The effects of body posture on resting electroencephalographic activity in sleep-deprived subjects.

OBJECTIVE: This study examined the effects of posture on the resting electroencephalographic (EEG) activity of sleep-deprived volunteers. METHODS: EEG data were collected under two conditions at 13 separate time points. Testing was performed while subjects remained in a normal seated position and then repeated while subjects stood upright. RESULTS: Results indicated that delta and theta activity progressively increased as a function of sleep loss, and that standing upright attenuated this effect. CONCLUSIONS: These results suggest that an upright posture increases EEG arousal and may be useful for counteracting fatigue in sleep-deprived individuals.     

Topographic electroencephalogram changes associated with psychomotor vigilance task performance after sleep deprivation

ObjectivesThe psychomotor vigilance task (PVT) is a widely used method for the assessment of vigilance after sleep deprivation (SDEP). However, the neural basis of PVT performance during SDEP has not been fully understood. In particular, no studies have investigated the possible relation between EEG topographical changes after sleep loss and PVT performance. The aim of the present study is to assess the EEG topographic correlates of PVT performance after SDEP.MethodsDuring 40 h of SDEP, 16 healthy male subjects were evaluated in four sessions performed at the same time (11:00 a.m. and 11:00 p.m.) of the first and second day with: (a) subjective sleepiness recordings by means of the Karolinska Sleepiness Scale (KSS); (b) EEG recordings (5 min eyes-open condition); and (c) PVT.ResultsSDEP induced a slowing of PVT reaction times (RTs), higher level of subjective sleepiness and an increase of delta, theta, alpha and beta 1 EEG activity. Only slowest PVT RTs were influenced by circadian factors, with longer RTs in the morning. Both fastest PVT RTs and KSS scores were positively correlated with post-SDEP changes in EEG theta activity, mainly in centro-posterior areas, but not with other EEG frequencies. KSS scores and PVT measures were also positively correlated.ConclusionsThese findings suggest that SDEP differently affects PVT variables, and that an increase in theta activity may be the principal EEG basis of the post-SDEP slowing of fastest PVT RTs. Similar neural mechanisms seem to underlie both performance deterioration to PVT and the increase of subjective sleepiness.     

High-dose naloxone affects task performance in normal subjects

Increasing intravenous doses of naloxone (0.3 mg/kg, 1 mg/kg, and 2 mg/kg) were administered to normal subjects. Naloxone at 2 mg/kg, but not at lower doses, impaired aspects of memory as measured by a verbal learning task which assessed the direct free recall and recognition of presented versus non-presented words of a single category (effortful processing) and the monitoring of the frequency of such presentations (automatic processing). At the same time "working" memory was left unaffected. The results suggest a role for the opioid system in some memory processes in man.     

Gender and age differences in psychomotor vigilance performance under differential sleep pressure conditions

The effects of sleep pressure and circadian phase on neurobehavioral function can be sensitively measured with the psychomotor vigilance task (PVT). We compared PVT performance in 16 young (8 men and 8 women, 20-31 years) and 16 elderly healthy subjects (8 men and 8 women, 57-74 years) during a 40-h sleep deprivation (SD, high sleep pressure) and a 40-h multiple nap protocol (NAP, low sleep pressure) under dim light and constant posture conditions in a balanced crossover design. Independent of age and sleep pressure conditions, women exhibited significantly slower reaction times (RTs) than men. This effect became more apparent with increasing time elapsed into both the 40-h NAP and SD protocol. However, women tended to have fewer premature key presses than men. Independent of gender, the elderly showed slower RTs than the young in the NAP protocol during the biological day (8-24 h) but not during the biological night (24-8 h). In the SD protocol, they had also significantly slower RTs but only during the first 16 h under low to moderate levels of sleep pressure conditions. The relative PVT performance decline after SD was significantly less pronounced in the elderly than in the young, so that both age groups exhibited similar performance decrements after 16 h into the SD protocol. Thus, nighttime- and sleep pressure-related RT slowing in the young "makes them old", or the elderly are less susceptible to circadian and wake-dependent PVT performance decrements. We interpret the gender effect as a different strategy in women when performing the PVT, although the instructions to be 'as fast as possible' were identical. Not only sleepiness and circadian phase, but also age and gender are major factors that may contribute to attentional failures in extended work shifts and during nighttime work shifts.     

