Isolated astasia caused by a localized infarction in the suprathalamic white matter.

A 73-year-old woman with essential hypertension and diabetes mellitus abruptly developed astasia. There were no other neurological abnormalities. Cranial diffusion-weighted magnetic resonance imaging demonstrated a localized infarction in the right-sided suprathalamic white matter. Under antiplatelet agent and rehabilitation, the patient became asymptomatic within 4 days. This is a first reported case of isolated astasia due to a suprathalamic white matter infarction. We speculated that disruption of the connection from the ventrolateral nucleus of the thalamus to the posterior cingulate gyrus and/or supplementary motor area might cause astasia.

Exposure to blue light during lunch break: effects on autonomic arousal and behavioral alertness.

BACKGROUND: Exposures to melanopsin-stimulating (melanopic) component-rich blue light enhance arousal level. We examined their effects in office workers. Eight healthy university office workers were exposed to blue and orange lights for 30 min during lunch break on different days. We compared the effects of light color on autonomic arousal level assessed by heart rate variability (HRV) and behavioral alertness by psychomotor vigilance tests (PVT). Heart rate was higher and high-frequency (HF, 0.150.45 Hz) power of HRV was lower during exposure to the blue light than to orange light. No significant difference with light color was observed, however, in any HRV indices during PVT or in PVT performance after light exposure. SHORT CONCLUSION: Exposure to blue light during lunch break, compared with that to orange light, enhances autonomic arousal during exposure, but has no sustained effect on autonomic arousal or behavioral alertness after exposure.

Enhancement of autonomic and psychomotor arousal by exposures to blue wavelength light: importance of both absolute and relative contents of melanopic component.

BACKGROUND: Blue light containing rich melanopsin-stimulating (melanopic) component has been reported to enhance arousal level, but it is unclear whether the determinant of the effects is the absolute or relative content of melanopic component. We compared the autonomic and psychomotor arousal effects of melanopic-enriched blue light of organic light-emitting diode (OLED) with those of OLED lights with lesser absolute amount of melanopic component (green light) and with greater absolute but lesser relative content (white light). METHODS: Using a ceiling light consisting of 120 panels (55 × 55 mm square) of OLED modules with adjustable color and brightness, we examined the effects of blue, green, and white lights (melanopic photon flux densities, 0.23, 0.14, and 0.38 µmol/m2/s and its relative content ratios, 72, 17, and 14%, respectively) on heart rate variability (HRV) during exposures and on the performance of psychomotor vigilance test (PVT) after exposures in ten healthy subjects with normal color vision. For each of the three colors, five consecutive 10-min sessions of light exposures were performed in the supine position, interleaved by four 10-min intervals during which 5-min PVT was performed under usual fluorescent light in sitting position. Low-frequency (LF, 0.04-0.15 Hz) and high-frequency (HF, 0.15-0.40 Hz) power and LF-to-HF ratio (LF/HF) of HRV during light exposures and reaction time (RT) and minor lapse (RT >500 ms) of PVT were analyzed. RESULTS: Heart rate was higher and the HF power reflecting autonomic resting was lower during exposures to the blue light than the green and white lights, while LF/HF did not differ significantly. Also, the number of minor lapse and the variation of reaction time reflecting decreased vigilance were lower after exposures to the blue light than the green light. CONCLUSIONS: The effects of blue OLED light for maintaining autonomic and psychomotor arousal levels depend on both absolute and relative contents of melanopic component in the light.

Suppression of vagal cardiac modulation by blue light in healthy subjects.

BACKGROUND: In the contemporary life environments, our body is increasingly exposed to various sources of colored light, which may affect our physiological functions as non-image-forming effects. We examined the impacts of colored lights on the autonomic functions by the analysis of heart rate variability (HRV). METHODS: A lighting device consisting of four organic light-emitting diode (OLED) modules (55 × 55 mm2) with adjustable red-green-blue color was secured 24 cm above the eyes of subject lying supine in a light-shielded laboratory. Following a 15-min supine rest, electrocardiogram and respiration were measured continuously during 3-min darkness, 6-min colored OLED illumination, and 3-min darkness under paced breathing (15 breath/min). The measurements were repeated at a 45-min interval for red, green, and blue lights with melanopsin-stimulating photon flux density (MSPFD) of 0.00, 0.10, and 0.20 µmol/m2/s, respectively, in 12 healthy subjects (23 ± 2 years, two females). Additionally, the effects of blue lights with 0.20, 0.10, and 0.04 µmol/m2/s MSPFD were examined in four healthy subjects (25-39 years, two females). HRV was analyzed for low-frequency (LF, 0.04-0.15 Hz) and high-frequency (HF, 0.20-0.30 Hz) power and LF-to-HF ratio (LF/HF). RESULTS: Compared to darkness before lighting, HF power decreased (P < 0.001) and LF/HF increased (P = 0.024) during lighting on average of all color lights, whereas HF power showed a greater decrease with blue light than with red and green lights (P < 0.05 for both). The decrease in HF power lasted even during darkness after lighting (P < 0.001). HF power decreased with blue light with 0.20 µmol/m2/s MSPFD (P < 0.001) but not with that with 0.10 or 0.04 µmol/m2/s (P = 0.1 and 0.9, respectively). CONCLUSIONS: Vagal cardiac modulation is suppressed by OLED blue light in healthy subjects most likely through melanopsin-dependent non-image-forming effect.