Biomedical subjects

J Trinder

Publications and source records attributed to J Trinder.

At least 19 recordsLinked to original sources

PubMed2001

The investigation of K-complex and vertex sharp wave activity in response to mid-inspiratory occlusions and complete obstructions to breathing during NREM sleep.

STUDY OBJECTIVES: To determine whether the cortical response to mid-inspiratory occlusions can be used as a model of the cortical response to obstructive events during sleep; and to determine whether the vertex sharp wave (VSW) and K-complex are exclusive contributors to the N350 and N550 components respectively of the stage 2 sleep event-related potential. DESIGN: Two types of respiratory stimuli were used to elicit evoked potential responses during stage 2 NREM sleep. These were mid-inspiratory occlusions and complete breath obstructions. Trials were grouped according to the type of phasic response elicited; isolated K-complex (KC), VSW associated with a K-complex (VSW/KC), isolated VSW, and no evoked response (other). Evoked responses were averaged separately within these categories. SETTING: Data were collected in the University of Melbourne Sleep Laboratory. PARTICIPANTS: Six young healthy male adults. INTERVENTIONS: N/A. MEASUREMENTS AND RESULTS: Data were recorded from 29 scalp sites referenced to linked ears. Mask pressure (Pm) and airflow were also recorded. Intra-thoracic pressure, as indicated by Pm, reached a more negative level following complete obstructions than brief occlusions. However, both types of respiratory stimuli elicited the two late latency components. Although latency varied across the two respiratory conditions in a manner consistent with the intra-thoracic pressure rise time differences, the elicitation characteristics and topographic distribution of these components did not vary across the two types of stimuli. In addition, an N350 was only present in the average for those categories that included VSWs, while an N550 was only present in those categories that contained K-complexes. CONCLUSIONS: Mid-inspiratory occlusions can be used as a model of obstructive events. VSWs contribute exclusively to the N350 component, while K-complexes contribute exclusively to the N550 component.

Adult↗

PubMed2001

Detecting insomnia: comparison of four self-report measures of sleep in a young adult population.

The sensitivity and specificity of four self-report measures of disordered sleep - the Sleep Impairment Index (SII), the Sleep Disorders Questionnaire (SDQ), the Dysfunctional Beliefs and Attitudes About Sleep Scale (DBAS) and the Sleep-Wake Activity Inventory (SWAI) - were compared in subjects with insomnia and normal sleep. Nineteen young adult subjects met DSM-IV criteria for primary insomnia and another 19 were normal control subjects. Discriminatory characteristics of each measure were assessed using receiver operator characteristic curve analyses. Discriminatory power was maximised for each measure to produce cut-scores applicable for identification of individuals with insomnia. The DBAS, SII and SDQ psychiatric DIMS subscale were found to correlate, and discriminated well between the two groups. The SWAI nocturnal sleep subscale was not found to be an accurate discriminator. The results suggest differences in the measures in their ability to detect insomnia, and offer guidelines as to the optimal use of test scores to identify young adults suspected of insomnia.

Adult↗

PubMed2001

Autonomic activity during human sleep as a function of time and sleep stage.

While there is a developing understanding of the influence of sleep on cardiovascular autonomic activity in humans, there remain unresolved issues. In particular, the effect of time within the sleep period, independent of sleep stage, has not been investigated. Further, the influence of sleep on central sympathetic nervous system (SNS) activity is uncertain because results using the major method applicable to humans, the low frequency (LF) component of heart rate variability (HRV), have been contradictory, and because the method itself is open to criticism. Sleep and cardiac activity were measured in 14 young healthy subjects on three nights. Data was analysed in 2-min epochs. All epochs meeting specified criteria were identified, beginning 2 h before, until 7 h after, sleep onset. Epoch values were allocated to 30-min bins and during sleep were also classified into stage 2, slow wave sleep (SWS) and rapid eye movement (REM) sleep. The measures of cardiac activity were heart rate (HR), blood pressure (BP), high frequency (HF) and LF components of HRV and pre-ejection period (PEP). During non-rapid eye movement (NREM) sleep autonomic balance shifted from sympathetic to parasympathetic dominance, although this appeared to be more because of a shift in parasympathetic nervous system (PNS) activity. Autonomic balance during REM was in general similar to wakefulness. For BP and the HF and LF components the change occurred abruptly at sleep onset and was then constant over time within each stage of sleep, indicating that any change in autonomic balance over the sleep period is a consequence of the changing distribution of sleep stages. Two variables, HR and PEP, did show time effects reflecting a circadian influence over HR and perhaps time asleep affecting PEP. While both the LF component and PEP showed changes consistent with reduced sympathetic tone during sleep, their pattern of change over time differed.

