Biomedical subjects

P Salzarulo

Publications and source records attributed to P Salzarulo.

At least 37 records · Page 2Linked to original sources

PubMed1997

Functional uncertainty, aging and memory processes during sleep.

Disorganized sleep patterns, can be found both during normal development and in pathological conditions. Aging could also be accompanied by a disorganization of the night sleep episode; sleep could be interrupted by spontaneous awakening, sleep cycle could be shortened or incomplete, sleep states modified. These patterns suggest an inability to sustain a stable condition, i.e. a condition of functional uncertainty. Biological and cognitive implications of functional uncertainty conditions are discussed. In particular, the hypothesis has been put forward that disturbances of sleep could have a detrimental role on memory. Recent results obtained in our lab support this hypothesis: recall is correlated with NREM-REM cycles proportion. Future research should ascertain the role of the functional uncertainty with respect to the kind of memory being involved during sleep, and establish how much and for which cognitive processes (including those involved in dream production) the inability to sustain a steady condition impairs the functioning during sleep. The duration of the functional uncertainty condition is also important. The long-term study of the link between functional uncertainty and cognitive resources, could be important for the understanding of the night life and for an adequate treatment of patients.

Adult↗

PubMed1995

Dynamics of EEG background activity level within quiet sleep in successive cycles in infants.

We investigated in infants the emergence of the trends of the EEG synchronization throughout quiet sleep (QS) as a function of the QS rank. The night sleep of 3 groups with 6 subjects each (aged respectively 9-18 weeks, 21-47 weeks, and 16-45 years) was recorded. A parameter value reflecting the degree of synchronization of the EEG background activity for successive epochs was computed by automatic analysis. For each QS phase 3 indicators of the dynamics of the time course of the EEG parameter activity were determined: the range (difference between the EEG parameter value at the beginning of the QS episode and that at the trough), the trough latency (after QS onset), and the rate of synchronization (range/trough latency). The range and the trough latency increased with age, whereas the rate of synchronization decreased. The range and the rate of synchronization decreased in the successive cycles, whereas the trough latency increased. These results provide further support for the hypothesis of the early emergence of the process S mechanisms and suggest that the framework of the 2-process model could account also for the development of both the EEG background activity dynamics and the sleep-wake organization.

Adolescent↗

PubMed1995

Delta (0.5-1.5 Hz) and sigma (11.5-15.5 Hz) EEG power dynamics throughout quiet sleep in infants.

Twenty-eight healthy infants, split into 3 groups according to age (group 1: 2-6 weeks, n = 10; group 2: 7-14 weeks, n = 10; and group 3: 4-12 months, n = 8), were recorded during the whole night. For each infant, the longest quiet sleep (QS) phase occurring between 8 p.m. and midnight was selected for EEG power spectral analysis. The power in the frequency band related to low-frequency delta waves (0.5-1.5 Hz, "delta band") and the power in the frequency band related to sigma spindles (11.5-15.5 Hz, "sigma band") were analyzed. Group 1 infants showed no significant modification of the power in the sigma band in the course of the QS phase; the power in the delta band showed a significant increase between the second and the third 5 min segment and a decrease thereafter. Group 2 infants showed a progressive reduction of the power in the sigma band, whereas the power in the delta band increased during the first 15 min. In group 3 infants, the sigma band power significantly decreased between the third and the fifth 5 min segment without further changes. The power in the delta band, on the contrary, increased progressively for the first 20 min and showed a second progressive increase beyond 35 min. For both group 2 and group 3 infants, it appeared that the change in delta power preceded the change in sigma power. The above results provide quantitative evidence that a well-defined temporal inhomogeneity pattern in the EEG of the QS phase may appear between 7 and 14 weeks of age and continues from the fourth month on.

Age Factors↗

PubMed1994

Heart rate and sleep states in infants.

Heart Rate (HR) was analyzed during the first six Quiet Sleep (QS)--Paradoxical Sleep (PS) cycles of the polygraphically-recorded nocturnal sleep in three groups of six infants each, aged respectively 1 to 2 weeks, 15 to 19 weeks, and 25 to 47 weeks. HR decreased with age, and was higher during PS than during QS, without difference between odd QS phases (1st, 3rd and 5th, which contain always, but only in oldest infant's group, Slow wave sleep (SWS) stage 3 and 4 episodes), and even QS phases (2nd, 4th and 6th, never containing SWS episodes). In the oldest infant's group, in odd QS phase only, HR was higher in the first half with respect to the second half. The HR modulation according to the QS-PS alternance was obvious in all infant groups. In the oldest infant's group the QS phases without SWS episodes were characterized by a dissociation between EEG activity level (close to that of PS) and HR (similar to that of QS phases with SWS); in QS phases with SWS, however, the HR was modulated according to the type of EEG activity (stage 2 vs SWS).

