Alzheimer's disease (AD) is the most common type of neurodegenerative disorder, typically causing dementia along aging. AD is mainly characterized by a pathological extracellular accumulation of ...amyloid-beta peptides that affects excitatory and inhibitory synaptic transmission, inducing aberrant patterns in neuronal circuits. Growing evidence shows that AD targets cortical neuronal networks related to cognitive functions including episodic memory and visuospatial attention. This is partially reflected by the abnormal mechanisms of cortical neural synchronization and coupling that generate resting state electroencephalographic (EEG) rhythms. The cortical neural synchronization is typically indexed by EEG power density. The EEG coupling between electrode pairs probes functional (inter-relatedness of EEG signals) and effective (casual effect from one over the other electrode) connectivity. The former is typically indexed by synchronization likelihood (linear and nonlinear) or spectral coherence (linear), the latter by granger causality or information theory indexes. Here we reviewed literature concerning EEG studies in condition of resting state in AD and mild cognitive impairment (MCI) subjects as a window on abnormalities of the cortical neural synchronization and functional and effective connectivity. Results showed abnormalities of the EEG power density at specific frequency bands (<12Hz) in the MCI and AD populations, associated with an altered functional and effective EEG connectivity among long range cortical networks (i.e. fronto-parietal and fronto-temporal). These results suggest that resting state EEG rhythms reflect the abnormal cortical neural synchronization and coupling in the brain of prodromal and overt AD subjects, possibly reflecting dysfunctional neuroplasticity of the neural transmission in long range cortical networks.
Several heart rate variability (HRV) studies show abnormalities in autonomic nervous control in obese and overweight subjects. However, some of the results appear to be controversial. Here we ...investigate the HRV profile in seventy adult normotensive women and its association with general and visceral adiposity. Specifically, we recorded the electrocardiographic (ECG) activity in subjects during a supine resting state for five minutes in a quiet room late in the morning. Total fat mass (TFM) and visceral adipose tissue (VAT) were instead estimated using dual-energy X-ray absorptiometry (DXA). Finally, we used simple a linear regression analysis of frequency and time-domain parameters to study the relationship between HRV and adiposity. Our data showed an overall reduction of the HRV related to an increase of TFM although this regression appeared significant only for high frequencies (HF). When the linear regression was applied between HRV variables and VAT, the slope of the line increases, thus unveiling a statistically significant relation (i.e. the more VAT, the lower HRV). Finally, a control analysis showed that age does not alter the relation between HRV and VAT when used as a confounding factor in multiple regression. To conclude, these findings point to abnormal activity of the autonomic nervous system (ANS) in subjects with an excess of VAT and represent a starting point to determine a non-invasive index of cardiac wellness for clinical and nutritional application.
To investigate the involvement of the primary motor cortex (M1) in the coordination performance of karate athletes through transcranial magnetic stimulation (TMS).
Thirteen right-handed male karate ...athletes (25.0±5.0 years) and 13 matched non-athlete controls (26.7±6.2 years) were enrolled. A single-pulse TMS was applied using a figure-eight coil stimulator. Resting motor threshold (rMT) was determined. Surface electromyography was recorded from the first dorsal interosseous muscle. Motor evoked potential (MEP) latencies and amplitudes at rMT, 110%, and 120% of rMT were considered. Functional assessment of the coordination performance was assessed by in-phase (IP) and anti-phase (AP) homolateral hand and foot coordination tasks performed at 80, 120, and 180 bpm.
Compared to controls, athletes showed lower rMT (p<0.01), shorter MEP latency (p<0.01) and higher MEP amplitude (p<0.01), with a significant correlation (r = 0.50, p<0.01) between rMT and MEP latency. Coordination decreased with increasing velocity, and better IP performances emerged compared to AP ones (p<0.001). In general, a high correlation between rMT and coordination tasks was found for both IP and AP conditions.
With respect to controls, karate athletes present a higher corticospinal excitability indicating the presence of an activity-dependent alteration in the balance and interactions between inhibitory and facilitatory circuits determining the final output from the M1. Furthermore, the high correlation between corticospinal excitability and coordination performance could support sport-specific neurophysiological arrangements.
