PubMed Health⌕ Search

Biomedical subjects

M Mölle

Publications and source records attributed to M Mölle.

32 records · Page 2Linked to original sources
PubMed1996

Enhanced dynamic complexity in the human EEG during creative thinking.

This study shows that divergent thinking, considered the general process underlying creative production, can be distinguished from convergent, analytical thought based on the dimensional complexity of ongoing electroencephalographic (EEG) activity. EEG complexity over the central and posterior cortex was higher while subjects solved tasks of divergent than convergent thinking, and also higher than during mental relaxation. Over the frontal cortex, EEG complexity was comparable during divergent thinking and mental relaxation, but reduced during convergent thinking. Results indicate that the basic process underlying the generation of novel ideas expresses itself in a strong increase in the EEG's complexity, reflecting higher degrees of freedom in the competitive interactions among cortical neuron assemblies. Frontocortical EEG complexity being comparable with that during mental relaxation, speaks for a loosened attentional control during creative thinking.

Adult↗
PubMed1996

Brain potential changes after intranasal vs. intravenous administration of vasopressin: evidence for a direct nose-brain pathway for peptide effects in humans.

There is evidence that intranasal application of peptides is a way to circumvent the blood-brain barrier. This led us to compare the effects of arginine-vasopressin (AVP) on event-related potentials (ERPs) in healthy men (n = 15) after intranasal and after intravenous (i.v.) administration. In a double-blind, crossover study, subjects received on three different occasions 20 IU of AVP intranasally (IN), 1.5 IU of AVP i.v., and saline solution. ERPs were recorded during the subject's performance on a auditory attention task. Plasma concentrations of vasopressin during task performance were enhanced after AVP, with the increase after i.v. administration of AVP exceeding that after AVP (p < 0.05). Intranasal administration of AVP substantially increased the P3 component of the ERP (p < 0.05). Intranasal administration of AVP substantially increased the P3 component of the ERP (< 0.01). By contrast, i.v. administration of AVP had no consistent effects on the ERP responses. In supplementary experiments as well, i.v. administration of lower doses of AVP (0.1 and 0.025 IU) did not affect the ERP. Plasma vasopressin concentrations after the 0.025 IU dose in these experiments were comparable to those after intranasal administration of 20 IU AVP. The results provide functional evidence that in the human brain effects of peptides like AVP may be facilitated after IN as compared to i.v. administration.

Administration, Intranasal↗
PubMed1996

Event-related brain potentials during identification of tachistoscopically presented pictures.

In the present study in 20 healthy subjects, event-related potentials (ERPs) were used to investigate the identification of picture stimuli. Each of 36 landscape pictures and 36 scrambled pictures was presented by a tachistoscope repeatedly until the subject made an identification response. Presentation of one picture was finished after 12 exposures. On the average, landscapes were identified after 5.8 +/- 0.4 exposures; identification responses to scrambles were always wrong and occurred after 11.8 +/- 0.1 exposures. Latencies and amplitude measures were assessed for P2, P3, N400, and the slow wave (SW). Changes in P2 across stimulus presentations did not differ between landscapes and scrambles excluding this component from being indicative for the processing of stimulus meaning. Amplitude of P3 generally declined across presentations, but increased prior to identification for landscape pictures. N400 rapidly declined across presentations of landscapes, but less rapidly for scrambles. The SW increased across stimulus presentations. This increase was more pronounced for landscape than scrambled pictures. The pattern of ERP changes can be interpreted in a framework of a stepwise inhibition of spreading activation within semantic memory with progressing picture identification.

Adult↗
PubMed1996

Sensory processing during early and late nocturnal sleep.

The present experiments in 10 healthy men compared auditory evoked potentials (AEPs) and heart rate (HR) indicators of stimulus processing during early and late phases of nocturnal stage 2 sleep. Definition of early and late sleep relied on endocrine pituitary-adrenal secretory activity which is known to be inhibited during early nocturnal sleep but sharply increases during late sleep. AEPs and HR responses were recorded to trains of 10 tone pips (1000 Hz; interstimulus interval 15 s; intertrain interval > 3 min). On one night, tone pips were presented in the first part of sleep, on the other night tone presentation took place in the second part, with the order of conditions balanced across subjects. Amplitudes of N150 and N550 components of the AEP, and of acceleratory and deceleratory HR responses, were higher during the first than second part of nocturnal sleep (P < 0.05). Moreover, habituation of P240 and N550 amplitudes was slower during the first than second part of sleep (P < 0.05). In supplementary experiments, AEP and HR responses to the same stimuli did not differ between the first and second part of the night when subjects were waking during stimulation. Results indicate a reduced inhibitory control over cortical stimulus processing during early nocturnal sleep. This diminished inhibition of cortical processing together with other concomitant changes during early sleep (such as the enhanced inhibition of pituitary-adrenal secretion) may reflect a coordinated regulatory function of sleep possibly mediated by hippocampal mechanisms.

Acoustic Stimulation↗
PubMed1996

Sleep and signs of attention during 3 months of intranasal vasopressin: a pilot study in two elderly subjects.

