Influences of daily stress upon spatial orientation

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【Subjects and methods】 To investigate influences of fatigue upon spatial orientation function, we made 10 young volunteers (6 male and 4 females, mean age of 21.4 years) stay up all night, and recorded body sways and examined abilities of mental arithmetic next morning. These findings were compared to the results examined after sound sleep. Experiments were performed after obtaining informed consents from all subjects.【Results】 Mean total lengths of traces of the center of pressure for 3 minutes, when recorded while subjects were standstill, were 193.6±18.1 cm after sound sleep, and 218±20.0 after staying up all night. Mean areas of body sway were 4.71±0.91 cm^2, and 6.60±1.18 cm^2, respectively. When body sways were recorded while the subjects were rotated at 60 deg/s, mean total lengths of traces of the center of pressure were 632.7±69.0 cm and 678.4±106.5 cm, and mean areas of body sway were 24.82±4.71 cm^2 and 36.35±10.81 cm^2, respectively. All these findings did not significantly differ between the sound sleep condition and the staying up all night condition. The ability of mental arithmetic also did not show any significant difference between two conditions.【Discussion】 Fatigue and lack of sleep are often found in patients who complain of vertigo or dizziness. In order to know the influence of brain exhaustion upon body balance and mental activity, we performed the present study on young normal volunteers. Both abilities of body balance and mental arithmetic were not influenced by staying up all night. Although we have investigated influences of working all night upon stress markers such as plasma vasopressin, steroid hormones, and plasma fibrinogen, any statistical difference has not been found after working all night. Staying up all night alone may not seem to deteriorate brain functions.