Features of the non-contact carotid pressure waveform: Cardiac and vascular dynamics during rebreathing.

This report amplifies and extends prior descriptions of the use of laser Doppler vibrometry (LDV) as a method for assessing cardiovascular activity, on a non-contact basis. A rebreathing task (n = 35 healthy individuals) was used to elicit multiple effects associated with changes in autonomic drive as well as blood gases including hypercapnia. The LDV pulse was obtained from two sites overlying the carotid artery, separated by 40 mm. A robust pulse signal was obtained from both sites, in accord with the well-described changes in carotid diameter over the blood pressure cycle. Emphasis was placed on extracting timing measures from the LDV pulse, which could serve as surrogate measures of pulse wave velocity (PWV) and the associated arterial stiffness. For validation purposes, a standard measure of pulse transit time (PTT) to the radial artery was obtained using a tonometric sensor. Two key measures of timing were extracted from the LDV pulse. One involved the transit time along the 40 mm distance separating the two LDV measurement sites. A second measure involved the timing of a late feature of the LDV pulse contour, which was interpreted as reflection wave latency and thus a measure of round-trip travel time. Both LDV measures agreed with the conventional PTT measure, in disclosing increased PWV during periods of active rebreathing. These results thus provide additional evidence that measures based on the non-contact LDV technique might provide surrogate measures for those obtained using conventional, more obtrusive assessment methods that require attached sensors.

Alcohol use disorders and anxiety disorders: relation to the P300 event-related potential.

BACKGROUND: The robust association of alcoholism with reduced P300 event-related potential amplitude has been largely established in severely affected alcoholics and their offspring. Few studies have examined the relationship of increased arousal, anxiety, and P300. In this study, we sought to determine whether P300 group differences could be discerned in well functioning individuals with less severe forms of alcohol use disorders and anxiety disorders. We were particularly interested in looking at the subgroup of alcohol use disorders accompanied by anxiety disorders. This subgroup has previously been found to have diminished alpha amplitude in the resting EEG. METHODS: Male and female community volunteers (99 unrelated index participants and 78 relatives) and 21 unrelated volunteers from an anxiety disorder clinic were interviewed by using the Schedule for Affective Disorders and Schizophrenia, Lifetime version. Blind-rated lifetime psychiatric diagnoses were assigned according to DSM-III-R criteria. Auditory and visual P300 event-related potentials were elicited with an oddball paradigm and were recorded at the midparietal (Pz) site. RESULTS: As expected, auditory P300 amplitudes were significantly reduced in participants with alcohol use disorders and significantly increased in participants with lifetime anxiety disorders. However, more detailed analysis revealed that, in an apparent paradox, auditory P300 amplitudes were lowest in individuals with comorbid alcohol use and anxiety disorders and highest in individuals with anxiety disorders alone. Visual P300 amplitudes followed the same trends but were generally not significant. CONCLUSIONS: Even in a sample of largely community-ascertained individuals, auditory P300 amplitude is reduced in alcoholics, particularly those with anxiety disorders, and is highest in nonalcoholics with anxiety disorders.

Visual P300 and the self-directedness scale of the Temperament and Character Inventory.

Reduced amplitude of the P300 event-related brain potential has been associated with several psychopathological conditions and is thought to represent brain dysfunction in such conditions. Predisposition to personality disorders and psychopathology in general is also associated with low scores on the self-directedness (SD) scale of the Temperament and Character Inventory. The present preliminary study investigated the relationship between amplitudes of P300 elicited by rare target stimuli in a visual oddball task and SD scores in 58 healthy participants. P300 was found to be significantly reduced in subjects with low SD, as supported by correlational analysis and by comparison of groups formed on the basis of SD scores. This finding may be relevant to prior findings indicating reduced P300 amplitudes in a variety of psychopathological conditions and suggests that a common vulnerability factor, reflected in the low SD personality scores, may contribute to the P300 reduction in psychiatric populations.

The P300 brain potential is reduced in smokers.

