Biomedical subjects

M Casagrande

Publications and source records attributed to M Casagrande.

At least 19 recordsLinked to original sources

PubMed2001

Sleepiness: evaluating and quantifying methods.

The aim of this literature review is to analyze the methods mainly used for evaluating and quantifying the complex phenomenon of sleepiness. The most common distinction is between subjective measures or self-evaluations, performance decrement measures, measures for evaluating sleep propensity and measures of arousal decrease. Techniques mainly used in specialized literature will be briefly presented and commented upon, evaluating their sensitivity, advantages and limitations. We conclude that: (a) different measures inevitably are differently sensitive to sleepiness fluctuations; (b) the amount of prior sleep is strongly relevant in quantifying sleepiness levels; (c) subjective and behavioral measures show a higher level of vulnerability to external and motivational factors.

Attention↗

PubMed2001

Modified autonomic balance in offsprings of diabetics detected by spectral analysis of heart rate variability.

This study was performed to evaluate the influence of family history for non-insulin-dependent diabetes mellitus (NIDDM) on autonomic balance. The latter was assessed by spectral analysis of heart rate variability (SA-HRV) and by analyzing the relative contribution of low-frequency (LF) and high-frequency (HF) components. Twenty glucose normotolerant offsprings of NIDDM parents and 20 controls underwent a 1-hour continuous electrocardiogram (ECG). LF and HF (mean +/- SEM in normalized units [NU]), respectively increased and decreased in offspring versus controls. The LF/HF ratio (mean +/- SEM) significantly increased (LF/HF = 3.25 +/- 0.7 v 1.45 +/- 0.5, P <.0001 offsprings v controls). To test a stimulated response, a passive tilting (+ 90 degrees ) after 30 minutes of bed rest (0 degrees ) was performed in a subsample of subjects (10 offsprings v 10 controls). During bed rest, we found significantly higher values of the LF/HF ratio in offsprings versus controls (1.93 +/- 0.3 v 1.08 +/- 0.2, P <.05), whereas in the head-up position, the LF/HF ratio value increased to the same levels in the 2 groups (6.48 +/- 1.3 v 6.89 +/- 1.4, not significant [NS]). NIDDM family history is characterized in the basal condition by an imbalance of the autonomic system, which, compared with controls, is expressed by a higher weight of sympathetic and a lower weight of parasympathetic components. No significant differences can be found under stimulated conditions.

Adult↗

PubMed2000

Selective slow-wave sleep deprivation and time-of-night effects on cognitive performance upon awakening.

We evaluated the effects of selective slow-wave sleep (SWS) deprivation and time-of-night factors on cognitive performance upon awakening. Ten normal men slept for 6 consecutive nights in the laboratory: 1 adaptation, 2 baseline, 2 selective SWS deprivation, and 1 recovery night. Cognitive performance was assessed by means of a Descending Subtraction Task after 2, 5, and 7.5 h of sleep. There was an almost complete selective SWS suppression during both deprivation nights, and a significant SWS rebound during the recovery sleep. Regarding cognitive performance, a progressive linear decrease of sleep inertia upon successive awakenings was found during all experimental nights except for the recovery night. In addition, a significant decrease of sleep inertia was observed upon the morning awakening of the second deprivation night for the measure of performance speed, and a significant increase of sleep inertia upon the morning awakening of the recovery night for the measure of performance accuracy. The results show that cognitive performance upon awakening is adversely affected by sleep depth and that, during the sleep-wake transition, cognitive performance accuracy is more impaired than performance speed.

Adult↗

PubMed1999

Endocrine and psychophysiological aspects of human adaptation to the extreme.

