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Visual Processing (visual + processing)

Distribution by Scientific Domains

Psychology	38%
Medical Sciences	34%
Life Sciences	15%
3 Other Domains	13%

Selected Abstracts

Change of Excitability in Brainstem and Cortical Visual Processing in Migraine Exhibiting Allodynia

HEADACHE, Issue 10 2006
Koichi Shibata MD
Background.,Clinical and neurophysiological manifestations of information processing associated with central sensitization are little known. Allodynic migraine (AM) can be caused by the sensitization of trigeminal neuron, but no study has reported on AM between attacks using blink reflex (BR) and pattern-reversal visual evoked potentials (PVEPs). Objective.,We explored the characteristics of AM between attacks associated with central sensitization using BR and PVEP. Methods.,We recruited 13 patients with interictal AM and 15 patients with nonallodynic migraine (NA), and 30 healthy subjects (HS). BRs were obtained using paired pulses delivered at the interstimulus interval (ISI) of 150, 300, and 500 ms. The ratio of the area in the R2 of the second to R2 of the first shock was measured for each ISI. PVEP were recorded with 2 spatial frequencies (0.5 and 4.0 cpd) and 2 low and high contrasts (29% and 98%, respectively). Amplitudes of P100 were measured. Results.,For BR, there were no significant differences in the ratio of the area of the R2 between the sides of stimulation, and the sides of headache. AM patients had less suppression of the R2 at the ISI of 150 and 300 ms when compared with the NA patients and HS. For PVEP, at 0.5, there were significant differences of amplitude between AM patients and HS, and between NA patients and HS in low and high contrast. At 4.0 cpd, there were significant differences of amplitude between AM patients and HS in low contrast, and between AM patients and HS, and NA patients and HS in high contrast. In AM patients, there was a significant difference of amplitude ratio between 0.5 and 4.0 cpd. Conclusions.,Our BR and PVEP study showed that migraine patients exhibiting allodynia may show central sensitization of brainstem trigeminal neuron and have contrast modulating dysfunction during the cortical visual processing of striate and extrastriate on visual cortex in-between attacks. [source]

Do healthy preterm children need neuropsychological follow-up?

DEVELOPMENTAL MEDICINE & CHILD NEUROLOGY, Issue 10 2010
Preschool outcomes compared with term peers
Aim, The aim of this study was to determine neuropsychological performance (possibly predictive of academic difficulties) and its relationship with cognitive development and maternal education in healthy preterm children of preschool age and age-matched comparison children born at term. Method, A total of 35 infants who were born at less than 33 weeks' gestational age and who were free from major neurosensory disability (16 males, 19 females; mean gestational age 29.4wk, SD 2.2wk; mean birthweight 1257g, SD 327g) and 50 term-born comparison children (25 males, 25 females; mean birthweight 3459g, SD 585g) were assessed at 4 years of age. Cognition was measured using the Griffiths Mental Development scales while neuropsychological abilities (language, short-term memory, visual,motor and constructive spatial abilities, and visual processing) were assessed using standardized tests. Multivariable regression analysis was used to explore the effects of preterm birth and sociodemographic factors on cognition, and to adjust neuropsychological scores for cognitive level and maternal education. Results, The mean total Griffiths score was significantly lower in preterm than in term children (97.4 vs 103.4; p<0.001). Factors associated with higher Griffiths score were maternal university education (,=6.2; 95% confidence interval [CI] 0.7,11.7) and having older siblings or a twin (,=4.0; 95% CI 0.5,7.6). At neuropsychological assessment, preterm children scored significantly lower than term comparison children in all tests except lexical production (Boston Naming Test) and visual-processing accuracy. After adjustment for cognitive level and maternal education, differences remained statistically significant for verbal fluency (p<0.05) and comprehension, short-term memory, and spatial abilities (p<0.01). Interpretation, Neuropsychological follow-up is also recommended for healthy very preterm children to identify strengths and challenges before school entry, and to plan interventions aimed at maximizing academic success. [source]

Ophthalmological, cognitive, electrophysiological and MRI assessment of visual processing in preterm children without major neuromotor impairment

