Effects of a small dose of triazolam on P300 and resting EEG

Dopaminergic and norepinephrinergic modulation of endogenous event-related potentials: A systematic review and meta-analysis

Event-related potentials (ERPs) represent the cortical processing of sensory, motor or cognitive functions invoked by particular events or stimuli. A current theory posits that the catecholaminergic neurotransmitters dopamine (DA) and norepinephrine (NE) modulate a number of endogenous ERPs during various cognitive processes. This manuscript aims to evaluate a leading neurotransmitter hypothesis with a systematic overview and meta-analysis of pharmacologic DA and NE manipulation of specific ERPs in healthy subjects during executive function. Specifically, the frontally-distributed P3a, N2, and Ne/ERN (or error-related negativity) are supposedly modulated primarily by DA, whereas the parietally-distributed P3b is thought to be modulated by NE. Based on preceding research, we refer to this distinction between frontally-distributed DA-sensitive and parietally-distributed NE-sensitive ERP components as the Extended Neurobiological Polich (ENP) hypothesis. Our systematic review and meta-analysis indicate that this distinction is too simplistic and many factors interact with DA and NE to influence these specific ERPs. These may include genetic factors, the specific cognitive processes engaged, or elements of study design, i.e. session or sequence effects or data-analysis strategies.

Effects of hypnotics on prefrontal cortex activity during a verbal fluency task in healthy male subjects: A near-infrared spectroscopy study

OBJECTIVE

To assess the effects of hypnotics on prefrontal cortex activity in healthy subjects using near-infrared spectroscopy (NIRS) in a double-blind, placebo-controlled crossover trial.

METHODS

Eighteen healthy males received acute doses of ramelteon (8 mg), triazolam (0.125 mg), or placebo in a predetermined randomization schedule, with a washout period of more than 1 week. All subjects performed a verbal fluency task during NIRS assessments at baseline and at 1 and 4 hr post-dose. The number of words correctly generated during the task (behavioral performance) and scores on the Stanford Sleepiness Scale (SSS) were also recorded at each test time.

RESULTS

Compared with the placebo, triazolam (0.125 mg) significantly decreased oxyhemoglobin (oxy-Hb) concentration change in NIRS during the posttask period and significantly increased behavioral performance, whereas triazolam (0.125 mg) and ramelteon (8 mg) significantly increased SSS scores.

CONCLUSIONS

The differential effects of two types of hypnotics on oxy-Hb change measured by NIRS were observed in acute dosing, suggesting that when assessing brain activity of patients with psychiatric disorders, researchers should consider how certain types of hypnotics can influence brain function. This would also provide useful information to clinicians when prescribing hypnotics suitable for their patients' conditions.

On the Physiological Modulation and Potential Mechanisms Underlying Parieto-Occipital Alpha Oscillations

The parieto-occipital alpha (8–13 Hz) rhythm is by far the strongest spectral fingerprint in the human brain. Almost 90 years later, its physiological origin is still far from clear. In this Research Topic I review human pharmacological studies using electroencephalography (EEG) and magnetoencephalography (MEG) that investigated the physiological mechanisms behind posterior alpha. Based on results from classical and recent experimental studies, I find a wide spectrum of drugs that modulate parieto-occipital alpha power. Alpha frequency is rarely affected, but this might be due to the range of drug dosages employed. Animal and human pharmacological findings suggest that both GABA enhancers and NMDA blockers systematically decrease posterior alpha power. Surprisingly, most of the theoretical frameworks do not seem to embrace these empirical findings and the debate on the functional role of alpha oscillations has been polarized between the inhibition vs. active poles hypotheses. Here, I speculate that the functional role of alpha might depend on physiological excitation as much as on physiological inhibition. This is supported by animal and human pharmacological work showing that GABAergic, glutamatergic, cholinergic, and serotonergic receptors in the thalamus and the cortex play a key role in the regulation of alpha power and frequency. This myriad of physiological modulations fit with the view that the alpha rhythm is a complex rhythm with multiple sources supported by both thalamo-cortical and cortico-cortical loops. Finally, I briefly discuss how future research combining experimental measurements derived from theoretical predictions based of biophysically realistic computational models will be crucial to the reconciliation of these disparate findings.

Inhibitory control in euthymic bipolar disorder: Event related potentials during a Go/NoGo task

OBJECTIVES

Patients with bipolar disorder (BD) are reported to have difficulties with inhibition, even in a euthymic state. However, the literature on cortical activity associated with response inhibition in BD remains ambiguous. This study investigates inhibition in euthymic BD using electrophysiological measures, while controlling for effects of specific medications.

