Attentional selection and communication through coherence: Scope and limitations.

Synchronous neural oscillations are strongly associated with a variety of perceptual, cognitive, and behavioural processes. It has been proposed that the role of the synchronous oscillations in these processes is to facilitate information transmission between brain areas, the 'communication through coherence,' or CTC hypothesis. The details of how this mechanism would work, however, and its causal status, are still unclear. Here we investigate computationally a proposed mechanism for selective attention that directly implicates the CTC as causal. The mechanism involves alpha band (about 10 Hz) oscillations, originating in the pulvinar nucleus of the thalamus, being sent to communicating cortical areas, organizing gamma (about 40 Hz) oscillations there, and thus facilitating phase coherence and communication between them. This is proposed to happen contingent on control signals sent from higher-level cortical areas to the thalamic reticular nucleus, which controls the alpha oscillations sent to cortex by the pulvinar. We studied the scope of this mechanism in parameter space, and limitations implied by this scope, using a computational implementation of our conceptual model. Our results indicate that, although the CTC-based mechanism can account for some effects of top-down and bottom-up attentional selection, its limitations indicate that an alternative mechanism, in which oscillatory coherence is caused by communication between brain areas rather than being a causal factor for it, might operate in addition to, or even instead of, the CTC mechanism.

Perceptual training improves audiovisual integration by enhancing alpha-band oscillations and functional connectivity in older adults.

Numerous studies on perceptual training exist, however, most have focused on the precision of temporal audiovisual perception, while fewer have concentrated on ability promotion for audiovisual integration (AVI). To investigate these issues, continuous 5-day audiovisual perceptual training was applied, during which electroencephalography was performed in response to auditory-only (A), visual-only (V) and audiovisual (AV) stimuli before and after training. The results showed that the perceptual sensitivity was greater for training group than for control group and was greater in the posttest than in the pretest. The response to the AV stimulus was significantly faster in the posttest than in the pretest for the older training group but was significantly greater for A and V stimuli for the younger training group. Electroencephalography analysis found higher P3 AVI amplitudes [AV-(A + V)] in the posttest than in the pretest for training group, which were subsequently reflected by an increased alpha (8-12 Hz) oscillatory response and strengthened global functional connectivity (weighted phase lag index). Furthermore, these facilitations were greater for older training groups than for younger training groups. These results confirm the age-related compensatory mechanism for AVI may be strengthened as audiovisual perceptual training progresses, providing an effective candidate for cognitive intervention in older adults.

Time to get deep.

Asymmetries in the size of structures deep below the cortex explain how alpha oscillations in the brain respond to shifts in attention.

Modulation of alpha oscillations by attention is predicted by hemispheric asymmetry of subcortical regions.

Evidence suggests that subcortical structures play a role in high-level cognitive functions such as the allocation of spatial attention. While there is abundant evidence in humans for posterior alpha band oscillations being modulated by spatial attention, little is known about how subcortical regions contribute to these oscillatory modulations, particularly under varying conditions of cognitive challenge. In this study, we combined MEG and structural MRI data to investigate the role of subcortical structures in controlling the allocation of attentional resources by employing a cued spatial attention paradigm with varying levels of perceptual load. We asked whether hemispheric lateralization of volumetric measures of the thalamus and basal ganglia predicted the hemispheric modulation of alpha-band power. Lateral asymmetry of the globus pallidus, caudate nucleus, and thalamus predicted attention-related modulations of posterior alpha oscillations. When the perceptual load was applied to the target and the distractor was salient caudate nucleus asymmetry predicted alpha-band modulations. Globus pallidus was predictive of alpha-band modulations when either the target had a high load, or the distractor was salient, but not both. Finally, the asymmetry of the thalamus predicted alpha band modulation when neither component of the task was perceptually demanding. In addition to delivering new insight into the subcortical circuity controlling alpha oscillations with spatial attention, our finding might also have clinical applications. We provide a framework that could be followed for detecting how structural changes in subcortical regions that are associated with neurological disorders can be reflected in the modulation of oscillatory brain activity.

Novice Users' Brain Activity and Biomechanics Change After Practicing Walking With an Ankle Exoskeleton.

