Level of haloperidol in plasma is related to electroencephalographic findings in patients who improve.

This study analyzed interrelationships among plasma level of haloperidol (HAL), electroencephalographic (EEG) changes, and clinical response in 37 acutely exacerbated schizophrenic patients after a 6-week period of treatment. Two hypotheses were tested: (1) EEG theta response to HAL depends on levels of HAL in plasma, and this relationship is expressed in patients showing a clear clinical response (responders). (2) Responders and nonresponders are characterized by a different neuroleptic EEG profile. EEG examinations (resting, waking EEG) were performed at study entry, end point of the placebo period ("baseline"), and weekly during the entire HAL treatment period. EEG response was measured by power spectral changes in four frequency bands (delta, theta, alpha, and beta); clinical response was assessed by the Brief Psychiatric Rating Scale. There was a significant relationship between HAL plasma levels and EEG theta activity for treatment responders, whereas no relationship was detected for the nonresponders. Furthermore, there were EEG changes (in the delta and alpha bands) that depended on clinical response but did not show any relationship, either in responders or nonresponders, to HAL plasma levels. These results supported both hypotheses.     

Age and sex effects in the EEG: development of the normal child.

OBJECTIVES: This study investigated age-related changes and sex differences in the EEGs of normal children. METHODS: Forty boys and 40 girls, between the ages of 8 and 12 years, participated in this study. The EEG was recorded during an eyes-closed resting condition and Fourier transformed to provide estimates for total power, absolute and relative power in the delta, theta, alpha and beta bands, and for theta/alpha and theta/beta ratios. RESULTS: Absolute delta activity decreased with age. Relative delta and theta decreased and alpha and beta increased with increasing age. The theta/alpha and theta/beta ratios decreased with increasing age. All of these indicated a developmental reduction in slow wave activity. Maturational differences were found in the rates of change between the midline and the two hemispheres. In the absolute delta and the theta/beta ratio, the midline and the two hemispheres became more equipotential with age. In the beta band, power increased at a greater rate than in the two hemispheres. Sex differences were found, with males having less theta and more alpha than females. CONCLUSIONS: These results indicated that maturation occurs earlier at the midline than in the two hemispheres. Females were also found to have a developmental lag in the EEG compared with males.     

EEG spectra in severely dyslexic men: rest and word and design recognition

To identify and localize differences in brain functioning, electrical activity was recorded with a full complement of scalp electrodes in 14 healthy, severely dyslexic men (mean age = 22 years, S.D. = 3) and 15 matched controls during rest and during word and design recognition. The electroencephalograms were spectrum analyzed, and the mean amplitude in each of 5 bands--delta, theta, alpha, slow beta and fast beta--compared topographically between conditions and groups. The two tasks did not elicit differentially lateralized patterns of electrical activity, but produced anteroposterior differences in alpha and theta. The Designs task, more difficult for both groups, was associated with less posterior alpha than was the Words task. The strongest group difference was likewise seen along an anteroposterior axis on the Designs task. With performance equal to that of controls, the dyslexics showed relatively greater fronto-central theta and less posterior theta (a more activated state), suggesting that dyslexics were compensating for less efficient information processing. There were no group differences in overall amplitude in any band for any condition. The differences in the topographic distribution of theta may reflect subtle differences in brain organization or compensatory recruitment of widely distributed neuronal networks.     

EEG topography during sleep inertia upon awakening after a period of increased homeostatic sleep pressure

ObjectiveBehavioral and physiological indexes of high sleep inertia (SI) characterize the awakening from recovery (REC) sleep after prolonged wakefulness, but the associated electroencephalogram (EEG) topography has never been investigated. Here, we compare the EEG topography following the awakening from baseline (BSL) and REC sleep.MethodsWe have recorded the EEG waking activity of 26 healthy subjects immediately after the awakening from BSL sleep and from REC sleep following 40 h of prolonged wakefulness. In both BSL and REC conditions, 12 subjects were awakened from stage 2 sleep, and 14 subjects from rapid eye movement (REM) sleep. The full-scalp waking EEG (eyes closed) was recorded after all awakenings.ResultsSubjects awakened from REC sleep showed a reduction of fronto-central alpha and beta-1 activities, while no significant effects of the sleep stage of awakening have been observed. Positive correlations between pre- and post-awakening EEG modifications following REC sleep have been found in the posterior and lateral cortices in the frequency ranges from theta to beta-2 and (only for REM awakenings) extending to the fronto-central regions in the beta-1 band, and in the midline central and parietal derivations for the alpha and delta bands, respectively.ConclusionsThese findings suggest that the higher SI after REC sleep may be due to the fronto-central decrease of alpha and beta-1 activity and to the persistence of the sleep EEG features after awakening in the posterior, lateral, and fronto-central cortices, without influences of the sleep stage of awakening.     

