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Biomedical subjects

P Brugger

Publications and source records attributed to P Brugger.

At least 37 records · Page 2Linked to original sources
PubMed1999

Qualitative hemispheric differences in semantic category matching.

A unilateral category matching task with words as stimuli was employed to investigate semantic processing in the right and left hemispheres (RH, LH). An overall right visual field (RVF)/LH dominance was observed and performances were better than chance, also in the left visual field (LVF)/RH. A qualitative analysis of reaction times with individual differences multidimensional scaling (INDSCAL) revealed that LVF/RH INDSCAL solutions were significantly more differentiated in structure than RVF/LH solutions in terms of number and size of dimensions. These findings support a depth of activation hypothesis of hemispheric processing, with the LH rapidly and focally and the RH slowly and diffusely activating the semantic network.

Adult↗
PubMed1999

Vestibular stimulation affects dichotic lexical decision performance.

We report an experimental attempt to shift, by vestibular stimulation, healthy subjects' right ear advantage (REA) in a dichotic listening (DL) task with words and nonwords as stimuli. Forty right-handed men performed the task under two different conditions, once while sitting in a stationary turning chair (baseline) and once during sinusoidal rotation. In this latter condition, every other stimulation was received during maximal left-to-right (i.e., clockwise), every other during maximal right-to-left (i.e., counterclockwise) acceleration. There was a reliable REA for lexical decision accuracy in the baseline and right-to-left trials but not during left-to-right rotation. While right ear performance was unaffected by rotation, there were more correct lexical decisions to left ear targets exclusively during left-to-right turns (one-tailed P = 0.05). Since there were no parallel shifts in auditory thresholds under the different conditions, this effect is not due to any hypothetical auditory-vestibular interactions on a primary sensory level. The improvement in left ear DL performance, although small in our study, is comparable to the symptom-alleviating effect of caloric vestibular stimulation in patients with left-sided hemispatial neglect and interpreted as a consequence of a rotation-induced attentional shift towards the left hemispace.

Adult↗
PubMed1999

One hundred years of an ambiguous figure: happy birthday, duck/rabbit.

In the present study, Jastrow's famous ambiguous drawing of a duck/rabbit was presented to 100 students along with 11 published variants from later research. The beak/ears of the animal pointed to the right for half of the subjects and to the left for the other half. For each figure subjects were required to rate the ease of bird and of rabbit identification on a 9-point scale. Raw data of subjects' ratings are presented for the convenience of experimenters planning research with a specific bird/rabbit figure. Of the 12 figures, 6 were significantly bird-dominant, 2 were rabbit-dominant, and only 4 figures were truly ambiguous, i.e., a bird was as easily identified as was a rabbit. With the exception of one figure (the whole-body representation of a duck/rabbit), bird and rabbit ratings were not affected by the orientation of the beak/ears. Jastrow's original drawing was the seventh out of the 12 figures in rated ambiguity, suggesting a secure place for it in research on visual ambiguity.

Adolescent↗
PubMed1999

Hallucinatory experiences in extreme-altitude climbers.

OBJECTIVE: This study attempted a systematic investigation of incidence, type, and circumstances of anomalous perceptual experiences in a highly specialized group of healthy subjects, extreme-altitude climbers. BACKGROUND: There is anecdotal evidence for a high incidence of anomalous perceptual experiences during mountain climbing at high altitudes. METHOD: In a structured interview, we asked eight world-class climbers, each of whom has reached altitudes above 8500 m without supplementary oxygen, about hallucinatory experiences during mountain climbing at various altitudes. A comprehensive neuropsychological, electroencephalographic, and magnetic resonance imaging evaluation was performed within a week of the interview (8). RESULTS: All but one subject reported somesthetic illusions (distortions of body scheme) as well as visual and auditory pseudohallucinations (in this order of frequency of occurrence). A disproportionately large number of experiences above 6000 m as compared to below 6000 m were reported (relative to the total time spent at these different altitudes). Solo climbing and (in the case of somesthetic illusions) life-threatening danger were identified as probable triggers for anomalous perceptual experiences. No relationship between the number of reported experiences and neuropsychological impairment was found. Abnormalities in electroencephalographic (3 climbers) and magnetic resonance imaging (2 climbers) findings were likewise unrelated to the frequency of reported hallucinatory experiences. CONCLUSIONS: The results confirm earlier anecdotal evidence for a considerable incidence of hallucinatory experiences during climbing at high altitudes. Apart from hypoxia, social deprivation and acute stress seem to play a role in the genesis of these experiences.

