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Biomedical subjects

L Deecke

Publications and source records attributed to L Deecke.

At least 235 records · Page 13Linked to original sources
PubMed1983

[Standardization of the electromyographic tetany test in the diagnosis of normocalcemic tetany: the 10-minute Trousseau test in patients and healthy humans].

Eighteen adult patients with typical history and signs of normocalcemic tetany (hyperventilation syndrome) and 18 age- and sex-matched controls were submitted to a provocation test for tetany. This consisted of 10-min ischemia of the right arm produced by suprasystolic cuff compression at the upper arm (Trousseau test) and a postischemic electromyographic recording from the right interosseous I muscle. Postischemic repetitive discharges were found in all patients and predominantly consisted of multiples of 5 times and more. These discharges lasted 8 min on the average. Of the normal controls, as many as 16 subjects (88.8%) also exhibited tetanic discharges. However, these preferred a lower number of repetitions, such as doublets or triplets. Both number of repetition and duration of postischemic tetanic activity were significant parameters discriminating between patients and controls (2P less than 0.001), as was the cumulative total number of spontaneous potentials, amounting, on the average, to 10,266 in the group of patients and to only 320 in the controls (2P less than 0.001). The investigation has shown that the occurrence of postischemic tetanic spontaneous activity per se does not help to discriminate between cases of latent tetany and healthy controls. However, a normocalcemic tetanic condition may be assumed if multiples occur with a complexity of quadruplets or more, if these multiples last at least 2 min, and if they appear in a rhythmic order and in groups.

Adult↗
PubMed1983

Human cerebral potentials and visuomotor learning.

Cortical potentials during visuomotor learning were investigated in man using two hand tracking tasks: (i) direct tracking (T) and (ii) inverted (mirror) tracking (IT). Negative cerebral potentials were higher during the IT task over several cortical areas but in particular over the supplementary motor area (SMA). The acquisition of motor skill as measured in the IT task, was highly correlated with the enhancement of the negative potential. This correlation only held for the frontolateral and frontomedial cortex including the SMA but not for the other electrodes.

Cerebral Cortex↗
PubMed1983

Movement-related potentials preceding toe plantarflexion and dorsiflexion.

The cerebral potentials associated with self-paced rapid dorsiflexion and plantarflexion of the left toes were compared in the same experiment using 10 subjects 5 of whom were female and 5 of whom were male. The EEG was recorded from C3, C1, Cz, C2 and C4 including computed bipolar recordings C4/C3 and C2/C1. For both kinds of movements, the Bereitschaftspotential (BP) or readiness potential was bilaterally symmetrical in the first half of the foreperiod. In the later foreperiod, an ipsilateral preponderance of negativity (IPN) developed. The direction of toe movement had no effect on the IPN. The etiology of the paradoxical BP side preponderance prior to toe movements is discussed which can probably be referred to the unique dipole orientation of a generator situated on the mesial cortical surface in the depth of the interhemispherical fissure.

Adolescent↗
PubMed1983

Frontal hemispheric differences in the Bereitschaftspotential associated with writing and drawing.

Twenty right-handed subjects participated in a study investigating the cerebral potentials related to three complex actions: (1) writing one's own signature, (2) drawing a pentagram, and (3) fast meaningless scribbling. The Bereitschaftspotential (BP, readiness potential) started as early as 3 s prior to writing, 2.5 s prior to drawing, but only 1.5 s prior to scribbling. In all three tasks, the BP had its earliest onset over the supplementary motor area (SMA). BP topography was shifted towards the frontal lobes when compared to encephalographic activity reflecting simple finger movements, and was very weak in retro-rolandic leads. The side of the performing hand, as assessed from scribbling, was reflected in a contralateral preponderance of the precentral BP. The maximum BP (about 6 microV) was, in all three tasks, located in FCz (mid fronto-central) overlying the SMA. This location is different from that for simple finger movements, when the maximum is at the vertex. Hemispheric differences were found over the frontal cortex and were characteristic for the verbal and spatial tasks involved: for writing, the BP was significantly larger left frontally than right (even after considering the effect of the performing hand from scribbling), and the difference was largest prior to the onset of movement; for drawing, the BP was larger over the right than over the left frontal lobe, and the difference was largest during the movement.

