Low-Dose Radiation-Induced Effects on Cognitive Function / 항공우주의학회지

The relation between the low-dose radiation and the cognitive decline remains limited and controversial. However, the increasing use of high-dose radiation for medical purposes and some historical radiation-related accidents indicated that the low-dose radiation reduced cognitive ability, suggesting the reconsideration of the central nervous system’s low sensitivity to radiation, which has been advocated by conventional radiation biology. Although the continuous stimulation of low-dose radiation is known to be an environmental stressor that causes a critical decline in cognition during space exploration, the overall mechanisms from radiation exposure to cognitive alteration is still lacking. One of its main reasons is the inconsistent empirical results, and there are various possibilities to cause the contradictory consequences, such as the hormesis effect of low-dose radiation, the cellular adaptive responses, the radiation resistance, the bystander effects, and the genomic instability. In this review, we survey the low-dose radiation-induced cognitive studies, targeting learning achievement, emotional changes as well as fundamental cognitive behaviors in both humans and animals. Also, some relevant molecular studies are reappraised to understand the low-dose radiation-induced effects on the cognitive function.

Effects of Microgravity on Human Physiology / 항공우주의학회지

Space exploration is one of the dreams of humankind. However, the intriguing environment was a challenge for the human body, where we must counter with many extreme conditions such as thermal support, radiation, microgravity. Life, as well as the human body, developed and evolved in the continuous presence of gravity, especially when living creatures transfer from the ocean to the land. Once this gravitational force doesn't impact on the body, the drastic changes occur. Some of these changes were observed immediately, while others progress only slowly. Since the first orbital flight was performed, several hazards for the organs of the human body were identified [1]. These changes in human physiology can reverse when astronauts return to Earth. This article will review the published findings of the effects of microgravity exposure on the human body.

The Linear Transmission of the Vestibular Neural Information by Galvanic Vestibular Stimulation / 대한평형의학회지

OBJECTIVE: Growing hypotheses indicate the galvanic vestibular stimulation (GVS) as an alternative method to manage the symptoms of parkinson's disease (PD). GVS is easy and safe for use, and non-invasive. However, it is elusive how the neural information caused by GVS is transmitted in the central nervous system and relieves PD symptoms. To answer this question, we investigated the transmission of neural information by GVS in the central vestibular system, focused on vestibular nucleus (VN). METHODS: Twenty guinea pigs were used for this study for the extracellular neuronal recordings in the VN. The neuronal responses to rotation and GVS were analyzed by curve-fitting, and the numerical responding features, amplitudes and baselines, were computed. The effects of stimuli were examined by comparing these features. RESULTS: Twenty six vestibular neurons (15 regular and 11 irregular neurons) were recorded. Comparing the difference of baselines, we found the neural information was linearly transmitted with a reduced sensitivity (0.75). The linearity in the neural transmission was stronger in the neuronal groups with regular (correlation coefficient [Cor. Coef.]=0.91) and low sensitive units (Cor. Coef.=0.93), compared with those with irregular (Cor. Coef.=0.86) and high-sensitive neurons (Cor. Coef.=0.77). CONCLUSION: The neural information by GVS was linearly transmitted no matter what the neuronal characteristics were.

Vestibular System Research Based on Electrophysiology / 대한이비인후과학회지

Electrophysiological research has improved the understandings of various neural controls on motion and their functional connectivity in the central nervous system. Unlike medical imaging techniques, the electrophysiological approach can provide the neural signal processing between two or more specific regions and their temporal transmission of neural information. Using its unique advantages, the vestibular system has been also studied for more than 100 years. However, it is a recent finding that various higher functions, such as cognition, memory, learning, and even spatial navigation, are constructed partially by the vestibular neural information in the human brain. It is caused by the historical underestimation on the vestibular system and its supporting position to the main neural flow. Here, we seek for a new research theme with various approaches in the vestibular system by reviewing electrophysiological researches on the vestibular system and their experimental results.