[The jet lag syndrome].
Explore the source record for details and available documents.
Circadian Rhythm↗
Biomedical subjects
C Violani
Publications and source records attributed to C Violani.
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↗
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↗
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↗
Effects of different sleep duration on delta sleep in recovery nights.
The study assessed the effects of different amounts of sleep restriction on slow wave sleep (SWS) in the ensuing recovery nights. After one adaptation night and an 8-hr baseline night, six healthy men were individually studied during and following five nights in which sleep was reduced to 5, 4, 3, 2, and 1 hr with a 1-week interval between conditions. Each sleep reduction was followed by an 8-hr recovery night. Finally, a second 8-hr baseline night was recorded. A trend analysis revealed that SWS amount in recovery nights increases with decreasing previous sleep duration. Regression analyses showed that, within each participant, the rebound of SWS after a sleep reduction is predicted better by the total duration of sleep than by the specific amount of SWS lost.
Adult↗
Rapid eye movements density as a measure of sleep need: REM density decreases linearly with the reduction of prior sleep duration.
In the recovery nights from total and partial sleep deprivation there is a reduction of oculomotor activity during paradoxical sleep as compared to baseline nights. Aims of the present within-subjects study are to contribute in understanding the nature of the relationship between REM density and sleep need and to evaluate whether an inverse relationship exists between REM density and slow wave sleep (SWS) amount. Six healthy subjects were studied for 7 consecutive weeks with standard polysomnographic recordings. Variations in REM density were assessed in the recovery nights following a gradual sleep restriction, obtained by postponing the sleep onset time while maintaining the final awakening time constant. Results indicate that sleep curtailment decreases REM density in the ensuing recovery nights; the decrease is linearly related to the amount of sleep curtailment. The decrease in REM density parallels an increase in SWS, while no corresponding variation was found neither in the duration of paradoxical sleep nor in the latency of any other sleep stage. These results suggest that REM density could be used as a measure of sleep need.
Adult↗
Left movers' advantage in heartbeat discrimination: a replication and extension.
Lateral eye movers are subjects who consistently shift their gaze either leftward or rightward while reflecting on visuospatial or verbal questions. When reliably assessed, prevalent direction of gaze can be assumed as a valid index of hemispheric asymmetry. The present study evaluated discrimination of heartbeat (HB) and of spontaneous changes of finger temperature in 24 right-handed females reliably selected as lateral movers. Results replicate and extend previous findings by showing that left movers' superiority in HB discrimination is present also in females and concerns the perception of a different vascular function, that is, peripheral finger temperature. Differences between right movers and left movers were not due to activation level during the test or to body composition.
Adult↗
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↗
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↗
Generation of skeletal and multipart mental visual images in the cerebral hemispheres: a study in normal subjects.
In a series of three experiments the hemispheric lateralization of structures generating the details and the holistic properties of mental images was investigated in three different samples of normal right-handed subjects. In the first experiment the left hemisphere was faster in discriminating at an imagery level whether animals had short or long tails. No hemispheric dominance was found when the imagery task required the discrimination of the holistic features of objects and a decision of whether they were taller than wider, or vice versa. In the second experiment no hemispheric dominance was found when the same tasks had to be performed perceptually. In the third experiment no hemispheric dominance was found in the speed of lexical recognition of the names that in the first experiment elicited the generation of multipart and skeletal mental images, although the left hemisphere was generally more accurate. These findings provide support to the hypothesis advanced by Kosslyn that multipart mental images are generated by the left hemisphere and skeletal images by both hemispheres. Results are discussed both in terms of Kosslyn's computational theory of imagery generation and in terms of theories advanced by other authors.
Adolescent↗
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↗
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↗
Prevalent direction of reflective lateral eye movements and ear asymmetries in a dichotic test of musical chords.
Subjects who consistently move their gaze either to the right or to the left while reflecting on visuo-spatial or verbal questions are usually called "lateral eye movers". This study evaluated auditory asymmetries to a dichotic test of musical chords in 23 right-handed females, selected through test-retest as reliable lateral eye movers; 12 were "left movers" (LMs) and 11 were "right movers" (RMs). During the assessment of the prevalent direction of gaze as well as during the dichotic test, the oculomotor activity was controlled through a video camera. The hypothesis was that the left ear advantage usually found with dichotic chords is enhanced in LMs and reduced in RMs, and that this effect is not due to the facilitating influence of lateral eye movements occurring during the task. Results show that: (a) left movers exhibit a marked advantage of the left ear while right movers do not exhibit any significant ear advantage; (b) despite the instruction to fix a central point, lateral movers tend to show unwarranted eye movements in their usual direction; (c) the effect of the prevalent direction of gaze on the dichotic advantage is not due to eye movements made during the dichotic test. These findings give further support to the hypothesis that the tendency to consistently shift the gaze to one side is related to hemispheric asymmetries as measured by lateralized tests.
