Dynamical computational properties of local cortical networks for visual and motor processing: a bayesian framework

A major unsolved question concerns the interaction between the coding of information in the cortex and the collective neural operations (such as perceptual grouping, mental rotation) that can be performed on this information. A key property of the local networks in the cerebral cortex is to combine thalamocortical or feedforward information with horizontal cortico-cortical connections. Among different types of neural networks compatible with the known functional and architectural properties of the cortex, we show that there exist interesting bayesian solutions resulting in an optimal collective decision made by the neuronal population. We suggest that thalamo-cortical and cortico-cortical synaptic plasticity can be differentially modulated to optimize this collective bayesian decision process. We take two examples of cortical dynamics, one for perceptual grouping in MT, and the other one for mental rotation in M1. We show that a neural implementation of the bayesian principle is both computationally efficient to perform these tasks and consistent with the experimental data on the related neuronal activities. A major implication is that a similar collective decision mechanism should exist in different cortical regions due to the similarity of the cortical functional architecture.     

Abnormal autonomic stress responses in obstructive sleep apnoea are reversed by nasal continuous positive airway pressure

Obstructive sleep apnoea (OSA) is associated with abnormalities in autonomic stress tests, which are tests of cardiovascular response in the autonomic nervous system (ANS). The level of abnormality has been related to the level of overnight arterial oxygen saturation (Sa,O2). We have studied ANS function pre- and post-treatment with nasal continuous positive airway pressure (nCPAP) in six males with moderately severe or severe OSA (apnoea/hypopnoea index (AHI) median 51 (range 14-74 events.h-1 of sleep). Tests consisted of heart rate responses to Valsalva manoeuvre, deep breathing, and change of posture from lying to standing. In addition, systolic blood pressure (SBP) response to standing and diastolic blood pressure (DBP) response to handgrip were studied. Each abnormal test (compared to published normal values) scored +1.0 and each marginal test result (90-95% confidence interval for normals) scored +0.5. A total score was calculated for the five tests performed in the evening and morning (maximum score 10 per patient). Patients had been receiving treatment for more than 1 year (median 471 (389-624) days) and objective compliance was monitored by a clock counter in the nCPAP machines. Five of six patients had regularly used nCPAP (mean 7.8 h.night-1) and all showed a normalization in ANS test score: pre-nCPAP 2 (1-4.5), post-nCPAP 0.2 (0-0.5) (p < 0.05, Wilcoxon signed rank test). One poorly compliant subject (No. 6; nCPAP 3 h.night-1) had a deterioration in ANS test score: 1 pre-nCPAP to 1.5 post-nCPAP. The improvement in ANS test score in the five compliant patients was positively correlated with an improvement in mean Sa,O2 during sleep posttreatment. We conclude that successful treatment of obstructive sleep apnoea leads to normalization of impaired autonomic stress responses.     

Costs and effectiveness of extracorporeal gallbladder stone shock wave lithotripsy versus laparoscopic cholecystectomy. A randomized clinical trial. McGill Gallstone Treatment Group

Thirty-five patients were randomized to extracorporeal shock-wave lithotripsy (ESWL) and 25 to laparoscopic cholecystectomy (LC). Stone disappearance occurred in only 12 of 32 ESWL patients [38% (95% CI: 21-56%)] during a 15-month follow-up. Greater incremental gains in quality of life after 6 months were observed among LC patients (p < .01). Total duration of disability was 6.8 +/- 8.5 days for ESWL, and 22.7 +/- 16.6 days for LC (p < .01). Nine (28%) patients crossed over electively to the LC group, but only 44% of these underwent LC within the next 3 years. ESWL cost Can $58.9/ day of disability saved. ESWL is limited by its selective applicability and modest stone disappearance rate. Its cost-effectiveness is largely dependent on patient acceptance of recurrent episodes of biliary colic due to the persistence of stone fragments.     

