PubMed Health⌕ Search

Biomedical subjects

A Kornhuber

Publications and source records attributed to A Kornhuber.

At least 19 recordsLinked to original sources
PubMed1995

Individual differences in slow brain potentials in a guessing task.

18 healthy right-handed subjects had to predict one of two random non-equiprobable events by pressing one of two buttons with the right index finger. Each trial was preceded by a cue that increased the probability of the corresponding event in comparison to its overall probability. The Bereitschaftspotential (BP) before an action and the stimulus-preceding negativity (SPN) between the action and the event presentation were recorded. The subjects were subdivided into groups according to their tendency to follow the cue or to reject it. Cue rejection provided in the present situation a larger final gain than cue acceptance. Those subjects who used the former strategy were characterized by a local BP increase over the right parietal cortex, when a low-probable cue was presented. Their SPN amplitude was relatively small, but it increased substantially after a low-probable cue. Subjects who tended to follow the cue had a very large BP amplitude over the projection area and at vertex. Their SPN was overall large, regardless of condition. Peculiarities of the potentials recorded in these subjects are thought to relate to their desire to minimize errors.

Adolescent↗
PubMed1994

[The significance of quantitative computerized tomography in the long-term prognosis of ischemic stroke].

The courses of 118 patients who had suffered a supratentorial ischaemic infarction were observed over a mean follow-up period of 4 years. One goal of this study was to assess the prognostic value of quantitative cranial computerized tomography (CT). The infarct volume was determined using CT and expressed quantitatively as a percentage of the total brain volume. The infarct volume correlated negatively with the global outcome as estimated by the Barthel Index. It correlated positively with the occurrence of psychiatric alterations, disturbances of consciousness or alterations in the EEG. Nicotine, alcohol consumption and hyperuricaemia were the most frequent risk factors identified for men, while for women, especially those over 60, cardiac diseases were the most relevant risk factors. In looking only at the older patients, age, psychiatric alterations and cardiac disease at the time of the stroke were unfavourable prognostic factors. CT lesions in the basal ganglia were also unfavourable prognostic factors. Infarcts in the posterior cerebral artery region were seen as prognostically favourable. During the 4-year follow-up period, the reinfarction rate was 26%. Nearly 50% of the total patient population died. This group was significantly older, had more psychiatric alterations as well as multiple infarct areas in CT.

Adolescent↗
PubMed1993

A technique for diagnosing the individual patterns of innervation of the trapezius muscle prior to neck dissection.

Based on the techniques of regional anaesthesia, a method for simulating the effects of radical neck dissection on the innervation of the trapezius muscle by selectively and reversibly blocking the accessory nerve and its superficial cervical anastomoses, was developed and tested on 40 patients who were due to undergo radical neck dissection. Action potentials of the three portions of the muscle were recorded after this blockade as well as after radical neck dissection, and compared. It was found that the electromyograms were congruent in 92.5% of the cases. Four patterns of innervation were demonstrated, ranging from complete substitution of the resected or blocked nerves to a remaining muscle activity of less than 20% after blockade or radical neck dissection.

Accessory Nerve↗
PubMed1991

Endogenous event-related brain potentials and psychometric performance in children at risk for schizophrenia.

Two independent groups of high-risk children for schizophrenia and their matched control children were submitted to the following experiments: an auditory oddball paradigm registrating late event-related potentials (ERPs) and a psychometric test battery including the assessment of Wechsler Intelligence Scales, reaction times (after regular and irregular preparatory intervals), and the d2-attention test. The study was intended to clarify whether long-latency ERPs and the selected psychometric tests would contribute to reliably differentiating between these groups. The results showed significantly prolonged latencies of the P3 component of the ERPs to rare, task-relevant target stimuli in both high-risk groups compared with the controls. Similarly, the N2 latencies were delayed in both groups. By contrast, ERP patterns to frequent, nontask-relevant stimuli were very similar, with no significant differences between high-risks and normals; nor did any ERP amplitudes show significant differences. The data are interpreted as a reflection of a subtle deficit in maintaining attention and a subsequent impairment of stimulus discrimination in high-risk children. This is consistent with the psychometric findings of higher error scores in target counts and d2-test, and significantly prolonged reaction times after regular preparatory intervals (PIs) in the high-risks. The findings may hint at a vulnerability for schizophrenia in high-risk children. Given the high prevalence of the attentional dysfunctions in both high-risk groups, however, it is hypothesized their presence does not necessarily imply an unequivocal manifestation of schizophrenia.

