P300 latency in geriatric depression

Rapid improvements and subsequent effects in major depressive disorder patients with somatic pain using rTMS combined with sertraline

This study aims to explore changes in depression and pain for major depressive disorder (MDD) patients with somatic pain after repetitive transcranial magnetic stimulation (rTMS) using the event-related potentials (ERPs) technique. Eighty MDD patients with somatic pain were randomly assigned to drug therapy (DT) and combined therapy (CT) groups. CT group underwent intermittent theta burst stimulation over the left dorsolateral prefrontal cortex (DLPFC) with 800 pulses and 1 Hz over the right DLPFC with 800 pulses, 5 times a week for 3 weeks. All patients were given sertraline at 50-100 mg per day. All subjects were evaluated at baseline and at weeks three and six of therapy using the Hamilton Rating Scale for Depression (HAMD), Hamilton Anxiety Scale (HAMA), and Numerical Rating Scales (NRS), and the latency and amplitude of P300 and mismatch negativity (MMN) were measured. There were no significant differences in all indices between groups at baseline. At 3 weeks, HAMD subscale scores of Cognitive Impairment and NRS scores were significantly lower in the CT group than in the DT group. At 6 weeks, NRS and HAMD total scores in the CT group decreased significantly in the CT group compared with the DT group, especially for anxiety and pain, and the MMN and P300 latencies and P300 amplitude showed greater improvements. Our findings highlight that rTMS in combination with antidepressants is a rapid method of symptom improvement in patients with somatic pain with MDD and is helpful for cognitive impairment and anxiety.

Machine learning-based classification using electroencephalographic multi-paradigms between drug-naïve patients with depression and healthy controls

BACKGROUND

Electroencephalography (EEG) is a supplementary diagnostic tool in psychiatry but lacks practical usage. EEG has demonstrated inconsistent diagnostic ability because major depressive disorder (MDD) is a heterogeneous psychiatric disorder with complex pathologies. In clinical psychiatry, it is essential to detect these complexities using multiple EEG paradigms. Though the application of machine learning to EEG signals in psychiatry has increased, an improvement in its classification performance is still required clinically. We tested the classification performance of multiple EEG paradigms in drug-naïve patients with MDD and healthy controls (HCs).

METHODS

Thirty-one drug-naïve patients with MDD and 31 HCs were recruited in this study. Resting-state EEG (REEG), the loudness dependence of auditory evoked potentials (LDAEP), and P300 were recorded for all participants. Linear discriminant analysis (LDA) and support vector machine (SVM) classifiers with t-test-based feature selection were used to classify patients and HCs.

RESULTS

The highest accuracy was 94.52 % when 14 selected features, including 12 P300 amplitudes (P300A) and two LDAEP features, were layered. The accuracy was 90.32 % when a SVM classifier for 30 selected features (14 P300A, 14 LDAEP, and 2 REEG) was layered in comparison to each REEG, P300A, and LDAEP, the best accuracies of which were 71.57 % (2-layered with LDA), 87.12 % (1-layered with LDA), and 83.87 % (6-layered with SVM), respectively.

LIMITATIONS

The present study was limited by small sample size and difference in formal education year.

CONCLUSIONS

Multiple EEG paradigms are more beneficial than a single EEG paradigm for classifying drug-naïve patients with MDD and HCs.

Reduced P300 amplitude is consistently associated with trait anhedonia across repeated assessments

