Ultrasound imaging transducer motion during standing postural tasks with and without using transducer fixator.

BACKGROUND: Changes in the orientation of ultrasound (US) transducer relative to the body surface during dynamic standing tests can affect US measurements. OBJECTIVE: The purpose of the study was to evaluate ultrasound imaging transducer motion while measuring the lateral abdominal muscle thickness during standing tasks with and without using transducer fixator (TF). DESIGN: Cross-sectional experimental study. METHODS: A digital optical motion analysis system was used to assess the motions of US transducer during double-leg stance in different levels of platform stability of Biodex Balance System (BBS) (static, levels 6 and 3) with and without using TF in 45 healthy individuals. In addition, lateral abdominal muscle thickness was evaluated by US imaging. RESULTS: The results indicated that the amount of angular and linear transducer motions during static and dynamic standing tasks significantly decreased by the use of TF as compared to the conditions without TF (P < 0.001, effect size> 0.84). CONCLUSION: TF can significantly control US transducer motions within acceptable threshold limits during standing postural task. This may improve the clinical application of US imaging.

Differential effects of primary motor cortex and cerebellar transcranial direct current stimulation on motor learning in healthy individuals: A randomized double-blind sham-controlled study.

The purpose of study was to compare the effect of primary motor cortex (M1) and cerebellar anodal transcranial direct current stimulation (a-tDCS) on online and offline motor learning in healthy individuals. Fifty-nine healthy volunteers were randomly divided into three groups (n=20 in two experimental groups and n=19 in sham-control group). One experimental group received M1a-tDCSand another received cerebellar a-tDCS. The main outcome measure were response time (RT) and number of errors during serial response time test (SRTT) which were assessed prior, 35min and 48h after the interventions. Reduction of response time (RT) and error numbers at last block of the test compared to the first block was considered online learning. Comparison of assessments during retention tests was considered as short-term and long-term offline learning. Online RT reduction was not different among groups (P>0.05), while online error reduction was significantly greater in cerebellar a-tDCS than sham-control group (P<0.017). Moreover, a-tDCS on both M1 and cerebellar regions produced more long-term offline learning as compared to sham tDCS (P<0.01), while short-term offline RT reduction was significantly greater in M1a-tDCS than sham-control group (P<0.05). The findings indicated that although cerebellar a-tDCS enhances online learning and M1a-tDCS has more effect on short-term offline learning, both M1 and cerebellar a-tDCS can be used as a boosting technique for improvement of offline motor learning in healthy individuals.

The osmotic response of the isolated tectorial membrane of the chick to isosmotic solutions: effect of Na+, K+, and Ca2+ concentration.

Changes in the size, shape, and structure of the isolated tectorial membrane of the chick were measured in response to isosmotic changes in the ionic composition of the perfusion solution. Substitution of artificial perilymph (AP) for artificial endolymph (AE) caused a small (approximately 15%), slow (time constants tau approximately 12 min) shrinkage of the thickness of the tectorial membrane that was largely reversed on return to AE. Substitution of AP for AE alters not only the predominate cation (from K+ to Na+) but also the Ca2+ concentration (from < 7 mumol/l to 2 mmol/l). Additional experiments were performed to separate effects of each of these changes. When a high-Na+, low-Ca2+ solution was substituted for a high-K+, low-Ca2+ solution (AE), the tectorial membrane swelled significantly, often to more than twice its original thickness (the largest swelling was 337%), with a slow time course (tau approximately 23 min). Addition of the Ca2+ to either high-K+ or high-Na+ solutions caused rapid shrinkage of the tectorial membrane (tau approximately 2-3 min). Addition of the Ca2+ chelator EGTA caused rapid swelling (tau approximately 4 min). Large osmotic responses were only partially reversible and caused long-lasting changes. For example, long-duration solution changes that produced large, rapid osmotic responses early in an experiment tended to produce smaller and slower responses later in the experiment. In contrast, the small osmotic responses to short-duration solution changes were repeatable for tens of hours. Changes in ionic composition of the bath affected not only the thickness of the tectorial membrane but also its other dimensions. Responses were not generally isotropic; both the size and shape of the tectorial membrane generally changed. Consistent changes in microstructure accompanied the osmotic changes.