scholarly journals The effect of stimulus area on global motion thresholds in children and adults

2017 ◽  
Vol 17 (10) ◽  
pp. 435
Author(s):  
Kimberly Meier ◽  
Farnaz Javadian ◽  
Kevin Chang ◽  
Deborah Giaschi
Keyword(s):  
Global Motion ◽  
Stimulus Area

scholarly journals The Effect of Stimulus Area on Global Motion Thresholds in Children and Adults

Vision ◽  
2019 ◽  
Vol 3 (1) ◽  
pp. 10
Author(s):  
Kimberly Meier ◽  
Deborah Giaschi
Keyword(s):  
Motion Perception ◽  
Spatial Integration ◽  
Global Motion ◽  
Motion Stimulus ◽  
Stimulus Area ◽  
Displacement Condition ◽  
Per Se ◽  
Spatial Displacements ◽  
Late Maturation ◽  
The Impact

Performance on random-dot global motion tasks may reach adult-like levels before 4 or as late as 16 years of age, depending on the specific parameters used to create the stimuli. Later maturation has been found for slower speeds, smaller spatial displacements, and sparser dot arrays. This protracted development on global motion tasks may depend on limitations specific to spatial aspects of a motion stimulus rather than to motion mechanisms per se. The current study investigated the impact of varying stimulus area (9, 36, and 81 deg2) on the global motion coherence thresholds of children 4–6 years old and adults for three signal dot displacements (∆x = 1, 5, and 30 arcmin). We aimed to determine whether children could achieve mature performance for the smallest displacements, a condition previously found to show late maturation, when a larger stimulus area was used. Coherence thresholds were higher in children compared to adults in the 1 and 5 arcmin displacement conditions, as reported previously, and this did not change as a function of stimulus area. However, both children and adults performed better with a larger stimulus area in the 30 arcmin displacement condition only. This suggests that immature spatial integration, as measured by stimulus area, cannot account for immaturities in global motion perception.

Improving motion detection via anodal transcranial direct current stimulation

2020 ◽  
Vol 38 (5) ◽  
pp. 395-405
Author(s):  
Luca Battaglini ◽  
Federica Mena ◽  
Clara Casco
Keyword(s):  
Direct Current ◽  
Signal To Noise Ratio ◽  
Individual Performance ◽  
Coherent Motion ◽  
Motion Processing ◽  
Global Motion ◽  
Local Motion ◽  
Processing Efficiency ◽  
Temporal Area ◽  
Direct Current Stimulation

Background: To study motion perception, a stimulus consisting of a field of small, moving dots is often used. Generally, some of the dots coherently move in the same direction (signal) while the rest move randomly (noise). A percept of global coherent motion (CM) results when many different local motion signals are combined. CM computation is a complex process that requires the integrity of the middle-temporal area (MT/V5) and there is evidence that increasing the number of dots presented in the stimulus makes such computation more efficient. Objective: In this study, we explored whether anodal direct current stimulation (tDCS) over MT/V5 would increase individual performance in a CM task at a low signal-to-noise ratio (SNR, i.e. low percentage of coherent dots) and with a target consisting of a large number of moving dots (high dot numerosity, e.g. >250 dots) with respect to low dot numerosity (<60 dots), indicating that tDCS favour the integration of local motion signal into a single global percept (global motion). Method: Participants were asked to perform a CM detection task (two-interval forced-choice, 2IFC) while they received anodal, cathodal, or sham stimulation on three different days. Results: Our findings showed no effect of cathodal tDCS with respect to the sham condition. Instead, anodal tDCS improves performance, but mostly when dot numerosity is high (>400 dots) to promote efficient global motion processing. Conclusions: The present study suggests that tDCS may be used under appropriate stimulus conditions (low SNR and high dot numerosity) to boost the global motion processing efficiency, and may be useful to empower clinical protocols to treat visual deficits.

scholarly journals Coherent global motion in the absence of coherent velocity signals

2000 ◽  
Vol 10 (11) ◽  
pp. 679-682 ◽  
Author(s):  
John Ross ◽  
David R. Badcock ◽  
Anthony Hayes
Keyword(s):  
Global Motion

scholarly journals Global motion compensated visual attention-based video watermarking

2016 ◽  
Vol 25 (6) ◽  
pp. 061624 ◽  
Author(s):  
Matthew Oakes ◽  
Deepayan Bhowmik ◽  
Charith Abhayaratne
Keyword(s):  
Visual Attention ◽  
Video Watermarking ◽  
Global Motion

Onset of Natural Convection from a Suddenly Heated Horizontal Cylinder

1980 ◽  
Vol 102 (4) ◽  
pp. 636-639 ◽  
Author(s):  
J. R. Parsons ◽  
J. C. Mulligan
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Thermal Stability ◽  
Heat Capacity ◽  
Natural Convection ◽  
Stability Analysis ◽  
Horizontal Cylinder ◽  
Finite Cylinder ◽  
Global Motion ◽  
Experimental Apparatus

A study of the onset of transient natural convection from a suddenly heated, horizontal cylinder of finite diameter is presented. The termination of the initial conductive and “locally” conuectiue heat transfer regime which precedes the onset of global natural convection is treated as a thermal stability phenomenon. An analysis is presented wherein the effects of finite cylinder diameter, cylinder heat capacity, and cylinder thermal conductivity are included in calculations of the convective delay time. A simple experimental apparatus is described and data presented. The thermal stability analysis is confirmed experimentally and data is presented which indicates localized natural convection prior to global motion.

Sign in / Sign up

Export Citation Format

Share Document