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Biomedical subjects

L Deecke

Publications and source records attributed to L Deecke.

At least 217 records · Page 12Linked to original sources
PubMed1987

Initial experience with technetium-99m HM-PAO brain SPECT.

Technetium-99m hexamethylpropyleneamineoxime ([99mTc]HM-PAO) brain single photon emission computed tomography (SPECT) was performed with a dual head rotating scintillation camera. Normal tracer distribution and side/side differences of counting rates were obtained in 11 healthy volunteers. Almost stable gray/white matter ratios were found (1.97-2.1) in one normal subject during 2 hr after tracer administration. Eighty-three investigated patients had the following diagnoses (in parentheses is percent of positive findings in each group): cerebral vascular disease 18 (94.4%), epilepsy 23 (82.6%), extrapyramidal disorders 8 (100%), dementia 12 (100%), headache 11 (63.6%), psychiatric disorders 11 (27.3%). In addition, SPECT was performed in 28 male volunteers during motor or visual imagery tasks and a significant increase (p = 0.035) of relative tracer deposition was observed in the left inferior occipital region during visual imagery when compared with motor imagery. The results indicate that [99mTc]HM-PAO SPECT is valuable for demonstrating pathologic and physiologic changes of the brain.

Adult↗
PubMed1986

Cerebral potentials preceding voluntary toe, knee and hip movements and their vectors in human precentral gyrus.

In this study, the brain potentials related to voluntary, self-paced plantarflexions of the left toes, flexion of the right knee and isometric extensions of the left hip were examined in 3 groups of 10 subjects each. In the first half of the foreperiod, the Bereitschaftspotential (BP) or readiness potential for all movements was symmetrically distributed over both hemispheres. For toe and knee movements, an ipsilateral preponderance of the BP developed in the later foreperiod, which was statistically significant for toe movements. For hip movements, BP topography was symmetrical during the entire foreperiod including its second half. Since finger, hand or shoulder movements of previous experiments show a strong contralateral preponderance of the BP, the results are discussed as further support of the hypothesis that the lateralisation of the BP is due to the orientation of the precentral electrical field vector generated by an active source in the MI motor cortex. Thus, part of the somatotopic representation of the human precentral gyrus can be mapped by this non-invasive means: upper limb movements are located on the convexity; toe, foot and knee movements are generated on the mesial cortex between the hemispheres; and hip movements seem to be located at the mantle edge.

Adolescent↗
PubMed1986

[Status of oral contraceptives as a risk factor in cerebrovascular diseases].

A critical review of the relevant literature revealed that the incidence of subarachnoid haemorrhage is increased in women taking oral contraceptives and the mortality rate is higher. The data concerning correlation between the use of oral contraceptives and other cerebrovascular disorders are less conclusive. Taking oral contraceptives seems to result in a higher risk of stroke, but there is no definite correlation to the incidence of strokes with a fatal outcome. However, in the case of the coexistence of more than one risk factor, including cigarette smoking, the risk of cerebrovascular disease is considerably increased for women using oral contraceptives. Age also seems to be a significant factor. Women older than 44 should avoid oral contraceptives in general; women between 35 and 44 should use oral contraceptives only if additional risk factors are absent, i.e. if they are non-smokers. Indeed, in the presence of this or other risk factors younger women should also avoid taking oral contraceptives.

Adult↗
PubMed1986

Bereitschaftspotential preceding speech after holding breath.

Cerebral potentials prior to speaking were recorded in 36 healthy righthanded subjects. Subjects began holding breath at irregular intervals prior to the voluntary onset of speech. This was done in order to avoid respiration-related potential shifts. The Bereitschaftspotential (BP) or readiness potential started already 2 s prior to the onset of speaking and was present over either hemisphere. During the last 100 to 200 ms of preparation period, the BP became significantly lateralized towards the left hemisphere. The close temporal relation to speech onset characterized this hemispheric lateralization to be an indicator of the final motor mechanisms for speech. Still, the BP was a bilateral phenomenon, i.e. it was also present over the right hemisphere, indicating involvement of the non-dominant hemisphere as well. The data are compatible with the view of an early bihemispheric motor preparation for speech followed by a late left hemisphere preponderance as the final common pathway.

