Factors affecting dystocia in cattle.

The paper reviews the various factors affecting dystocia in cattle. It is based mainly on the recent studies found in the literature of the subject but refers occasionally to some older papers as well. The factors are grouped into four main categories: direct factors, phenotypic factors related to calf and cow, non-genetic and genetic factors. The first group includes malpresentations and uterine torsion. The second one includes: calf birth weight, multiple calvings, perinatal mortality, cow pelvic area, cow body weight and body condition at calving, gestation length. The non-genetic factors are: cow age and parity, year and season of calving, place of calving, maintenance practises, disorders, calf sex and nutrition. Other non-genetic factors are the level of hormones in the periparturient period, in vitro production of embryos and embryo cloning. Finally, the genotypes of cow, bull and calf, inbreeding, muscular hypertrophy, selection and quantitative trait loci form the fourth group of genetic factors.

Subjective contour illusion: sex-related effect of unilateral brain damage.

The aim of the study was to investigate the effect of unilateral brain lesions on the perception of subjective contours. Brain damage resulted in a reduced ability to perceive the illusion. The effect, however, was hemisphere and sex dependent. In women an illusion decrement due to either the left or right hemisphere damage was observed, while in men only right hemisphere damage caused a decrement. No specific effect of intrahemispheric localisation of lesion was found. We conclude that mechanisms contributing to subjective contour perception are right hemisphere dependent in males whereas in females they are bilaterally represented.

Evidence for the involvement of the ventro-medial prefrontal cortex in a short-term storage of visual images.

The purpose of this study was to clarify the role of the ventro-medial prefrontal cortex in short-term visual memory. Patients with focal lesions to the right gyrus rectus were impaired on a size judgement task, which required short-term retention of laterally presented visual patterns. The impairment was most evident when the stimuli were addressed to the damaged hemisphere (left visual field presentations) and when separated by very short (50-500 ms) intervals. The findings suggest that the ventro-medial part of the orbitofrontal cortex, like the ventro-lateral part, is involved in short-term storage of icon-like representations of visual objects, and also that there exists a right-hemispheric specialization for that function. Our study presents the first direct evidence of such specific memory effects in humans using a lesion method and points to the importance of the right gyrus rectus area in maintaining the representation of stimuli after they are removed from view.

Phonological and semantic fluencies are mediated by different regions of the prefrontal cortex.

Verbal phonological and semantic fluencies were investigated in 24 patients with unilateral prefrontal lesions and 10 normal control subjects. Lesions were limited to small areas within either the dorsolateral (Brodmann's area 46/9) or ventromedial (posterior part of the gyrus rectus) cortices. In a phonological fluency task, patients with lesions to the left dorsolateral region were impaired. In semantic fluency, not only the left dorsolateral group but also the two right frontal damaged groups performed worse than the control group. In agreement with previous studies, our results show that the phonological fluency is mediated by the left dorsolateral prefrontal cortex. In contrast to this, performance on the semantic fluency task depends on a wider portion of the prefrontal cortex involving the left and right dorsolateral and the right ventromedial areas.

Evidence on hereditary occurrence of placental anastomoses in heterosexual twins in sheep.

Pedigree analysis of 22 heterosexual litters demonstrating the leukocyte chimerism (XX/XY) was carried out. The analysis revealed the familial occurrence of the chimerism in 15 litters. Eight litters were obtained from four ewes and the other seven ones were sired by three rams. Moreover, it was shown that ten chimeric litters had a common male ancestor. The coefficients of inbreeding ranged from 0.0 to 0.0625, with a mean of 0.019. These results suggest that the development of placental anastomoses in sheep is genetically controlled. A possible mode of the genetic control is discussed.

Disturbances in time limited storage sensory information after right temporal lobectomy.

Our previous study performed on subjects with no brain damage suggested that processes involved in the storage of sensory information are lateralized to the right hemisphere. The present research aimed at verifying this hypothesis by studying the effect of unilateral temporal lobe lesion on performance in a sensory information storage test. Seventeen patients who had undergone a unilateral temporal lobectomy for the relief of intractable epilepsy (8 subjects--left hemisphere damage, 9 subjects--right hemisphere damage) and 11 normal control subjects with no brain damage were tested. The subjects were presented with geometrical Vanderplas type figures exposed in pairs, each for 100 ms, one after another, with short (50 ms and 500 ms) and long (3,000 ms) interstimulus intervals (ISI). The task of the subjects was to judge whether the second stimulus was the same as, smaller or bigger than the first one. The first stimulus in each pair was exposed unilaterally, randomly in the left (LVF) or right (RVF) visual field, and the second one in the centre of the screen. In short ISI conditions the RH-damaged group performed worse than both the control group and the LH-damaged group. In long ISI conditions the RH-damaged group did not differ from the controls. On the contrary the LH-damaged group did not differ significantly from the controls in any ISI condition. The results show that temporal lobe structures are involved in time limited storage of sensory information. Moreover, they provide further evidence for the right-hemispheric locus of this storage.

