Influence of geomedical factors on Guillain-Barré syndrome incidence in the region of western Slovakia.

During 5-years of follow-up we identified 58 cases of the Guillain-Barré syndrome in the Western Slovakia (approximately 1,300,000 inhabitants). The incidence of this disease fluctuated between 0.4-1.9 cases per 100,000 persons likewise mentioned in the literature. It was interesting to analyse the influence of bioclimatic conditions. We found that while higher altitude, cold and humidity increased the incidence of the GBS, warm weather had the opposite (beneficial) effect. This phenomenon might be related to a higher incidence of upper respiratory tract infections, which probably induce the autoimmune related disease. (Tab. 1, Fig. 4, Ref. 12.)

[The relation of speech to the right and left cerebral hemispheres]. / Vzt'ah reci k pravej a l'avej hemisfére mozgu.

Verbal speech functions are localized in right-handed subjects nearly exclusively and in left-handed ones mostly in the left hemisphere. Much information on these functions has been obtained by studying patients affected with spontaneous damages, as well as after hemispherectomy, after severing the corpus callosum, and during electric stimulation of the brain in neurosurgical procedures. In the presylvian region of the hemisphere dominant for speech, a region for the production and identification of speech was found, surrounded by an area for shortterm verbal memory. The predominance of the right ear in recognizing verbal stimuli, established by the dichotic test, applies to the population rather than to the individual. The substance of verbal dominance of the left hemisphere lies in the prevalence of its capacity to distinguish rapid acoustic sequences and to produce them. Observations made on deaf-mute patients with sign language have demonstrated that humans possess a genetically determined ability to develop speech, regardless the modality. Speech functions of the right hemisphere concern mostly nonverbal prosodic components of speech.

[Interaction of the cerebral hemispheres in relation to their functional asymmetry]. / Interakcia mozgových hemisfér vo vzt'ahu k ich funkcnej asymetrii.

Neurophysiological and neuropsychological methods are used to investigate the influence of one hemisphere on the activity of the other one. The findings concern contralateral motor irradiation, mirror movements and contralateral transmission of evoked potentials. At transcallosal transmission of information both quality and quantity of the information as well as the functional specification of the hemispheres is called into play. In derangements of the corpus callosum various disconnection syndromes develop, determined by the extent and localization of the lesion. Examination of patients with commissurotomy revealed a remaining partially operative interaction between the two hemispheres. The question of the relationship between conscious subjective experience and cerebral activity remains a philosophical problem. (Ref. 49).

[Left-handedness and its clinical significance]. / L'aváctvo a jeho klinický význam.

The occurrence rate of lefthanded persons is estimated to range between 4-8% in the human population, according to the criteria used. On assessing pathological lefthandedness, the role of all factors affecting the development of a lefthanded subject has to be considered. There are morphological differences between left- and righthanded subjects. The differences in neuropsychologie performance of the right and left hemisphere are less pronounced in lefthanded than in righthanded persons. A relationship between lefthandedness and the occurrence of some pathological conditions has been established. On sociobiological evaluation it appears more appropriate to consider lefthandedness as a continuous quantitative manifestation of handedness rather than a separate biological variant of man.

[Ontogenic aspects of functional asymmetry of the hemispheres]. / Ontogenetický pohl'ad na funkcnú asymetriu hemisfér.

The use of one preferred hand for differentiated activities develops gradually and stabilizes at about the age of four years. Immediately after delivery the majority of infants turn spontaneously their head to the right and are able to perceive verbal stimuli and to respond to them by turning the head to the right. The recognition of verbal stimuli involves already in infants of 1-4 months the differentiation of different phonetic categories and perhaps also of bimodal and acoustic visual categories. The development of verbal functions end sat the 9th-12th year of life. The ontogenesis of functions of the right and left hemisphere is in addition to genetic factors influenced by perinatal cerebral lesions of various extent. During transmission of verbal functions from the left to the right hemisphere a more important part is played by plasticity than by the equipotentiality of the hemispheres. The right and left hemisphere develop at a different rate continuously, however, there are sudden developmental stages in some areas of the brain.

[Relation of functional hemisphere asymmetry to motor performance]. / Vzt'ah funkcnej asymetrie hemisfér k motorike.

Motor prevalence of one upper extremity can be quantitatively expressed by the ratio of the number of performances carried out by one and the other extremity. One-sided prevalence is most markedly manifested at differentiated performances of the distal part of the extremity which require graded rapid changes of position. The competence of the left hemisphere for sequential analysis is presumably the basis of motor prevalence in right-handed persons. In performances of the proximal parts of the upper extremities involving the axial muscles, one-sided motor prevalence is less pronounced. Bilateral innervation of these parts may account for this finding. The motor preference of one lower extremity appears ontogenetically later and coincides mostly with the dominant upper extremity. Study of the relationship between reflex irritability and motor dominance failed to yield unequivocal results. The motorically dominant hemisphere is usually effective in direction dominance of conjugated lateral eye movements; under certain circumstances functional dominance of the right hemisphere is effective in right-handed persons for processing nonverbal sensoric information.

[Morphological correlates and heredity in functional asymmetry of the cerebral hemispheres]. / Morfologické koreláty a dedicnost' funkcnej nesúmernosti mozgových hemisfér.

Morphological findings which may be associated with asymmetric functions of the hemispheres have mostly appeared over the last two decades. They concern the leftsided dominance of the temporal plane and of the cytoarchitectonic region TpT, as well as of the regions which have connections with them. The posterior horn of the left lateral ventricule is usually longer and the left occipital lobe larger. The findings are associated with the leftsided location of speech functions rather than with motor dominance. Several hypotheses have been put forward attempting to explain the mode of heredity of handedness: the hypothesis of biological left--right maturation gradient, the polygenic hypothesis, further the hypothesis suggesting that one pair of genes determines the hemisphere dominant for motor and speech functions and another pair determines whether the dominant hand will be controlled by the ipsilateral or contralateral hemisphere. The hypothesis of Annette offers a plausible explanation of the heredity of handedness. It proposes that the development of a right-handed or left-handed individual is accounted for by the presence or absence of the gene which determines the dominance of the left hemisphere for speech and facilitates the development of right-handed motor dominance.

[Biochemical and electrophysiological correlations of functional asymmetry of the brain]. / Biochemické a elektrofyziologické koreláty funkcnej asymetrie mozgu.

Biochemical differences in metabolic activity between the two hemispheres are manifested by a higher level of free fatty acids in the left hemisphere. Differences in the concentration of transmitters concern higher levels of norepinephrine, dopamine, choline acetyltransferase and GABA in some regions of the left hemisphere. Lesions in homologous areas of the right and left hemisphere do not have the same effect on the biochemical activity of the brain. Amobarbital and alcohol reduce the activity of the right hemisphere. The criteria used to establish electrophysiologic differences in the activity of the two hemispheres are as follows: evaluation of the value of basic activity, suppression of alpha activity, evoked potential parameters, and the degree of negativity of slow brain potentials. Signs of higher activity of the right hemisphere were recorded at visuo-spatial performances and of higher activity of the left hemisphere at verbal performance. Extracerebrally only slight electrodermal differences were observed between the right and left side of the body.