Reinforcement Learning May Demystify the Limited Human Motor Learning Efficacy Due to Visual-Proprioceptive Mismatch.

Vision and proprioception have fundamental sensory mismatches in delivering locational information, and such mismatches are critical factors limiting the efficacy of motor learning. However, it is still not clear how and to what extent this mismatch limits motor learning outcomes. To further the understanding of the effect of sensory mismatch on motor learning outcomes, a reinforcement learning algorithm and the simplified biomechanical elbow joint model were employed to mimic the motor learning process in a computational environment. By applying a reinforcement learning algorithm to the motor learning of elbow joint flexion task, simulation results successfully explained how visual-proprioceptive mismatch limits motor learning outcomes in terms of motor control accuracy and task completion speed. The larger the perceived angular offset between the two sensory modalities, the lower the motor control accuracy. Also, the more similar the peak reward amplitude of the two sensory modalities, the lower the motor control accuracy. In addition, simulation results suggest that insufficient exploration rate limits task completion speed, and excessive exploration rate limits motor control accuracy. Such a speed-accuracy trade-off shows that a moderate exploration rate could serve as another important factor in motor learning.

Suppressive effects of young radish cultivated with sulfur on growth and metastasis of B16-F10 melanoma cells.

The oral administration of extracts of young radishes cultivated with sulfur after intravenous tumor cell injection achieved a marked reduction of pulmonary colonization in mice. Treatment of the mice with extracts of young radish cultivated with sulfur did not show any increase in the number of CD8+ or NK T cells in the spleen, indicating no influence on host immunity. Sulforaphane, which could be a candidate for an active compound from young radishes cultivated with sulfur, inhibited cell growth of B16-F10 melanoma cells. In addition, extracts of the young radish cultivated with sulfur-fed group showed enhanced quinine reductase (QR) activities in the liver and lung and a slight increase of glutathione S-transferase (GST) activity in the liver. These results suggested that the administration of extracts of young radishes cultivated with sulfur suppressed pulmonary tumorigenesis, possibly due to increased activity of detoxification enzymes in the liver and lung, and partly due to cell cytotoxicity.