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Biomedical subjects

L Deecke

Publications and source records attributed to L Deecke.

At least 199 records · Page 11Linked to original sources
PubMed1988

DC-potential shifts and regional cerebral blood flow reveal frontal cortex involvement in human visuomotor learning.

In the present study, two different physiological parameters were measured to describe brain activity related to visuomotor learning: performance-related DC-potential shifts and regional cerebral blood flow (rCBF) by Tc-99m HMPAO brain SPECT (Single Photon Emission Computerized Tomography). Visuomotor learning was required in a conflicting situation: a visual target moved on a screen and had to be tracked by moving the right hand in an inverted fashion (IT), e.g. movements of the target to the right side required hand movement to the left and vice versa. Compared to a normal, non-inverted control task (T), IT required the development of a novel motor program and the prevention of returning to routine direct pursuit. These additional demands in IT caused a relative hyperperfusion in regions including the middle frontal gyri, frontomedial cortex (including the supplementary motor area, SMA), right basal ganglia (caudate-putamen) and left cerebellum. Correlations of rCBF values between the middle frontal gyrus and basal ganglia may indicate a functional relation between these two brain structures. Visuomotor performance was accompanied by slow negative DC-potential shifts. In frontal and to a lesser degree in central recordings, amplitudes of DC-negativity were larger in IT than they were in T. This additional frontal negativity covaried with the success of learning. Results substantiate, now using a dual approach, previous suggestions that the frontal lobe plays an important role in visuomotor learning.

Adolescent↗
PubMed1988

Negative cortical DC shifts preceding and accompanying simultaneous and sequential finger movements.

Cortical DC shifts preceding and accompanying the execution of five different bimanual motor tasks were analysed in 20 subjects. All tasks required repetitive flexions and extensions of the two forefingers for a period of at least six seconds. The temporal and spatial structures organization varied in the different tasks: (1) Simultaneous agonistic performance (forefinger flexion on both sides), (2) simultaneous antagonistic performance (e.g. flexion of the right, extension of the left forefinger), (3) sequential agonistic performance, (4) sequential antagonistic performance, (5) uncoordinated flexions and extensions of the two forefingers. Compared to (1) and (2), conditions (3) and (4) included a temporal delay between the performance of the two forefingers; compared to (1) and (3), conditions (2) and (4) required the subjects to perform movements of opposite directions with their two forefingers. Effects of the temporal factor (T; simultaneous vs. sequential) and the spatial factor (S; agonistic vs. antagonistic) on cortical DC shifts were investigated. The voluntary initiation of each motor task was preceded by a Bereitschaftspotential (BP). The performance of the complex tasks (1-4) was accompanied by a slow negative DC potential shift (N-P). In general, the BP did not differ depending on the temporal or spatial structures of the tasks (1-4). However, amplitudes of N-P (i.e. during tasks) were influenced by the temporal factor with significantly larger amplitudes in sequential than in simultaneous tasks. This difference was not a global phenomenon in all recordings but was selectively found in the recordings over the fronto-central midline.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1988

Left frontal lobe in verbal associative learning: a slow potential study.

In the present experiment pairs of words had to be memorized. The words were either meaningful or meaningless. The experimental design compares conditions of preestablished learning (L-) with active learning (L+). The effects of these two factors, "semantic content (S)" and "learning (L)", on the slow potential shifts accompanying presentation and processing of the verbal material were tested. In the memorizing tasks, the two words were given in a fixed temporal sequence. A slow negative potential shift having a maximum in parietal leads emerged within the inter-stimulus-interval. Its amplitudes were larger in the learning tasks (L+) than in conditions of pre-established learning (L-). This difference of amplitudes may reflect different levels of attention: In L-, the second word could be anticipated, but not in the L+ tasks. After the presentation of the second item, learning tasks (L+) were characterized by a slow negative potential shift in the recordings of the left dorso-lateral frontal lobe. It is assumed that this potential shift may indicate an importance of the left frontal lobe in the elaborative encoding of verbal material.

Adult↗
PubMed1988

Single photon emission computerized tomography during and between seizures.

In three patients, patterns of brain activity were measured by 99mTc-hexamethyl-propyleneamineoxime (99mTc-HM-PAO) brain SPECT (single photon emission computerized tomography) in ictal and interictal states. Increased relative blood flow indicated the focus of partial seizures, its spreading to adjacent cortical regions and to distant brain structures via neuronal pathways. Ictal patterns of regional cerebral blood flow (rCBF) were in agreement with clinical symptomatology. Successive SPECT studies were performed after 3-7 days in the absence of electroencephalographic and clinical signs of seizures but still revealed increased relative blood flow in the focus of the seizures. SPECT studies, performed 2-6 weeks after the last clinically observable seizures, demonstrated the transition from increased to decreased relative blood flow in the focus of the seizures. In one patient, the EEG was complementary to and corresponded with the rCBF patterns in the ictal state. However, the dynamics of interictal changes could only be assessed by brain SPECT.

