Traditionally, repetitive practice of a task is used to learn a new skill, exhibiting as immediately improved performance. Research suggests, however, that a more experience-based rather than exposure-based training protocol may allow for better transference of the skill to related tasks. In synergy-based motor control theory, fundamental motor skills, such as hand grasping, are represented with a synergy subspace that captures essential motor patterns. In this study, we propose that motor-skill learning through synergy-based mechanisms may provide advantages over traditional task repetition learning. A new task was designed to highlight the range of motion and dexterity of the human hand. Two separate training strategies were tested in healthy subjects: task repetition training and synergy training versus a control. All three groups showed improvements when retested on the same task. When tested on a similar, but different set of tasks, only the synergy group showed improvements in accuracy (9.27% increase) compared to the repetition (3.24% decline) and control (3.22% decline) groups. A kinematic analysis revealed that although joint angular peak velocities decreased, timing benefits stemmed from the initial feed-forward portion of the task (reaction time). Accuracy improvements may have derived from general improved coordination among the four involved fingers. These preliminary results warrant further investigation of synergy-based motor training in healthy individuals, as well as in individuals undergoing hand-based rehabilitative therapy.

Radionuclide irradiators (137Cs and 60Co) are commonly used in preclinical studies ranging from cancer therapy to stem cell biology. Amidst concerns of radiological terrorism, there are institutional initiatives to replace radionuclide sources with lower energy X-ray sources. As researchers transition, questions remain regarding whether the biological effects of γ-rays may be recapitulated with orthovoltage X-rays because different energies may induce divergent biological effects. We therefore sought to compare the effects of orthovoltage X-rays with 1-mm Cu or Thoraeus filtration and 137Cs γ-rays using mouse models of acute radiation syndrome. Following whole-body irradiation, 30-day overall survival was assessed, and the lethal dose to provoke 50% mortality within 30-days (LD50) was calculated by logistic regression. LD50 doses were 6.7 Gy, 7.4 Gy, and 8.1 Gy with 1-mm Cu-filtered X-rays, Thoraeus-filtered X-rays, and 137Cs γ-rays, respectively. Comparison of bone marrow, spleen, and intestinal tissue from mice irradiated with equivalent doses indicated that injury was most severe with 1-mm Cu-filtered X-rays, which resulted in the greatest reduction in bone marrow cellularity, hematopoietic stem and progenitor populations, intestinal crypts, and OLFM4+ intestinal stem cells. Thoraeus-filtered X-rays provoked an intermediate phenotype, with 137Cs showing the least damage. This study reveals a dichotomy between physical dose and biological effect as researchers transition to orthovoltage X-rays. With decreasing energy, there is increasing hematopoietic and intestinal injury, necessitating dose reduction to achieve comparable biological effects. Significance: Understanding the significance of physical dose delivered using energetically different methods of radiation treatment will aid the transition from radionuclide γ-irradiators to orthovoltage X-irradiators.

Purpose: Radionuclide irradiators (137Cs and 60Co) are commonly used in preclinical studies ranging from cancer therapy to stem cell biology. There are institutional initiatives to replace radionuclide sources with lower-energy X-ray sources amidst concerns of radiological terrorism. As researchers transition, there are questions whether the biological effects of γ-rays may be recapitulated with orthovoltage X-rays, since different energy may cause different biological effects. We, therefore, sought to compare the effects of orthovoltage X-rays and 137Cs γ-rays using mouse models of acute radiation syndrome. Experimental Design: 137Cs γ-rays were compared with Orthovoltage X-rays, generated at 300 kVp, 10 mA with 1 mm Cu or Thoraeus filtration. We assessed 30-day overall survival following whole-body irradiation and calculated LD50 by logistic regression. Comparing equivalent doses delivered with different average energies (Ē), we assessed bone marrow, spleen, and intestinal histology and flow cytometry. Results: The LD50 doses are 6.7 Gy, 7.4 Gy and 8.1 Gy with 1 mm Cu filtered (Ē=120 keV), and Thoraeus filtered X-rays (Ē=160 keV), and 137Cs (E=662 keV), respectively. At constant dose, hematopoietic injury was most severe with 1 mm Cu filtered X-rays with the greatest reduction in bone marrow cellularity, stem and progenitor populations, and intestinal crypts and OLFM4+ intestinal stem cells. Thoraeus filtered X-rays provoked an intermediate phenotype, with 137Cs showing the least damage. Conclusions: Our study reveals a dichotomy between physical dose and biological effect relevant as researchers transition to orthovoltage X-rays. With decreasing energy, there is increasing hematopoietic and intestinal injury, necessitating dose-reduction to achieve comparable biological effects.