scholarly journals Spatial vision deficit underlies poor sine-wave motion direction discrimination in anisometropic amblyopia

2007 ◽  
Vol 7 (11) ◽  
pp. 7 ◽  
Author(s):  
Zhuping Qiu ◽  
Pengjing Xu ◽  
Yifeng Zhou ◽  
Zhong-Lin Lu
Keyword(s):  
Wave Motion ◽  
Spatial Vision ◽  
Sine Wave ◽  
Motion Direction ◽  
Anisometropic Amblyopia ◽  
Direction Discrimination

scholarly journals Electrophysiological aftereffects of high-frequency transcranial random noise stimulation (hf-tRNS): an EEG investigation

2021 ◽  
Author(s):  
Filippo Ghin ◽  
Louise O’Hare ◽  
Andrea Pavan
Keyword(s):  
High Frequency ◽  
Discrimination Task ◽  
Temporal Dynamics ◽  
Random Noise ◽  
Decomposition Analysis ◽  
Oscillatory Activity ◽  
Motion Direction ◽  
Time Frequency ◽  
Direction Discrimination ◽  
Transcranial Random Noise Stimulation

AbstractThere is evidence that high-frequency transcranial random noise stimulation (hf-tRNS) is effective in improving behavioural performance in several visual tasks. However, so far there has been limited research into the spatial and temporal characteristics of hf-tRNS-induced facilitatory effects. In the present study, electroencephalogram (EEG) was used to investigate the spatial and temporal dynamics of cortical activity modulated by offline hf-tRNS on performance on a motion direction discrimination task. We used EEG to measure the amplitude of motion-related VEPs over the parieto-occipital cortex, as well as oscillatory power spectral density (PSD) at rest. A time–frequency decomposition analysis was also performed to investigate the shift in event-related spectral perturbation (ERSP) in response to the motion stimuli between the pre- and post-stimulation period. The results showed that the accuracy of the motion direction discrimination task was not modulated by offline hf-tRNS. Although the motion task was able to elicit motion-dependent VEP components (P1, N2, and P2), none of them showed any significant change between pre- and post-stimulation. We also found a time-dependent increase of the PSD in alpha and beta bands regardless of the stimulation protocol. Finally, time–frequency analysis showed a modulation of ERSP power in the hf-tRNS condition for gamma activity when compared to pre-stimulation periods and Sham stimulation. Overall, these results show that offline hf-tRNS may induce moderate aftereffects in brain oscillatory activity.

Human Updating of Visual Motion Direction During Head Rotations

2008 ◽  
Vol 99 (5) ◽  
pp. 2558-2576
Author(s):  
Mario Ruiz-Ruiz ◽  
Julio C. Martinez-Trujillo
Keyword(s):  
Visual Motion ◽  
Human Subjects ◽  
Head Tilt ◽  
Head Rotation ◽  
Three Dimensions ◽  
Spatial Updating ◽  
Motion Direction ◽  
Direction Discrimination ◽  
Head Rotations ◽  
Stimulus Direction

Previous studies have demonstrated that human subjects update the location of visual targets for saccades after head and body movements and in the absence of visual feedback. This phenomenon is known as spatial updating. Here we investigated whether a similar mechanism exists for the perception of motion direction. We recorded eye positions in three dimensions and behavioral responses in seven subjects during a motion task in two different conditions: when the subject's head remained stationary and when subjects rotated their heads around an anteroposterior axis (head tilt). We demonstrated that after head-tilt subjects updated the direction of saccades made in the perceived stimulus direction (direction of motion updating), the amount of updating varied across subjects and stimulus directions, the amount of motion direction updating was highly correlated with the amount of spatial updating during a memory-guided saccade task, subjects updated the stimulus direction during a two-alternative forced-choice direction discrimination task in the absence of saccadic eye movements (perceptual updating), perceptual updating was more accurate than motion direction updating involving saccades, and subjects updated motion direction similarly during active and passive head rotation. These results demonstrate the existence of an updating mechanism for the perception of motion direction in the human brain that operates during active and passive head rotations and that resembles the one of spatial updating. Such a mechanism operates during different tasks involving different motor and perceptual skills (saccade and motion direction discrimination) with different degrees of accuracy.

scholarly journals Influence of the driving frequency and equivalent parameters on displacement amplitude of electrostatic linear comb actuator

2018 ◽  
Vol 40 (4) ◽  
pp. 397-306
Author(s):  
Hoang Trung Kien ◽  
Vu Cong Ham ◽  
Pham Hong Phuc
Keyword(s):  
Sine Wave ◽  
Displacement Amplitude ◽  
Damping Factor ◽  
Driving Voltage ◽  
Driving Frequency ◽  
Dynamic Parameters ◽  
Motion Direction ◽  
Amplitude Error ◽  
Differential Motion ◽  
Air Damping

A new method determining the equivalent dynamic parameters such as stiffness, vibrating mass, and air damping factor in motion direction of shuttle (i.e. in y-direction) is proposed, thence the differential motion equation of shuttle is established and solved to achieve a typical displacement formula. Simulation and experimental results show that the change of ELCA' displacement is inappreciable while the range of driving frequency up to 27 Hz (error of 10% with driving voltage is a square wave). Moreover, the range of driving frequency for the ELCA can be extended up to 1 kHz with displacement amplitude error of 10% while the shape of driving voltage is a harmonic sine wave.

scholarly journals Impaired spatial and binocular summation for motion direction discrimination in strabismic amblyopia

2011 ◽  
Vol 51 (6) ◽  
pp. 577-584 ◽  
Author(s):  
Benjamin Thompson ◽  
Alby Richard ◽  
Jan Churan ◽  
Robert F. Hess ◽  
Craig Aaen-Stockdale ◽  
...  
Keyword(s):  
Binocular Summation ◽  
Motion Direction ◽  
Strabismic Amblyopia ◽  
Direction Discrimination

Low-level processing deficits underlying poor contrast sensitivity for moving plaids in anisometropic amblyopia

2012 ◽  
Vol 29 (6) ◽  
pp. 315-323 ◽  
Author(s):  
YONG TANG ◽  
LINYI CHEN ◽  
ZHONGJIAN LIU ◽  
CAIYUAN LIU ◽  
YIFENG ZHOU
Keyword(s):  
Contrast Sensitivity ◽  
Significant Loss ◽  
Extrastriate Cortex ◽  
Motion Processing ◽  
Motion Direction ◽  
Temporal Area ◽  
Anisometropic Amblyopia ◽  
Low Level ◽  
Spatial Frequencies ◽  
Processing Deficits

AbstractMany studies using random dot kinematograms have indicated a global motion processing deficit originated from extrastriate cortex, specifically middle temporal area (MT) and media superior temporal area (MST), in patients with amblyopia. However, the nature of this deficit remains unclear. To explore whether the ability of motion integration is impaired in amblyopia, contrast sensitivity for moving plaids and their corresponding component gratings were measured over a range of stimulus durations and spatial and temporal frequencies in 10 control subjects and 13 anisometropic amblyopes by using a motion direction discrimination task. The results indicated a significant loss of contrast sensitivity for moving plaids as well as for moving gratings at intermediate and high spatial frequencies in amblyopic eyes (AEs). Additionally, we found that the loss of contrast sensitivity for moving plaids was statistically equivalent to that for moving component gratings in AEs, that is, the former could be almost completely accounted for by the latter. These results suggest that the integration of motion information conveyed by component gratings of moving plaids may be intact in anisometropic amblyopia, and that the apparent deficits in contrast sensitivity for moving plaids in anisometropic amblyopia can be almost completely attributed to those for gratings, that is, low-level processing deficits.

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