Findings of electroencephalographic brain mapping in mild to moderate dementia of the Alzheimer type during resting, motor, and music-perception conditions

Sex differences in the progression to Alzheimer's disease: a combination of functional and structural markers

Mild cognitive impairment (MCI) has been frequently interpreted as a transitional phase between healthy cognitive aging and dementia, particularly of the Alzheimer's disease (AD) type. Of note, few studies explored that transition from a multifactorial perspective, taking into consideration the effect of basic factors such as biological sex. In the present study 96 subjects with MCI (37 males and 59 females) were followed-up and divided into two subgroups according to their clinical outcome: "progressive" MCI (pMCI = 41), if they fulfilled the diagnostic criteria for AD at the end of follow-up; and "stable" MCI (sMCI = 55), if they remained with the initial diagnosis. Different markers were combined to characterize sex differences between groups, including magnetoencephalography recordings, cognitive performance, and brain volumes derived from magnetic resonance imaging. Results indicated that the pMCI group exhibited higher low-frequency activity, lower scores in neuropsychological tests and reduced brain volumes than the sMCI group, being these measures significantly correlated. When sex was considered, results revealed that this pattern was mainly due to the influence of the females' sample. Overall, females exhibited lower cognitive scores and reduced brain volumes. More interestingly, females in the pMCI group showed an increased theta activity that correlated with a more abrupt reduction of cognitive and volumetric scores as compared with females in the sMCI group and with males in the pMCI group. These findings suggest that females' brains might be more vulnerable to the effects of AD pathology, since regardless of age, they showed signs of more pronounced deterioration than males.

Resting State Alpha Electroencephalographic Rhythms Are Affected by Sex in Cognitively Unimpaired Seniors and Patients with Alzheimer's Disease and Amnesic Mild Cognitive Impairment: A Retrospective and Exploratory Study

In the present retrospective and exploratory study, we tested the hypothesis that sex may affect cortical sources of resting state eyes-closed electroencephalographic (rsEEG) rhythms recorded in normal elderly (Nold) seniors and patients with Alzheimer's disease and mild cognitive impairment (ADMCI). Datasets in 69 ADMCI and 57 Nold individuals were taken from an international archive. The rsEEG rhythms were investigated at individual delta, theta, and alpha frequency bands and fixed beta (14-30 Hz) and gamma (30-40 Hz) bands. Each group was stratified into matched females and males. The sex factor affected the magnitude of rsEEG source activities in the Nold seniors. Compared with the males, the females were characterized by greater alpha source activities in all cortical regions. Similarly, the parietal, temporal, and occipital alpha source activities were greater in the ADMCI-females than the males. Notably, the present sex effects did not depend on core genetic (APOE4), neuropathological (Aβ42/phospho-tau ratio in the cerebrospinal fluid), structural neurodegenerative and cerebrovascular (MRI) variables characterizing sporadic AD-related processes in ADMCI seniors. These results suggest the sex factor may significantly affect neurophysiological brain neural oscillatory synchronization mechanisms underpinning the generation of dominant rsEEG alpha rhythms to regulate cortical arousal during quiet vigilance.

Distinguishing rhythmic from non-rhythmic brain activity during rest in healthy neurocognitive aging

Rhythmic brain activity at low frequencies (<12Hz) during rest are thought to increase in neurodegenerative disease, but findings in healthy neurocognitive aging are mixed. Here we address two reasons conventional spectral analyses may have led to inconsistent results. First, spectral-power measures are compared to a baseline condition; when resting activity is the signal of interest, it is unclear what the baseline should be. Second, conventional methods do not clearly differentiate power due to rhythmic versus non-rhythmic activity. The Better OSCillation detection method (BOSC; Caplan et al., 2001; Whitten et al., 2011) avoids these problems by using the signal's own spectral characteristics as a reference to detect elevations in power lasting a few cycles. We recorded electroencephalographic (EEG) signal during rest, alternating eyes open and closed, in healthy younger (18-25 years) and older (60-74 years) participants. Topographic plots suggested the conventional and BOSC analyses measured different sources of activity, particularly at frequencies, like delta (1-4Hz), at which rhythms are sporadic; topographies were more similar in the 8-12Hz alpha band. There was little theta-band activity meeting the BOSC method's criteria, suggesting prior findings of theta power in healthy aging may reflect non-rhythmic signal. In contrast, delta oscillations were present at higher levels than theta in both age groups. In summary, applying strict and standardized criteria for rhythmicity, slow rhythms appear present in the resting brain at delta and alpha, but not theta frequencies, and appear unchanged in healthy aging.

