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Notes: Summary The results of psychological examinations on 298 adult male probands with various inherited EEG variants are described. They may be summarized as follows: 1) The low-voltage (N) group scored high in intelligence tests, especially in spatial orientation. Personality scores revealed this group as ‘normal’, extravert, group-dependent, and not very energetic. 2) The borderline low-voltage (NG) group showed slight weakness in abstract thinking, short-time memory, and motor skills and a relatively strong tendency to have ‘neurotic’ complaints. Reaction time and motor skills were poor. 3) The occipital fast α-variants (BO) group performed very well in tests of abstract thinking and motor skills. 4) The monotonous α (R) group showed average performance in most intelligence scores but above-average in short-time memory and in precision under stress conditions. Personality scores indicated high spontaneous activity and toughmindedness. 5) The BG (fronto-precentral β-group) category showed very low MMPI scores, indicating little neurotic tendency. Intelligence could be above average. 6) The diffuse β (BD) group scored low in intelligence tests, especially in spatial orientation, and had a high error rate in tests measuring concentration and precision.

Notes: Summary In the first section of this paper, various research designs in human behavior genetics are compared. In this context, the commonly used concept of biometric genetics is critically evaluated from the point of view of science theory. It is contrasted with the Mendelian gene concept, which, in principle, leads to a much deeper theoretical understanding by offering clues for basic mechanisms. To explore this advantage fully, a research strategy is needed that first looks for genetic variability in a physiological parameter of possible importance for human behavior and then tries to explore the influence of this parameter on the function of the human brain and on behavior. If possible, this genetic parameter should be selected in a way that inferences as to the mechanism of its influence on behavior become feasible. Such genetic variability is provided by the hereditary variants of the normal EEG discovered by earlier work (cf. Vogel, 1970). In the following section, a research program on 298 adult healthy males, most of them soldiers, with various inherited EEG variants is described. Apart from controls with inconspicuous EEGs, this material comprises probands with the following EEG variants: low-voltage (N); low-voltage borderline (NG); monotonous α-waves (R); occipital fast α-variants (BO); fronto-precentral β-groups (BG), and diffuse β-waves (BD). In addition to an EEG examination, the probands were examined with various test methods measuring intelligence (IST; LPS; Raven); working speed and concentration (d-2; KLT); personal attitudes (MMPI; 16 PF; RKS); and sensory and motor abilities (flicker fusion; tachistoscopy; reaction time to optic, acoustic and combined stimuli; two-hand dexterity; pursuit rotor; tapping). In a supplementary twin study on 52 male adult twin pairs (26 MZ, 26 DZ), heritabilities were determined for the test scores included in the main study. For most test scores, heritabilities are relatively low; the data are compared with those from the literature. We conclude that the test methods utilized in the main study (on EEG variants) are expected to demonstrate at the most a small to moderate correlation of the EEGs with psychological phenotypes as defined by test examinations, even if a major part of the genetic variability underlying these phenotypes would be due to differences in brain physiology that could be revealed by EEG variation.

