Speed Of Visual Perception Research Articles

Acute alcohol exposure impairs neural representation of visual motion speed in the visual cortex area posteromedial lateral suprasylvian cortex of cats.

Psychophysical and behavioral studies have demonstrated that perception of motion can be impaired by acute alcohol exposure. The neural activities of posteromedial lateral suprasylvian cortex (PMLS) of cats are directly linked to the perception of visual motion speed. To date, there have been no studies on the effects of acute alcohol exposure in vivo upon the representation of speed in PMLS neurons. Alcohol was administered intravenously as a 20% (v/v) saline solution via a syringe at a dose levels of 0.5, 1, or 2g/kg to generate a series of blood alcohol concentrations. Using extracellular single-unit recording technique, we recorded the speed-tuning properties of PMLS neurons that responded to random-dot patterns before and after alcohol administration, and simultaneously monitored the concentration of ethanol by detecting the breath alcohol concentration using a breath analyzer. After acute alcohol treatment, PMLS cells preferred lower speeds. A broadened speed-tuning bandwidth of PMLS cells was also observed after acute alcohol administration. Additionally, response modulation and discriminative capacity for speed of visual motion in the PMLS cells were significantly impaired after acute alcohol exposure. Concurrently, PMLS cells after acute alcohol exposure showed decreased spontaneous activity, peak responses, and signal-to-noise ratios. There is a significant functional degradation in the neural representation of visual motion speed in PMLS of cats after acute alcohol exposure. These neural changes may contribute to the alcohol-related deficits in visual motion perception observed in behavioral studies.

Evidence of Conjoint Activation of the Anterior Insular and Cingulate Cortices during Effortful Tasks.

The ability to perform effortful tasks is a topic that has received considerable interest in the research of higher functions of the human brain. Neuroimaging studies show that the anterior insular and the anterior cingulate cortices are involved in a multitude of cognitive tasks that require mental effort. In this study, we investigated brain responses to effort using cognitive tasks with task-difficulty modulations and functional magnetic resonance imaging (fMRI). We hypothesized that effortful performance involves modulation of activation in the anterior insular and the anterior cingulate cortices, and that the modulation correlates with individual performance levels. Healthy participants performed tasks probing verbal working memory capacity using the reading span task, and visual perception speed using the inspection time task. In the fMRI analysis, we focused on identifying effort-related brain activation. The results showed that working memory and inspection time performances were directly related. The bilateral anterior insular and anterior cingulate cortices showed significantly increased activation during each task with common portions that were active across both tasks. We observed increased brain activation in the right anterior insula and the anterior cingulate cortex in participants with low working memory performance. In line with the reported results, we suggest that activation in the anterior insular and cingulate cortices is consistent with the neural efficiency hypothesis (Neubauer).

Business Administration Students As Surrogates For IT Professionals Summary Of A Study

The purpose of this paper is to report a summary of the results of a study which examined the appropriateness of using business school students as surrogates for IT professionals by comparing cognitive styles, physiological characteristics, and basic demographic data among the two groups. Cognitive style refers to the way individuals think, perceive and remember information. Myers-Briggs Type Indicator (MBTI), Kolb's Learning Style Inventory (LSI), and Human Information Processing Survey (HIPS) tests were used to examine cognitive style. Physiological characteristics examined include dichotic (different ear) listening and visual perception speed, both with laterality (right/leftness). This study identifies important differences between the students and IT professionals. The results have implications for both researchers and designers of future information systems.

Video saliency incorporating spatiotemporal cues and uncertainty weighting.

We propose a novel algorithm to detect visual saliency from video signals by combining both spatial and temporal information and statistical uncertainty measures. The main novelty of the proposed method is twofold. First, separate spatial and temporal saliency maps are generated, where the computation of temporal saliency incorporates a recent psychological study of human visual speed perception. Second, the spatial and temporal saliency maps are merged into one using a spatiotemporally adaptive entropy-based uncertainty weighting approach. The spatial uncertainty weighing incorporates the characteristics of proximity and continuity of spatial saliency, while the temporal uncertainty weighting takes into account the variations of background motion and local contrast. Experimental results show that the proposed spatiotemporal uncertainty weighting algorithm significantly outperforms state-of-the-art video saliency detection models.

Understanding processing speed weaknesses among pedophilic child molesters: Response style vs. Neuropathology.