METHODS

Twenty patients with BD were compared with eighteen healthy controls on a Go/NoGo task while electroencephalogram was recorded. Behavioral and event-related potential (ERP) measurements were analyzed for the two groups. Medication effects were controlled for in the analysis.

RESULTS

Patients with BD had marginally reduced NoGo N2 amplitudes and increased NoGo P3 amplitudes compared with healthy controls when patients using benzodiazepines were excluded from the study. No behavioral differences between the groups were found.

CONCLUSIONS

Reduced NoGo N2 amplitudes in BD reflect aberrant conflict detection, an early stage of the inhibition process. In addition, increased NoGo P3 amplitudes in BD despite normal task performance reflect an overactive cortical system during a simple inhibition task.

SIGNIFICANCE

Difficulties in early stages of inhibition in BD appear to have been compensated by increased cortical activation. This study extends current knowledge regarding cortical activations relating to inhibition in BD.

Cognitive Processing in Non-Communicative Patients: What Can Event-Related Potentials Tell Us?

Event-related potentials (ERP) have been proposed to improve the differential diagnosis of non-responsive patients. We investigated the potential of the P300 as a reliable marker of conscious processing in patients with locked-in syndrome (LIS). Eleven chronic LIS patients and 10 healthy subjects (HS) listened to a complex-tone auditory oddball paradigm, first in a passive condition (listen to the sounds) and then in an active condition (counting the deviant tones). Seven out of nine HS displayed a P300 waveform in the passive condition and all in the active condition. HS showed statistically significant changes in peak and area amplitude between conditions. Three out of seven LIS patients showed the P3 waveform in the passive condition and five of seven in the active condition. No changes in peak amplitude and only a significant difference at one electrode in area amplitude were observed in this group between conditions. We conclude that, in spite of keeping full consciousness and intact or nearly intact cortical functions, compared to HS, LIS patients present less reliable results when testing with ERP, specifically in the passive condition. We thus strongly recommend applying ERP paradigms in an active condition when evaluating consciousness in non-responsive patients.

How human electrophysiology informs psychopharmacology: from bottom-up driven processing to top-down control

This review surveys human event-related brain potential (ERP) and event-related magnetic field (ERF) approaches to psychopharmacology and psychopathology, and the way in which they complement behavioral studies and other neuroimaging modalities. The major paradigms involving ERP/ERF are P50 suppression, loudness-dependent auditory evoked potential (LDAEP), mismatch negativity (MMN), P300, mental chronometry, inhibitory control, and conflict processing (eg, error-related negativity (ERN)). Together these paradigms cover a range of more bottom-up driven to more top-down controlled processes. A number of relationships between the major neurotransmitter systems and electrocortical mechanisms are highlighted. These include the role of dopamine in conflict processing, and perceptual processing vs motor preparation; the role of serotonin in P50 suppression, LDAEP, and MMN; glutamate/NMDA and MMN; and the role of acetylcholine in P300 generation and memory-related processes. A preliminary taxonomy for these relationships is provided, which should be helpful in attuning possible new treatments or new applications of existing treatments to various disorders.

Effects of etizolam and ethyl loflazepate on the P300 event-related potential in healthy subjects

BACKGROUND

Benzodiazepines carry the risk of inducing cognitive impairments, which may go unnoticed while profoundly disturbing social activity. Furthermore, these impairments are partly associated with the elimination half-life (EH) of the substance from the body. The object of the present study was to examine the effects of etizolam and ethyl loflazepate, with EHs of 6 h and 122 h, respectively, on information processing in healthy subjects.

METHODS

Healthy people were administered etizolam and ethyl loflazepate acutely and subchronically (14 days). The auditory P300 event-related potential and the neuropsychological batteries described below were employed to assess the effects of drugs on cognition. The P300 event-related potential was recorded before and after drug treatments. The digit symbol test, trail making test, digit span test and verbal paired associates test were administered to examine mental slowing and memory functioning.

RESULTS

Acute administration of drugs caused prolongation in P300 latency and reduction in P300 amplitude. Etizolam caused a statistically significant prolongation in P300 latency compared to ethyl loflazepate. Furthermore, subchronic administration of etizolam, but not ethyl loflazepate, still caused a weak prolongation in P300 latency. In contrast, neuropsychological tests showed no difference.

CONCLUSIONS

The results indicate that acute administration of ethyl loflazepate induces less effect on P300 latency than etizolam.

Acute neurophysiological effects of the hypnotic zolpidem in healthy volunteers

INTRODUCTION

The imidazopyridine zolpidem is a hypnotic drug with relative selectivity for the benzodiazepine (BZP) type 1 receptor subtypes displaying a different biochemical structure to that of BZPs. Little is known of its electrophysiological effects.

PURPOSE

The aim of the present study was to investigate the acute neurophysiological effects of clinical oral doses of zolpidem.