Understanding how event-related potentials (ERPs) change following repeated assessments is critical to advance our understanding of neural mechanisms implicated in psychopathology. Specifically, it is unclear if associations between ERPs and individual differences can be reproduced when repeatedly measured within the same participants, or if clinical characteristics impact ERP trajectories over repeated assessments. The present study assessed P300 amplitude and latency from a flanker task at four time points over one month (M = 7.24 days between assessments [SD = 1.02]) in 79 female undergraduates to examine how P300 amplitude/latency changes across repeated assessments, the presence of associations between within- and between-subjects measures of current depressive symptoms and the P300, and if between-subjects depressive symptoms moderated change in P300 over repeated assessment. Results using multilevel modeling indicated a significant reduction in P300 amplitude and latency across assessments. Individuals with increased trait anhedonia (i.e., between-subjects) exhibited reduced P300 amplitudes across assessments; there were no associations of within-subjects fluctuations in anhedonia symptoms and P300 amplitude across assessments. There was also no interaction between number of assessments and between-subjects anhedonia in relation to P300 amplitude. Unlike anhedonia, between-subjects dysphoria was unrelated to P300. These results demonstrate a relatively specific and consistent association between an attenuated P300 amplitude and trait anhedonia across repeated assessments - data that may further suggest that flanker P300 amplitude reflects hedonic and motivational processes.

Auditory event-related potentials in separating patients with depressive disorders and non-depressed controls: A narrative review

This narrative review brings together the findings regarding the differences in the auditory event-related potentials (ERPs) between patients with depressive disorder and non-depressed control subjects. These studies' results can inform us of the possible alterations in sensory-cognitive processing in depressive disorders and the potential of using these ERPs in clinical applications. Auditory P3, mismatch negativity (MMN) and loudness dependence of auditory evoked potentials (LDAEP) were the subjects of the investigation. A search in PubMed yielded 84 studies. The findings of the reviewed studies were not highly consistent, but some patterns could be identified. For auditory P3b, the common findings were attenuated amplitude and prolonged latency among depressed patients. Regarding auditory MMN, especially the amplitude of duration deviance MMN was commonly attenuated, and the amplitude of frequency deviance MMN was increased in depressed patients. In LDAEP studies, generally, no differences between depressed patients and non-depressed controls were reported, although some group differences concerning specific depression subtypes were found. This review posits that future research should investigate whether certain stimulus conditions are particularly efficient at separating depressed and non-depressed participant groups. Future studies should contrast responses in different subpopulations of depressed patients, as well as different clinical groups (e.g., depressive disorder and anxiety disorder patients), to investigate the specificity of the auditory ERP alterations for depressive disorders.

Vascular depression for radiology: A review of the construct, methodology, and diagnosis

Vascular depression (VD) as defined by magnetic resonance imaging (MRI) has been proposed as a unique subtype of late-life depression. The VD hypothesis posits that cerebrovascular disease, as characterized by the presence of MRI-defined white matter hyperintensities, contributes to and increases the risk for depression in older adults. VD is also accompanied by cognitive impairment and poor antidepressant treatment response. The VD diagnosis relies on MRI findings and yet this clinical entity is largely unfamiliar to neuroradiologists and is rarely, if ever, discussed in radiology journals. The primary purpose of this review is to introduce the MRI-defined VD construct to the neuroradiology community. Case reports are highlighted in order to illustrate the profile of VD in terms of radiological, clinical, and neuropsychological findings. A secondary purpose is to elucidate and elaborate on the measurement of cerebrovascular disease through visual rating scales and semi- and fully-automated volumetric methods. These methods are crucial for determining whether lesion burden or lesion severity is the dominant pathological contributor to VD. Additionally, these rating methods have implications for the growing field of computer assisted diagnosis. Since VD has been found to have a profile that is distinct from other types of late-life depression, neuroradiologists, in conjunction with psychiatrists and psychologists, should consider VD in diagnosis and treatment planning.

