Neurons in monkey visual cortex detect lines defined by coherent motion of dots.

Form perception from coherent motion is an important aspect of vision. Representations of one-, two- and three-dimensional forms have been found at various stages of cortical processing using random-dot stimuli, whereas representations of biological objects like a walking human being concentrate at higher stages of processing. The perception of biological objects can be induced by sparse dot stimuli that consist of a few dots that mark the joints of the human body [G. Johansson (1973) Percept. Psychophys., 14, 201-211]. In the present study, we aimed to investigate whether neurons in early visual areas that respond to bars and edges defined by luminance contrast also signal bar-like objects from sparse dot stimuli. We studied single neurons with rows of 3-24 dots that were either collinear or scattered within a rectangular form. These dots were moved coherently on a uniform or dotted background, and human observers perceived them as rigid rods or other bar-like objects. We found neurons in the visual cortex of the awake, behaving monkey that responded to these stimuli and were sensitive to the orientation of these objects as for conventional bars or edges. Stimulus conditions that failed to induce these percepts in human observers also evoked weaker responses or none in these neurons. We found these neurons with increasing frequency in areas V1, V2 and V3/V3A. The results suggest that the visual cortex not only detects biological objects, but also lines and other bar-like objects from sparse dot stimuli, and that this function evolves at an early stage of processing.

Anatomy and physiology of a neural mechanism defining depth order and contrast polarity at illusory contours.

We studied the anatomy and physiology of neurons in monkey visual cortex, which contribute to mechanisms segregating figure and ground at contours based on information provided by occlusion cues. First, we defined the location of neurons sensitive to occluding (illusory) contours. These neurons were found most frequently in the pale cytochrome oxidase stripes of area V2 but rarely in V1. In area V2, they were found in all laminae and with similar frequencies. The few neurons recorded in area V1 concentrated in the upper laminae. Second, we studied the properties and anatomical location of neurons sensitive to occlusion cues (dark and light line-ends, corners). These neurons had end-stopped receptive fields and were found with similar frequencies in both areas. In area V1, they concentrated in the upper laminae. In area V2, they were found in all laminae and cytochrome oxidase stripes. These neurons responded to short stimuli of optimal length (bars, edges) and to stimuli terminating in their receptive field (line-ends, corners). Overall, about half of these neurons detected the direction of such terminations and about 60% were selective for certain types of termination. In summary, our results suggest that in monkey visual cortex, occlusion cues are represented in areas V1 and V2, whereas grouping mechanisms detecting occluding contours concentrate in area V2.

Backward masking of words and faces: evidence for different processing speeds in the hemispheres?

Two tachistoscopic experiments with a lateralized presentation of function words and faces were carried out to investigate the influence of temporal factors and type of masking on visual field asymmetries. Accuracy, represented by signal detection measures (d' and beta), was calculated separately for the two visual fields, for various interstimulus intervals, and for noise and pattern masking. In both experiments, d' increased with prolonged temporal delay between target and mask. In the lexical decision task, visual field interacted with mask type confirming that only in the pattern mask condition did an advantage of the right visual field emerge. In the facial decision task, however, visual field interacted with interstimulus interval, confirming that, in the left visual field, the facial information escaped the masking effect earlier than in the right visual field. In the facial task, there was a higher response criterion (beta) in the left visual field. By applying different types of masks, visual processing of lexical stimuli can be disrupted at distinct stages where perceptual asymmetries are present to a varying extent. The results of both experiments suggest that words and faces are differentially affected by masking procedures.

Sex-related engagement of the hemispheres in visuospatial processing.

Hemispheric asymmetries in visuospatial functions were investigated in women and men with a tachistoscopic task using lateralized presentation of "Necker" cubes. A lexical decision task served as control. In either of the two tasks the procedure involved a bilateral presentation of correct and distorted items and responses had to be given by means of a nonverbal decision task. The analysis of hits in the cube task showed a right visual field advantage for women and a left visual field advantage for men, but women had more false alarms in the right visual field, whereas men showed the reverse pattern again. The lexical decision task showed similar response patterns for men and women. The distinct response behavior supports the hypothesis that tasks allowing for various strategies to choose from obviously are better suited to elicit a differential engagement of the two hemispheres in women and men.

Visual field asymmetries in schematic persistence.

A modified partial-report technique was used as a tool to study hemispheric asymmetries in schematic persistence. Two types of stimuli were presented: (1) verbal stimuli consisting of function words and nonsense words, and (2) pictures of faces and nonfaces. The stimulus items were arranged bilaterally in a circular array around the fixation point and the participants' task was to decide whether the probed item was a correct or distorted version of each stimulus type. Delay time between stimulus set and marker ranged from 0 ms to 360 ms. Calculating a sensitivity measure of accuracy, distinctive visual field differences emerged which depended on the nature of the stimuli; that is, a left field advantage for facial stimuli and a right field advantage for lexical stimuli. In addition, performance decreased linearly as delay time between probe and marker increased. The present results indicate that on a level of schematic persistence perceptual hemispheric asymmetries are already strongly present.