Notes: Summary Interpretation of the results from psychological examinations of 298 probands with inherited EEG variants requires (1) critical evaluation of previous literature on psychological EEG correlates, (2) knowledge of the main concepts and experimental approaches for elucidating the basic mechanisms of EEG rhythms, (3) discussion of previous attempts to link psychological variation in human populations with corresponding variation in brain function, and (4) interpretation of results from considerations at these three levels with the data from out own study. At the first level (previous psychological studies), comparison with Schmettau's study proved to be especially revealing: Her conclusions about personality correlates with high α-index and with “flat” EEGs were very similar to ours with the monotonous α-(R) and low-voltage (N) EEGs, respectively. Her EEG type with high β-index overlaps with our β-diffuse (BD) type; a tendency to ssychasthenia and low resistance to stress is less obvious in our group, but is expressed indirectly by reduced speed and accuracy in tests requiring attentiveness and persistence. The correlation between α-frequency and intelligence found in other studies was confirmed by the especially high intelligence scores of our group with occipital fast α-variants (BO). At the second and third levels of the discussion (EEG mechanisms; neurophysiological theories), the cooperation of cerebral cortex (EEG battery), thalamus (pacemaker), and ARAS (tonic arousal) is discussed, and the personality typologies of Eysenck and Claridge are mentioned. From this and other evidence, the following hypotheses are discussed: 1) The personality profiles of the R group are influenced by high activity and efficiency of the thalamic α-pacemaker(s), which leads to a high degree of modulation, selection, and amplification of afferent stimuli. 2) In the countertype of this EEG variant, the N EEG, a low modulation and amplification by the thalamic α-pacemaker is assumed. This leads to relatively low intensity of feeling and to low spontaneous activity, but to faster information processing. Combined with an increased level of tonic arousal in the ARAS, it may cause certain ‘neurotic’ complaints (our low-voltage borderline (NG) group). 3) The EEG with diffuse β-waves (BD) is caused by a high level of tonic arousal in the ARAS, which tends to disturb the thalamocortical circuit. This leads to reduced stress resistance and to impairment of intellectual functions, especially space perception. Due to limited evidence, the next two hypotheses are advanced only tentatively: 4) α-rhythm with very high frequency (16–19 c/s) leads to improvement of information processing and, hence, to high intellectual performance and motor dexterity. 5) Probands with frontoprecentral β-groups (BG) show no psychological signs of increased tonic arousal; therefore, these β-groups are caused not by increased tonic arousal of the ARAS, but by a genetic variant of a thalamic subsystem.

Notes: Summary The resting EEGs of 17 twin pairs originally traced through one neurotic co-twin (10 monozygotic and 7 dizygotic pairs aged between 18 and 63 years) have been described and compared with the neuroticism scores (Schepank, 1974) of these twins. EEG comparison according to the customary visual criteria failed to show any consistent EEG differences between monozygotic co-twins, whereas dizygotic pairs often showed EEG discordance. Computerized time-domain (interval-amplitude) analysis failed to show a higher degree of EEG discordance between neurotic MZ cotwins than between co-twins in 25 adult nonneurotic male MZ pairs (age range 18–33; mean age 22.9 years). There were no significant correlations between EEG differences and differences in the neuroticism score among ten MZ pairs traced through a neurotic co-twin. It is concluded that the individual and genetically determined EEG pattern is manifest even in the face of the long-lasting psychological alterations observed in neurotics.

Notes: Summary The problem was examined, whether those cases of postinfantile (late infantile, juvenile, and adult) amaurotic idiocy, who showed myoclonies, belong to separate genetic types, or whether myoclonies are just an occasional symptom without genetic significance. For this purpose, three new families were analyzed together with the observations from the literature. Results 1. Within the same sibships, either all siblings show myoclonies, or none of them. There are only very few exceptions from this rule, all of which can be disputed. 2. Within the late infantile, juvenile, and adult group, age of onset and other symptoms were compared between the subgroups with and without myoclonies. Among the late infantile cases, no clearcut differences were found. Among the juvenile as well as among the adult groups, however, differences between the myoclonic and non-myoclonic cases could be demonstrated. 3. The age of onset of the disease in all cases with myoclonies shows a clearcut trimodal distribution. From these three results together, the conclusion seems to be warranted that there are at least six different types of post-infantile amaurotic idiocy: late infantile, juvenile and adult types without myoclonies, and late infantile, juvenile and adult types with myoclonies. 4. In near relatives of the patients, unspecific central nervous disturbances, especially epilepsies, seem to be more frequent than in the average population. In some of these persons, we observed mild EEG anomalies. 5. the EEG of propositi with postinfantile amaurotic idiocy seems to be more variable than expected. 6. Literature reports were confirmed, according to which heterocygotes differ from normal controls by showing a certain fraction of vacuolized lymphocytes. In the discussion some problems are mentioned which need to be solved for a more thorough analysis of the postinfantile amaurotic idiocies.