Adult↗
PubMed1986

Blood brain barrier modification and chemotherapy. Interventional neuroradiology in the treatment of malignant gliomas.

Postoperative interventional neuroradiology was performed in patients with malignant gliomas to increase target efficacy of chemotherapy. In 8 glioma patients the blood brain or blood tumor barrier was reversibly opened by intraarterial injection of hyperosmolar fluid (Mannitol 25%). One additional patient had primary lymphoma of the central nervous system. During barrier modification chemotherapeutic agents were applied intraarterially and intravenously. A total of 22 blood brain barrier modification procedures have been carried out until now, ranging from one to five per patient. A presently continuing tumor regression or tumor progression free intervals have been noted in 5 patients. Therapeutic effects are being evaluated from repeated computed tomography and single photon emission computed tomography examinations.

Adult↗
PubMed1986

Handedness, footedness and finger and toe movement-related cerebral potentials.

Sixteen right-handed and 16 left-handed subjects were compared with respect to their foot dominance and the topography of their pre-movement cerebral potentials (Bereitschaftspotential, BP). First, righthanders were usually also found to be right-footed. Lefthanders showed a similar trend in preferring their left foot. Second, the BP prior to volitional self-paced movements of fingers and toes on either side was examined. For finger movements, the BP always showed higher amplitudes over the contralateral hemisphere as compared to the ipsilateral one (contralateral preponderance of negativity, CPN). For toe movements a significant ipsilateral preponderance of negativity (IPN) occurred in all subjects. The CPN was larger for finger movements of the dominant hand than it was for finger movements on the non-dominant side. By contrast, the IPN was larger prior to movements of the "non-dominant toes" than it was for movements of the dominant toes. This can be explained by assuming that the hemisphere contralateral to the dominant hand, generates more negativity than the one contralateral to the non-dominant hand. This assumption is further discussed in the context of a vector model for the BP.

Adolescent↗
PubMed1985

Canal-neck interaction in vestibular neurons of the cat's cerebral cortex.

Interaction of semicircular canal and neck proprioceptive inputs was studied in the cerebral cortex of awake, intact cats. Neuronal responses were recorded extracellularly in the anterior suprasylvian gyrus of the left hemisphere. Stimulations consisted of horizontal rotations in the dark applied as sinusoids or position ramps. There were three stimulus conditions: (1) Pure canal stimulation; rotation of whole body. (2) Pure neck stimulation; rotation of trunk about stationary head. (3) Canal-neck interaction; rotation of head about stationary trunk. We recorded 105 neurons with either Type I or Type II canal response. These showed often pronounced non-linearities such as a clear firing increase upon rotation in the "on-direction" and hardly any decrease in the opposite direction. The responses reflected mostly angular velocity, but angular position signals were also obtained. In 79 neurons, either Type I or Type II neck responses were obtained. They coded either angular velocity, velocity plus position, or position. Canal-neck convergence was found in 67 of 88 neurons tested. In the majority of neurons, interaction was "antagonistic" in the sense that the canal and neck responses tended to cancel each other during rotation of the head about the stationary trunk. These neurons could signal trunk rotation in space rather than head in space or head relative to trunk. Most of the remaining neurons showed a "synergistic" interaction such that the response upon head rotation was enhanced as compared to whole body or trunk rotation. These neurons might be involved in the dual task of monitoring head rotation in space and relative to trunk. Interaction was compatible with linear summation of canal and neck inputs in 70% of the neurons. In part of these, however, the assumption had to be made that the interaction had taken place already at some stage prior to the cortical neurons investigated. The response characteristics of cortical canal neurons are discussed in comparison to vestibular nuclear neurons. Furthermore, parallels are drawn between the observed canal-neck interactions in the cortical neurons and (i) interactions of canal and neck dependent postural reflexes in the decerebrate cat, and (ii) interactions of canal and neck induced turning sensations in man.