Adolescent↗

PubMed2001

A longitudinal investigation of seasonal variation in mood.

A prospective panel study was conducted to measure seasonality of mood in a random community sample in Melbourne, Australia (N = 245). Based on research into the structure of human mood, it was predicted that a lowering of mood in winter relative to summer would be observed in positive affect (PA) and behavioral engagement (BE), but not negative affect (NA). These variables were measured across summer and winter for 3 years. Consistent with the majority of research in the Northern Hemisphere, analyses on the entire sample found evidence of a small prospective season effect on the BE scale (explaining 2.1% of variance in BE scores). Also, as expected, no season effect was seen on the NA scale. In the entire sample, the season effect was not significant for PA, but joint factor analysis of the BE, PA, and NA scales confirmed that the season effect seen in the BE scale was largely due to items that were pure measures of PA. Winter pattern seasonality was both reliable across measures and significantly more marked among the subgroup of respondents who self-identified winter pattern of mood on the Seasonal Pattern Assessment Questionnaire.

Affect↗

PubMed2001

Cardiac and respiratory activity at arousal from sleep under controlled ventilation conditions.

Arousal from sleep is associated with elevated cardiac and respiratory activity. It is unclear whether this occurs because of homeostatic mechanisms or a reflex activation response associated with arousal. Cardiorespiratory activity was measured during spontaneous arousals from sleep in subjects breathing passively on a ventilator. Under such conditions, homeostatic mechanisms are eliminated. Ventilation, end-tidal PCO2, mask pressure, diaphragmatic electromyograph, heart rate, and blood pressure were measured in four normal subjects under two conditions: assisted ventilation and a normal ventilation control condition. In the control condition, there was a normal, sleep-related fall in ventilation and rise in end-tidal PCO2. Subsequently, at an arousal, there was an increase in respiratory and cardiac activity. In the ventilator condition, a vigorous cardiorespiratory response to a spontaneous arousal from sleep remained. These results indicate that sleep-related respiratory stimuli are not necessary for the occurrence of elevated cardiorespiratory activity at an arousal from sleep and are consistent with the hypothesis that such activity is at least in part due to a reflex activation response.

Adult↗

PubMed2000

The effect of arousals during sleep onset on estimates of sleep onset latency.

It is well established that insomniacs overestimate sleep-onset latency. Furthermore, there is evidence that brief arousals from sleep may occur more frequently in insomnia. This study examined the hypothesis that brief arousals from sleep influence the perception of sleep-onset latency. An average of four sleep onsets was obtained from each of 20 normal subjects on each of two nonconsecutive, counterbalanced, experimental nights. The experimental nights consisted of a control night (control condition) and a condition in which a moderate respiratory load was applied to increase the frequency of microarousals during sleep onset (mask condition). Subjective estimation of sleep-onset latency and indices of sleep quality were assessed by self-report inventory. Objective measures of sleep-onset latency and microarousals were assessed using polysomnography. Results showed that sleep-onset latency estimates were longer in the mask condition than in the control condition, an effect not reflected in objective sleep-stage scoring of sleep-onset latency. Furthermore, an increase in the frequency of brief arousals from sleep was detected in the mask condition, and this is a possible source for the sleep-onset latency increase perceived by the subjects. Findings are consistent with the concept of a physiological basis for sleep misperception in insomnia.

Adult↗

PubMed2000

Effect of age on sleep onset-related changes in respiratory pump and upper airway muscle function.

In normal young men, there is an abrupt fall in ventilation (VE), a rise in upper airway resistance (UAR), and falls in the activities of the diaphragm (Di), intercostals (IC), genioglossus (GG), and tensor palatini (TP) at sleep onset. On waking, there is an abrupt increase in VE and fall in UAR and an increase in the activities of Di, IC, GG, and TP. The aim of this study was to determine whether these changes are age dependent. Nine men aged 20 to 25 yr were compared with nine men aged 42 to 67 yr. Airflow, UAR, Di, and IC surface electromyograms (EMGs) and the intramuscular EMGs of GG and TP were recorded. It was found that the falls in IC, GG, and TP at the transition from alpha to theta electroencephalogram (EEG) activity were significantly greater in the older than in the younger men (P < 0.05) and that the fall in Di was also greater, although this was only marginally significant (P = 0.15). The rise in GG at theta-to-alpha transitions was also greater in the older than in the younger men, and there was a trend for TP to be higher.