RATIONALE: Tobacco smoking is the most prevalent type of substance abuse, yet its biobehavioral etiology is little understood. Identification of differences between smokers and non-smokers on basic characteristics of neurocognitive functioning may help to elucidate the mechanisms of tobacco dependence. OBJECTIVES: This study assessed the relationship between smoking status and the P300 component of event-related potential (ERP) while controlling for potential confounders such as alcoholism, drug abuse, and psychopathology. METHODS: The ERP responses elicited by a visual oddball task were measured at the mid-parietal site in 905 current smokers, 463 ex-smokers, and 979 never smokers. RESULTS: P300 amplitude was significantly lower in current cigarette smokers compared to never-smokers. Ex-smokers did not differ significantly from never-smokers. P300 reduction was also associated with alcoholism, drug dependence, and family density of alcoholism. However, after controlling for smoking, only family density of alcoholism remained a significant predictor of P300 amplitude. CONCLUSIONS: The results indicate a significant effect of smoking status on P300 amplitude which is additive to family history of alcoholism and suggest that either (1) long-term tobacco smoking may produce a reversible change in brain function, or (2) reduced P300 may be a marker of risk for nicotine dependence.

Factors associated with falling asleep at the wheel among long-distance truck drivers.

Data on the prevalence and hypothesized predictors of falling asleep while driving were gathered through face-to-face interviews with 593 long-distance truck drivers randomly selected at public and private rest areas and routine roadside truck safety inspections. Hypothesized predictor variables related to drivers' typical work and rest patterns, extent of daytime and night-time drowsiness, symptoms of sleep disorder, measures of driving exposure, and demographic characteristics. A sizeable proportion of long-distance truck drivers reported falling asleep at the wheel of the truck: 47.1% of the survey respondents had ever fallen asleep at the wheel of a truck, and 25.4% had fallen asleep at the wheel in the past year. Factor analysis reduced the large set of predictors to six underlying, independent factors: greater daytime sleepiness; more arduous schedules, with more hours of work and fewer hours off-duty; older, more experienced drivers; shorter, poorer sleep on road; symptoms of sleep disorder; and greater tendency to night-time drowsy driving. Based on multivariate logistic regression, all six factors were predictive of self-reported falling asleep at the wheel. Falling asleep was also associated with not having been alerted by driving over shoulder rumble strips. The results suggest that countermeasures that limit drivers' work hours and enable drivers to get adequate rest and that identify drivers with sleep disorders are appropriate methods to reduce sleepiness-related driving by truck drivers.

Genetic differences in alcohol sensitivity and the inheritance of alcoholism risk.

BACKGROUND: Substantial evidence exists for an important genetic contribution to alcohol dependence risk in women and men. It has been suggested that genetically determined differences in alcohol sensitivity may represent one pathway by which an increase in alcohol dependence risk occurs. METHODS: Telephone interview follow-up data were obtained on twins from male, female and unlike-sex twin pairs who had participated in an alcohol challenge study in 1979-81, as well as other pairs from the same Australian twin panel surveyed by mail in 1980-82. RESULTS: At follow-up, alcohol challenge men did not differ from other male twins from the same age cohort on measures of lifetime psychopathology or drinking habits; but alcohol challenge omen were on average heavier drinkers than other women. A composite alcohol sensitivity measure, combining subjective intoxication and increase in body-sway after alcohol challenge in 1979-81, exhibited high heritability (60 %). Parental alcoholism history was weakly associated with decreased alcohol sensitivity in women, but not after adjustment for baseline drinking history, or in men. High alcohol sensitivity in men was associated with substantially reduced alcohol dependence risk (OR = 0.05, 95% CI 0.01-0.39). Furthermore, significantly decreased (i.e. low) alcohol sensitivity was observed in non-alcoholic males whose MZ co-twin had a history of alcohol dependence, compared to other non-alcoholics. These associations remained significant in conservative analyses that controlled for respondents' alcohol consumption levels and alcohol problems in 1979-81. CONCLUSIONS: Men (but not women) at increased genetic risk of alcohol dependence (assessed by MZ co-twin's history of alcohol dependence) exhibited reduced alcohol sensitivity. Associations with parental alcoholism were inconsistent.

Association of low-voltage alpha EEG with a subtype of alcohol use disorders.