Animals↗
PubMed1985

Timing function of the frontal cortex in sequential motor and learning tasks.

The timing aspects of human frontal lobe function are discussed in the light of the results of three experiments on movement-related cerebral potentials. Experiment I is based on use of a sequential tracking task and experiment II a motor learning task; experiment III deals with frontal hemispheric specialisation by comparing self-initiated writing and drawing. The Bereitschaftspotential (BP) preceding voluntary movement is maximum over the supplementary motor area (SMA) for all movements, including finger, toe, speech, and eye movements, regardless of each movement's different localisation in the brain, e.g., motor cortex, temporal lobe, or midbrain. The assumption that all motor events are governed by the primary (rolandic) motor cortex is erroneous. The motor system is widely decentralised. It is only when this decentralization is recognized that the close temporal association between the onset of all movements and the preceding Bereitschaftspotential in the SMA can be understood. A plausible explanation would be that the SMA decides on the starting time of all the various movements. The frontal function of motivation is not a single entity but has several subfunctions. It has to decide what to do, how to do and when to do. The latter is probably the task of the SMA. A comparison of different motivational situations makes this clear. In the usual BP paradigm, such as self-initiated simple finger or eye movements, only the SMA becomes active among all the frontal areas. If, however, motivation is required to modify motor programs in motor learning, as it is in experiment II, the entire convexity of the frontal lobe shows a large surface-negative potential, the amplitude of which reveals a significant positive correlation with the success in learning. On the other hand, in experiment I, which uses a manual pursuit-movement task requiring attention to unpredictable changes in stimulus direction but providing a fixed time for these changes (so that their timing is foreseeable), the SMA shows anticipatory behaviour; it takes the form of a large negative potential which ceases 0.5 s prior to the end of the directed-attention potential over parietooccipital areas. In other words, in this special situation, where the SMA can anticipate the onset of movement, it seems to delegate the final execution of the movement to the cortical area most specialised for it, in this case the parietooccipital cortex. The supervision of the tasks concerning what to do and how to do may be provided mainly by the orbital cortex and the frontolateral cortex, respectively (Kleist 1934).(ABSTRACT TRUNCATED AT 400 WORDS)

Cerebral Cortex↗
PubMed1984

Brain potentials related to voluntary hand tracking, motivation and attention.

While there are many behavioural studies available investigating human hand tracking performance, there are none that include recording of cerebral potentials. Sixteen subjects tracked a visual or a tactile target by moving a stylus with their right hand. They voluntarily started the stimulus, which moved for 1 s in a first random direction, then for 1's in another direction. The stimulus was given to the left field of vision or tactually to the left palm. Tracking was compared to no-tracking controls. The voluntary initiation was preceded by a Bereitschaftspotential (BP), the change in direction by a contingent negative variation (CNV). Both BP and CNV showed a characteristic right hemispheric parietooccipital (visual task) or centro-parietal asymmetry (tactile task) due to the attention paid to the expected stimulus event ("directed attention potential", DAP). While the DAP outlasted stimulus onset by 0.2 s, fronto-midline areas switched already to positivity 100 ms prior to stimulus onset and more than 300 ms prior to the change in direction. Large P300-like components were elicited by stimulus onset and change in direction.

Attention↗
PubMed1983

Finger movement versus toe movement-related potentials: further evidence for supplementary motor area (SMA) participation prior to voluntary action.