Human beings need to adapt to any extreme, unknown, or isolated environment. This adaptation requires changes in the normal regulation of psychophysiological homeostasis, as described in terms of stress reaction. The aim of the present study was to monitor the processes of human adaptation to cold and isolated areas in Antarctica during the 12th expedition of the Italian National Research Program. Nine healthy subjects (experimental subjects), members of the expedition, and nine controls in Italy, were studied over a period of 2 months. Anterior pituitary hormone secretion, insulin, and melatonin, plus routine blood test, blood pressure, and ECG were performed. In addition, psychophysiological correlates were also recorded before and after the expedition period. In experimental subjects results of metabolic data suggested the presence of an increased peripheral insulin sensitivity at the end of the permanence in the station and a significant increased of total cholesterol. Hematocrit also significantly increased due to the conditions of hypobaric hypoxia. Results of endocrine data showed a significant decrease (p < 0.05) of hormone levels, which was associated with a significant decrement of the Galvanic Skin Response (GSR) activity to a standardized cognitive stress. No significant differences were reported in the controls. The data suggest that the exposure to the extreme environment develops a possible psychophysiological mechanism(s) that decreases the individual arousal.

Acclimatization↗

PubMed1999

Auditory arousal thresholds after selective slow-wave sleep deprivation.

OBJECTIVES: The aim of this study is to assess Auditory Arousal Thresholds (AATs) three times during an undisturbed baseline night and to compare them to AATs during the recovery night that follows two consecutive nights of selective SWS deprivation. The presence of a time-of-night effect on AATs will also be assessed. METHODS: Ten male Ss slept in the laboratory for 6 consecutive nights. The first two nights were undisturbed. The 3rd night was considered as baseline. During the 4th and 5th nights, selective SWS deprivation was obtained by means of acoustic stimulation. The 6th night was a recovery. In the last 4 nights Ss were awakened three times, after 2, 5 and 7.5 h of sleep, respectively. All the awakenings were carried out from stage 2 (after at least 5 consecutive min of stage 2), by means of 1000 Hz ascending tone series. The AAT determination was based on EEG-EMG criteria: at least 10-s of clear alpha rhythm and/or a 10 s movement arousal. RESULTS: During both deprivation nights, SWS amount was close to zero. In the ensuing recovery night a significant SWS rebound was found, accompanied by a significant increase of AATs with respect to the baseline. Furthermore, there was a significant linear decrease of AATs during the night. Finally, the individual correlations between AATs and SWS amount were significant in 4 out of 10 Ss. CONCLUSIONS: These results confirm that AATs are a reliable index of sleep depth by showing that the SWS rebound following selective SWS deprivation is paralleled by a significant AAT enhancement. The experimental paradigm also allows us to claim that AATs show a decreasing linear trend during the night, having excluded any procedural bias. Finally, AATs can be directly related to SWS amount that preceded the awakening, although the individual correlations between AATs and SWS have to be considered with caution, given the high inter-subject variability and the small number of observations.

Acoustic Stimulation↗

PubMed1998

Smooth pursuit and saccadic eye movements as possible indicators of nighttime sleepiness.

Sleepiness is associated with specific variations of spontaneous oculomotor activity. During nocturnal sleep onset periods and also during the Multiple Sleep Latency Test (MSLT) a reduction of both rapid eye movements and blinks are recorded. In many operational contexts it might be even more relevant to assess whether and to what extent voluntary visual ocular control is affected by sleepiness due to sleep deprivation and time-of-day effects. In this study we evaluated, in a laboratory simulation of a sudden inversion of the sleep-wake cycle, the nocturnal modifications of smooth pursuit (SP) and saccadic (SAC) eye movements as possible indicators of sleepiness. Levels of sleepiness were objectively measured by means of MSLT and Maintenance of Wakefulness Test (MWT); subjective ratings of sleepiness were also obtained. After a diurnal sleep, five subjects underwent four nocturnal test sessions, each one comprising an SP and a SAC trial. Both the SP variables considered (velocity gain and phase) showed a trend similar to that one of MWT latencies, being significantly impaired only in the last nocturnal trial, when levels of sleepiness were maximal. Saccadic accuracy showed the same trend, being negatively affected by sleepiness only in the last nocturnal session. In addition, percentage of rejected (inappropriate) saccades showed a linear increase during the night, paralleling the shortening of sleep latency at MSLT and the linear increase of subjective ratings of sleepiness. These results, suggesting that saccadic performance, unlike SP, seems to be more sensitive to increasing levels of sleepiness, encourage further research on this topic.

Adult↗

PubMed1998

Actigraphic motor asymmetries during sleep.