Cognition and vigilance: differential effects of diazepam and buspirone on memory and psychomotor performance.

Effects of a single dose of the anxiolytic buspirone (15 mg) on memory and psychomotor performance were studied in healthy volunteers and compared to those of the classic benzodiazepine anxiolytic diazepam (15 mg). The study was performed in a double-blind, placebo-controlled way. Three groups of 12 subjects were exposed to an extended test battery before and after intake of drug or placebo. Next to this, an evaluation session took place 1 week later. Immediately after intake, diazepam exerted major effects on memory, impaired psychomotor performance and decreased alertness. In particular, long-term memory had deteriorated, which was interpreted as anterograde amnesia. One week later, more items were recalled from the predrug session compared to the number of items from the postdrug session; this was interpreted as retrograde facilitation. After intake of buspirone, there were no effects of alertness and vigilance, on psychomotor performance and on memory. One week later, a small memory decrement was noticed for verbal material, which was considered as a sign of anterograde amnesia. These results indicate that effects of anxiolytics on memory can be more easily demonstrated 1 week later than immediately after drug intake and, furthermore, that the disruptive effects of diazepam outweight the small effects of buspirone. Finally, it was established that the effects of diazepam on cognition might be mediated by its effects on alertness and vigilance and that cognitive effects are not related to the anxiolytic properties of the drug.     

Psychomotor vigilance task performance during total sleep deprivation in young and postmenopausal women

The objective of this study was to investigate the effects of age on women's performance in the psychomotor vigilance task (PVT) during total sleep deprivation (SD). A total of 46 healthy women volunteered. They belonged to two age groups: young (n=34; age range 19-30 years; 12 without, and 22 with oral contraceptives (OC); early phase of the menstrual cycle) and older (n=12; age range 60-68; postmenopausal; without hormone therapy). During a 40-h total SD, the subjects performed the PVT and the Stanford Sleepiness Scale (SSS) at 2-h intervals. At baseline, the reaction speed of the young women was faster as compared to the older women (Mann-Whitney U-test p<0.01). During SD, all the PVT measures as well as the SSS scores changed similarly in the two age groups, when the baseline performance difference in favour of the young women was taken into account (area under curve analyses, Mann-Whitney U-tests n.s.). No age difference in the time course of the SD-related deterioration in PVT performance or subjective sleepiness was observed. OC use had no effects on any of the measures during SD. After recovery sleep, young women had higher subjective sleepiness scores than older women, the sleepiness scores being highest in young women not taking OCs. In conclusion, in women, aging has no effects on the amount or the time course of the decline in PVT performance caused by total SD. OC use does not significantly affect young women's PVT performance during SD in the early phase of the menstrual cycle.     

Inferior parietal rtms affects performance in an addition task

Neuropsychological and neuroimaging studies strongly suggest that the inferior parietal cortex is important for calculation. However, the evidence from neuroimaging experiments for a left hemispheric dominance in calculation is not as clear as one would expect from the studies of patients. Often a concomitant activation of the homologous inferior parietal region of the right hemisphere is reported in the same tasks. The objective of this study was to replicate basic findings of acalculic patients and to investigate discrepancies between data from patients and results from neuroimaging studies in an addition task. Repetitive transcranial magnetic stimulation (rTMS) was applied over inferior parietal areas and the adjacent intraparietal sulcus (IPS) while subjects solved double-digit addition tasks. From studies of acalculic patients it was hypothesised that left hemispheric rTMS stimulation should result in longer reaction times (RTs) in the addition task. On addition trials without TMS subjects showed the classical problem size effect with longer RTs the larger the sum of the two operands. Magnetic stimulation over left inferior parietal areas disrupted performance significantly. The effect was specific to the left hemisphere stimulation. There was no increase in RTs for rTMS stimulation over the right hemisphere.     