Prominent features of aging include a decrease of attention abilities and loss of sleep. Although acute effects of vasopressin (VP) on these functions in the elderly remained inconsistent, beneficial effects of the peptide may develop only with subchronic treatment, which so far has not been tested. This pilot study examined the changes in: i) event-related brain potentials (ERPs) during an attention task, ii) mood, and iii) nocturnal sleep in two healthy elderly subjects during a 3-month period of VP treatment (40 IU/day). The period of VP treatment was preceded and followed by 4-week periods of placebo treatment. ERPs and mood were not consistently affected by VP. However, unexpectedly, VP improved sleep by markedly enhancing nocturnal slow-wave sleep (SWS, p < 0.05). These findings indicate that effects of subchronic treatment with VP involve mechanisms different from those mediating acute effects.

Administration, Intranasal↗
PubMed1996

The angiotensin converting enzyme inhibitors fosinopril and enalapril differ in their central nervous effects in humans.

BACKGROUND: Although the antihypertensive actions of different angiotensin converting enzyme (ACE) inhibitors are comparable, they may affect central nervous activity, mood and well-being differently. Thus, central nervous actions of ACE inhibitors may represent an essential factor determining compliance with antihypertensive therapy. OBJECTIVE: To compare central nervous effects of the biochemically different ACE inhibitors fosinopril and enalapril in healthy men. METHODS: In a double-blind cross-over study, auditory event-related brain potentials and heart rate variability were assessed 6 h after oral intake of placebo, enalapril (10 mg) and fosinopril (20 mg) with the doses being equipotent with regard to systemic ACE inhibition. Plasma concentrations of noradrenaline, adrenaline, vasopressin and cortisol were determined 3 and 6 h after drug intake. Central nervous effects mediated via direct systemic hypotensive actions were avoided (although not completely ruled out) by including only subjects (n = 14) who displayed no substantial drop in blood pressure following intake of the ACE inhibitors. RESULTS: Enalapril, but not fosinopril, enhanced the N1 component and the N1-P2 amplitude of the event-related brain potential (P < 0.05). In addition, enalapril enhanced plasma noradrenaline concentrations (P < 0.05). A similar effect of fosinopril failed to reach significance. There was no clear-cut effect of ACE inhibition on heart rate variability, and also plasma concentrations of adrenaline, vasopressin and cortisol remained unaffected. CONCLUSION: The results suggest an enhancing effect of enalapril on mechanisms regulating stimulus-induced cortical arousal and central nervous sympathetic outflow. The effects diverging between enalapril and fosinopril indicate that access to human brain functions differs among the various types of ACE inhibitors.

Adult↗
PubMed1996

[Disseminated aspergillosis and mucormycosis. A case report].

This paper reports a simultaneous pulmonary infection due to Aspergillus fumigatus and Rhizomucor pusillus which evolved to disseminated aspergillosis and mucormycosis in a leukaemic and neutropenic 40-year-old woman. Both fungi were cultured ante mortem from bronchial secretion. Although high doses of intravenous amphotericin B were administered, the course of the infection was fatal. At autopsy, aspergilli were demonstrated by histology in lungs and brain, and zygomycetes were found to have invaded liver and kidneys.

Adult↗
PubMed1996

Greater efficacy of episodic than continuous growth hormone-releasing hormone (GHRH) administration in promoting slow-wave sleep (SWS).

It has been suggested that growth hormone (GH)-releasing hormone (GHRH) stimulates the surge in GH and enhances slow-wave sleep (SWS), two phenomena that characterize the beginning of nocturnal sleep. However, in human studies the effects of systemic GHRH administration on sleep were not consistent. This may reflect the differential influence of administration procedures being episodic in one of the above studies, but either a continuous infusion or a single bolus in the others. The present study in healthy volunteers compared changes in nocturnal sleep following 200 micrograms GHRH administered iv either episodically (4 boluses of 50 micrograms each at 2200, 2300, 2400, and 0100 h) or as a continuous infusion (57 micrograms/h between 2130 and 0100 h). Time spent in stage 4 of SWS on nights of episodic GHRH administration significantly exceeded that on nights of continuous GHRH administration (P < 0.01). Compared with a placebo condition, episodic administration of GHRH enhanced SWS (P < 0.01) and rapid eye movement (REM) sleep (P < 0.05) and diminished time spent in wakefulness and sleep stage 1 (P < 0.05). Effects of continuous GHRH infusion on sleep generally remained insignificant compared with placebo. Plasma GH concentrations were enhanced during both conditions of GHRH administration (P < 0.01), with the increase following episodic administration slightly exceeding that during continuous infusion (P < 0.05). The results support a greater physiological efficacy of episodic GHRH stimulation in promoting sleep.

Adult↗
PubMed1995

[Prophylaxis and therapy of fungal infections in oncology].