Walking with an exoskeleton represents a sophisticated interplay between human physiology and mechanical augmentation, yet understanding of cortical responses in this context remains limited. To address this gap, this study aimed to explore cortical responses during walking with an ankle exoskeleton, examining how these responses evolve with familiarity to the augmentation. Healthy participants without prior exoskeleton experience underwent EEG, EMG, and motion capture analysis while walking with exoskeleton assistance at 1.2m/s. Initially, exoskeleton-assisted walking induced significant biomechanical changes accompanied by corresponding cortical alterations, leading to increased cortical involvement. In addition, after a brief familiarization period, significant increases in alpha band cortical power were observed, indicating decreased cortical engagement. These findings hold significance for elucidating the cortical mechanisms involved in exoskeleton-assisted walking and may contribute to the development of more seamlessly integrated augmentation devices.

Alpha tACS on Parieto-Occipital Cortex Mitigates Motion Sickness Based on Multiple Physiological Observation.

Approximately one third of the population is prone to motion sickness (MS), which is associated with the dysfunction in the integration of sensory inputs. Transcranial alternating current stimulation (tACS) has been widely used to modulate neurological functions by affecting neural oscillation. However, it has not been applied in the treatment of motion sickness. This study aims to investigate changes in brain oscillations during exposure to MS stimuli and to further explore the potential impact of tACS with the corresponding frequency and site on MS symptoms. A total of 19 subjects were recruited to be exposed to Coriolis stimuli to complete an inducing session. After that, they were randomly assigned to tACS stimulation group or sham stimulation group to complete a stimulation session. Electroencephalography (EEG), electrocardiogram, and galvanic skin response were recorded during the experiment. All the subjects suffering from obvious MS symptoms after inducing session were observed that alpha power of four channels of parieto-occipital lobe significantly decreased (P7: t =3.589, p <0.001; P8: t =2.667, p <0.05; O1: t =3.556, p <0.001; O2: t =2.667, p <0.05). Based on this, tACS group received the tACS stimulation at 10Hz from Oz to CPz. Compared to sham group, tACS stimulation significantly improved behavioral performance and entrained the alpha oscillation in individuals whose alpha power decrease during the inducing session. The findings show that parieto-occipital alpha oscillation plays a critical role in the integration of sensory inputs, and alpha tACS on parieto-occipital can become a potential method to mitigate MS symptoms.

Working memory enhancement using real-time phase-tuned transcranial alternating current stimulation.

BACKGROUND: Prior work has shown that transcranial alternating current stimulation (tACS) of parietooccipital alpha oscillations (8-14 Hz) can modulate working memory (WM) performance as a function of the phase lag to endogenous oscillations. However, leveraging this effect using real-time phase-tuned tACS has not been feasible so far due to stimulation artifacts preventing continuous phase tracking. OBJECTIVES AND HYPOTHESIS: We aimed to develop a system that tracks and adapts the phase lag between tACS and ongoing parietooccipital alpha oscillations in real-time. We hypothesized that such real-time phase-tuned tACS enhances working memory performance, depending on the phase lag. METHODS: We developed real-time phase-tuned closed-loop amplitude-modulated tACS (CLAM-tACS) targeting parietooccipital alpha oscillations. CLAM-tACS was applied at six different phase lags relative to ongoing alpha oscillations while participants (N = 21) performed a working memory task. To exclude that behavioral effects of CLAM-tACS were mediated by other factors such as sensory co-stimulation, a second group of participants (N = 25) received equivalent stimulation of the forehead. RESULTS: WM accuracy improved in a phase lag dependent manner (p = 0.0350) in the group receiving parietooccipital stimulation, with the strongest enhancement observed at 330° phase lag between tACS and ongoing alpha oscillations (p = 0.00273, d = 0.976). Moreover, across participants, modulation of frontoparietal alpha oscillations correlated both in amplitude (p = 0.0248) and phase (p = 0.0270) with the modulation of WM accuracy. No such effects were observed in the control group receiving frontal stimulation. CONCLUSIONS: Our results demonstrate the feasibility and efficacy of real-time phase-tuned CLAM-tACS in modulating both brain activity and behavior, thereby paving the way for further investigation into brain-behavior relationships and the exploration of innovative therapeutic applications.

Evidence of bottom-up homeostatic modulation induced taVNS during emotional and Go/No-Go tasks.