Impact of cognitive task on the posture of elderly subjects with Alzheimer's disease compared to healthy elderly subjects.

The aims of this study were to analyze the effects of cognitive task on static posture in Alzheimer's disease (AD) and in healthy elderly (HE) subjects and to evaluate whether those effects were greater in AD subjects than in HE subjects. We performed a posturographic analysis on 13 subjects with mild AD (mean age, 79.7+/-5.1 years, Mini-Mental State Examination scores between 18 and 23) and on 17 HE subjects (mean age, 78.5+/-4.4 years). After watching a video sequence, the subjects were asked to maintain a stable upright posture while standing on a force platform. Then, the postural sway was measured during the following two conditions: (1) quiet standing and (2) both standing and answering questions about the video sequence. We were interested in the center of pressure (CoP) area and path. For each group, the single task was compared to the dual task for the CoP area and path. We also compared the variability of both CoP area (variation of the CoP area between the single and the dual task) and path (variation of the CoP path between the single and the dual task) between the two groups. We showed that there was no significant difference between the single and the dual task in HE subjects concerning the CoP area and path, in contrast to the AD group, and that variability of both the CoP area and path were significantly greater in the AD subjects than in the HE subjects. This finding may contribute to the risk of falls in AD patients.     

Impaired neurobehavioral alertness quantified by the psychomotor vigilance task is associated with depression in the Wisconsin Sleep Cohort study

BackgroundExcessive daytime sleepiness plays an important role in the presentation and course of mood disorders. Standard objective measures of daytime sleep propensity are of little to no value in depressive illness. This study examined the psychomotor vigilance task (PVT), an objective measure of neurobehavioral alertness, and its cross-sectional and longitudinal associations with depressive symptomatology in the Wisconsin Sleep Cohort Study.MethodsThe sample consisted of 1569 separate 10-min PVT assessments conducted in 942 unique individuals. Cross-sectional and longitudinal conditional logistic regression models were used to estimate associations between the primary outcome of depression symptomatology (adjusted Zung scale≥50) and six separate PVT variables: mean reciprocal reaction time (1/RT); total lapses (RTs≥500 msec; LAPSE); total false responses (FALSE); reciprocal of the mean of the 10% fastest (FAST) and 10% slowest (SLOW) RTs; and slope of the linear regression line for all transformed 1/RTs (SLOPE).ResultsIn fully-adjusted cross-sectional models, 1/RT, LAPSE, FAST, and SLOW were each significantly associated with depression, such that worse neurobehavioral alertness was associated with higher odds of depressive symptomatology. Similar, though attenuated, findings were observed in fully-adjusted conditional longitudinal models that examined within-subject changes in depression status in the subset of participants with repeated PVT assessments. FALSE and SLOPE were not associated with depression in either cross-sectional or conditional longitudinal models.ConclusionsThese findings suggest components of the PVT are associated with depressive symptomatology. Further research is indicated to clarify the role of the PVT in the assessment of hypersomnolence in mood disorders.     

The influence of hostility on electroencephalographic activity and memory functioning during an affective memory task.

OBJECTIVE: The purpose of this study was to examine the neural correlates of emotional learning and hostility via the use of EEG and the Auditory Affective Verbal Learning Test (AAVL). METHODS: The Cook-Medley Hostility Scale (CMHO) was used to identify right-handed men (N=16) and women (N=44) as low or high hostile. Participants were administered the positive and negative word lists of the AAVL lists, and were asked to recall the words during a 5-trial paradigm. EEG data were recorded from 19 scalp sites before and following learning trials; separate bandwidths of the EEG spectrum were analyzed. RESULTS: As predicted, completion of the negative AAVL resulted in self-reported negative mood induction. Moreover, primacy and recency effects were demonstrated with the negative and positive versions of the AAVL, respectively. Unexpectedly, high hostiles demonstrated greater right versus left hemisphere high alpha power than low hostile counterparts. Low hostiles evidenced greater alpha power and low beta power than did high hostiles. CONCLUSIONS: These results suggest differing patterns of hemispheric asymmetry and overall brain activity for low and high hostiles during emotional learning. SIGNIFICANCE: The findings are important with regard to understanding the relationship between hostility, emotional learning, and associated neural systems.     

