RESUMEN
A single session of priming cathodal transcranial direct current stimulation (tDCS) prior to anodal tDCS (c-a-tDCS) allows cumulative effects on motor learning and retention. However, the impact of multiple sessions of c-a-tDCS priming on learning and retention remains unclear. Here, we tested whether multiple sessions of c-a-tDCS (over 3 consecutive days) applied over the left sensorimotor cortex can further enhance motor learning and retention of an already learned visuo-motor task as compared to anodal tDCS (a-tDCS) or sham. In a between group and randomized double-blind sham-controlled study design, 25 participants separated in 3 independent groups underwent 2 days of baseline training without tDCS followed by 3-days of training with both online and offline tDCS, and two retention tests (1 and 14 days later). Each training block consisted of five trials of a 60 s circular-tracing task intersected by 60 s rest, and performance was assessed in terms of speed-accuracy trade-off represented notably by an index of performance (IP). The main findings of this exploratory study were that multiple sessions of c-a-tDCS significantly further enhanced IP above baseline training levels over the 3 training days that were maintained over the 2 retention days, but these learning and retention performance changes were not significantly different from the sham group. Subtle differences in the changes in speed-accuracy trade-off (components of IP) between c-a-tDCS (maintenance of accuracy over increasing speed) and a-tDCS (increasing speed over maintenance of accuracy) provide preliminary insights to a mechanistic modulation of motor performance with priming and polarity of tDCS.
RESUMEN
BACKGROUND: Red blood cell (RBC) storage in blood banks is not exempt from cellular injury. Alterations not observed on RBCs freshly isolated from units can rapidly appear in circulation. The transfusion of old blood units, even if this is a controversial issue, could therefore have adverse effects on the recipient. We wanted to determine the respective effects of storage duration and recipient plasma on RBCs for transfusion into patients with severe sepsis. STUDY DESIGN AND METHODS: Eleven stored RBC units were sampled at various time points, approximately Days 3 to 8 (referred to as fresh RBCs) and Days 38 to 42 (old RBCs) and tested in coincubation experiments with plasma obtained from 13 patients with severe sepsis and 17 healthy donors as controls. RBCs were tested after 24 or 48 hours at 37°C for the detection of senescence markers (phosphatidylserine exposure, calcium influx, and reactive oxygen species detection and decrease in size) with or without exposure to plasma. RESULTS: We confirmed that a 42-day refrigerated storage of RBCs alone (without any incubation in plasma) had no significant effect on RBCs and no senescence marker detected. By contrast, ex vivo exposure to plasma samples altered both fresh and old RBCs, with a much larger effect for old RBCs, regardless of the plasma used (sepsis vs. control). CONCLUSION: We show that the main factor affecting the senescence of RBCs for transfusion into patients with severe sepsis is the age of the stored units rather than the clinical status of the recipient.
