Suppression of Optokinetic Velocity Storage in Humans by Static Tilt in Roll

1991 ◽  
Vol 1 (4) ◽  
pp. 347-355 ◽  
Author(s):  
S.H. Lafortune ◽  
D.J. Ireland ◽  
R.M. Jell
Keyword(s):  
Exponential Model ◽  
Velocity Storage ◽  
Slow Phase ◽  
Indirect Pathway ◽  
Otolith Organ ◽  
Storage Mechanism ◽  
3 Dimensional ◽  
Double Exponential ◽  
Double Exponential Model ◽  
Anterior Posterior

The effects of static tilts about the roll (anterior-posterior) axis on human horizontal optokinetic afternystagmus (HOKAN) were examined. Static tilts in roll, with subjects lying on their left side, produced significant tilt-dependent HOKAN suppression. Only the slow (indirect pathway) component time constant (1/D) of the double exponential model for human HOKAN decreased with angle of roll tilt. The effect was direction specific in that suppression occurred only following a leftward-going stimulus. These findings provide further support for the postulate that otolith-organ-mediated activity can couple to the horizontal velocity storage mechanism in humans. A slight trend towards a tilt-dependent reduction of coefficient A (initial slow phase velocity of fast component decay) was revealed, suggesting the possibility that otolith-organ-mediated activity could couple to direct (pursuit-mediated?) pathways as well. No horizontal-to-vertical cross-coupling occurred, indicating that this aspect of the 3-dimensional model for velocity storage proposed by Raphan & Cohen (1988) may not completely apply to humans.

The Velocity Storage Mechanism of the Optokinetic Nystagmus Under Apparent Stimulus Movements in Squirrel Monkeys

1997 ◽  
Vol 7 (6) ◽  
pp. 441-451
Author(s):  
J. Kröller ◽  
F. Behrens ◽  
V.V. Marlinsky
Keyword(s):  
Steady State ◽  
Brain Stem ◽  
Apparent Movement ◽  
Squirrel Monkeys ◽  
Constant Light ◽  
Velocity Storage ◽  
Slow Phase ◽  
Stripe Pattern ◽  
Storage Mechanism ◽  
The Brain

Experiments in two awake untrained squirrel monkeys were performed to study the velocity storage mechanism during fast rise of OKN slow phase velocity. This was done by testing the monkey’s capability to perform OKN in response to a stationary-appearing stroboscopically illuminated stripe pattern of a horizontally rotating drum. Nystagmus was initially elicited during constant illumination lasting between 0.6 and 25 s. The periodicity of the stripe pattern was 2.37°. When after the constant light the flash illumination was switched on again, two types of behavior could occur, depending on the length of the constant light interval (CLI): 1) when the CLI was shorter than a threshold value of 6.2 seconds, the OKN ceased under the flash stimulation. Then a “post-OKN” occurred that increased with the length of the CLIs, indicating that the intermittently illuminated pattern did not provoke fixation suppression of OKN aftereffects. 2) when the CLI was above threshold, the OKN continued under the flash light: it will he called “apparent movement OKN.” The threshold CLI between the type 1 and the type 2 response did not depend on drum velocities between 21.5°/s and 71.3°/s. The average gain of the apparent movement OKN was 0.83 ± 0.04; gain and stability of slow phase eye movement velocity did not deviate systematically from the usually elicited OKN. OKAN after apparent movement OKN did not deviate from OKAN after constantly illuminated moving patterns. In response to the OKN initiation by a constantly illuminated pattern up to pattern velocities of 100°/s, the OKN steady state gain was reached within the first 2 or 3 nystagmus beats. We ascribe the increase of the post-OKN with CLI and the existence of a threshold constant light interval to activity-accumulation in the common velocity-to-position integrator (velocity storage) of the brain stem. Loading of the velocity storage takes place after the OKN gain has already reached the steady-state value. Apparent movement OKN could also be elicited in guinea pigs that lack an effective smooth pursuit system. We suggest that apparent movement OKN is produced by mechanisms located in the brain stem.

Spatial orientation of postrotatory nystagmus during static roll tilt in cats

2002 ◽  
Vol 12 (1) ◽  
pp. 15-23
Author(s):  
Keiko Yasuda ◽  
Hiroaki Fushiki ◽  
Rinnosuke Wada ◽  
Yukio Watanabe
Keyword(s):  
Spatial Orientation ◽  
Vertical Axis ◽  
Longitudinal Axis ◽  
Velocity Storage ◽  
Slow Phase ◽  
Storage Mechanism ◽  
Spatial Disorientation ◽  
Acceleration And Deceleration ◽  
Eye Velocity ◽  
Roll Tilt

While the stimulation of otolith inputs reduces the duration of postrotatory nystagmus (PRN), there is still room for dialogue about the effect of static tilt on the orientation of PRN. We studied one possible influence of static roll tilt on the spatial orientation of PRN in cats. The animal was rotated about an earth-vertical axis (EVA) at a constant velocity of 100 deg/s with an acceleration and deceleration of 120 deg / s 2 . Within two seconds after stopping EVA rotation, the animal was passively tilted at 45 deg/s about its longitudinal axis by as much as ± 90 deg in steps of 15 deg. Eye movements were measured with magnetic search coils. The angle of the PRN plane and its slow phase eye velocity were measured. The time constant of PRN decreased with an increase in roll tilt. The PRN plane remained earth horizontal within a range of ± 30 deg roll tilt. Beyond this range, the velocity of PRN decreased too rapidly to measure any change in orientation. Our results indicate a spatially limited and temporally short interaction of the semicircular canal and otolith signals in the velocity storage mechanism of cat PRN. Our data, along with previous studies, suggest that different species show different solutions to the problem of the imbalance and spatial disorientation during contradictory stimuli.