DEVELOPMENTAL SCIENCE, Issue 5 2010
Michelle O'Reilly
Many studies report chronic deficits in visual processing in children born preterm. We investigated whether functional abnormalities in visual processing exist in children born preterm but without major neuromotor impairment (i.e. cerebral palsy). Twelve such children (< 33 weeks gestation or birthweight < 1000 g) without major neuromotor impairment and 12 born full-term controls were assessed at 8,12 years of age by means of ophthalmological assessment (visual acuity, colour vision, stereopsis, stereoacuity, visual fields, ocular motility, motor fusion), cognitive tests of visual-motor, visual-perceptual and visual-spatial skills and pattern-reversal visual evoked potentials (PR-VEPs). All participants also underwent magnetic resonance imaging (MRI) of the brain and neuromotor assessments. No significant differences were found between the groups on the ophthalmological, visual cognitive, neurological, neuromotor or MRI measures. The P100 component of the PR-VEP showed a significantly shorter latency in the preterm compared with the full-term participants. Whilst this P100 finding suggests that subtle abnormalities may exist at the neurophysiological level, we conclude that visual dysfunction is not systematically associated with preterm birth in the context of normal neurological status. [source]

Sensori-motor experience leads to changes in visual processing in the developing brain

DEVELOPMENTAL SCIENCE, Issue 2 2010
Karin Harman James
Since Broca's studies on language processing, cortical functional specialization has been considered to be integral to efficient neural processing. A fundamental question in cognitive neuroscience concerns the type of learning that is required for functional specialization to develop. To address this issue with respect to the development of neural specialization for letters, we used functional magnetic resonance imaging (fMRI) to compare brain activation patterns in pre-school children before and after different letter-learning conditions: a sensori-motor group practised printing letters during the learning phase, while the control group practised visual recognition. Results demonstrated an overall left-hemisphere bias for processing letters in these pre-literate participants, but, more interestingly, showed enhanced blood oxygen-level-dependent activation in the visual association cortex during letter perception only after sensori-motor (printing) learning. It is concluded that sensori-motor experience augments processing in the visual system of pre-school children. The change of activation in these neural circuits provides important evidence that ,learning-by-doing' can lay the foundation for, and potentially strengthen, the neural systems used for visual letter recognition. [source]

Effects of auditory input in individuation tasks

DEVELOPMENTAL SCIENCE, Issue 6 2008
Christopher W. Robinson
Under many conditions auditory input interferes with visual processing, especially early in development. These interference effects are often more pronounced when the auditory input is unfamiliar than when the auditory input is familiar (e.g. human speech, pre-familiarized sounds, etc.). The current study extends this research by examining how auditory input affects 8- and 14-month-olds' performance on individuation tasks. The results of the current study indicate that both unfamiliar sounds and words interfered with infants' performance on an individuation task, with cross-modal interference effects being numerically stronger for unfamiliar sounds. The effects of auditory input on a variety of lexical tasks are discussed. [source]

Neuroanatomical specificity in the expression of the immediate early gene c-fos following expression of appetitive and consummatory male sexual behaviour in Japanese quail

EUROPEAN JOURNAL OF NEUROSCIENCE, Issue 7 2006
M. Taziaux
Abstract We investigated the neural sites related to the occurrence of appetitive (ASB) and consummatory (CSB) aspects of male sexual behaviour in Japanese quail. Castrated males treated with testosterone were exposed for 5 min to one of four experimental conditions: (i) free interaction with a female (CSB group); (ii) expression of rhythmic cloacal sphincter movements in response to the visual presentation of a female (ASB-F group); (iii) or a male (ASB-M group), and (iv) handling as a control manipulation. Brains were collected 90 min after the start of behavioural tests and stained by immunocytochemistry for the FOS protein. An increase in FOS expression was observed throughout the rostro-caudal extent of the medial preoptic nucleus (POM) in CSB males, whereas the view of a female (ASB-F) induced an increased FOS expression in the rostral POM only. In the CSB group, there was also an increase in FOS expression in the bed nucleus striae terminalis, and both the CSB and ASB-F groups exhibited increased FOS expression in aspects of the ventro-lateral thalamus (VLT) related to visual processing. Moreover, both the CSB and ASB-M groups showed increased FOS expression in the lateral septum. These data provide additional support to the idea that there is a partial anatomical dissociation between structures involved in the control of both aspects of male sexual behaviour and independently provide data consistent with a previous lesion study that indicated that the rostral and caudal POM differentially control the expression of ASB and CSB in quail. [source]