Adult↗
Feedback and autonomic awareness: the ability to discriminate the direction of spontaneous changes in peripheral body temperature.
Forty-eight Ss were requested to discriminate spontaneous changes of at least 0.1 degree C in their peripheral finger temperature (PFT). They were randomly assigned to one of 3 groups: in the first group ("KR") Ss were given a feedback after each discrimination; in the second group ("NKR") Ss were given no feedback after each discrimination; in the third group ("RKR") Ss were given a random feedback after each discrimination. Results indicated that in the "Knowledge-of-Results" group discrimination was significantly higher than in both "No-Knowledge-of-Results" and "Random-Knowledge-of-Results" groups. Within the first group, there was a significant difference in a discrimination index between Ss "aware" and Ss "unaware" of their PFT changes, which remained significant even when the effects of individual variability of PFT and of the regularity of PFT changes were partialled out.
Adult↗
Reflective lateral eye movements: individual styles, cognitive and lateralization effects.
The direction of gaze shifts following verbal and spatial questions was recorded by direct observation in two separate sessions in 80 right-handed Ss. Ocular events were stable over the sessions, and some Ss were classified reliably as lateral, vertical or bidirectional eye movers. No effect for type of question was found in lateral direction either in the general sample or in the bidirectional sample. Verbal questions elicited more downward movements than spatial questions. Less eye movements were found for spatial and for easy questions. These findings suggest a link between ocular motility and cognition independent of the lateralization issue.
Adult↗
Hemispheric differentiation and dream recall: subjective estimates of sleep and dreams in different handedness groups.
Previous investigations pointed to a relationship between hemispheric asymmetry and dream recall. Since handedness may reflect the extent to which cerebral organization is lateralized, it was hypothesized that differences in dream recall might exist between different handedness groups. A selected sample of 78 college students (38 right-handers, 25 left-handers, 15 mixed-handers) completed a seven-day sleep and dream diary upon final awakening, at home. Results showed that significantly more dreams are recalled by females compared to males and by right-handers compared to mixed-handers and left-handers. The latter finding is tentatively interpreted as due to a more direct access to aspects of oneiric material structured in the left hemisphere by right-handers, whose language centers are located in the same hemisphere. Unexplained findings of the only other investigation concerning handedness and sleep variables (Hicks, Pellegrini & Hawkins, 1979), which showed greater variability of sleep duration in mixed-handers, were not confirmed by the present study.
Dominance, Cerebral↗
[Hemispheric asymmetries in cortical electrical activity during sleep. I].
The hypothesis of a predominance of the right hemisphere in stage REM as compared to NREM has been tested through a spectral analysis of the EEG recorded from left (T3) and right (T4) temporal sites in 5 young healthy right-handed male subjects. Variations in the asymmetry coefficient R - L/R + L in different sleep stages have been analyzed by one way ANOVAs and Sheffé's tests. The hypothesis of a progressive increase in left hemisphere activity throughout different REM cycles as one approaches final awakenings have been investigated by comparing variations in the asymmetry coefficient for epochs of REM and stage 2 NREM sampled in different phases of the REM cycle. EEG results do not support either the hypothesized stage dependent or cycle dependent variation in EEG activity during sleep. We question whether variations in EEG amplitude and synchronization can be used as indices of hemispheric asymmetries during sleep.
Cerebral Cortex↗
[The direction of rapid eye movements as an indication of hemispheric asymmetry during REM sleep. II].
The hypothesis of right hemisphere predominance in REM sleep and of an increase in left activity throughout the night have been tested by analyzing the distribution of vertical and of horizontal rapid eye movements (REMs) to the right and to the left during the first and the last REM periods in 5 right-handed subjects. Neither the expected superiority of REMs to the left nor variations along the REM periods were found. For vertical eye movements our data suggest a superiority of upward movements during REM. In waking some empirical evidences suggest a relationship between upward eye movements and right hemisphere functioning although to date no hemispheric model can explain it.
Functional Laterality↗