Much evidence indicates that during sleep there is a repatterning of motor asymmetries with a relative advantage of the left hand (i.e., the left hand moves more than the right). This could be due to the ability of the right hemisphere in operating at levels of reduced arousal (arousal hypothesis) or to its superior spatial abilities (motor specificity hypothesis), or it could indicate a greater need for sleep in the left hemisphere (homeostatic hypothesis). Since only the latter hypothesis predicts that the repatterning should be present in the first part of sleep (i.e., when the homeostatic processes are more pronounced), the present study evaluated whether actigraphic data are consistent with this prediction. Sixteen right-handed college students wore actigraphs (AMI 16K) on both upper and lower limbs for about 56 hours. Factorial ANOVAS were carried out on side (left vs right) and part (first vs second) of the recording period during sleep and waking. During waking, the right hand showed more intense motor activity as compared to the left. During sleep, in the first part of the night, the right hand lost this advantage, while in the second part of the night it regained its superiority. Since this repatterning was specific for hand movements and no difference was found in overall motor activity and in arousal between the two parts of the sleep period, the results are interpreted as consistent with the homeostatic hypothesis.

Adult↗

PubMed1998

Sleepiness, alertness and performance during a laboratory simulation of an acute shift of the wake-sleep cycle.

Monitoring the presence of sleepiness on the job and its effects on performance is of primary importance for improving schedule systems of shiftworkers. Shiftworkers, often involved in night-time operations and irregular work schedules, frequently complain of nocturnal sleepiness especially in conditions of abrupt shift of the wake-sleep cycle. In this study, the authors evaluated the effects of a laboratory simulation of acute night-shift changes on sleepiness, vigilance and performance, using Maintenance of Wakefulness Test, Multiple Sleep Latency Test and three pencil and paper tests: Digit Symbol Substitution Test, 'Deux Barrages' Test and a 3-Letter Cancellation Task. All of the tests were administered four times at 2-hourly intervals during the night after daytime sleep. Results showed that the ability to maintain wakefulness and to perform simple visuo-attentive tasks is substantially spared during the night. On the other hand, sleep tendency and performance on a more complex and monotonous task (Letter Cancellation Task) reveal, respectively, increasing sleepiness and degrading performance.

Adult↗

PubMed1998

Sleep and alertness during alternating monophasic and polyphasic rest-activity cycles.

People involved in shift work often have to face altered patterns of sleep and wakefulness. This is particularly true for schedules involving night shifts and/or fragmentation of duty periods throughout the 24-hr day. In such conditions, it can be difficult to obtain satisfactory periods of sleep, and sleepiness on duty is a frequent and dangerous occurrence. The aim of this study was to evaluate sleep and wakefulness periods of subjects whose work schedule was characterized by an alternation of 2 hours of activity and 4 hours of rest (sleep allowed), repeated 4 times throughout the 24-hr day. This schedule was alternated with 24 hours off duty. Nine healthy male volunteers were monitored by means of ambulatory polysomnography while attending their 24-hr rest-activity schedule. Sleep periods were visually scored according to standard criteria. Wake periods were visually scored using both 30 s and 5 s epochs in order to reveal episodes of drowsiness and/or microsleep. Results showed that total sleep time was substantially reduced as compared to the usual 7-8 hour monophasic nocturnal sleep. Subjects did not sleep during the first rest period (11.00-15.00). Time in sleep linearly increased in the course of the 3 remaining rest periods. Normal sleep stage distribution was substantially spared only in the last rest period (3.00-7.00 a.m.). With regard to duty periods, only a few microsleeps were detected and their number did not significantly vary across the four 2-hr activity periods. In conclusion, this rest-activity schedule, despite the considerable sleep reduction, allowed maintaining good levels of vigilance as shown by the virtual absence of EEG microsleeps. Whether future research will prove that this regimen does not cause an impairment of performance, it should be a suitable strategy for the management of continuous operations.

Adult↗

PubMed1997

Assessing vigilance through a brief pencil and paper letter cancellation task (LCT): effects of one night of sleep deprivation and of the time of day.

