Library

feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Experimental brain research 128 (1999), S. 123-133 
    ISSN: 1432-1106
    Keywords: Key words Precision grip ; Context-dependency ; Force ; Finger representation ; Motor cortex ; Premotor cortex
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  In three monkeys trained to finely grade grip force in a visuomotor step-tracking task, the effect of the context on neuronal force correlates was quantitatively assessed. Three trial types, which differed in force range, number, and direction of the force steps, were presented pseudo-randomly and cued with the color of the cursor serving as feedback of the exerted force. Quantitative analyses were made on 85 neurons with similar discharge patterns in the three trial types and significant linear positive (54 cells) or negative (31 cells) correlation coefficients between firing rate and force. An analysis of covariance (ANCOVA) showed that the population slopes for 2-step were steeper than for 3-step trials. Another ANCOVA at the population level, computed on the differences in firing rate and force between force steps, persistently disclosed a significant effect of trial type. For the first two force steps, the differences in firing rate were significantly larger in the 2-step than in the 3-step increase trials. Further analyses revealed that neither the force range nor the number of steps was a unique factor. A small group of neurons was tested in an additional trial series with a uniform cue for all three trials, leading to either a loss of context-dependency or to unexpected changes in firing rate. This demonstrates that the cue color was an important instruction for task performance and neuronal activity. The most important findings are that the context-dependent changes were occurring ”on-line”, and that neurons displaying context-dependency were found in all three lateral premotor cortex hand regions and in the primary motor cortex. Finger muscle activity did not show any context dependency. The context-dependent effect leads to a normalization of the cortical activity. The advantage of normalization is discussed and mechanisms for the gain regulation are proposed.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 2
    ISSN: 1432-1106
    Keywords: Pyramidotomy ; Reaction time ; Precision grip ; Monkey
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Two monkeys (Macaca fascicularis) were trained to perform fast conditioned fingergrip on a small transducer. When performance was stabilized to the shortest possible reaction time, the pyramidal tract was transected on one side in one monkey, bilaterally in another. Retraining was resumed 1–3 weeks after surgery. Response latency as well as electromyographic latency and summation time were measured before and up to several months after pyramidotomy. The data show that pyramidotomy induced a long-lasting slowing in the performance of the fingergrip. This slowing was due mainly to a delay in the execution of the movement. However, a short-lasting significant delay of the onset of the EMG activity preceding the movement shows that not only the execution but also the initiation contributes to the increase of the mean response latency. The deficits were more severe and of longer duration in the monkey with bilateral pyramidotomy, especially the delay in the onset of the EMG activity. The mechanisms underlying these deficits and the role of the pyramidal tract in rapid movements are discussed, specifically in consideration of the possible function of the ipsilateral pyramidal tract.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Experimental brain research 41 (1981), S. 358-363 
    ISSN: 1432-1106
    Keywords: Eye movements ; Saccade ; Coordinate remapping ; Auditory localization ; Eye-head coordination
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Three adult female monkeys were trained to direct their gaze toward auditory targets. When the animals were free to move their heads about the vertical axis, this was accomplished with shortlatency, coordinated eye-head movements reminiscent of responses to visual targets. The similarity of response to auditory and visual targets suggests a common motor program elicited by stimuli of different modalities. Since these modalities do not share the same reference system, this implies a remapping between the two reference systems.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Experimental brain research 63 (1986), S. 567-580 
    ISSN: 1432-1106
    Keywords: Monkey ; Isometric force ; Finger ; Neuronal activity ; Thalamus ; Precentral cortex