Passive Paradigm Single-Tone Elicited ERPs in Tension-Type Headaches and Migraine

The active 'oddball' event-related potential (ERP) P3 is elongated or reduced in migraine and tension-type headaches, indicating a deficit of active attention in these primary headaches. It is then reasonable to study the passive attention function in these headaches through the technology of passive paradigm singletone elicited ERPs. We invited 32 patients suffering from chronic tension-type headache (CTTH), 17 from frequent episodic tension-type headache (FETH) and 32 from interictal migraine without aura, as well as 28 healthy subjects to undergo passive paradigm single-tone ERPs. There were no statistically significant differences when the mean latencies and amplitudes of N1, P2, N2 or the mean latencies of P3 of the four groups were considered. In contrast, the P3 amplitudes were significantly reduced in the patient groups when compared with healthy controls. However, no further significant difference was found between patient groups when considering P3 amplitude. Our study demonstrated a deficit of passive attention in CTTH, FETH and migraine, but could not separate these headache types in this regard. The reduced P3 in patients might be due to the head pain experienced.

P300 latency as an indicator of severity in major depressive disorder

BACKGROUND

Depression is the most common mental health problem across all the age groups. Still diagnostic techniques and laboratory tests are awaited to confirm it. Some studies focus on P300 latency to aid in the diagnosis of depression. Hence, this study was conducted to know whether P300 latency is an indicator of major depressive disorder (MDD).

METHODS

This study was conducted both on patients admitted in the hospital and those attending outdoor clinic giving written informed consent and fulfilling inclusion/exclusion criteria from the Department of Psychiatry, S.N. Medical College and Hospital, Agra. The sample consisted of 30 consecutive patients suffering from MDD as per the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition criteria and 30 subjects as normal control. Sociodemographic and clinical history proforma, Hamilton Rating Scale for Depression (Ham-D), and P300 were administered on all 60 subjects. Data were analyzed using mean, standard deviation, and t-test.

RESULTS

Significant difference (P < 0.0001) has been found in HAM-D mean scores of depressed and nondepressed control group subjects. The mean score of depressed group was significantly high (18.066) compared to nondepressed control group (4.833). Significant difference (P < 0.0001) between the mean of P300 latency in depressed and nondepressed control subjects was also found. Mean score of P300 latency in depressed group was significantly high (346.918 ± 19.515) compared to the nondepressed control subjects (303.741 ± 6.378). There was a significant difference in the mean of P300 latency between mild and severe (P < 0.0001), mild and very severe (P < 0.0003), as well as moderate and severe (P < 0.0001) level of depression.

CONCLUSIONS

P300 latency may be used as an indicator of MDD and it is directly proportional to the severity of MDD.

Electrophysiological changes in late life depression and their relation to structural brain changes

BACKGROUND

Late life depression is often accompanied by slowed information processing during neuropsychological testing, and this has been related to underlying cerebrovascular disease. We investigated whether changes in electrophysiological markers of information processing might share the same pathological correlates.

METHODS

Differences in power spectra frequency, contingent negative variation (CNV), post-imperative negative variation (PINV), and auditory P300a amplitude and latency in 19 patients with DSM-IV major depression aged ≥ 60 years were compared with 25 recordings in age-matched healthy controls. Associations with total brain volume and degree of white matter hyperintensities (WMH) were examined in those who had undergone additional magnetic resonance imaging (MRI).

RESULTS

Compared with healthy controls, patients had more slow-wave delta (group difference: p = 0.024) and theta activity (p = 0.015) as well as alpha activity (p = 0.005) but no decrease in beta band frequency (p = 0.077). None of these changes related differently to brain volume or WMH in patients or controls. Patients further showed prolonged P300a latencies (p = 0.027), which were associated with decreased total brain volume in patients but not controls (interaction by group: p = 0.004). While there were no overall differences in PINV between both groups, patients showed a decrease in PINV magnitude with increasing WMH, a relation that was not seen in controls (interaction by group: p = 0.024).

CONCLUSION

Patients with late life depression show changes in several electrophysiological markers of cerebral arousal and information processing, some of which relate to brain atrophy and WMH on MRI.

The effects of maternal binge drinking during pregnancy on neural correlates of response inhibition and memory in childhood

BACKGROUND

Although an extensive literature has documented a broad range of cognitive performance deficits in children with prenatal alcohol exposure, little is known about how the neurophysiological processes underlying these deficits may be affected. Event-related potentials (ERPs), which reflect task-specific changes in brain electrical activity, provide a method for examining multiple constituents of cognitive processing at the neural level.

