Abstract Dementia is a syndrome characterised by cognitive impairments, with a loss of learning/memory abilities at the earlier stages and executive dysfunction at the later stages. However, recent studies have suggested that impairments in both learning/memory abilities and executive functioning might co-exist. Cognitive impairments have been primarily evaluated using neuropsychological assessments, such as the Mini-Mental State Examination (MMSE). Recently, neuroimaging techniques such as magnetoencephalography (MEG), which assess changes in resting-state brain activity, have also been used as biomarkers for cognitive impairment. However, it is unclear whether these changes reflect dysfunction in executive function as well as learning and memory. In this study, parameters from the MEG for brain activity, MMSE for learning/memory, and Frontal Assessment Battery (FAB) for executive function were compared within 207 individuals. Three MEG parameters were used as representatives of resting-state brain activity: median frequency, individual alpha frequency, and Shannon’s spectral entropy. Regression analysis showed that median frequency was predicted by both the MMSE and FAB scores, while individual alpha frequency and Shannon’s spectral entropy were predicted by MMSE and FAB scores, respectively. Our results indicate that MEG spectral parameters reflect both learning/memory and executive functions, supporting the utility of MEG as a biomarker of cognitive impairment. 

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Distinctive effects of executive dysfunction and loss of learning/memory abilities on resting-state brain activity

Frontocentral delta-beta amplitude coupling in endometriosis-related chronic pelvic pain

Premenstrual dysphoric disorder (PMDD) is a psychiatric condition characterized by extreme mood shifts, anxiety, and irritability during the premenstrual period. Abnormal sensitivity to allopregnanolone, a neurosteroid that normally potentiates inhibition, and an increased ratio of neural excitation-to-inhibition (E/I) have been linked to the pathophysiology of PMDD. We hypothesized that in subjects with PMDD these factors will lead to an altered frequency of magnetoencephalographic (MEG) visual gamma oscillations, altered modulation of their power by the strength of excitatory drive and to an altered perceptual spatial suppression. We examined women with PMDD and age-matched control women twice: during the asymptomatic follicular and symptomatic luteal phases of the menstrual cycle (MC). MEG gamma oscillations were recorded while modulating excitatory drive to the visual cortex by increasing drift rate of high-contrast visual gratings. Perceptual suppression was assessed as a degree of impairment of the discrimination of visual motion direction with increasing stimulus size. In women with PMDD, the gamma response (GR) peak frequency and its modulation by the drift rate were normal, whereas modulation of the GR power was significantly altered. A moderate increase in drift rate had an unusually strong facilitating effect on the GR power in PMDD, regardless of the MC phase. In contrast, the effect of increasing drift rate, which normally suppresses GR power, was attenuated in PMDD in the luteal phase and predicted symptom severity estimated on the same day. Perceptual spatial suppression did not differ between the groups, but decreased from the follicular to the luteal phase only in PMDD subjects. The atypical GR power modulation suggests that neuronal excitability in the visual cortex is constitutively elevated in women with PMDD, and that their E/I ratio is additionally shifted toward excitation during the luteal phase, possibly due to an abnormal sensitivity to neurosteroids. However, the unchanged frequency of GR and normal spatial suppression in women with PMDD speak against the dysfunction of their inhibitory neurons, at least those involved in generation of visual gamma oscillations. Three key points Atypical modulation of visual gamma power by excitatory drive in women with PMDD suggests the presence of neuronal hyperexcitability, which is exacerbated during the symptomatic luteal phase, possibly due to altered sensitivity to neurosteroids. The peak frequency of gamma oscillations does not differ between women with PMDD and control women and demonstrates the luteal phase-specific effect of the 1st scan in both groups, which suggest normal functioning of inhibitory neurons in the visual cortex in PMDD. The presence of normal perceptual spatial suppression also speaks against inhibitory deficit in the visual cortex in PMDD.

Altered visual cortex excitability in premenstrual dysphoric disorder: Evidence from magnetoencephalographic gamma oscillations and perceptual suppression

Background: Heartfulness meditation (HM) has been shown to have positive impacts on cognition and well-being, which makes it important to look into the neurophysiological mechanisms underlying the phenomenon. Aim: A cross-sectional study was conducted on HM meditators and nonmeditators to assess frontal electrical activities of the brain and self-reported anxiety and mindfulness. Settings and Design: The present study employed a cross-sectional design. Methods: Sixty-one participants were recruited, 28 heartfulness meditators (average age male: 31.54 ± 4.2 years and female: 30.04 ± 7.1 years) and 33 nonmeditators (average age male: 25 ± 8.5 years and female: 23.45 ± 6.5 years). An electroencephalogram (EEG) was employed to assess brain activity during baseline (5 min), meditation (10 min), transmission (10 min) and post (5 min). Self-reported mindfulness and anxiety were also collected in the present study. The EEG power spectral density (PSD) and coherence were processed using MATLAB. The statistical analysis was performed using an independent sample t-test for trait mindfulness and anxiety, repeated measures analysis of variance (ANOVA) for state mindfulness and anxiety, and Two-way multivariate ANOVA for EEG spectral frequency and coherence. Results: The results showed higher state and trait mindfulness, P < 0.05 and P < 0.01, respectively, and lower state and trait anxiety, P < 0.05 and P < 0.05, respectively. The PSD outcomes showed higher theta (P < 0.001) and alpha (P < 0.01); lower beta (P < 0.001) and delta (P < 0.05) power in HM meditators compared to nonmeditators. Similarly, higher coherence was found in the theta (P < 0.01), alpha (P < 0.05), and beta (P < 0.01) bands in HM meditators. Conclusions: These findings suggest that HM practice may result in wakeful relaxation and internalized attention that can influence cognition and behavior.