Individual differences in the functional asymmetry of the human brain.

Standard models of hemispheric asymmetry assume the dychotomous division of functional competence between the two hemispheres. Individual subjects, however, often do not fit such prototypical patterns and show great variation with respect to the functional differentiation of their hemispheres. The present paper reviews the results of some of our investigations on the effect of various subject related factors on brain lateralization. Among these individual experience, gender and handedness seem to be of most significance.

Memory impairment in patients with stereotaxic lesions to the hippocampus and amygdala.

The study aimed at testing: (1) whether stereotaxic damage to the hippocampus and amygdala results in a memory deficit, (2) whether the memory functions subserved by the hippocampus are lateralized and (3) whether time limited storage of sensory information is impaired after focal hippocampal and amygdalar lesions. Seven patients with unilateral stereotaxic damage to the anterior part of hippocampus and unilateral or bilateral damage to the medial part of amygdala and 11 control subjects with no brain damage participated in the research. They were presented with memory tests that required either remembering a spatial arrangement of simultaneously presented verbal vs nonverbal stimuli or a temporal order of sequentially presented items. Moreover, a sensory information storage test was used. The results indicate that even small damage limited to the anterior part of the hippocampus and medial part of the amygdala results in a mild memory deficit. Memory impairment was not related to the side of hippocampal lesion. This suggests that memory function subserved by the hippocampus is not lateralized. Differential effects of left and right lobectomies found in previous studies were, thus, probably due to the damage to temporal cortex. The results showed, however, that sensory information storage limited to 3 s is not impaired after focal damage to the hippocampus and amygdala. A clear lateralization effect showing right hemisphere advantage in that function was found.

Hemispheric asymmetry in stimulus size evaluation.

In the present study a possible hemispheric asymmetry in size evaluation was tested. Subjects were presented with geometrical Vanderplas type figures of various sizes and shapes. The stimuli were exposed in pairs, for 100 ms, one after another. The subject's task was to decide (by pressing one of three buttons) whether the second stimulus was the same as, smaller or bigger than the first one. The first stimulus in each pair was exposed unilaterally (randomly in the left or right visual field), and the second one in the centre of the screen. Three different interstimulus intervals (ISI) were used: 50 ms, 500 ms, and 2,000 ms. The results showed shorter reaction times for left visual field presentation than for right visual field presentation at the 50 ms and 500 ms interstimulus interval. No laterality effect occurred at the 2,000 ms ISI. The results indicate a right hemisphere predominance in stimulus size evaluation. Moreover, they suggest that hemispheric asymmetry is not a stable feature of the brain but is a dynamic process that may change in the course of information processing.

Asymmetry in visual evoked potentials to gratings registered in the two hemispheres of the human brain.

The study aimed at testing, by a visual evoked potential method, the hypothesis of the hemispheric specialization in processing of high and low-spatial frequencies. Twenty four right-handed subjects (12 males and 12 females) were presented with square-wave vertical gratings of various spatial frequencies (0.67, 0.86, 1.20, 2.00, 2.40, 3.00, 3.30, 6.00 and 7.50 c/deg). Gratings were presented in nine separate blocks each containing 64 exposures. Time of exposure was 30 ms and the interstimulus interval varied from 2 to 3.5 s. VEPs were recorded with electrodes located at O1 and O2 and referred to Cz according to the 10/20 system. Amplitudes and latencies of two VEPs components (N130-150 and P200-240) were analyzed. The results showed larger amplitudes of VEPs registered in the right hemisphere of both males and females. This difference, however, was apparent in the earlier component of VEPs in females and in the later component in males. The observed hemispheric asymmetry did not depend on the spatial frequency of grating. Females demonstrated longer latencies than males for both N and P components. Our data suggest that the right hemisphere predominates in processing grating stimuli, but the dynamics of this process differ in the two sexes. The results do not support Sergent's hypothesis which postulate the right hemisphere specialization for low spatial frequencies and the left hemisphere specialization for high spatial frequencies.