Intracranial current density (LORETA) differences in QEEG frequency bands between depressed and non-depressed alcoholic patients.

OBJECTIVE: To assess possible differences in intracranial source distribution of surface QEEG power between depressed and non-depressed alcoholic patients in order to find any symptom-related topographic features of physiopathologic relevance. METHODS: Low-Resolution Electromagnetic Tomography (LORETA) for the delta, theta, alpha and beta bands of EEG spectra was estimated from 38 alcoholic patients, 20 with and 18 without clinical depression, in which QEEG showed decreased slow and increased beta activity diffusely. Statistical non-parametric mapping was used to compare depressed and non-depressed groups. Measures of intracranial current density in individual patients at areas of significant differences were correlated with BDI scores. RESULTS: Patients with clinical depression showed areas of significantly lower current density than non-depressed patients in delta band at left anterior temporal, left midtemporal (including amygdala and hippocampus), and both frontopolar cortices mostly on the right; and in theta band at bilateral parietal lobe, anterior cingulate and medial frontal cortex. No differences were found at alpha and beta band. Intracranial current density in delta band at left parahippocampal, left midfrontal cortex and right frontopolar cortex was negatively correlated with BDI score. Theta band also showed negative correlations with BDI at sites of significant differences. CONCLUSIONS: Diffusely decreased delta and theta activity in the surface QEEG of alcoholic patients has a different intracranial distribution linked to the presence or not of clinical depression that seems to reveal a dysfunctional neuronal state at several specific limbic and other cortical locations that have been related to a specific clinical disorder such as depression. SIGNIFICANCE: These results provided further evidence on the effects of depression in the context of alcohol dependence, in this case decreased slow activity as a possible marker of neuronal damage secondary to alcohol toxicity, clinically expressed as depressive symptoms when present in structures that are known to be related to clinical depression.     

Clozapine-induced QEEG changes correlate with clinical response in schizophrenic patients: a prospective, longitudinal study

BACKGROUND: The changes of theta activity (3.5-7 Hz) in the quantitative electroencephalography (QEEG) and serum clozapine levels and their correlation with clinical response, measured by the Positive and Negative Syndrome Rating Scale (PANSS) for schizophrenia, were examined prospectively in 16 patients suffering from schizophrenia during 18 weeks of clozapine (CLO) treatment. METHODS: Evaluations were performed on five occasions: before the initiation of CLO treatment at baseline and after 1, 3, 10, and 18 weeks of treatment. Doses of CLO starting from 50 mg/day were determined on the basis of clinical response. In the PANSS subscales for positive and negative symptoms, a significant (P < 0.05) improvement was observed after the first week, and in the subscale for general symptoms, improvement was seen after three weeks of treatment with CLO. A significant increase in theta power (P < 0.01) was found after three weeks of CLO treatment in the electrodes over the fronto-central scalp area, most distinctly in the midline. RESULTS: After three weeks we observed significant inverse correlations between the theta power increase and the changes in PANSS subscales for negative (P < 0.01) and positive (P < 0.05) symptoms, and after 10 weeks, between the theta power increase and the change in PANSS subscales for general (P < 0.05) and positive (P < 0.05) symptoms. After 18 weeks a trend of inverse correlation between the PANSS subscales for general and negative symptoms and the right and midline theta power increase was observed, but not with regard to positive symptoms. There were trends, but no significant correlations, between CLO treatment response and serum CLO levels. CONCLUSIONS: These findings indicate that the change in the theta frequency in QEEG and particularly in the midline electrodes over the fronto-central scalp area might be a more sensitive indicator for the evaluation of CLO treatment adequacy than the serum CLO level.     