Heartfulness Meditation Alters Electroencephalogram Oscillations: An Electroencephalogram Study

Migraine is a common, headache disorder characterized by recurrent episodes of headache often associated with nausea, vomiting, photophobia, and phonophobia. Prior to puberty, boys and girls are equally affected. Female preponderance emerges after puberty. Migraine pathophysiology is not fully understood, and although the hormonal effect of estrogen is significant, it is not clear how hormonal phases affect brain excitability and EEG patterns in women with migraine. The objective of this research was to study the effect of migraine on the resting-state EEG activity of women during the luteal phase. This work compares electroencephalographic (EEG) absolute power in different frequency bands and scalp areas between young women who suffer from migraine and had a migraine attack within 24 h prior to EEG recording (experimental) and ten age-matched young healthy women (controls), all with normal menstrual cycles. For women with migraine, we found a significant decrease/increase in alpha power in the occipitoparietal/frontocentral area, significant decrease in beta power for all areas, significant decrease in delta power in the temporal area, and significant decrease in theta power in the frontocentral and occipitoparietal area. We concluded that women with migraine have a distinct electroencephalographic pattern during the luteal phase in comparison with control women. A possible explanation might be an intermittent rhythmic activity linked to pain.

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Quantitative Electroencephalographic Analysis in Women with Migraine during the Luteal Phase

Resting-state neural oscillations are used as biomarkers for functional diseases such as dementia, epilepsy, and stroke. However, accurate interpretation of clinical outcomes requires the identification and minimisation of potential confounding factors. While several studies have indicated that the menstrual cycle also alters brain activity, most of these studies were based on visual inspection rather than objective quantitative measures. In the present study, we aimed to clarify the effect of the menstrual cycle on spontaneous neural oscillations based on quantitative magnetoencephalography (MEG) parameters. Resting-state MEG activity was recorded from 25 healthy women with normal menstrual cycles. For each woman, resting-state brain activity was acquired twice using MEG: once during their menstrual period (MP) and once outside of this period (OP). Our results indicated that the median frequency and peak alpha frequency of the power spectrum were low, whereas Shannon spectral entropy was high, during the MP. Theta intensity within the right temporal cortex and right limbic system was significantly lower during the MP than during the OP. High gamma intensity in the left parietal cortex was also significantly lower during the MP than during the OP. Similar differences were also observed in the parietal and occipital regions between the proliferative (the late part of the follicular phase) and secretory phases (luteal phase). Our findings suggest that the menstrual cycle should be considered to ensure accurate interpretation of functional neuroimaging in clinical practice.

/pdf/the-menstrual-cycle-alters-resting-state-cortical-activity-a-58vygaovav.pdf

The Menstrual Cycle Alters Resting-State Cortical Activity: A Magnetoencephalography Study.

Retinal prosthesis is a promising treatment for vision degeneration. However, clinical experiments show that the patients can only recognize several grayscales at low resolution with electrical stimulation. This paper proposes a retinal prosthesis chip with binarization and edge detection functions to maximize the brightness difference and reduce redundant information. The binarization operation is designed as a column-parallel processing element for saving space. Moreover, the fill factor achieves 50.79% by separating the sensor and stimulator into different chips. Finally, the SPICE simulator verified the effectiveness of the proposed circuit, which achieves an FoM of 110nW/(frame·pixel). 

3D-stacked retinal prosthesis chip with binary image capture and edge detection functions for human visual restoration

The increase in the number of visually impaired people has led to active research on artificial retinas. In our laboratory, we study a fully-implantable retinal prosthesis using a 3D-stacked artificial retina chip, which provides highly visible visual information with edge enhancement and binarization functions. However, since the visibility of objects can be significantly reduced when the ambient illumination is low, the light and dark adaptation (LDA) function is needed to provide the same visibility regardless of the ambient illumination. Conventional LDA functions have operability, comfort, and circuit area problems in these situations. In this study, we proposed a small-area LDA function circuit that provided visual information with high quality of life and evaluated a prototype circuit.

Implementation of Light and Dark Adaptation Function for High QOL 3D-Stacked Artificial Retina Chip

This paper presents the first circuit that enables microsaccade function in an artificial eyeball system. Currently, the artificial eyeball is receiving increasing development in vision restoration. The main challenge is that the human eye is born with microsaccade that helps refresh vision, avoiding perception fading while the gaze is fixed for a long period, and without microsaccade, high-quality vision restoration is difficult. The proposed electronic microsaccade (E-μSaccade) circuit addresses the issue, and it is intrinsically safe because only charge-balanced stimulus pulses are allowed for stimulation. The E-μSaccade circuit adopts light-to-frequency modulation; due to the circuit’s leakage and dark current of light-sensitive elements, stimulus pulses of a frequency lower than tens of Hz occur, which is the cause of flickering vision. A flicker vision prevention (FVP) circuit is proposed to mitigate the issue. The proposed circuits are designed in a 0.18 μm standard CMOS process. The simulation and measurement results show that the E-μSaccade circuit helps refresh the stimulation pattern and blocks the low-frequency output.

https://www.mdpi.com/2079-9292/12/13/2836/pdf?version=1687852607

Kohei Nakamura

Papers

The Menstrual Cycle Alters Resting-State Cortical Activity: A Magnetoencephalography Study.

3D-stacked retinal prosthesis chip with binary image capture and edge detection functions for human visual restoration

Implementation of Light and Dark Adaptation Function for High QOL 3D-Stacked Artificial Retina Chip

An Electronic Microsaccade Circuit with Charge-Balanced Stimulation and Flicker Vision Prevention for an Artificial Eyeball System