Change of Excitability in Brainstem and Cortical Visual Processing in Migraine Exhibiting Allodynia

Brain mechanisms of involuntary visuospatial attention: An event-related potential study

HUMAN BRAIN MAPPING, Issue 4 2005
Shimin Fu
Abstract The brain mechanisms mediating visuospatial attention were investigated by recording event-related potentials (ERPs) during a line-orientation discrimination task. Nonpredictive peripheral cues were used to direct participant's attention involuntarily to a spatial location. The earliest attentional modulation was observed in the P1 component (peak latency about 130 ms), with the valid trials eliciting larger P1 than invalid trials. Moreover, the attentional modulations on both the amplitude and latency of the P1 and N1 components had a different pattern as compared to previous studies with voluntary attention tasks. In contrast, the earliest visual ERP component, C1 (peak latency about 80 ms), was not modulated by attention. Low-resolution brain electromagnetic tomography (LORETA) showed that the earliest attentional modulation occurred in extrastriate cortex (middle occipital gyrus, BA 19) but not in the primary visual cortex. Later attention-related reactivations in the primary visual cortex were found at about 110 ms after stimulus onset. The results suggest that involuntary as well as voluntary attention modulates visual processing at the level of extrastriate cortex; however, at least some different processes are involved by involuntary attention compared to voluntary attention. In addition, the possible feedback from higher visual cortex to the primary visual cortex is faster and occurs earlier in involuntary relative to voluntary attention task. Hum Brain Mapp, 2005. © 2005 Wiley-Liss, Inc. [source]

Human cortical processing of colour and pattern

HUMAN BRAIN MAPPING, Issue 4 2001
Nicholas A. Barrett
Abstract The present study investigates human visual processing of simple two-colour patterns using a delayed match to sample paradigm with positron emission tomography (PET). This study is unique in that we specifically designed the visual stimuli to be the same for both pattern and colour recognition with all patterns being abstract shapes not easily verbally coded composed of two-colour combinations. We did this to explore those brain regions required for both colour and pattern processing and to separate those areas of activation required for one or the other. We found that both tasks activated similar occipital regions, the major difference being more extensive activation in pattern recognition. A right-sided network that involved the inferior parietal lobule, the head of the caudate nucleus, and the pulvinar nucleus of the thalamus was common to both paradigms. Pattern recognition also activated the left temporal pole and right lateral orbital gyrus, whereas colour recognition activated the left fusiform gyrus and several right frontal regions. Hum. Brain Mapping 13:213,225, 2001. © 2001 Wiley-Liss, Inc. [source]

Aspect graphs for three-dimensional object recognition machine vision systems

INTERNATIONAL JOURNAL OF INTELLIGENT SYSTEMS, Issue 1 2005
Tatiana Tambouratzis
The purpose of this research is to seek evidence for viewer-centered (especially aspect-graph-based) visual processing in the elementary task of object understanding. Two homologous, bilaterally symmetrical three-dimensional (3-D) objects have been employed that differ in that one is based on parts with flat surfaces and the other on parts with curved surfaces. The following procedure has been followed, separately for each object. In the training (saturated free inspection and manipulation) phase, a location (identical for both objects) of the object is marked with a red strip and the subjects' task is to memorize the object structure as well as the position of the strip. In the test phase, two-dimensional views of the object without the strip are presented and the subjects' task is to determine whether the previously marked location should be visible or invisible in the particular view. Findings have been found consistent with an aspect-graph-based 3-D object representation: (a) the reaction times and errors show characteristic dependencies on viewpoint; (b) a number of views (corresponding to certain aspects and aspect transitions of the aspect graph) consistently produce faster and more accurate recognition; (c) the differences in the aspect graphs of the two objects are reflected in differing patterns of reaction times and errors; furthermore; (d) the subjects impose a standard orientation on the objects, whereby a strong inversion effect is observed; and (e) performance varies in a similar way for both objects as a function of tilt. It is concluded that object understanding is viewpoint dependent, that is, based on a number of views. The characteristics of the views found to be most important for object understanding can be employed for creating efficient 3-D object recognition machine vision systems. © 2005 Wiley Periodicals, Inc. Int J Int Syst 20: 47,72, 2005. [source]

