Biomedical subjects

Gregory Neely

Publications and source records attributed to Gregory Neely.

6 recordsLinked to original sources

PubMed2006

Performance on a simple reaction time task while sleep deprived.

Divergent results have been reported on the effect of a night's sleep loss on performance of a single monotonous task. The present experiment examined the effect that partial sleep deprivation had on 10 participants' performance on a simple reaction time task requiring low responding for 120 min. compared to performance on the same task when well rested. Participants missed significantly more signals and had slower reaction times when sleep deprived. Reaction times increased with time when participants were both sleep deprived and rested, but the number of misses did not significantly change over time. Reaction time was significantly correlated with subjective ratings of sleepiness and heart rate in both conditions. EEG and heart-rate variability measures did not correlate significantly with reaction time. Misses correlated significantly with subjective ratings and heart rate but only in the rested condition.

Adult↗

PubMed2005

Electroencephalography and subjective ratings of sleep deprivation.

BACKGROUND AND PURPOSE: Sleep-related vehicle accidents account for many injuries and fatalities each year on monotonous motorways and roads. To effectively prevent such incidents requires greater knowledge of the mechanisms and development of the effects of sleep deprivation. Ten volunteers participated in a laboratory study aimed to analyze the way changes in wakefulness were described in terms of EEG changes and subjective ratings. PATIENTS AND METHODS: For each subject, the study consisted of four testing sessions that varied in length on different days: one session each of 60, 90, and 120 min when sleep-deprived, and one session of 120 min when rested. Changes in wakefulness were analyzed using electroencephalographic recordings and ratings on two different scales, the Karolinska Sleepiness Scale (KSS) and the Category-Ratio Scale (CR-10). RESULTS: The results indicate quite conclusively that significant changes in the perception of sleepiness occur during the first 60-90 min of sedentary, monotonous work. Beyond this time period, subjective and physiological changes remained constant throughout the rest of the 120-min period. CONCLUSION: In general, the subjective rating scales highly and significantly correlated with theta activity in both tired and rested states and with alpha activity in the rested state. Similar results were seen using both subjective rating scales.

Adult↗

PubMed2005

Heart rate variability during sedentary work and sleep in normal and sleep-deprived states.

The possibility of using heart rate variability (HRV) as an indicator of sleepiness was investigated by analysing heart rate (HR) activity and electroencephalography (EEG) recordings from 10 individuals who performed a monotonous attention task for 120 min in both sleep-deprived and rested states. In both conditions, measurements were collected during 60 min of sleep immediately following a 120 min of non-sleep (awake phase). Although HR decreased significantly in both the rested and the sleep-deprived states during the awake phase, HR significantly changed sooner when subjects were sleep-deprived than when they were rested. No significant changes in HRV were found during the awake phase; however, HRV correlated significantly with alpha and theta power densities when rested but not when sleep-deprived. During the sleep phase, the total HRV and very low and low frequency HRV components significantly decreased approximately 40 min after sleeping in the sleep-deprived condition. These HRV components were also significantly and negatively correlated with delta power densities. HRV does not seem to be a viable indicator of sleepiness; however, HRV may be useful for determining sleep stages.

Adult↗

PubMed2004

Cognitive performance and subjective experience during combined exposures to whole-body vibration and noise.

OBJECTIVE: The goal of this study was to examine the effects of noise and whole-body vibration, individually and combined, and at various stimulus intensity levels, on cognitive performance and subjective experience. METHOD: Fifty-four participants (27 men and 27 women) with a mean age of 25 years, ranging from 19 to 30, were exposed for 20 min each to a 16-Hz sinusoidal whole-body vibration, a helicopter sound at 21 Hz, both stimuli combined, and a control condition. Participants were randomly assigned to one of three groups: low intensity [77 dB(A) noise and 1.0 m/s2 vibration], medium intensity [81 dB(A)/1.6 m/s2] or high intensity [86 dB(A)/2.5 m/s2. During each environmental exposure, short-term memory performance was tested with a visual Sternberg paradigm. Reaction time was measured as a dependent variable. Directly following each environmental exposure, participants rated the difficulty of the task and the annoyance level of the exposure stimulus. RESULTS: Results revealed no significant changes in reaction times due to environmental exposure or intensity level. However, participants significantly rated the combined exposure as both more annoying and more difficult than the other conditions. Further, the high-intensity group rated subjective annoyance significantly higher than the other groups for all conditions. CONCLUSIONS: The results from this study indicate that performance alone is not a sufficient measure for the study of the effects of combined stimuli on a human operator.

Adult↗

PubMed2004

Missing a meal: effects on alertness during sedentary work.

The purpose of this investigation was to evaluate the acute effects of missing a meal on alertness. The participants were ten university students between 20-29 years old, five females and five males. Participants were chosen on the basis of their good sleep and eating practices. Measurements were collected during an eight hour period starting at 8.00 AM on four separate days. During the test period, participants carried out their normal study activities while on separate days receiving either just breakfast, just lunch, both lunch and breakfast, or no meal at all. During the test period, EEG was monitored continuously while subjective ratings of performance and tiredness were collected every half-hour. The results showed that while there were neither physiological nor subjective indications of tiredness which could be attributed to meal consumption, subjective feelings of lack of energy and motivation was significantly more pronounced at the end of the workday when missing a meal or two.

Adult↗

PubMed2002

Sensation seeking and subjective unpleasantness ratings of stimulus intensity.

Zuckerman's Sensation Seeking Scale measures tendency to seek novel, varied, complex, and intense sensations and experiences and the willingness to take risks for the sake of such experiences. In this study, the subjective experience of sensory intensity change was explored by asking six high and six low sensation seekers to expose themselves to a combined sound and vibration stimulus that increased in intensity until one of three different levels of subjective unpleasantness was reached. Analysis showed that high sensation seekers consistently exposed themselves to longer periods of stimulation and thus higher intensities.

Adult↗