Biomedical subjects

Peter Jönsson

Publications and source records attributed to Peter Jönsson.

8 recordsLinked to original sources

PubMed2006

Respiratory sinus arrhythmia as a function of state anxiety in healthy individuals.

Respiratory sinus arrhythmia (RSA) was examined in relation to state and trait anxiety in healthy individuals. Time-frequency analyses of HR-power spectrum in the high frequency region (0.12-0.40 Hz), related to RSA, were examined in 43 women and 39 men. Based on median split, the participants were divided into high and low state and trait anxiety groups. The main result showed that high state anxious individuals had higher RSA-magnitude (HF-power) than low state anxious individuals. The higher RSA-magnitude in the former group was interpreted as reflecting increased attention or vigilance together with motor and behavioural inhibition. No significant effects of trait anxiety or gender were found.

Adult↗

PubMed2006

Estimation of HRV spectrogram using multiple window methods focussing on the high frequency power.

In this paper, the results of different multiple window spectrum analysis methods are compared in the estimation of heart rate variability (HRV) power spectra, in the high frequency band (HF), around 0.25 Hz, related to respiratory sinus arrhythmia (RSA). The evaluation is performed by simulating different spectrum shapes and peak frequency locations and calculating the mean squared error of a frequency range close around the strongest spectral peak. The results show that it is preferable to use the Peak Matched Multiple Windows in most situations, but the Welch method and the Sinusoid Multiple Windows can be as reliable in certain aspects.

Algorithms↗

PubMed2004

Dismissing-avoidant pattern of attachment and mimicry reactions at different levels of information processing.

Individuals with a dismissing-avoidant pattern of attachment are assumed to repress anxiety-related signals, a disposition hypothesized to interfere with facial mimicry and emotional contagion. Further, they are assumed to have one internal working model associated with anxiety, operating out of awareness at early, automatic stages of information processing, and another positive model operating at later, cognitively controlled stages of processing. The main aim of the present investigation was to compare facial mimicry in dismissing-avoidant and non-dismissing subjects at different levels of information processing. Pictures of happy and angry faces were exposed to 61 subjects at three different exposure times (17, 56, and 2,350 ms) in order to elicit facial muscle reactions, first at automatic levels and then at a more controlled levels. Corrugator activity ("frowning muscles") represented negative emotions and zygomaticus activity ("smiling muscles") positive emotions. The dismissing-avoidant subjects scored significantly lower on emotional empathy than the non-dismissing subjects. At the automatic level the dismissing-avoidant subjects showed "normal" corrugator responses (negative emotions) upon exposure to angry faces. At the cognitively controlled level of processing (2,350 ms) a significant interaction effect was shown between Faces x Muscles x Attachment pattern. The dismissing-avoidant subjects showed no corrugator response and an increased zygomaticus response ("smiling reaction") to the angry face, whereas the non-dismissing subjects reacted with a significant mimicking reaction. The dismissing-avoidant subjects' tendency to "smiling" in response to the angry face at the controlled level (2,350 ms) may be interpreted as a repression of their earlier, automatically evoked (56 ms) negative emotional reaction.

Adult↗

PubMed2003

The effects of pictures of emotional faces on tonic and phasic autonomic cardiac control in women and men.

The aim of the present study was to examine autonomic function in response to negatively and positively valenced pictures under different levels of conscious recognition. Heart period variability (HPV) and heart rate (HR) reactivity were studied in 53 males and females who were being shown pictures of angry and happy faces. The pictures, which were backwardly masked, were presented once every 30 s during a 5-min period and under three conditions (counterbalanced for type of facial expression): below the level of conscious recognition (17 ms), at an intermediate level (56 ms), and at a clearly recognizable level (2370 ms). Analyses of HR power spectrum (for 5 min in each condition) in the high frequency region (HF: 0.15-0.5 Hz) that reflects respiratory sinus arrhythmia, as well as analysis of phasic heart rate responses (7.5 s in 0.5 epochs following every picture presentation) were carried out. The main findings were that HF-power was higher, and cardiac midinterval acceleration lower, in response to angry as opposed to happy faces, a result obtained only for the men, however. No interaction effect between facial expression and the three exposure conditions was found, suggesting that the pictures induced emotional activation both subliminally and supraliminally. The results were discussed in terms of increased attention to aversive stimuli.

Adult↗

PubMed2003

Determinants of IGF-I status in a large cohort of growth hormone-deficient (GHD) subjects: the role of timing of onset of GHD.