The observation of a considerable incidence of fungal infections in oncology patients has promoted a large number of studies both on prophylaxis and treatment in this patient group. Trials using triazoles, especially fluconazole, have shown effect in preventing fungal infections. In neutropenic patients, their role in therapy still remains less clear. Amphotericin B is the drug of choice for most life-threatening infections. With this drug, efforts concentrate upon the amelioration of side effects by sodium loading, administration in lipid emulsions or liposomes. The use of AMB as low-dose systemic prophylaxis or by inhalation needs further study.

Amphotericin B↗
PubMed1994

Scalp recorded direct current potential shifts associated with the transition to sleep in man.

Cortical direct current (DC) potentials are considered to reflect the state of cortical excitability which may change characteristically from wakefulness to sleep. The present experiments examined changes in the scalp recorded DC potential in 10 healthy humans at the transition from wakefulness to nocturnal sleep. For each subject, DC recordings obtained from Cz were evaluated for a 15 min pre-sleep onset interval and for a 20 min post-sleep onset interval, on 2 separate nights. Sleep stages were determined from standard sleep recordings. The transition from wakefulness to sleep coincided with a significant (P < 0.05) shift in the DC potential of negative polarity. Maximum negative potentials of (mean +/- S.E.M.) 500 +/- 130 microV (first night) and of 760 +/- 200 microV (second night) were reached at the end of the 20 min post-sleep onset interval. A number of possible technical and biological artifacts were controlled. It is reasonable to assume that the slow negative shift of the DC potential at the transition from wakefulness to sleep reflects increased cortical excitability. Whether the negative potential shift pertains during sleep, or is of transient nature and closely linked to the process of falling asleep, remains to be clarified.

Adolescent↗
PubMed1994

Mental comparison of visually presented two-digit numbers: a P300 study.

Comparison processes were investigated in a multiple-stimulus paradigm with a pseudo-random sequence of visually presented numbers 11 to 20. The subjects' task was to compare each current number with the preceding one and to indicate whether it was larger or smaller. ERPs were selectively averaged for the 10 number stimuli, for three functional conditions according to the information the numbers provide about the ensuing response and for the differences between consecutive numbers. P300 amplitude averaged for each number stimulus showed a U-shaped trend with largest amplitudes for the numbers 11 and 20. It was found that P300 amplitudes change with the amount of information the current number is delivering for the ensuing response. This information delivery is related to the processing in the subsequent trial, as revealed by a negative correlation between P300 in the current trial and RT in the ensuing trial. Reaction times decreased significantly with increasing difference between the current number and the preceding one. This symbolic distance effect was not found for P300 parameters. The dissociation between RT and P300 data provides evidence for the assumption that under the present experimental conditions informational transaction leading to the distance effect occur after the elicitation of P300.

Adult↗
PubMed1994

Event-related potentials indicate information extraction in a comparative judgement task.

Event-related potentials (ERPs) were recorded from normal subjects in a serial paired-comparison task with the spoken digits one to five. For each digit, the subject decided whether it was smaller or larger than the preceding one. We examined to what extent ERP components are associated with the probability information each digit provides with respect to the subsequent response. Shortest reaction time (RT) and highest accuracy was obtained for the two end terms one and five. The N1 and P2 components of the ERP were attenuated for the two end terms. Three late positivities were found: early P3, P3b, and slow wave. P3b increased in amplitude the more information the eliciting digit provided with respect to the response to the subsequent digit. Moreover, a negative correlation was found between the P3b amplitude associated with information extraction and the RTs to the subsequent digit. During comparative judgement, subjects process the relative position of a stimulus within a stimulus set to extract information about the probability of a forthcoming response, and this process is reflected in P3b amplitude.

Adult↗
PubMedDate not supplied

Adrenocorticotropin widens the focus of attention in humans. A nonliner electroencephalographic analysis.

OBJECTIVE: This study examined the effects of ACTH 4-10, a fragment of adrenocorticotropin (ACTH) with known central nervous system (CNS) activity, on the dimensional complexity of the ongoing electroencephalographic (EEG) activity. Stressful stimuli cause ACTH to be released from the pituitary, and as a neuropeptide ACTH may concurrently exert adaptive influences on the brain's processing of these stimuli. Previous studies have indicated an impairing influence of ACTH on selective attention. METHODS: Dimensional complexity of the EEG, which indexes the brain's way of stimulus processing, was evaluated while subjects performed tasks with different attention demands. Sixteen healthy men (23 to 33 years) were tested once after placebo and another time after administration of ACTH 4-10 (1.25 mg intravenously (i.v.), 30 minutes before testing). The EEG was recorded while subjects were presented with a dichotic listening task (consisting of the concurrent presentation of tone pips to the left and right ear). Subjects either a) listened to pips in both ears (divided attention), or b) listened selectively to pips in one ear (selective attention), or c) ignored all pips. RESULTS: Dimensional complexity of the EEG was higher during divided than selective attention. ACTH significantly increased the EEG complexity during selective attention, in particular over the midfrontal cortex (Fz, Cz). CONCLUSIONS: The effects support the view of a de-focusing action of ACTH during selective attention that could serve to improve the organism's adaptation to stress stimuli.

Adrenocorticotropic Hormone↗