METHODS

We recorded ERPs in 217 children from Inuit communities in Arctic Quebec (M age = 11.3 years) during 2 different tasks-Go/No-go response inhibition and continuous recognition memory. Children were classified as either alcohol-exposed (ALC) or controls (CON) depending on whether the mother reported binge drinking during pregnancy.

RESULTS

Both groups performed comparably in terms of accuracy and reaction time on the tasks, and both tasks elicited the expected effects on ERPs when responses were compared across conditions. However, the ALC group showed slower P2 latencies on Go/No-go, suggesting an altered neurophysiological response associated with initial visual processing of the stimuli. On the memory task, the ALC group showed reduced FN400 amplitude to New items, known as the familiarity effect, and reduced amplitude for the late positive component, possibly reflecting impairment in memory retrieval.

CONCLUSIONS

These findings show that, even in tasks in which alcohol-exposed children exhibit behavioral performance that is comparable to controls, fetal alcohol exposure is associated with altered neurophysiological processing of response inhibition and recognition memory. The data suggest that fetal alcohol exposure is associated with reduced efficiency in the initial extracting of the meaning of a stimulus, reduced allocation of attention to the task, and poorer conscious, explicit recognition memory processing.

The effects of fetal alcohol syndrome on response execution and inhibition: an event-related potential study

BACKGROUND

Both executive function deficits and slower processing speed are characteristic of children with fetal alcohol exposure, but the temporal dynamics of neural activity underlying cognitive processing deficits in fetal alcohol spectrum disorder have rarely been studied. To this end, event-related potentials (ERPs) were used to examine the nature of alcohol-related effects on response inhibition by identifying differences in neural activation during task performance.

METHODS

We recorded ERPs during a Go/No-go response inhibition task in 2 groups of children in Cape Town, South Africa (M age = 11.7 years; range = 10 to 13)-one diagnosed with fetal alcohol syndrome (FAS) or partial FAS (FAS/PFAS; n = 7); the other, a control group whose mothers abstained or drank only minimally during pregnancy (n = 6). Children were instructed to press a "Go" response button to all letter stimuli presented except for the letter "X," the "No-go" stimulus, which occurred relatively infrequently.

RESULTS

Task performance accuracy and reaction time did not differ between groups, but differences emerged for 3 ERP components-P2, N2, and P3. The FAS/PFAS group showed a slower latency to peak P2, suggesting less efficient processing of visual information at a relatively early stage ( approximately 200 ms after stimulus onset). Moreover, controls showed a larger P2 amplitude to Go versus No-go, indicating an early discrimination between conditions that was not seen in the FAS/PFAS group. Consistent with previous literature on tasks related to cognitive control, the control group showed a well-defined, larger N2 to No-go versus Go, which was not evident in the FAS/PFAS group. Both groups showed the expected larger P3 amplitude to No-go versus Go, but this condition difference persisted in a late slow wave for the FAS/PFAS group, suggesting increased cognitive effort.

CONCLUSIONS

The timing and amplitude differences in the ERP measures suggest that slower, less efficient processing characterizes the FAS/PFAS group during initial stimulus identification. Moreover, the exposed children showed less sharply defined components throughout the stimulus and response evaluation processes involved in successful response inhibition. Although both groups were able to inhibit their responses equally well, the level of neural activation in the children with FAS/PFAS was greater, suggesting more cognitive effort. The specific deficits in response inhibition processing at discrete stages of neural activation may have implications for understanding the nature of alcohol-related deficits in other cognitive domains as well.