θ, β But not α-band EEG connectivity has implications for dual task performance in Parkinson’s disease

People with Parkinson’s disease (PD) have difficulty performing dual tasks or simultaneous movements, even if the same movements can be easily performed individually. This has particular significance clinically, as for example falling injuries may occur if care is not taken to perform tasks one at a time. We investigated whether this difficultyx results from impaired dopamine-modulated connectivity. We recorded the EEG in PD subjects off and on l-dopa medication performing simultaneous and unimanual tracking tasks. To deal with the inherent non-stationarity of the EEG during motor tasks, we segmented the data into task-related sections based on transient synchronisation between independent components of the data, before assessing the mutual information (MI) between each EEG channel pair. In both tasks, PD subjects off-medication demonstrated enhanced fronto-central and decreased occipital synchronisation within theta and alpha bands, and widespread increased beta-band synchronisation, compared to controls. Synchronisation changes in theta and beta bands were partially normalised by l-dopa, but l-dopa had relatively little effect on alpha band synchronisation. When comparing simultaneous movements to unimanual tracking, PD subjects off-medication demonstrated synchronisation changes within theta and beta bands, however alpha connectivity was largely unchanged. These results suggest that downstream influences of impaired basal ganglia function on cortico-cortical connectivity may result in difficulties with dual task performance in PD.     

Cortical source analysis of resting state EEG data in children with attention deficit hyperactivity disorder

ObjectiveThis study investigated age-dependent and subtype-related alterations in electroencephalography (EEG) power spectra and current source densities (CSD) in children with attention deficit and hyperactivity disorder (ADHD).MethodsWe performed spectral and cortical source (exact low-resolution electromagnetic tomography, eLORETA) analyses using resting state EEG recordings from 40 children (8–16 years) with combined and inattentive subtypes of ADHD and 41 age-matched healthy controls (HC). Group differences in EEG spectra and CSD were investigated at each scalp location, voxel and cortical region in delta, theta, alpha and beta bands. We also explored associations between topographic changes in EEG power and CSD and age.ResultsCompared to healthy controls, combined ADHD subtype was characterized with significantly increased diffuse theta/beta power ratios (TBR) with a widespread decrease in beta CSD. Inattentive ADHD subtype presented increased TBR in all brain regions except in posterior areas with a global increase in theta source power. In both ADHD and HC, older age groups showed significantly lower delta source power and TBR and higher alpha and beta source power than younger age groups. Compared to HC, ADHD was characterized with increases in theta fronto-central and temporal source power with increasing age.ConclusionsOur results confirm that TBR can be used as a neurophysiological biomarker to differentiate ADHD from healthy children at both the source and sensor levels.SignificanceOur findings emphasize the importance of performing the source imaging analysis in order to better characterize age-related changes in resting-state EEG activity in ADHD and controls.     

Spatiotemporal changes of EEG activity during waking-sleeping transition period

To evaluate the spatiotemporal changes of EEG during waking-sleeping transition or hypnagogic period, spectral analysis of the five scalp EEG on the midline (Fpz, Fz, Cz, Pz and Oz) referenced to the left ear lobe was carried out on seven young male subjects. Power spectra from consecutive samples of 5.12 sec period with 0.2 Hz resolution were studied from 10 min before the manually scored stage 1 onset to 30 min after the onset of stage 1. The average power spectra over 1 min segments and corresponding coefficient of variation (CV) were determined for the frequency bands of delta (1-3 Hz), theta (4-7 Hz), alpha (8-12 Hz), sigma (13-15 Hz) and beta (16-19 Hz). The latency score was defined as the time elapsed from the onset of stage 1 to the first epoch when the frequency band power, using the ANOVA significantly increased (or decreased) in comparison with the average level at the onset of stage 1. Median latency scores for each band were similar to the Cz scores, with a ranking, from early to late, of: alpha (2 min), theta (3 min), delta (5 min) and sigma (5 min). Significant change was not observed on the beta band activity. In terms of the EEG areas, the shortest latency was found in the theta band activity of the Fz EEG (2 min), and the longest was the sigma band activity of the Fpz and Oz EEG (8 min). The average stage 2 latency was 3.5 min when it was measured as time elapsed between the onset of stage 1 and 2. The average curves of delta, theta and alpha band CVs, started to increase just before or immediately after stage 1 onset and continued to increase for about 10 min. If the increased CV or unsteadiness of EEG activity is taken as a characteristic of the hypnagogic period, hypnagogic states may be considered to have continued until about 10 min after the stage 1 onset. Delta-theta activity showed a rapid rise in power after the onset of stage 1 for all areas. Delta power at the occipital, however, increased more gradually, and consistently remained at a lower level. The differences of delta power between Oz and other four electrode sites became clear at 7 min after the onset of stage 1. These regional differences may reflect the termination of hypnagogic effects.(ABSTRACT TRUNCATED AT 400 WORDS)     

Quantitative EEG effects of topiramate.

