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Visual Tasks (visual + task)
Selected AbstractsLearning to filter out visual distractorsEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 8 2009Viktor Gál Abstract When learning to master a visual task in a cluttered natural environment, it is important to optimize the processing of task-relevant information and to efficiently filter out distractors. However, the mechanisms that suppress task-irrelevant information are not well understood. Here we show that training leads to a selective increase in motion coherence detection thresholds for task-irrelevant motion directions that interfered with the processing of task-relevant directions during training. Furthermore, using functional magnetic resonance imaging we found that training attenuated neural responses associated with the task-irrelevant direction compared with the task-relevant direction in the visual cortical areas involved in processing of visual motion. The strongest suppression of functional magnetic resonance imaging responses to task-irrelevant motion information was observed in human area MT+. These findings reveal that perceptual learning leads to the suppression and efficient filtering of task-irrelevant visual information. [source] Changes of effective connectivity between the lateral and medial parts of the prefrontal cortex during a visual taskEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 3 2003Thierry Chaminade Abstract Structural equation modelling was used to study the change of connectivity during a visual task with continuous variation of the attention load. The model was based on areas defined by the haemodynamic responses described elsewhere [Mazoyer, P., Wicker, B. & Fonlupt, P. (2002) A neural network elicited by parametric manipulation of the attention load. Neuroreport, 13, 2331,2334], including occipitotemporal, parietal, temporal and prefrontal (lateral and medial areas) cortices. We have studied stationary- (which does not depend on the attentional load) and attention-related coupling between areas. This allowed the segregation of two subsystems. The first could reflect a system performing the integration step of the visual signal and the second a system participating in response selection. The major finding is the mutual negative influence between the lateral and medial parts of the prefrontal cortex. This negative influence between these two brain regions increased with the attention load. This is interpreted as a modification of the balance between integration and decision processes that are needed for the task to be efficiently completed. [source] A Comparison of Visual Familiarization and Object-Examining Measures of Categorization in 9-Month-Old InfantsINFANCY, Issue 3 2003Barbara A. Younger Three studies were conducted to determine whether differential patterns of categorization observed in studies using visual familiarization and object-examining measures hold up as procedural confounds are eliminated. In Experiment 1, we attempted as direct a comparison as possible between visual and object-examining measures of categorization. Consistent with previous reports, 9-month-old infants distinguished a basic-level contrast (dog,horse) in the visual task, but not in the examining task. Experiment 2 was designed to reduce levels of nonexploratory activity in an examining task; 9-month-olds again failed to distinguish categories of dogs and horses. In Experiment 3, we adopted a paired-comparison test format in the object-examining task. Infants did display a novel category preference under paired testing conditions. The results suggest that the different patterns of categorization often seen in looking and touching tasks are a reflection, not of different categorization processes, but of the differential sensitivity of the tasks. [source] Binge Drinking Affects Attentional and Visual Working Memory Processing in Young University StudentsALCOHOLISM, Issue 11 2009Alberto Crego Background:, Binge Drinking (BD) typically involves heavy drinking over a short time, followed by a period of abstinence, and is common among young people, especially university students. Animal studies have demonstrated that this type of alcohol consumption causes brain damage, especially in the nonmature brain. The aim of the present study was to determine how BD affects brain functioning in male and female university students, during the performance of a visual working memory task. Methods:, Event-related potentials (ERPs) were recorded, with an extensive set of 32 scalp electrodes, in 95 first-year university students (age range 18 to 20 years), comprising 42 binge drinkers (BD) and 53 controls, in a visual "identical pairs" continuous performance task. Principal components analysis was used to identify and analyze the N2 (negative waveform with a latency around 200 to 300 ms related to attentional processes) and P3 (positive waveform with a latency around 300 to 600 ms related to working memory processes) components of the ERPs. Results:, In the matching condition of the task, the N2 component in central and parietal regions was significantly larger in the BD than in the control group. In the control group, the P3 component was larger in the matching than in the nonmatching condition in the frontal, central, and parietal regions, whereas the BD group did not show any significant differences between