Individual brain-frequency responses to self-selected music

Music is a stimulus which may give rise to a wide range of emotional and cognitive responses. Therefore, brain reactivity to music has become a focus of interest in cognitive neuroscience. It is possible that individual preference moderates the effectof music on the brain. In the present study we examined whether there are common effects of listening to music even if each subject in a sample chooses their own piece of music. We invited 18 subjects to bring along their favorite relaxing music, and their favourite stimulating music. Additionally, a condition with tactile stimulation on the foot and a baseline condition (rest) without stimulation were used. The tactile stimulation was chosen to provide a simple, non-auditory condition which would be identical for all subjects. The electroencephalogram was recorded for each of the 3 conditions and during rest. We found responses in the alpha range mainly on parietal and occipital sites that were significant compared to baseline in 13 subjects during relaxing music, 15 subjects during activating music, and 16 subjects during tactile stimulation. Most subjects showed an alpha desynchronization in a lower alpha range followed by a synchronization in an upper frequency range. However, some subjects showed an increase in this area, whereas others showed a decrease only. In addition, many subjects showed reactivity in the beta range. Beta activity was especially increased while listening to activating music and during tactile stimulation in most subjects. We found interindividual differences in the response patterns even though the stimuli provoked comparable subjective emotions (relaxation, activation), and even if the stimulus was the same for all subjects (somatosensory stimulation). We suggest that brain responsivity to music should be examined individually by considering individual characteristics.

The early diagnosis and differential diagnosis of Alzheimer’s disease with clinical methods

Az Alzheimer-dementia progresszív neurodegeneratív betegség, amelynek progresszióját a jelenleg alkalmazott kezelések a betegség korai szakaszában lassíthatják. Vizsgálatainkkal olyan biológiai markereket kerestünk, amelyek érzékenyek a betegség prodromalis és korai szakaszában. A diagnosztikai rutinvizsgálatok mellett neuropszichológiai tesztet, auditoros kiváltottválasz-vizsgálatot és speciális laboratóriumi teszteket végeztünk Alzheimer-betegségben, vascularis dementiában, enyhe kognitív zavarban és depresszióban egészséges kontrollhoz hasonlítva. A párosított asszociációs tanulás mindegyik betegcsoportban kóros volt, depresszióban reverzíbilisnek látszott. Az auditoros kiváltott P300 komponens latenciája enyhe kognitív zavarban és dementiában megnőtt. A szérumban a paraoxonázaktivitás csökkent, az agy-gerincvelői folyadékban az Nε(γ-glutamil)lizin-izodipeptid koncentrációja emelkedett mindkét dementiacsoportban. Enyhe kognitív zavarban a párosított asszociációs tanulási teszt és a P300 jellegzetes változása az Alzheimer-dementia kialakulásának nagyobb kockázatát jelzi. A paraoxonázaktivitás és az izodipeptidkoncentráció változása érzékeny marker lehet a neurodegeneratív kórfolyamatok kimutatására. Az említett vizsgálatok együttes alkalmazása segítséget nyújthat az Alzheimer-dementia korai felismerésében és előrejelzésében.

