Sit-to-stand (STS) motion is an important daily activity, and many post-stroke patients have difficulty performing STS motion. Previous studies found that there are four muscle synergies (synchronized muscle activations) in the STS motion of healthy adults. However, for post-stroke patients, it is unclear whether muscle synergies change and which features primarily reflect motor impairment. Here, we use a machine learning method to demonstrate that temporal features in two muscle synergies that contribute to hip rising and balance maintenance motion reflect the motor impairment of post-stroke patients. Analyzing the muscle synergies of age-matched healthy elderly people (n = 12) and post-stroke patients (n = 33), we found that the same four muscle synergies could account for the muscle activity of post-stroke patients. Also, we were able to distinguish post-stroke patients from healthy people on the basis of the temporal features of these muscle synergies. Furthermore, these temporal features were found to correlate with motor impairment of post-stroke patients. We conclude that poststroke patients can still utilize the same number of muscle synergies as healthy people, but the temporal structure of muscle synergies changes as a result of motor impairment. This could lead to a new rehabilitation strategy for poststroke patients that focuses on activation timing of muscle synergies.

The relationship between tissue oxygen partial pressure (pO2) values and electrical activities of guinea pig olfactory cortical slices were investigated as the slices were superfused with Krebs-Ringer's solution equilibrated with different gas mixtures. The pO2 values were measured in the slices with oxygen microelectrodes (tip diameter less than 1 micrometer). 1. Studies of pO2 measurements showed the variability of minimum pO2 value of oxygen profiles in the tissue slice. The profile depends on the pO2 value of the superfusate and on the thickness and the oxygen consumption of the slice. With our experimental conditions an anoxic area developed in the middle layers of the slice when the thickness of the slice exceeded ca. 430 micrometers; in thinner slices there was no anoxic area. In our case the limiting section thickness of the slice was ca.430 micrometers from the viewpoint of tissue pO2 value. 2. The N potential (extra-cellularly recorded EPSP) showed a tendency to decrease in amplitude, for slices being thicker than ca 430 micrometers. It would seem reasonable to think that the decrement of the N potential was brought about by the existence of the anoxic area. 3. When the slice was bubbled with 25, 45 or 95% O2, the tissue pO2 value changed, and the N potential height also changed. The N potential was higher in amplitude when bubbled with 95% O2 than with 25% O2. On the other hand, the amplitude of the IS potential (the lateral olfactory tract potential) was not influenced as much as that of the N potential by the change of tissue pO2 value in the slice. 4. The tissue pO2 value was continuously measured during the electrical stimulation of the lateral olfactory tract. The steady state level of tissue pO2 value obtained during the stimulation diminished as the frequency of stimulation increased from 5-30 Hz.

We examined the effect of heating on electrical activity of neurons in the guinea pig olfactory cortex slice. At the control temperature (37 degree C) the potential evoked by stimulation of the lateral olfactory tract consisted of an initial spike (IS) potential and a negative (N) potential. The IS potential is considered to be presynaptic and the other transsynaptic. The IS potential decreased in amplitude on heating and completely disappeared at 49 degree C. However, it recovered when the temperature was lowered to 37 degree C after five minutes of incubation at 49 degree C. In contrast, the N potential increased in amplitude at 39 degree C, was completely suppressed at 47 degree C and did not recover when the temperature was dropped to the control temperature. The maximum temperature from which the N potential recovered was 43 degree C. Unit activity was extracellularly recorded from neurons in the slice. On heating the brain slice some neurons showed an increase in activity others a decrease, and the rest were unaffected. We conclude that neurons in the olfactory cortex have different thermal sensitivities.

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