Development of a computerized assessment for visual masking

INTERNATIONAL JOURNAL OF METHODS IN PSYCHIATRIC RESEARCH, Issue 2 2002
Michael Foster Green
Abstract Visual masking provides a highly informative means of assessing the earliest stages of visual processing. This procedure is frequently used in psychopathology research, most commonly in the study of schizophrenia. Deficits in visual masking tasks appear to reflect vulnerability factors in schizophrenia, as opposed to the symptoms of the illness. Visual masking procedures are typically conducted on a tachistoscope, which limits standardization across sites, as well as the number of variables that can be examined in a testing session. Although visual masking can be administered on a computer, most methods used so far have had poor temporal resolution and yielded a limited range of variables. We describe the development of a computerized visual masking battery. This battery includes a staircase procedure to establish an individual's threshold for target detection, and a relatively dense sampling of masking intervals. It includes both forward and backward masking trials for three different masking conditions that have been used previously in experimental psychopathology (target location, target identification with high-energy mask, and target identification with low-energy mask). Copyright © 2002 Whurr Publishers Ltd. [source]

Influence of experience of treadmill exercise on visual perception while on a treadmill

JAPANESE PSYCHOLOGICAL RESEARCH, Issue 2 2010
YOSHIKO YABE
Abstract A firm linkage exists between a motor command and its expected feedback. When we are exposed to a conflict between expected and actual feedback in a new context, we form a new linkage between action and perception, which may be further strengthened by prolonged experience. In this paper, we attempt to identify whether the linkage between treadmill locomotion and visual processing in relation to optic flow is strengthened in experienced users of treadmills. Yabe and Taga (2008) showed that ambiguous apparent motions are perceived to be moving downward more frequently when the stimuli are shown in front of the observers' feet on a treadmill when walking compared with when standing. Here, their experimental data was reanalyzed in relation to the experience of using the treadmill. The result revealed that habitual treadmill exercise reduced the difference in perceived direction of visual motion between the walking and standing conditions. It should be noted that the treadmill users showed perceptual "downward" bias for both the standing and walking conditions. The results suggest that treadmill users tend to activate the habitual linkage between treadmill locomotion and perception of optic ground flow even when they are just standing on a treadmill. [source]

Auditory stimulation affects apparent motion1

JAPANESE PSYCHOLOGICAL RESEARCH, Issue 2 2006
MAKOTO ICHIKAWA
Abstract: In two experiments, we investigated how the number of auditory stimuli affected the apparent motion induced by visual stimuli. The multiple visual stimuli that induced the apparent motion on the front parallel plane, or in the depth dimension in terms of the binocular disparity cue, were accompanied by multiple auditory stimuli. Observers reported the number of visual stimuli (Experiments 1 and 2) and the displacement of the apparent motion that was defined by the distance between the first and last visual stimuli (Experiment 2). When the number of auditory stimuli was more/less than that of the visual stimuli, observers tended to perceive more/less visual stimuli and a larger/smaller displacement than when the numbers of the auditory and visual stimuli were the same, regardless of the dimension of motion. These results suggest that auditory stimulation may modify the visual processing of motion by modulating the spatiotemporal resolution and extent of the displacement. [source]

Taking Television Seriously: A Sound and Image Bite Analysis of Presidential Campaign Coverage, 1992,2004

