tDCS modulates behavioral performance and the neural oscillatory dynamics serving visual selective attention

Transcranial direct‐current stimulation (tDCS) is a noninvasive method for modulating human brain activity. Although there are several hypotheses about the net effects of tDCS on brain function, the field's understanding remains incomplete and this is especially true for neural oscillatory activity during cognitive task performance. In this study, we examined whether different polarities of occipital tDCS differentially alter flanker task performance and the underlying neural dynamics. To this end, 48 healthy adults underwent 20 min of anodal, cathodal, or sham occipital tDCS, and then completed a visual flanker task during high‐density magnetoencephalography (MEG). The resulting oscillatory responses were imaged in the time‐frequency domain using beamforming, and the effects of tDCS on task‐related oscillations and spontaneous neural activity were assessed. The results indicated that anodal tDCS of the occipital cortices inhibited flanker task performance as measured by reaction time, elevated spontaneous activity in the theta (4–7 Hz) and alpha (9–14 Hz) bands in prefrontal and occipital cortices, respectively, and reduced task‐related theta oscillatory activity in prefrontal cortices during task performance. Cathodal tDCS of the occipital cortices did not significantly affect behavior or any of these neuronal parameters in any brain region. Lastly, the power of theta oscillations in the prefrontal cortices was inversely correlated with reaction time. In conclusion, anodal tDCS modulated task‐related oscillations and spontaneous activity across multiple cortical areas, both near the electrode and in distant sites that were putatively connected to the targeted regions.     

Neuronal oscillations and functional interactions between resting state networks

Functional magnetic imaging (fMRI) studies showed that resting state activity in the healthy brain is organized into multiple large‐scale networks encompassing distant regions. A key finding of resting state fMRI studies is the anti‐correlation typically observed between the dorsal attention network (DAN) and the default mode network (DMN), which—during task performance—are activated and deactivated, respectively. Previous studies have suggested that alcohol administration modulates the balance of activation/deactivation in brain networks, as well as it induces significant changes in oscillatory activity measured by electroencephalography (EEG). However, our knowledge of alcohol‐induced changes in band‐limited EEG power and their potential link with the functional interactions between DAN and DMN is still very limited. Here we address this issue, examining the neuronal effects of alcohol administration during resting state by using simultaneous EEG‐fMRI. Our findings show increased EEG power in the theta frequency band (4–8 Hz) after administration of alcohol compared to placebo, which was prominent over the frontal cortex. More interestingly, increased frontal tonic EEG activity in this band was associated with greater anti‐correlation between the DAN and the frontal component of the DMN. Furthermore, EEG theta power and DAN‐DMN anti‐correlation were relatively greater in subjects who reported a feeling of euphoria after alcohol administration, which may result from a diminished inhibition exerted by the prefrontal cortex. Overall, our findings suggest that slow brain rhythms are responsible for dynamic functional interactions between brain networks. They also confirm the applicability and potential usefulness of EEG‐fMRI for central nervous system drug research. Hum Brain Mapp 35:3517–3528, 2014. © 2013 Wiley Periodicals, Inc .     

Prefrontal theta modulates sensorimotor gamma networks during the reorienting of attention

The ability to execute a motor plan involves spatiotemporally precise oscillatory activity in primary motor (M1) regions, in concert with recruitment of “higher order” attentional mechanisms for orienting toward current task goals. While current evidence implicates gamma oscillatory activity in M1 as central to the execution of a movement, far less is known about top‐down attentional modulation of this response. Herein, we utilized magnetoencephalography (MEG) during a Posner attention‐reorienting task to investigate top‐down modulation of M1 gamma responses by frontal attention networks in 63 healthy adult participants. MEG data were evaluated in the time–frequency domain and significant oscillatory responses were imaged using a beamformer. Robust increases in theta activity were found in bilateral inferior frontal gyri (IFG), with significantly stronger responses evident in trials that required attentional reorienting relative to those that did not. Additionally, strong gamma oscillations (60–80 Hz) were detected in M1 during movement execution, with similar responses elicited irrespective of attentional reorienting. Whole‐brain voxel‐wise correlations between validity difference scores (i.e., attention reorienting trials—nonreorienting trials) in frontal theta activity and movement‐locked gamma oscillations revealed a robust relationship in the contralateral sensorimotor cortex, supplementary motor area, and right cerebellum, suggesting modulation of these sensorimotor network gamma responses by attentional reorienting. Importantly, the validity difference effect in this distributed motor network was predictive of overall motor function measured outside the scanner and further, based on a mediation analysis this relationship was fully mediated by the reallocation response in the right IFG. These data are the first to characterize the top‐down modulation of movement‐related gamma responses during attentional reorienting and movement execution.     