Action Potentials↗
PubMed1982

Magnetic fields of the human brain accompanying voluntary movement: Bereitschaftsmagnetfeld.

A slow magnetic field shift has been detected in the human brain occurring in the foreperiod of a voluntary finger movement. This magnetic field accompanies a slow negative electrical cerebral potential which occurs in the same foreperiod, the Bereitschaftspotential (BP) of Kornhuber and Deecke. The present report is the first of a magnetic field associated with the BP, and has been named the Bereitschaftsmagnetfeld (BM) or readiness magnetic field. The BM is oriented with the field lines directed out of the head in the pre-rolandic region and with the field lines directed into the head in post-rolandic areas, suggesting a source in the sensorimotor area for the contralateral hand. Distribution of the magnetic fields has so far not revealed a source in the fronto-central midline where the BP is recorded maximally. The time course and morphology of the BP and BM are similar, but they have different topography over the skull.

Cerebral Cortex↗
PubMed1982

Risk-taking and the human bereitschaftspotential.

The effects of response probability and feedback predictability on the human Bereitschaftspotential (BP) were examined in a probability-matching paradigm. The subjects were to guess, by pressing one of two buttons, which of two possible feedback lights could be lighted. The a priori probabilities (30%-70%) of the feedback were known to the subjects. This task was performed both when the feedback was unpredictable and when it was perfectly predictable from the prior information. The BP was enhanced only when the subjects guessed the improbable feedback when it was unpredictable, thereby putting themselves 'at risk.' This effect seemed to be independent of any concurrent contingent negative variation. The results indicate that the BP is sensitive to trial-by-trial variation of the psychological state, which is in some way related to intention.

Adolescent↗
PubMed1981

Vestibulo-thalamic projection to the anterior suprasylvian cortex of the cat.

Suggestive evidence as to the site of a major thalamic relay of the vestibular projection to the anterior suprasylvian (ASS) cortex in the cat has been obtained using the retrograde axonal transport of horseradish peroxidase. The thalamo-cortical neurons are located in several patches surrounding the posterior margins of the ventro-basal complex (VB). This area also was found to receive vestibulo-thalamic projections. It comprises different nuclear groups known to carry somatic, acoustic, visual or combined information, which possibly have certain functions related to kinaesthesia and body orientation in common.

Afferent Pathways↗
PubMed1981

Discrimination between trunk and head rotation; a study comparing neuronal data from the cat with human psychophysics.

Kinesthetic information from labyrinthine and neck receptors is required for reflex control and conscious perception of posture and movement. This study considers (1) the neuronal responses to horizontal labyrinthine and neck stimulation and their interaction both in the anterior suprasylvian (AS) cortex and in the vestibular nuclei (VN) of cats, and (2) human turning sensation related to these stimuli. Convergence of labyrinthine (L) and neck (N) input of comparable sensitivity was found in 80% of the AS neurons and in only 27% of the VN neurons. At both sites, the on-direction of L-responses as well as N-responses was either to the ipsilateral or to the contralateral side (type I and type II responses, respectively). When combining the two stimuli during head rotation, the two inputs could be synergistic (same on-direction) or antagonistic (opposite on-directions). Their interaction consisted of either an additive or subtractive summation leading to enhanced or depressed interaction responses. These interaction patterns are compatible with the subtractive and additive mechanisms which have been proposed to be essential for the stabilisation of the trunk and of the head, respectively. The psychophysical experiments showed that human turning sensations depend on the part of the body to which they are referred. Subjects taking the trunk as reference, reported similar turning sensations during both labyrinthine and neck stimulation, and weak or no turning sensation during head rotation. This suggests an antagonistic interaction of the two inputs. In subjects taking the head as reference, neck stimulation induced an illusionary sensation of head turning. Its direction was such that it would be synergistic with the vestibularly induced sensation of head turning during isolated head rotation. Thus, there appear to exist parallels between the basic operations performed by neurons in cat and by human subjects during labyrinthine-neck interactions.