Analysis of Variance↗

PubMed1994

Electromyographic activity and sleep states in infants.

The electromyographic (EMG) activity in infants was studied in relationship to sleep states and age using an automatic method. One night of sleep in 23, healthy, full-term infants was recorded. Based on 10-second measures of chin EMG activity, two parameters were derived: 1) the tonic EMG and 2) the EMG instability (corresponding to phasic events). Age comparisons were made between young (2-11 weeks) and older infants (21-47 weeks) and between two subgroups of young infants (2-3 weeks and 7-11 weeks). State comparisons were made between paradoxical sleep (PS) and quiet sleep (QS) and, for the older infants, between QS with and without slow-wave sleep. QS tonic level did not differ either between age groups or between QS+ and QS- phases. The EMG instability was larger in PS than in QS for all age groups, and larger in the young than in the older infants, although within the group of young infants no differences between age subgroups were found.

Electromyography↗

PubMed1994

Trends in electroencephalographic synchronization across nonrapid eye movement sleep in infants.

The trend of synchronized (high-voltage, low-frequency) electroencephalographic (EEG) activity was determined across nonrapid eye movement (NREM) sleep periods of night sleep in two groups of infants (eight "young infants", age 2-19 weeks; eight "older infants", age 21-54 weeks) and, a reference, in a group of eight adults (age 16-45 years). By automatic analysis of the sleep EEG, a parameter was derived that represents the degree of synchronized (high-amplitude, low-frequency) EEG activity for successive 30-second epochs. For each subject, the average level of EEG synchronization for each NREM period and the time of the NREM period midpoints were determined. In all three groups, synchronized EEG activity tended to decrease across successive NREM periods. This trend was weaker for infants than for adults and, surprisingly, weaker for older than for young infants. This suggests that the decreasing trend typical for adults is already present in the first months after birth. The difference in trend between infants and adults may be caused by differences in the 24-hour sleep-wakefulness distribution, whereas the distinction between young and older infants could be related to a restructuring of sleep in the second semester, in particular to the emergence of slow-wave sleep and its peculiar distribution across NREM periods of night sleep.

Adolescent↗

PubMed1993

The role of slow-wave sleep on the duration of quiet sleep in infants.

The duration of quiet sleep (QS) phases has been shown to increase during the first year of life. Slow-wave sleep (SWS) appears in about half of the QS phases beyond 20 weeks. In order to evaluate the role of SWS in the lengthening of QS phase duration during the first year of life, we looked at 48 normal full-term infants (aged between 1 and 54 weeks), recorded for a whole-night period. Records included electro-encephalogram (EEG) and other polygraphic parameters. Infants were separated into two groups: (1) those who did not show SWS episodes at all, and (2) those who show both QS phases with (QS SWS+) and without (QS SWS-) SWS episodes. In group 2 the duration of QS SWS+ was longer than that of QS SWS, as well as longer than that of QS of group 1. Group 1 had a duration of QS phases similar to that of QS SWS-. The duration of QS SWS+ depended both on the SWS latency and SWS duration. The lengthening of QS phases with age is accounted for by those phases containing SWS episodes, reflecting a maturational restructuring of QS.

Journal Article↗

PubMed1992

Post-natal development of sleep organization in man: speculations on the emergence of the 'S process'.

We outline the development during the first year of life of both sleep-wake patterns and internal sleep organization (sleep states, quiet sleep-paradoxical sleep cycles, and slow-wave sleep), and raise the issue of the emergence of the 'S process'. The consolidation of sleep in episodes of longer duration takes place during the night; the ability to maintain sleep after sleep onset decreases during the day in infants older than 6 months. The main contribution to the increase of longest nocturnal sleep episode duration comes from the quiet sleep, the number of quiet sleep-paradoxical sleep cycles being of minor importance. The temporal analysis of infant sleep structure showed a difference between the first and the following cycles, not only for slow wave activity in infants older than five months, but also for younger infants and for other individual physiological activities (EEG activity, respiratory and cardiac rates): is the early development of these peculiar features a sketch of the 'S Process' described in the adult?

Child Development↗

PubMed1992

Recall of mental sleep experience with or without prior verbalization.