Subjective effects and vigilance after diazepam and oxazepam in normal subjects.

Twenty-two normal subjects were given single oral doses of diazepam 5 mg, oxazepam 15 mg and placebo in a double-blind cross-over trial. Subjective effects according to a rating scale and performance on a vigilance task were assessed. The results showed a difference between each of the two drugs and placebo, but none between the drugs, with regard to the vigilance test. The results from the rating of subjective effects showed an increase in "tiredness" for both drugs, and a decreased "well-being" for oxazepam.     

Resting regional cerebral blood flow and gambling task performance in cocaine-dependent subjects and healthy comparison subjects

OBJECTIVE: Orbitofrontal cortex regional cerebral blood flow (rCBF) is lower in cocaine-dependent subjects than in non-cocaine-dependent subjects. Performance on the Gambling Task, a test of decision making, is a putative correlate of orbitofrontal cortex activity and is reportedly impaired in drug-dependent subjects. The authors tested the hypothesis that lower Gambling Task scores would be associated with lower resting orbitofrontal cortex rCBF in cocaine-dependent subjects. METHOD: Fifteen healthy comparison subjects and 13 abstinent cocaine-dependent subjects underwent resting single photon emission computed tomography to measure rCBF, after which they completed the Gambling Task. RESULTS: Resting anterior cingulate and left dorsolateral prefrontal cortex rCBF significantly correlated with performance on the Gambling Task, but orbitofrontal cortex rCBF did not. Left dorsolateral prefrontal cortex rCBF was lower in the cocaine-dependent subjects than in the comparison subjects. CONCLUSIONS: Resting anterior cingulate and dorsolateral prefrontal cortex rCBF is significantly related to decision making, as assessed by the Gambling Task.     

Dorsal visual cortex activity elicited by posture change in a visuo-tactile matching task

To investigate the process of crossmodal spatial recognition, we examined the effect of posture change on the recognition of a tactile stimulus position. The task was to judge whether a visual and a tactile stimulus, presented to the left or right, were on the same or different sides while subjects crossed or uncrossed their hands. Under a condition which removed the effect of response bias to the left and right, the dorsal visual cortex (area 18/19) and the precuneus were more activated in the crossed hands condition. The dorsal visual cortex activation suggests that the activity of brain areas classically considered to be visual cortex is affected by posture change, and reflects the reciprocal process across different modalities in spatial recognition.     

The relationships between improvements in daytime sleepiness,fatigue and depression and psychomotor vigilance task testing with CPAP use in patients with obstructive sleep apnea

ObjectiveThe purpose of this study was to determine if the subjective improvements in daytime sleepiness, fatigue and depression experienced by patients with obstructive sleep apnea (OSA) with continuous positive airway pressure (CPAP) therapy predict an objective improvement in vigilance, and whether patients with mild-to-moderate OSA differ from patients with severe OSA in this regard.MethodsA total of 182 patients underwent psychomotor vigilance task (PVT) testing and measurements of subjective daytime sleepiness, fatigue and depression at baseline and after a minimum of one month of adherent CPAP use at an adequate pressure.ResultsPatients with both mild-to-moderate (n = 92) and severe (n = 90) OSA experienced improvements in subjective daytime sleepiness, fatigue and depression, but objective improvement in vigilance was only seen in patients with severe OSA. In patients with severe OSA, while a correlation was found between improvements in daytime sleepiness and some PVT parameters, changes in subjective daytime sleepiness, fatigue and depression scores were not predictive of objective improvement in vigilance while controlling for all these subjective symptoms and for age, gender, body mass index, apnea-hypopnea index/respiratory event index and total sleep time/total recording time with pulse oximetry below 90%.ConclusionsWe found no predictive relationship between subjective improvements in daytime sleepiness, fatigue and depression and objective vigilance with CPAP use in patients with OSA. These results suggest that subjective complaints of daytime impairment and objective measures of vigilance in patients with OSA should be assessed separately while evaluating the efficacy of CPAP therapy on daytime functioning.     