conditions in any region. Conclusions:, The results of this study confirm the presence of electrophysiological differences between young university student binge drinkers and controls during the execution of a visual task with a high working memory load. The larger N2 in the BD group suggests higher levels of attentional effort required by this group to perform the task adequately. The absence of any differences in the P3 component in the different conditions (matching and nonmatching stimuli) in the BD group suggests a deficiency in the electrophysiological differentiation between relevant and irrelevant information, which may reflect some impairment of working memory processes. [source] Binocular interaction and performance of visual tasksOPHTHALMIC AND PHYSIOLOGICAL OPTICS, Issue 2 2004Maria S. Justo Abstract Binocular vision implies the fusion of the right and left retinal images to perceive a single image. For this, interocular interaction is required. We measured the reaction times to carry out a visual fixation task in order to determine whether binocular interaction influences performance. Several combinations of test and distraction stimuli were monocularly and binocularly presented to one monkey and three human subjects. The overall median reaction times were 340 ms for the animal and 308, 342 and 381 for human subjects 1, 2 and 3 respectively. Reaction time was shorter when the test stimulus was presented binocularly. Moreover, we observed that the presence of a distraction stimulus increased the reaction time and that a correlated distraction stimulus had a greater influence on this increase than an uncorrelated distraction stimulus. These findings indicate that with binocular vision a more rapid performance of a visual task occurs. [source] The effects of smoking on selective attention as measured by startle reflex, skin conductance, and heart rate responses to auditory startle stimuliPSYCHOPHYSIOLOGY, Issue 1 2010Justin E. Greenstein Abstract The present study examined the effects of cigarette smoking on attentional processing by measuring nondeprived smokers' (n=39), minimally deprived smokers' (n=36), and nonsmokers' (n=34) startle eyeblink reflex, heart rate, and skin conductance responses (SCR) to acoustic startle stimuli (105 dB) during directed attention tasks. Whereas smokers demonstrated smaller startle responses than nonsmokers during a directed attention visual task, no difference in startle response magnitude emerged between the two smoking groups, nor did we observe an effect of smoking on SCR or heart rate response to the startle stimuli. Our findings suggest that smokers differ from nonsmokers in their selective attention abilities and that smoking does not enhance minimally deprived smokers' selective attention. [source] Visual P3 amplitude and self-reported psychopathic personality traits: Frontal reduction is associated with self-centered impulsivityPSYCHOPHYSIOLOGY, Issue 1 2009Scott R. Carlson Abstract Past studies have examined P3 amplitude as an index of cognitive function related to psychopathy with mixed results. Psychopathy is a heterogeneous set of dissociable traits, and no previous study has examined relationships between P3 and specific traits. A Two Process Theory (TPT) of psychopathy has recently been advanced predicting that P3 reductions are related to only one dimension. We evaluated the relationship between P3 and the two factors of the Psychopathic Personality Inventory (PPI) in 96 undergraduates who performed a visual task. One factor of the PPI, Self-Centered Impulsivity, is related to the dimension of the TPT predicted to underlie P3 reduction. Frontal amplitude reduction was uniquely and inversely related to this trait. The other PPI factor, Fearless Dominance, was associated with faster reaction times. Future work on psychopathic personality and P3 should evaluate whether relationships are unique to one personality dimension. [source] Visual deficits in developmental dyslexia: relationships between non-linguistic visual tasks and their contribution to components of readingDYSLEXIA, Issue 2 2008Manon W. Jones Abstract Developmental dyslexia is often characterized by a visual deficit, but the nature of this impairment and how it relates to reading ability is disputed (Brain 2003; 126: 841,865). In order to investigate this issue, we compared groups of adults with and without dyslexia on the Ternus, visual-search and symbols tasks. Dyslexic readers yielded more errors on the visual-search and symbols tasks compared with non-dyslexic readers. A positive correlation between visual-search and symbols task performance suggests a common mechanism shared by these tasks. Performance on the visual-search and symbols tasks also correlated with non-word reading and rapid automatized naming measures, and visual search contributed independent variance to non-word reading. The Ternus task did not discriminate reading groups nor contributed significant variance to reading measures. We consider how visual-attention processes might underlie specific component reading measures. Copyright © 2007 John Wiley & Sons, Ltd. [source] Removing Eye-movement Artifacts from the EEG during the Intracarotid Amobarbital ProcedureEPILEPSIA, Issue 3 2005Weidong Zhou Summary:,Purpose: The EEG is often recorded during the intracarotid amobarbital procedure (IAP) to help in the assessment of the spatial extent