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Biomedical subjects

R T Pivik

Publications and source records attributed to R T Pivik.

At least 19 recordsLinked to original sources
PubMed2006

Event-related variations in alpha band activity during an attentional task in preadolescents: Effects of morning nutrition.

OBJECTIVE: Event-related desynchronization and synchronization (ERD/ERS) methodology was used to study interactions between nutrition, brain function, cognition and behavior in children who ate or skipped breakfast after overnight fasting. METHODS: Healthy preadolescents performed a cued visual Go/No-Go RT task after overnight fasting (Phase 1) and again (Phase 2) after eating breakfast (n=30) or continuing to fast (n=30). ERS and ERD determinations (8-10, 10-12Hz; frontal, central, parietal, occipital sites) and measures of sleep (overnight actigraphy) and blood glucose (finger sticks) were obtained. RESULTS: Feeding increased blood glucose, but the groups were similar in sleep amount and response accuracy. Between-phase comparisons showed slower RT and increased alpha synchronization in fasting subjects, but little change in those who ate breakfast. Phase 2 group differences emphasized greater frontal early ERS and late frontal-central ERD in Fed subjects. CONCLUSIONS: In preadolescents a brief extension of overnight fasting resulted in significant changes in brain activity and behavior that were effectively countered by eating breakfast. Delaying breakfast until mid-morning appeared to have introduced fasting effects that attenuated responses in Fed subjects. SIGNIFICANCE: These findings show the sensitivity of brain function and behavior to subtle variations in nutritional status and argue for greater consideration of nutritional variables in neurobehavioral studies.

Attention↗
PubMed2006

Skipping breakfast: gender effects on resting heart rate measures in preadolescents.

The cardiovascular response in children to morning nutrition has received little attention, and associated gender-related effects are virtually uninvestigated. This study evaluated resting heart-rate (HR) and heart-rate variability (HRV) in preadolescents after overnight fasting and again after eating a standardized breakfast or continuing to fast. HR increased slightly after eating and decreased significantly with continued fasting. These effects were present for both sexes. Relative to children who ate, those who continued fasting showed increases in HRV-particularly for inter-beat-interval and low frequency component (LF: 0.04-0.15 Hz) measures. Analyses revealed significant increases across variability measures for fasting children, but a selective LF decrease in those who were fed-an effect most prominent in females. Otherwise, males and females showed similar treatment-related changes in HRV. While within-gender comparisons showed similar results for HR, i.e., faster HR in fed compared with fasting males and females, respectively, fasting females-but not males-showed significantly greater increases in variability relative to their fed counterparts. Together, these findings suggest that extended overnight fasting initiates an increase in parasympathetic activity that attenuates the expected increase in cardiovascular output following a mid-morning meal. Observed gender differences were related to greater parasympathetic activity in males and to the apparent emphasis on parasympathetic regulation of LF variability. The implications of these findings for health concerns, the nature of responses to physiological and cognitive stressors, and how such differences may influence performance variables-particularly early in development when cardiovascular responses to these stressors may be more sensitive to nutritional factors-are discussed.

Child↗
PubMed2005

A new scaling method for topographical comparisons of event-related potentials.

Recent studies have demonstrated that comparisons of scalp topographical distributions of event-related potentials (ERPs) between experiment conditions may not correctly indicate underlying changes in neural sources if the signals are not scaled prior to the comparisons. This important issue was re-evaluated in this paper using both simulated and experimental data. Simulated data were generated according to 16 different brain models containing 2-4 dipole sources varying in strength, orientation, origin and number. The changes made in the strength, orientation and origin included relative changes between the sources or symmetrical changes in the sources. Experimental data were ERPs collected from 45 infants at 3 months of age. Influences of linked-ear and average references were examined. A scaling method based on relations of signal amplitudes between conditions was devised and compared with the vector method (McCarthy and Wood, 1985). While real topographic differences generated by complex changes in underlying sources were preserved, interactions between condition and electrode site due to mere strength changes were successfully identified by the new method, irrespective of reference method used. However, the vector method was not always reliable because failure to differentiate or mistakenly indicate changes in sources may occur when a linked-mastoid reference was used. The method presented in this paper is reliable and recommended prior to topographic comparisons to distinguish different types of changes in underlying neural sources.

Algorithms↗
PubMed2004

Cardiovascular effects of morning nutrition in preadolescents.