Working memory load-related electroencephalographic parameters can differentiate progressive from stable mild cognitive impairment

Recent studies described several changes of endogenous event-related potentials (ERP) and brain rhythm synchronization during memory activation in patients with Alzheimer's disease (AD). To examine whether memory-related EEG parameters may predict cognitive decline in mild cognitive impairment (MCI), we assessed P200 and N200 latencies as well as beta event-related synchronization (ERS) in 16 elderly controls (EC), 29 MCI cases and 10 patients with AD during the successful performance of a pure attentional detection task as compared with a highly working memory demanding two-back task. At 1 year follow-up, 16 MCI patients showed progressive cognitive decline (PMCI) and 13 remained stable (SMCI). Both P200 and N200 latencies in the two-back task were longer in PMCI and AD cases compared with EC and SMCI cases. During the interval 1000 ms to 1700 ms after stimulus, beta ERS at parietal electrodes was of lower amplitude in PMCI and AD compared with EC and SMCI cases. Univariate models showed that P200, N200 and log% beta values were significantly related to the SMCI/PMCI distinction with areas under the receiver operating characteristic curve of 0.93, 0.78 and 0.72, respectively. The combination of all three EEG hallmarks was the stronger predictor of MCI deterioration with 90% of correctly classified MCI cases. Our data reveal that PMCI and clinically overt AD share the same pattern of working memory-related EEG activation characterized by increased P200-N200 latencies and decreased beta ERS. They also show that P200 latency during the two-back task may be a simple and promising EEG marker of rapid cognitive decline in MCI.

Changes of EEG spectra and coherence following performance in a cognitive task in Alzheimer's disease

Electroencephalographic measures combined with cognitive tasks are widely used for the assessment of cognitive and pathophysiological changes in Alzheimer's disease (AD). Instead of the analysis of EEG data obtained during the performance of the task, in this study data recorded in the immediate after-task period were analyzed. It was expected that this period would correspond to the electrophysiological consequences of the cognitive effort. Data of 14 patients with AD (MMS score: 16-24) were compared to that of 10 healthy control subjects. Reverse counting of a fix duration was used as a cognitive task. Changes of relative frequency spectra, and those of inter-and intrahemispheric coherence were analyzed. Relative theta power was significantly higher in AD patients compared to the controls both before and after the task. The performance of the task resulted in an increase of the relative alpha2 band in the AD group, whereas it slightly decreased in the control group. The most prominent coherence differences between AD and controls were found in the alpha1 band, especially for long-range coherence values. Coherence in this frequency band increased in the control group following the task, not seen in the AD group. We conclude that EEG parameters calculated from epochs following the completion of a cognitive task clearly differentiates patients with AD from normal controls. The electrophysiological changes found in AD may correspond to the decrease of functional connectivity of cortical areas and to the malfunctioning of the networks engaged in the cognitive task investigated.

Decreased theta event-related synchronization during working memory activation is associated with progressive mild cognitive impairment

BACKGROUND

Among the different quantitative electroencephalographic markers, theta activity is known to reflect neural resources involved in memory processes and directed attention. Previous studies suggested that synchronization likelihood analysis in theta-band frequency might be a sensitive method to identify early alterations of neuronal networks in mild cognitive impairment (MCI).

METHODS

We report here a longitudinal study of 24 MCI patients with theta event-related synchronization (ERS) analysis during the n-back working memory task and neuropsychological follow-up after 1 year. Statistical analysis included analysis of variance and logistic regression to assess the relationship between cognitive decline and theta ERS.

RESULTS

Upon follow-up, 13 MCI patients showed progressive MCI and 11 remained stable. In both groups, the phasic increase in theta amplitude after stimulus presentation did not depend on working memory load and electrode sites. Progressive MCI cases displayed significantly lower theta ERS power over all electrode sites compared to stable MCI cases. Theta ERS was significantly related to the cognitive outcome explaining 15.5% of its variability. In terms of MCI classification, the best combination of sensitivity and specificity was 0.87 and 0.60, respectively, with an area under the corresponding receiver operating characteristic curve reaching 76%.

CONCLUSIONS

The present data indicate that a decrease in the early phasic theta ERS power during working memory activation may predict cognitive decline in MCI. This phenomenon is not related to working memory load but may reflect the presence of early deficits in directed attention-related neural circuits in MCI.