Bilateral transcutaneous auricular vagus nerve stimulation (taVNS) - a non-invasive neuromodulation technique - has been investigated as a safe and feasible technique to treat many neuropsychiatric conditions. such as epilepsy, depression, anxiety, and chronic pain. Our aim is to investigate the effect of taVNS on neurophysiological processes during emotional and Go/No-Go tasks, and changes in frontal alpha asymmetry. We performed a randomized, double-blind, sham-controlled trial with 44 healthy individuals who were allocated into two groups (the active taVNS group and the sham taVNS group). Subjects received one session of taVNS (active or sham) for 60 min. QEEG was recorded before and after the interventions, and the subjects were assessed while exposed to emotional conditions with sad and happy facial expressions, followed by a Go/No-Go trial. The results demonstrated a significant increase in N2 amplitude in the No-Go condition for the active taVNS post-intervention compared to the sham taVNS after adjusting by handedness, mood, and fatigue levels (p = 0.046), significantly reduced ERD during sad conditions after treatment (p = 0.037), and increased frontal alpha asymmetry towards the right frontal hemisphere during the emotional task condition (p = 0.046). Finally, we observed an interesting neural signature in this study that suggests a bottom-up modulation from brainstem/subcortical to cortical areas as characterized by improved lateralization of alpha oscillations towards the frontal right hemisphere, and changes in ERP during emotional and Go/No-Go tasks that suggests a better subcortical response to the tasks. Such bottom-up effects may mediate some of the clinical effects of taVNS.

Prediction of behavioral performance by alpha-band phase synchronization in working memory.

Working memory (WM) is a cognitive system with limited capacity that can temporarily store and process information. The purpose of this study was to investigate functional connectivity based on phase synchronization during WM and its relationship with the behavioral response. In this regard, we recorded EEG/Eye tracking data of seventeen healthy subjects while performing a memory-guided saccade (MGS) task with two different positions (near eccentricity and far eccentricity). We computed saccade error as memory performance and measured functional connectivity using Phase Locking Value (PLV) in the alpha frequency band (8-12 Hz). The results showed that PLV is negatively correlated with saccade error. Our finding indicated that during the maintenance period, PLV between the frontal and visual area in trials with low saccade error increased significantly compared to trials with high saccade error. Furthermore, we observed a significant difference between PLV for near and far conditions in the delay period. The results suggest that PLV in memory maintenance, in addition to predicting saccade error as behavioral performance, can be related to the coding of spatial information in WM.

EEG alpha band functional brain network correlates of cognitive performance in children after perinatal stroke.

Mechanisms underlying cognitive impairment after perinatal stroke could be explained through brain network alterations. With aim to explore this connection, we conducted a matched test-control study to find a correlation between functional brain network properties and cognitive functions in children after perinatal stroke. First, we analyzed resting-state functional connectomes in the alpha frequency band from a 64-channel resting state EEG in 24 children with a history of perinatal stroke (12 with neonatal arterial ischemic stroke and 12 with neonatal hemorrhagic stroke) and compared them to the functional connectomes of 24 healthy controls. Next, all participants underwent cognitive evaluation. We analyzed the differences in functional brain network properties and cognitive abilities between groups and studied the correlation between network characteristics and specific cognitive functions. Functional brain networks after perinatal stroke had lower modularity, higher clustering coefficient, higher interhemispheric strength, higher characteristic path length and higher small world index. Modularity correlated positively with the IQ and processing speed, while clustering coefficient correlated negatively with IQ. Graph metrics, reflecting network segregation (clustering coefficient and small world index) correlated positively with a tendency to impulsive decision making, which also correlated positively with graph metrics, reflecting stronger functional connectivity (characteristic path length and interhemispheric strength). Our study suggests that specific cognitive functions correlate with different brain network properties and that functional network characteristics after perinatal stroke reflect poorer cognitive functioning.

Operating in a second language lowers cognitive interference during creative idea generation: Evidence from brain oscillations in bilinguals.

Tasks measuring human creativity overwhelmingly rely on both language comprehension and production. Although most of the world's population is bilingual, few studies have investigated the effects of language of operation on creative output. This is surprising given that fluent bilinguals master inhibitory control, a mechanism also at play in creative idea evaluation. Here, we compared creative output in the two languages of Polish(L1)-English(L2) bilinguals engaged in a cyclic adaptation of the Alternative Uses Task increasing the contribution of idea evaluation (convergent thinking). We show that Polish-English bilinguals suffer less cognitive interference when generating unusual uses for common objects in the L2 than the L1, without incurring a significant drop in idea originality. Right posterior alpha oscillation power, known to reflect creative thinking, increased over cycles. This effect paralleled the increase in originality ratings over cycles, and lower alpha power (8-10 Hz) was significantly greater in the L1 than the L2. Unexpectedly, we found greater beta (16.5-28 Hz) desynchronization in the L2 than the L1, suggesting that bilingual participants suffered less interference from competing mental representations when performing the task in the L2. Whereas creative output seems unaffected by language of operation overall, the drop in beta power in the L2 suggests that bilinguals are not subjected to the same level of semantic flooding in the second language as they naturally experience in their native language.