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The relationship between single cell activity in the “motor” thalamus and the generation of isometric force between the fingers has been investigated in 2 monkeys. Neurons related to the task were found in the thalamic motor regions VLo, VPLo, and VA where microstimulation occasionally elicited motor reactions in hand and fingers. 58% of these 55 neurons, designated “typical”, showed modulation of their discharge patterns with force similar to neurons in precentral cortex and could be assigned to one of 5 discharge patterns described for the motor cortex. Only a small percentage of the thalamic neurons were found to have phasic activity. The other “atypical” neurons (42%) had discharge patterns with complex sequences of phasic and tonic activation with respect to force. For 18 typical and atypical neurons with tonic and phasic-tonic modulation of their firing rate with force significant regression coefficients between firing rate and static force were observed. The mean index of force sensitivity (rateforce slope) was 54.5 Hz/N for the neurons increasing their discharge rate with force, i.e. approximately that of precentral cells. Neurons tested for their sensory properties had receptive fields located on hand and/or fingers and were activated mainly by stimulation of muscle and joint receptors. The characteristics of these thalamic neurons are compared to those of precentral cells recorded under identical experimental conditions and are discussed in relation to the known input-output relationships of the motor thalamic nuclei. The data strongly support the hypothesis that parameters of movement, in particular force, are represented by the activity of neurons in the “motor” thalamus.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 5
    ISSN: 1432-1106
    Keywords: Precentral motor cortex ; Unit recording ; Isometric precision grip ; Force and rate of force change ; Microstimulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The activity of single neurons within the hand area of the precentral motor cortex of primates was recorded during the performance of a maintained precision grip between the thumb and forefinger. The finger opposition forces were exerted against a strain gauge which allowed force changes to be studied under near isometric conditions. Task performance required the generation of a force ramp (the dynamic phase) and thereafter the maintenance of a stable force for one second (the static phase). Intracortical stimulation through the recording electrode was used to verify that the recordings were made from the appropriate somatotopographic area of the motor cortex. From a total of 221 recorded neurons, 76 were found to be either activated or deactivated during performance of the task. Among the 51 activated neurons, most discharged at higher frequencies during the dynamic phase, than during the static phase. The discharge of some of these neurons could be related to both force (F) and rate of force change (df/dt) whereas certain others could only be correlated with df/dt. The change in discharge frequency for these neurons generally occurred prior to the onset of EMG activity. Eight neurons were more active during maintained force than during the force ramp. The discharge frequency could not be correlated with df/dt and only one showed a significant positive relation to force. The change in discharge frequency for these neurons either coincided or occurred after the onset of EMG activity.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 6
    ISSN: 1520-4804
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Der Chirurg 68 (1997), S. 215-224 
    ISSN: 1433-0385
    Keywords: Key words: Laparoscopic colorectal surgery ; Port site metastases ; Pitfalls of laparoscopy. ; Schlüsselwörter: Laparoskopische colorectale Chirurgie ; Port-site-Metastasen ; Onkologische Fehler bei der Laparoskopie.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung. Die onkologischen Probleme bei laparoskopisch colorectalen Eingriffen in kurativer Intention bestehen im Auftreten von Port-site-Metastasen, in einer inadäquaten Radikalität, einer Tumorzellverschleppung durch ungeschützte Präparatebergung und unzureichende Operationstechnik sowie Nichtbeachtung technisch-onkologischer Grenzen bei bestimmten Tumorlokalisationen. Die bisher vorliegenden Untersuchungen ergeben eine mehr mechanische Pathogenese der Port-site-Metastasen durch Verschleppung von Tumorzellen in die Trokareinstichstellen über Instrumente, Trokare und Resektionspräparate. Durch entsprechende Vorsichtsmaßnahmen scheint somit eine Vermeidung möglich. Das CO2-Pneumoperitoneum spielt anscheinend eine untergeordnete Rolle bei der Entstehung der Port-site-Metastasen. Die onkologische Radikalität laparoskopischer Eingriffe beim colorectalen Carcinom kann bei fehlenden Langzeitdaten zur Zeit nicht beurteilt werden. Es liegen lediglich vereinzelte Untersuchungen zur Zahl der bei den Eingriffen mitentfernten Lymphknoten vor. Die Anzahl scheint nicht die bei vergleichbaren offenen Resektionen zu erreichen, eine genauere Analyse müßte jedoch die selektionierten Indikationen nach Tumorgröße und -lokalisation berücksichtigen. Die Vielzahl der möglichen Fehler und Gefahren der onkologischen laparoskopischen Chirurgie führt zu der klaren Forderung, daß die Eingriffe nur innerhalb von prospektiven klinischen Studien mit selektionierten Indikationen erfolgen sollten. Eine prospektiv randomisierte Studie für alle Tumorstadien und -lokalisationen ist vor diesem Hintergrund kritisch zu werten.
