Mislocalization of stationary and flashed bars after saccadic inward and outward adaptation of reactive saccades

2012 ◽  
Vol 107 (11) ◽  
pp. 3062-3070 ◽  
Author(s):  
Fabian Schnier ◽  
Markus Lappe
Keyword(s):  
Saccade Target ◽  
Saccade Amplitude ◽  
Presentation Duration ◽  
Target Presentation ◽  
Adaptation Mechanisms ◽  
Long Duration ◽  
Neuronal Mechanisms ◽  
The Difference ◽  
Saccade Adaptation

Recent studies have shown that saccadic inward adaptation (i.e., the shortening of saccade amplitude) and saccadic outward adaptation (i.e., the lengthening of saccade amplitude) rely on partially different neuronal mechanisms. There is increasing evidence that these differences are based on differences at the target registration or planning stages since outward but not inward adaptation transfers to hand-pointing and perceptual localization of flashed targets. Furthermore, the transfer of reactive saccade adaptation to long-duration overlap and scanning saccades is stronger after saccadic outward adaptation than that after saccadic inward adaptation, suggesting that modulated target registration stages during outward adaptation are increasingly used in the execution of saccades when the saccade target is visually available for a longer time. The difference in target presentation duration between reactive and scanning saccades is also linked to a difference in perceptual localization of different targets. Flashed targets are mislocalized after inward adaptation of reactive and scanning saccades but targets that are presented for a longer time (stationary targets) are mislocalized stronger after scanning than after reactive saccades. This link between perceptual localization and adaptation specificity suggests that mislocalization of stationary bars should be higher after outward than that after inward adaptation of reactive saccades. In the present study we test this prediction. We show that the relative amount of mislocalization of stationary versus flashed bars is higher after outward than that after inward adaptation of reactive saccades. Furthermore, during fixation stationary and flashed bars were mislocalized after outward but not after inward adaptation. Thus, our results give further evidence for different adaptation mechanisms between inward and outward adaptation and harmonize some recent research.

scholarly journals Discharge of Monkey Nucleus Reticularis Tegmenti Pontis Neurons Changes During Saccade Adaptation

2005 ◽  
Vol 94 (3) ◽  
pp. 1938-1951 ◽  
Author(s):  
N. Takeichi ◽  
C.R.S. Kaneko ◽  
A. F. Fuchs
Keyword(s):  
Saccade Amplitude ◽  
Nucleus Reticularis Tegmenti Pontis ◽  
Adaptation Mechanisms ◽  
Nucleus Reticularis ◽  
Oculomotor Vermis ◽  
Adaptive Mechanisms ◽  
Direct Input ◽  
Induced Changes ◽  
Saccade Adaptation ◽  
Amplitude Decrease

Saccade accuracy is maintained by adaptive mechanisms that continually modify saccade amplitude to reduce dysmetria. Previous studies suggest that adaptation occurs upstream of the caudal fastigial nucleus (CFN), the output of the oculomotor cerebellar vermis but downstream from the superior colliculus (SC). The nucleus reticularis tegmenti pontis (NRTP) is a major source of afferents to both the oculomotor vermis and the CFN and in turn receives direct input from the SC. Here we examine the activity of NRTP neurons in four rhesus monkeys during behaviorally induced changes in saccade amplitude to assess whether their discharge might reveal adaptation mechanisms that mediate changes in saccade amplitude. During amplitude decrease adaptation (average, 22%), the gradual reduction of saccade amplitude was accompanied by an increase in the number of spikes in the burst of 19/34 neurons (56%) and no change for 15 neurons (44%). For the neurons that increased their discharge, the additional spikes were added at the beginning of the saccadic burst and adaptation also delayed the peak-firing rate in some neurons. Moreover, after amplitude reduction, the movement fields changed shape in all 15 open field neurons tested. Our data show that saccadic amplitude reduction affects the number of spikes in the burst of more than half of NRTP neurons tested, primarily by increasing burst duration not frequency. Therefore adaptive changes in saccade amplitude are reflected already at a major input to the oculomotor cerebellum.

