Biomedical subjects
J Huttunen
Publications and source records attributed to J Huttunen.
[Alcohol consumption in Finland].
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Activation of ipsilateral primary sensorimotor cortex by median nerve stimulation.
We report evidence for activation of ipsilateral primary sensorimotor cortex (SMI) after median nerve stimulation recorded with magnetoencephalography (MEG). We measured somatosensory evoked magnetic fields (SEFs) to median nerve stimulation with a 122-channel helmet-shaped magnetometer in 10 healthy subjects. In five, the magnetic field patterns suggested long-latency activation of the ipsilateral SMI. Source locations found by current dipole fitting corresponded to the SMI hand area, as determined by contralateral stimulation. Further evidence for the origin of the ipsilateral responses in SMI was provided by the suppression of these responses during movement of the contralateral fingers. Sensory input to ipsilateral SMI could play a role in sensorimotor integration of bilateral movements.
Angiotensin-converting enzyme genotypes in the high- and low-risk area for coronary heart disease in Finland.
The deletion/deletion genotype of the insertion (I)/deletion (D) polymorphism of the angiotensin-converting enzyme (ACE) gene has been suggested to be a risk factor for myocardial infarction (MI). The objective of this study was to evaluate whether genotype distributions of the I/D polymorphism of the ACE gene are different between individuals from high-risk and low-risk areas for coronary heart disease in the genetically isolated population of Finland and to assess the impact of this genetic risk factor by comparing individuals with different parental histories of MI. Representative population-based samples of middle-aged men (n = 363) and women (n = 358) from two areas of Finland were used. The area had a borderline significant effect on the prevalence of the genotype DD (beta = 0.35, SE = 0.16, X2 = 470, df = 1, P = 0.03), the DD genotype being more prevalent in eastern Finland (the high-risk area). The II genotype was more prevalent in women with parental history of MI, so we could not replicate the previous findings of the risk-increasing effect of DD genotype in this sample. Although the observed difference in the ACE DD genotype between the high-risk and low-risk areas for coronary heart disease might represent one of the genetic factors contributing to the difference in risk of coronary heart disease between eastern and southwestern Finland, the data emphasize the fact that also other risk factors, including other genes, contribute to this difference and the high incidence of MI in Finland.
Scattering of partially coherent electromagnetic fields by microstructured media.
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[The cholesterol hypothesis has been proved true at last].
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[The importance of oral and dental health].
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Muscle tone in Huntington's disease.
Tone was evaluated quantitatively in 39 patients with Huntington's disease (HD) by measuring resistance to passive elbow flexion and extension movements on a hydraulic testing device. A velocity dependent increase in resistance to passive elbow flexion and to a lesser extent in resistance to passive extension was found in 10 patients. Increase in muscle tone was related to disease duration but not to the age of the patients nor to the severity of choreatic movements or the amount of cognitive impairment. A hypertonic pattern could be observed also in patients without any medication, and seemed not to be related to neuroleptic treatment. The pattern of tone change in HD is compared to the pattern of hemispasticity in upper motor neuron syndrome and to that of Parkinson's disease. It appears that an increase in muscle tone, with a velocity dependent resistance to flexion more than extension movements, is a frequent feature in advanced stages of Huntington's disease.
Are frontal and parietal somatosensory evoked potentials functionally dissociated by changing stimulus rate?
The cortical somatosensory evoked potentials are known to be sensitive to relatively small changes in the stimulus repetition rate of the afferent nerve. However, conflicting reports exist as to whether frontally and parietally recorded potentials at a given latency show differential behaviors as a function of stimulus rate. Because such dissociations of frontal and parietal potentials can have significant implications for the SEP generation mechanisms, the present study was undertaken to further describe in detail these effects on frontal, central and parietal waveforms after median nerve stimulation. Increasing stimulus repetition rate from 1 Hz to 5 Hz had the following effects: (i) in 9 of 16 subjects, the frontal P20 diminished while parietal N20 clearly remained unaltered, (ii) the central P22 was reduced in all subjects, (iii) frontal N30 and parietal P27 were attenuated in all subjects, the average magnitude of the reductions being nearly equal for these deflections. The results support the view that changing stimulus rate can functionally dissociate frontal and parietal activity around 20 ms, indicating that several partially independent neural populations can contribute to the frontal P20. The results did not lend support for functional dissociation of frontal N30 from parietal P27.
Antioxidants and carcinogenesis.
It is established beyond doubt that free radicals in tissues and cells can damage DNA, proteins, carbohydrates and lipids. These potentially deleterious reactions are at least partly controlled by antioxidants capable of scavenging free radicals. It is widely believed that a proper balance between free radicals and antioxidants is essential for the health of an organism. A vast body of observational epidemiological studies has suggested that high intake of dietary or supplemental antioxidants protects against ischaemic heart disease, various types of cancer and several other diseases. Final proof for the beneficial effects of antioxidants can, however, be obtained from controlled studies. Conflicting results of the first three major clinical trials force us to postpone conclusions of the usefulness of antioxidant supplements in disease prevention until the other on-going trials have been published.
[SETTI-Study and antioxidants--more questions than answers].
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[Free radicals and antioxidants. Advantages of antioxidants in clinical medicine, truth or fiction?].
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Pre- and postcentral cortical somatosensory evoked potentials in hemiparkinsonism.
We recorded cortical frontal, central, and parietal somatosensory evoked potentials (SEPs) in 9 patients with hemiparkinsonism and in a group of 25 healthy volunteers. No differences were observed in the SEPs recorded after stimulation of the asymptomatic and symptomatic sides in the patients. Likewise, comparison with the healthy controls did not reveal significant group differences or abnormal waveforms in the patients. Even frontal N30 deflection, which has been reported to be diminished in Parkinson's disease (PD), was normal and symmetric in the patients. Therefore, no evidence was found for altered sensory input to the motor or premotor and supplementary motor cortices in PD.