Adolescent↗
PubMed1989

[The normal values of gamma-glutamyltransferase are falsely defined up to now: on the diagnosis of hypertension, obesity and diabetes with reference to "normal" consumption of alcohol].

In a large sample of 1379 adult patients and, in addition, in a smaller group of 223 other patients in whom a glucose tolerance test with measurement of serum insulin was carried out, an increase of blood pressure, pulse rate, relative body weight and serum insulin was found which correlated significantly with that range of gamma glutamyltransferase (GGT) values which erroneously so far is considered to be normal. The really normal range of the GGT is not up to 28 (measured at 25 degrees C), but only up to 10 U/l. Persons with GGT 9-12 U/l have a significantly higher blood pressure than persons with GGT up to 8 U/l. The relationship between blood pressure and GGT is the same in males and females although the females show a higher GGT for the same amount of alcohol consumed; in both, males and females, the steepest increase is just in the low GGT range between 9 and 25 U/l. The nature of this ethanol-effect is toxic, not caloric. Daily alcohol in "normal" ("social") amounts causes hyperinsulinemia (and thus increased sodium reabsorption in the Kidney) as well as increased catecholamine excretion. "Normal" alcohol consumption leading to hepatic steatosis as the "normal" condition of the population, has more health hazards than so for assumed. A GGT higher than 10 U/l (measured at 25 degrees C), is besides hyperinsulinemia the most sensitive test for pathologic changes of the metabolism and the cardiovascular parameters due to hepatic steatosis.(ABSTRACT TRUNCATED AT 250 WORDS)

Alcoholism↗
PubMed1989

Alcohol, smoking and body build: obesity as a result of the toxic effect of 'social' alcohol consumption.

Previous work showed that obesity in the average human male is not due to increased caloric intake. To test the hypothesis that 'social' ethanol consumption causes obesity by a hepatotoxic mechanism, the relationships between alcohol intake, cigarette smoking, serum gamma-glutamyl transpeptidase (GGT) and body build were investigated in 816 adult patients, 491 males and 325 females. A large part of the Broca index variance could be explained by hepatic damage as reflected by the GGT level. The higher the GGT, the more overweight were the subjects. Hyperinsulinemia may be the pathogenetic link; insulin is the strongest known blocker of lipolysis. Almost the total variation of obesity with GGT, however, occurred in the range of GGT up to 25 U/l, which is usually, but nevertheless erroneously, considered to be the normal range. This effect was independent of sex and age. Normal GGT is below 10 U/l, which is found on average in females aged less than 20 years. Females tolerate less alcohol than males. Although GGT is as high in females as in males around age 30, males drink about three times as much ethanol. For the same GGT the Broca index is significantly higher in females than in males. GGT generally increases with age; maximum GGT is reached in females in the age group 21-40 years (due to the change in drinking habits around 1968), declining thereafter; in males at age 50. Obesity per se is not correlated with a high GGT. In the females there are hormonal factors influencing obesity. Although in the females GGT decreases on average after age 40, obesity increases (due to the decrease in estrogens). After age 50 ethanol tolerance in males decreases: they reduce their alcohol consumption, and yet the GGT remains high. -Cigarette smoking is a factor which independently influences obesity. Although people who smoke tend also to drink more alcohol, smokers are significantly leaner than nonsmokers. On average males smoke about twice as heavily as females; this contributes to the fact that on average males are leaner than females despite their higher alcohol consumption. Due to lower consumption the influence of ethanol and smoking on body build is smaller in females than in males.

Adolescent↗
PubMed1988

Negative cortical DC shifts preceding and accompanying simultaneous and sequential finger movements.

