Size Distortions: Space-Time Interaction

Perception ◽  
1997 ◽  
Vol 26 (1_suppl) ◽  
pp. 114-114
Author(s):  
S Chukova ◽  
V E Gauzelman
Keyword(s):  
Random Order ◽  
Spatial Separation ◽  
Experimental Session ◽  
Reference Stimulus ◽  
Temporal Separation ◽  
Memory Processing ◽  
Modified Method ◽  
Time Interaction ◽  
Modular Model ◽  
Size Distortions

We used a modified method of constant stimuli to measure spatial interval discrimination thresholds. Horizontal intervals were indicated by a pair of dark vertical lines on a bright background. In each experimental session, thresholds were measured for seven reference stimuli, presented in random order. Reference stimulus separations varied from 9.52 to 16.66 min−1 in increments of 1.95 min−1. The interstimulus interval (ISI) was varied (50, 200, 500, and 1000 ms) between experimental sessions. Stimulus duration was constant at 500 ms. For all ISI durations, the point of subjective equality (PSE) for small spatial separation references was less than physical equality, the PSE for larger separations was greater, and the PSE was close to physical equality for reference stimuli in the centre of the range. This result is consistent with the modular model [V D Glezer, 1995 Vision and Mind (Mahwah, NJ: Lawrence Erlbaum)]. However, the magnitude of the PSE shifts was affected by the ISI duration: at 50 and 1000 ms, the small spatial intervals were more underestimated and the large ones were more overestimated than at 200 or 500 ms. The discriminability thresholds based on the slopes of the psychometric functions varied inversely with the ISI duration, but at the ISI of 1000 ms increased again. These findings demonstrate that in the sequential mode of presentation the temporal separation can be as important as the spatial separation distribution in determining the PSE. This suggests that these size distortions result more from memory processing than from spatial processing.

scholarly journals Comparison of the Spatial Limits on Direction Selectivity in Visual Areas MT and V1

2005 ◽  
Vol 93 (3) ◽  
pp. 1235-1245 ◽  
Author(s):  
Mark M. Churchland ◽  
Nicholas J. Priebe ◽  
Stephen G. Lisberger
Keyword(s):  
Apparent Motion ◽  
Great Majority ◽  
Spatial Separation ◽  
Direction Selectivity ◽  
Temporal Separation ◽  
Temporal Area ◽  
Mean Values ◽  
V1 Neurons ◽  
Preferred Direction ◽  
The Difference

We recorded responses to apparent motion from directionally selective neurons in primary visual cortex (V1) of anesthetized monkeys and middle temporal area (MT) of awake monkeys. Apparent motion consisted of multiple stationary stimulus flashes presented in sequence, characterized by their temporal separation (Δ t) and spatial separation (Δ x). Stimuli were 8° square patterns of 100% correlated random dots that moved at apparent speeds of 16 or 32°/s. For both V1 and MT, the difference between the response to the preferred and null directions declined with increasing flash separation. For each neuron, we estimated the maximum flash separation for which directionally selective responses were observed. For the range of speeds we used, Δ x provided a better description of the limitation on directional responses than did Δ t. When comparing MT and V1 neurons of similar preferred speed, there was no difference in the maximum Δ x between our samples from the two areas. In both V1 and MT, the great majority of neurons had maximal values of Δ x in the 0.25–1° range. Mean values were almost identical between the two areas. For most neurons, larger flash separations led to both weaker responses to the preferred direction and increased responses to the opposite direction. The former mechanism was slightly more dominant in MT and the latter slightly more dominant in V1. We conclude that V1 and MT neurons lose direction selectivity for similar values of Δ x, supporting the hypothesis that basic direction selectivity in MT is inherited from V1, at least over the range of stimulus speeds represented by both areas.