Pre- and postcentral somatosensory evoked potentials in Huntington's disease: effects of stimulus repetition rate.
We recorded frontal, central and parietal somatosensory evoked potentials (SEPs) to median nerve stimulation in 20 patients with Huntington's disease (HD) and in a group of normal controls. Two stimulus repetition rates, 1 Hz and 5 Hz, were employed. In HD patients the early cortical potentials (latency range 20-30 ms) at all 3 recording locations were replaced by a widespread, broadly configured N20-25 deflection, while later potentials at 40-80 ms did not significantly differ from those of normals. In contrast to the early P22, P27 and N30 potentials in normals, the N20-25 potential in the patients was not significantly modified by changing the stimulus repetition rate. At 40-80 ms the stimulus rate effects were similar in the patients and normals. The results show that early pre- and postcentral SEPs are both pathological in HD, while later frontal and parietal components can be totally preserved. The early N20-25 in HD is possibly a subcortical potential, seen due to unmasking in the absence of early cortical deflections.
Cortical somatosensory magnetic responses in multiple sclerosis.
Somatosensory evoked magnetic fields (SEFs) to contralateral median and ulnar nerve stimulation were analyzed in 10 patients with multiple sclerosis and in 8 healthy controls. SEFs were recorded with a 24-channel SQUID gradiometer over both hemispheres. Seven patients showed abnormally large-amplitude SEF deflections at 60-80 msec; 5 of them had multiple lesions around lateral ventricles in magnetic resonance imaging. In 2 patients with plaques at the level of 3rd and 4th ventricles and medulla, the 30 msec responses were enlarged. The equivalent sources of 20 msec and 30-80 msec responses were in the primary hand sensorimotor cortex both in patients and in control subjects. The results suggest that early and middle-latency SEFs reflect parallel processing of somatosensory input. Recording of middle-latency evoked responses, electric or magnetic, may give additional information about the somatosensory function in multiple sclerosis.
Interaction of afferent impulses in the human primary sensorimotor cortex.
We recorded somatosensory evoked magnetic fields (SEFs) over the hand area of the primary sensorimotor cortex (SMI) in 6 healthy adults in 2 sets of experiments to study interaction of afferent impulses. In experiment 1, SEFs were elicited by contralateral median nerve (MC) stimuli presented alone and 40 msec after a conditioning stimulus to the contralateral ulnar (UC), ipsilateral median (MI) or contralateral tibial (TC) nerve. N20m, P30m and P60m deflections to MC stimulation were markedly attenuated by preceding UC stimulation whereas N40m was enhanced, and a novel P80m emerged. In contrast, MI or TC stimulation did not affect the responses to MC. In experiment 2, the time course of recovery of N20m to median nerve stimuli was studied after stimulation of the adjacent ulnar and of the same median nerve. The recovery curves were similar for both conditioning stimuli with nearly full recovery of N20m at 120 msec. The results indicate marked interaction of impulses from ipsilateral median and ulnar nerves in human SMI, but no evidence was found of interaction from the two hands or from ipsilateral hand and foot.
Influence of stimulus repetition rate on cortical somatosensory potentials evoked by median nerve stimulation: implications for generation mechanisms.
Despite growing clinical and experimental interest in the cortical components of somatosensory evoked potentials (SEPs) little is known about their physiological dynamics, e.g. with changing stimulation parameters. This paper reports the influence of varying stimulus repetition rate from 0.5 to 5 Hz on cortical SEPs up to 60-msec latency after right median nerve stimulation, separately analyzed at frontal (F3), central (C3) and parietal (P3) electrodes. The amplitudes of early frontal P20 and N25, central P14 and N18, and parietal N20 did not change with stimulation rate. Later deflections were significantly modified when their amplitudes were determined with respect to the baseline: at F3 negative N30 and N60 diminished and positive P40 was enhanced with increasing rate of stimulation. At P3 the effects were the reverse, so that positive P27 and P45 were attenuated while negative N34 and N60 were enhanced. At C3 both positive P22 and P40 and negative N60 were reduced. However, the corresponding peak-to-peak amplitudes changed much less. We conclude that SEP waveforms following the earliest cortical deflections are very sensitive to small changes in stimulation frequency. The opposite changes at F3 compared with P3 probably represent the opposite scalp field poles from horizontally oriented generator(s) located within the primary sensorimotor cortex (SMI). We suggest that the rate effects are partly due to selective sensitivity of postexcitatory inhibitory postsynaptic potentials to stimulation frequency.
Modification of cortical somatosensory evoked potentials during tactile exploration and simple active and passive movements.
The present study compares the effects of different types of movement on median nerve somatosensory evoked potentials (SEPs) recorded from frontal, central and parietal electrodes. Test conditions included tactile exploratory movements, repetitive active and passive thumb movements and isometric contraction. All these conditions modified the SEPs in a similar manner. Parietal N20, P25, and N60, central P22 and N32, and frontal N25, N30 and P40 deflections were diminished, while later centro-parietal P40 and fronto-central N60 were unchanged. A small frontal P35 emerged during movement. The subcortical P14 was not changed in any of the conditions. The similar modulatory effects of simple active movements and of tactile exploration indicate that the modification of SEPs does not depend on the importance of proprioceptive feedback information for movement execution. As all modulatory effects were present also during passive movement, these observed effects are most likely to be caused by afferent occlusion in the ascending thalamo-cortical pathways or sensorimotor cortical cell populations.