Cortical DC shifts preceding and accompanying the execution of five different bimanual motor tasks were analysed in 20 subjects. All tasks required repetitive flexions and extensions of the two forefingers for a period of at least six seconds. The temporal and spatial structures organization varied in the different tasks: (1) Simultaneous agonistic performance (forefinger flexion on both sides), (2) simultaneous antagonistic performance (e.g. flexion of the right, extension of the left forefinger), (3) sequential agonistic performance, (4) sequential antagonistic performance, (5) uncoordinated flexions and extensions of the two forefingers. Compared to (1) and (2), conditions (3) and (4) included a temporal delay between the performance of the two forefingers; compared to (1) and (3), conditions (2) and (4) required the subjects to perform movements of opposite directions with their two forefingers. Effects of the temporal factor (T; simultaneous vs. sequential) and the spatial factor (S; agonistic vs. antagonistic) on cortical DC shifts were investigated. The voluntary initiation of each motor task was preceded by a Bereitschaftspotential (BP). The performance of the complex tasks (1-4) was accompanied by a slow negative DC potential shift (N-P). In general, the BP did not differ depending on the temporal or spatial structures of the tasks (1-4). However, amplitudes of N-P (i.e. during tasks) were influenced by the temporal factor with significantly larger amplitudes in sequential than in simultaneous tasks. This difference was not a global phenomenon in all recordings but was selectively found in the recordings over the fronto-central midline.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1988

Left frontal lobe in verbal associative learning: a slow potential study.

In the present experiment pairs of words had to be memorized. The words were either meaningful or meaningless. The experimental design compares conditions of preestablished learning (L-) with active learning (L+). The effects of these two factors, "semantic content (S)" and "learning (L)", on the slow potential shifts accompanying presentation and processing of the verbal material were tested. In the memorizing tasks, the two words were given in a fixed temporal sequence. A slow negative potential shift having a maximum in parietal leads emerged within the inter-stimulus-interval. Its amplitudes were larger in the learning tasks (L+) than in conditions of pre-established learning (L-). This difference of amplitudes may reflect different levels of attention: In L-, the second word could be anticipated, but not in the L+ tasks. After the presentation of the second item, learning tasks (L+) were characterized by a slow negative potential shift in the recordings of the left dorso-lateral frontal lobe. It is assumed that this potential shift may indicate an importance of the left frontal lobe in the elaborative encoding of verbal material.

Adult↗
PubMed1988

Cortical slow potentials in verbal and spatial tasks--the effect of material, visual hemifield and performing hand.

Fifteen right-handed students voluntarily initiated the tachistoscopic presentation of visual stimuli containing either verbal (abstract words) or spatial (stereogeometric figures) material. Subjects had to reproduce stimulus material which had been presented either in their right or their left hemifield of vision by writing or drawing, either with their right or their left hand. Material-specific effects were found during the reproduction period: amplitudes of the performance-related negative potential shifts were larger in parietal and occipital recordings (P4, O1, and O2) when drawing as compared to writing. The opposite was true in frontal and left central leads (F3, F4, and C3) where writing was associated with larger negative amplitudes than drawing. Although subjects were informed about the nature of the forthcoming stimulus before voluntarily initiating the task, material-specific effects were missing in the preparation period. The performing hand had an influence on potentials in central leads, whereas hemifield of vision had no effect on preparation- and performance-related slow potential shifts.

Adolescent↗
PubMed1988

Event-related EEG-spectra in a concept formation task.

Event-related spectra of short EEG epochs were investigated in a concept formation paradigm. In this task, subjects had to learn to transform letters into Morse codes. Related to a resting state, cognitive performance in this learning task was characterized (i) by an increased mean power density (MPD) within the Theta frequency band (theta) in recordings over the frontal lobes and (ii) by a reduced Alpha (alpha) MPD in all recording sites. The performance-related increase of the theta-MPD, as obtained in left frontolateral and frontomedial recordings, separated (i) the learning task from an appropriate control and (ii) a group of successful learners from a group which performed less efficiently. MPDs of the alpha- and the delta-(Delta) frequency band did not differ between tasks and groups. A consistent finding in the learning tasks was a temporal dissociation of performance-related alpha-attenuation between parietal and frontal recordings: in the period preceding the presentation of the informative stimuli, the alpha-rhythm is attenuated especially at parietal recordings, whereas in frontal recordings, alpha-attenuation accompanied information processing and response selection.