Adolescent↗

PubMed2000

Pathophysiological interactions of ventilation, arousals, and blood pressure oscillations during cheyne-stokes respiration in patients with heart failure.

Arousals from sleep can be associated with increases in blood pressure (BP). However, it is uncertain whether this is due to a direct effect of arousals on BP, or is secondary to respiratory stimuli present at the time of the arousal. Cheyne-Stokes respiration (CSR) in patients with congestive heart failure (CHF) provides unique conditions that may allow these two possibilities to be distinguished. In CSR, the apnea-hyperpnea cycle can be dissociated from arousals because when CSR occurs during wakefulness, it does so in the absence of arousals, and when it occurs during sleep, arousals occur either at the termination of apnea (early arousals) or several breaths after the onset of hyperpnea (late arousals). We therefore measured BP during wakefulness and non-rapid eye movement (NREM) sleep in eight patients with CHF and CSR. During wakefulness, CSR was associated with wide fluctuations in systolic BP (mean +/- SD, 11.3 +/- 6.0 mm Hg) synchronous with the apnea-hyperpnea cycle, in the absence of arousals. Similar fluctuations in BP were observed during CSR with early arousals (13. 7 +/- 7.0 mm Hg) in NREM sleep. However, late arousals during CSR were associated with a small, but significant additional effect on systolic BP (14.2 +/- 7.1 mm Hg, p < 0.05). Furthermore, the degree of BP increase following arousals was directly related to the associated increase in ventilation (r = 0.70, p < 0.05). We conclude that BP fluctuations during CSR in patients with CHF are primarily related to oscillations in ventilation during the CSR cycle and can occur in the absence of arousals. Arousals augment these BP oscillations, but only when they occur late in hyperpnea.

Aged↗

PubMed1999

Affective startle modulation in clinical depression: preliminary findings.

BACKGROUND: Modulation of the startle reflex by affective foreground stimuli was investigated in a group receiving inpatient treatment for major depressive episodes (n = 14) and an age and gender matched nondepressed group (n = 14). METHODS: Participants viewed 27 pleasant, neutral, and unpleasant pictures chosen from the International Affective Picture System. Acoustic startle probes were presented during picture viewing, and participants also rated the affective qualities of the pictures. RESULTS: While ratings of the pictures were largely similar between the depressed and nondepressed groups, they displayed dissimilar patterns of startle modulation. In the nondepressed group, blinks elicited during unpleasant pictures were significantly larger than during pleasant pictures, whereas the depressed group failed to show this effect. Analyses, which separated the depressed participants into moderate and severe groups based on Beck Depression Inventory scores, revealed that while the moderately depressed group also showed a normal pattern of startle modulation, the severely depressed showed potentiated startles during the pleasant pictures. CONCLUSIONS: These preliminary results suggest that severely depressed patients may respond to some pleasant stimuli as if they are aversive, possibly because such stimuli are seen as signals of frustrative nonreward.

Acoustic Stimulation↗

PubMed1999

Cardiac activity during sleep onset.

Alterations in a number of measures of cardiac activity were examined during sleep onset in 6 participants over 3 experimental nights. Each sleep onset was divided into four consecutive phases: wakefulness, mixed alpha and theta activity, stage 2 NREM sleep with arousals, and stable stage 2 sleep. The variables measured were heart rate (HR), respiratory sinus arrhythmia (RSA), pre-ejection period (PEP) and T-wave amplitude (TWA). Respiration rate (RR) was also measured. HR and RR were lower in stable Stage 2 sleep compared with wakefulness, whereas PEP, TWA and RSA did not change significantly. During the second and third phases of sleep onset, HR decreased at each transition into sleep and increased following each spontaneous arousal. This increase resolved rapidly, with a return to sleep levels by 12 beats after the arousal. HR changes are discussed with reference to RSA, PEP, TWA and the concept of a waking reflex.

Adolescent↗

PubMed1999

Respiratory-related evoked potentials during the transition from alpha to theta EEG activity in stage 1 NREM sleep.