The cardiovascular response to eating has been extensively investigated in adults, but comparable data in children are lacking. In this investigation, heart-rate and heart-rate variability were evaluated in preadolescents during resting periods in the morning initially while participants maintained overnight fasting, and again after the participants either ate a standardized breakfast or continued fasting. Relative to the initial fasting period, heart rate (HR) increased slightly in fed participants and decreased significantly in those who continued to fast. These effects were associated with significant increases in low- (LF: 0.04-0.15 Hz; primarily sympathetic influences) and high-frequency (HF:0.15-0.5 Hz; parasympathetic influences) spectral components in fasting participants and with nonsignificant decreases in both components in fed participants. Although these HF changes are consistent with the observed heart-rate variations (i.e., increases and decreases in parasympathetic influence associated with decreased and increased HR, respectively), the LF increase with the slowing, and decrease with the acceleration of HR run counter to expected sympathetic effects on HR. The net effect of these modulations was unchanged sympathovagal balance (LF/HF) for fasting participants but a significant decrease for fed participants across recording periods. The results indicate that the continuation of overnight fasting is associated with a significant increase in parasympathetic activity that is attenuated by eating breakfast. Furthermore, the findings suggest that the parasympathetic contribution to the LF spectral component is significantly enhanced in preadolescents, and, consequently, the LF/HF ratio-generally considered to reflect sympathovagal balance-does not segregate sympathetic and parasympathetic influences in children.

Cardiovascular Physiological Phenomena↗
PubMed2004

Endogenous eye blinks in preadolescents: relationship to information processing and performance.

Endogenous blinks--those occurring without apparent provocation--are regulated in adults with respect to the presentation, cognitive loading, and response demands of stimuli. This investigation determined the extent to which similar regulatory and response-related relationships were evident in preadolescents during a visual continuous performance task (CPT). As in adults, increased blink incidence on task, longer blink deferral following stimuli with greater cognitive loading, and blink-facilitated motor responses to imperative stimuli were observed. Reaction times significantly decreased when the button press (BP) occurred near (+/- 200 ms) blink onset and increased across the task period on blink-free but not blink-associated trials. More blinks occurred before motor responses in females, and a reaction time (RT) advantage for males on blink-free trials was maintained across blink-associated conditions. From these results, an interpretation is developed arguing that endogenous blinks are a meaningful and integral component of sensory-motor processing, indexing times of facilitated attentional and motor response capability.

Adolescent↗
PubMed2002

Sleep in depressed and nondepressed participants with chronic low back pain: electroencephalographic and behaviour findings.

STUDY OBJECTIVES: To study the nature of sleep disturbance in depressed and nondepressed patients with chronic low back pain (CLBP). DESIGN: A controlled, consecutive 4-night polysomnographic study. PATIENTS: Participants were screened (psychologic, psychiatric, and physical) to determine their study group, and 21 participants (CLBP: 4 depressed, 6 nondepressed and 11 controls) were studied. MEASUREMENTS AND RESULTS: On all nights, standard polysomnographic sleep measures as well as midline occipital and frontal electroencephalography and respiration were recorded on a Grass Model 7 polygraph. Pain, sleep quality, and depression were also measured. Participants with CLBP reported significant levels of pain and sleep disturbance as compared to controls, but all groups had equivalent amounts of sleep and comparable sleep architecture. The electroencephalographic power spectral analyses revealed significant differences, with controls having more sigma across sites, more low beta activity occipitally and frontally than nondepressed patients with CLBP, and more occipital sigma and less high beta activity than depressed participants. Between pain subgroups, the depressed participants showed more occipital delta, more occipital and central alpha, and more high beta activity across all sites than did the nondepressed participants. CONCLUSIONS: Lower sigma power in participants with CLBP suggests less-effective sensorimotor gating that may contribute to poor sleep quality. Pain subgroup differences underscore the need to consider the influence of depression in the evaluation of sleep in clinical populations. This study controlled for many factors other than pain that may contribute to the sleep complaints in this population. Consequently, the absence of signs of major sleep disturbance must not be interpreted as evidence of a lack of a true sleep problem in CLBP but more likely reflects control of these factors as well as the difficulty in measuring sleep quality.

Adult↗
PubMed1999

Sleep spindles and arousal: the effects of age and sensory stimulation.