and the duration of the effect of the drug. In scalp recordings, the EEG is always heavily contaminated with eye movement artifacts as the patient actively performs visual tasks. Methods: Independent component analysis (ICA) is a new technique for blind source separation. In this study, we separated the EEG data recorded during the IAP into independent components using ICA. The EEG signal was reconstructed by excluding the components related to eye movement and eye blinks. Results: EEGs from 10 IAP tests were analyzed. The experimental results indicate that ICA is very efficient at subtracting eye-movement artifacts, while retaining the EEG slow waves and making their interpretation easier. Conclusions: ICA appears to be a generally applicable and effective method for removing ocular artifacts from EEG recordings during IAP, although slow waves and ocular artifacts share similar frequency distributions. [source] On the positive side of error processing: error-awareness positivity revisitedEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 7 2009Shani Shalgi Abstract Performance errors are indexed in the brain even if they are not consciously registered, as demonstrated by the error-related negativity (ERN or Ne) event-related potential. It has recently been shown that another response-locked potential, the error positivity (Pe), follows the Ne, but only in those trials in which the participants consciously detect making the error (,Aware Errors'). In the present study we generalize these findings to an auditory task and investigate possible caveats in the interpretation of the Pe as an index of error awareness. In an auditory Go/No-Go error-awareness task (auditory EAT) participants pressed an additional ,fix error' button after noticing that they had made an error. As in visual tasks, the Ne was similar for aware (,fixed') and unaware (,unfixed') errors, while the Pe was enhanced only for Aware Errors. Within subjects, the Ne and Pe behaved in similar fashions for auditory and visual errors. A control condition confirmed that the awareness effect was not due to the requirement to report error awareness. These results reinforce the evidence in favor of the Pe as a correlate of conscious error processing, and imply that this process is not modality-specific. Nevertheless, single-trial analysis suggested that the Pe may be a delayed P3b related to stimulus processing rather than to response monitoring. [source] Detection of animals in natural images using far peripheral visionEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 5 2001Simon J. Thorpe Abstract It is generally believed that the acuity of the peripheral visual field is too poor to allow accurate object recognition and, that to be identified, most objects need to be brought into foveal vision by using saccadic eye movements. However, most measures of form vision in the periphery have been done at eccentricities below 10° and have used relatively artificial stimuli such as letters, digits and compound Gabor patterns. Little is known about how such data would apply in the case of more naturalistic stimuli. Here humans were required to categorize briefly flashed (28 ms) unmasked photographs of natural scenes (39° high, and 26° across) on the basis of whether or not they contained an animal. The photographs appeared randomly in nine locations across virtually the entire extent of the horizontal visual field. Accuracy was 93.3% for central vision and decreased almost linearly with increasing eccentricity (89.8% at 13°, 76.1% at 44.5° and 71.2% at 57.5°). Even at the most extreme eccentricity, where the images were centred at 70.5°, subjects scored 60.5% correct. No evidence was found for hemispheric specialization. This level of performance was achieved despite the fact that the position of the image was unpredictable, ruling out the use of precued attention to target locations. The results demonstrate that even high-level visual tasks involving object vision can be performed using the relatively coarse information provided by the peripheral retina. [source] Strategic Teaching: Student Learning through Working the ProcessINTERNATIONAL JOURNAL OF ART & DESIGN EDUCATION, Issue 2 2010Nancy Spanbroek The designers of our future built environment must possess intellectual tools which will allow them to be disciplined, flexible and analytical thinkers, able to address and resolve new and complex problems. In response, an experimental and collaborative design studio was designed to inspire and build on students' knowledge and their creative thinking abilities through a series of explorative exercises and modelling. The learning experience of students undertaking this studio was enabled and guided by a collaboration of teachers experienced in both teaching and creative practice. A series of guest creative practitioners joined the studio's intensive 10-week hands-on workshop sessions within which students undertook set exercises. These creative research workshops then served to inform subsequent design development of the students' work through planning and documentation over a period of 4 weeks. Strategic teaching is central to the creative development process. The driving educational belief, as idea and practice, is that by bringing ideas to life in design, by working with full-scale three-dimensionality, students are able to cement their commitment to ,working the