Adult↗
PubMed1998

Stimulus-response compatibility in representational space.

Spatial stimulus response (S-R) compatibility designates the observation that speeded reactions to unilateral stimuli are faster for the hand ipsilateral than for the hand contralateral to the sensory hemifield containing the stimulus. In two experiments involving presentation of the numbers 1 to 11 in the center of the visual field we show (1) a left-hand reaction time (RT) advantage for numerals < 6 and a right-hand advantage for those > 6 for subjects who conceive of the numbers as distances on a ruler, and (2) a reversal of this RT advantage for subjects who conceive of them as hours on a clock face. While the results in the first task (RULER) replicate a robust finding from the neuropsychology of number processing (the "SNARC effect") those in the second task (CLOCK) show that extension of the number scale from left to right in representational space cannot be the decisive factor for the observed interaction between hand and number size. Taken together, the findings in the two tasks are best accounted for in terms of an interaction between lateralized mental representations and lateralized motor outputs (i.e. an analog of traditional spatial S-R compatibility effects in representational space). We discuss potential clinical applications of the two tasks in patients with neglect of representational space.

Adolescent↗
PubMed1998

Schizotypal thinking and associative processing: a response commonality analysis of verbal fluency.

OBJECTIVE: To determine whether people with high scores for schizotypal thinking generate more uncommon words in a letter fluency task than people with low scores. DESIGN: Prospective study. SETTING: University psychology department. PATIENTS: Forty healthy, right-handed students. INTERVENTIONS: Students were administered the Magical Ideation (MI) Scale and a 2-minute letter fluency task in which they named as many nouns as possible beginning with "A" or "F," in any order. OUTCOME MEASURES: Total number of words produced and percentage of unique, rare and common words (as determined by the responses of the whole group); scores on MI scale. RESULTS: Participants with high scores (above the median) on the MI scale generated as many words as those who had low scores. People in both groups also generated a comparable number of unique words (named by only 1 person) and common words (named by 6 or more people). As hypothesized, people with high scores on the MI scale generated more rare words (named by fewer than 6 people) than those with low scores. CONCLUSIONS: These findings support the view of a disinhibition of semantic network functioning as the neuropsychological basis of creative thought, magical ideation and thought disorder.

Adult↗
PubMed1998

Creative, paranormal, and delusional thought: a consequence of right hemisphere semantic activation?

OBJECTIVE: There is a rapidly growing body of evidence for an association between schizophrenic syndromes and the absence of a clear pattern of hemispheric dominance for language. Independent work with healthy subjects suggests that one feature of right hemispheric (RH) linguistic processing is a coarse as opposed to a focused semantic activation. We provide a comprehensive review of the literature to these hitherto unrelated fields of research and present an experiment assessing functional hemispheric asymmetries for language processing in healthy volunteers, differing in the susceptibility to schizophrenia-like experiences and thoughts. BACKGROUND: Forty right-handed men were administered a lateralized tachistoscopic lexical decision task. They also completed the Magical Ideation (MI) scale, which examines a variety of paranormal experiences and beliefs. RESULTS: Although the 20 subjects with MI scores below the median displayed the expected right visual field/left hemisphere (RVF/LH) superiority in lexical decision accuracy, the 20 high scorers were equally proficient in both visual fields. Compared to the low scorers, they made significantly more correct decisions in the left visual field/right hemisphere (LVF/RH). CONCLUSIONS: These results corroborate previous findings of a reduced LH language dominance for subjects scoring high on scales measuring proneness to schizophrenic behavior and thought ("schizotypy"). We propose that this dominance failure, which is commonly observed in patients with acute signs of psychosis, facilitates the emergence of paranormal and delusional ideas by way of RH associative processing characteristics, that is, coarse rather than focused semantic activation. As unfocused semantic processing is also characteristic of creative thinking, the use of the RH semantic system may constitute a selective evolutionary advantage allowing the genes predisposing to schizophrenia to proliferate despite the obvious disadvantages of this devastating disease.

Adolescent↗
PubMed1997

[Melatonin and coronary heart disease].

