Biomedical subjects

O Franzén

Publications and source records attributed to O Franzén.

14 recordsLinked to original sources

PubMed2001

Oscillation of pain intensity during adenosine infusion. Relationship to beta-endorphin and sympathetic tone.

Adenosine is a neuromodulator with both excitatory and inhibitory effects dependent in part upon preconditions; it can act as an algesic or an analgesic agent. Previously we found variations of pain intensity during constant infusion of adenosine. We therefore quantified pain intensity during constant infusion of adenosine at a rate of 140 microg/kg/min intravenously in healthy volunteers, placebo controlled, double blind, and the relation to hemodynamic, vasomotor and sudomotor responses of the sympathetic nervous system and to the role of peripheral beta-endorphin response. The perceived chest pain during adenosine infusion showed an oscillatory pattern. Painful periods of about 30s were interrupted by painfree periods, and pain was always preceded by an increase in vasomotor sympathetic activity and by increased sudomotor activity. Plasma beta-endorphin values were heterogenous but exhibited an increase during infusion.

Adenosine↗

PubMed1999

Pulpal ischemia in man: effects on detection threshold, A-delta neural response and sharp dental pain.

Preferential blocks of peripheral nerves have shown that myelinated nerves are more susceptible to local compression and less resistant to asphyxia than unmyelinated fibers. Since two groups of functionally different nociceptors exist in the dental pulp, it is of theoretical and clinical interest to determine the influence of ischemia on the sensitivity of human dental pulp, using standard means for testing tooth vitality and at the same time investigating the intensity coding in one pathway of the afferent trigeminal system. Adrenaline was used to study the differential effect of adrenaline-induced ischemia on intradental A-delta nerve activity (INA) and the concomitant sharp pain, as well as on the detection threshold for monopolar electrical stimulation. Cold (ethyl chloride) and heat (heated gutta-percha) stimulation was applied to the tooth surface. In accordance with the hydrodynamic theory of dentin sensitivity the rapid fluid flow induced in the dentinal tubuli by these thermal stimuli is an adequate stimulus for selectively activating the A-delta nerves in healthy pulps. Consistency plots of the magnitude of the perceptual experience of sharp pain against the neural population response in linear coordinates yielded a high product-moment correlation, implying linearity for the intensity coding relationship. In contrast to the significant reduction of INA and its perceptual correlate of sharp pain after adrenaline administration, the electrical detection threshold remained constant during the full test period, suggesting that electrical threshold measurements have their limitations as a diagnostic tool or criterion for assessing the sensitivity of the dental pulp. The absence of A-delta activity was parallelled by no sensation of sharp pain. These findings suggested that the integrated neural A-delta activity constituted the underlying peripheral neurophysiological mechanism of the sensory intensity of sharp dental pain.

Adult↗

PubMed1997

Reduced activity in the extrastriate visual cortex of individuals with strabismic amblyopia.

In order to examine the relationship between reduced visual acuity in human strabismic amblyopia and the cortical activation pattern, we studied, by use of positron emission tomography (PET) and the H2(15)O bolus technique, changes in the regional cerebral blood flow (rCBF) induced by monocular visual stimulation of 8 individuals with this disorder. Individual amblyopic thresholds for monocular detection of the checkerboard pattern were employed as stimuli for both eyes during PET scans. Statistical analysis of subtracted images showed significant increases in rCBF (P < 0.05) by the stimulation of the sound eye localized bilaterally to Brodmann's areas (BAs) 17-19. The cortical response evoked by the amblyopic eye was significantly reduced (P < 0.05) in the ipsilateral BAs 18, 19. These results suggest that the reduction in contrast sensitivity (pattern vision) in amblyopia is coupled with deactivation in identifiable regions of occipital visual areas, including ipsilateral BAs 18,19.

Adult↗

PubMed1994

Quantitative judgements and matching of subjective speed of apparent laser speckle flow induced by refractive defocus.

The speed of laser speckles induced by refractive defocus was determined by means of the direct method of free magnitude estimation in combination with sensory verbal descriptors. Physical measures of angular velocities were obtained by matching a similar pattern under the viewer's control to the laser speckles for equal subjective velocity. Theoretical speckle speed was calculated from geometrical formulae proposed by Charman [7]. The velocity percept of apparent speckle motion was a monotonic function of the refractive power of the positive lenses added to the observer's eye, although it exhibited a tendency of levelling off at the greatest strength. The magnitude estimates of this motion percept were highly correlated with corresponding subjective judgements of the angular velocity of the real motion of the matched pattern. Theoretical velocity plotted against empirically obtained values of velocity through matching yielded a product moment correlation coefficient of 0.98 and a regression coefficient of 0.94 indicating a high internal and external validity of these measurements as well as the usefulness of speckle speed as a cue for voluntary changes of the crystalline lens of the eye.

Acceleration↗

PubMed1994

Velocity percepts of apparent laser speckle motion modulated by voluntary changes of visual accommodation: real-time, in-vivo measurements of the accommodative response.