It has been argued previously that evoked potential components during Stage 1 sleep in response to both auditory and respiratory stimuli are intermediate between those of wakefulness and Stage 2 sleep. However, state fluctuations in the ECG between alpha and theta during Stage 1 sleep have been linked to changes in a number of respiratory functions including ventilation, upper airway resistance and chemical drive. It was therefore hypothesized that if respiratory related evoked potentials (RREP) were averaged separately for alpha and theta EEG periods during Stage 1 sleep, the alpha RREP would resemble wakefulness and the theta RREP would resemble Stage 2 sleep. RREPs were produced by 250 ms occlusions in 10 subjects. EEG was recorded from 29 scalp sites, referenced to linked ears, together with EOG and EMG. The N1 component was not specifically associated with alpha vs. theta activity, but appeared to be sensitive to any decrease in arousal level, suggesting that it was more related to attention than to changes in the EEG. The late N2 and P300 components were present during wake and Stage 1 alpha. However, in Stage 1 theta, different late components emerged (N300 and P450) that differed in latency, amplitude or topographical distribution from those seen in wakefulness. The P2 proved difficult to interpret, whereas the N550 did not appear until Stage 2 sleep, and as such, was not dependent on alpha/theta state. The results indicate that RREP components are differentially affected by the transition into sleep.

Adult↗

PubMed1999

Cardiac autonomic nervous system activity during presleep wakefulness and stage 2 NREM sleep.

Previous research has found that cardiac parasympathetic nervous system (PNS) activity increases and cardiac sympathetic nervous system (SNS) activity decreases during night-time sleep. This study aimed to examine in greater detail the time course of these changes in cardiac autonomic nervous system (ANS) activity. In the week prior to the experimental night, nine subjects maintained a constant sleep-wake schedule and experienced an adaptation night. Each subject's experimental night consisted of 2 h of presleep wakefulness, followed by a night of sleep, commencing at each subject's normal sleep onset time. One hundred and twenty beat blocks of presleep wakefulness and stable Stage 2 non-rapid eye movement (NREM) sleep across the night were selected. SNS activity was assessed using pre-ejection period, the amplitude of the T-wave in the ECG and the 0.1 Hz peak from the spectral analysis of the ECG. PNS activity was assessed using respiratory sinus arrhythmia (spectral analysis). Heart rate and respiratory rate were also measured. The results indicated a progressive decrease in SNS activity throughout sleep and a rise in PNS activity during the first half of the normal sleep period. The changes in PNS activity were similar, while the changes in SNS activity were altered, compared with a previous study in which stage of sleep was not controlled. This indicates a likely sleep stage influence on SNS activity, but not on cardiac PNS activity. These results are consistent with the concept of a primarily circadian, but not sleep, influence on PNS activity, and primarily a sleep, but not circadian, influence on SNS activity.

Adaptation, Physiological↗

PubMed1999

Ventilatory instability during sleep onset in individuals with high peripheral chemosensitivity.

Previous work has shown that the magnitude of state-related ventilatory fluctuations is amplified over the sleep-onset period and that this amplification is partly due to peripheral chemoreceptor activity, because it is reduced by hyperoxia (J. Dunai, M. Wilkinson, and J. Trinder. J. Appl. Physiol. 81: 2235-2243, 1996). These data also indicated considerable intersubject variability in the magnitude of amplification. A possible source of this variability is individual differences in peripheral chemoreceptor drive (PCD). We tested this hypothesis by measuring state-related ventilatory fluctuations throughout sleep onset under normoxic and hyperoxic conditions in subjects with high and low PCD. Results demonstrated that high-PCD subjects experienced significantly greater amplification of state-related ventilatory fluctuations than did low-PCD subjects. In addition, hyperoxia significantly reduced the amplification effect in high-PCD subjects but had little effect in low-PCD subjects. These results indicate that individuals with high PCD are likely to experience greater sleep-related ventilatory instability and suggest that peripheral chemoreceptor activity can contribute to sleep-disordered breathing.

Adult↗

PubMed1998

Load compensation as a function of state during sleep onset.

Ventilation decreases and airway resistance increases with the loss of electroencephalogram alpha activity at sleep onset. The aim of this study was to determine whether reflexive load compensation is lost immediately on the loss of alpha activity. Six healthy male subjects were studied under two conditions (load and control-no load), in three states (continuous alpha, continuous theta, and immediately after a transition from alpha to theta), and in two phases (early and late sleep onset). Ventilation and respiratory timing were measured. A comparison of loaded with control conditions indicated that loading had no effect on inspiratory minute ventilation during continuous alpha (differential effect of 0.00 l/min) and only a small, nonsignificant effect in theta immediately after phase 2 transitions (0.31 l/min), indicating a preservation of load compensation at these times. However, there were significant decreases in inspiratory minute ventilation on loaded trials during continuous theta in phase 2 (0.77 l/min) and phase 3 (1.15 l/min) and during theta immediately after a transition in phase 3 (0.87 l/min), indicating a lack of reflexive load compensation. The results indicate that, because reflex load compensation is state dependent, state-related changes in airway resistance contribute to state-related changes in ventilation during sleep onset. However, this effect was slightly delayed with transitions into theta early in sleep.

