scholarly journals Effects of Crowding and Attention on High-Levels of Motion Processing and Motion Adaptation

PLoS ONE ◽  
2015 ◽  
Vol 10 (1) ◽  
pp. e0117233 ◽  
Author(s):  
Andrea Pavan ◽  
Mark W. Greenlee
Keyword(s):  
Motion Processing ◽  
Motion Adaptation

Neuroimaging of Direction-Selective Mechanisms for Second-Order Motion

2003 ◽  
Vol 90 (5) ◽  
pp. 3242-3254 ◽  
Author(s):  
Shin'ya Nishida ◽  
Yuka Sasaki ◽  
Ikuya Murakami ◽  
Takeo Watanabe ◽  
Roger B. H. Tootell
Keyword(s):  
Neural Substrates ◽  
Neural Correlates ◽  
Selective Adaptation ◽  
Motion Processing ◽  
Motion Adaptation ◽  
Motion Stimulus ◽  
Fmri Study ◽  
Wide Range ◽  
Contingent Response ◽  
Visual Cortical

Psychophysical findings have revealed a functional segregation of processing for 1st-order motion (movement of luminance modulation) and 2nd-order motion (e.g., movement of contrast modulation). However neural correlates of this psychophysical distinction remain controversial. To test for a corresponding anatomical segregation, we conducted a new functional magnetic resonance imaging (fMRI) study to localize direction-selective cortical mechanisms for 1st- and 2nd-order motion stimuli, by measuring direction-contingent response changes induced by motion adaptation, with deliberate control of attention. The 2nd-order motion stimulus generated direction-selective adaptation in a wide range of visual cortical areas, including areas V1, V2, V3, VP, V3A, V4v, and MT+. Moreover, the pattern of activity was similar to that obtained with 1st-order motion stimuli. Contrary to expectations from psychophysics, these results suggest that in the human visual cortex, the direction of 2nd-order motion is represented as early as V1. In addition, we found no obvious anatomical segregation in the neural substrates for 1st- and 2nd-order motion processing that can be resolved using standard fMRI.

A Single System Explains Human Speed Perception

2006 ◽  
Vol 18 (11) ◽  
pp. 1808-1819 ◽  
Author(s):  
Jeroen J. A. van Boxtel ◽  
Raymond van Ee ◽  
Casper J. Erkelens
Keyword(s):  
Visual System ◽  
Computational Models ◽  
Motion Processing ◽  
Single System ◽  
Motion Adaptation ◽  
Low Level ◽  
Psychophysical Data ◽  
Motion System ◽  
Speed Perception ◽  
Direction Information

Motion is fully described by a direction and a speed. The processing of direction information by the visual system has been extensively studied; much less is known, however, about the processing of speed. Although it is generally accepted that the direction of motion is processed by a single motion system, no such consensus exists for speed. Psychophysical data from humans suggest two separate systems processing luminance-based fast and slow speeds, whereas neurophysiological recordings in monkeys generally show continuous speed representation, hinting at a single system. Although the neurophysiological findings hint at a single system, they remain inconclusive as only a limited amount of cells can be measured per study and, possibly, the putative different motion systems are anatomically separate. In three psychophysical motion adaptation experiments, we show that predictions on the basis of the two-motion system hypothesis are not met. Instead, concurrent modeling showed that both here-presented and previous data are consistent with a single system subserving human speed perception. These findings have important implications for computational models of motion processing and the low-level organization of the process.

scholarly journals USING TRANSCRANIAL MAGNETIC STIMULATION (TMS) TO PROBE EFFECTS OF VISUAL MOTION ADAPTATION ON PRIMARY VISUAL CORTEX (V1) EXCITABILITY IN BILATERAL VESTIBULAR FAILURE (BVF) PATIENTS

2015 ◽  
Vol 86 (11) ◽  
pp. e4.70-e4
Author(s):  
Hena Ahmad ◽  
Richard Roberts ◽  
Qadeer Arshad Arshad ◽  
Mitesh Patel ◽  
Adolfo Bronstein
Keyword(s):  
Visual Motion ◽  
Cortical Plasticity ◽  
Cortical Excitability ◽  
Motion Processing ◽  
Motion Adaptation ◽  
Visual Motion Perception ◽  
Ocular Reflex ◽  
Visual Motion Processing ◽  
Vestibulo Ocular Reflex ◽  
Visual Cortical