Summary
Heart rate variability (HRV) is altered in obese subjects, but whether this is true also in underweight (UW) subjects is still under debate. We investigated the HRV profile in a sample of ...healthy adult women and its association with adiposity. Five‐minute resting state electrocardiographic activity was recorded in 69 subjects grouped according to their body mass index, 23 normal weight (NW), 23 overweight/obese (OW) and 23 UW). Body fat mass (FM) was measured by bio‐impedance. Frequency‐ and time‐domain analyses were performed. Compared to NW, UW and OW subjects showed a significant decrease in HRV indices, as revealed by spectral analysis. No differences were observed between UW and OW subjects. A second‐order polynomial regression unveiled an inverted U‐shaped relationship between FM extent and HRV indices. A decrease of HRV indices was associated with changes in FM extent, proving that in UW and OW subjects, the adaptive flexibility of autonomic cardiac function was reduced. These findings provide important clues to guide future studies addressed to determine how changes in adiposity and autonomic cardiac function may contribute to health risk.
Compared with Alzheimer's disease (AD), Parkinson's disease (PD) shows peculiar clinical manifestations related to vigilance (i.e., executive cognitive deficits and visual hallucinations) that may be ...reflected in resting-state electroencephalographic rhythms. To test this hypothesis, clinical and resting-state electroencephalographic rhythms in age-, sex-, and education-matched PD patients (N = 136) and Alzheimer's disease patients (AD, N = 85), and healthy older participants (Nold, N = 65), were available from an international archive. Electroencephalographic sources were estimated by eLORETA software. The results are as follows: (1) compared to the Nold participants, the AD and PD patients showed higher widespread delta source activities (PD > AD) and lower posterior alpha source activities (AD > PD); (2) the PD patients with the most pronounced motor deficits exhibited very low alpha source activities in widespread cortical regions; (3) the PD patients with the strongest cognitive deficits showed higher alpha source activities in widespread cortical regions; and (4) compared to the PD patients without visual hallucinations, those with visual hallucinations were characterized by higher posterior alpha sources activities. These results suggest that in PD patients resting in quiet wakefulness, abnormalities in cortical neural synchronization at alpha frequencies are differently related to cognitive, motor, and visual hallucinations. Interestingly, parallel PD neuropathological processes may have opposite effects on cortical neural synchronization mechanisms generating cortical alpha rhythms in quiet wakefulness.
•In Parkinson's disease patients, resting-state delta and alpha electroencephalographic source activities were abnormal.•Those abnormalities were differently related to cognitive, motor, and perceptual deficits.•Those source activities may reflect the effect of Parkinson's disease on cognitive, motor, and perceptual systems.
Highlights ► Symptomatic treatment options for Alzheimer’s disease (AD) are currently limited to two therapeutic classes namely, acetylcholinesterase inhibitors (AChEIs) and memantine. ► The present ...review clarifies the effects of AChEIs and memantine on resting-state electroencephalographic (EEG) rhythms and cognitive function in AD patients to identify EEG markers useful for drug development. ► Based on the field literature, the patient’s EEG rhythms most reactive to AChEIs are those at delta (0–3 Hz), theta (4–7 Hz) and alpha (8–12 Hz); the effects of memantine generate a reduction of pathological theta rhythms.
To evaluate the effect of a solo ultraendurance open-water swim on autonomic and nonautonomic control of heart rate (HR).
A male athlete (age 48 y, height 172 cm, body mass 68 kg, BMI 23 kg/m2) ...underwent HR-variability (HRV) and circulating catecholamine evaluations at different times before and after an ultraendurance swim crossing the Adriatic Sea from Italy to Albania. HRV was measured in 5-min segments and quantified by time and frequency domain. Circulating catecholamines were estimated by salivary alpha-amylase (sAA) assay.
The athlete completed 78.1 km in 23:44 h:min. After arrival, sAA levels had increased by 102.6%. Time- and frequency-domain HRV indexes decreased, as well (mean RR interval, -29,7%; standard deviation of normal mean RR interval, -63,1%; square root of mean squared successive differences between normal-to-normal RR intervals, -49.3%; total power, -74.3%; low frequency, -78.0%; high frequency, -76.4%), while HR increased by 41.8%. At 16-h recovery, sAA had returned to preevent values, while a stable tachycardia was accompanied by reduced HRV measures.
To the authors' knowledge, this is the first study reporting cardiac autonomic adjustments to an extreme and challenging ultraendurance open-water swim. The findings confirmed that the autonomic drives depend on exercise efforts. Since HRV changes did not mirror the catecholamine response 16 h postevent, the authors assume that the ultraendurance swim differently influenced cardiac function by both adaptive autonomic and nonautonomic patterns.