This study assessed a proposed sleep-preserving role for sleep spindles by evaluating variations in this activity as a function of factors, both naturally occurring and experimentally induced, known to affect and effect arousal from sleep. These factors included age, auditory stimulation, and experimentally induced arousal from sleep. Analyses were based on data from 84 males (5-49 yrs. old) from normal and clinical (hyperactive, enuretic, and chronic pain) populations who had participated in sleep auditory arousal threshold studies involving adaptation and 1-2 experimental nights. Spindles on experimental nights were visually analyzed and incidence determined for the two minutes preceding and throughout all Stage 2 arousal attempts. Prestimulation spindle occurrence in 39 preadolescent subjects with two experimental nights did not vary significantly from night-to-night, and prestimulation period comparisons between clinical groups and their respective controls were also non-significant. Anticipated relationships between spindle activity and indices of arousal-either inverse with respect to known variations in arousal threshold, i.e., decreases with age and across the night, or direct with respect to stimulus intensity particularly on trials when arousal did not occur-were not observed. Instead, all age groups showed significant decreases in spindle density as an increasing negative function of stimulus intensity. These findings suggest that to the extent to which sleep spindles can be considered to play a role in sleep preservation by inhibiting or attenuating potentially arousing stimuli, these effects appear to be restricted to endogenously generated stimuli and are passive rather than reactive in nature.

Acoustic Stimulation↗
PubMed1997

Elevated sleep arousal thresholds in enuretic boys: clinical implications.

Enuretic children are described as difficult to arouse from sleep. We studied auditory sleep arousal thresholds in enuretic boys and report on the clinical implications of these findings. Fifteen enuretic and 18 control subjects (7-12-year-old males) were studied in a sleep laboratory for four consecutive nights using standard polysomnographic recording techniques. Sleep was undisturbed for the initial two nights and waking thresholds were measured on the following two nights. Enuretic children wet most frequently in the first two-thirds of the night. Arousal attempts were successful 39.7% of the time in controls and only 9.3% of the time in enuretics. In conclusion, enuretic males were more difficult to arouse than age-matched controls. The elevated arousal thresholds may be due to delayed maturation. Treatment programmes that rely on awakening should be aware of these features.

Arousal↗
PubMed1996

Heart rate associated with sleep onset in preadolescents.

It is well-established that heart rate is decreased in NREM sleep relative to wakefulness, but the extent and progression of variations in heart rate when NREM sleep is first initiated, i.e. at sleep onset, have not been detailed. Furthermore, since physiological variations which have been documented during the sleep onset period have been based on studies of adult subjects, developmentally related influences on this process have not been examined. The present investigation addressed these issues by examining beat-to-beat (RR interval) changes in heart rate during the transitions between wakefulness, initial Stage 1, and subsequent Stage 2 sleep in normal and reading disabled male preadolescents who participated in a four-consecutive-night baseline sleep study. To avoid the influence of sleep deprivation or the effects of multiple sleep onset attempts, only initial, uninterrupted sleep onset periods from post-adaptation nights were selected for study. For both groups the results indicated a significant slowing of heart rate beginning 30s prior to Stage 1 onset, and a further decrease within 30s of Stage 2 onset. In addition to providing new developmental data documenting heart rate variations in the wake/sleep transition, these results complement previous reports indicating motor and autonomic changes occurring in anticipation of Stage 1 onset. These data are also relevant to an ongoing controversy regarding whether initial Stage 1 or Stage 2 sleep should be considered as the time of sleep onset. To the extent that the systematic and coordinated variations across systems may be taken as an index of state change, and in the absence of remarkable differences in these variations between Stage 1 and subsequent Stage 2, the present data are most consistent with considering initial Stage 1 as the earliest EEG sign of physiological sleep onset.

Child↗
PubMed1996

Heart rate variations during sleep in preadolescents.