METHODS

This was a double blind, independent group design study. Thirty-six young, healthy volunteers were randomly allocated to one of three groups--zolpidem (5 mg and 10 mg) and placebo. In addition to ERPs, behavioural measures were used to examine sedative effects of the drug.

RESULTS

ERPs were affected in a similar way to that described after sedative/hypnotic drug ingestion: increased N2 and P3 latencies and decreased N2 and P3 amplitudes. However, contrary to what is expected of a hypnotic drug, there was no change with N1 while P2 amplitude increased after the highest dose.

CONCLUSIONS

Because zolpidem showed different effects in different components, it seems to first enhance or preserve initial orienting (no change in N1), after an increase of P2 and then drastically diminish resource allocation (affecting N2 and P3 latencies and amplitudes). The study with ERPs, therefore, allows a more direct "moment to moment" investigation of finer mechanisms of changes in cerebral processes underlying the acute ingestion of the drug in question. The effects on N2 and P3 amplitudes and latencies were similar to those of other sedative/hypnotic drugs. However, zolpidem led to an unexpected increase in P2 amplitude; this effect may be related to its selective receptor binding profile and warrants further research.

Flunitrazepam-induced changes in neurophysiological, behavioural, and subjective measures used to assess sedation

INTRODUCTION

Certain features of event-related potentials (ERPs), electroencephalographic (EEG), and behavioural measures vary with differing states of alertness and/or sedation.

PURPOSE

This study was conducted to investigate changes in several measures usually viewed as reflecting states of sedation/sleepiness associated with the use of a range of doses of the hypnotic benzodiazepine (BZD) flunitrazepam (FNZ).

METHODS

This was a double blind, independent group design study of the effects of acute oral doses of FNZ in young healthy volunteers. Forty-eight subjects were randomly allocated to one of four groups-FNZ (0.6, 0.8, and 1.0 mg) and placebo (PLAC)-and tested prior to treatment and then in a posttreatment session close to the theoretical peak plasma concentration. ERP latencies and amplitudes were measured at midfrontal (Fz), midcentral (Cz), and midparietal (Pz) using a standard auditory oddball paradigm. EEG changes were assessed at Pz. Behavioural measures included the digit-symbol substitution test (DSST), a cancellation task (CT), and subjective ratings of alertness and attentiveness by the subjects (SUB) and the experimenter (EXP).

RESULTS

FNZ led to psychomotor impairments and decreased alertness and attention; these effects were consistent with previous findings. A progressive, dose-related increase in P3 latency occurred in Fz, Cz, and Pz, and there was an increase in N1 (Fz, Cz) and N2 (Fz). N2-P3 amplitude decreased in Fz. EEG power bands beta 1 increased for the two highest doses, but no significant differences were noted in theta, delta, and alpha bands. P3 latencies, experimenter-rated levels of alertness, and DSST scores differentiated all three doses of FNZ from PLAC.

CONCLUSION

The most sensitive measures used were P3 latencies of the ERPs (which varied with FNZ dose), DSST, and the experimenter-rated levels of alertness. However, we found no evidence for the assumption that one single phenomenon was reflected in all measures and different mechanisms were probably involved. Further experiments will be needed for more in-depth probing of the finer mechanisms underlying sedation/sleepiness and how they affect behavioural and eletrophysiological measures of the central nervous system (CNS) function.

Alteration of cortical EEG in mice carrying mutated human APP transgene

Transgenic mice expressing human APPswe and PS1-A264E mutations mimic certain neuropathological features of Alzheimer's disease (AD). These mice have elevated levels of the highly fibrillogenic amyloid beta1-42 peptide (Abeta42) and develop amyloid plaques around the age of 9 months. Our aim was to find whether these transgenic mice differ electrophysiologically from non-transgenic mice and whether the alteration in EEG activity progresses with the accumulation of Abeta. The APP/PS1 mice had reduced cortical theta activity and enhanced beta and gamma activity, but these changes were not age-dependent. APP single mutant mice had similar EEG alterations in theta, beta and gamma bands as APP/PS1 double mutant mice while PS1 single mutant mice did not differ from non-transgenic controls. Insoluble Abeta40 and Abeta42 levels were robustly increased in APP/PS1 double mutant mice and insoluble Abeta40 moderately increased also in APP single mutant mice. Soluble Abeta42 was found in all APP mutant mice but also in lower concentrations in PS1 single mutant mice. Plaques were deposited in 13-month-old APP/PS1 double mutant mice but not in 8-month-old double mutant or 13-month-old single mutant mice. We conclude that the alteration of EEG activity in APP/PS1 double mutant and APP single mutant mice is related to their APP genotype rather than to deposition of beta-amyloid in the brain.