The incidence of killer activity and extracellular proteases in tropical yeast communities

1997 ◽  
Vol 43 (4) ◽  
pp. 328-336 ◽  
Author(s):  
Jacqueline Abranches ◽  
Leda C. Mendonça-Hagler ◽  
Allen N. Hagler ◽  
Paula B. Morais ◽  
Carlos A. Rosa
Keyword(s):  
Killer Toxin ◽  
Spatial Separation ◽  
Extracellular Proteases ◽  
Temporal Separation ◽  
Killer Activity ◽  
Killer Yeasts ◽  
Sporobolomyces Roseus ◽  
Nitrogen Nutrients ◽  
Pichia Kluyveri ◽  
Ascomycetous Yeasts

The presence of killer and proteolytic yeasts was studied among 944 isolates representing 105 species from tropical yeast communities. We found 13 killer toxin producing species, with Pichia kluyveri being the most frequent. Other killer yeast isolates were Candida apis, Candida bombicola, Candida fructus, Candida krusei, Candida sorbosa, Hanseniaspora uvarum, Issatchenkia occidentalis, Kloeckera apis, Kluyveromyces marxianus, Pichia membranaefaciens, Pichia ohmeri-like, and Sporobolomyces roseus. The communities from which killer yeasts were isolated had strains sensitive to them, and there were interspecific and intraspecific differences in the spectra of their killer activities. Pichia kluyveri had the broadest spectra of activity against sensitive isolates, and it apparently produced different toxins. The coexistence of sensitive and killer yeasts using the same substrate suggests that there is spatial separation in microhabitats or temporal separation in different stages of successions. Basidiomycetous yeasts were more frequently proteolytic than ascomycetous yeasts. Extracellular proteases could be important for the yeasts to have access to more nitrogen nutrients and obtain a better balance with available carbon sources.Key words: killer yeasts, extracellular proteases, tropical yeast communities.

Divergence Thresholds as Functions of Temporal Separation, Spatial Separation, and Retinal Locus

1983 ◽  
Vol 56 (2) ◽  
pp. 459-468 ◽  
Author(s):  
Marjorie J. Di Orio ◽  
Thomas L. Harrington
Keyword(s):  
Spatial Separation ◽  
Retinal Locus ◽  
Line Density ◽  
Information Analysis ◽  
Angular Divergence ◽  
Temporal Separation ◽  
Line Segments ◽  
Fast Motion ◽  
Straight Lines ◽  
Form Information

Human thresholds were measured for the detection of angular divergence between straight lines using pairs of line segments. The dependence of these thresholds on temporal separation between the two lines, spatial separation, and retinal locus was assessed. Results were comparable to prior divergence thresholds obtained by Harrington and Harrington in their study of “blur patterns.” In blur patterns motion parameters may be processed partly or wholly as form information rather than as motion information per se. Harrington and Harrington had used moderate blurring velocities, for which information on both motion and form were present. Observers may have been responding either to motion or to form. The study reported here used briefly presented two-line “blur patterns” with only form information. Analysis suggested that the form components of fast motion-produced blur patterns could be processed by the human visual system. Neither temporal nor spatial separation was a significant determiner of thresholds in accordance with Harrington and Harrington who found no effect of blur-line density in the range studied. Retinal locus was a factor as it was with blur patterns. Some possible mechanisms for the detection of divergence indicated by these results are discussed.

Resource partitioning between two species of Ceutorhynchus (Coleoptera: Curculionidae) on Echium plantagineum in a Mediterranean habitat

1993 ◽  
Vol 83 (3) ◽  
pp. 345-351 ◽  
Author(s):  
Guy J. Forrester
Keyword(s):  
Biological Control ◽  
Resource Partitioning ◽  
Spatial Separation ◽  
Temporal Separation ◽  
Southern France ◽  
Early Larval Stage ◽  
Tap Root ◽  
Mediterranean Habitat ◽  
Different Parts ◽  
Original Index

AbstractTwo weevil species, Ceutorhynchus geographicus (Goeze) and C. larvatus Schultze, feed on Echium plantagineum (Boraginaceae) in southern France. This paper shows that they do not compete for resources in the host's native environment. Niche overlaps of the two weevils were measured using the proportional overlap measure and Morisita's original index. The two species showed significant overlap in niche requirements during the egg and early larval stage. During the final two larval instars, larvae feed on different parts of the plant, C. geographicus in the tap root and C. larvatus in the root crown. Spatial separation in niche requirements is augmented by a temporal separation, C. larvatus emerging in the field about one month earlier than C. geographicus. In Europe and in Australia, to which E. plantagineum has been introduced and has become a serious weed, the host-plant has an extended germination period during the autumn. The differences in emergence times of the two species mean that their niches are separated both in time and in space. Should the two species be released into Australia they would not compete for resources. They may, however, be able to displace other species of the stemfeeding guild that are also proposed as candidates for the biological control of E. plantagineum.