Spontaneous oscillatory markers of cognitive status in two forms of dementia

Abnormal oscillatory brain activity in dementia may indicate incipient neuronal/synaptic dysfunction, rather than frank structural atrophy. Leveraging a potential link between the degree of abnormal oscillatory activity and cognitive symptom severity, one could localize brain regions in a diseased but pre‐atrophic state, which may be more amenable to interventions. In the current study, we evaluated the relationships among cognitive deficits, regional volumetric changes, and resting‐state magnetoencephalography abnormalities in patients with mild cognitive impairment (MCI; N = 10; age: 75.9 ± 7.3) or primary progressive aphasia (PPA; N = 12; 69.7 ± 8.0), and compared them to normal aging [young (N = 18; 24.6 ± 3.5), older controls (N = 24; 67.2 ± 9.7]. Whole‐brain source‐level resting‐state estimates of relative oscillatory power in the delta (1–4 Hz), theta (4–7 Hz), alpha (8–12 Hz), and beta (15–30 Hz) bands were combined with gray matter volumes and cognitive scores to examine between‐group differences and brain–behavior correlations. Language and executive function (EF) abilities were impaired in patients with PPA, while episodic memory was impaired in MCI. Widespread oscillatory speeding and volumetric shrinkage was associated with normal aging, whereas the trajectory in PPA indicated widespread oscillatory slowing with additional volumetric reductions. Increases in delta and decreases in alpha power uniquely predicted group membership to PPA. Beyond volumetric reductions, more delta predicted poorer memory. In patients with MCI, no consistent group difference among oscillatory measures was found. The contributions of delta/alpha power on memory abilities were larger than volumetric differences. Spontaneous oscillatory abnormalities in association with cognitive symptom severity can serve as a marker of neuronal dysfunction in dementia, providing targets for promising treatments.     

Magnetoencephalographic gamma power reduction in patients with schizophrenia during resting condition

Objective: The “default network” represents a baseline condition of brain function and is of interest in schizophrenia research because its component brain regions are believed to be aberrant in the disorder. We hypothesized that magnetoencephalographic (MEG) source localization analysis would reveal abnormal resting activity within particular frequency bands in schizophrenia. Experimental Design: Eyes‐closed resting state MEG signals were collected for two comparison groups. Patients with schizophrenia (N = 38) were age‐gender matched with healthy control subjects (N = 38), and with a group of unmedicated unaffected siblings of patients with schizophrenia (N = 38). To localize 3D‐brain regional differences, synthetic aperture magnetometry was calculated across established frequency bands as follows: delta (0.9–4 Hz), theta (4–8 Hz), alpha (8–14 Hz), beta (14–30 Hz), gamma (30–80 Hz), and super‐gamma (80–150 Hz). Principle Observations: Patients with schizophrenia showed significantly reduced activation in the gamma frequency band in the posterior region of the medial parietal cortex. As a group, unaffected siblings of schizophrenia patients also showed significantly reduced activation in the gamma bandwidth across similar brain regions. Moreover, using the significant region for the patients and examining the gamma band power gave an odds ratio of 6:1 for reductions of two standard deviations from the mean. This suggests that the measure might be the basis of an intermediate phenotype. Conclusions: MEG resting state analysis adds to the evidence that schizophrenic patients experience this condition very differently than healthy controls. Whether this baseline difference relates to network abnormalities remains to be seen. Hum Brain Mapp, 2009. © 2009 Wiley‐Liss, Inc.     

Core dysfunction in schizophrenia: electrophysiology trait biomarkers

Koychev I, El‐Deredy W, Mukherjee T, Haenschel C, Deakin JFW. Core dysfunction in schizophrenia: electrophysiology trait biomarkers. Objective: Core symptoms of schizophrenia, particularly in the cognitive domain are hypothesized to be due to an abnormality in neural connectivity. Biomarkers of connectivity may therefore be a promising tool in exploring the aetiology of schizophrenia. We used electrophysiological methods to demonstrate abnormal visual information processing during in patients performing a simple cognitive task. Method: Electrophysiological recordings were acquired from 20 chronically ill, medicated patients diagnosed with either schizophrenia or schizo‐affective disorder and 20 healthy volunteers while they conducted a working memory (WM) task. Results: The patient group had significantly lower accuracy on the WM task and a trend for slower responses. An early visual evoked response potential was reduced in patients. Analysis of the electroencephalographic oscillations showed a decreased phase‐locking factor (in the theta, beta and gamma bands) and signal power (theta frequency band). The beta and gamma oscillatory abnormalities were confined to two sets of correlated fronto and occipital electrodes. Conclusion: The findings of event‐related potential and oscillatory abnormalities in patients with schizophrenia confirm the sensitivity of early visual information processing measurements for identification of schizophrenia phenotype. The fronto‐occipital distribution of the oscillatory abnormalities replicates our findings from a schizotypal sample and implicates a possible top‐down dysfunction as a vulnerability trait.     