Background and aimPatients with BVF report oscillopsia due to a defective vestibulo-ocular reflex causing retinal slip. No previous studies have probed visual cortical excitability using TMS and visual motion processing in these patients. We investigated the effects of visual motion adaptation on V1 cortical excitability in BVF patients and correlated this with psychophysical parameters.Methods12 BVF patients (7 males) aged 29–65 (mean=54.5) and 12 controls (6 males) aged 42–73 (mean=55) were recruited. Biphasic TMS pulses were applied at V1 and phosphene threshold (PT) was estimated. 3 measurement phases were (1) Stationary (2) Motion with optokinetic stimulation (OKS) Adaptation: OKS rightwards for 5 minutes 3) Post adaptation during viewing motion. All subjects completed questionnaires prior to the experiment. Results were analysed offline by calculating the probability of phosphene perception.ResultsBaseline phosphene thresholds were significantly higher in BVF patients (p=0.024) reflecting reduced visual cortical excitability. Lower oscillopsia scores correlated with reduced baseline V1 excitability (p=0.009).ConclusionsThis novel finding acts as a neurophysiological correlate for clinical observations of adaptive visual motion perception and is also correlated with psychophysical parameters. These results provide evidence for adaptive mechanisms leading to cortical plasticity following BVF.

scholarly journals Adaptation to Real Motion Reveals Direction-selective Interactions between Real and Implied Motion Processing

2007 ◽  
Vol 19 (8) ◽  
pp. 1231-1240 ◽  
Author(s):  
Jeannette A. M. Lorteije ◽  
J. Leon Kenemans ◽  
Tjeerd Jellema ◽  
Rob H. J. van der Lubbe ◽  
Marjolein W. Lommers ◽  
...  
Keyword(s):  
Stimulus Onset ◽  
Motion Processing ◽  
Motion Adaptation ◽  
Real Motion ◽  
Motion Response ◽  
Implied Motion ◽  
Static Pictures ◽  
The Difference ◽  
Random Dot Patterns ◽  
Motion Amplitude

Viewing static pictures of running humans evokes neural activity in the dorsal motion-sensitive cortex. To establish whether this response arises from direction-selective neurons that are also involved in real motion processing, we measured the visually evoked potential to implied motion following adaptation to static or moving random dot patterns. The implied motion response was defined as the difference between evoked potentials to pictures with and without implied motion. Interaction between real and implied motion was found as a modulation of this difference response by the preceding motion adaptation. The amplitude of the implied motion response was significantly reduced after adaptation to motion in the same direction as the implied motion, compared to motion in the opposite direction. At 280 msec after stimulus onset, the average difference in amplitude reduction between opposite and same adapted direction was 0.5 μV on an average implied motion amplitude of 2.0 μV. These results indicate that the response to implied motion arises from direction-selective motion-sensitive neurons. This is consistent with interactions between real and implied motion processing at a neuronal level.

scholarly journals Monkey and humans exhibit similar motion-processing mechanisms

2009 ◽  
Vol 5 (6) ◽  
pp. 743-745 ◽  
Author(s):  
William Curran ◽  
Catherine Lynn
Keyword(s):  
Macaque Monkey ◽  
Human Motion ◽  
Motion Processing ◽  
Motion Adaptation ◽  
Response Characteristics ◽  
Cell Recording ◽  
Strong Resemblance ◽  
Dot Density ◽  
Processing Mechanisms ◽  
Human Primate

Single cell recording studies have resulted in a detailed understanding of motion-sensitive neurons in non-human primate visual cortex. However, it is not known to what extent response properties of motion-sensitive neurons in the non-human primate brain mirror response characteristics of motion-sensitive neurons in the human brain. Using a motion adaptation paradigm, the direction aftereffect, we show that changes in the activity of human motion-sensitive neurons to moving dot patterns that differ in dot density bear a strong resemblance to data from macaque monkey. We also show a division-like inhibition between neural populations tuned to opposite directions, which also mirrors neural-inhibitory behaviour in macaque. These findings strongly suggest that motion-sensitive neurons in human and non-human primates share common response and inhibitory characteristics.

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 Interpretation of Swedish Sign Language Using Convolutional Neural Networks and Transfer Learning

2021 ◽  
Vol 2 (3) ◽  
Author(s):  
Gustaf Halvardsson ◽  
Johanna Peterson ◽  
César Soto-Valero ◽  
Benoit Baudry
Keyword(s):  
Neural Networks ◽  
Sign Language ◽  
Transfer Learning ◽  
Convolutional Neural Networks ◽  
Web Application ◽  
Training Dataset ◽  
Motion Processing ◽  
Image Perception ◽  
Sign Languages ◽  
High Level

AbstractThe automatic interpretation of sign languages is a challenging task, as it requires the usage of high-level vision and high-level motion processing systems for providing accurate image perception. In this paper, we use Convolutional Neural Networks (CNNs) and transfer learning to make computers able to interpret signs of the Swedish Sign Language (SSL) hand alphabet. Our model consists of the implementation of a pre-trained InceptionV3 network, and the usage of the mini-batch gradient descent optimization algorithm. We rely on transfer learning during the pre-training of the model and its data. The final accuracy of the model, based on 8 study subjects and 9400 images, is 85%. Our results indicate that the usage of CNNs is a promising approach to interpret sign languages, and transfer learning can be used to achieve high testing accuracy despite using a small training dataset. Furthermore, we describe the implementation details of our model to interpret signs as a user-friendly web application.

Sign in / Sign up

Export Citation Format

Share Document