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PubMed2000

Experience and visual perception in resident acquisition of laparoscopic skills.

Assess the role of experience and visual perception (VP) in resident acquisition of laparoscopic surgical skills (LSS).Thrity-nine residents (20 PGY-1s tested just before starting residency; 19 PGY 3+) completed an LSS course, including examination of course-specific knowledge before and after didactic tutorials, 10 trials of 3 dexterity drills and suturing, and 3 standardized VP tests.Mean speed increased significantly (p < 0.001) across trials for all dexterity drills and suturing. Senior residents performed suturing trials 1 to 4 significantly faster (p < 0.05) than did PGY 1's (M +/- SD averaged across trials 1 to 4: 166.5 +/- 59.9 vs 252.3 +/- 108.2 seconds, p < 0.01). Group differences on later trials were progressively smaller and nonsignificant, as were all group differences on dexterity drills. Significant correlations between VP and speed on drills ranged from (r = -0.41, p < 0.01) to (r = -0.71, p < 0.001). Visual perception did not correlate significantly with suturing speed; neither pretest nor posttest scores correlated significantly with drill or suturing speeds.Residents at all levels can significantly increase LSS performance speed to comparable levels during a brief intensive skills course. Proficiency in specific aspects of VP is directly associated with performance speed on dexterity drills, shown in previous studies to be fundamental in the development of intracorporeal suturing skill. (Curr Surg 57:368-372. Copyright 2000 by the Association of Program Directors in Surgery.)

Journal Article↗
PubMed2006

Time-resolved fMRI of mental rotation revisited--dissociating visual perception from mental rotation in female subjects.

Functional neuroimaging studies have demonstrated that mental rotation paradigms activate a network of spatially distributed cortical areas rather than a discrete brain region. Although the neuro-anatomical nodes of the rotation network are well established, their specific functional role is less well identified. It was the aim of the present study to dissociate network components involved in the visual perception of 3D cubic objects from regions involved in their mental spatial transformation. This was achieved by desynchronizing the time course of the perceptional process (i.e., stimulus duration) from the duration of the cognitive process (i.e., reaction times) and by comparing these with the temporal characteristics of the hemodynamic response functions (HRFs) in regions of interest. To minimize intersubject variability, an all-female subject group was chosen for this investigation. Time-resolved fMRI analysis revealed a significant increase in the full width at half maximum (FWHM) of the HRF with reaction times in the supplementary motor area (pre-SMA), in the bilateral premotor cortex (PMd-proper), and in the left parietal lobe (PP). The FWHM in visual system components such as the bilateral lateral occipital complex (LOC) and dorsal extrastriate visual areas (DE) was constant across trials and roughly equal to the stimulus duration. These findings suggest that visual system activation during mental rotation reflects visual perception and can be dissociated from other network components whose response characteristics indicates an involvement in the mental spatial transformation itself.

Adult↗
PubMed1995

[Is the M. Frostig perceptual training effective or not? On evaluation of the program for promoting visual perception in the German speaking areas].

Whereas the question concerning the efficacy of the Frostig program for the development of visual perception has been discussed controversely among American scientists, most German authors speak positively about the training. In this article, eight studies applying German versions of the Frostig training are shortly presented and their results summarized to find a statement about the effects of the German version of the Frostig program. The comparison of the eight studies turned out to be difficult, because the authors trained children with different handicaps. Moreover, the material was composed differently and the children were trained for different time periods. The interpretation of the positive results in the eight studies turned out more difficult because of unprecise presentation and of methodic shortcomings. The most severe shortcoming in most studies concerned the use of either no or of inappropriate control groups. Overall, the Frostig program seems to lead to improvements in different areas of performance when compared to normal school or preschool lessons. But it seems questionable if the Frostig material itself or the social interaction between trainer and child is responsible for the effects. Besides, the impact of the Frostig training on different performances may be a hint that the training not only affects visual perception, and that improved attention may be responsible for some of the effects.