BACKGROUND: Neurophysiological traits may identify more homogeneous subgroups of alcoholics. Such discoveries could yield information regarding pathophysiological development, leading to more specific preventive measures and treatments. In an earlier study of 127 individuals, 59 of whom were unrelated, we found that a heritable resting Electroencephalographic (EEG) phenotype, i.e., the low-voltage alpha (LVA) trait, was associated with alcohol use disorders and anxiety disorders. METHODS: We evaluated these findings using an independent, similarly established, dataset of 120 subjects. We also extended the study to a larger set of 149 unrelated individuals from a total sample of 247 subjects for whom psychiatric diagnoses and resting EEG phenotypes were available. Blind-rated psychiatric diagnoses were formulated according to DSM-III-R criteria. RESULTS: In the replication sample, the LVA trait was again more common among subjects with anxiety disorders than among those without. In the total group of unrelated individuals, alcoholics were significantly (3 times) more likely to show the LVA trait than were nonalcoholics. Again, individuals with anxiety disorders were significantly (3 times) more likely to exhibit the LVA trait than were those without anxiety disorders. Of 11 unrelated alcoholics with anxiety disorders, seven showed the LVA trait. It was specifically the LVA trait and not low-amplitude alpha activity that was associated with alcohol use disorders. CONCLUSIONS: The results of this replication study and the analysis of the total sample of unrelated individuals support an association between LVA EEG and the subtype of alcohol use disorders associated with anxiety disorders. The LVA phenotype may be a vulnerability factor for alcohol use disorders and anxiety disorders.

Slow brain potentials in a visual-spatial memory task: topographic distribution and inter-laboratory consistency.

Slow brain electrical potentials (SPs) were investigated in a visual-spatialmemory task. Two issues were addressed: (1) the nature and topographic distribution of the potentials obtained under such conditions; and (2) the consistency of the SPs when recorded in six identically configured laboratories. Fifteen young male subjects were studied at each laboratory (total n = 90). The paradigm entailed presentations of paired-visual patterns (S1 and S2), to which subjects responded with a choice reaction time response indicating whether or not the two patterns matched. A biphasic contingent negative variation (CNV) was produced which consisted of an early symmetric component with bilateral foci at posterior temporal sites and a subsequent mid-parietal dominant wave later in the retention interval. Although the CNVs from all laboratories were similar in waveform and in topographic distribution, there were significant inter-laboratory differences in amplitude of the slow potential components. The topographic distributions of the components and the possible role of sampling effects are discussed.

Relationship of genetically transmitted alpha EEG traits to anxiety disorders and alcoholism.

We tested the hypothesis that a heritable EEG trait, the low voltage alpha (LV), is associated with psychiatric disorders. Modest to moderate evidence for genetic linkage of both panic disorder and the low voltage alpha trait to the same region of chromosome 20q has recently been reported, raising the issue of whether there is a phenotypic correlation between these traits. A total of 124 subjects including 50 unrelated index subjects and 74 relatives were studied. Alpha EEG power was measured and EEG phenotypes were impressionistically classified. Subjects were psychiatrically interviewed using the SADS-L and blind-rated by RDC criteria. Alcoholics were four times more likely to be LV (including so-called borderline low voltage alpha) than were nonalcoholic, nonanxious subjects. Alcoholics with anxiety disorder are 10 times more likely to be LV. However, alcoholics without anxiety disorder were similar to nonalcoholics in alpha power. An anxiety disorder (panic disorder, phobia, or generalized anxiety) was found in 14/17 LV subjects as compared to 34/101 of the rest of the sample (P < 0.01). Support for these observations was found in the unrelated index subjects in whom no traits would be shared by familial clustering. Lower alpha power in anxiety disorders was not state-dependent, as indicated by the Spielberger Anxiety Scale. Familial covariance of alpha power was 0.25 (P < 0.01). These findings indicate there may be a shared factor underlying the transmissible low voltage alpha EEG variant and vulnerability to anxiety disorders with associated alcoholism. This factor is apparently not rare, because LV was found in approximately 10% of unrelated index subjects and 5% of subjects free of alcoholism and anxiety disorders.

Dose-related effects of alcohol on dynamic posturography and oculomotor measures.

Four healthy male volunteers < 30 years of age participated in a blinded study of placebo versus low (0.45 g/kg lean body weight = LBW), medium (0.80 g/kg LBW) and high (1.05 g/kg LBW) dose ethanol ingestion to investigate its effect upon gaze and posture control. Serial electronystagmography and computerized platform posturography were performed at different points along each subject's blood alcohol concentration (BAC) curve as measured by breath analysis. Smooth pursuit and positional testing revealed subtle abnormalities at sub-intoxicating BACs. In addition, instability on posturography was evident on the Sensory Organization Test with no statistically significant influence observed on muscle latency testing as determined by sway analysis. We conclude that even low ethanol BAC levels produce widespread gaze and posture control effects which can be easily documented.

