Objectives: (1) To evaluate the learning potential and performance improvements during standing balance training with visual feedback (VBT) in individuals with incomplete spinal cord injury (SCI) and (2) to determine whether standing static and dynamic stability during training-irrelevant tasks can be improved after the VBT. Setting: National Rehabilitation Center for Persons with Disabilities, Tokorozawa, Japan. Methods: Six participants with chronic motor and sensory incomplete SCI who were able to stand for at least 5 min without any form of assistive device performed the VBT, 3 days per week, for a total of 12 sessions. During the training, participants stood on a force platform and were instructed to shift their center of pressure in the indicated directions as represented by a cursor on a monitor. The performance and the rate of learning were monitored throughout the training period. Before and after the program, static and dynamic stability was assessed. Results: All participants showed substantial improvements in the scores, which varied between 236 ± 94 and 130 ± 14% of the initial values for different exercises. The balance performance during training-irrelevant tasks was significantly improved: for example, the area inside the stability zone after the training reached 221 ± 86% of the pre-training values. Conclusion: Postural control can be enhanced in individuals with incomplete SCI using VBT. All participants showed substantial improvements during standing in both game performance and training-irrelevant tasks after the VBT.

Previous studies have demonstrated that plantar cutaneous afferents can adjust motoneuron excitability, which may contribute significantly to the control of human posture and locomotion. However, the role of plantar cutaneous afferents in modulating the excitability of stretch and H-reflex with respect to the location of their excitation remains unclear. In the present study, it was hypothesized that electrical stimulation delivered to the sole of the foot might be followed by modulation of spinal excitability that depends on: (1) the stimulation location and (2) the reflex studied. In these experiments, conditioned and unconditioned stretch and H-reflexes were evoked in 16 healthy subjects in a seated position. Both reflexes were conditioned by non-noxious electrical plantar cutaneous afferent stimulation at two different sites, the heel and metatarsal regions, at four different conditioning-test (CT) intervals. The conditioning stimulation delivered to the heel caused a significant facilitation of the soleus stretch reflex for all CT intervals, whereas the soleus H-reflex had significant facilitation only at CT interval of 50 ms and significant inhibition at longer CT intervals. Stimulation delivered to the metatarsal region, however, resulted mainly in reduced stretch and H-reflex sizes. This study extends the reported findings on the contribution of plantar cutaneous afferents within spinal interneuron reflex circuits as a function of their location and the reflex studied.

No abstract

The effect of development and aging on common modulation between bilateral plantarflexors (i.e., the right and left soleus, and the right and left medial gastrocnemius) (bilateral comodulation) and within plantarflexors in one leg (i.e., the right soleus and the right medial gastrocnemius) (unilateral comodulation) was investigated during bipedal quiet standing by comparing electromyography-electromyography (EMG) coherence among three age groups: adult (23-35 years), child (6-8 years), and elderly (60-80 years). The results demonstrate that there was significant coherence between bilateral plantarflexors and within plantarflexors in one leg in the 0- to 4-Hz frequency region in all three age groups. Coherence in this frequency region was stronger in the elderly group than in the adult group, while no difference was found between the adult and child groups. Of particular interest was the finding of significant coherence in bilateral and unilateral EMG recordings in the 8- to 12-Hz frequency region in some subjects in the elderly group, whereas it was not observed in the adult and child groups. These results suggest that aging affects the organization of bilateral and unilateral postural muscle activities (i.e., bilateral and unilateral comodulation) in the plantarflexors during quiet standing.

While previous studies have shown that muscle stretching suppresses monosynaptic spinal reflex excitability in stretched muscles, its effects on non-stretched muscles is still largely unknown. The purpose of this study was to examine the effects of muscle stretching on monosynaptic spinal reflex in non-stretched muscles. Ten healthy male subjects participated in this study. Muscle stretching of the right triceps surae muscle was performed using a motor torque device for 1 minute. Three different dorsiflexion torques (at approximately 5, 10, and 15 Nm) were applied during muscle stretching. Spinal reflexes evoked by transcutaneous spinal cord stimulation were recorded in both the lower-limb muscles before, during, and at 0 and 5 min following muscle stretching. The amplitudes of the spinal reflexes in both the stretched and non-stretched muscles in the right (ipsilateral) leg were smaller during stretching compared to before, and at 0 and 5 min after stretching. Furthermore, the degree of reduction in the amplitude of the spinal reflexes in the right (ipsilateral) leg muscles increased significantly as the dorsiflexion torque (i.e., stretching of the right triceps surae muscles) increased. In contrast, reduction in the amplitude of the spinal reflexes with increasing dorsiflexion torque was not seen in the left (contralateral) leg muscles. Our results clearly indicate that muscle stretching has inhibitory effects on monosynaptic spinal reflexes, not only in stretched muscles, but also in non-stretched muscles of the ipsilateral leg.

The purpose of this study was to investigate how the recruitment properties of the corticospinal pathway are modulated in the soleus (SOL) and tibialis anterior (TA) muscles depending on postures. A wide range of stimulus intensities were applied via transcranial magnetic stimulation over the primary motor cortex during standing (STD) and sitting (SIT) with a comparable background activity level in each muscle. The relationship between the stimulation intensities and the size of motor-evoked potentials was assessed by the Boltzmann sigmoid function, which is characterized by a plateau value, maximum slope, and threshold. The plateau value and maximum slope were significantly higher during STD than during SIT in the SOL muscle (STD vs. SIT, plateau value: 50.0 +/- 21.8 vs. 33.9 +/- 12.3 mV ms, maximal slope: 1.6 +/- 0.7 vs. 1.2 +/- 0.5 mV ms/% maximal stimulator output). Similar changes of the parameters were also observed in the TA muscle (STD vs. SIT, plateau value: 71.0 +/- 22.9 vs. 41.4 +/- 16.1 mV ms, maximal slope: 5.0 +/- 2.0 vs. 2.5 +/- 0.7 mV ms/% maximal stimulator output). The threshold did not differ significantly between the two conditions and both muscles. These results indicate that the central nervous system requires a different control for each postural condition; that is, the relative balance of the excitatory and inhibitory inputs to the corticospinal pathways as well as the number of neurons of subliminal fringe in the corticospinal pathway was increased during STD compared with those during SIT.

No abstract

Expanding diet breadth to previously unexplored resources was a key strategy in Neolithic adaptation through the Holocene. Most prominently, marine resources became substantial supplements in coastal and island regions worldwide. The Neolithic culture in Korea, known as the Chulmun, has been viewed as heavily based on a marine diet, as a large number of sites are shell middens with well-preserved marine resources. Terrestrial animal taxa are also documented in shell middens, but plant resources have been rarely reported because of the absence of archaeobotanical research. To help fill in this gap, we compared archaeobotanical and organic residue isotope data from four Neolithic shell middens, including Beombang, Bibongri, Sejukri, and Tongsamdong (7500 to 4000 cal BP). Results indicate that ca. Coastal inhabitants procured a broad-spectrum of resources from both marine and terrestrial taxa, while maintaining some difference in resource procurement across settlements from the Early Neolithic period. Particularly, the longer the occupation was, the wider the diet breadth became, including various plant resources and terrestrial animals. Our research demonstrates the utility of integrating archaeobotanical, grain impression, and isotopic methods, while building an additional robust case study demonstrating long-term niche construction and diverse resource seeking in coastal regions in the area.