Attention↗
PubMed1983

Visual exploratory activity of hemiplegic patients viewing the motor-free visual perception test.

Eye movements of adult hemiplegics (11 right- and 9 left-brain-damaged patients) and 11 nonimpaired controls were recorded as they viewed selected cards of the Motor-free Visual Perception Test. The major finding was that neither group of patients exhibited an asymmetry of visual exploration (unilateral visual neglect) as they viewed the cards. Their scanning strategies were, however, unsystematic and irregular. In addition, both groups of patients scanned the cards longer and made more errors than controls. Use of the Motor-free Visual Perception Test as an appropriate measure for the general assessment of visual-perceptual processing abilities of adult brain-damaged patients who lack severe clinical manifestations of neglect is discussed.

Brain Damage, Chronic↗
PubMed2006

Intact visual perception in memory-impaired patients with medial temporal lobe lesions.

A recent proposal that structures of the medial temporal lobe support visual perception in addition to memory challenges the long-standing idea that the ability to acquire new memories is separable from other cognitive and perceptual functions. In four experiments, we have put this proposal to a rigorous test. Six memory-impaired patients with well characterized lesions of either the hippocampal region or the hippocampal region plus additional medial temporal lobe structures were assessed on difficult tests of visual perceptual discrimination. Across all four experiments, the patients performed as well as controls. The results show that visual perception is intact in memory-impaired patients with damage to the medial temporal lobe even when perception is assessed with challenging tasks. Furthermore, the results support the principle that the ability to acquire new memories is a distinct cerebral function, dissociable from other perceptual and cognitive functions.

Aged↗
PubMed1980

[Visual perception disorders in depressive syndromes].

A wide range of psychopathological visual phenomena, part of which are traditionally considered as derealizational disturbances, are described in the structure of depressive states. Five main types of disordered visual perception are singled out, which differ by their structure and degree of correlation with the depressive affect and symptoms of depersonalization in a wide sense. The results point to certain dynamics in the described phenomena, their sensory basis. Electrooculographic studies of eye movements indicating a peculiar formation of a visual image in different forms of depressions are demonstrated.

Adolescent↗
PubMed1981

A model of visual perception.

In this paper we propose a model of visual perception in which a positive feedback mechanism can reproduce the pattern stimulus on a neurons screen. The pattern stimulus reproduction is based on informations coming from the spatial derivatives of visual pattern. This information together with the response of the feature extractors provides to the reproduction of the visual pattern as neuron screen electric activity. We simulate several input patterns and prove that the model reproduces the percept.

Computers↗
PubMed2004

Visual perception in space and time--mapping the visual field of temporal resolution.

To characterize temporal aspects of information processing in the human visual field, we studied the topographical distribution of temporal and non-temporal performance parameters in 95 normally sighted subjects. Visual field maps of double-pulse resolution thresholds (DPR) (the minimum detectable temporal gap between two light stimuli) and simple visual reaction times (RT) (measuring the speed of reaction to a light stimulus) were compared to maps of luminance thresholds determined by standard perimetry. Thus, for the first time, the topography of a visual variable without temporal constraints (perimetry) could be compared to visual variables in the temporal domain, with (RT) and without (DPR) motor reaction. The goal of the study was to obtain and to describe the pattern of co-variation of performance indicators. In all three measures, performance was best in the central visual field and dropped significantly towards the periphery. Although the correlation between DPR and RT was significant, shared variance was low, and we observed large topographical differences between these two temporal-performance variables. In contrast, DPR and perimetric thresholds correlated more substantially, and visual field maps were similar. The Gestalt of DPR maps shares characteristics of basic visual processing (e.g., light sensitivity), but it also reflects top-down influences, i.e., from spatial attention. Although the correlation between DPR and RT suggests common characteristics between these two temporal variables, the topographic distributions reveal significant differences, indicating separate underlying processing mechanisms.