process', towards becoming excellent designers. This ambitious strategy enables students to work on the many different aspects of the design problem towards meeting their design outcome at the highest level of resolution and intent. Through a combination of pragmatic tasks , writing and developing design briefs , and visual tasks , evidence gathering and analysis of design through photographic, modelling and diagramming exercises , students were encouraged to think outside and beyond the ,normal' realm of design practice. [source] Users' subjective evaluation of electronic vision enhancement systemsOPHTHALMIC AND PHYSIOLOGICAL OPTICS, Issue 2 2009Louise E. Culham Abstract The aims of this study were (1) to elicit the users' responses to four electronic head-mounted devices (Jordy, Flipperport, Maxport and NuVision) and (2) to correlate users' opinion with performance. Ten patients with early onset macular disease (EOMD) and 10 with age-related macular disease (AMD) used these electronic vision enhancement systems (EVESs) for a variety of visual tasks. A questionnaire designed in-house and a modified VF-14 were used to evaluate the responses. Following initial experience of the devices in the laboratory, every patient took home two of the four devices for 1 week each. Responses were re-evaluated after this period of home loan. No single EVES stood out as the strong preference for all aspects evaluated. In the laboratory-based appraisal, Flipperport typically received the best overall ratings and highest score for image quality and ability to magnify, but after home loan there was no significant difference between devices. Comfort of device, although important, was not predictive of rating once magnification had been taken into account. For actual performance, a threshold effect was seen whereby ratings increased as reading speed improved up to 60 words per minute. Newly diagnosed patients responded most positively to EVESs, but otherwise users' opinion could not be predicted by age, gender, diagnosis or previous CCTV experience. User feedback is essential in our quest to understand the benefits and shortcoming of EVESs. Such information should help guide both prescribing and future development of low vision devices. [source] Evaluation of Melbourne Edge Test contrast sensitivity measures in the visually impairedOPHTHALMIC AND PHYSIOLOGICAL OPTICS, Issue 4 2005James S. Wolffsohn Abstract Aim:, Contrast sensitivity (CS) provides important information on visual function. This study aimed to assess differences in clinical expediency of the CS increment-matched new back-lit and original paper versions of the Melbourne Edge Test (MET) to determine the CS of the visually impaired. Methods:, The back-lit and paper MET were administered to 75 visually impaired subjects (28,97 years). Two versions of the back-lit MET acetates were used to match the CS increments with the paper-based MET. Measures of CS were repeated after 30 min and again in the presence of a focal light source directed onto the MET. Visual acuity was measured with a Bailey,Lovie chart and subjects rated how much difficulty they had with face and vehicle recognition. Results:, The back-lit MET gave a significantly higher CS than the paper-based version (14.2 ± 4.1 dB vs 11.3 ± 4.3 dB, p < 0.001). A significantly higher reading resulted with repetition of the paper-based MET (by 1.0 ± 1.7 dB, p < 0.001), but this was not evident with the back-lit MET (by 0.1 ± 1.4 dB, p = 0.53). The MET readings were increased by a focal light source, in both the back-lit (by 0.3 ± 0.81, p < 0.01) and paper-based (1.2 ± 1.7, p < 0.001) versions. CS as measured by the back-lit and paper-based versions of the MET was significantly correlated to patients' perceived ability to recognise faces (r = 0.71, r = 0.85 respectively; p < 0.001) and vehicles (r = 0.67, r = 0.82 respectively; p < 0.001), and with distance visual acuity (both r = ,0.64; p < 0.001). Conclusions:, The CS increment-matched back-lit MET gives higher CS values than the old paper-based test by approximately 3 dB and is more repeatable and less affected by external light sources. Clinically, the MET score provides information on patient difficulties with visual tasks, such as recognising faces. [source] Clinical performance of electronic, head-mounted, low-vision devicesOPHTHALMIC AND PHYSIOLOGICAL OPTICS, Issue 4 2004Louise E. Culham Abstract This study compared four electronic head-mounted devices (HMDs) (Jordy, Flipperport, Maxport and NuVision) with conventional optical low-vision aids (LVAs). The aim was to determine any performance differences for laboratory-based clinical measurements and practical visual tasks for patients with macular disease. Possible factors influencing success were explored. Ten patients with early onset macular disease (EOMD) and 10 with age-related macular disease (AMD) used the four HMDs, habitual spectacles and previously prescribed optical LVAs to complete a range of clinical measurements and everyday visual tasks. The clinical measurements were distance, intermediate and near acuities, and contrast sensitivity. The visual tasks were to read text of three sizes, to write a cheque and to identify grocery items on a shelf. Following the initial evaluation, each subject took home two randomly selected HMD devices for 2 weeks, after which performance measures were repeated. No single HMD stood