Animals↗
PubMed1981

Patterns of vestibular and neck responses and their interaction: a comparison between cat cortical neurons and human psychophysics.

The present study provides evidence that during whole-body rotation and during isolated rotation of either the head or the trunk, essentially the same processing of labyrinthine and neck afferent inputs takes place in neurons of the cat's ASS cortex and in humans who try to distinguish these stimulus conditions. This processing includes, among others (1) measurement of angular velocity and displacement during labyrinthine stimulation (whole-body rotation); (2) indication of trunk rotation as well as of an apparent head rotation in the opposite direction during neck stimulation (isolated trunk rotation); and (3) subtraction as well as addition of labyrinthine and neck afferent inputs during combined stimulation (isolated head rotation). Subtraction provides a basis for the discrimination between whole-body rotation and isolated head rotation; addition may optimize the indication of movement and position of the head in space.

Acceleration↗
PubMed1981

Tullio phenomenon with torsion of the eyes and subjective tilt of the visual surround.

A 44-year-old male patient had an acoustic trauma three years previously, after which he suffered from vertigo and tilting of the environment to the right when uttering the vowels u or e. At such times, a tonic eye torsion to the left, which lasted throughout the utterance, was observed under Frenzel's glasses along with head tilt to the left. The phenomenon could be elicited experimentally by right-ear stimulation with low-frequency noise (mean frequency, 125 Hz; 90 dB), as well as by constant pressure. The patient also reported observing the phenomenon with loud noises, nose blowing, obstruction of his right external meatus with the finger, and with altitude pressure changes in a car. This suggests that the phenomenon is elicited via the eardrum and the ossicular chain. Since lateral head tilt and counterrolling were tonic and without nystagmus, it is unlikely that one of the semicircular canals is involved as in usual Tullio cases. Rather, the otoliths may play a role in pathogenesis. Possible causative mechanisms are discussed along with the relevant literature.

Acoustic Stimulation↗
PubMed1979

Cerebral potentials preceding unilateral and simultaneous bilateral finger movements.

Cerebral potentials preceding voluntary bilateral simultaneous finger movements were investigated in 19 right-handed young adult subjects, and were compared with unilateral right-sided finger m n the same experiment. With bilateral movements, the Bereitschaftspotential (BP) was not symmetrical or larger over the dominant hemisphere, but surprisingly, it was larger over the minor hemisphere. The BP averaged -3.66 microV (S.D. 1.96) over the left precentral region and -4.82 microV (S.D. 3.73) over the right precentral region in this condition. The difference was significant at 2P less than 0.01. This difference was pronounced in precentral leads but very small and almost missing in parietal leads. The pre-motion positivity (PMP) was well developed and even larger with bilateral than with unilateral (right-sides) movements. At the vertex it averaged +1.33 microV (S.D.4.16) with bilateral movements and only +0.15 microV (S.D. 1.42) with right-sided unilateral movements (2P less than 0.05). With bilateral movements the PMP could be observed in any record, but with unilateral movements it was missing at the left precentral lead, in accordance with previous publications (Deecke et al. 1969, 1976). The motor potential (MP), measured in a bipolar record from left and right precentral leads, was larger with unilateral (-1.25 microV, S.D. 1.33) than with bilateral movements (-0.36 microV, S.D. 0.92). Onset time differences of the BP preceding unilateral and bilateral movements were very small. However, there was a tendency towards earlier onset with unilateral than with bilateral movements (1031 msec, S.D. 358, as compared with 951 msec, S.D. 305). The averaged EMG revealed differences in movement onset. Muscular contraction tended to be earlier in the right than in the left m. flexor indicis in our right-handed subjects, on the average by 16 msec (S.D. 15). With unilateral right-sided movements, the left m. flexor indicis was not silent but showed an abortive mirror activity in the EMG, without visible movement. This activity occurred on the average 50 msec (S.D. 39) later on the non-moving side.

Adult↗