Heart rate variations during sleep have been documented for infant and adult populations, but not for children and adolescents. To provide normative data for the preadolescent age group, this investigation used a combination of time-domain measures and nonlinear procedures (Poincare plots) to describe heart rate variations during two consecutive nights of undisturbed baseline sleep in 14 normal 8- to 10-year-old males. Heart rate variables, based on all-night analyses of computer-determined beat-to-beat (RR) intervals, were related to sleep stage and sleep cycle measures within and across nights. Time-domain summary statistics revealed a tendency for higher mean heart rates in rapid eye movement (REM) compared to slow-wave (SW) and stage 2 sleep, but the differences were not significant. Heart rate variability, as measured by average RR interval standard deviation, was greatest in stage 2 and least in SW sleep, but it did not vary significantly across sleep stages. Analyses of heart rate variables across the initial four sleep cycles showed a significant heart rate decrease (quadratic trend) and a significant increase (linear trend) for heart rate variability. All effects replicated across nights. Poincare plots revealed wide-ranging individual differences, generally characterized by greater dispersion at longer RR intervals and a remarkable night-to-night consistency in whole-night as well as stage-specific patterns. The sleep-stage plots uniformly indicated reduced overall range and variability in SW relative to REM and stage 2 and a general equivalence of stage 2 and REM patterns. The results indicate several features of sleep-related heart rate variations in preadolescents that differ from those in adults. The differences can be attributed to developmental variations in autonomic cardiac control and are consistent with increased parasympathetic influences reported to occur at this time.

Autonomic Nervous System↗
PubMed1994

Ontogenetic variations in auditory arousal threshold during sleep.

Developmental variations in auditory arousal thresholds during sleep were investigated in four groups of normal male subjects--children, preadolescents, adolescents, and young adults. Arousal thresholds were determined during NREM and REM sleep for tones presented via earphone insert on a single night following two adaptation nights of undisturbed sleep. Age-related relationships were observed for both awakening frequency and stimulus intensity required to effect awakening, with awakenings occurring more frequently in response to lower stimulus intensities with increasing age. Although stimulus intensities required for awakening were high and statistically equivalent across sleep stages in nonadults, higher intensity stimuli were required in Stage 4 relative to Stage 2 and REM sleep in adults. These results confirm previous observations of marked resistance to awakening during sleep in preadolescent children and suggest that processes underlying awakening from sleep undergo systematic modification during ontogenetic development.

Adolescent↗
PubMed1993

Smooth pursuit along a solid line: a new variation on the theme of efference-copy-bound eye tracking.

Theoretical considerations of the physiology of eye tracking have long implied that the kinematics of smooth pursuit need not parallel those of the pursued target, with pursuit in the absence of a physically moving target as an extreme case. Yet these theoretical implications have been largely ignored, with the consequence that observed kinematic discrepancies between target and pursuit have generally been presented as somewhat surprising, and this view has maintained unnecessary diversity among reported smooth-pursuit phenomena. The case of yet another stimulus-discrepant smooth-pursuit phenomenon is presented and is used to suggest a role which recognized eye-tracking theory might advantageously play in classifying smooth-pursuit phenomena. The new phenomenon, smooth pursuit along a stationary solid straight line under continuous illumination, was demonstrated in a study where eye movements were documented by continuous recordings of the electrooculogram. All twelve subjects were able to initiate smooth pursuit along the line and to maintain it in the absence of any other source of stimulation, and all reported experiencing apparent movement during smooth pursuit. It is suggested that smooth-pursuit phenomena can best be classified in terms of degree of efference-copy dependency.

Adolescent↗
PubMed1993

Sleep patterns in reading disabled children.

Sleep patterns in reading disabled (n = 24) and normal control (n = 15) 8-10-year-old boys were compared to examine suggested relationships among sleep, maturational and cognitive processes. Sleep was recorded in the laboratory for four consecutive nights (two adaptation, two baseline) using standard polysomnography. Analyses revealed variations across nights for both groups reflecting adaptation to the sleep laboratory, but such effects were attenuated in reading disabled subjects. Group comparisons on baseline sleep measures (nights 3 and 4 collapsed) revealed that reading disabled children showed significantly more stage 4 sleep, less rapid eye movement (REM) sleep, a longer REM onset latency and, related to this, an extended initial non-REM (NREM) cycle. Chronic sleep deprivation and maturational delay are prominent among factors that could result in such variations in sleep architecture, and these factors, alone or in combination, could impair information processing and contribute to cognitive deficits noted in reading disabled children.

Child↗
PubMed1993

Guidelines for the recording and quantitative analysis of electroencephalographic activity in research contexts.

Developments in technologic and analytical procedures applied to the study of brain electrical activity have intensified interest in this modality as a means of examining brain function. The impact of these new developments on traditional methods of acquiring and analyzing electroencephalographic activity requires evaluation. Ultimately, the integration of the old with the new must result in an accepted standardized methodology to be used in these investigations. In this paper, basic procedures and recent developments involved in the recording and analysis of brain electrical activity are discussed and recommendations are made, with emphasis on psychophysiological applications of these procedures.

Action Potentials↗