Adult↗
PubMed1988

Structural brain correlates of anterograde memory deficits in multiple sclerosis.

Progressive decline of anterograde memory functions has been increasingly recognized as a frequent symptom in chronic multiple sclerosis. In order to investigate the brain structures involved, magnetic resonance imaging was performed in 20 patients. Neuropsychological assessment included the WAIS and WMS subtests information, picture completion, similarities, digit span, logical memory, and paired associate learning. All patients with severely impaired memory functions (n = 5) showed bilateral lesions in the medial temporal lobe, whereas in those patients with moderate (n = 10) or no measurable impairment of memory testing (n = 5) either no lesions were seen in the medial temporal lobes or these lesions were restricted to one side. A post hoc cluster analysis strikingly confirmed these results. The differences could not be related to the age of the patients, the disease duration, or the level of education. Extensive lesions in the white matter of the frontal lobes, thinning and lining of the corpus callosum, and bilateral involvement of the anterior cingulate gyrus had no bearing on the neuropsychological results. These findings indicate that bilateral demyelination in the hippocampal regions is the most likely explanation for the impairment of anterograde memory in such patients.

Adult↗
PubMed1988

Hexa-methyl-propylene-amine-oxime (HMPAO) single photon emission computed tomography (SPECT) in epilepsy.

Twenty-eight normal volunteers and 74 seizure patients were investigated with hexa-methyl-propylene-amine-oxime (HMPAO) brain single photon emission computed tomography (SPECT). Fifty-four patients suffered from partial seizures and 20 patients had generalized seizures. Indices describing regional tracer distribution (RIs) were calculated in all investigated subjects. Regions whose RI exceeded the mean normal RI +/- 3 SD were defined as abnormally perfused. In normals a significant interhemispheric asymmetry of HMPAO deposition was found, with higher RI values in the right frontal, parietal, temporal and occipital regions. In 59.3% of partial seizure patients abnormal RIs were found. Low RIs were detected predominantly in the frontal and temporal cortex, while elevated RIs were observed predominantly in the anterior basal ganglia. Only in 20% of the cases with generalized seizures, abnormal RIs were found. In one patient an ictal and 3 follow-up SPECT studies were obtained. Here SPECT results indicated transient rCBF changes between the ictal and seizure free state. EEG and SPECT foci were ipsilaterally located in 69.2% of the partial seizure cases. The results indicate that HMPAO brain SPECT is valuable for the detection of rCBF abnormalities in seizure patients and that patients with partial seizures have mostly several abnormally perfused areas in their brains.

Adult↗
PubMed1988

Cortical slow potentials in verbal and spatial tasks--the effect of material, visual hemifield and performing hand.

Fifteen right-handed students voluntarily initiated the tachistoscopic presentation of visual stimuli containing either verbal (abstract words) or spatial (stereogeometric figures) material. Subjects had to reproduce stimulus material which had been presented either in their right or their left hemifield of vision by writing or drawing, either with their right or their left hand. Material-specific effects were found during the reproduction period: amplitudes of the performance-related negative potential shifts were larger in parietal and occipital recordings (P4, O1, and O2) when drawing as compared to writing. The opposite was true in frontal and left central leads (F3, F4, and C3) where writing was associated with larger negative amplitudes than drawing. Although subjects were informed about the nature of the forthcoming stimulus before voluntarily initiating the task, material-specific effects were missing in the preparation period. The performing hand had an influence on potentials in central leads, whereas hemifield of vision had no effect on preparation- and performance-related slow potential shifts.

Adolescent↗
PubMed1988

Is aphasia an additional prognostic factor in ischemic stroke with regard to the severity of hemiparesis in the subacute stage?