scholarly journals The reference frames in saccade adaptation

2013 ◽  
Vol 109 (7) ◽  
pp. 1815-1823 ◽  
Author(s):  
Eckart Zimmermann
Keyword(s):  
Reference Frames ◽  
Visual Target ◽  
Saccade Target ◽  
Presentation Duration ◽  
Coordinate Frames ◽  
Intended Target ◽  
Target Signal ◽  
External Space ◽  
Saccade Adaptation ◽  
Voluntary Saccades

Saccade adaptation is a mechanism that adjusts saccade landing positions if they systematically fail to reach their intended target. In the laboratory, saccades can be shortened or lengthened if the saccade target is displaced during execution of the saccade. In this study, saccades were performed from different positions to an adapted saccade target to dissociate adaptation to a spatiotopic position in external space from a combined retinotopic and spatiotopic coding. The presentation duration of the saccade target before saccade execution was systematically varied, during adaptation and during test trials, with a delayed saccade paradigm. Spatiotopic shifts in landing positions depended on a certain preview duration of the target before saccade execution. When saccades were performed immediately to a suddenly appearing target, no spatiotopic adaptation was observed. These results suggest that a spatiotopic representation of the visual target signal builds up as a function of the duration the saccade target is visible before saccade execution. Different coordinate frames might also explain the separate adaptability of reactive and voluntary saccades. Spatiotopic effects were found only in outward adaptation but not in inward adaptation, which is consistent with the idea that outward adaptation takes place at the level of the visual target representation, whereas inward adaptation is achieved at a purely motor level.

Contraction duration affects metabolic energy cost and fatigue in skeletal muscle

1998 ◽  
Vol 274 (3) ◽  
pp. E397-E402 ◽  
Author(s):  
Michael C. Hogan ◽  
Erica Ingham ◽  
S. Sadi Kurdak
Keyword(s):  
Skeletal Muscle ◽  
Short Duration ◽  
Energy Cost ◽  
Lactate Concentration ◽  
Metabolic Energy ◽  
Muscle Lactate ◽  
Contracting Muscle ◽  
Contraction Duration ◽  
Long Duration ◽  
The Difference

It has been suggested that during a skeletal muscle contraction the metabolic energy cost at the onset may be greater than the energy cost related to holding steady-state force. The purpose of the present study was to investigate the effect of contraction duration on the metabolic energy cost and fatigue process in fully perfused contracting muscle in situ. Canine gastrocnemius muscle ( n = 6) was isolated, and two contractile periods (3 min of isometric, tetanic contractions with 45-min rest between) were conducted by each muscle in a balanced order design. The two contractile periods had stimulation patterns that resulted in a 1:3 contraction-to-rest ratio, with the difference in the two contractile periods being in the duration of each contraction: short duration 0.25-s stimulation/0.75-s rest vs. long duration 1-s stimulation/3-s rest. These stimulation patterns resulted in the same total time of stimulation, number of stimulation pulses, and total time in contraction for each 3-min period. Muscle O2 uptake, the fall in developed force (fatigue), the O2 cost of developed force, and the estimated total energy cost (ATP utilization) of developed force were significantly greater ( P < 0.05) with contractions of short duration. Lactate efflux from the working muscle and muscle lactate concentration were significantly greater with contractions of short duration, such that the calculated energy derived from glycolysis was three times greater in this condition. These results demonstrate that contraction duration can significantly affect both the aerobic and anaerobic metabolic energy cost and fatigue in contracting muscle. In addition, it is likely that the greater rate of fatigue with more rapid contractions was a result of elevated glycolytic production of lactic acid.

scholarly journals Saccade Adaptation Specific to Visual Context

2009 ◽  
Vol 101 (4) ◽  
pp. 1713-1721 ◽  
Author(s):  
James P. Herman ◽  
Mark R. Harwood ◽  
Josh Wallman
Keyword(s):  
Target Stimulus ◽  
Separate Experiment ◽  
Physical Parameters ◽  
Visual Context ◽  
Saccade Amplitude ◽  
Repair Mechanism ◽  
Adaptive Process ◽  
Differential Adaptation ◽  
Saccade Adaptation ◽  
Visual Properties