Clinical results of the modular porous-coated anatomic (PCA) total knee arthroplasty with cement: a 5-year prospective study

Our study examines the clinical, radiographic, and patient satisfaction outcome of the cemented Modular Porous-Coated Anatomic (PCA) total knee arthroplasty with a minimum 5-year follow up. All data were gathered prospectively and consecutively. Patient satisfaction was assessed with a self-administered survey. Statistical analysis examined the effect of 17 patient factors, 19 surgical factors, and postoperative continuous passive motion use on range of motion (ROM) and HSS scores at 2 years. Seventy-eight Modular PCA arthroplasties performed by 9 orthopedic surgeons on 71 patients between January 1988 and November 1989 are reported in this study. Preoperative HSS scores averaged 51.2 and improved to an average of 89 at 1 and 2 years, and 86 at 5 years after surgery (90% good or excellent). ROM changed after surgery through improvement in preoperative knee flexion contracture, but not in increased knee flexion. One patient underwent reoperation for patellar instability, and one patient's arthroplasty was revised at 53 months for late instability. The total reoperation rate for any reason was 7.7%. Zonal analysis for progressive radiolucency at the bone-cement interface showed increasing frequency of narrow (< 1 mm) radiolucencies concentrated on the anterior and medial aspect of the tibial tray. Ninety-eight percent of patients responded to an outcome questionnaire, and 96% rated themselves improved. The Kaplan-Meier probability of an implant surviving without loosening at 5 years was 100%. The Modular PCA TKA has a low incidence of patellofemoral problems, is clinically successful, and results are stable at a minimum 5-year follow-up examination.     

Preoperative preparation programs in children: a comparative examination

We sought to determine whether an extensive behavioral preparation program for children undergoing surgery is more effective than a limited behavioral program. The primary end point was child and parent anxiety during the preoperative period. Secondary end points included behavior of the child during the induction of anesthesia and the postoperative recovery period. Several days before surgery, children (n = 75) aged 2-12 yr randomly received either an information-based program (OR tour), an information + modeling-based program (OR tour + videotape), or an information + modeling + coping-based program (OR tour + videotape + child-life preparation). Using behavioral and physiological measures of anxiety, we found that children who received the extensive program exhibited less anxiety immediately after the intervention, in the holding area on the day of surgery, and on separation to the operating room. These findings, however, achieved statistical significance only in the holding area on the day of surgery (44[10-72] vs 32[8-50] vs 9[6-33]; P = 0.02). Similarly, parents in the extensive program were significantly less anxious on the day of surgery in the preoperative holding area, as assessed by behavioral (P = 0.015) and physiological measures (P = 0.01). In contrast, no differences were found among the groups during the induction of anesthesia, recovery room period, or 2 wk postoperatively. We conclude that children and parents who received the extensive preoperative preparation program exhibited lower levels of anxiety during the preoperative period, but not during the intraoperative or postoperative periods. IMPLICATIONS: The extensive behavioral preoperative program that we undertook had limited anxiolytic effects. These effects were localized to the preoperative period and did not extended to the induction of anesthesia or the postoperative recovery period.     

Co-culture, oviduct secretion and the function of oviduct-specific glycoproteins

Co-cultures of embryos with somatic cells, usually in the form of monolayers, or conditioned medium from these somatic cells, results in development past the early stage blocks and the formation of hatched blastocysts. Optimum rates of development are not achieved, however, and the task is to investigate components of the oviduct that are obligatory or facilitative for embryo development. Glycine and alanine are amino acids present in much higher concentrations in oviduct fluid than in serum or culture media. Glycoproteins specifically produced by the oviduct around oestrus bind to embryos and aid development but are absent from most culture media. These glycoproteins are induced by oestrogen in vivo but not in vitro. It is our contention that co-cultures of mammalian embryos should include appropriate concentrations of amino acids and a source of embryotrophic glycoproteins as an additive or by including stromal cells in addition to epithelial cells.