BACKGROUND: IGF-I standard deviation score (SDS) is widely used in clinical practice; however, factors determining IGF-I SDS in GH-deficient (GHD) individuals remain incompletely understood. Earlier studies have been limited by the small size of cohorts studied. We have used the KIMS database to examine if a true difference exists between subjects who developed GHD in adult life (AO), and those who developed GHD in childhood (CO). PATIENTS: A total of 1317 patients fulfilled the inclusion criteria, 1073 with AO GHD and 244 with CO GHD. METHODS: Serum IGF-I concentrations were determined by a hydrochloric acid-ethanol extraction radioimmunoassay method using synthetic IGF-I for labelling. The reference range was calculated using normative data from healthy Swedish individuals. RESULTS: A total of 86% of patients with CO GHD but only 52% of patients with AO GHD had IGF-I SDS below -2 SDS. The CO cohort had a lower IGF-I SDS (-4.69 vs. -2.24, P < 0.0001), a smaller body mass index (BMI; 26.6 vs. 28.6 kg/m2, P < 0.0001) and waist-hip ratio (WHR; 0.90 vs. 0.92 P < 0.001) than the AO cohort. A stepwise multiple linear regression was performed to examine the principal determinants of IGF-I SDS. Age at onset of GHD was the most important determinant of IGF-I SDS, contributing 17% towards the variability of IGF-I SDS. Timing of onset, gender, BMI, and number of pituitary hormone deficiencies other than GH deficiency were also significant determinants of IGF-I SDS. CONCLUSION: Whilst age at onset of GHD was the most important determinant of IGF-I SDS, individuals with CO GHD had values on average 1.43 lower than those with AO GHD, all other factors being equal. Potential explanations include differences in GH secretory patterns, variation in body composition, and/or suboptimal treatment of GHD in childhood.

Adolescent↗

PubMed2003

The effect of seat design on vibration comfort.

A field study was done to evaluate different seat designs in the aspect of minimizing vibration transmission and reducing the level of discomfort experienced by drivers subjected to transient vibration. Two seat designs (sliding or fixed in the horizontal direction) were compared in an experiment based on variation of sitting posture, speed, and type of obstacle. The comparison was done by assessing discomfort and perceived motion and by vibration measurement. Ten professional drivers were used as participants. Maximum Transient Vibration Value and Vibration Dose Value were used in the evaluation. The results showed that a sliding seat is superior in attenuating vibration containing transient vibration in the horizontal direction. It was also perceived as giving less overall and low back discomfort compared to a fixed seat.

Automobile Driving↗

PubMed2003

Models-of-self and models-of-others as related to facial muscle reactions at different levels of cognitive control.

The hypotheses of this investigation were based on attachment theory and Bowlby's conception of "internal working models", supposed to consist of one mainly emotional (model-of-self) and one more conscious cognitive structure (model-of-others), which are assumed to operate at different temporal stages of information processing. Facial muscle reactions in individuals with positive versus negative internal working models were compared at different stages of information processing. The Relationship Scale Questionnaire (RSQ) was used to categorize subjects into positive or negative model-of-self and model-of-others and the State-Trait Anxiety Inventory was used to measure trait anxiety (STAI-T). Pictures of happy and angry faces followed by backward masking stimuli were exposed to 61 subjects at three different exposure times (17 ms, 56 ms, 2,350 ms) in order to elicit reactions first at an automatic level and then consecutively at more cognitively elaborated levels. Facial muscle reactions were recorded by electromyography (EMG), a higher corrugator activity representing more negative emotions and a higher zygomaticus activity more positive emotions. In line with the hypothesis, subjects with a negative model-of-self scored significantly higher on STAI-T than subjects with a positive model-of-self. They also showed an overall stronger corrugator than zygomatic activity, giving further evidence of a negative tonic affective state. At the longest exposure time (2,350 ms), representing emotionally regulated responses, negative model-of-self subjects showed a significantly stronger corrugator response and reported more negative feelings than subjects with a positive model-of-self. These results supported the hypothesis that subjects with a negative model-of-self would show difficulties in self-regulation of negative affect. In line with expectations, model-of-others, assumed to represent mainly knowledge structures, did not interact with the physiological emotional measures employed, facial muscle reactions or tonic affective state.

Adult↗

PubMed2003

Aspects of growth hormone (GH) replacement in elderly patients with GH deficiency: data from KIMS.

This study was designed to examine the clinical characteristics of adult-onset growth hormone deficiency (AO-GHD) in patients aged over 65 years in comparison with patients aged less than 65 years. In addition, the effects of 12 months of GH replacement therapy on body composition, carbohydrate metabolism, blood pressure, serum lipids and quality of life were compared between patients aged over 65 years and patients under 45 years, 45-55 years and 55-65 years of age. The investigation was an observational study of patients enrolled in KIMS (Pharmacia International Metabolic Database). Baseline clinical characteristics were qualitatively similar, and scores from the Assessment of Quality of Life in GH-deficient Adults questionnaire (QoL-AGHDA) were indistinguishable between patients aged over 65 years and younger patients. Improvements in QoL-AGHDA scores were similar in all age groups during GH replacement therapy. Significant reductions in total and low-density lipoprotein cholesterol levels were observed in all groups and tended to be greater in patients aged over 65 years. Waist circumference and waist:hip ratio were not influenced by GH replacement therapy in women aged over 65 years, which was in contrast to the reductions observed in younger male and female patients and the decrease in waist circumference observed in men aged over 65 years. The similarities and differences in response to GH replacement therapy between patients aged over 65 years and those aged less than 65 years remained evident when the latter group was stratified by age. In conclusion, older patients with AO-GHD who receive GH replacement therapy achieve beneficial effects equivalent to those seen in younger patients in all age groups and require lower doses of GH.

Adult↗