Research shows that pedophilic (PED) child molesters exhibit slower performance speed and greater performance accuracy when compared to nonpedophilic (N-PED) child molesters or other criminal and noncriminal controls. The purpose of the present study was to examine whether these differences reflect a slow/deliberate response style among PEDS (as we have previously hypothesized; Eastvold, Suchy, & Strassberg, 2011; Suchy, Whittaker, Strassberg, & Eastvold, 2009a, 2009b), or a fundamental neuropathological weakness in processing speed. Data came from a larger study examining neurocognition among sex offenders. Processing speed in three different domains (motor speed, visual-perceptual speed, and visual-motor integration) was examined in 20 phallometrically identified PEDs, 20 N-PEDs, and 20 nonsexual offenders, using both clinical (Finger Tapping, Symbol Search, Digit Symbol Coding) and experimental measures (Inspection Time Task [ITT]). The ITT assessed speed of visual-perceptual processing independent of response speed. On clinical measures, PEDs exhibited slower visual perception [F(2, 57) = 5.24, p = .008] and visual-motor integration [F(2, 57) = 5.02, p = .010] than the other groups, with no differences for simple motor speed. On the ITT, PEDs performed less accurately than the other groups [F(2, 57) = 3.95, p = .025], clearly indicating that slow processing speed cannot be explained by a deliberate response style. Group differences persisted after controlling for other potential confounds (age, estimate IQ, working memory, ethnicity, and substance use). PEDs' slower performance is due to a fundamental neurocognitive weakness, rather than a slow/deliberate response style. These results are consistent with Cantor et al.'s (2008) work identifying white matter abnormalities among PEDs and provide further support for a neurodevelopmental etiology of pedophilia.

SSIM-Motivated Rate-Distortion Optimization for Video Coding

We propose a rate-distortion optimization (RDO) scheme based on the structural similarity (SSIM) index, which was found to be a better indicator of perceived image quality than mean-squared error, but has not been fully exploited in the context of image and video coding. At the frame level, an adaptive Lagrange multiplier selection method is proposed based on a novel reduced-reference statistical SSIM estimation algorithm and a rate model that combines the side information with the entropy of the transformed residuals. At the macroblock level, the Lagrange multiplier is further adjusted based on an information theoretical approach that takes into account both the motion information content and perceptual uncertainty of visual speed perception. Finally, the mode for H.264/AVC coding is selected by the SSIM index and the adjusted Lagrange multiplier. Extensive experiments show that the proposed scheme can achieve significantly better rate-SSIM performance and provide better visual quality than conventional RDO coding schemes.

Asociación entre la realización de ejercicio e indicadores de funcionamiento físico y cognitivo. Comparativa de resultados en función de la edad

Background Gerontology research shows the importance of physical exercise for active aging. This study demonstrates the relationship between the practice of aerobic exercise, and physical fitness (muscle strength, respiratory capacity and motor speed) and cognitive performance (memory and visual-perceptual speed) and analyzes whether age is a modulating factor of this relationship. Material and methods The sample included 690 subjects with an age range of 30–85 years. The level of physical exercise was assessed using self-report form. Two sub-scales were used for the evaluation of cognitive performance: Digit Span Backwards and Digit Symbol (both are sub-scales of the Wechsler Adult Intelligence Scale - WAIS). The physical fitness was assessed using bio-behavioral measurements (strength, lung capacity, speed). To test the combined effect of exercise and age on the two variables (physical fitness and cognitive performance) two separate factorial analysis of variance were performed (procedure - general linear model: Univariate). Result The most significant result showed that scores on cognitive performance is a function of the intensity of the physical activity (F=4.8; P<0.002). With regard to physical fitness, its relationship with physical exercise is also significant (F=4.10; P<0.007) as well as the interaction between exercise and age (F=2.2; P<0.001). Conclusions The intensity in achieving aerobic exercise is associated with physical fitness and cognitive performance. Age has a specific weight in the association between exercise and physical fitness, this effect is higher in the older age groups (65–74 and 75–85 years for 30–49 and 50–64 years). These data suggest the compensatory effect of exercise on decline in old age.

