Taking fatigue seriously: I. Variations in fatigue sampled repeatedly in healthy controls.

OBJECTIVE: The four objectives of this study were to test the ability of a 1-item fatigue scale to correlate with the fatigue subscale of the Profile of Mood States (POMS), to test the acceptability of recording hourly fatigue ratings, to examine the chronobiological variation in self-reports of fatigue, and finally to examine the degree to which self-report of fatigue correlated with actigraphy findings. METHODS: Ten healthy normal controls completed the POMS fatigue subscale hourly for three days. The same 10 healthy subjects wore an actigraph for 72 consecutive hours. The actigraph was modified to incorporate two event buttons which subjects were asked to push hourly to report their level of fatigue. RESULTS: The 1-item fatigue rating correlated significantly (mean r = 0.61) with the rest of the POMS subscale for fatigue. Subjects had no difficulty using the event button on the actigraph in entering the 1-item fatigue ratings. Fatigue ratings revealed marked differences in how healthy subjects report fatigue. There was no consistent diurnal patterning of fatigue. The fatigue ratings in general were not correlated with actigraphic measures. DISCUSSION: The study documents that fatigue can be repeatedly assessed with an ambulatory device and that self-reported fatigue levels vary enormously from hour to hour in a healthy normal sample.

Acoustic transmission in the dentate nucleus. I. Patterns of activity to click and hiss; II. Changes in activity and excitability after conditioning.

Recordings were made from 95 units of the dentate nucleus of naive cats to determine if patterns of response to 70 dB clicks could be distinguished from those to another acoustic stimulus (a hiss) of approximately equal sound pressure level. Further studies of an additional 309 units were conducted to determine if unit excitability and the response to clicks changed after Pavlovian conditioning in which blink responses were elicited by the clicks as conditioned stimuli. Over 50% of units tested before conditioning responded to click or hiss with increased activity, and 8% responded in the first 4-8 ms after the onset of the rapidly rising click. Cross-correlation of the respective 160 ms poststimulus histogram averages of mean activity showed dissimilar patterns of response to clicks and hisses (Pearson product-moment correlation coefficient + 0.02). Thus the averaged population responses distinguished these stimuli. In addition, individual cells were found in each behavioral state that responded selectively to either click or hiss. After conditioning with click as the conditioned stimulus, the number of units responding in the first 4-8 ms to click increased to 23%. The mean magnitude of activity 4-8 ms after presenting the click increased after conditioning but not after sensitization produced by backward pairing of the stimuli used for conditioning. After backward pairing only 6% of the units responded in the first 4-8 ms to click. The changes in activity after conditioning were accompanied by increases in neural excitability to intracellularly applied depolarizing current. In contrast with the changes in activity, the increases in neural excitability were also found after backward pairing. We conclude that short as well as long latency acoustic transmissions to click change in the dentate nucleus after conditioning, that changes in response to click are expressed in 4-8 ms responsive cells, and that many of these cells have different patterns of spike activity in response to click and hiss. The findings support the hypothesis that the dentate nucleus can play a significant role in short as well as long latency, adaptive acoustic transmission that can enhance the response to an acoustic signal used as a Pavlovian conditioned stimulus.

Seasonal variation in human illumination exposure at two different latitudes.

The authors measured ambient illumination exposure in healthy volunteers in San Diego, California (latitude 32 degrees 43' N, n = 30), and Rochester, Minnesota (latitude 44 degrees 1' N, n = 24), during each of the four quarters of the year, which were centered on the solstices and equinoxes. Subjects wore photosensors on their wrists and lapels (or foreheads while in bed) 24 h per day for an average of 5-6 days per quarter. The maximum of the two illumination readings was stored each minute. Annual average time spent per day in outdoor illumination (> or = 1000 lux) was significantly higher in San Diego than it was in Rochester (p < .04). Daily durations of illumination at or exceeding thresholds of 1, 10, 100, 1000, and 10,000 lux were highly seasonal in the sample as a whole (p < .01 at 1 lux, p < .0001 at other thresholds). Seasonal variation in outdoor illumination was far more pronounced in Rochester than it was in San Diego (interaction p < .001) but remained significant in San Diego (p < or = .03). Seasonal variation in indoor illumination was generally similar in the two cities. The median Rochester subject experienced illumination > or = 1000 lux for 2 h 23 min per day during summer and 23 min per day during winter. The corresponding times in San Diego were 2 h 10 min and 1 h 20 min. Neither age nor gender predicted illumination duration at any level. Both season and geographic location strongly influenced human illumination exposure, and behavior (choice of indoor vs. outdoor environment) was the most important mediating factor.

Automatic sleep/wake identification from wrist activity.

The purpose of this study was to develop and validate automatic scoring methods to distinguish sleep from wakefulness based on wrist activity. Forty-one subjects (18 normals and 23 with sleep or psychiatric disorders) wore a wrist actigraph during overnight polysomnography. In a randomly selected subsample of 20 subjects, candidate sleep/wake prediction algorithms were iteratively optimized against standard sleep/wake scores. The optimal algorithms obtained for various data collection epoch lengths were then prospectively tested on the remaining 21 subjects. The final algorithms correctly distinguished sleep from wakefulness approximately 88% of the time. Actigraphic sleep percentage and sleep latency estimates correlated 0.82 and 0.90, respectively, with corresponding parameters scored from the polysomnogram (p < 0.0001). Automatic scoring of wrist activity provides valuable information about sleep and wakefulness that could be useful in both clinical and research applications.

Pequeño vocabulario de la Biblia

Este pequeño vocabulario tiene el objetivo de ofrecer información sobre terminología elemental, aclarando expresiones que pueden parecer extrañas; también corregir distorsiones comunes entre términos similares.