JOURNAL OF COMMUNICATION, Issue 4 2007
Erik P. Bucy
This study updates and builds on Hallin's landmark investigation of sound-bite news by documenting the prevalence of candidate image bites, where candidates are shown but not heard (as opposed to being shown and heard), in general election news over 4 election cycles. A visual analysis of broadcast network (ABC, CBS, and NBC) news coverage of the 1992, 1996, 2000, and 2004 U.S. presidential elections finds that image bites constituted a greater percentage of total campaign coverage than sound bites, with candidates appearing in image bites significantly more than sound bites. Even as candidate sound bites continue to shrink over time, image-bite time is increasing in duration,and candidates are being presented in image bites almost twice as much as journalists. Sound bites are also found to be largely attack and issue focused. Based on these findings, we call for greater appreciation of visual processing, nonverbal communication, and voter learning from television news in the study of media and politics. Résumé Prendre la télévision au sérieux : Une analyse des clips sonores et visuels de la couverture des campagnes électorales présidentielles, 1992-2004 Cette étude met à jour et raffine l,enquête qu'avait faite Hallin sur les clips sonores d,actualités en documentant la prévalence des clips visuels des candidats, dans lesquels ceux-ci sont montrés mais non entendus (par opposition àêtre montrés et entendus), dans les bulletins d'information sur les élections générales au travers de quatre cycles électoraux. Une analyse visuelle de la couverture par les bulletins d,information des réseaux de télédiffusion (ABC, CBS et NBC) des élections présidentielles américaines de 1992, 1996, 2000 et 2004 démontre que les clips visuels ont constitué un plus grand pourcentage de la couverture électorale totale que les clips sonores, les candidats apparaissant plus fréquemment (de façon significative) dans les clips visuels que dans les clips sonores. Alors que les clips sonores des candidats ne cessent de raccourcir au fil du temps, la durée des clips visuels augmente , et les candidats sont présentés dans des clips visuels dans une proportion presque deux fois plus grande que les journalistes. L'étude démontre également que les clips sonores sont largement centrés sur les attaques et les enjeux. D'après ces résultats, nous réclamons une plus grande compréhension du traitement visuel, de la communication non verbale et de l,apprentissage que font les électeurs à partir des bulletins de nouvelles, dans l'étude des médias et de la politique. Abstract Fernsehen ernst nehmen: Eine Analyse der Sound und Bild Bites der Präsidentschaftskampagnenberichterstattung 1992-2004 Diese Untersuchung basiert auf und erweitert die zentrale Studie von Hallin zu Sound Bite Nachrichten, indem sie über 4 Wahlzyklen hinweg die Verbreitung von Kandidaten Bild Bites dokumentiert. Bild Bites sind dabei Nachrichtenteile, in denen die Kandidaten zwar sichtbar, aber nicht hörbar sind (im Gegensatz zu sichtbar und hörbar). Eine visuelle Analyse der Nachrichtenberichterstattung zu den Präsidentschaftswahlen von 1992, 1996, 2000 und 2004 auf ABC, CBS und NBC zeigte, dass Bild Bites einen größeren Anteil der Kampagnengesamtberichterstattung ausmachen als Sound Bites, und dass die Kandidaten signifikant häufiger in Bild Bites erscheinen als in Sound Bites. Auch wenn die Zahl der Sound Bites der Kandidaten über die Jahre hinweg abnahmen, nehmen die Bild Bites in diesem Zeitraum zu - und Kandidaten werden in Bild Bites fast doppelt so oft gezeigt wie Journalisten. Sound Bites konzentrieren sich inhaltlich außerdem eher auf Angriffe und Themen. Basierend auf diesen Ergebnissen, fordern wir eine Konzentration auf die Untersuchung von visueller Verarbeitung, nonverbaler Kommunikation und dem Aspekt des Lernens von Fernsehnachrichten in der Erforschung von Medien und Politik. Resumen Tomando a la Televisión Seriamente: Un Análisis de los fragmentos de Sonido e Imagen de la Cobertura de Campañas Presidenciales, 1992-2004 Este estudio actualiza y extiende la investigación pionera de Hallin sobre los fragmentos de sonidos de noticias a través de la documentación de la prevalencia de las imágenes fragmentadas de los candidatos, en las cuales los candidatos fueron mostrados pero no escuchados (en vez de ser mostrados y escuchados), en las noticias de las elecciones generales durante 4 ciclos electivos. Un análisis visual de la cobertura de noticias de las redes de televisión (ABC, CBS, y NBC) y de las elecciones presidenciales de los Estados Unidos de 1992, 1996, 2000, y 2004 encontró que los fragmentos de imágenes, más que los de los sonidos, constituían un gran porcentaje de la cobertura total de la campaña, con los candidatos apareciendo más significativamente en los fragmentos de imágenes que en los fragmentos de sonido. Aún cuando los fragmentos de sonidos de los candidatos continúan reduciéndose a través del tiempo, el tiempo del fragmento de la imagen está incrementando en duración-y los candidatos son presentados en fragmentos de imágenes casi dos veces más que los periodistas. Los fragmentos de sonido, en su mayoría, se enfocan en ataques y asuntos. Basados en estos resultados, hacemos un llamado a la apreciación del procesamiento visual, de la comunicación no-verbal, y del aprendizaje del votante por medio de las noticias televisivas en el estudio de los medios y la política. ZhaiYao Yo yak [source]