Adult↗

PubMed1998

Activity of respiratory pump and upper airway muscles during sleep onset.

Ventilation decreases at sleep onset. This change is initiated abruptly at alpha-theta electroencephalographic transitions. The aim of this study was to determine the contributions of reduced activity in respiratory pump muscles and upper airway dilator muscles to this change. Surface electromyograms over the diaphragm (Di) and intercostal muscles and fine-wire intramuscular electrodes in genioglossus (GG) and tensor palatini (TP) muscles were recorded in nine healthy young men. It was shown that phasic Di and both phasic and tonic TP activities were lower during theta than during alpha activity. Breath-by-breath analysis of the changes at alpha-theta transitions during the sleep-onset period showed a number of changes. At alpha-theta transitions, phasic activity of Di, intercostal, and GG muscles fell and rose again, and phasic and tonic activities of TP fell and remained at low levels during theta. With a state transition from theta to alpha, the phasic and tonic activities of the Di, GG, and TP increased dramatically. It is now clear that the fall in ventilation that occurs with sleep is related to a fall in activities of both upper airway dilator muscles and respiratory pump muscles.

Adolescent↗

PubMed1997

Sleep and circadian influences on cardiac autonomic nervous system activity.

To assess the separate contributions of the sleep and circadian systems to changes in cardiac autonomic nervous system (ANS) activity, 12 supine subjects participated in two 26-h constant routines, which were counterbalanced and separated by 1 wk. One routine did not permit sleep, whereas the second allowed the subjects to sleep during their normal sleep phase. Parasympathetic nervous system activity was assessed with respiratory sinus arrhythmia as measured from the spectral analysis of cardiac beat-to-beat intervals. Sympathetic nervous system activity was primarily assessed with the preejection period as estimated from impedance cardiography, although the 0.1-Hz peak from the spectral analysis of cardiac beat-to-beat intervals, the amplitude of the T wave in the electrocardiogram, and heart rate were also measured. Respiratory sinus arrhythymia showed a 24-h rhythm independent of sleep, whereas preejection period only showed a 24-h rhythm if sleep occurred. Thus the findings indicate that parasympathetic nervous system activity is mostly influenced by the circadian system, whereas sympathetic nervous system activity is mostly influenced by the sleep system.

Adult↗

PubMed1997

Gender differences in airway resistance during sleep.

At the onset of non-rapid-eye-movement (NREM) sleep there is a fall in ventilation and an increase in upper airway resistance (UAR). In healthy men there is a progressive increase in UAR as NREM sleep deepens. This study compared the pattern of change in UAR and ventilation in 14 men and 14 women (aged 18-25 yr) both during sleep onset and over the NREM phase of a sleep cycle (from wakefulness to slow-wave sleep). During sleep onset, fluctuations between electroencephalographic alpha and theta activity were associated with mean alterations in inspiratory minute ventilation and UAR of between 1 and 4.5 l/min and between 0.70 and 5.0 cmH2O . l-1 . s, respectively, with no significant effect of gender on either change (P > 0.05). During NREM sleep, however, the increment in UAR was larger in men than in women (P < 0.01), such that the mean levels of UAR at peak flow reached during slow-wave sleep were approximately 25 and 10 cmH2O . l-1 . s in men and women, respectively. We speculate that the greater increase in UAR in healthy young men may represent a gender-related susceptibility to sleep-disordered breathing that, in conjunction with other predisposing factors, may contribute to the development of obstructive sleep apnea.

Adolescent↗

PubMed1997

Correlation between ventilation and EEG-defined arousal during sleep onset in young subjects.

In studies of elderly individuals, ventilation and EEG-defined arousal have been shown to vary periodically and synchronously. Such results have been interpreted as indicating the primacy of sleep/wake state in causing ventilatory instability during sleep onset. However, because the elderly individuals studied were periodic breathers, the results do not unequivocally support this conclusion. In this study the relationship between ventilation and EEG-defined arousal was assessed in a group of 21 young, healthy men in whom ventilatory instability during sleep onset was not periodic. Ventilation and EEG (O1-A2) recordings were collected, and the longest uncontaminated periods from early and late in sleep onset were selected for subsequent analysis. The 84 time series (21 subjects, 2 variables, and 2 occasions in sleep onset) were subjected to spectral analysis to identify periodicity, and the relationship between the two variables was determined by cross-correlational methods. The results indicated that the time series were nonperiodic, yet significant correlations were observed between the two variables. The data support the view that during sleep onset ventilatory instability is driven primarily by variations in sleep/wake arousal level.

Adolescent↗