We investigated whether verbalization of contents of mental sleep experience (MSE), just after awakening provoked during rapid eye movement (REM) sleep, facilitates subsequent recall in the morning. Twelve subjects were awakened four times in each of two experimental nights and alternately asked to recall, with or without concurrent verbalization, MSE contents preceding the awakening. In the morning, the subjects were asked to report MSEs both verbalized and nonverbalized during the night. If subjects were unable to provide a spontaneous morning report, they were prompted using a probe, which was the title given by the subjects to each MSE at the end of its verbalization or covert recall at night. Frequencies of spontaneous reports were high, regardless of whether MSEs had been previously verbalized or not. The proportions of spontaneous and probed reports were similar for verbalized and nonverbalized MSEs, but spontaneous morning reports were longer than probed ones, regardless of their previous verbalization. Spontaneous and probed morning reports corresponding to night reports shared similar linguistic structures (i.e., length of sentences and proportions of waking-related utterances, which are indicative of difficulty of retrieval for MSE contents) and had similar percentages of contents common to night and morning reports. These findings support the hypothesis that verbalization does not directly influence the further accessibility of MSE contents.

Adult↗

PubMed1991

Oxygen consumption during sleep in children under continuous and cyclic nutrition.

The present study investigated the effects of two modalities of parenteral nutrition (continuous nutrition over the 24-hour period vs. cyclic nutrition, i.e., administered only during the night) on O2 consumption during sleep in children affected by severe gastrointestinal diseases. In both feeding modalities O2 consumption was always highest in REM sleep, intermediate in stage 2 and lowest in SWS. The trends during the night of O2 consumption (an increase from the second to the third part of the night) for different sleep stages were comparable in both feeding modalities. These results suggest that O2 consumption is not affected by the feeding modalities investigated, but is dependent on both sleep stages and time of night.

Cerebral Cortex↗

PubMed1991

The distribution of slow-wave sleep across the night: a comparison for infants, children, and adults.

This study describes the temporal distribution of slow-wave sleep (SWS) (defined as the visually scored stages 3 + 4) across the night for 16 infants aged between 20 weeks and 1 year, 17 children between 1 and 6 years, and 17 adults between 20 and 36 years. In all three groups the amounts of SWS peaked during the first nonrapid eye movement (NREM) episode. SWS decreased across the night for adults and children, but not for infants. In infants the amounts of SWS remained at a fairly constant level from the second cycle onward, although many cycles were observed with zero SWS. The latter was evident from the very low tendency for SWS to appear in consecutive NREM/REM cycles. Rather, SWS was observed in alternate cycles. In children this phenomenon was less prominent but still well visible, and the tendency for SWS to appear in consecutive cycles had increased. In adults SWS occurred predominantly in consecutive cycles. The results suggest that whereas REM recurrence time increases twofold from infancy to adulthood, SWS recurrence time remains of similar length in infants, children, and adults.

Adult↗

PubMed1990

Developmental changes in the clustering pattern of sleep rapid eye movement activity during the first year of life: a Markov-process approach.

Findings are presented in support of the hypothesis that the tendency of sleep rapid eye movement (REM) activity to group into burst structures changes with age during the first year of life in normal infants. Specifically, by assuming a markovian model for the generation of 1 sec long units of REM activity, it is shown that the propensity of those units to develop a sustained clustering pattern may increase during the first 2 months, possibly reaching a plateau at about 4 months. On the other hand, the overall density of REM activity units may continue to increase beyond that point in time.

Age Factors↗

PubMed1989

Effect of early human malnutrition on waking and sleep organization.

In order to evaluate the effect of early human malnutrition (EHM) on waking and sleep organization, a group of 12 infants malnourished (M) from birth were investigated in their first year of life through 24-h polygraphic recordings. The same infants were recorded again after nutritional rehabilitation (R). A group of 12 age-paired normal infants served as controls (C). Both young (less than 4 months) and older (greater than or equal to 4 months) M infants showed a distribution of classes of waking duration different from that of C while the trend with age of the longest sustained waking (LSW) is similar in M and in C infants. The durations distribution of sleep episodes does not differ between M and C infants, while the longest sustained sleep (LSS) is significantly shorter in M than in C infants. The LSW is less clearly located in the day-time and the LSS is less clearly located in the night-time in M infants as compared to C infants. The quiet sleep-paradoxical sleep cycles are significantly shorter in older M infants because of the reduction of quiet sleep. Nutritional rehabilitation tends to improve waking and sleep organization.

Child, Preschool↗

PubMed1989

Decrease of slow-wave sleep in children with prolonged absence of essential lipids intake.