Timing of Thyroid Hormone Action in the Developing Brain: Clinical Observations and Experimental Findings

JOURNAL OF NEUROENDOCRINOLOGY, Issue 10 2004
R. T. Zoeller
Abstract The original concept of the critical period of thyroid hormone (TH) action on brain development was proposed to identify the postnatal period during which TH supplement must be provided to a child with congenital hypothyroidism to prevent mental retardation. As neuropsychological tools have become more sensitive, it has become apparent that even mild TH insufficiency in humans can produce measurable deficits in very specific neuropsychological functions, and that the specific consequences of TH deficiency depends on the precise developmental timing of the deficiency. Models of maternal hypothyroidism, hypothyroxinaemia and congential hyperthyroidism have provided these insights. If the TH deficiency occurs early in pregnancy, the offspring display problems in visual attention, visual processing (i.e. acuity and strabismus) and gross motor skills. If it occurs later in pregnancy, children are at additional risk of subnormal visual (i.e. contrast sensitivity) and visuospatial skills, as well as slower response speeds and fine motor deficits. Finally, if TH insufficiency occurs after birth, language and memory skills are most predominantly affected. Although the experimental literature lags behind clinical studies in providing a mechanistic explanation for each of these observations, recent studies confirm that the specific action of TH on brain development depends upon developmental timing, and studies informing us about molecular mechanisms of TH action are generating hypotheses concerning possible mechanisms to account for these pleiotropic actions. [source]

Functional Magnetic Resonance Imaging of Working Memory among Multiple Sclerosis Patients

JOURNAL OF NEUROIMAGING, Issue 2 2004
Lawrence H. Sweet PhD
ABSTRACT Background and Purpose. Verbal working memory (VWM) deficits have been a well-replicated finding among patients with multiple sclerosis (MS). Functional magnetic resonance imaging (FMRI) studies have described a VWM system in healthy samples; however, functional neuroimaging of this system among MS patients is just beginning to appear. Methods. Fifteen MS patients and 15 sex-, age-, education-, and IQ-matched healthy control (HC) participants completed a 2-Back VWM task as whole-brain FMRI was conducted. Results. Each group exhibited increased brain activity compared to the 0-Back control task in regions associated with the 2-Back in previous neuroimaging studies. These included Broca's area, supplementary motor area (SMA), premotor cortices (PMC), and dorsolateral prefrontal cortices (DLPFC). MS patients exhibited greater cortical activity than did HC participants in left primary motor and somatosensory cortices, PMC, DLPFC, anterior cingulate, and bilateral SMA. MS patients exhibited relatively less activation in Broca's area, bilateral cerebellum, and other regions not typically associated with the 2-Back (eg, right fusiform gyrus, left lingual gyrus, right hippocampus). Performance accuracy and reaction time did not differ between groups. Conclusions. Normal performance of a challenging VWM task among high-functioning MS patients is associated with a shift toward greater activity in regions related to sensorimotor functions and anterior attentional/executive components of the VWM system. Posterior memory storage systems appeared unaffected, while portions of the visual processing and subvocal rehearsal systems were less active. Although a shift in neural activity was noted relative toHC participants, deviation from regions normally involved in VWM function was not observed in this patient sample. [source]

Visual Learning and the Brain: Implications for Dyslexia

MIND, BRAIN, AND EDUCATION, Issue 3 2007
Matthew H. Schneps
ABSTRACT, The central and peripheral visual fields are structurally segregated in the brain and are differentiated by their anatomical and functional characteristics. While the central field appears well suited for tasks such as visual search, the periphery is optimized for rapid processing over broad regions. People vary in their abilities to make use of information in the center versus the periphery, and we propose that this bias leads to a trade-off between abilities for sequential search versus contemporaneous comparisons. The parameter of periphery-to-center ratio (PCR) describes the degree of peripheral bias, which evidence suggests is high in many people with dyslexia. That is, many dyslexics favor the peripheral visual field over the center, which results in not only search deficits but also (more surprisingly) talents for visual comparison. The PCR framework offers a coherent explanation for these seemingly contradictory observations of both deficit and talent in visual processing. The framework has potential implications for instructional support in visually intensive domains such as science and mathematics. [source]