The outcome of 122 patients with ischemic stroke in the left carotid territory (ascertained by CT) was investigated using mailed questionnaires after a mean follow-up time of 60.7 months (SD 20.5 months). Patients who had had cerebrovascular accidents others than TIA prior to the stroke were not included in the study. The relationship between the degree of aphasia in the postacute stage and the long-term outcome was evaluated with regard to the severity of motor deficits. With respect to survival, recurrent stroke, single activities of daily living such as dressing, personal hygiene, walking, feeding, bowel management and overall self-care status, the outcome of patients was not dependent on the severity of aphasia. Aphasia did also not serve as a prognostic factor in returning to work after left hemispheric cerebral infarction. Our results indicate that in presence of motor deficits the severity of aphasia in the subacute stage does not additionally influence the long-term outcome after left hemispheric cerebral infarction.

Activities of Daily Living↗
PubMed1988

Topographic brain mapping of EEG before and after open-heart surgery.

The brain function of 60 patients undergoing open-heart surgery (36 patients receiving coronary artery bypass, 21 patients valve replacements, 3 both) was investigated before and 10 days after the operation utilizing topographic brain mapping of the electroencephalogram (EEG). The postoperative EEG changes were characterized by a slight delta-theta increase, an alpha decrease [especially in the fast alpha (10.5-13 Hz) band] and a beta increase in the relative power. The total power and the absolute power of the delta-theta, alpha and beta showed a decrease, the dominant frequency a significant slowing from 9.7 to 9.3 Hz. The centroid of alpha and beta activity decreased as well. These results are similar to findings obtained in patients with organic brain syndrome. The EEG changes were prominent over the left hemisphere, which may be of particular clinical relevance.

Adult↗
PubMed1988

[Visual evoked potentials as affected by different modes of stimulation].

VEP with 3 different modes of stimulation (pattern-reversal, flash and light-emitting diodes = LED) were performed in 30 subjects with normal vision. Normal values were established and the main components were compared under these 3 conditions of stimulation. The latencies of the main components showed a normal distribution in pattern-reversal and flash stimulation mode, but not in LED stimulation modes. The latency of the main component P2 of pattern reversal stimulation mode as well as the amplitude showed the smallest variance; flash and LED stimulation mode had a longer latency of the main component than pattern reversal stimulation mode. No sex or side differences were observed. In one subject (3%) the main component (P2) of pattern-reversal stimulation mode had a W-form, in LED stimulation mode 63% and in flash stimulation mode 40% of the subjects showed a W-form of the main component. The main component (P2) of pattern-reversal stimulation mode was best correlated with the first component of a W-from in flash and LED stimulation mode. Therefore, from one latency value (LED or flash stimulation mode) a latency value of pattern reversal stimulation mode may be estimated.

Adult↗
PubMed1988

[Prognosis of social reintegration following stroke].

From the socio-economic point of view, early prediction of outcome after stroke is of essential value. The longterm prognosis of 310 patients suffering from ischemic stroke, was therefore investigated by means of questionnaires. The mean follow-up period was 62.5 (S.D. 21.9) months. The results of patients who had suffered cerebrovascular accidents other than ischemic stroke or only transient ischemic attacks were not included. It had been the aim of the study to determine the predictive value of some clinical variables and symptoms in the subacute stage as regards the familial and social functioning handicaps to be expected later on. Between the number of strokes as well as the severity of some clinical signs (motor deficits, sensory deficits, speech disorders, organic mental syndrome) on the one hand, and the restrictions experienced in familial functioning on the other hand, a clear cut correlation was found. As regards social functioning, two additional predictors of unfavourable outcome could be identified: age, and lesion within the left hemisphere. The findings indicate that some clinical variables and symptoms in the subacute stage are of great predictive value concerning the ensuing handicap in familial and social functioning. These variables may help to develop individual strategies as regards the further social management and support (e.g. discharge arrangements, care services, rehabilitation programs).

Adolescent↗
PubMed1987

[Reversible opening of the blood-brain barrier in the chemotherapy of malignant gliomas].

The concept of a blood brain or blood tumour barrier blocking the passage of lipid insoluble cytoreductive drugs from blood into brain-tumor, leads to a protocol of intraarterial injection of high dose methotrexate (MTX) during reversible, osmotic blood brain barrier disruption (BBBD). Malignant Gliomas of grades III and IV in 9 patients and one primary CNS-lymphoma in one patient have been treated in 2 to 5 sessions per patient with BBBD plus polychemotherapy (MTX, cyclophosphamide, procarbazine). Median progression free intervals (PFI) which are still in continuation are 12.2 months. Median PFI which had been terminated by tumour recurrence are 7.75 months.

Antineoplastic Agents↗
PubMed1987

Bereitschaftspotential as an indicator of movement preparation in supplementary motor area and motor cortex.