[Effect of psychosocial risks on the maturation of EEG background activity in early childhood brain-damaged children]. / Der Einfluss psychosozialer Risiken auf die Reifung der EEG-Hintergrundaktivität bei frühkindlich hirngeschädigten Kindern.

Age-dependent changes in EEG activity were assessed in a comparison of EEG recordings taken from 102 children at the ages of 6 and 10 years. Of the 2-to-13-cycle-a-second activity recorded from the left occipital region, the fast alpha frequencies (10 to 13 cycles a second) showed a significant increase at the expense of all slower frequencies. The children were divided into two groups according to whether they had been exposed to a small or large number of biological risks; in the latter group the extent of the increase in fast alpha activity was negatively related to the number of additional psychosocial risks. This effect was even more pronounced in the group of brain-damaged children, where the smallest age-dependent shift in the EEG frequencies was seen in the group with both minimal brain damage and a high psychosocial risk factor. These data suggest that the exposure of children with minimal brain damage to multiple psychosocial risks may lead to a delay in the maturation of the brain that can be detected by neurophysiological methods.

[The diagnostic value of capillaroscopy]. / Zur diagnostischen Wertigkeit der Kapillaroskopie.

The value of capilloroscopy of the perionychium for the diagnosis of infantile brain damage and its psychic late sequealae was studied in 279 six-years-old children. By comparisons carried out within the groups of the organic brain damage criteria with respect to perinatological risks and with psychological parameters it was proved that capillaroscopy show no differential-diagnostic suitability with respects to the presence or absence of an infantile brain damage.

[Frequency and presentation of somatic brain damage criteria in risk children]. / Häufigkeit und Stellenwert somatischer Hirnschadenkriterien bei Risikokindern.

The data given in the literature about frequency and relative importance of diagnostic criteria for children with cerebral lesions show considerable differences and so do, as a consequence, diagnosing practice and epidemiological statements. This study aims at weighting the determing factors of a diagnosis and ascretining their interrelations and the associated influence on the psychic-mental development. In a total of 279 six-year-old risk and control children eight criteria regarding brain damage were recorded. The conclusive results give evidence of the influence exerted by organic conditions on the child's development and of the possibility of objectification by common methods. There is no justifiable alternative to a primarily organic basis of the diagnosis of infantile brain damage.

[Experience with the dyspraxia test (according to Lesny)]. / Erfahrungen mit dem Dyspraxie-Test (nach Lesny).

The dyspraxia test developed by LESNY was applied in a random test in 279 six-year-old risk and control children fit for infants class. All children showing failures with respect to dyspraxia requirements have on average higher pregnancy and birth risks, have on an average more symptoms of the cerebral-psychic axis syndrome, produce pathological findings more frequently in the usual method of somatic brain stem diagnostics and are regularly below the level of the control group with respect to the various performance, concentration, and behaviour parameters. Mild dyspraxia is characterised by elementary functional weakness which is etiologically caused by a brain injury and psychopathologically exerts a general development-inhibiting effect.

[Factor structure of psychopathologic symptoms in the pre-school age]. / Zur Faktorenstruktur psychopathologischer Symptome im Krippenalter.

The authors present a factor analysis of 49 psychic and physical peculiarities found in 294 children in creches, most of them high-risk children; these were perinatologically classified at the time of birth, and an examination was performed by neuropsychiatrists and a follow-up clinical and psychological examination made, at the age of 2.0-2.3 years. The following two problems were of interest: 1. Can psychosyndromes be detected in creche children and, if so; 2. Does the psychosyndrome obtained through factor analysis contain vegetative symptoms? Results - The peculiarities can be grouped as follows: (table; see text) This is the first time that the existence of a pre-school chronic psychosyndrome has been detected using a multivariate method. Its basic structure is as described by Göllnitz. A discussion follows of its position within the symptom variability in damaged and disturbed children, and of rough brain localization analogies.

[Attitude of mothers towards physical punishment as a counseling problem in small children with developmental disorders]. / Die Einstellung von Müttern zur körperlichen Bestrafung als Beratungsproblem bei entwicklungsgestörten Kleinkindern.

Using the questionnaire that has been specifically developed to obtain data on parental educational behavior, 294 mothers of 2-year-old children were studied and their attitudes towards corporal punishment correlated with characteristics and symptoms of children as well as with psychosocial factors. Low level of education and lack of domestic happiness proved to be essential conditions for acceptance of corporal punishment. Children with developmental disorders are especially endangered only because of their particular liability to disorders, but on account of the fact that they do not receive the same amount of clemency as do children who are liable to infections. Problems of maleducation should receive greater attention in the elimination of environmental dangers to healthy development of children as well as in counseling.