Affect and vigilance performance in depressive illness

The relationships between the affective states of depression and anxiety on the one hand, and vigilance performance on the other, were examined for 10 neurotic depressive patients, 10 psychotic depressive patients and 10 normal controls. Affect did not consistently and systematically influence vigilance performance for individual subject groups.Combination of all 3 groups did however produce some significant relationships in the hypothesized directions. A significant negative relationship between severity of depressive affect and signal detection performance and a significant curvilinear (inverted U) relationship between anxiety and signal detection performance allowed confirmation of the hypotheses.The results were discussed in terms of a cognitive deficit among patients with depressive illness.     

Changes in oscillatory cortical activity related to a visuomotor task in young and elderly healthy subjects.

OBJECTIVE: In order to better understand the spatio-temporal interaction of the activated cortical areas when the movement is visuo-guided and to assess the age effect on the spatio-temporal pattern of cortical activity, we have compared a proximo-distal movement with visual-motor control and hand-eye coordination (targeting movement) with a distal and a proximal movement. METHODS: Brain's electrical activity was studied using the analysis of event-related (de)synchronizations (ERD/S) of cortical mu and beta rhythms in 17 subjects, 8 young and 9 elderly subjects. RESULTS: In both populations, we found an earlier and broader mu and beta ERD during the preparation of the targeting movement compared to distal and proximal movements, principally involving the contralateral parietal region. During the execution, a spreading over the parietocentral region during proximal movement and over the parietal region during targeting movement was observed. After the execution of proximal and targeting movements, a wider and higher beta ERS was observed only in the young subjects. In the elderly subjects, our results showed a significant decrease of beta ERS during the targeting task. CONCLUSIONS: These results suggest there was a larger recruitment of cortical areas, involving notably the parietal cortex when the movement is visuo-guided. Moreover, cerebral aging-related changes in the spatio-temporal beta ERS pattern suggests an impaired sensory integration.     

Poor working memory performance in healthy elderly adults with electroencephalographic risk of cognitive decline affects syntactic processing

ObjectiveTo examine the effects of working memory (WM) load and gender agreement on sentence processing as a function of the electroencephalographic risk (i.e., abnormally high values of theta absolute power) of cognitive decline in older adults.MethodsEvent-related potentials (ERPs) were collected from Spanish speakers (22 older adults belonged to the Risk group, mean age = 67.7 years; 22 older adults belonged to the Control group, mean age = 65.2 years) while reading sentences to detect grammatical errors. Sentences varied with regard to (1) the gender agreement of the noun and adjective, where gender of the adjective either agreed or disagreed with the noun, and (2) WM load (i.e., the number of words between the noun and adjective in the sentence).ResultsThe Risk group showed a lower percentage of correct answers and longer reaction times than the Control group. The Risk group also showed a different pattern of ERP components, which was characterized by smaller amplitude and longer latency of the P600a component under high WM load conditions.ConclusionThe findings suggest that the Risk group shows difficulties integrating information associated with the previous sentence context.SignificanceThe electroencephalographic risk factor of cognitive decline might be not only a predictor of but also an indicator of current decline.     

Direction and position factors in performance of line extension task by unilateral neglect subjects

In this study was investigated the influence of direction and position in the performance of a line extension task by patients with unilateral neglect, with the aim of exploring the role of perceptual and premotor factors in this task. Twenty-three right brain damaged patients (14 patients with left unilateral neglect) were asked to extend horizontal lines both leftward and rightward; lines were presented in three different positions (left, right and central). Patients with neglect significantly overextended the lines in all conditions, but particularly toward the sagittal mid plane of the body and leftward when the line was presented on the right. The global overextension seem to be related to concomitant hemianopsia. A crucial finding in neglect group was that left extensions reduced progressively on passing from right through central to left presentation, particularly in patients with lesions involving frontal regions or the basal ganglia. The last finding supports the hypothesis that left overextension does not exclude the coexistence of both perceptual and premotor factors (causing directional hypometria) in left unilateral neglect.