Effects of nitric oxide synthase inhibitor on decrease in peripheral arterial stiffness with acute low-intensity aerobic exercise

2004 ◽  
Vol 287 (6) ◽  
pp. H2666-H2669 ◽  
Author(s):  
Jun Sugawara ◽  
Seiji Maeda ◽  
Takeshi Otsuki ◽  
Takumi Tanabe ◽  
Ryuichi Ajisaka ◽  
...  
Keyword(s):  
Arterial Stiffness ◽  
Aerobic Exercise ◽  
Short Duration ◽  
Random Order ◽  
Posterior Tibial Artery ◽  
Nitric Oxide Synthase Inhibitor ◽  
Low Intensity ◽  
Time Interaction ◽  
Peripheral Arterial ◽  
Synthase Inhibitor

We previously reported that even low-intensity, short-duration acute aerobic exercise decreases arterial stiffness. We aimed to test the hypothesis that the exercise-induced decrease in arterial stiffness is caused by the increased production of NO in vascular endothelium with exercise. Nine healthy men (age: ∼22–28 yr) performed a 5-min single-leg cycling exercise (30 W) in the supine position under an intravenous infusion of NG-monomethyl-l-arginine (l-NMMA; 3 mg/kg during the initial 5 min and subsequent continuous infusion of 50 μg·kg−1·min−1 in saline) or vehicle (saline) in random order on separate days. The pulse wave velocity (PWV) from the femoral to posterior tibial artery was measured on both legs before and after the infusion at rest and 2 min after exercise. Under the control condition, exercised leg PWV significantly decreased after exercise ( P < 0.05), whereas nonexercised leg PWV did not show a significant change throughout the experiment. Under l-NMMA administration, exercised leg PWV was increased significantly by the infusion ( P < 0.05) but decreased significantly after the exercise ( P < 0.05). Nonexercised leg PWV increased with l-NMMA administration and maintained a significantly higher level during the administration compared with baseline (before the infusion, all P < 0.05). The NO synthase blockade × time interaction on exercised leg PWV was not significant ( P = 0.706). These results suggest that increased production of NO is not a major factor in the decrease of regional arterial stiffness with low-intensity, short-duration aerobic exercise.

No teleworker is an island: The impact of temporal and spatial separation along with media use on knowledge sharing networks

2019 ◽  
Vol 34 (3) ◽  
pp. 243-262 ◽  
Author(s):  
Nick van der Meulen ◽  
Peter van Baalen ◽  
Eric van Heck ◽  
Sipko Mülder
Keyword(s):  
Knowledge Sharing ◽  
Spatial Separation ◽  
Negative Effects ◽  
Temporal Separation ◽  
Media Synchronicity ◽  
Depth Study ◽  
Negative Effect ◽  
Effects Of Media ◽  
The Impact

Despite its prevalence, there is a lack of understanding regarding the effect of telework on an organization’s knowledge base. Recognizing the enabling role of electronic communication media, this article therefore addresses the interaction effects of media synchronicity and temporal as well as spatial separation among colleagues on sharing in knowledge networks. Special attention is paid to knowledge awareness (a form of metaknowledge representing “who knows what”) as well as homogeneous and heterogeneous knowledge sources to further explicate the relationship between coworker separation and knowledge sharing. Multiple surveys were placed between two smaller ethnographic investigations and combined with whole network data to form an in-depth study of 64 knowledge workers at a medium-sized European research and advisory organization. The results reveal that spatial separation directly reduces the frequency of knowledge sharing between colleagues, whereas temporal separation affects knowledge sharing through reduced knowledge awareness, resulting in lower job and proactive performance. The use of asynchronous media can serve to mitigate most of the negative effects of spatial separation on knowledge sharing but may also exacerbate the negative effect of temporal separation on teleworkers’ knowledge awareness of colleagues with identical expertise.

scholarly journals Infection dynamics of two renal myxozoans in hatchery reared fry and juvenile Atlantic cod Gadus morhua L.