Dimension-based attention modulates early visual processing

PSYCHOPHYSIOLOGY, Issue 5 2010
Klaus Gramann
Abstract Target selection can be based on spatial or dimensional/featural mechanisms operating in a location-independent manner. We investigated whether dimension-based attention affects processing in early visual stages. Subjects searched for a singleton target among an 8-item array, with the search display preceded by an identical cue array with a dimensionally non-predictive, but spatially predictive singleton. Reaction times (RTs) were increased for changes in the target-defining dimension but not for featural changes within a dimension. This RT effect was mirrored by modulations of the P1 and anterior transition N2 (tN2). Current density reconstructions revealed increased activity in dorsal occipital cortex and decreased activity in left frontopolar cortex owing to repeated dimensional pop-out identities. These findings strengthen dimension-based theories of visual attention by indicating dimension-, rather than feature-, specific influences within the first 110 ms of visual processing. [source]

Cognitive processes facilitated by contextual cueing: Evidence from event-related brain potentials

PSYCHOPHYSIOLOGY, Issue 3 2009
Andrea Schankin
Abstract Finding a target in repeated search displays is faster than finding the same target in novel ones (contextual cueing). It is assumed that the visual context (the arrangement of the distracting objects) is used to guide attention efficiently to the target location. Alternatively, other factors, e.g., facilitation in early visual processing or in response selection, may play a role as well. In a contextual cueing experiment, participant's electrophysiological brain activity was recorded. Participants identified the target faster and more accurately in repeatedly presented displays. In this condition, the N2pc, a component reflecting the allocation of visual-spatial attention, was enhanced, indicating that attention was allocated more efficiently to those targets. However, also response-related processes, reflected by the LRP, were facilitated, indicating that guidance of attention cannot account for the entire contextual cueing benefit. [source]

Bilateral symmetric organization of neural elements in the visual system of a coelenterate, Tripedalia cystophora (Cubozoa)

THE JOURNAL OF COMPARATIVE NEUROLOGY, Issue 3 2005
Linda Parkefelt
Abstract Cubozoans differ from other cnidarians by their body architecture and nervous system structure. In the medusa stage they possess the most advanced visual system within the phylum, located in sophisticated sensory structures, rhopalia. The rhopalium is a club-shaped structure with paired pit-shaped pigment cup eyes, paired slit-shaped pigment cup eyes, and two complex camera-type eyes: one small upper lens eye and one large lower lens eye. The medusa carries four rhopalia and visual processing and locomotor rhythm generation takes place in the rhopalia. We show here a bilaterally symmetric organization of neurons, with commissures connecting the two sides, in the rhopalium of the cubozoan Tripedalia cystophora. The fortuitous observation that a subset of neurons is strongly immunoreactive for a PCNA (proliferating cell nuclear antigen)-like epitope allowed us to analyze the organization of these neurons in detail. Distinct PCNA-immunoreactive (PCNA-ir) nuclei form six bilateral pairs that are associated with the slit eyes, pit eyes, upper lens eye, and the posterior wall of the rhopalium. Three commissures connect the clusters of the two sides and all clusters in the rhopalium have connections to the area around the base of the stalk. This neuronal system provides an anatomical substrate for integration of visual signals from the different eyes. J. Comp. Neurol. 492:251,262, 2005. © 2005 Wiley-Liss, Inc. [source]

Investigating the efficacy of concept mapping with pupils with autistic spectrum disorder

BRITISH JOURNAL OF SPECIAL EDUCATION, Issue 3 2007
Veronica Roberts
Pupils with autism often present significant challenges to teachers. They seem to have real strengths in visual processing but a cognitive style that encourages them to focus on detail rather than the overarching connections between concepts. Veronica Roberts, currently undertaking doctoral training at the Institute of Education, University of London, in order to become an educational psychologist, and Richard Joiner, senior lecturer in the Department of Psychology at the University of Bath, set out to explore these issues. In this article, they report the outcomes of a naturalistic experiment in which they investigated the utility of concept mapping as an educational strategy with pupils diagnosed with an autistic spectrum disorder (ASD). Theoretical arguments supporting the use of concept mapping with an autistic population are outlined in the paper. A tutor group of ten pupils with ASD, aged between 11 and 14 years, took part in the study. Concept mapping tasks were integrated within National Curriculum science lessons in collaboration with the school's science teacher. The study found that the increase in pupil performance in subject-specific questionnaires was nearly four times greater in the concept mapping condition than after a more conventional teaching intervention. Veronica Roberts and Richard Joiner tentatively draw out the implications of their work for staff who work with pupils with ASD and make recommendations for further research into the use of these learning strategies. [source]