Theta-power differences in patients with mild cognitive impairment under rest condition and during haptic tasks

The aim of this study was to investigate spectral EEG theta-power during perceptive-cognitive demands in age-homogeneous groups of subjects with mild cognitive impairment (MCI), mild dementia (MDE), and a healthy control (CO) group. The present study includes 51 subjects (23 males, 28 females). We used the scales of the CDR (clinical dementia rating) to assign the subjects to the different groups. EEG data were collected during 10 minutes rest condition with eyes closed and during haptic perception test. The quality of the haptic reproductions differed significantly between CO and MCI, as well as between CO and MDE. The statistical comparison between EEG theta-power under rest condition and theta-power during haptic tasks revealed a significant decrease in theta-power during haptic tasks in all three groups over parieto-occipital regions. During haptic tasks, the theta-power was significantly different between CO and MDE over occipital regions and over parieto-temporal regions. A significant difference between CO and MCI was only revealed over right occipital regions (O2). Spectral theta-power during haptic tasks is a suitable measure to distinguish healthy subjects (CO) from patients with MCI respectively MDE. The results show that haptic tasks are sensitive to early perceptive-cognitive and functional deficits in patients with MCI.

Magnetoencephalographic analysis of cortical activity in Alzheimer's disease: a pilot study

OBJECTIVES

In the present study, MEG was used to analyze spectral power and reference-free coherence in patients with probable Alzheimer's disease (AD).

METHODS

Sixty-one channel MEG was recorded in 5 AD patients and 5 age-matched controls at rest with eyes open and eyes closed, as well as during the performance of two different mental tasks. Artefact-free epochs were selected for the analysis of power and coherence values in each of 5 4-Hz wide frequency bands ranging from 2 to 22 Hz.

RESULTS

In AD patients, the absolute low frequency magnetic power was significantly and rather diffusely increased relative to controls with a fronto-central maximum. High frequency power values were significantly decreased over the occipital and temporal areas. Reactivity to eye-opening and mental tasks was reduced in the patient group. Relative to controls, a general decrease of MEG coherence values, including all frequencies analyzed, was found in AD patients.

CONCLUSIONS

These observations confirm the pattern of changes in spectral power and reactivity known from EEG studies and suggest that coherence decreases in AD patients are widespread and include frequencies outside the alpha band.

The diagnostic value of electroencephalography in mild senile Alzheimer's disease

OBJECTIVE

We investigated the diagnostic value of the visually assessed electroencephalogram (EEG) in patients with mild Alzheimer's disease (AD), using the grand total of EEG (GTE) score.

METHODS

Forty-nine non-demented control subjects with and without minimal cognitive impairment from the general population and 86 probable AD patients (NINCDS-ADRDA criteria), consecutively referred to a memory clinic, participated in this study.

RESULTS

Frequency of rhythmic background activity (P<0.05), diffuse slow activity (P<0.001), and reactivity of the rhythmic background activity (P<0.001) were statistically significant related to the diagnosis control subject or AD patient, using logistic regression analysis with adjustment for age and sex. When these subscores were used to confirm the diagnosis of AD, thus at high specificity of 89.1% (GTE cut-off point of 3), the sensitivity was 44.6% and positive predictive value was 88.1%. Incremental ruling-in and ruling-out curves showed a maximum diagnostic gain of 38% for a positive test result at a prior probability ranging from 30 to 40%. At high pretest probability levels of 80-90%, the diagnostic gain for a positive test result was low, varying from 7 to 14%.

CONCLUSION

In conclusion, the visually assessed EEG may give a clinically meaningful contribution to the diagnostic evaluation of AD when there is diagnostic doubt.

The role of the electroencephalogram in the diagnosis of dementia of the Alzheimer type: an attempt at technology assessment

In a first attempt at technology assessment of the electroencephalogram (EEG) in the diagnosis of patients with Alzheimer's disease (AD), three conclusions were reached: notwithstanding the well defined clinical criteria, there remains a need for a laboratory technique to confirm the diagnosis since a 100% accuracy cannot be obtained by clinical methods only; although the EEG has a high sensitivity in separating AD patients from normal controls, the sensitivity of the EEG is at present not satisfactory when studying populations with a low prevalence of AD patients; the sensitivity of the EEG is higher or equal to the best other laboratory techniques (magnetic resonance imaging [MRI], computerized tomography [CT], SPECT, PET) available at the moment. Since the EEG and MRI can be helpful in different aspects of the differential diagnosis it is argued that all AD patients should be studied at least once by EEG as well as by MRI.