Parasitology ◽  
2010 ◽  
Vol 137 (10) ◽  
pp. 1501-1513 ◽  
Author(s):  
A. S. HOLZER ◽  
S. STEWART ◽  
A. TILDESLEY ◽  
R. WOOTTEN ◽  
C. SOMMERVILLE
Keyword(s):  
Growth Performance ◽  
Gadus Morhua ◽  
Prolonged Exposure ◽  
Atlantic Cod ◽  
Spatial Separation ◽  
Renal Tubules ◽  
Performance Study ◽  
Temporal Separation ◽  
Infection Dynamics ◽  
Before And After

SUMMARYIn order to study the infection dynamics of 2 renal myxozoans, Zschokkella hildae Auerbach, 1910 and Gadimyxa atlanticaKøie, Karlsbakk and Nylund, 2007 in cultured Atlantic cod, Gadus morhua L. aged 3–19 months, a specific single-round PCR assay and a double-label in situ hybridization protocol were developed. The results demonstrated that the 2 myxozoans show spatial separation of their development with regard to spore formation inside the renal tubules versus the collecting ducts and ureters, as well as temporal separation with Z. hildae proliferating and developing spores only once the G. atlantica infection decreases, despite the presence of both myxozoans in the smallest fry studied. These results strongly suggest within-host competition of the 2 myxozoans with potential suppression of Z. hildae by G. atlantica until G. morhua acquires immunity against G. atlantica. The quantification of the G. atlantica infection inside the renal tubules before and after a 29-day experimental growth performance study using fry from hatcheries with differing filtration systems showed that the intensity of infection with G. atlantica seems to be controlled if prolonged exposure to the myxozoan transmission stages takes place from hatching onwards. Surprisingly, growth rates in the trial were inversely affected suggesting that G. atlantica does not negatively influence cod fry growth performance.

scholarly journals Effects of Transdermal Methylsulfonylmethane on Muscle Damage and Recovery Following Eccentric Exercise

2021 ◽  
Vol 30 (2) ◽  
pp. 158-166
Author(s):  
Hyeon-deok Jo ◽  
Choun-sub Kim ◽  
Maeng-kyu Kim
Keyword(s):  
Muscle Damage ◽  
Eccentric Exercise ◽  
Muscle Soreness ◽  
Random Order ◽  
Experimental Session ◽  
Maximal Voluntary Isometric Contraction ◽  
Positive Effects ◽  
Transdermal Application ◽  
Before And After ◽  
Exercise Induced

PURPOSE:The present study aimed to investigate the effects of transdermal application of methylsulfonylmethane (MSM) on muscle damage and recovery following eccentric exercise in young men.METHODS: Eleven college-aged men without any cardiovascular or orthopedic disorders underwent two sessions consisting of a control session (CS) and an experimental session (ES) in a random order with at least 2 weeks of wash-out between the sessions. The participants performed 30 maximal eccentric exercises involving their non-dominant elbow flexors in each session. Circumference, muscle soreness, range of motion, maximal voluntary isometric contraction (MVIC), and muscular echo intensity (EI) were measured to evaluate the changes in the level of exercise-induced muscle damage (EIMD). All measurements were performed at 24, 48, 72, and 96 hours after exercise and also immediately before and after exercise.RESULTS:Transdermal application of MSM in ES attenuated muscle swelling and decreased MVIC after eccentric exercise when compared with CS. Muscle soreness and EI tended to increase less rapidly and decrease more rapidly in ES than in CS.CONCLUSIONS: Transdermal application of MSM may induce relatively positive effects on EIMD and recovery following eccentric exercise when compared with the treatment that has been widely used previously.