Individual posterior alpha rhythms and cognitive reserve as possible early prognostic markers in people with subjective memory complaints.

Subjective memory complaints (SMCs) are a memory disorder that often precedes mild cognitive impairment (MCI) or Alzheimer's disease (AD). Both individual alpha rhythms and cognitive reserve (CR) represent key features of SMCs and provide useful tools to characterize and predict the course of the disorder. We studied whether older people with SMCs may also present some abnormal resting state electroencephalogram (rsEEG) alpha rhythms, and whether alpha rhythms are associated with CR. To do this, eyes-closed rsEEG were recorded in 68 older people with and without SMCs. The individual alpha indexes alpha/theta transition frequency (TF) and individual alpha frequency peak (IAFp) were computed. TF and IAFp were also used to determine the alpha1, alpha2, and alpha3 power frequency. Results indicated no differences in TF or IAFp between older people with SMCs and controls. The SMCs group showed a reduction in alpha3 power in comparison with controls. Specifically, women with SMCs were characterized by a significant decrease in alpha3 power compared to control women. Furthermore, only in SMCs group, greater CR was associated with slow IAFp. In sum, these results suggest that TF and IAFp are two stable indexes that are not influenced by the presence of SMCs. However, the reduction in alpha3, as observed in women with SMCs, shows an abnormal posterior rsEEG at alpha power. Finally, the compensatory mechanisms of CR appear to interact with the neurophysiological mechanisms that underlie the regulation of alpha rhythms.

Effects of neurofeedback training on the alpha activity in quantitative electroencephalography, cognitive function, and speech perception in elderly with presbycusis: a quasi-experimental study.

BACKGROUND: This study aimed to investigate the effects of neurofeedback training (NFT) on alpha activity in quantitative electroencephalography (QEEG), cognitive function, and speech perception in elderly with presbycusis. METHODS: This study was conducted from June 15 to November 30, 2020. The experimental group (n = 28) underwent NFT, while the control group (n = 31) was instructed to continue with their routine daily life. The NFT conducted for 40 min, two times a week, for a total of 16 sessions and was performed using Neuroharmony S and BrainHealth 2.7. The alpha activity was measured as alpha waves using QEEG. The cognitive function was measured using the Korean version of Mini-Mental Status Examination, digit span forward and backward (DSF and DSB). The speech perception was measured using the word and sentence recognition score (WRS and SRS) using an audiometer with the Korean Standard Monosyllabic Word Lists for Adults. RESULTS: The experimental group demonstrated improvement in the alpha wave of the left frontal lobe measured as alpha activity (t=-2.521, p = .018); MMSE-K (t=-3.467, p < .01), and DSF (t=-2.646, p < .05) measured as cognitive function; and WRS (t=-3.255, p = .003), and SRS (t=-2.851, p = .008) measured as speech perception compared to the control group. CONCLUSIONS: This study suggests that NFT could be considered an effective cognitive and auditory rehabilitation method based on brain and cognitive science for improving alpha activity, cognitive function, and speech perception.

Neural basis of lower-limb visual feedback therapy: an EEG study in healthy subjects.

BACKGROUND: Video-feedback observational therapy (VOT) is an intensive rehabilitation technique based on movement repetition and visualization that has shown benefits for motor rehabilitation of the upper and lower limbs. Despite an increase in recent literature on the neurophysiological effects of VOT in the upper limb, there is little knowledge about the cortical effects of visual feedback therapies when applied to the lower limbs. The aim of our study was to better understand the neurophysiological effects of VOT. Thus, we identified and compared the EEG biomarkers of healthy subjects undergoing lower limb VOT during three tasks: passive observation, observation and motor imagery, observation and motor execution. METHODS: We recruited 38 healthy volunteers and monitored their EEG activity while they performed a right ankle dorsiflexion task in the VOT. Three graded motor tasks associated with action observation were tested: action observation alone (O), motor imagery with action observation (OI), and motor execution synchronized with action observation (OM). The alpha and beta event-related desynchronization (ERD) and event-related synchronization (or beta rebound, ERS) rhythms were used as biomarkers of cortical activation and compared between conditions with a permutation test. Changes in connectivity during the task were computed with phase locking value (PLV). RESULTS: During the task, in the alpha band, the ERD was comparable between O and OI activities across the precentral, central and parietal electrodes. OM involved the same regions but had greater ERD over the central electrodes. In the beta band, there was a gradation of ERD intensity in O, OI and OM over central electrodes. After the task, the ERS changes were weak during the O task but were strong during the OI and OM (Cz) tasks, with no differences between OI and OM. CONCLUSION: Alpha band ERD results demonstrated the recruitment of mirror neurons during lower limb VOT due to visual feedback. Beta band ERD reflects strong recruitment of the sensorimotor cortex evoked by motor imagery and action execution. These results also emphasize the need for an active motor task, either motor imagery or motor execution task during VOT, to elicit a post-task ERS, which is absent during passive observation. Trial Registration NCT05743647.