When saccades consistently overshoot their targets, saccade amplitudes gradually decrease, thereby maintaining accuracy. This adaptive process has been seen as a form of motor learning that copes with changes in physical parameters of the eye and its muscles, brought about by aging or pathology. One would not expect such a motor-repair mechanism to be specific to the visual properties of the target stimulus. We had subjects make saccades to sudden movements of either of two targets—a steadily illuminated circle or a flickering circle—one of which stepped back during each saccade it elicited, simulating the effect of a hypermetric saccade. Saccade gain (saccade amplitude/target amplitude) decreased by 15% for the target that stepped back versus 6% for the target that did not step back. Most of the change in gain between successive blocks of trials of each type occurred on the first saccade of the block, decreasing by 0.12 on the first trial of a step-back block and increasing by 0.1 on the first trial of a no-step-back block. The differential adaptation of the two targets required postsaccadic feedback of both target types, as shown in a separate experiment, in which saccades to only one target received feedback, and the gain did not differ between the two target types. This demonstration that a context defined by a visual stimulus can serve as an effective cue for switching saccade gain between states suggests that saccade adaptation may have a heretofore unsuspected dimension of adaptability.

Language Learning Strategies Use by Saudi EFL Students: The Effect of Duration of English Language Study and Gender

2017 ◽  
Vol 7 (1) ◽  
pp. 18 ◽  
Author(s):  
Maha Alhaysony
Keyword(s):  
Language Learning ◽  
Learning Strategies ◽  
English Language ◽  
Language Learning Strategies ◽  
Long Duration ◽  
Significant Difference ◽  
Language Study ◽  
Efl Students ◽  
The Difference ◽  
And Gender

This paper reports findings from a study that investigated language learning strategies (LLS) used by Saudi EFL students at Aljouf University. A total of 134 students (66 males, 68 females) completed a questionnaire adapted from Oxford’s (1990) Strategy Inventory for Language Learning (SILL). The aim of the study was to better understand the relationship between the use of LLS and gender and duration of English language study. The results showed that the average of strategy use was in the low to medium range. Cognitive, metacognitive and compensation strategies were used most frequently, while memory and affective strategies were reported to be least frequently used. The results also showed that female students used more LLS than male students, although the difference was not significant. No significant difference was found in relation to duration of studying English, although students with long duration reported using LLS most frequently. Pedagogical implications of these findings are discussed in relation to Saudi EFL context.

Characterization of Arsenic-Implanted Amorphous Silicon

1992 ◽  
Vol 258 ◽  
Author(s):  
Lynnita Knoch ◽  
N. David Theodore ◽  
Gordon Tam ◽  
Ron Pennell
Keyword(s):  
Amorphous Silicon ◽  
Single Step ◽  
Deposition Condition ◽  
Electrical Measurements ◽  
Rapid Thermal Anneal ◽  
Long Duration ◽  
The Difference ◽  
Polycrystalline Silicon Films ◽  
Clear Change

ABSTRACTIn this study, amorphous silicon and polycrystalline silicon films were implanted with arsenic and subjected to varied low temperature (<900°C) anneal conditions and characterized using TEM. The microstructure is of interest for later correlation with electrical measurements. The amorphous deposition produces larger, more irregular grains with more strain than does the polysilicon deposition for a single-step rapid thermal anneal (RTA) cycle. This can be explained by the number of critical nucleii and the rate of grain growth. The sheet resistivity, as measured by four-point probe, correlates to the deposition conditions. A two-stage anneal makes the grains less irregular by reducing the roughness of the grains and decreasing the strain in the grains. For a given deposition condition, the final microstructure is most strongly influenced by the first anneal. The second anneal produces no clear change in grain size. 800°C anneals result in larger grains than 900°C anneals. This is explained by the presence of less critical nucleii for 800°C anneals. In comparing short and long durations of RTA, the short duration produced slightly larger grains than the long duration RTA due to greater nucleation in the longer RTA wafers. In the case of RTA versus furnace anneals, RTA produces larger, more irregular grains, with more strain in the grains. A model in terms of the size of critical nucleii is used to explain the difference.