Functional EEG mapping and SPECT in detoxified male alcoholics

Fifteen alcoholics diagnosed according to DSM-III-R, who were detoxified for at least 2 weeks and showed no clinical withdrawal signs, were investigated with 16 channel EEG mapping during resting, manumotor and music perception conditions, and were compared with 13 control persons. Single photon emission computed tomography (SPECT) using hexa-methyl-propilene-amine-oxime (HMPAO) labeled with 99m-technetium (99mTc) as tracer was performed separately (in patients only) and submitted to semiquantitative region of interest (ROI) analysis in 2 slices, 6 and 10 cm above canthomeatal line, respectively. Resting EEG showed increased power values in fast beta frequency band for the detoxified alcoholics. On cortical stimulation, patients showed signs of pathological EEG reactivity. Correlations of EEG parameters to cerebral blood flow (CBF) values (patients only) yielded coefficients around zero for all frequency bands (signs of uncoupling). All findings point to organic brain dysfunctions in these patients which extend beyond the period of withdrawal.

[Digital EEG with brain mapping in Alzheimer's dementia and Parkinson's disease. A prospective controlled study]

In order to evaluate the EEG activity during wakefulness in senile dementia of the Alzheimer type (AD) and Parkinson's disease (PD), a prospective controlled study was performed. We compared 6 AD and 11 PD patients with a control group of 12 patients with mild to moderate major chronic depression (DSM-III-R, 1987). The median of the frequencies and the power of the posterior dominant activity was obtained in the three groups using spectral analysis. The posterior activity had a frequency of 8.79 +/- 0.52 (mean +/- sd) in the control group, 6.65 +/- 0.80 (mean +/- sd) in the AD group and 7.69 +/- 1.39 (mean +/- sd) in the PD group. The experimental hypothesis that patients with AD and PD differ from controls in relation to the background activity (defined as abnormal < 8) was confirmed by the chi square test (p = 0.01) and the t test showed that the mean of the frequency of the posterior power was significantly lower in AD (p = 0.01) and PD (p = 0.05) patients, compared with the controls. The results indicate that this abnormality could be correlated with the degree of cortical damage and natural history of these disorders.

Quantitative EEG analysis during motor function and music perception in Tourette's syndrome

Gilles de la Tourette's syndrome (TS) is a neurobehavioral disorder of childhood onset that is characterized by motor and vocal tics and associated behavioral disturbances including obsessive-compulsive symptoms. We performed 30 channel quantitative electroencephalograms (EEGs) on 13 Tourette patients and 26 controls and studied both resting and manumotor/music perception activation conditions. Resting EEGs did not show any differences between patients and controls, as known from the literature. However, during simple and complex hand movements, as well as music perception tasks, there were subtle differences predominantly in alpha frequency. They suggested reduced brain activation during motor tasks in frontal and central regions, and on music perception in temporal and parietal regions, respectively. These findings may add evidence to the functional neuroanatomy of Tourette syndrome, affecting more areas than disturbed motor circuits.

Psychomotor disturbances in psychiatric patients as a possible basis for new attempts at differential diagnosis and therapy. Part VI. Evaluation of psychomotor training programs in schizophrenic patients

Parts I-III of this series established signs of disturbed motor performance--the "psychotic motor syndrome" (PMS)--in schizophrenic and endogenous depressed patients, which was not found in neurotic/reactive depressed nor healthy persons. Part IV yielded EEG signs of concomitant brain dysfunction in these patients, which were demonstrated by other (SPECT/PET) neuroimaging methods also. In part V we engaged in the development of motor-training programs applied both actively and mentally, using the PMS as target syndrome in depressed patients. We hypothesized that motor training would not only improve disturbed motor behaviour, but ameliorate other symptoms of psychopathology additionally, which was supported for these patients. Part VI is the final paper of this series demonstrating favourable results of our motor-training programs in 96 schizophrenic inpatients in two separate investigations. A general discussion to the whole series attempts to link motor symptoms to neuroimaging findings of brain dysfunction during motor challenge and to modern three- and four-factor models of schizophrenic symptomatology. A final version of our complete training programs will be published as an appendix to this paper along with information regarding the abbreviated test battery.