Topographical studies in humans of the Bereitschaftspotential (BP, or readiness potential, as averaged from the electroencephalogram) and the Bereitschaftsmagnetfeld (BM, or readiness magnetic field, as averaged from the magnetoencephalogram) revealed a widespread distribution of motor preparation over both hemispheres even before unilateral movement. This indicates the existence of several generators responsible for the BP, including generators in the ipsilateral hemisphere, which is in agreement with measurements of regional cerebral blood flow or regional cerebral energy metabolism. Nevertheless, two principal generators seem to prevail: (1) An early generator, starting its activity 1s or more before the motor act, with its maximum at the vertex. For this and other reasons, early BP generation probably stems from cortical tissue representing or including the supplementary motor area (SMA). (2) A later generator, starting its activity about 0.5s before the onset of movement and biased towards the contralateral hemisphere (contralateral preponderance of negativity, CPN). For unilateral finger movements the CPN succeeds the BP's initial bilateral symmetry in the later preparation period. Thus, this lateralized BP component probably stems from the primary motor area, MI (area 4, hand representation). While regional cerebral blood flow or regional cerebral energy metabolism show that the SMA is active in conjunction with motor acts, these data do not permit the conclusion that SMA activity precedes motor acts. This can only be shown by the Bereitschaftspotential, which proves that SMA activity occurs before the onset of movement and, what is more, before the onset of MI activity. This important order of events (first SMA, then MI activation) has been elucidated by our BP studies. It gives the SMA an important functional role: the initiation of voluntary movement. The recording of movement-related potentials associated with manual hand-tracking and motor learning points to the SMA and frontal cortex having an important role in these functions.

Action Potentials↗
PubMed1987

Unilateral stenosis of the vertebral artery--secondary finding with no prognostic relevance?

The outcome of 142 patients suffering from ischemic cerebral circulation disorders was followed up over a period of 33 months on average. The spontaneous course of 25 patients with unilateral, hemodynamically ineffective stenoses of the vertebral artery was compared with that of 107 patients without vertebral artery stenoses. Within the first 12 months, novel clinically manifest cerebrovascular events were observed in 16.0% of patients without vertebral artery stenosis (deaths 5.0%), but in only 4.3% of the patients with vertebral artery stenosis (no deaths). Within 30 months, only 2 of the 13 patients with vertebral artery stenosis had suffered a new cerebrovascular attack. At the end of the observation period, 39.3% of the patients without vertebral artery stenosis and 48.0% of the patients with vertebral artery stenosis were significantly disabled in their social life or had died. An additional unilateral hemodynamically irrelevant vertebral artery stenosis did not influence the rate of reinfarction or the remission of neurological deficits, independently of age, the degree of the circulatory disorder, the vascular territory involved, the presence of an organic psychosyndrome, or of additional stenoses in the carotid arteries. Consequently, a vertebral artery stenosis narrowing the vessel diameter to less than 1/3 is without prognostic relevance.

Carotid Artery Diseases↗
PubMed1987

Bereitschaftspotential in patients with unilateral lesions of the supplementary motor area.

In the present study, an attempt was made to examine the sensitivity of the Bereitschaftspotential (BP) preceding simple finger movement in revealing pathophysiological patterns of premovement cortical activity in patients with chronic unilateral lesions of the supplementary motor area (SMA). Usually, in healthy subjects, BP has a clear maximum in Cz with larger amplitudes than in Ccon (located over the motor cortex, contralateral to the performing hand). In the patients, amplitudes did not differ between Cz and Ccon. This effect of the lesion on BP topography, was found in movements of either side. However, intraindividual comparisons revealed that the reduction of the BP in Cz (relative to Ccon) was larger for movements contralateral to the SMA lesion than for those ipsilateral of it.

Brain Diseases↗
PubMed1987

Slow negative potential shifts indicating verbal cognitive learning in a concept formation task.

It is well-known clinically that patients with left frontal lesions are impaired in their verbal-cognitive learning ability. Starting from such observations, it is of particular interest whether the event-related cerebral potential shifts recorded in healthy human subjects would indicate a left frontal lobe involvement in verbal-cognitive learning tasks. In a concept formation paradigm, subjects learned by trial and error to transform letters into Morse codes. This cognitive performance was accompanied by a slow negative potential shift (SP) that in frontal recordings was lateralized towards the left hemisphere. off results show in a later stage of learning, in which the experience of the preceding trial and error learning could be integrated, an increasing slow negativity over the frontal cortex. Ss also participated in a control task with already known letter/Morse code combinations. Again, a negative potential shift occurred within the stimulus-response interval, however, it was smaller in amplitude.

Adult↗