phase showed a phase lag of 20 deg at 0.5 Hz. The gain of the slow phase was not modified by the velocity, amplitude, or frequency of the stimuli. This gain was not changed by the presence of a fixed visual surround.When cervical stimuli (0.05–0.5 Hz) were added to an optokinetic stimulation (30 deg/s) in the “resting” condition, the slow phase velocity (SPV) of the optokinetic reflex was modulated with a time course close to that produced by the cervico-ocular reflex alone. The SPV was alternately increased and decreased round the SPV level corresponding to the steady-state OKN. In the “flying” condition, optokinetic-cervical stimulation provoked an eye beating field and a strong SPV modulation synchronized with the position of the cervical stimulation. The number of nystagmic beats (OKN) and the amplitude and velocity of the fast phases were modulated in correlation with the SPV. Consequently, the optokinetic response was increased or decreased according to whether the cervical stimuli were in the reverse direction or in the same direction as the optokinetic stimulation, respectively.These data are interpreted as an improvement of gaze stabilization by the COR. This mechanism is context dependent, since it is strongly reinforced during the flight.

Spatial orientation of the vestibular system: dependence of optokinetic after-nystagmus on gravity

1991 ◽  
Vol 66 (4) ◽  
pp. 1422-1439 ◽  
Author(s):  
M. J. Dai ◽  
T. Raphan ◽  
B. Cohen
Keyword(s):  
Time Course ◽  
The Body ◽  
Body Axis ◽  
Coronal Plane ◽  
Velocity Storage ◽  
Slow Phase ◽  
Optokinetic Stimulation ◽  
Stimulus Motion ◽  
Marquardt Algorithm ◽  
The Mean

1. Monkeys received optokinetic stimulation at 60 degrees/s about their yaw (animal vertical) and pitch (animal horizontal) axes, as well as about other head-centered axes in the coronal plane. The animals were upright or tilted in right-side-down positions with regard to gravity. The stimuli induced horizontal, vertical, and oblique optokinetic nystagmus (OKN). OKN was followed by optokinetic after-nystagmus (OKAN), which was recorded in darkness. 2. When monkeys were tilted, stimulation that generated horizontal or yaw axis eye velocity during OKN induced a vertical or pitch component of slow phase velocity during OKAN. This has been designated as "cross-coupling" of OKAN. Eigenvalues and eigenvectors associated with the system generating OKAN were found as a function of tilt. They were determined by use of the Levenberg-Marquardt algorithm to minimize the mean square error between the output of a model of OKAN and the data. 3. The eigenvector associated with yaw OKAN (yaw axis eigenvector) was maintained close to the spatial vertical regardless of the angle of tilt. The eigenvector associated with pitch OKAN (pitch axis eigenvector) was always aligned with the body axis. The data indicate that velocity storage can be modeled by a piecewise linear system, the structure of which is dependent on gravity and the yaw axis eigenvector, which tends to align with gravity. 4. Yaw axis eigenvectors were also determined by giving optokinetic stimulation about head-centered axes in the coronal plane with the animal in various angles of tilt. A technique using a spectral analysis of residuals was developed to estimate whether yaw and pitch OKAN slow phase velocities decayed concurrently at the same relative rate and over the same time course. The eigenvectors determined by this method were in agreement with those obtained by analyzing OKAN elicited by yaw OKN. 5. During yaw OKN with the animal in tilted positions, the mean vector of the ensuing nystagmus was closer to the body axis than to the spatial vertical. This suggests that there is suppression of the cross-coupled pitch component during OKN. The direction of the stimulus may be utilized to suppress components of velocity storage not coincident with the direction of stimulus motion. 6. There were similarities between the monkey eigenvectors and human perception of the spatial vertical, and the mean of eigenvectors for upward and downward eye velocities overlay human 1-g perceptual data.(ABSTRACT TRUNCATED AT 400 WORDS)

scholarly journals Mechanisms of maintenance of tropical freshwater fish communities in the face of disturbance

1999 ◽  
Vol 354 (1391) ◽  
pp. 1803-1810 ◽  
Author(s):  
Keith M. Martin–Smith ◽  
Lindsay M. Laird ◽  
Luke Bullough ◽  
Matthew G. Lewis
Keyword(s):  
Time Course ◽  
Fish Communities ◽  
Complete Removal ◽  
Physical Habitat ◽  
Fish Community Structure ◽  
Community Resistance ◽  
Significant Difference ◽  
Before And After ◽  
The Face