Adolescent↗
PubMed1985

Visual perception dominance of fallers among community-dwelling older adults.

The authors postulated that older adult fallers show a greater tendency than older adult nonfallers to rely more on visual information sources in maintaining upright posture than on kinesthetic and vestibular cues. This paper presents descriptive statistics on 199 older adults living independently in the community. Their visual perception of the vertical and horizontal was analyzed with respect to age, sex, health status, and severity of injury as a result of a fall. The finding of significant impairments for fallers in visual perceptual abilities confirmed a trend previously established by one of the authors (Tobis). When the visual field entailed only misleading or ambiguous cues in the form of a tilted frame, fallers again showed a larger error than nonfallers in establishing the vertical and horizontal. The authors feel that this relatively greater dependence on visual sources may develop in response to impairment of feedback on posture and gait from the kinesthetic and vestibular systems as a result of age and chronic health problems. Errors in visual perception of the vertical and horizontal intercorrelated with age, sex, and a large number of medical problems. However, visual variables were more important in predicting faller status than physical characteristics.

Accidents↗
PubMedDate not supplied

[The hemispheric functional specialization of visual perception].

In this review the modern concepts on psychophysical mechanisms of hemispheric functional specialization of human visual perception are considered. The problems are discussed on three basic historical aspects: interhemispheric relations in patients with localized cerebral lesions, interhemispheric differences in the "Bisected Brain", and the functional asymmetry in the intact brain. The neuropsychological data on recognition of geometric figures, faces and objects, and also electrophysiological results on the event-related brain potentials are deliberated. Special attention is given to the own data of authors dedicated to importance role of the right hemisphere in the brain interhemispheric functional asymmetry in control subjects and alcoholics. Several problems on learning and influence of emotions on visuospatial recognition are discussed. The dichotomous approach to brain functional asymmetry are not shared, the hypothesis on intersupplementary cooperation in hemispheric specialization and interaction of the brain hemispheres are supported.

Alcoholism↗
PubMed1998

Multiple-domain dissociation between impaired visual perception and preserved mental imagery in a patient with bilateral extrastriate lesions.

A brain-damaged patient is described whose pattern of performance provides insight into both the functional mechanisms and the neural structures involved in visual mental imagery. The patient became severely agnosic, alexic, achromatopsic and prosopagnosic following bilateral brain lesions in the temporo-occipital cortex. However, her mental imagery for the same visual entities that she could not perceive was perfectly preserved. This clear-cut dissociation held across all the major domains of high-level vision: object recognition, reading, colour and face processing. Our findings, together with other reports on domain-specific dissociations and functional brain imaging studies, provide evidence to support the view that visual perception and visual mental imagery are subserved by independent functional mechanisms, which do not share the same cortical implementation. In particular, our results suggest that mental imagery abilities need not be mediated by early visual cortices.

Aged↗
PubMed1982

[Neurophysiological correlates of visual perception].

Structural organization of simple and complex receptive fields of the visual cortex was studied. The bidimensional weight function of the field determining its main properties as a filter of spatial frequencies (the space-frequency and the orientation sensitivity), was investigated. Two types of modules are discussed: the cylinders of cortical neurons whose receptive fields are oriented towards a single area of the visual field and adjusted for different spatial frequencies and orientations. One type of the modules contains neurons whose receptive fields describe the amplitude and phase of a visual signal and give the Fourier-description of a portion of picture; the second type's receptive fields describe the amplitude alone and give the power spectra. Comparison with psychophysical data suggests that the second type serves for texture description. Inhibition in the receptive field induced by frequencies which are lateral in respect to the optimal frequency and by orientations which are perpendicular in respect to the optimal orientation, reveals the mutually inhibiting influences among the module's neurons. Significance of this type of organization for visual perception is discussed.

Humans↗
PubMed1990

Structure of visual perception.