OBJECTIVE: The study is to invesigate the effect of topiramate (TPM) on EEG by means of quantitative pharmacoelectroencephalography (QPEEG). METHODS: One dose of TPM was administrated to epileptics and healthy adults. The EEG samples were obtained prior to and at regular intervals within the 24 hours following the administration of TPM. The EEG activity was processed with power spectral analysis. RESULTS: The power of slow wave, alpha 1 bands and total power increased after the administration of TPM, the power or slow wave in both occipital areas, and the total power of all scalp areas also increased. The percent of power increased at the theta band and alpha 1 band (healthy adults) or delta band, theta band (patients). CONCLUSION: TPM can change the EEG background activity. These changes are different from other antiepileptic drugs.     

Reduced fronto-cortical brain connectivity during NREM sleep in Asperger syndrome: An EEG spectral and phase coherence study

Objective

To investigate whether sleep macrostructure and EEG power spectral density and coherence during NREM sleep are different in Asperger syndrome (AS) compared to typically developing children and adolescents.

Methods

Standard all night EEG sleep parameters were obtained from 18 un-medicated subjects with AS and 14 controls (age range: 7.5–21.5 years) after one adaptation night. Spectral, and phase coherence measures were computed for multiple frequency bands during NREM sleep.

Results

Sleep latency and wake after sleep onset were increased in AS. Absolute power spectrum density (PSD) was significantly reduced in AS in the alpha, sigma, beta and gamma bands and in all 10 EEG derivations. Relative PSD showed a significant increase in delta and a decrease in the sigma band for frontal, and in beta for centro-temporal derivations. Intrahemispheric coherence measures were markedly lower in AS in the frontal areas, and the right hemisphere over all EEG channels. The most prominent reduction in intrahemispheric coherence was observed over the fronto-central areas in delta, theta, alpha and sigma EEG frequency bands.

Conclusion

EEG power spectra and coherence during NREM sleep, in particular in fronto-cortical derivations are different in AS compared to typically developing children and adolescents.

Significance

Quantitative analysis of the EEG during NREM sleep supports the hypothesis of frontal dysfunction in AS.     

Decrease in early right alpha band phase synchronization and late gamma band oscillations in processing syntax in music

The present study investigated the neural correlates associated with the processing of music-syntactical irregularities as compared with regular syntactic structures in music. Previous studies reported an early ( approximately 200 ms) right anterior negative component (ERAN) by traditional event-related-potential analysis during music-syntactical irregularities, yet little is known about the underlying oscillatory and synchronization properties of brain responses which are supposed to play a crucial role in general cognition including music perception. First we showed that the ERAN was primarily represented by low frequency (<8 Hz) brain oscillations. Further, we found that music-syntactical irregularities as compared with music-syntactical regularities, were associated with (i) an early decrease in the alpha band (9-10 Hz) phase synchronization between right fronto-central and left temporal brain regions, and (ii) a late ( approximately 500 ms) decrease in gamma band (38-50 Hz) oscillations over fronto-central brain regions. These results indicate a weaker degree of long-range integration when the musical expectancy is violated. In summary, our results reveal neural mechanisms of music-syntactic processing that operate at different levels of cortical integration, ranging from early decrease in long-range alpha phase synchronization to late local gamma oscillations.     

Neurophysiological and behavioral indices of time pressure effects on visuomotor task performance

Using a video game format, this study examined the effects of time pressure (TP) on behavioral and electrocortical indices. The behavioral results were consistent with previous time pressure research in that TP reduced time to perform a task and increases behavioral errors. In addition, electroencephalogram (EEG) measures showed distinctive patterns associated with TP in the theta, mu, and gamma bands along the midline. Site specific changes in the success vs. failure trials were also seen in midline theta at Fz, gamma at Fz, and mu at Cz. Right parietal alpha also differentiated TP and success vs. failure trials. In specific TP (1) increased frontal midline theta activity and (2) increased gamma at midline (frontal, central, and partietal) and in right frontal areas. The results of these findings are discussed in terms of the formation of specific neurocognitive strategies as evidenced by the topographic distribution of task-related modulation of the EEG within certain frequency bands. It is suggested that the effect of TP on visuomotor performance is mediated by adopting either task-relevant or task-irrelevant neurocognitive strategies as evidenced by successful or failed trials, respectively. Whether these strategies are formulated prior to performance or appear spontaneously during task performance remains unclear and is awaiting further experimentation.     