out as being superior overall. Flipperport and Jordy provided significantly better distance and intermediate acuity than the previously prescribed optical LVAs but near acuity and contrast sensitivity were not consistently better with any of the HMDs. Practice at home provided some improvement in performance with HMDs, nevertheless, optical aids remained the best devices for optimum functioning for the majority of tasks. Younger patients and those with better distance acuity were more likely to benefit from HMDs, particularly when reading small print. In low vision clinics, practitioners should continue to show patients conventional optical aids and demonstrate these electronic HMDs only when appropriate for the individual patient. [source] Binocular interaction and performance of visual tasksOPHTHALMIC AND PHYSIOLOGICAL OPTICS, Issue 2 2004Maria S. Justo Abstract Binocular vision implies the fusion of the right and left retinal images to perceive a single image. For this, interocular interaction is required. We measured the reaction times to carry out a visual fixation task in order to determine whether binocular interaction influences performance. Several combinations of test and distraction stimuli were monocularly and binocularly presented to one monkey and three human subjects. The overall median reaction times were 340 ms for the animal and 308, 342 and 381 for human subjects 1, 2 and 3 respectively. Reaction time was shorter when the test stimulus was presented binocularly. Moreover, we observed that the presence of a distraction stimulus increased the reaction time and that a correlated distraction stimulus had a greater influence on this increase than an uncorrelated distraction stimulus. These findings indicate that with binocular vision a more rapid performance of a visual task occurs. [source] Degeneration and regeneration of ultraviolet cone photoreceptors during development in rainbow troutTHE JOURNAL OF COMPARATIVE NEUROLOGY, Issue 5 2006W. Ted Allison Abstract Ultraviolet-sensitive (UVS) cones disappear from the retina of salmonid fishes during a metamorphosis that prepares them for deeper/marine waters. UVS cones subsequently reappear in the retina near sexual maturation and the return migration to natal streams. Cellular mechanisms of this UVS cone ontogeny were investigated using electroretinograms, in situ hybridization, and immunohistochemistry against opsins during and after thyroid hormone (TH) treatments of rainbow trout (Oncorhynchus mykiss). Increasing TH levels led to UVS cone degeneration. Labeling demonstrated that UVS cone degeneration occurs via programmed cell death and caspase inhibitors can inhibit this death. After the cessation of TH treatment, UVS cones regenerated in the retina. Bromodeoxyuridine (BrdU) was applied after the termination of TH treatment and was detected in the nuclei of cells expressing UVS opsin. BrdU was found in UVS cones but not other cone types. The most parsimonious explanation for the data is that UVS cones degenerated and UVS cones were regenerated from intrinsic retinal progenitor cells. Regenerating UVS cones were functionally integrated such that they were able to elicit electrical responses from second-order neurons. This is the first report of cones regenerating during natural development. Both the death and regeneration of cones in retinae represent novel mechanisms for tuning visual systems to new visual tasks or environments. J. Comp. Neurol. 499:702,715, 2006. © 2006 Wiley-Liss, Inc. [source] Comparing methods of determining addition in presbyopesCLINICAL AND EXPERIMENTAL OPTOMETRY, Issue 3 2008Beatriz Antona BSc Background:, The use of plus lenses to compensate for the reduction in the range of accommodation associated with presbyopia, brings the near point of accommodation to a comfortable distance for near visual tasks. Our aim was to compare the tentative near addition determined using the most common procedures with the final addition prescribed in presbyopic patients. Methods:, Sixty-nine healthy subjects with a mean age of 51.0 years (range 40 to 60 years) were studied. Tentative near additions were determined using seven different techniques: dynamic retinoscopy, amplitude of accommodation (AA), age-expected addition, binocular fused cross-cylinder with and without myopisation, near duochrome, and balance of negative and positive relative accommodation. The power of the addition was then refined to arrive at the final addition. Results:, The mean tentative near additions were higher than the final addition for every procedure except for the fused cross-cylinder without initial myopisation and age-expected addition methods. These biases were small in clinical terms (less than 0.25 D) with the exception of the AA procedure (0.34 D). The intervals between the 95% limits of agreement differed substantially and were always higher than ±0.50 D. Conclusions:, All the techniques used displayed similar behaviour and provided a tentative addition close to the final addition. Due to the wide agreement intervals observed, the likelihood of error is high and supports the idea that any tentative addition has to be adjusted according to the particular needs of each patient. Among the methods examined here, we would recommend the age-expected procedure, as this technique produced results that correlated best with the final addition. [source] | ||||||||||||||||