Behavioural effects of the lack of sleep in normal subjects have been investigated mostly by experimenter-paced choice reaction times in prolonged stimulus detection tasks. However, length and procedure complexity of these tasks limit their use in research on larger numbers of subjects. The aim of the present study was to assess the effectiveness of a brief subject-paced pencil and paper performance task, i.e. letter cancellation task (LCT) in revealing the effects of one night of sleep deprivation. In addition, the authors evaluated sleep loss and time of day effects on six Visual Analogue Scales (VAS) measuring subjective activation-deactivation. Results show that a LCT is sensitive in revealing the effects of time of day and of 24 h of sleep deprivation. Effects of sleep deprivation were also revealed by VAS data. Sleepiness, tiredness and energy scales on the VAS were also affected by time of day. Despite the sensitivity of both the LCT and VAS, there was little correspondence between performance and subjective measures.

Adult↗

PubMed1997

A finger-tapping task and a reaction time task as behavioral measures of the transition from wakefulness to sleep: which task interferes less with the sleep onset process.

The aim of this study was to assess whether a finger-tapping task (FTT), in which normal subjects repeatedly tap on a button while falling asleep, could be less disturbing and provide comparable information on the sleep onset period (SOP) with respect to a reaction-time task (RTT) to acoustic stimuli, in which the onset of sleep can be delayed by the arousing effect of the acoustic stimuli. Twelve subjects slept at their homes and six slept in a sleep laboratory for four consecutive nights. After one adaptation night and one baseline night, subjects were required to fall asleep in the third and fourth nights, bimanually performing either a RTT or a FTT. The results indicate that the FTT interfaces less with the SOP compared to the RTT and suggest that the FTT provides further advantages as a behavioral measure of the transition from wakefulness to sleep. In fact, the tapping task is associated with significantly shorter behavioral and polysomnographic sleep onset latencies and with a greater proportion of slow-wave sleep (SWS) during the transition from wakefulness to sleep compared with the RTT. Furthermore, correlations among subjective, behavioral, and electroencephalograph (EEG) latencies confirm the validity of the finger-tapping task as a behavioral measure of sleep onset.

Acoustic Stimulation↗

PubMed1997

Performance, ability to stay awake, and tendency to fall asleep during the night after a diurnal sleep with temazepam or placebo.

Sleep loss and increased sleepiness on the job are among the most prevalent problems encountered by people involved in night shift work, especially in cases of abrupt shift of the wake-sleep cycle. In such conditions, detrimental effects on performance are well documented. In these situations, to avoid decrements of performance at night, one possibility is to use hypnotics for improving the quality and quantity of daytime sleep. In this study, we evaluated the effects of 20 mg of temazepam on daytime sleep, the subsequent levels of nocturnal alertness/sleepiness, and performance in a laboratory simulation of acute night shift. For evaluating alertness, sleepiness, and performance we used, respectively, the maintenance of wakefulness test (MWT), the multiple sleep latency test (MSLT), and two pencil and paper tests: digit symbol substitution test (DSST) and deux barrages test (DBT). All tests were administered four times at 2-hour intervals during the nighttime after daytime sleep. Results showed that the ability to maintain wakefulness (MWT) and to perform some visuo-attentive tasks were substantially maintained during the night. On the other hand, sleep tendency (MSLT) linearly increased during the night. Temazepam resulted in being an effective diurnal hypnotic, increasing total sleep time with no residual detrimental effects on sleepiness and performance and with an increase in the ability to stay awake.

Adult↗

PubMed1997

Acutely shifting the sleep-wake cycle: nighttime sleepiness after diurnal administration of temazepam or placebo.

HYPOTHESIS: Sleepiness on the job is a common problem suffered by people involved in night shift work, especially in conditions of abrupt reversal of the sleep-wake cycle, such as emergencies and combat air operations. It is well known that sleepiness can severely affect alertness and performance. One of the most useful countermeasures is to take a prophylactic nap before working at irregular hours. To induce and maintain sleep in the "forbidden zones for sleep" during the day, it is possible to use suitable benzodiazepine hypnotics such as temazepam (TMZ). However, it is then necessary to monitor sleepiness and performance the night following the diurnal intake of the drug in order to evaluate possible side effects. METHODS: In this study, sleepiness was subjectively and objectively measured during the night after a daytime administration of TMZ 20 mg in soft gelatine capsules or placebo to obtain a prophylactic sleep. RESULTS AND DISCUSSION: Results showed the effectiveness of TMZ for inducing and maintaining diurnal sleep. This lengthening of total sleep time did not cause a decrease of sleepiness during the night, but no significant carry over effect of TMZ was present for nighttime sleep tendency. Both polygraphic and subjective measures of sleep latency decreased during the night. Finally, no significant relationship between the Stanford Sleepiness Scale and the Multiple Sleep Latency Test measures was found.