Stroke and Action Slowing: Mechanisms, Determinants and Prognosis Value

Aim: The present study aimed to determine the mechanisms and determinants of stroke-related action slowing. Methods: Thirty-six stroke patients not presenting any clinical motor deficit of the preferred hand (mean post-stroke delay 11 months) were compared to matched controls on Finger Tapping test (motor speed), Visual Inspection Time test (visual perceptual speed) and Simple and Choice Reaction Time tests. Results: Patients were slower on all tests except Choice Reaction Time: Visual Inspection (p = 0.003), Finger Tapping test (p = 0.001), Simple Reaction Time (p = 0.002) tests were impaired including performance measured with the ipsi-lesional hand. This pattern and the uniform lengthening across the entire reaction time distribution both suggest that psychomotor slowing was due to slowing of perceptual and motor processes. The main determinant of action slowing was lesion location: (1) Visual Inspection Time = right inferior parietal lobulus (OR 18, 95% CI 2.9–108); (2) Finger Tapping = left frontal middle gyrus (OR 18, 95% CI 2.9–108) and lenticular nucleus (OR 59, 95% CI 1.9–1,775), and (3) Simple Reaction Time = right lenticular nucleus (OR 110, 95% CI 8–1,490) and posterior fossa (OR 55, 95% CI 3.4–890). Finally poor outcome depended on Tapping Frequency measured with the contra-lesional index (OR 0.1, 95% CI 0.02–0.5; p = 0.0005) and impairment on the Token test (OR 151, 95% CI 2.24–1136; p = 0.02). Conclusions: This study shows that stroke-related action slowing is mainly due to slowing of perceptual and motor processes. Action slowing was related to lesions of the large network. Finally Tapping Frequency is an independent predictor of outcome. This supports that action slowing is an important consequence of stroke and that it is a promising prognosis index.

Representation of environmental statistics by neural populations

Event Abstract Back to Event Representation of environmental statistics by neural populations Deep Ganguli1* and Eero P. Simoncelli2 1 NYU, Center for Neural Science, United States 2 NYU, United States The efficient coding hypothesis proposes that sensory systems have evolved so as to efficiently represent signals experienced in natural environments (Barlow, 1961). Quantitatively, this hypothesis can be expressed as the desire to maximize mutual information between environmental signals (as characterized by a prior probability density), and the response of a neural population, subject to resource constraints. Here we consider both the perceptual and physiological implications of efficient coding constrained by both the size of the population, and the average firing rate. Information is difficult to optimize for a multi-dimensional neural system, so we rely on two approximations. First, we use the Fisher bound on mutual information (Brunel et al., 1998), which can be rewritten in terms of the KL divergence between the square root of Fisher information and the prior (McDonnell, 2008). The bound becomes tighter as the signal to noise ratio of the population code increases (e.g. with a larger number of neurons and/or higher firing rates). Second, we solve for the optimum of this objective function, ignoring the normalization that would be necessary to make the root Fisher information a proper density. Under these approximations, an efficient population code should achieve a Fisher information proportional to the square of the prior, while satisfying resource constraints. Since the inverse of root Fisher information also provides a lower bound on the discriminability of stimuli (Series et al., 2009), this solution provides a direct perceptual prediction. Specifically, efficient coding implies that the inverse of perceptual discriminability should look like the prior. We tested this prediction for two different stimulus attributes: orientation, and speed. In the first case, we show that the inverse of orientation discriminability (data from Girshick et al., VSS2009) closely resembles the prior distribution of orientations we measured from natural images. In the speed case, we examined both discrimination data (Stocker et al., 2006) and the responses of a population of Macaque MT cells to stimuli of different speeds (data from Majaj et al., Cosyne2007). The latter data set was collected explicitly for the purpose of assessing the embedding of prior information in MT populations (Stocker, VSS2009). Thus, we can use the efficient coding result to make two independent predictions for the prior on speed. The first prediction is obtained by inverting the discrimination thresholds, as in the orientation case. A second prediction is obtained by computing the normalized root Fisher information of the MT population, which we accomplish by assuming independent Poisson noise and parameterized tuning curves fit to the data. Remarkably, the two predicted priors are consistent with each other and with the finding that human visual speed perception is consistent with a Bayesian observer using a prior that favors slower speeds (eg., Stocker et al. 2006). The efficient coding hypothesis allows us to establish a quantitative link between environmental statistics, neural processing, and perception. Although we have resorted to several approximations to achieve these results, we are currently exploring reformulations that can eliminate the need for such approximations while reaching similar conclusions. Conference: Computational and Systems Neuroscience 2010, Salt Lake City, UT, United States, 25 Feb - 2 Mar, 2010. Presentation Type: Poster Presentation Topic: Poster session III Citation: Ganguli D and Simoncelli EP (2010). Representation of environmental statistics by neural populations. Front. Neurosci. Conference Abstract: Computational and Systems Neuroscience 2010. doi: 10.3389/conf.fnins.2010.03.00240 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 04 Mar 2010; Published Online: 04 Mar 2010. * Correspondence: Deep Ganguli, NYU, Center for Neural Science, New York, United States, dganguli@cns.nyu.edu Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Deep Ganguli Eero P Simoncelli Google Deep Ganguli Eero P Simoncelli Google Scholar Deep Ganguli Eero P Simoncelli PubMed Deep Ganguli Eero P Simoncelli Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Flanker interference in young and older participants as reflected in event-related potentials