Computerized electroencephalographic assessment of congenital brain infarction

We studied 12 children (8 female and 4 male) aged 2.2–14.3 years, whose computed tomographic (CT) examination had shown evidence of malacic and/or porencephalic outcomes of early vascular brain infarction. Topographic spectral electroencephalographic (EEG) analysis was performed in all patients in the awake state. The following spectral EEG variables were studied: topography, absolute and relative power of delta, theta, alpha, beta bands, overall power, and peak alpha frequency asymmetries. The results of topographic spectral EEG analysis were compared with the localization and nature of lesions as detected by CT scans. Depending on the nature of the lesions, we were able to identify two different spectral patterns. Porencephalic cysts were characterized by an increase in delta and theta bands in the areas surrounding the lesion sites, as identified by CT. Spectral EEG patterns of malacic outcomes resulted in a focal increase in theta and delta band power, corresponding to the topography of lesions. Moreover, in 9/12 subjects an asymmetry of alpha rhythm in occipital leads was found homolaterally to the lesion sites, associated with a decrease in power, without any CT evidence of an occipital lesion.     

The rhythm of the executive gate of speech: subthalamic low‐frequency oscillations increase during verbal generation

We investigated neurophysiological mechanisms of subthalamic nucleus involvement in verbal fluency through a verbal generation task. The subthalamic nucleus is thought to act as a behavioural go/no‐go instance by means of oscillatory communication in the theta band with the prefrontal cortex. Because subthalamic alpha‐theta frequency stimulation has been shown to exert beneficial effects on verbal fluency in Parkinson′s disease, we hypothesized that an alpha‐theta oscillatory network involving the subthalamic nucleus underlies verbal generation task performance as a gating instance for speech execution. Postoperative subthalamic local field potential recordings were performed during a verbal generation compared to a control task. Time‐frequency analysis revealed a significant alpha‐theta power increase and enhanced alpha‐theta coherence between the subthalamic nucleus and the frontal surface EEG during the verbal generation task. Beta and gamma oscillations were not significantly modulated by the task. Power increase significantly correlated with verbal generation performance. Our results provide experimental evidence for local alpha‐theta oscillatory activity in the subthalamic nucleus and coherence to frontal associative areas as a neurophysiological mechanism underlying a verbal generation task. Thus, verbal fluency improvement during subthalamic alpha‐theta stimulation in Parkinson′s disease is likely due to an enhancement of alpha‐theta oscillatory network activity. Alpha‐theta oscillations can be interpreted as the rhythmic gating signature in a speech executing subthalamic‐prefrontal network.     

Do prefrontal midline electrodes provide unique neurophysiologic information in Major Depressive Disorder?

Brain oscillatory activity from the midline prefrontal region has been shown to reflect brain dysfunction in subjects with Major Depressive Disorder (MDD). It is not known, however, whether electrodes from this area provide unique information about brain function in MDD. We examined a set of midline sites and two other prefrontal locations for detecting cerebral activity differences between subjects with MDD and healthy controls. Resting awake quantitative EEG (qEEG) data were recorded from 168 subjects: 47 never-depressed adults and 121 with a current major depressive episode. Individual midline electrodes (Fpz, Fz, Cz, Pz, and Oz) and prefrontal electrodes outside the hairline (Fp1, Fp2) were examined with absolute and relative power and cordance in the theta band. We found that MDD subjects exhibited higher values of cordance (p = 0.0066) at Fpz than controls; no significant differences were found at other locations, and power measures showed trend-level differences. Depressed adults showed higher midline cordance than did never-depressed subjects at the most-anterior midline channel. Salient abnormalities in MDD may be detectable by focusing on the prefrontal midline region, and EEG metrics from focused electrode arrays may offer clinical practicality for clinical monitoring.     

Propofol anesthesia induces phase synchronization changes in EEG.