Decreased cingulate and precuneate glucose utilization in alcoholic Korsakoff's syndrome.

Localized cerebral glucose utilization was determined for nine abstinent alcoholic men with Korsakoff's syndrome and 10 age-matched normal men who underwent positron emission tomography with [18F]2-fluoro-2-deoxyglucose (FDG). Patients with Korsakoff's syndrome showed relatively decreased glucose utilization in cingulate and precuneate areas. These decreases persisted even after correction for group differences in ventricular and sulcal cerebrospinal fluid measured on computed tomography. Electroencephalographic recordings at the time of FDG uptake showed no group differences, a finding that demonstrates that the metabolic differences could not be explained by differences in physiological arousal at the time of scanning. It is concluded that the decreased glucose utilization in the patients reflects a disruption of memory circuitry, the Papez circuit, caused by diencephalic lesions induced by thiamine deficiency.

Improving spatial and temporal resolution in evoked EEG responses using surface Laplacians.

Spline generated surface Laplacian temporal wave forms are presented as a method to improve both spatial and temporal resolution of evoked EEG responses. Middle latency and the N1 components of the auditory evoked response were used to compare potential-based methods with surface Laplacian methods in the time domain. Results indicate that surface Laplacians provide better estimates of underlying cortical activity than do potential wave forms. Spatial discrimination among electrode sites was markedly better with surface Laplacian than with potential wave forms. Differences in the number and latencies of peaks, and their topographic distributions, were observed for surface Laplacian, particularly during the time period encompassing the middle latency responses. Focal activities were observed in surface Laplacian wave forms and topographic maps which were in agreement with previous findings from auditory evoked response studies. Methodological issues surrounding the application of spline methods to the time domain are also discussed. Surface Laplacian methods in the time domain appear to provide an improved way for studying evoked EEG responses by increasing temporal and spatial resolution of component characteristics.

Altered brain development in Turner's syndrome: an event-related potential study.

We compared event-related brain potentials (ERPs) and reaction time (RT) measures from untreated young (prepubertal and peripubertal; ages 9 to 14) and old (postpubertal; ages 15 to 20) Turner's syndrome (TS) subjects with those from normal age-matched controls. Comparisons among groups permitted the assessment of the relative roles of congenital and maturational brain alterations as possible bases of the cognitive deficits in TS. All subjects were presented with series of auditory stimuli, and they either counted one of the two stimuli or made rapid discriminative button presses to both. The results indicated that, whereas the ERPs in young TS females were essentially the same as those in their age-matched controls, the ERPs in old TS females more closely resembled those in both young groups than those in their age-matched controls. Specifically, a late (400 to 900 msec) frontal negative slow wave (Nc) in the old TS subjects failed to show the normal maturational course in which the amplitude and duration of this component steadily decreases with age. Except for slightly greater amounts of N1 amplitude in the young TS group, the latencies, amplitudes, and scalp distributions of the other ERP components (N1, P2, N2, P300) were all the same at all ages in the TS subjects and their controls. Behaviorally, both TS groups had longer RTs than their controls but, consistent with the ERP results, they did not make more errors.(ABSTRACT TRUNCATED AT 250 WORDS)

Event related potentials using visual stimulation.

Visual patterns are used to elicit event related potentials. Equipment is available for generating visual geometric patterns such as checkerboards. Slides may be used for patterns which are more complex but preparation is costly and time consuming. A variety of programs exist on PC's for making very elaborate color pictures and in most cases the programs are easy to use making them ideal for generating visual patterns for event related potential experiments. A necessary requirement in event related potential experiments is the ability to control and/or determine precisely when the stimulus is presented to the subject. We have observed that timing is a problem with stimuli generated by the PC as a result of the raster scan and use in many cases of high level system calls in the software. This paper describes a technique which allows for precise control of the time of stimulus presentation using the video control signals to the monitor.

Regional cerebral glucose utilization in chronic organic mental disorders associated with alcoholism.

Localized cerebral utilization rates for glucose (CMRglu) were determined in 10 detoxified patients with alcoholic organic mental disorders and in 7 age-equivalent normal volunteers using [18F]2-fluoro-2-deoxyglucose positron emission tomography. Although gray and white matter CMRglu were not significantly different, normalized CMRglu was increased in the left cerebellar and parietal cortical regions and decreased in the right posterior white matter and anterior temporal regions of alcoholic patients, and the pattern of regional CMRglu differed between the two groups. The results suggest functional disruption of right-sided and frontal brain regions and hyperactivity of cerebellar-cortical connections in alcoholic chronic organic mental disorders.