The aim of this study was to verify the hypothesis that transcranial magnetic stimulation (TMS) parameters over the hand region of the motor cortex, such as resting motor threshold (rMT) and motor ...evoked potential (MEP) latency, predict the behavioural performance of karate athletes in the response time (RT) test. Twenty-five male karate athletes (24.9 ± 4.9 years) and 25 matched non-athletes (26.2 ± 4.5 years) were recruited. Using TMS, we investigated cortico-spinal system excitability. Compared with controls, the athletes showed faster RT (
p
< 0.001), lower rMT (
p
< 0.01), shorter MEP latency (
p
< 0.01), and higher MEP amplitude (
p
< 0.01); moreover, there was a significant positive linear correlation between RT and rMT (
p
< 0.001), between RT and MEP latency (
p
< 0.0001), and a negative correlation between RT and MEP amplitude (
p
< 0.001). The practice of competitive sports affects both the central and peripheral nervous system. Subjects that showed higher cortical excitability showed also higher velocity, at which the neural signal is propagated from the motor cortex to the muscle and consequently better RT. The lower rMT and the shorter MEP latency observed in athletes support the effects of training in determining specific brain organizations to meet specific sport challenges.
We tested the hypothesis of a relationship between heart rate variability (HRV) and Rolandic mu rhythms in relaxed condition of resting state. Resting state eyes-closed electroencephalographic (EEG) ...and electrocardiographic (ECG) data were recorded (10–20 System) in 42 healthy adults. EEG rhythms of interest were high-frequency alpha (10.5–13Hz) and low-frequency beta (13–20Hz), which are supposed to form Rolandic mu rhythms. Rolandic and occipital (control) EEG sources were estimated by LORETA software. Results showed a statistically significant (p<0.05, corrected) negative correlation across all subjects between Rolandic cortical sources of low-frequency beta rhythms and the low-frequency band power (LF, 0.04–0.15Hz) of tachogram spectrum as an index of HRV. The lower the amplitude of Rolandic sources of low-frequency beta rhythms (as a putative sign of activity of somatomotor cortex), the higher the LF band power of tachogram spectrum (as a putative sign of sympathetic activity). This effect was specific as there was neither a similar correlation between these EEG rhythms and high-frequency band power of tachogram spectrum (as a putative sign of parasympathetic vagal activity) neither between occipital sources of low-frequency beta rhythms (as a putative sign of activity of visual cortex) and LF band power of tachogram spectrum. These results suggest that Rolandic low-frequency beta rhythms are related to sympathetic activity regulating heart rate, as a dynamic neurophysiologic oscillatory mechanism sub-serving the interaction between brain neural populations involved in somatomotor control and brain neural populations regulating ANS signals to heart for on-going homeostatic adaptations.
Abstract Occipital sources of resting-state electroencephalographic (EEG) alpha rhythms are abnormal, at the group level, in patients with amnesic mild cognitive impairment (MCI) and Alzheimer's ...disease (AD). Here, we evaluated the hypothesis that amplitude of these occipital sources is related to neurodegeneration in occipital lobe as measured by magnetic resonance imaging. Resting-state eyes-closed EEG rhythms were recorded in 45 healthy elderly (Nold), 100 MCI, and 90 AD subjects. Neurodegeneration of occipital lobe was indexed by weighted averages of gray matter density, estimated from structural MRIs. EEG rhythms of interest were alpha 1 (8–10.5 Hz) and alpha 2 (10.5–13 Hz). EEG cortical sources were estimated by low-resolution brain electromagnetic tomography. Results showed a positive correlation between occipital gray matter density and amplitude of occipital alpha 1 sources in Nold, MCI, and AD subjects as a whole group (r = 0.3, p = 0.000004, N = 235). Furthermore, there was a positive correlation between the amplitude of occipital alpha 1 sources and cognitive status as revealed by Mini Mental State Examination score across all subjects (r = 0.38, p = 0.000001, N = 235). Finally, amplitude of occipital alpha 1 sources allowed a moderate classification of individual Nold and AD subjects (sensitivity: 87.8%; specificity: 66.7%; area under the receiver operating characteristic curve: 0.81). These results suggest that the amplitude of occipital sources of resting-state alpha rhythms is related to AD neurodegeneration in occipital lobe along pathologic aging.
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