The observation of raised nocturnal urinary norepinephrine excretion in patients with coronary heart disease (CHD), together with results of animal experiments showing a suppression of sympathetic activity by melatonin, were the reasons for this investigation. In 15 patients with CHD and 10 controls the concentrations of serum melatonin, serotonin and N-acetylserotonin were determined in samples gained by venopuncture at 14.00 h and 02.00 h. The melatonin secretion was significantly lower at 02.00 h in the patients with CHD than in the controls. Moreover the serotonin concentration was significantly lower at 14.00 h in the patients with CHD, and somewhat, but not significantly, lower at 02.00 h than in the controls. On the other hand, the serum concentrations of N-acetylserotonin showed a tendency towards higher levels in the CHD patients than in the controls. The causes and consequences of the diminished secretion during the night in patients with CHD are discussed.

Circadian Rhythm↗
PubMed1997

Right hemispatial inattention and magical ideation.

In visual and tactile bisection tasks, healthy subjects have been reported to place the subjective midline towards the left of the objective midline. This phenomenon, known as "pseudoneglect", has been interpreted as a right hemispatial inattention due to hypodopaminergic activity of the left hemisphere mesocortical dopamine system. In schizophrenic patients pseudoneglect was previously found to be correlated with severity of psychotic symptoms. We administered a tactile bisection task (rod centering) to 40 healthy students (20 women and 20 men). All participants also filled in the "Megical Ideation" scale which asks for hallucination-like experiences and delusion-like beliefs. There was no significant pseudoneglect for the group as a whole. However, Magical Ideation scores were significantly correlated to the size of relative right-sided inattention for the 20 men only. On the background of the findings in patients with schizophrenia we conclude that, at least in healthy men, susceptibility to schizophrenia-like experiences and thoughts is likewise accompanied by an attentional shift towards the left hemi-space.

Adolescent↗
PubMed1997

[The dose-dependent effects of oral premedication with midazolam].

OBJECTIVE: The aim of this study was to examine the psychological effects, well-being and side effects after various doses of oral midazolam medication. METHODS: After informed consent has been obtained and following the approval by the institutional ethical committee, 80 adult patients in the ASA physical status I and II were randomly assigned to one of five different premedication groups: 3.75, 7.5, 11.25, 15 mg midazolam, and placebo. The medication was given in a double-blind fashion 60 min before induction of general anaesthesia for various surgical procedures. At 3 definite stages (before premedication, 30 and 60 min after premedication), blood pressure, heart rate, transcutaneous oxygen saturation and respiratory rate were measured. Sedation and well-being were graded according to a 5-point scale, and the subjective anxiety level was assessed according a visual analogue scale (range 0-100 mm). Anterograde and retrograde amnesia were measured by recall of auditive and visual stimuli. Finally, patients were asked whether in case of future surgery they would prefer the same or a different medication. RESULTS: Demographic data were similar in all groups. There was no significant difference in respiratory rate, oxygen saturation, blood pressure or heart rate. Alertness declined only after 60 min in the groups treated with 7.5 mg and more midazolam. During the entire measurement period, anxiolysis was not different from placebo in any of the midazolam groups. In comparison to placebo, all midazolam groups showed a statistically significant and dose dependent anterograde amnesia for visual stimuli. Subjective well-being scores showed no differences between the groups. Only few side effects were seen following doses of 7.5 mg and higher, including ptosis, strabismus, diplopia, speech disorders, disorientation and vertigo. The majority of patients in all groups indicated a wish for the same medication in case of future anaesthesia for surgical interventions. CONCLUSIONS: Midazolam administered orally prior to surgical procedures showed marked interindividual variability. Sedation and amnesia were dose-dependent and were evaluated by the patients as acceptable. Anxiolysis was not significantly different from placebo. A dose of 7.5 mg midazolam showed the best relation between desirable and undesirable effects. Adequate attention given to the patient by the anaesthesiologist prior to surgery seems to be as important and beneficial as oral medication with midazolam.

Administration, Oral↗
PubMed1997

Variables that influence the generation of random sequences: an update.

This article updates Tune's 1964 review of variables influencing human subjects' attempts at generating random sequences of alternatives. It also covers aspects not included in the original review such as randomization behavior by patients with neurological and psychiatric disorders. Relevant work from animal research (spontaneous alternation paradigm) is considered as well. It is conjectured that Tune's explanation of sequential nonrandomness in terms of a limited capacity of short-term memory can no longer be maintained. Rather, interdependence among consecutive choices is considered a consequence of an organism's natural susceptibility to interference. Random generation is thus a complex action which demands complete suppression of any rule-governed behavior. It possibly relies on functions of the frontal lobes but cannot otherwise be "localized" to restricted regions of the brain. Possible developments in the field are briefly discussed, both with respect to basic experiments regarding the nature of behavioral nonrandomness and to potential applications of random-generation tasks.