The cerebral potentials associated with voluntary, self-paced rapid flexions of (1) right fingers, (2) left fingers, (3) right toes, and (4) left toes were compared in the same experiment using 32 right- and left-handed subjects. The Bereitschaftspotential (BP) or readiness potential was, in the first half of the foreperiod, bilaterally symmetrical for both finger and toe movements of either side. In the later foreperiod there were differences: Finger movements showed two maxima, an early one at Cz and a late one, which was lateralized toward the contralateral precentral region. With toe movements, the maximum BP amplitude was always at Cz and not lateralized and was twice as large as with finger movements. The data are compatible with the view that two principal sources of different spatial and temporal characteristics are active in the foreperiod of a voluntary movement. The early generator is probably the supplementary motor area (SMA) on the mesial surface of the hemispheres; the later is the primary motor cortex (MI) which is lateralized for finger but not for toe movements. In lateral leads, rather remote from the mesial source, the BP for toe movements showed a small but significant ipsilateral preponderance, which is obviously due to the fact that dipole sources located on the mesial surface of the hemispheres point to the opposite direction as compared to those on the convexity.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1983

Magnetic fields of the human brain (Bereitschaftsmagnetfeld) preceding voluntary foot and toe movements.

Voluntary movements are preceded by a slow electrical potential of the brain (Bereitschafts-potential, BP) or readiness potential. The BP is accompanied by a magnetic field shift of similar time characteristics (Bereitschaftsmagnetfeld, BM). The BM preceding volitional right foot or toe movements was recorded from anterior, posterior, and lateral positions of the scalp using a SQUID (Superconducting Quantum Interference Device) third-order gradiometer. Controls were implemented to reduce head movements, which were simultaneously recorded with a mechanograph. The results showed that movements of the lower extremities are also preceded by a BM. However, contrary to finger movements, BMs with field lines directed into the head were found predominantly for foot movements and exclusively for toe movements. The BM preceding foot movements was maximum over a position 2 cm left of the vertex, i.e., contralateral to the movement. Two centimeters right of the vertex it was smaller, thus exhibiting a normal contralateral preponderance and not sharing the paradoxical side preponderance of the electrical BP preceding foot or toe movements. The BM preceding toe movements was only apparent at the vertex and was smaller than the one preceding foot movement. This may suggest a source that is located still deeper in the brain than with foot movements.

Brain↗
PubMed1983

The role of canal-neck interaction for the perception of horizontal trunk and head rotation.

The present report considers the conscious perception of passive horizontal rotations of the trunk, the head, or both, by human observers. It examines in particular how this perception depends on the interaction of canal and neck afferents. Three sets of sinusoidal stimulations (0.2 Hz) were applied to subjects (Ss): Rotations of (1) whole body (pure labyrinthine stimuli, lambda), of (2) only the trunk with the head stationary in space (pure neck stimuli, nu), and of (3) both head and trunk, each with an amplitude and a direction of its own, giving rise to various in-phase and counter phase combinations of lambda and nu.--The Ss were to estimate the magnitude of their turning sensations (psi). In doing so, they were to concentrate either on the rotation of their trunk in space (TS) or of their head in space (HS), or of the head relative to the trunk (HT). The TS and HS turning sensations induced by pure lambda-stimuli were essentially the same as to magnitude and direction. Pure nu-stimulation also led to TS and HS turning sensations. However, the former had the direction of the trunk-to-head (T delta S) deflection, the latter that of the head-to-trunk deflection. The nu-induced HS turning sensation represented an illusion, since the head remained stationary in space. When the lambda- and nu-stimuli were combined, the interaction could be described by a linear summation of their effects. The estimates of TS turning followed the equation psi HS approximately lambda-nu, thus well reflecting the actual TS rotation. The estimates of HS could be described by psi HS approximately lambda+k nu; the term k nu represents the "nu-illusion" contaminating the HS turning sensation. The estimates of HT turning were roughly proportional to nu alone and, therefore, close to the actual HT rotation. We conclude that humans may derive a rather faithful information about trunk rotation from the combined activation of canal and neck afferents, but that the sensation of passive head rotation is contaminated by an (illusionary) contribution from neck afferents. These additive and subtractive modes of interaction have parallels in postural reflexes as well as in neuronal responses that are known from cat.

Adolescent↗