scholarly journals Empirical determination of water saturation of porous materials in the process of long duration imbibition

2019 ◽  
Vol 109 ◽  
pp. 00117
Author(s):  
Volodymyr Yelisieiev ◽  
Vasyl Lutsenko ◽  
Tetiana Demchenko ◽  
Vitalii Ruban
Keyword(s):  
Good Accuracy ◽  
Water Saturation ◽  
Process Time ◽  
Saturation Curve ◽  
Porous Bodies ◽  
Theoretical Approaches ◽  
Long Duration ◽  
Empirical Determination ◽  
The Difference

The paper presents the results of an experimental study of the process of imbibition of porous bodies with a long stay in the impregnating medium. Experiments have confirmed, that at time of the order of 100 min there is a significant slowdown in the rise of the saturation curve, which can be taken as the end of the process. However, for the final completion of the process time is needed in the hundreds of times greater and the water saturation can increase more than twice. Experiments showed that with an increase in porosity, the length of the region of a significant deceleration of the impregnation rate tends to decrease. Regardless of the difference in the structures of the tested samples, it was possible to obtain a general analytical expression for describing the process of water saturation, which indicates similarity in the movement of fluid in the system of pore channels. The approximation of the experimental data by a logarithmic function gives a good result of an analytical representation of the process. It is also shown that the theoretical approaches used make it possible to obtain water saturation curves over long periods with good accuracy.

Behavioral Evidence of Separate Adaptation Mechanisms Controlling Saccade Amplitude Lengthening and Shortening

2009 ◽  
Vol 101 (3) ◽  
pp. 1550-1559 ◽  
Author(s):  
Muriel Panouillères ◽  
Tiffany Weiss ◽  
Christian Urquizar ◽  
Roméo Salemme ◽  
Douglas P. Munoz ◽  
...  
Keyword(s):  
Saccadic Eye Movements ◽  
Saccade Amplitude ◽  
Adaptive Changes ◽  
Adaptation Mechanisms ◽  
Amplitude Increase ◽  
Adaptation Condition ◽  
Vector Inversion ◽  
Behavioral Evidence ◽  
Amplitude Decrease

The accuracy of saccadic eye movements is maintained over the long term by adaptation mechanisms that decrease or increase saccade amplitude. It is still unknown whether these opposite adaptive changes rely on common mechanisms. Here, a double-step target paradigm was used to adaptively decrease (backward second target step) or increase (forward step) the amplitude of reactive saccades in one direction only. To test which sensorimotor transformation stages are subjected to these adaptive changes, we measured their transfer to antisaccades in which sensory and motor vectors are spatially dissociated. In the backward adaptation condition, all subjects showed a significant amplitude decrease for adapted prosaccades and a significant transfer of adaptation to antisaccades performed in the adapted direction, but not to oppositely directed antisaccades elicited by a target jump in the adapted direction. In the forward adaptation condition, only 14 of 19 subjects showed a significant amplitude increase for prosaccades and no significant adaptation transfer to antisaccades was detected in either the adapted or nonadapted direction. These findings suggest that, whereas the level(s) of forward adaptation cannot be resolved, the mechanisms involved in backward adaptation of reactive saccades take place at a sensorimotor level downstream from the vector inversion process of antisaccades and differ markedly from those involved in forward adaptation.

scholarly journals P779 Intestinal cancer associated with Crohn’s disease: difference between those with short duration and those with long duration

2020 ◽  
Vol 14 (Supplement_1) ◽  
pp. S617-S618
Author(s):  
M Shinozaki ◽  
R Takahashi
Keyword(s):  
Crohn’S Disease ◽  
Crohn's Disease ◽  
Short Duration ◽  
Cancer Diagnosis ◽  
Significant Proportion ◽  
Intestinal Cancer ◽  
Montreal Classification ◽  
Long Duration ◽  
Increased Risk ◽  
The Difference