Sleep measures of eight children fed by total parenteral nutrition (TPN) without essential lipids were compared to those of seven children fed by TPN receiving a daily supplementation of essential lipids. Slow wave sleep (SWS) is significantly decreased in the former group, particularly in the second half of the night, thus suggesting that lipids could be involved in sleep regulation.

Adolescent↗

PubMed1989

Interserial and intraserial interference processes in morning recall of mental sleep experience.

This study investigated ways in which predictions from interference theory might explain partial or total failure in the morning recall of mental sleep experience (MSE) episodes reported after provoked night awakening. Interference could take place either between the contents of one MSE episode (intraserial interference) or between the contents of different MSE episodes (interserial interference) and would be more likely to affect morning recall where similar (i.e., interrelated) contents in MSEs are involved. If interference were mainly intraserial, in the morning there would be no change in the difficulty of retrieving interrelated contents, whereas, if it were mainly interserial, there would be increased difficulty in the retrieval of such contents. All the possible pairs of reports obtained by awakening 8 subjects four times in REM sleep during each of four experimental nights spaced at weekly intervals were scored for interrelated contents, using Clark's (1970) system of analysis of paired units, which operates by matching linguistic features. Results showed that interrelations in morning report pairs are as frequent as in night report pairs, maintaining the same linguistic characteristics and with little transfer of contents from one MSE to another. Overall these findings are compatible with the hypothesis that interference is primarily intraserial rather than interserial. It is consequently suggested that morning recall failure may be due to temporary blocking of retrieval.

Adult↗

PubMed1988

Time course of night sleep EEG in the first year of life: a description based on automatic analysis.

The aim of this study is to describe the time course of night sleep in the first year of life. Forty-eight infants aged between 1 and 54 weeks were polygraphically recorded for 1 night. The central occipital EEG derivation was processed with a lab computer in order to obtain every 30 sec an EEG parameter value. The parameter is based on the joint frequency-amplitude distribution of the EEG and displays fluctuations between 2 extreme levels, high voltage low frequency (HVLF) and low voltage high frequency (LVHF). The range of the fluctuations between HVLF and LVHF increases from the period of 1-6 weeks to the period of 7-14 weeks. A further increase of the parameter range occurs after 24 weeks, which remains restricted to the first half of the night. The recurrence time of LVHF and HVLF episodes (possibly corresponding to quiet sleep paradoxical sleep cycles) is about 56 min and does not change with age in the first year of life.

Brain↗

PubMed1988

24-hour behavioural states distribution in continuously fed infants.

This study compared the 24-h sleep states distribution in infants fed orally with separate meals with that in infants continuously fed from birth. Sleep was polygraphically recorded for 24 h in 12 infants (aged between 6 weeks and 14 months) continuously fed since birth through an intracaval catheter, and in 12 age-paired control infants. The amount of sleep states in each six 4-h epoch of the 24-h day was evaluated. A clear decrease of the sleep amount, concerning both Paradoxical Sleep and Quiet Sleep, was observed during the day-time in infants older than 4 months, independently from the feeding condition. This result does not support the role of feeding rhythm upon the early development of sleep pattern circadian distribution.

Circadian Rhythm↗

PubMed1987

The thematic continuity of mental sleep experience in the same night.

It has been found that the contents of mental sleep experience (MSE) in rapid eye movement (REM) sleep are often interrelated. The aim of this study was to see whether this interrelatedness is better accounted for by the hypothesis that the mental sleep experience interrupted by provoked awakening is resumed when the subject returns to sleep (resumption), or by the hypothesis that the same contents are elaborated repeatedly throughout the night (iterative processing). We also aimed to gain some information as to the processes by which contents previously stored in memory are retrieved and inserted into the current MSE. Ten subjects were awakened 4 times on each of 4 nights after 9 min of REM sleep, and the contents of all the possible pairings of reports were scored and compared with respect to the factors "night" (same/different), "report continguity" (contiguous/noncontinguous reports), "unit interrelated" (lexical/propositional), and "interrelationship" (paradigmatic/syntagmatic). Both the occurrences and the frequencies of interrelations were greater for same night pairs than for different night pairs, but without significant differences between contiguous and noncontiguous pairs: these data provide support for the iterative processing hypothesis. The units interrelated in pairs of reports are more frequently at a lexical than a propositional level and show more paradigmatic than syntagmatic interrelationships: these data suggest that the reelaboration of contents of previous MSEs occurs mainly at a local level, making for the coherence, rather than the thematic, progression of the MSE narrative.

Adult↗