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  • 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
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  • 2
    ISSN: 1432-2218
    Keywords: Key words: Laparoscopic colorectal surgery — Multicenter study — Sigmoid diverticulitis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Background: In the large bowel, resection of the sigmoid colon is the most commonly performed laparoscopic intervention because large bowel lesions often are located in this part of the bowel and the procedure technically is the most favorable one. A number of publications involving case series or the results of highly experienced individual surgeons already have confirmed the feasibility of laparoscopic resection in cases of diverticulitis. The aim of the present prospective multicentric investigation was to check the results obtained by a large number of surgeons performing laparoscopic resection of the sigmoid colon for diverticulitis in various stages of severity. Results: Between January 8, 1995 and January 1, 1998, the Laparoscopic Colorectal Surgery Study Group recruited 1,118 patients to the prospective multicenter study. Diverticulitis of the sigmoid colon, which accounted for 304 cases, was the most common indication for laparoscopic intervention. In most of these patients undergoing laparoscopic surgery (81.9%), the diverticulitis manifested as acute phlegmonous peridiverticulitis, recurrent attacks of inflammation, or stenosis. Complicated forms of diverticulitis in Hinchey stages I to IV and late complications of chronic diverticular disease with fistula formation and bleeding accounted for only 18.1% of the cases. For the overall group, the conversion rate was 7.2%. Patients with less severe diverticulitis (i.e., those presenting with peridiverticulitis, stenosis, or recurrent attacks of inflammation) had a conversion rate of 4.8% and the rate for complicated cases was 18.2%. Regarding laparoscopically completed interventions, 3 of 282 patients died (1.1%). In the group of patients with peridiverticulitis, stenosis, or recurrent attacks of inflammation the overall complication rate was 14.8%. The group with perforated diverticulitis in Hinchey stages I to IV or those with fistula and bleeding, the corresponding rate was 28.9%, and after conversion it was 31.8%. Conclusions: Laparoscopic colorectal interventions in sigmoid diverticulitis are, for the most part, carried out as elective procedures for peridiverticulitis, stenosis, or recurrent attacks of inflammation. The conversion, complication, and mortality rates associated with these interventions are acceptable. Laparoscopic procedures in Hinchey stages I to IV sigmoid diverticulitis and in the presence of fistula and bleeding are more likely to be associated with complications, and should be carried out only by highly experienced laparoscopic surgeons.
    Type of Medium: Electronic Resource
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  • 3
    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
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