Reduced approach disposition in familial risk for depression: Evidence from time-frequency alpha asymmetries.

Despite the promising role of alpha and delta power in reflecting reduced approach disposition in depression, to date, it is unclear whether these measures can be employed to identify at-risk individuals. Hence, the present study investigated affective disposition in 32 unaffected individuals with a family history of depression (23 F) and 30 individuals without a family history of depression (21 F) through a data-driven analysis of alpha and delta time-frequency power during the viewing of pleasant, neutral, and unpleasant pictures. Different patterns of posterior alpha asymmetry emerged within each group. Particularly, controls showed greater right posterior alpha desynchronization ~ 600 ms following emotional relative to neutral pictures presentation. Conversely, the group with a family history of depression showed greater posterior left alpha desynchronization only to unpleasant relative to neutral images in a later time window (> 900 ms). Hence, depression vulnerability seems to be characterized by a blunted reactivity to pleasant and delayed reactivity to unpleasant stimuli with a distinct posterior distribution relative to the controls. Finally, the two groups showed a comparable pattern of greater delta power to emotional relative to neutral cues. Overall, initial support was provided for the employment of time-frequency alpha power changes during affective processing in identifying blunted approach disposition in unaffected at-risk individuals.

Evaluation of Acupuncture Efficacy in Modulating Brain Activity With Periodic-Aperiodic EEG Measurements.

Acupuncture is an important therapeutic method of traditional Chinese medicine and can effectively modulate brain disorders. The therapeutic efficacy of acupuncture is hard to evaluate due to lacking of effective measurements of brain activity. In this work, we design an EEG-based monitoring system to evaluate therapeutic effect of acupuncture on human brain by extracting periodic-aperiodic features. Power spectral density is estimated to compute the adjusted power of periodic oscillatory rhythm in EEG under acupuncture stimulation. It is exhibited that the brain activity in alpha band (8-12 Hz) is significantly enhanced during acupuncture, especially in parietal and occipital lobe regions. To probe the modulatory effect of acupuncture on aperiodic brain activity, we calculate the aperiodic exponent based on the parameterization of EEG power spectra. The aperiodic exponent decreases along with acupuncture process, which is more significant in central and frontal lobe regions. Furthermore, sensitivity of different brain regions to acupuncture is assessed by the integration of adjusted power and aperiodic exponent. Experimental results demonstrate the effectiveness of proposed periodic-aperiodic measurements of EEG signals, by which different effects of four acupuncture manipulations are precisely evaluated and a knowledge graph is established. The monitoring system provides a new perspective to quantitatively evaluate acupuncture effect on human brain and improve its therapeutic efficacy in clinical applications for neural disorders.

The role of alpha oscillations in free- and goal-directed semantic associations.

Alpha oscillations are known to play a central role in several higher-order cognitive functions, especially selective attention, working memory, semantic memory, and creative thinking. Nonetheless, we still know very little about the role of alpha in the generation of more remote semantic associations, which is key to creative and semantic cognition. Furthermore, it remains unclear how these oscillations are shaped by the intention to "be creative," which is the case in most creativity tasks. We aimed to address these gaps in two experiments. In Experiment 1, we compared alpha oscillatory activity (using a method which distinguishes genuine oscillatory activity from transient events) during the generation of free associations which were more vs. less distant from a given concept. In Experiment 2, we replicated these findings and also compared alpha oscillatory activity when people were generating free associations versus associations with the instruction to be creative (i.e. goal-directed). We found that alpha was consistently higher during the generation of more distant semantic associations, in both experiments. This effect was widespread, involving areas in both left and right hemispheres. Importantly, the instruction to be creative seems to increase alpha phase synchronisation from left to right temporal brain areas, suggesting that intention to be creative changed the flux of information in the brain, likely reflecting an increase in top-down control of semantic search processes. We conclude that goal-directed generation of remote associations relies on top-down mechanisms compared to when associations are freely generated.