Role of irregular otolith afferents in the steady-state nystagmus during off-vertical axis rotation

1992 ◽  
Vol 68 (5) ◽  
pp. 1895-1900 ◽  
Author(s):  
D. E. Angelaki ◽  
A. A. Perachio ◽  
M. J. Mustari ◽  
C. L. Strunk
Keyword(s):  
Steady State ◽  
Vertical Axis ◽  
Dynamic Responses ◽  
Velocity Storage ◽  
Slow Phase ◽  
Otolith Organs ◽  
Galvanic Stimulation ◽  
Storage Mechanism ◽  
Velocity Storage Mechanism ◽  
Ocular Nystagmus

1. During constant velocity off-vertical axis rotations (OVAR) in the dark a compensatory ocular nystagmus is present throughout rotation despite the lack of a maintained signal from the semicircular canals. Lesion experiments and canal plugging have attributed the steady-state ocular nystagmus during OVAR to inputs from the otolith organs and have demonstrated that it depends on an intact velocity storage mechanism. 2. To test whether irregularly discharging otolith afferents play a crucial role in the generation of the steady-state eye nystagmus during OVAR, we have used anodal (inhibitory) currents bilaterally to selectively and reversibly block irregular vestibular afferent discharge. During delivery of DC anodal currents (100 microA) bilaterally to both ears, the slow phase eye velocity of the steady-state nystagmus during OVAR was reduced or completely abolished. The disruption of the steady-state nystagmus was transient and lasted only during the period of galvanic stimulation. 3. To distinguish a possible effect of ablation of the background discharge rates of irregular vestibular afferents on the velocity storage mechanism from specific contributions of the dynamic responses from irregular otolith afferents to the circuit responsible for the generation of the steady-state nystagmus, bilateral DC anodal galvanic stimulation was applied during optokinetic nystagmus (OKN) and optokinetic afternystagmus (OKAN). No change in OKN and OKAN was observed.(ABSTRACT TRUNCATED AT 250 WORDS)

A DOUBLE EXPONENTIAL MODEL FOR TRANSMITTANCE IN SOLAR PONDS

1989 ◽  
Vol 7 (4) ◽  
pp. 227-235 ◽  
Author(s):  
M. N. A. HAWLADER ◽  
J. C. HO ◽  
N. E. WIJEYSUNDERA ◽  
T. H. KHO
Keyword(s):  
Exponential Model ◽  
Solar Ponds ◽  
Double Exponential ◽  
Double Exponential Model

scholarly journals BOD measuring and modelling methods - review

2011 ◽  
Vol 43 (2) ◽  
pp. 143-153
Author(s):  
Tadeusz Siwiec ◽  
Lidia Kiedryńska ◽  
Klaudia Abramowicz ◽  
Aleksandra Rewicka ◽  
Piotr Nowak
Keyword(s):  
Exponential Model ◽  
Second Order ◽  
First Order ◽  
Double Exponential ◽  
Double Exponential Model ◽  
Modelling Methods

BOD measuring and modelling methods - reviewThe article presents the method of measuring BOD in wastewater and characteristic different models which can by used for describing changes of BOD in next days. In the paper described eight models: Moore et al. (1950), Thomas (1950), Navone (1960), Fujimoto (1964), Hewitt et al. (1979), Adrian and Sanders (1992-1993) as well as Young and Clark (1965) used by Adrian and Sanders (1998), Borsuk and Stow (2000) and Manson et al. (2006). Comparison the models suggests that changing of BOD during the time are better describes by models second order or double exponential model (Manson et al. 2006) than models the first order.

Decomposition of aspen (Populustremuloides) leaf litter modified by leaching

1990 ◽  
Vol 20 (7) ◽  
pp. 943-951 ◽  
Author(s):  
William F. J. Parsons ◽  
Barry R. Taylor ◽  
Dennis Parkinson
Keyword(s):  
Mass Loss ◽  
Leaf Litter ◽  
Rocky Mountain ◽  
Exponential Model ◽  
Decay Rates ◽  
Double Exponential ◽  
Exponential Trend ◽  
Aspen Forest ◽  
Double Exponential Model ◽  
Soluble Material

In a Rocky Mountain aspen forest, the detailed pattern of mass loss from decomposing leaf litter of trembling aspen (Populustremuloides Michx.) during the first 6 months of decay was compared with that from aspen leaves modified to produce a more recalcitrant litter type by removal of leachable material (31.7% of original mass). Leaching litter removed substantial quantities of N (24%) and P (54%), but did not change the litter's C/N ratio (77:1); and leached leaves still contained 33% labile (benzene alcohol soluble) material. Decomposition of intact aspen litter was best described by a double exponential model (k1 = −7.91/year, k2 = −0.21/year), except during the first 2 weeks, when an extremely rapid mass loss (14.2%) apparently resulted from leaching. Microbial metabolism was probably responsible for most of the subsequent decay (35% total in 6 months). In contrast, decomposition of leached aspen showed no exponential trend and was best described by a simple linear regression with a slope of −19.7%/year. Additional data from a 2nd year (12–15 months decay) reduced the regression estimates of decay rates but did not alter the best fit models. Fits were improved slightly if temperature sum replaced time in the regressions, especially if 2nd-year data were included.

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