The effects of benzodiazepines on event-related potential indices of automatic and controlled processing in schizophrenia: a preliminary report

The effects of benzodiazepines on cognitive function in schizophrenic patients were investigated using event-related potential (ERP) measurement during an auditory selective attention task. In this study, the authors compared the mismatch negativity (MMN) and N2b components between two subgroups of schizophrenic patients: one is comprised of patients who received no benzodiazepines (NT group, n = 7) and the other is comprised of those administered benzodiazepines in the daytime (T group, n = 7). There were no significant differences in MMN and N2b amplitudes between the two subgroups, whereas the N2b latency was significantly prolonged in the T group relative to the NT group. This suggested that benzodiazepines induce delayed stimulus classification processing in schizophrenic patients.

A double-dissociation of behavioural and event-related potential effects of two benzodiazepines with similar potencies

This study was designed to explore the role of benzodiazepine affinity to benzodiazepine binding site on acute psychomotor, subjective and memory effects, as well as auditory Event Related Potential (ERP) latencies, in healthy volunteers. Two benzodiazepines with similar affinity to benzodiazepine binding sites, or potency, were compared: the atypical compound lorazepam (2.0 mg), which has been reported to impair priming, and a standard benzodiazepine, flunitrazepam (0.6 mg, 0.8 mg, 1.0 mg). The study followed a placebo-controlled, double-blind, parallel-group design. Sixty subjects completed a test battery before treatment and at theoretical peak plasma concentration of drugs. Lorazepam and 1.0 mg of flunitrazepam led to comparable alterations on psychomotor, subjective and auditory episodic memory measures. A double-dissociation was found for lorazepam and the equipotent dose of flunitrazepam (1.0 mg): lorazepam was more deleterious than flunitrazepam in time taken to identify fragmented shapes. Lorazepam also impaired direct and indirect stem-completion in comparison to placebo, but this effect was abolished when time to identify shapes was used as a covariate. By contrast, 1.0 mg of flunitrazepam prolonged auditory ERP latencies to a greater extent than lorazepam. High affinity to the benzodiazepine binding sites does not seem to explain the consistent lorazepam-induced impairment of indirect stem-completion. Differences in impairment profile between the benzodiazepines employed may relate to the modality (visual or not) of the tasks used.

Effects of small dose of brotizolam on P300

Nine healthy men (mean age, 22.2 years) participated in two experimental sessions cross-overed randomly in a double blind manner; one with a placebo and the other with 0.125 mg of brotizolam (BTZ) administered in the morning. Resting electroencephalogram and event-related potential under oddball paradigm was recorded before and 1, 2, 4, 6 and 8 h after the administration. Mean 30-msec bin amplitude from 240 msec to 450 msec after the stimulus was compared between placebo and drug sessions in order to observe P300. Brotizolam reduced the amplitude of P300 at 6 h after administration. It was noted that the effects of BTZ were most marked at Fz.

Sleep loss and daytime sleepiness in the general adult population of Japan

There are few epidemiological studies on sleep loss and daytime sleepiness in the general adult population of Japan. A total of 4000 adult people, aged 20 and over, were randomly drawn from five areas of Japan, and 3030 individuals were interviewed and completed a questionnaire including information about sleep duration and sleep problems. Overall, 29% slept less than 6 h at night, 23% reported having insufficient sleep, and 6% took sleep enhancing medications. The prevalence rates were 21% for symptoms of insomnia and 15% for excessive daytime sleepiness. Symptoms of insomnia were more prevalent in the elderly, whereas young people were more likely to report short sleep duration, subjective insufficient sleep and excessive daytime sleepiness. A multiple logistic regression model revealed that excessive daytime sleepiness had significant associations with young people, short sleep duration, insomnia symptoms, subjective insufficient sleep and sleep enhancing medication use. Short sleep duration was the strongest predictor of excessive daytime sleepiness. The findings indicate that sleep loss and excessive daytime sleepiness in the Japanese adult population are common, and comparable to those reported in Western countries. Excessive daytime sleepiness in the general adult population seems more likely to be attributed to short sleep duration.

Effects of a small dose of triazolam on P300

Ten healthy men (mean age, 33.9 years) participated in two experimental sessions cross-overed randomly in a double-blind manner: one with the placebo and another with 0.125 mg of triazolam (TRZ). Resting electroencephalography and event-related potential under oddball paradigm were recorded before the drug administration, and 1, 2, 4, 6 and 8 h after that. P300 waveforms were analyzed by peak amplitudes and 30-ms bin data. Triazolam may cause cognitive dysfunction without general sedation or apparent sleepiness, and this effect appeared 2 h, 4 h and 6 h, most prominently 6 h, after TRZ administration.