Adult↗

PubMed1996

Variations in sleep mentation as a function of time of night.

Mentation reports collected from sleep onset, Stage 2 and REM Stage awakenings, in the first part and in the second part of the night were analyzed both with systematic psycholinguistic and global measures. Results confirm the relationship between activation and the length of sleep mentation report shown by Antrobus. Length of the report increases with sleep time, but time does not modulate qualitative inter-stage differences. By partialling out the length of the report, many inter-stage differences disappeared; however significant differences remain in the global measure of bizarreness and in the psycholinguistic measure of visual imagery. These results cannot be explained entirely by differences in attention and memory and point to more basic differences in mental activity.

Adult↗

PubMed1995

Changes in cognitive asymmetries from waking to REM and NREM sleep.

In previous studies, a right hemisphere superiority was shown during REM sleep with respect to Wake and NREM states for right hemisphere tasks. The question can be raised whether the increasing right hemisphere performance during REM is related to right hemisphere tasks only, or whether it is of more general nature. This hypothesis was tested by giving the lateralized Consonant Recognition Task to 16 subjects during waking and upon awakenings from REM and NREM sleep. Results support the hypothesis that right hemisphere superiority in REM sleep is not restricted to right hemisphere tasks.

Adult↗

PubMed1995

The complementary relationship between waking and REM sleep in the oculomotor system: an increase of rightward saccades during waking causes a decrease of rightward eye movements during REM sleep.

Since an inverse relationship between waking and REM sleep eye movements (EMs) has been found with respect to frequency, amplitude and direction of EMs, we evaluated variations in the percentages of horizontal rapid eye movements (REMs) during REM sleep after having increased rightward saccades during waking by means of a unilateral tachistoscopic visual test administered prior to sleep. In another condition subjects were given the same 4 h testing condition prior to sleep, the only difference being that they were instructed not to move their gaze; therefore only "attentional movements" were possible. This condition served as a control for the role of oculomotor activity in the complementary relationship between waking and REM sleep eye movements. The actual increase of rightward saccades during waking resulted in a significant decrease of rightward REMs. This effect has been observed only in the condition in which rightward eye movements were increased and it is specific for REMs of amplitude similar to those which were increased during waking by the lateralized test.

Adult↗

PubMed1995

Which hemisphere falls asleep first?

Behavioral tasks (reaction times to acoustic stimuli and finger tapping tasks) performed by normal subjects when sleepy or attempting to fall asleep have been used as indices of hemispheric asymmetries during the sleep onset period. Results show a stronger impairment of the left hemisphere (right hand) both in reacting to external stimuli and in sustaining endogenous motor programs. The left hemisphere seems to fall asleep earlier than the right hemisphere.

Acoustic Stimulation↗

PubMed1995

Increase of REM duration and decrease of REM latency after a prolonged test of visual attention.

Following one adaptation night, the nocturnal sleep of nine female college students was recorded for two baseline and two experimental nights. In both experimental nights, prior to sleep the subjects performed a 4 hour long visual task requiring the recognition of letters tachistoscopically presented in the right visual hemifield. In the first experimental night eye movements were permitted, while in the second subjects were allowed only covert movements of attention while keeping their gaze on a fixation point. Results show that, as a consequence of the experimental manipulation, there is an increase of REM duration and a shortening of REM latency without any concomitant significant change in REM density and in the duration and latency of the other sleep stages. The increase of REM duration was greater in the night in which only attentional "movements" were permitted (i.e., when there is a covert orienting of attention), suggesting that a load of spatial attention might have a role in increasing REM pressure.

Adult↗