Differential associations of sex and D2 dopamine receptor (DRD2) genotype with negative affect and other substance abuse risk markers in children of alcoholics

Children of alcoholics have increased risk for substance abuse problems. Self-medication of negative affect may be one developmental path to future substance abuse. Because the 146 young (adolescent) children of alcoholics in the current sample had not used enough abused substances to study substance use directly, the relation of substance abuse risk markers to negative affect was assessed. Because the D2 dopamine receptor (DRD2) A1 allele has been associated with alcoholism and other substance use disorders, negative affect, measured by the Beck Depression Inventory (BDI), was determined in four groups of children: boys and girls with the A1+ allele (A1A1 and A1A2 genotypes) and with the A1- allele (A2A2 genotype). The other risk markers were stress, low amplitude of the P300 evoked potential, poor visuospatial functioning, novelty seeking (NS), and harm avoidance (HA). Stress was correlated with BDI scores in all groups. In contrast, low P300 was associated with BDI scores only in boys with the A1+ allele (P = .04), NS was associated with BDI scores only in girls with the A1+ allele (P = .02), and HA was associated with BDI scores only in boys with the A1- allele (P = .01). In addition, boys with the A1+ allele had lower BDI (P = .05) and HA (P = .005) scores than the respective scores for boys with the A1- allele. Girls with the A1- allele had lower HA scores compared with scores for boys with the A1- allele (P = .02). Girls with the A1+ allele had lower visuospatial functioning than that of boys with the A1+ allele (P<.001). Results indicate that both sex and DRD2 genotype modify associations between negative affect and other substance abuse risk markers.

P300 (Latency) Event-Related Potential: An Accurate Predictor of Memory Impairment

To determine if P300 latency changes precede and correlate with memory and mental status, patients (N=1506 aged 20–100 years) who received medical and psychiatric diagnoses (from 1997 to 2002), were assessed for P300 (N=1496), WMS-III (N=694), and MMSE (N=456). Patient and control groups included, a) normal WMS-III on all 4 subscales (N=36), b) normal WMS-III and MMSE (N=189) with subjective memory/mental status complaints, and c) medical patients with normal WMS-III and no memory complaints (N=205), and d) P300 control group without medical, psychiatric or memory problems for ROC.

Patients with impaired/borderline memory had a prolonged P300 latency (P<0.02) compared to age matched non-impaired controls; in patients with normal WMS-III/MMSE, with subjective mild memory/mental status impairment, P300 latency was prolonged compared to controls (P=0.0004). The P300 latency increased by 0.72ms per year (P=7.9×10−65) and voltage decreased by 0.03dV per year (P=6.7×10−10), and both parameters were linearly correlated with the age of the subjects.

Male subjects had an average voltage of 6.1dV and female 6.8dV(P=0.00009). Statistically, prolonged latency began at age range 41–50 (P=0.0002); reduced P300 voltage began at age range 51–60 (P=0.003). WMS-III memory decline for all measures began in females at age range 61–70 (P value at least=0.02) and for males at age range 61–80 (P=0.02). Prolonged P300 latency (P≤0.0001) and memory impairment (at least <0.02) were greater for females than males. MMSE memory decline, male and female, began at age range 81–90 (P value of at least 0.00007).

In our logistic regression model P300 latency was more predictive of WMS-III impairment than MMSE >24. In patients whose WMS-III score is impaired ≤69, or borderline ≤79 (P at least =0.004), a P300 latency more prolonged than the norm (≥300 + 30 + Age) identifies these patients, whereas a MMSE >24 failed. With the ROC curve, we confirmed that P300 latency could accurately identify borderline/impaired memory.

Event-related potentials and neuropsychological tests in obsessive-compulsive disorder

OBJECTIVE

Previous studies have provided evidence from event-related potentials (ERPs) and neuropsychological testing of abnormal cognitive processing in obsessive-compulsive disorder (OCD). The aim of this study was to further characterize the cognitive functions of the patients with OCD by utilizing ERPs and neuropsychological tests.