The present study investigates behavioural and event-related potential (ERP) differences between young and older participants in two variants of a flanker task. Flankers preceded the target by 100 ms (Experiment 1) or were presented simultaneously with the target (Experiment 2). In both experiments the response times showed an age-related slowing and a compatibility effect, which did not differ significantly across age. The older participants committed only half as many errors as the young ones. The visual ERPs revealed that the speed of visual perception was similar between groups. In addition the processing of the targets, but not of the flankers, appeared to be enhanced in the older participants. Moreover the lateralized readiness potential (LRP) started later and was larger for old vs. young participants, which was most pronounced for the incorrect LRP activation due to the flankers. The LRP amplitude effect is due to an enhanced activation over contralateral motor areas, which appears to be a general finding unrelated to the error rate. In summary, in the present study we could not find evidence for enhanced flanker interference in the performance of older compared to young participants. The reduced error rates for older participants are likely due to enhanced processing of the targets and delayed transmission of flanker information from visual to motor areas.

Video quality assessment using a statistical model of human visual speed perception

Motion is one of the most important types of information contained in natural video, but direct use of motion information in the design of video quality assessment algorithms has not been deeply investigated. Here we propose to incorporate a recent model of human visual speed perception [Nat. Neurosci. 9, 578 (2006)] and model visual perception in an information communication framework. This allows us to estimate both the motion information content and the perceptual uncertainty in video signals. Improved video quality assessment algorithms are obtained by incorporating the model as spatiotemporal weighting factors, where the weight increases with the information content and decreases with the perceptual uncertainty. Consistent improvement over existing video quality assessment algorithms is observed in our validation with the video quality experts group Phase I test data set.

Step frequency and perceived self-motion

There is a discrepancy between the ability to correctly match the gains of visual and motor speed in virtual reality (VR) when walking on solid ground and the failure of this ability when walking on a treadmill. Moreover, this discrepancy has been found to interact with effects of the structure of the visual environment. The authors used a high-fidelity treadmill VR system to reproduce the high interactivity of normal walking in wide-area VR. Under these conditions, it was found that gain matches in a richly structured near environment differ by only about 10% in treadmill VR from matches in wide-area VR and that trial-to-trial variations in step frequency predicted changes in perceived locomotor speed. Gait differences resulting from treadmill walking (which are shown not to be a product of wearing a head-mounted display), apparently lead to an overestimation of motor speed on treadmills. When the near visual environment represented an empty hallway, additional errors were present that could be accounted for by known illusions in the perception of visual speed during self-motion. A study of normal gait at different speeds measured by head-tracker is reported as evidence of other possible sources of perceptual estimates of locomotor speed in normal walking.

Noise characteristics and prior expectations in human visual speed perception

Human visual speed perception is qualitatively consistent with a Bayesian observer that optimally combines noisy measurements with a prior preference for lower speeds. Quantitative validation of this model, however, is difficult because the precise noise characteristics and prior expectations are unknown. Here, we present an augmented observer model that accounts for the variability of subjective responses in a speed discrimination task. This allowed us to infer the shape of the prior probability as well as the internal noise characteristics directly from psychophysical data. For all subjects, we found that the fitted model provides an accurate description of the data across a wide range of stimulus parameters. The inferred prior distribution shows significantly heavier tails than a Gaussian, and the amplitude of the internal noise is approximately proportional to stimulus speed and depends inversely on stimulus contrast. The framework is general and should prove applicable to other experiments and perceptual modalities.

Constraining the prior and likelihood in a Bayesian model of human visual speed perception

Constraining the prior and likelihood in a Bayesian model of human visual speed perception

Correlation between Speed Perception and Neural Activity in the Middle Temporal Visual Area

We conducted electrophysiological recording and microstimulation experiments to test the hypothesis that the middle temporal visual area (MT) plays a direct role in perception of the speed of moving visual stimuli. We trained rhesus monkeys on a speed discrimination task in which monkeys chose the faster speed of two moving random dot patterns presented simultaneously in spatially segregated apertures. In electrophysiological experiments, we analyzed the activity of speed-tuned MT neurons and multiunit clusters during the discrimination task. Neural activity was correlated with the monkeys' behavioral choices on a trial-to-trial basis (choice probability), and the correlation was predicted by the speed-tuning properties of each unit. In microstimulation experiments, we activated clusters of MT neurons with homogeneous speed-tuning properties during the same speed discrimination task. In one monkey, microstimulation biased speed judgments toward the preferred speed of the stimulated neurons. Together, evidence from these two experiments suggests that MT neurons play a direct role in the perception of visual speed. Comparison of psychometric and neurometric thresholds revealed that single and multineuronal signals were, on average, considerably less sensitive than were the monkeys perceptually, suggesting that signals must be pooled across neurons to account for performance.