Oxidative Stress in Response to Forearm Ischemia-reperfusion with and without Carnitine Administration

2010 ◽  
Vol 80 (1) ◽  
pp. 12-23 ◽  
Author(s):  
Richard J. Bloomer ◽  
Webb A. Smith ◽  
Kelsey H. Fisher-Wellman
Keyword(s):  
Oxidative Stress ◽  
Ischemia Reperfusion ◽  
Reactive Hyperemia ◽  
Oral Intake ◽  
Random Order ◽  
Trolox Equivalent Antioxidant Capacity ◽  
Oxidative Stress Biomarkers ◽  
Double Blind ◽  
Stress Biomarkers ◽  
Time Interaction

We have recently noted a decrease in lipid peroxidation with oral intake of glycine propionyl-L-carnitine (GPLC). However, these findings were observed at rest, and in previously sedentary subjects. Methods: We determined the effect of GPLC on oxidative stress biomarkers at rest and in response to reactive hyperemia in exercise-trained men. Using a double-blind, crossover design, 15 healthy men were assigned to a placebo and GPLC (4.5 g/day) in random order, for four weeks, with a two-week washout between assignments. Blood samples were collected at rest and at 0, 3, and 10 minutes following a protocol of ischemia-reperfusion, and analyzed for lactate, malondialdehyde (MDA), F2-isoprostanes (F2-iso), hydrogen peroxide (H2O2), xanthine oxidase activity (XO), hypoxanthine (HYPO), total (TGSH) and oxidized (GSSG) glutathione, and Trolox-equivalent antioxidant capacity (TEAC). Results: No condition or condition by time interaction effects were noted (p>0.05). Time effects were noted for lactate (p<0.0001), MDA (p=0.02), H2O2 (p=0.0003), XO (p=0.03), HYPO (p<0.0001), TGSH (p=0.02), and GSSG (p<0.0001), with peak values noted at 0 minutes post for lactate, MDA, TGSH, and GSSG, at 3 minutes post for H2O2 and XO, and at 10 minutes post for HYPO. F2-iso and TEAC were unaffected by treatment or protocol (p>0.05). Conclusion: Short-term ischemia-reperfusion in trained men results in a modest and transient increase in selected blood oxidative stress biomarkers. Oral GPLC supplementation does not attenuate the increase in these biomarkers.

Effect of Different Circuit Training on Cardiovascular Responses in Cirrhotic Patients

2018 ◽  
Vol 40 (02) ◽  
pp. 139-146 ◽  
Author(s):  
Igor Nasser ◽  
Jeffrey Willardson ◽  
Renata de Mello Perez ◽  
Michel Reis ◽  
Anderson de Azevedo Brito ◽  
...  
Keyword(s):  
Heart Rate ◽  
Liver Cirrhosis ◽  
Resistance Training ◽  
Random Order ◽  
Cardiovascular Responses ◽  
Experimental Session ◽  
Cirrhotic Patients ◽  
Circuit Resistance Training ◽  
Circuit Resistance ◽  
Rest Intervals

AbstractThe purpose of this study was to analyze and compare heart rate (HR), heart rate variability (HRV), and blood pressure (BP) responses during and after circuit resistance training with 1 min. (CIR1) vs. 2 min. (CIR2) rest intervals between exercises in liver cirrhosis patients. 10 patients (7 women, 3 men) participated in 2 experimental sessions (CIR1 and CIR2) in random order. Each experimental session consisted of 6 exercises performed for 3 sets of 10 repetitions with 70% of the 10-RM load. The only difference between experimental sessions was taking either 1 min. (CIR1) or 2 min. (CIR2) of rest between exercises. Prior and during each session, BP, HR and HRV (beat-to-beat intervals) were assessed. Training efficiency were significant higher for CIR1 when compared to CIR2, since same total training volume was performed in less time. Both protocols elicited significant changes in HR, SBP, and SampEn. Based on the ∆HR and ∆IRR between protocols, higher cardiovascular stress was observed for CIR1 vs. CIR2. However, the patients presented a similar recovery pattern between experimental sessions, and did not present significant alterations in the HRV at 60 min post-workout. In summary, the fast adjustment of autonomic modulation in HRV and BP suggests that circuit resistance training with 1-min or 2-min rest intervals between exercises elicits typical cardiovascular responses in liver cirrhosis patients.

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