Community resistance to, and resilience from, perturbation will determine the trajectory of recovery from disturbance. Although selective timber extraction is considered a severe disturbance, fish communities from headwater streams around Danum Valley Field Centre, Sabah, Malaysia, showed few long–term changes in species composition or abundance. However, some species showed short–term (< 18 months) absence or decrease in abundance. These observations suggested that both resistance and resilience were important in maintaining long–term fish community structure. Resistance to perturbation was tested by monitoring fish communities before and after the creation of log–debris dams, while resilience was investigated by following the time–course of recolonization following complete removal of all fish. High community resistance was generally shown although the response was site–specific, dependent on the composition of the starting community, the size of the stream and physical habitat changes. High resilience was demonstrated in all recolonization experiments with strong correlations between pre– and post–defaunation communities, although there was a significant difference between pool and riffle habitats in the time–course of recovery. These differences can be explained by the movement characteristics of the species found in the different habitats. Resilience appeared to be a more predictable characteristic of the community than resistance and the implications of this for ensuring the long–term persistence of fish in the area are discussed.

scholarly journals Transcriptional Changes Before and After Forgetting of a Long-Term Sensitization Memory in Aplysia californica

2018 ◽  
Author(s):  
Robert Calin-Jageman ◽  
Irina Calin-Jageman
Keyword(s):  
Gene Expression ◽  
Time Course ◽  
Memory Trace ◽  
Aplysia Californica ◽  
Regulation Of Expression ◽  
Withdrawal Reflex ◽  
Before And After ◽  
Transcriptional Changes ◽  
Testable Model

This is a pre-print of a paper now published in Neurobiology of Learning and Memory: https://doi.org/10.1016/j.nlm.2018.09.007 Most long-term memories are forgotten, becoming progressively less likely to be recalled. Still, some memory fragments may persist beyond forgetting, as savings memory (easier relearning) can persist long after recall has become impossible. What happens to a memory trace during forgetting that makes it inaccessible for recall and yet still effective to spark easier re-learning? We are addressing this question by tracking the transcriptional changes that accompany learning and then forgetting of a long-term sensitization memory in the tail-elicited siphon withdrawal reflex of Aplysia californica. First, we tracked savings memory. We found that even though recall of sensitization fades completely within 1 week of training, savings memory is still robustly expressed at 2 weeks post training. Next, we tracked the time-course of regulation of 11 transcripts we previously identified as potentially being regulated beyond the decay of recall. Remarkably, 3 transcripts still show strong regulation of expression 2 weeks after training and an additional 4 are regulated for at least 1 week. These long-lasting changes in gene expression always began early in the memory process, within 1 day of training. We present a synthesis of our results tracking gene expression changes accompanying sensitization and provide a testable model of how sensitization memory is forgotten.

scholarly journals A Method for Studying the Effects of Neurochemicals on Long-Term Compensation in Unilaterally Labyrinthectomized Rats

1997 ◽  
Vol 6 (2) ◽  
pp. 105-113 ◽  
Author(s):  
Lars Andersson ◽  
Mats Ulfendahl ◽  
Richard Tham
Keyword(s):  
Experimental Model ◽  
Virtual Instrument ◽  
Vestibular Stimulation ◽  
Slow Phase ◽  
Intact Side ◽  
Ocular Reflex ◽  
Vestibulo Ocular Reflex ◽  
Repeated Analysis ◽  
Adaptation Processes

A new method has been developed to study the influence of drugs and toxicants on longterm recovery of dynamics in the horizontal vestibulo-ocular reflex of the rat after hemilabyrinthectomy (HL). HL was performed by injecting sodium arsanilate into the middle ear. The lesion was confirmed by histology. Eye movements elicited by sinusoidal vestibular stimulation, in both light and darkness, were recorded by a search-coil technique and then analyzed by a computer program created with virtual instrument soft-ware, which calculated the gain of the slow-phase velocity (SPV) and the saccades para-meters (frequency, amplitude, and peak velocity) to the lesioned side and to the intact side separately. During the 2-10 week period after HL, repeated analysis of the spontaneous long-term recovery of such parameters revealed a slight but significant reduction of the post-HL asymmetry between SPV gain to the lesioned side and to the intact side. During the follow-up period, a post-HL increase of the phase lead remained unchanged. The reduced number of saccades/min was not completely restored. To test the usefulness of the experimental model for neurochemical investigation of such adaptation, we administered baclofen and toluene to rats 8–12 wk after hemilabyrinthectomy. Baclofen, a specificGABABagonist, immediately restored the symmetry of SPV gain. By contrast, toluene, which has some effects on the central vestibular system that are related toGABABtransmission, aggravated the asymmetry in both the SPV gain and the number of saccades. We suggest that the experimental model would be useful for studying neurochemical mechanisms in vestibular adaptation processes.

scholarly journals Text Mining Approaches to Analyze Public Sentiment Changes Regarding COVID-19 Vaccines on Social Media in Korea