This study examined negative volitional accommodation under open-loop viewing conditions by means of a coherent laser light pattern (633 nm) whose direction and velocity of motion is determined by the refractive state of the eye. Using the direct scaling procedure of free magnitude estimation, the subjects were required to quantitatively judge velocities of speckles when the retinal image of the subjects' eye was minimally influenced and when the subject was instructed to exert voluntary negative accommodation. Real-time, in-vivo measures of accommodation indicated that the dioptric strength of the crystalline eye lens was reduced under the condition of mental effort, and that the volitional accommodation values ranged between -0.26 and -1.90 D. The amplitude of these responses were noticeably correlated with individual measures of dark focus, so that larger dark focus values were associated with higher amplitudes of the voluntary negative response, and vice versa. By converting the dioptric strength of added optical lenses and the in-vivo measures of the eye lens curvature into angular velocities of laser speckles whose speed changes with focus relative the plane of stationarity, a specification of the proximal stimulus flow was obtained. The psychophysical functions describing the relationship between subjective speed and angular velocity generated either by placing lenses in front of the eye or by voluntary changes in accommodation had approximately the same appearance suggesting that the percepts reported by the subjects were valid and veridical estimates of the velocity of speckle movement.

Acceleration↗

PubMed1994

Dental pain evoked by hydrostatic pressures applied to exposed dentin in man: a test of the hydrodynamic theory of dentin sensitivity.

The hydrodynamic theory of dentin sensitivity holds that pain is evoked by stimuli producing minute shifts in tubule fluid. In human volunteers hydrostatic pressures were applied to prepared dentinal cavities. The subjects reported the magnitude and quality of their sensations of pain by means of an intermodal matching technique in combination with verbal descriptors. No pain could be elicited when the smear layer was present. After removal of this layer, pressure stimuli of either direction evoked sharp pain. Rapid changes in pressure induced higher pain intensities than slow changes, indicating that the dental A-delta system is dynamic and gradient dependent. These results provide support for the hydrodynamic theory of dentin sensitivity and also lend credence to the notion that the movement of fluid across dentin induces a selective activation of the A-delta nerves in healthy pulps which is highly correlated with a sensation of sharp and/or shooting pain.

Acid Etching, Dental↗

PubMed1986

Respiratory-related cortical potentials evoked by inspiratory occlusion in humans.

It has long been recognized that humans can perceive respiratory loads. There have been several studies on the detection and psychophysical quantification of mechanical load perception. This investigation was designed to record cortical sensory neurogenic activity related to inspiratory mechanical loading in humans. Inspiration was periodically occluded in human subjects while the electroencephalographic (EEG) activity in the somatosensory region of the cerebral cortex was recorded. The onset of inspiratory mouth pressure (Pm) was used to initiate signal averaging of the EEG signals. Cortical evoked potentials elicited by inspiratory occlusions were observed when C3 and C alpha were referenced to CZ. This evoked potential was not observed with the control (unoccluded) breaths. There was considerable subject variability in the peak latencies that was related to the differences in the inspiratory drive, as measured by occlusion pressure (P0.1). The results of this study demonstrate that neurogenic activity can be recorded in the somatosensory region of the cortex that is related to inspiratory occlusions. The peak latencies are longer than analogous somatosensory evoked potentials elicited by stimulation of the hand and foot. It is hypothesized that a portion of this latency difference is related to the time required for the subject to generate sufficient inspiratory force to activate the afferents mediating the cortical response.

Adult↗

PubMed1983

Depression and somatosensory evoked potentials: II. Correlations between SEP and depressive phenomenology.

In 32 patients with major depressive disorders according to Research Diagnostic Criteria (RDC), symptomatology was rated using the Schedule for Affective Disorders and Schizophrenia (SADS), and somatosensory evoked potentials (SEP) elicited by tactile fingertip stimuli were recorded at the vertex of the scalp. Patients were drug-free except for benzodiazepines. Amplitudes and amplitude/stimulus intensity slopes were adjusted to same sex, age, height, and weight. Uni-and multivariate correlations revealed associations between the N140-P200 amplitude and hypothyroidlike aspects of depression with symptoms such as poor appetite and indecisiveness, and between the P100-N140 slope and intrapunitive aspects of depression with symptoms such as negative self-evaluation and suicidal attempts. Neither attention level nor benzodiazepine medication were reflected in these relationships.

Adult↗

PubMed1983

Depression and somatosensory evoked potentials: I. Correlations between SEP and monoamine and purine metabolites in CSF.

In 32 patients with major depressive disorders diagnosed according to Research Diagnostic Criteria (RDC), somatosensory evoked potentials elicited at four levels of tactile fingertip stimulation were recorded. Four peak-to-baseline amplitudes (P100, N140, P200, and P300) and two peak-to-trough amplitudes (P100-N140 and N140-P200) plus their amplitude/stimulus intensity slopes were selected for analysis. All 12 measures were adjusted to same sex, age, height, and weight. Values were linearly and curvilinearly correlated with adjusted levels of homovanillic acid (HVA), 5-hydroxyindoleacetic acid (5HIAA), 3-methoxy-4-hydroxyphenylglycol (MPHG), hypoxanthine, and xanthine in the cerebrospinal fluid (CSF), monoamine and purine metabolites, respectively. Significant negative linear correlations were found between the P300 amplitude and both HVA and hypoxanthine, and between the P200 slope and both 5HIAA and hypoxanthine. A significant positive correlation existed between the N140-P200 slope and 5HIAA. Curvilinear bivariate regressions demonstrated complex topologies of regression surfaces. Neither attention nor benzodiazepine medication were of significant importance in these relationships.

Adult↗

PubMed1978