METHODS

ERPs were recorded in a group of 31 drug-free OCD patients without depression and 30 normal controls following verbal auditory stimuli using an oddball paradigm. The specific neuropsychological tests administered to assess cognitive functions in all participants were the Stroop Test, Trail Making Test, Design Fluency Test, Controlled Word Association Test (Verbal Fluency test).

RESULTS

The patient group showed shorter P300 duration compared to normal controls. In neuropsychological tests, no significant differences were found between the two groups. Negative correlations between Stroop duration and P300 amplitudes in occipital, parietal, and temporal anterior regions were observed.

CONCLUSION

Shorter P300 duration may indicate an acceleration in the P300 process, and speeding of cognitive processing, dysfunction of cortico-subcortical circuits, or some combination of all of the above.

Auditory event-related potentials in 50 melancholic patients: increased N100, N200 and P300 latencies and diminished P300 amplitude

BACKGROUND

To investigate whether there are some differences in Event-Related Potentials (ERP) between melancholic patients and healthy controls. To establish whether there is a relationship between abnormalities of ERP and severity of depression and psychomotor retardation.

METHOD

Melancholic depressed patients (N=50) and normal comparison subjects (N=31) were assessed for latencies and interlatencies of N100, N200, N400, latency and amplitude of P300. The ERPs were studied with an 'oddball paradigm' in the auditory modality. Severity of depression was measured by the Hamilton Depression Rating Scale (HDRS) and psychomotor retardation with the Depressive Retardation Rating Scale (DRRS).

RESULTS

The melancholic group showed a significantly higher latency in N100 (P<0.001), N200 (P<0.001) and P300 (P<0.001) and a significantly lower P300 amplitude (P<0.001) than healthy controls. No other differences were found either in the latencies of the N400 or in their interlatencies. HDRS and DRRS do not have any significant correlations with amplitude or latency measures.

LIMITATIONS

The subjects of this study are inpatients, with a severe subcategory of depression and high average age. It is difficult to generalize these findings.

CONCLUSIONS

The principal finding of this study is the increase in three of the four latencies measured (N100, N200 and P300) and in the decreased P300 amplitude in melancholic patients compared to normal controls. There is no association between these abnormalities and clinical variables.

P300 subcomponents in obsessive-compulsive disorder

Hyperactivity in the frontal cortex, leading to acceleration of attentional and cognitive processes, is discussed as pathogenetic factor in obsessive-compulsive disorder (OCD), as supported by findings of neuroimaging studies. This dysfunction in patients with OCD could be reflected by the auditory event-related P300 component, since one subcomponent of the P300, the so-called P3a, is mainly generated in frontal regions. The P300 of 21 patients with OCD free of medication and 21 age- and sex-matched healthy controls was studied, and dipole source analysis was used, allowing the separation of the subcomponents P3a and P3b with high reliability. No difference concerning the P3a between OCD and healthy subjects was found. OCD patients, however, showed a larger P3b amplitude and a shorter P3b latency (only right hemisphere) as well as a shorter reaction time to target tones as the healthy controls. Since the P3b, generated mainly in the temporo-parietal junction, is related to attentional and higher cognitive functions, whereas the P3a is more related to unspecific orienting reactions, the P3b abnormalities found in these patients could be an electrophysiological correlate of overfocussed attention and faster cognitive processes in OCD, possibly due to higher arousal and noradrenergic function. Regarding the findings with small P300 amplitudes and long latencies in most of the other psychiatric patients, it is remarkable that OCD is one of the few psychiatric diseases being characterized by larger P3b amplitudes and shorter latencies.

Cerebrovascular disease and evolution of depressive symptoms in the cardiovascular health study

BACKGROUND AND PURPOSE

Previous studies have reported an association between cerebrovascular disease and depressive symptoms. The Cardiovascular Health Study (CHS) provides an opportunity to examine the relationship between vascular brain pathology seen on neuroimaging and changes in depressive symptoms.