    Notes: Summary. Oncological problems associated with laparoscopic colorectal surgery with curative intent include port site metastases, inadequate radicality, seeding of tumour cells through unprotected recovery of the surgical specimen, faulty surgical technique, and failure to observe the technical and/or oncological limitations applicable to certain tumour sites. Investigations so far reported reveal a preponderance of mechanical pathogenesis of port site metastases caused by the contamination of trocar entry ports by tumour cells borne on instruments, trocars and resected material. This suggests that appropriate precautionary measures could resolve the problem. It appears that the CO2 pneumoperitoneum plays only a minor role in the development of port site metastases. Owing to a lack of long-term data, the oncological radicality of laparosopic resections for colorectal carcinoma cannot be assessed; merely a few reports on the number of lymph nodes removed during such operations have been published. Nevertheless, it would appear that fewer lymph nodes were removed than with comparable conventional surgery. However, a more accurate analysis needs to take account of the fact that the indication for laparoscopic surgery is determined by the size and location of the tumour. The many potential pitfalls and hazards of oncological laparoscopic surgery make it mandatory that such interventions should be done only within the framework of prospective clinical studies covering limited indications. Randomized prospective studies to cover all tumour stages and sites cannot be recommended.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Experimental brain research 86 (1991), S. 209-215 
    ISSN: 1432-1106
    Keywords: Eye ; Head ; Arm ; Coordination ; Gaze ; Rotatory synergy ; Reaching ; Human
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary We have recorded eye, head, and upper arm rotations in five healthy human subjects using the three-dimensional search coil technique. Our measurements show that the coordination of eye and head movements during gaze shifts within ± 25 deg relative to the forward direction is organized by restricting the rotatory trajectories of the two systems to almost parallel planes. These so-called “Listing planes” for eye-in-space and head-in-space rotations are workspace-oriented, not body-fixed. Eye and head trajectories in their respective planes are closely related in direction and amplitude. For pointing or grasping, the rotatory trajectories of the arm are also restricted to a workspace-oriented Listing plane. During visually guided movements, arm follows gaze, and the nine-dimensional rotatory configuration space for eye-head-arm-synergies (three degrees of freedom for each system) is reduced to a two-dimensional plane in the space of quaternion vectors.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 9
    ISSN: 1359-5997
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 10
    ISSN: 1432-2218
    Keywords: Key words: Anastomotic leakage — Laparoscopic colorectal surgery — Multicenter study
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Background: We report on a prospective observational multicenter study of more than 1,000 consecutive patients undergoing laparoscopic colorectal procedures. The aim of the current study was to investigate the safety of laparoscopic colorectal surgery as reflected by the anastomotic insufficiency rates in the various sections of the bowel, and to compare these rates with those of open colorectal surgery. Methods: The study was begun on August 1, 1995. Twenty-four centers in Germany, Austria, and Switzerland participated in this prospective multicenter study. All patients undergoing laparoscopic colorectal surgery were included in the study. No selection criteria were applied, which means that every operation begun as a laparoscopic procedure was included. Data on patient demographics, surgical indications, surgical course, and patient outcome were recorded prospectively in a computer database. All data were rendered anonymous. Results: Between August 1995 and February 1998, the 24 participating centers treated 1,143 patients (male/female ratio, 1:1.36; mean age, 60.7 years). In all, 626 operations were performed for benign indications and 517 for cancer. Most procedures involved the sigmoid colon and rectum (80.9%). An anastomosis was performed in 83% of the operations. Most of the anastomoses were laparoscopically assisted using the stapling technique. We observed an overall leakage rate of 4.25% (colon 2.9%; rectum 12.7%), and surgical reintervention was required in 1% of the cases. The rate of conversion to open surgery was 5.6%. Intraoperative complications occurred in 5.9%, and reoperation was necessary in 4.1% of the cases. The overall morbidity rate was 22.3%, and the 30-day mortality rate was 1.57%. Conclusions: The feasibility and safety of the laparoscopic colorectal approach is demonstrated clearly. The current study shows that the laparoscopic or laparoscopically assisted approach to colorectal surgery is not associated with a higher risk of anastomotic leaks. Morbidity and mortality rates with this method approximate those seen with conventional colorectal surgery.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...