The response properties of a class of motion detectors (Reichardt detectors) are investigated extensively here. Since the outputs of the detectors, responding to an image undergoing two-dimensional rigid translation, are dependent on both the image velocity and the image intensity distribution, they are nonuniform across the entire image, even though the object is moving rigidly as a whole. To achieve perceptual "oneness" in the rigid motion, we are led to contend that visual perception must take place in a space that is non-Euclidean in nature. We then derive the affine connection and the metric of this perceptual space. The Riemann curvature tensor is identically zero, which means that the perceptual space is intrinsically flat. A geodesic in this space is composed of points of constant image intensity gradient along a certain direction. The deviation of geodesics (which are perceptually "straight") from physically straight lines may offer an explanation to the perceptual distortion of angular relationships such as the Hering illusion.

Animals↗
PubMed2003

Development of visual perception and attention, assessed by backward masking and application in children with epilepsy.

Visual masking assesses visual perception and attention; it occurs when a visual stimulus (mask) interferes with the perception of a stimulus that the participant is trying to identify (target). A backward masking study (target presented before mask) was performed on 662 children without disabilities (338 females), aged between 6 and 17 years, in order to evaluate if performance varies with age. In the masking procedure 10 letters were presented through a tachistoscope as target stimuli. Fragments of letters oriented at random ('noise') represented the mask. A slight improvement of visual performance from the beginning of school age to 9-12 years of age was found. This paper gives normative data for the most important parameters which can be used as a standardized reference for the procedure employed. We also studied 113 children with epilepsy (56 females), aged between 5 and 19 years, who attended a mainstream school and had been seizure free for at least 2 years. Children were tested just before starting antiepileptic drug withdrawal and re-tested 1 year later; they were drug free for 3 months before the second test. These children showed, during and after treatment, only slightly worse results when compared with healthy children of the same age; after therapy withdrawal, their visual performance slightly improved but this was not statistically significant.

Adolescent↗
PubMed2000

Simplicity versus likelihood in visual perception: from surprisals to precisals.

The likelihood principle states that the visual system prefers the most likely interpretation of a stimulus, whereas the simplicity principle states that it prefers the most simple interpretation. This study investigates how close these seemingly very different principles are by combining findings from classical, algorithmic, and structural information theory. It is argued that, in visual perception, the two principles are perhaps very different with respect to the viewpoint-independent aspects of perception but probably very close with respect to the viewpoint-dependent aspects which, moreover, seem decisive in everyday perception. This implies that either principle may have guided the evolution of visual systems and that the simplicity paradigm may provide perception models with the necessary quantitative specifications of the often plausible but also intuitive ideas provided by the likelihood paradigm.

Gestalt Theory↗
PubMed1997

[The visual perception of the elements of technical drawings among masking distractions in advanced and nonadvanced students in the building and architectural professions].

To investigation were submitted the particularities of the process of visual perception of technical drawings and schemes in advanced and backward pupils, who were mastering the specialties of "building and architecture", "hydroconstruction", "transport construction", "geodesy". The time was registered, which was necessary to advanced and backward pupils for unveiling the different elements in the drawing, scheme, and such attributes of the drawing as: orientation, length, curves of the lined, the boundary between them; time for identification of the specific designations, symbols, group of symbols, elements of the sketch from the simple to the complex ones. The results of the investigations revealed that in the advanced pupils the perception (unveiling) of the different elements of the technical drawing proceeded very rapidly, almost automatically. In the backward pupils this process elapsed reliably more slowly. It was demonstrated that the growing up pupils, who were distinguished with more rapid perception of the different elements of the drawing (advanced ones) more rapidly and more exactly dealt with solution of the technical tasks as compared with these, who more slowly unveiled the looked for elements (backwardness). Some other individual particularities were also established with respect to the visual perception of the elements of the technical drawing and its properties in advanced and backward pupils who were mastering the investigated professions.

Architecture↗