Adult↗
PubMed1987

Slow negative potential shifts indicating verbal cognitive learning in a concept formation task.

It is well-known clinically that patients with left frontal lesions are impaired in their verbal-cognitive learning ability. Starting from such observations, it is of particular interest whether the event-related cerebral potential shifts recorded in healthy human subjects would indicate a left frontal lobe involvement in verbal-cognitive learning tasks. In a concept formation paradigm, subjects learned by trial and error to transform letters into Morse codes. This cognitive performance was accompanied by a slow negative potential shift (SP) that in frontal recordings was lateralized towards the left hemisphere. off results show in a later stage of learning, in which the experience of the preceding trial and error learning could be integrated, an increasing slow negativity over the frontal cortex. Ss also participated in a control task with already known letter/Morse code combinations. Again, a negative potential shift occurred within the stimulus-response interval, however, it was smaller in amplitude.

Adult↗
PubMed1986

Electrophysiological evidence for right frontal lobe dominance in spatial visuomotor learning.

Slow negative potential shifts were recorded together with the error made in motor performance when two different groups of 14 students tracked visual stimuli with their right hand. Various visuomotor tasks were compared. A tracking task (T) in which subjects had to track the stimulus directly, showed no decrease of error in motor performance during the experiment. In a distorted tracking task (DT) a continuous horizontal distortion of the visual feedback had to be compensated. The additional demands of this task required visuomotor learning. Another learning condition was a mirrored-tracking task (horizontally inverted tracking, hIT), i.e. an elementary function, such as the concept of changing left and right was interposed between perception and action. In addition, subjects performed a no-tracking control task (NT) in which they started the visual stimulus without tracking it. A slow negative potential shift was associated with the visuomotor performance (TP: tracking potential). In the learning tasks (DT and hIT) this negativity was significantly enhanced over the anterior midline and in hIT frontally and precentrally over both hemispheres. Comparing hIT and T for every subject, the enhancement of the tracking potential in hIT was correlated with the success in motor learning in frontomedial and bilaterally in frontolateral recordings (r = 0.81-0.88). However, comparing DT and T, such a correlation was only found in frontomedial and right frontolateral electrodes (r = 0.5-0.61), but not at the left frontolateral electrode. These experiments are consistent with previous findings and give further neurophysiological evidence for frontal lobe activity in visuomotor learning. The hemispherical asymmetry is discussed in respect to hemispherical specialization (right frontal lobe dominance in spatial visuomotor learning).

Contingent Negative Variation↗
PubMed1985

[Headache of unknown origin: brain tumor? Indications for computer tomography].

Headache is the most frequent initial as well as the principle symptom of brain tumours. In 25 patients with brain tumours, in whom the initial symptom was headache, a further symptom of cerebral origin did not appear until after an interval of 40 months on average (median 11.5 months, 95% confidence limits of the median 4 and 60 months). Whereas tumours associated with short case-histories of headache are mostly glioblastomas, previously unrecognised tumours associated with long-standing headache are predominantly slow-growing, in the main easily operable, brain tumours. Pure headache-tumours occur predominantly in "silent" regions: in the subdominant (right) hemisphere and also in the frontal lobes as well as mid-basal in the sella area. In comparison with electroencephalography, X-ray of the skull, scintigraphy and sonography, computerised tomography is the superior non-invasive diagnostic procedure. A tumour-excluding headache does not exist. A typical migraine attack, when appearing for the first time in middle-age, can be the first indication of a brain tumour. Any reservations on the use of computerised tomography in regard to headache, when this has not been present since childhood as intermittent migraine, are, even from the point of view of cost, no longer tenable.

Adult↗
PubMed1985

Neuropsychological and neuroendocrinological disturbances associated with extracerebral cysts of the anterior and middle cranial fossa.

In ten adult patients various clinical signs and symptoms led to the diagnosis of an arachnoid cyst in the anterior and middle cranial fossa. In this study a functional relationship between these cysts and disturbances of higher cognitive processes is described. In addition, neuroendocrinological impairment were caused by arachnoid cysts reaching into the suprasellar cistern. Considering the short medical history of our patients we presumed the disturbances not to be primary, but rather secondary, caused by an expansion of the cysts' volume.

Adult↗