Integration of Position and Predictive Motion Signals in Aging Vision.

We examined the effect of aging on the integration of position and motion signals, which is essential for tracking visual objects, using the motion-induced position shift (MIPS) phenomenon. We first measured the MIPS and bias in speed perception at three eccentricities. Both young and older adults showed the increasing MIPS and decreasing perceived speed as the eccentricity increased, which is consistent with previous literature. More importantly, we found that the mean MIPS was 2.87 times larger in older adults, and the response variability in position tasks showed a larger difference between age groups compared with the difference in speed tasks. We then measured the MIPS across stimulus durations. Temporal changes in the MIPS showed similar patterns in young and older adults in that the MIPS initially peaked at around 60 ms and approached an asymptote. We further analyzed the changes in response variability across stimulus durations to estimate sensory noise and propagation noise separately and found that only sensory noise was significantly larger in older adults. The overall results suggest that the increased MIPS in older adults is due to the increased dependency on predictive motion signals to compensate for the relatively imprecise position signals, which in turn implies that older adults would depend more on the motion signals to track objects.

Popliteal sciatic nerve block versus spinal anesthesia in hallux valgus surgery.

BACKGROUND: We compared clinical properties and patient satisfaction between spinal anesthesia and popliteal sciatic nerve block (PSNB) for hallux valgus surgery. METHODS: Forty patients undergoing hallux valgus surgery were divided into spinal group (spinal anesthesia with 2.5 ml of 0.5% bupivacaine [n = 20]) and PSNB group (PSNB with 30 ml of 0.75% ropivacaine mixed with 10 ml of normal saline solution using a nerve stimulator [n = 20]). The PSNB group used a patient-controlled-analgesia (PCA) pump for postoperative pain control. The quality and side effects were compared between the two groups. A questionnaire was used to evaluate patient satisfaction with the use of anesthetic techniques and postoperative pain control in the PSNB group. This study was assessed 3 days postoperatively by a blinded observer. RESULTS: Procedure time and time from anesthesia until start of sugery were significantly shorter in the spinal group than those in the PSNB group (P < 0.01). Anesthesia-related complications such as hypotension, bradycardia, shivering, nausea/vomitting, post-dural puncture headache (PDPH) and urinary retension were observed in 15%, 10%, 5%, 5%, 10%, and 20% of patients in the spinal group, respectively. PSNB was not associated with these complications. Patient satisfaction was slightly higher for PSNB than for spinal anesthesia. In the PSNB group, patient satisfaction with postoperative pain-control was 95% above ordinary satisfaction. CONCLUSIONS: Despite the long duration of the procedure, PSNB is relatively safe, provides an adequate level of anesthesia, effectively controls postoperative pain and reduces side effects. Therefore, PSNB could be a potential anesthetic technique for hallux valgus surgery.

A practical MRI grading system for osteoarthritis of the knee: association with Kellgren-Lawrence radiographic scores.

PURPOSE: To propose a reproducible and constant MR grading system for osteoarthritis of the knee joint that provides high interobserver and intraoberver agreement and that does not require complicated calculation procedures. MATERIALS AND METHODS: This retrospective study sample included 44 men and 65 women who underwent both MRI and plain radiography of the knee at our institution. All patients were older than 50 years of age (mean 57.7) and had clinically suspected osteoarthritis of the knee. The standard of 4 grades on the MR grade scale was based mainly on cartilage injury and additional findings. Kellgren-Lawrence grades were assessed for the same patient group. The relationship between the results was determined. Statistical analyses were performed including kappa statistics, categorical regression analysis and nonparametric correlation analysis. RESULTS: The interobserver and intraoberver agreements between the two readers in the grading of osteoarthritis were found to be almost perfect. Interobserver and intraobserver agreements were slightly lower for the MR grading system than for the Kellgren-Lawrence grading scale. The correlation between the MR grade and Kellgren-Lawrence grade was very high and did not differ with patient age. The MR grades were highly correlated with the Kellgren-Lawrence grades and showed excellent interobserver and intraobserver agreements. CONCLUSION: This new MR grading system for osteoarthritis of the knee joint is reproducible and may be helpful for the grading of osteoarthritis of the knee without requiring reference to plain radiography.