Perception of Visual Speed While Moving.

During self-motion, the world normally appears stationary. In part, this may be due to reductions in visual motion signals during self-motion. In 8 experiments, the authors used magnitude estimation to characterize changes in visual speed perception as a result of biomechanical self-motion alone (treadmill walking), physical translation alone (passive transport), and both biomechanical self-motion and physical translation together (walking). Their results show that each factor alone produces subtractive reductions in visual speed but that subtraction is greatest with both factors together, approximating the sum of the 2 separately. The similarity of results for biomechanical and passive self-motion support H. B. Barlow's (1990) inhibition theory of sensory correlation as a mechanism for implementing H. Wallach's (1987) compensation for self-motion.

Perceptual lane width, wide perceptual road centre markings and driving speeds

The possibility that driving speeds could be reduced through the use of lane delineation was explored. Using a high-fidelity driving simulator, 28 experienced drivers were measured on seven two-lane rural roads with lane widths of 3.6, 3.0, or 2.5 m, and with either a standard centreline (control), a wide painted hatched road centre marking, or a wide white gravel road centre marking. Driving speeds were reduced on the narrowest lane width road, and further reduced on straight road sections that contained the centre marking with painted hatching. It was concluded that the narrow lane width increased steering workload and reduced speeds through a speed-steering workload trade-off, whilst the hatched road centre marking enhanced peripheral visual speed perception, leading to higher speed estimations and slower speeds. Therefore, narrowing the lane width below 3.0 m by using a painted hatched road centre marking should be an effective way to reduce driving speeds.

Neural models of motion integration and segmentation

A neural model is developed of how motion integration and segmentation processes compute global motion percepts. Figure-ground properties, such as occlusion, influence which motion signals determine the percept. For visible apertures, a line's extrinsic terminators do not specify true line motion. For invisible apertures, a line's intrinsic terminators create veridical feature tracking signals, which are amplified before they propagate across space and are integrated with ambiguous motion signals within line interiors. This integration process is the result of several processing stages: directional transient cells respond to image transients and input to a directional short-range filter that selectively boosts feature tracking signals. Competitive interactions further boost feature tracking signals and create speed-selective receptive fields. A long-range filter gives rise to true directional cells by pooling signals over multiple orientations and opposite contrast polarities. A distributed population code of speed tuning realizes a size–speed correlation, whereby activations of multiple spatially short-range filters of different sizes are transformed into speed-tuned cell responses. These mechanisms use transient cell responses, output thresholds that covary with filter size, and competition. The model reproduces empirically derived speed discrimination curves and simulates data showing how visual speed perception and discrimination are affected by stimulus contrast.

Evaluating driving ability after brain damage. Neuropsychological diagnosis and driving test

The study examined the validity of psychometric measures for the assessment of driving ability in brain-damaged subjects. 116 patients with brain damage mainly of vascular and traumatic origin underwent extensive neuropsychological examinations emphasizing attentional performance and visual perceptual speed and participated in a comprehensive on-road driving test. Only 58% of the patients passed the driving test. Attempts to predict the outcome of the driving test by discriminant analysis or cut-off procedures based on neuropsychological and/or other subject-related data yielded a maximum of 73% correct predictions. In view of the frequent impairment in driving ability after brain damage and in view of the failure to reliably predict driving ability from psychometric test results, it is recommended that in each case an on-road driving test is given.

Neural dynamics of motion processing and speed discrimination.

A neural network model of visual motion perception and speed discrimination is presented. The model shows how a distributed population code of speed tuning, that realizes a size-speed correlation, can be derived from the simplest mechanisms whereby activations of multiple spatially short-range filters of different size are transformed into speed-turned cell responses. These mechanisms use transient cell responses to moving stimuli, output thresholds that covary with filter size, and competition. These mechanisms are proposed to occur in the V1-->MT cortical processing stream. The model reproduces empirically derived speed discrimination curves and simulates data showing how visual speed perception and discrimination can be affected by stimulus contrast, duration, dot density and spatial frequency. Model motion mechanisms are analogous to mechanisms that have been used to model 3-D form and figure-ground perception. The model forms the front end of a larger motion processing system that has been used to simulate how global motion capture occurs, and how spatial attention is drawn to moving forms. It provides a computational foundation for an emerging neural theory of 3-D form and motion perception.