METHODS

The sample included 3236 CHS participants who had an MRI brain scan. Demographic variables, medical history, functional status, and apolipoprotein E genotype were obtained at baseline. Annual scores on a modified version of the Centers for Epidemiologic Studies Depression (CES-D) scale were obtained initially and up to 7 years subsequently.

RESULTS

After controlling for important covariates, occurrence of depressive symptoms (defined as modified CES-D score of >7) was associated with small lesions in the basal ganglia, large cortical white-matter lesions, and severe subcortical white-matter grade. Neuroimaging variables did not predict incident depression among those who were nondepressive at the time of MRI. Persistence of depressive symptoms across 2 consecutive time points was associated with small basal ganglia lesions and large cerebral cortical white-matter lesions. Worsening of depression (increase in CES-D score of > or =5) was associated with subcortical white-matter lesions.

CONCLUSIONS

These findings suggest that cerebrovascular disease at baseline is related to depression symptoms over time. Further studies are needed to investigate the differential effects of subcortical white- versus gray-matter lesions on mood.

Executive functions and P300 latency in elderly depressed patients and control subjects

The authors asked whether impaired executive functioning and long P300 latency are related dysfunctions and whether they are associated with geriatric depression. A group of 25 elderly depressed patients without dementia and 20 control subjects were assessed on tasks of fluency, initiation and perseveration, the Stroop task, the Wisconsin Card Sorting Test (WCST) perseverative error score, and P300 latency. The groups' performance differed significantly on these tasks and in P300 latency. Longer latency was associated with poorer performance in both groups on all measures except WCST perseverative errors. Regardless of patients' depression status, increased P300 latency predicts poorer performance on executive function tasks requiring speeded performance.

Changes in EEG spectral power in the prefrontal cortex of conscious rats elicited by drugs interacting with dopaminergic and noradrenergic transmission

1. The electroencephalographic (EEG) effects of drugs interacting with dopaminergic and noradrenergic systems were studied in conscious rats. Power spectra (0 - 30 Hz) were recorded from electrodes implanted bilaterally in the prefrontal cortex. Drug effects on EEG power were calculated as the spectral power following drug administration divided by the spectral power after vehicle administration. 2. Dopaminergic agonists at low doses, (apomorphine 0. 01 mg kg-1 s.c., quinpirole 0.01 mg kg-1 i.p.) and dopaminergic antagonists (haloperidol 1 mg kg-1 i.p., raclopride 2.5 mg kg-1 s.c. ), which decrease dopaminergic transmission, induced an increase of EEG power. Conversely, dopaminergic agonists at higher doses (apomorphine 0.5 mg kg-1 s.c., quinpirole 0.5 mg kg-1 i.p.) which increase activation of postsynaptic D2 and D3 receptors, induced a decrease of EEG power. 3. The alpha1-adrenoceptor antagonists (phenoxybenzamine 0.64 mg kg-1 s.c., prazosin 0.32 mg kg-1 s.c.) and the alpha2-adrenoceptor agonists (UK 14304 0.05 mg kg-1 s.c., clonidine 0.025 mg kg-1 i.p.), which decrease noradrenergic transmission, induced an increase of EEG power. Conversely, the alpha1-adrenoceptor agonist, cirazoline (0.05 mg kg-1 s.c.), the adrenergic agent modafinil (250, 350 mg kg-1 i.p.) and alpha2-adrenoceptor antagonists (RX 821002 0.01 mg kg-1 s.c., yohimbine 0.5 mg kg-1 i.p.), which increase noradrenergic transmission, induced a decrease of EEG power. The effects of prazosin (0.64 mg kg-1 s.c.) were dose-dependently antagonized by co-administration with modafinil and cirazoline, but not by apomorphine. 4. In conclusion, pharmacological modulation of dopaminergic and noradrenergic transmission may result in consistent EEG changes: decreased dopaminergic or noradrenergic activity induces an increase of EEG spectral power; while increased dopaminergic or noradrenergic activity decreases EEG spectral power.