Brain Diseases↗
PubMed1996

Human colour discrimination based on a non-parvocellular pathway.

BACKGROUND: Traditionally, colour information is assumed to be carried by neural channels in the parvocellular pathway and to be encoded in an opponent manner, while other, non-parvocellular, spectrally non-opponent channels are thought to play no part in colour vision. But is the parvocellular pathway the only way that colours can be discriminated in human vision? We studied two patients with cerebral achromatopsia, who lack conscious colour perception but are nevertheless able to make use of colour information. In particular, we investigated whether, in these patients, colour discrimination is mediated by the parvocellular pathway. RESULTS: The achromatopsic patients carried out a forced-choice colour- and luminance-discrimination task, and showed clear evidence of unconscious colour processing, consistent with previous studies. We added different types of luminance noise to see when this unconscious colour information could be masked. The results of the colour-discrimination-with-noise and the brightness-non-additivity experiments showed a double-dissociation between patients. This indicates that, in one patient, unconscious colour discrimination may be subserved by a spectrally non-opponent mechanism, which does not have the characteristics of the parvocellular pathway and which is responsive to fast flicker. Spectral sensitivity, contrast sensitivity and motion perception experiments confirmed that this patient lacks a working opponent parvocellular system. The second achromatopsic patient showed evidence of a residual parvocellular system. CONCLUSIONS: Our results show that chromatic discrimination need not be mediated by neural mechanisms, the parvocellular system in particular, normally assumed to subserve conscious colour perception. Such discrimination may be mediated by a neural subsystem which responds to fast flicker, is spectrally non-opponent, and supports normal motion perception.

Aged↗
PubMed1996

Random number generation in dementia of the Alzheimer type: a test of frontal executive functions.

The quality of attempts at generating a random sequence of the numbers 1-6 was studied in 30 patients with dementia of the Alzheimer type (DAT) and 30 elderly normal control (NC) subjects. Three main findings emerged: (1) DAT patients' subjective random sequences were more streotyped (contained fewer digit combinations) than those of NC subjects. (2) This difference in response stereotypy was due to patients' enhanced tendency to arrange consecutive numbers in an ascending series ('counting bias'). (3) In the patient group, degree of sequential nonrandomness was positively correlated with overall severity of dementia and with the extent to which performance on neuropsychological tests specifically assessing executive functions (fluency, naming, error monitoring) was impaired. These results illustrate a loss of behavioral complexity in the course of dementia and are interpreted as reflecting a frontal dysexecutive syndrome in DAT.

Aged↗
PubMed1996

Repetitive behavior and repetition avoidance: the role of the right hemisphere.

Based on clinical observations of patients suffering from brain damage, a recent model assumes a right hemisphere dominance for the suppression of repetitive behavior. This study set out to test whether or not the well-known effect of repetition avoidance in sequential response production is likewise mediated by the right hemisphere. It was found that, in 40 healthy subjects, avoidance of repetitions in a random number-generation task correlated positively with a relative superiority for design as compared to letter fluency. Since design fluency is predominantly mediated by the right frontal lobe and letter fluency by the left, this finding supports the notion of a right hemisphere dominance for the avoidance of repetitive responses. This study illustrates the usefulness of a neurobehavioral approach to repetition behavior in the randomization of response. In particular, it demonstrates that the phenomenon of repetition avoidance may be better accounted for in terms of a control mechanism preventing perservation than by referring to human subjects' "generally biased concept of randomness."

Adult↗
PubMed1995

Impaired nocturnal secretion of melatonin in coronary heart disease.

Patients with coronary heart disease have increased nocturnal urinary noradrenaline. Because melatonin suppresses sympathetic activity, we measured serum melatonin concentrations at night (0200 h) in 15 patients with coronary heart disease. Melatonin was significantly lower in the patients than in 10 healthy controls (median 7.8 [interquartile range 6.5-11.8] vs 36.2 [32.2-42.5] pg/mL, p < 0.0001). Thus, impaired nocturnal secretion of melatonin is associated with coronary heart disease.

Circadian Rhythm↗