Abstract Background Patients with Crohn’s disease (CD) have increased risk of developing intestinal cancer (IC). In patients with ulcerative colitis, cancer risk is thought to increase around 10 years after the onset of colitis. However, in patients with CD, significant proportion of those was with shorter CD duration, and little has been known about the clinical management. The aim of this study was to clarify the clinicopathological characteristics of IC associated with Crohn’s disease with short duration. Methods We searched for IC cases associated with CD from a Japanese medical database (Ichushi). We picked up 272 cases, where we selected the two groups: those with short duration (5 years or less; S-group; n = 51) and those with long duration (15 years or more; L-group; n = 135). The median durations of the two groups were 0 year and 20 years, respectively. Results The age at cancer diagnosis was 51 years (interquartile (40–62)) and 45 (39–56) in S-group and L-group, respectively (p = 0.028). Patients in S-group were significantly older at the time of cancer diagnosis (p &lt; 0.0001). The age at CD diagnosis was older in S-group than that in L-group (51 (38.5–62) years vs. 22 (9–68) years) with statistically significance (p &lt; 0.0001). Relating to disease location of CD according to the Montreal classification, the proportion of L1 and L2 were significantly more in S-group than L-group (31% vs. 18%, and 49% vs. 10%, respectively; p &lt; 0.0001). Penetrating type were significantly less in S group than that in L-group (28% vs. 59%; p = 0.003) in terms of disease behaviour according to the Montreal classification. In Japan, we found that majority of the colorectal cancer associated with CD is located at anorectum. However, in S-group, the proportion of anorectal cancer was only 26%, whereas that in L-group was 69%, and the difference reached statistical significance (p &lt; 0.0001). Well to moderately differentiated adenocarcinoma accounts for 81% in S-group, while the ratio was 44% in L-group, and the difference was significant (p &lt; 0.0001). Mucinous carcinoma was predominant in L-group (39%), and the proportion was significantly lower in S-group (12%; p = 0.0022). Clinical stage was similar in both groups, and the median was stage 2 (interquartile 1–3; p = 0.071). Median survivals were 21 and 26 months, and overall survival was also similar between the two groups (p = 0.51). Conclusion Some features were different between S-group and L-group, while the prognosis was not satisfactory in both groups despite relatively early clinical cancer stage. Older patients with short CD duration should be included as candidates of surveillance for neoplasia.

Visual Versus Motor Vector Inversions in the Antisaccade Task: A Behavioral Investigation With Saccadic Adaptation

2008 ◽  
Vol 99 (5) ◽  
pp. 2708-2718 ◽  
Author(s):  
Thérèse Collins ◽  
Dorine Vergilino-Perez ◽  
Laura Delisle ◽  
Karine Doré-Mazars
Keyword(s):  
Eye Movement ◽  
Visual Target ◽  
Antisaccade Task ◽  
Saccade Amplitude ◽  
Stimulus Position ◽  
Target Vector ◽  
Saccadic Adaptation ◽  
Vector Inversion ◽  
Adaptation Field ◽  
Saccade Adaptation

In the antisaccade task, subjects must execute an eye movement away from a visual target. Correctly executing an antisaccade requires inhibiting a prosaccade toward the visual target and programming a movement to the opposite side. This movement could be based on the inversion of the visual vector, corresponding to the distance between the fixation point and the visual target, or the motor vector of the unwanted prosaccade. We dissociated the two vectors by means of saccadic adaptation. Adaptation can be observed when systematic targeting errors are caused by the displacement of the visual target during the saccade. Adaptation progressively modifies saccade amplitude (defined by the motor vector) such that it becomes appropriate to the postsaccadic stimulus position and thus different from the visual vector of the target. If antisaccade preparation depended on visual vector inversion, rightward prosaccade adaptation should not transfer to leftward antisaccades (which are based on the same visual vector) but should transfer to rightward antisaccades (which are based on a visual vector inside the adaptation field). If antisaccade preparation depended on motor vector inversion, rightward prosaccade adaptation should transfer to leftward antisaccades (which are based on the same, adapted motor vector) but should not transfer to rightward antisaccades (which are based on a nonadapted motor vector). The results are in line with the first hypothesis, showing that vector inversion precedes saccadic adaptation and suggesting that antisaccade preparation depends on the inversion of the visual target vector.

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