Developmental trajectories of EEG aperiodic and periodic components in children 2-44 months of age.

The development of neural circuits has long-lasting effects on brain function, yet our understanding of early circuit development in humans remains limited. Here, periodic EEG power features and aperiodic components were examined from longitudinal EEGs collected from 592 healthy 2-44 month-old infants, revealing age-dependent nonlinear changes suggestive of distinct milestones in early brain maturation. Developmental changes in periodic peaks include (1) the presence and then absence of a 9-10 Hz alpha peak between 2-6 months, (2) nonlinear changes in high beta peaks (20-30 Hz) between 4-18 months, and (3) the emergence of a low beta peak (12-20 Hz) in some infants after six months of age. We hypothesized that the emergence of the low beta peak may reflect maturation of thalamocortical network development. Infant anesthesia studies observe that GABA-modulating anesthetics do not induce thalamocortical mediated frontal alpha coherence until 10-12 months of age. Using a small cohort of infants (n = 23) with EEG before and during GABA-modulating anesthesia, we provide preliminary evidence that infants with a low beta peak have higher anesthesia-induced alpha coherence compared to those without a low beta peak.

Globus pallidus externus drives increase in network-wide alpha power with propofol-induced loss-of-consciousness in humans.

States of consciousness are likely mediated by multiple parallel yet interacting cortico-subcortical recurrent networks. Although the mesocircuit model has implicated the pallidocortical circuit as one such network, this circuit has not been extensively evaluated to identify network-level electrophysiological changes related to loss of consciousness (LOC). We characterize changes in the mesocircuit in awake versus propofol-induced LOC in humans by directly simultaneously recording from sensorimotor cortices (S1/M1) and globus pallidus interna and externa (GPi/GPe) in 12 patients with Parkinson disease undergoing deep brain stimulator implantation. Propofol-induced LOC is associated with increases in local power up to 20 Hz in GPi, 35 Hz in GPe, and 100 Hz in S1/M1. LOC is likewise marked by increased pallidocortical alpha synchrony across all nodes, with increased alpha/low beta Granger causal (GC) flow from GPe to all other nodes. In contrast, LOC is associated with decreased network-wide beta coupling and beta GC from M1 to the rest of the network. Results implicate an important and possibly central role of GPe in mediating LOC-related increases in alpha power, supporting a significant role of the GPe in modulating cortico-subcortical circuits for consciousness. Simultaneous LOC-related suppression of beta synchrony highlights that distinct oscillatory frequencies act independently, conveying unique network activity.

Analysis of the alpha activity envelope in electroencephalography in relation to the ratio of excitatory to inhibitory neural activity.

Alpha waves, one of the major components of resting and awake cortical activity in human electroencephalography (EEG), are known to show waxing and waning, but this phenomenon has rarely been analyzed. In the present study, we analyzed this phenomenon from the viewpoint of excitation and inhibition. The alpha wave envelope was subjected to secondary differentiation. This gave the positive (acceleration positive, Ap) and negative (acceleration negative, An) values of acceleration and their ratio (Ap-An ratio) at each sampling point of the envelope signals for 60 seconds. This analysis was performed on 36 participants with Alzheimer's disease (AD), 23 with frontotemporal dementia (FTD) and 29 age-matched healthy participants (NC) whose data were provided as open datasets. The mean values of the Ap-An ratio for 60 seconds at each EEG electrode were compared between the NC and AD/FTD groups. The AD (1.41 ±0.01 (SD)) and FTD (1.40 ±0.02) groups showed a larger Ap-An ratio than the NC group (1.38 ±0.02, p<0.05). A significant correlation between the envelope amplitude of alpha activity and the Ap-An ratio was observed at most electrodes in the NC group (Pearson's correlation coefficient, r = -0.92 ±0.15, mean for all electrodes), whereas the correlation was disrupted in AD (-0.09 ±0.21, p<0.05) and disrupted in the frontal region in the FTD group. The present method analyzed the envelope of alpha waves from a new perspective, that of excitation and inhibition, and it could detect properties of the EEG, Ap-An ratio, that have not been revealed by existing methods. The present study proposed a new method to analyze the alpha activity envelope in electroencephalography, which could be related to excitatory and inhibitory neural activity.