Comprehensive cognitive neurological assessment in stroke

ACTA NEUROLOGICA SCANDINAVICA, Issue 3 2009
M. Hoffmann
Background,,, Cognitive syndromes (CS) after stroke may be important to measure and monitor for management and emerging therapies. Aim,,, To incorporate known behavioral neurological and neuropsychiatric syndromes into a bedside cognitive assessment in patients with stroke. Methods,,, A validated cognitive examination (comprehensive cognitive neurological test in stroke, Coconuts) was administered during the first month of stroke presentation and analyzed according to five large-scale networks for cognition and correlated with neuropsychological tests. Validity testing of the test was performed for overall sensitivity, specificity, positive predictive value and negative predictive value to stroke in comparison with MRI diagnosis of stroke as well as discriminant validity, construct validity and inter-rater reliability. Results,,, Overall the sensitivity of the Coconuts scale was 91% and specificity 35%, PPV 88% and NPV 41% vs stroke lesions using MRI. Cognitive syndrome frequencies: frontal network syndrome frequency was 908/1796 (51%), left hemisphere network syndrome frequency was 646/1796 (36%), right hemisphere network included 275/1796 (15.3%), occipitotemporal network for complex visual processing 107/1796 (6%), the hippocampal limbic network for amnesias and emotional disorders 397/1796 (22%) and miscellaneous network syndromes 481/1796 (27%). Conclusion,,, The Coconuts is a valid and practical test of a comprehensive array of known behavioral neurological and neuropsychiatric syndromes in patients with stroke. [source]

Visual hallucinations in consultation-liaison neuropsychiatry

ACTA NEUROPSYCHIATRICA, Issue 6 2007
Mark Walterfang
Background:, In consultation-liaison settings, neuropsychiatrists are commonly asked to assess patients with hallucinatory syndromes and to differentiate ,functional' from ,organic' psychotic presentations. Methods:, The occurrence and management of visual hallucinations (VH) in healthy individuals, lesion states, neurodegenerative disorders, intoxication/withdrawal states and delirium are reviewed. Results:, The presence of VH has been shown to predict a secondary rather than primary psychotic illness and an understanding of the neurobiology of the visual system , including how and where underlying neurotransmitter systems interact in visual processing and how perturbations can result in VH , allows for appropriate clinical assessment and management. [source]

Introduction on the multifaceted roles of nitric oxide in the retina

ACTA OPHTHALMOLOGICA, Issue 2009
NN OSBORNE
Multifaceted roles of nitric oxide in the retina. N.N. Osborne. Nuffield Lab of Ophthalmology, University of Oxford, Oxford, United Kingdom Nitric oxide (NO), a free radical gas with a half-life of a few seconds is implicated in various physiological and pathophysiological roles associated with the retina and its vasculature. Generated by a family of nitric oxide synthetases (NOS), NO has been shown to bind to soluble guanylyl cyclase and to mitochondrial cytochrome c oxidase to activate defined signalling cascades. Different types of NOS exist and can be activated by calcium dependent (NOS1 and NOS3) or independent (NOS2) mechanisms. Generally, NOS1 is located to neurones while NOS2 and NOS3 are in glial and endothelial cells, respectively. NO is involved in communication between different neurones, glial cells and neurones, and in the interactions of endothelial cells with pericytes and neurones. As a consequence, a reduction in the generation of endogenous NO in the healthy retina can result in vasoconstriction; the consequences of such an affect on the retina and alterations in visual processing may alter the photoreceptor transduction mechanism and communication between retinal cells. The binding of NO to mitochondrial cytochrome c oxidase to effectively compete with oxygen has been suggested be involved in a number of processes. NO-elicited events act as triggers by which mitochondrial signal transduction cascades become involved in the induction of cellular defence mechanisms and adaptive responses. Moreover, the effect of NO on the electron transport chain might lead to mitochondrial dysfunction and pathology. NO clearly has a multifaceted role in the healthy and unhealthy retina. [source]