Stimulus presentation using a programmable signal generator.

Event related potential experiments frequently require the presentation of complicated stimulus patterns to the subject. As the complexity and number of different types of stimuli presented to the subject increase there is a corresponding increase in the amount and complexity of the equipment required to generate the stimuli. Software was developed for complex stimulus presentation which uses a programmable arbitrary/function generator. The various stimulus patterns are stored in digital form in the memory of the signal generator and can be recalled by number. Prior to presentation of a particular stimulus pattern the number of that pattern is sent by the control program to the generator for recall from memory. The signal generator is set to operate in external trigger mode and at the proper time for stimulus presentation the generator is triggered by the control program. The use of the programmable signal generator allows replacement of the typical stimulus presentation equipment such as gates, signal generators, and attenuators by this the programmable generator and provides getter flexibility as to the type and complexity of stimuli which can be generated.

Determination of average heart rate as a sign of the orienting response.

The "O wave" is one component of minute EEG signals recorded from the scalp in response to external stimuli and is one sign of the "orienting response". The orienting response is a fundamental response in which attention is turned to fresh or important sources of information. The orienting response has many signs in the autonomic nervous system including changes in heart rate. Software was developed to track changes in heart rate as an additional sign of the orienting response. Instantaneous heart rate was determined by detecting R waves and calculating the interval between successive R waves. Segments of the instantaneous heart rate, time located to the occurrence of the stimuli, were averaged to produce an average heart rate during the time interval in which the stimuli occurred. Changes in the average heart rate where found to occur in time correspondence to the "O wave" in the EEG signal and thus provide an additional measure of the orienting response.

Event-related perturbations in an electrophysiological measure of auditory sensitivity: effects of probability, intensity and repeated sessions.

It is often held that novel or salient stimuli are followed by a brief period of orienting or alerting during which sensory processes are facilitated. Evidence for such a period of facilitation was sought in a paradigm in which evoked responses to weak auditory probe stimuli were examined when given in the presence of salient foreground stimuli, which were varied in probability and intensity, and which were given in two replicate sessions. The background probe stimuli consisted of a continuous train of auditory pip stimuli delivered at a rate of 40 pips per second. Under such conditions of repetitive stimulation a steady-state rhythm (SSR), which is believed to reflect summated early and middle latency evoked responses, is established in the EEG at a corresponding frequency of 40 Hz. The 40 Hz SSR was extracted using a digital averaging and filtering technique and examined continuously for changes in amplitude and latency. The rhythm showed a brief episode during which the latencies of response were decreased. The reduction in latency was greatest at 186 ms after the foreground stimulus, at which time the latencies of individual peaks in the rhythm were reduced by about 3.5 ms. The magnitude of the latency reduction response was larger for intense and for rare stimuli, and showed long-term decrement during the second session. Event-related potential and heart rate responses to the foreground stimulus were also affected by probability, intensity and session, but not in the same pattern. It was hypothesized that the latency shift in the 40 Hz SSR reflects a brief period of sensitization during alerting or orienting responses.

Auditory and visual event-related perturbations in the 40 Hz auditory steady-state response.

The effects of salient auditory and visual 'foreground' stimuli on responses to 'background' probe stimuli were investigated. The foreground stimuli were given at long and aperiodic intervals and required a discriminative judgment. Simultaneously, evoked potentials were obtained in response to background probe auditory stimuli presented in a continuous train at about 40/sec. The 40 Hz steady-state rhythm (SSR) evoked under such conditions was extracted using digital averaging and filtering techniques and examined continuously for evidence of change in latency or amplitude during the period surrounding the foreground stimulus. Within the first 200-300 msec after the onset of an acoustic foreground stimulus the latencies of individual peaks in the rhythm were momentarily reduced by a mean of 5.5 msec. A shift in the 40 Hz rhythm was also seen following visual foreground stimuli, although the shift was about one-third that following acoustic stimuli. A latency shift of comparable magnitude was not produced by deliberate manipulation of intensity or signal-to-noise ratio of the stimuli used to evoke the rhythm. The latency shift response is discussed in terms of a transient period of sensory facilitation during orienting or alerting associated with the foreground stimuli.