OBJECTIVE: Phase coupling between EEG channel pairs in various frequency bands was evaluated during propofol anesthetic induction and recovery periods. METHODS: Twenty-three patients participated in the study. Phase synchronization indices based on the Hilbert transform were investigated on frequency bands 0.05-1 Hz, 1-4 Hz, 4-8 Hz, 8-12 Hz and 12-16 Hz for all pairs of the 9 EEG channels covering midline and frontal areas. A straight line was used to approximate the index values as a function of time and the Sign Test statistics were applied to the slope parameters. RESULTS: Systematic phase synchronization changes were detected. Generally, phase synchronization in the sub-delta band decreased during the induction and increased during the recovery, while the directions were reversed in the alpha band. The changes were dependent on the channel pair. In the delta, theta and beta bands, the changes were aligned more irregularly than in the sub-delta or in the alpha bands. Highly asymmetric behavior between the induction and the recovery periods was also observed in these bands. CONCLUSIONS: Induction and recovery from propofol anesthesia changes the phase synchronization between the EEG channels. The passband and location-specific behavior of these changes reveals the effects of the anesthetic to the different neural mechanisms.     

Event-related theta oscillations during working memory tasks in patients with schizophrenia and healthy controls

Altered frontal lobe activity and executive control associated with working memory (WM) dysfunction are recognized as core deficits in schizophrenia. These impairments have been discussed as being associated with deficits in self-regulated action monitoring and anticipatory action plan generation. To study electrophysiological correlates of executive control -- specifically action monitoring and action rule switching -- under varying WM load, we used a paradigm derived from classic N-back (WM) tasks and requiring monitoring of simple actions. We focused on event-related changes in post-stimulus theta oscillatory activity during varying cognitive and WM demand in healthy controls and schizophrenia patients. The results show significant WM load and rule-switching-related increases of post-stimulus theta amplitude at fronto-central locations in controls. In patients with schizophrenia, there was no such modulation, but -- apart from an increased early theta at left temporal locations -- generally reduced late theta responses in all tasks and at all locations. Furthermore, the patients with schizophrenia showed significant differences in their error patterns, which imply differences in automation and anticipation of actions between controls and patients. These findings suggest that theta oscillations are involved in mediating frontal lobe activity and functions related to enhanced executive control. We conclude that the patients with schizophrenia showed deficits in acquiring a mental task set which appear to be associated with impairments in action monitoring and task-specific regulation of executive control.     

A qualitative and quantitative analysis of rhythmic activities during a mental task and sleep spindles

The frequency, configuration, and distribution of sleep spindles are similar to some of the rhythmic activities seen during task performance. In the present study, the relationship between rhythmic activities during sleep and arithmetic addition was investigated in male university students with (n = 10) and without (n = 10) frontal midline theta activity (Fmtheta). Electroencephalograms (EEGs) during addition in both groups were compared at frontal and central areas on three consecutive days. Polysomnograms were recorded at the same regions on four consecutive nights for each group. The amount of theta rhythm during a mental task (Fmtheta) and in nocturnal sleep at Fz and Cz electrodes was greater for the Fmtheta group than for the non-Fmtheta group, while the amount of beta rhythm at both sites was smaller in the Fmtheta group than in the non-Fmtheta group. There were no differences between the groups in the amount of alpha rhythm at either site. The frequency of alpha rhythm at Fz and Cz in both situations was slower for the Fmtheta group than for the non-Fmtheta group, but there were no differences in the frequency of theta and beta rhythms between the groups at either site. These results suggest that rhythmic activities during a mental task and in sleep may correlate with each other.     

Determinants of quantitative spectral electroencephalography in early Alzheimer's disease: cognitive function, regional cerebral blood flow, and computed tomography

Electroencephalography (EEG) bands may have different clinical or physiological correlates at initial diagnosis of Alzheimer's disease (AD). We studied 163 consecutive patients with probable (n = 105) and possible (n = 58) AD with measurements of cognitive function (CAMCOG), regional cerebral blood flow (rCBF) with single photon emission computed tomography using technetium-99m-labeled hexamethylpropylene amine oxime, and computed tomography (CT). Lower CAMCOG scores were significantly and most strongly associated with lower parieto-occipital and fronto-central alpha power. In a separate analysis of cognitive domains, disturbances in language, praxis, attention, and abstraction were also significantly and most consistently related to decrease in alpha power. Presence of cortical atrophy as measured on CT showed some statistically significant relations with EEG bands, but these associations were not consistent. Lower temporal and parietal rCBF were significantly related to lower parieto-occipital alpha activity. Presence of leukoaraiosis was significantly associated with lower beta values, but also with higher absolute theta and delta activity. The results suggest that alpha on EEG is most closely linked to cognitive function and rCBF, while beta and theta activity more likely reflect lower cortical or subcortical changes. Our study thus provides evidence that the EEG bands reflect differential pathophysiologic changes in AD.