2021 ◽  
Vol 18 (12) ◽  
pp. 6549
Author(s):  
Jae-Geum Shim ◽  
Kyoung-Ho Ryu ◽  
Sung Hyun Lee ◽  
Eun-Ah Cho ◽  
Yoon Ju Lee ◽  
...  
Keyword(s):  
Social Media ◽  
Sentiment Analysis ◽  
Time Course ◽  
Latent Dirichlet Allocation ◽  
Allocation Model ◽  
Public Response ◽  
Latent Dirichlet Allocation Model ◽  
Public Sentiment ◽  
Before And After

The COVID-19 pandemic has affected the entire world, resulting in a tremendous change to people’s lifestyles. We investigated the Korean public response to COVID-19 vaccines on social media from 23 February 2021 to 22 March 2021. We collected tweets related to COVID-19 vaccines using the Korean words for “coronavirus” and “vaccines” as keywords. A topic analysis was performed to interpret and classify the tweets, and a sentiment analysis was conducted to analyze public emotions displayed within the retrieved tweets. Out of a total of 13,414 tweets, 3509 were analyzed after preprocessing. Eight topics were extracted using the Latent Dirichlet Allocation model, and the most frequently tweeted topic was vaccine hesitation, consisting of fear, flu, safety of vaccination, time course, and degree of symptoms. The sentiment analysis revealed a similar ratio of positive and negative tweets immediately before and after the commencement of vaccinations, but negative tweets were prominent after the increase in the number of confirmed COVID-19 cases. The public’s anticipation, disappointment, and fear regarding vaccinations are considered to be reflected in the tweets. However, long-term trend analysis will be needed in the future.

Time course of appearance of markers of arrhythmia in patients with tetralogy of Fallot before and after surgery

2004 ◽  
Vol 14 (4) ◽  
pp. 360-366 ◽  
Author(s):  
Rim Al Balkhi ◽  
Maurice Beghetti ◽  
Beat Friedli
Keyword(s):  
Tetralogy Of Fallot ◽  
Time Course ◽  
Late Potentials ◽  
Ventricular Late Potentials ◽  
Post Operative Period ◽  
Before And After ◽  
Long Term Follow Up ◽  
History Of ◽  
Electrocardiographic Parameters

Sudden death and ventricular tachycardia are known to occur late after correction of tetralogy of Fallot. Abnormal dispersion of the QT interval, ventricular late potentials, and prolongation of the QRS complex, alone or in combination, are useful markers of the risk for such complications. Our present prospective study investigates the time course of appearance of two markers, dispersion of QT and JT, and ventricular late potentials, before and after corrective surgery. Dispersion of QT and JT, and signal averaged electrocardiographic parameters, were determined sequentially in 20 patients before, a mean of 9 ± 3 days after, and again 35 ± 11 days post-operatively. Dispersion of QT was already abnormal before surgery in two-fifths of the patients, but increased markedly in the later post-operative period. Ventricular late potentials were absent before surgery and in the immediate post-operative period, but were found in one-fifth of patients 1 month later. We conclude that abnormal dispersion of QT is, to some extent, a fact of the natural history of tetralogy of Fallot, but is significantly amplified by surgery. Ventricular late potentials, on the other hand, are absent before surgery, but appear with some delay after the operation, probably as a result of scarring rather than the surgical incision itself. Long-term follow-up is needed to assess the significance of these findings.

Preliminary Evaluation of a Weibull Function for Fitting Slow-Component Eye Velocity over the Time Course of Caloric-Induced Nystagmus

1989 ◽  
Vol 32 (3) ◽  
pp. 681-687 ◽  
Author(s):  
C. Formby ◽  
B. Albritton ◽  
I. M. Rivera
Keyword(s):  
Time Course ◽  
Slow Component ◽  
Weibull Function ◽  
Preliminary Evaluation ◽  
Mathematical Function ◽  
Before And After ◽  
Best Fitting ◽  
Eye Velocity ◽  
Fitting Parameters ◽  
Weibull Equation

We describe preliminary attempts to fit a mathematical function to the slow-component eye velocity (SCV) over the time course of caloric-induced nystagmus. Initially, we consider a Weibull equation with three parameters. These parameters are estimated by a least-squares procedure to fit digitized SCV data. We present examples of SCV data and fitted curves to show how adjustments in the parameters of the model affect the fitted curve. The best fitting parameters are presented for curves fit to 120 warm caloric responses. The fitting parameters and the efficacy of the fitted curves are compared before and after the SCV data were smoothed to reduce response variability. We also consider a more flexible four-parameter Weibull equation that, for 98% of the smoothed caloric responses, yields fits that describe the data more precisely than a line through the mean. Finally, we consider advantages and problems in fitting the Weibull function to caloric data.

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