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.     

Resting state oscillatory brain dynamics in Parkinson's disease: an MEG study.

OBJECTIVE: The pathophysiological mechanisms of cognitive dysfunction and dementia in Parkinson's disease (PD) are still poorly understood. Altered resting state oscillatory brain activity may reflect underlying neuropathological changes. The present study using magneto encephalography (MEG) was set up to study differences in the pattern of resting state oscillatory brain activity in groups of demented and non-demented PD patients and healthy, elderly controls. METHODS: The pattern of MEG background oscillatory activity was studied in 13 demented PD patients, 13 non-demented PD patients and 13 healthy controls. Whole head MEG recordings were obtained in the morning in an eyes closed and an eyes open, resting state condition. Relative spectral power was calculated using Fast Fourier Transformation in delta, theta, alpha, beta and gamma frequency bands. RESULTS: In the non-demented PD patients, relative theta power was diffusely increased and beta power concomitantly decreased relative to controls. gamma Power was decreased in central and parietal channels. In the demented PD patients, a diffuse increase in relative delta and to lesser extent theta power and a decrease in relative alpha, beta and to lesser extent gamma power were found in comparison to the non-demented PD group. In addition, reactivity to eye opening was much reduced in the demented PD group. CONCLUSIONS: Parkinson's disease is characterized by a slowing of resting state brain activity involving theta, beta and gamma frequency bands. Dementia in PD is associated with a further slowing of resting state brain activity, additionally involving delta and alpha bands, as well as a reduction in reactivity to eye-opening. SIGNIFICANCE: The differential patterns of slowing of resting state brain activity in demented and non-demented PD patients suggests that, in conjunction with a progression of the pathological changes already present in non-demented patients, additional mechanisms are involved in the development of dementia in PD.     

Genetic and disorder-specific aspects of resting state EEG abnormalities in schizophrenia

We evaluated whether abnormal frequency composition of the resting state electroencephalogram (EEG) in schizophrenia was associated with genetic liability for the disorder by studying first-degree biological relatives of schizophrenia patients. The study included a data-driven method for defining EEG frequency components and determined the specificity of resting state EEG frequency abnormalities by assessing schizophrenia patients, bipolar disorder patients, and relatives of both patient groups. Schizophrenia patients and their relatives, but not bipolar patients or their relatives, exhibited increased high-frequency activity (beta) providing evidence for disturbances in resting state brain activity being specific to genetic liability for schizophrenia. Schizophrenia patients exhibited augmented low-frequency EEG activity (delta, theta), while bipolar disorder patients and the 2 groups of relatives generally failed to manifest similar low-frequency EEG abnormalities. The Val(158)Met polymorphism for the catechol-O-methyl transferase (COMT) gene was most strongly associated with delta and theta activity in schizophrenia patients. Met homozygote schizophrenia patients exhibited augmented activity for the 2 low-frequency bands compared with control subjects. Excessive high-frequency EEG activity over frontal brain regions may serve as an endophenotype that reflects cortical expression of genetic vulnerability for schizophrenia. Low-frequency resting state EEG anomalies in schizophrenia may relate to disorder-specific pathophysiology in schizophrenia and the influence of the COMT gene on tonic dopamanergic function.     

Frequency‐specific alternations in the amplitude of low‐frequency fluctuations in schizophrenia

Schizophrenia has been associated with abnormal task‐related brain activation in sensory and motor regions as well as social cognition network. Recently, two studies investigated temporal correlation between resting‐state functional magnetic resonance imaging (R‐fMRI) low‐frequency oscillations (LFOs) in schizophrenia but reported mixed results. This may be due to the different frequency bands used in these studies. Here we utilized R‐fMRI to measure the amplitude of low‐frequency fluctuations (ALFF) and fractional ALFF (fALFF) in three different frequency bands (slow‐5: 0.01–0.027 Hz; slow‐4: 0.027–0.08 Hz; and typical band: 0.01–0.08 Hz) in 69 patients with schizophrenia and 62 healthy controls. We showed that there were significant differences in ALFF/fALFF between the two bands (slow‐5 and slow‐4) in regions including basal ganglia, midbrain, and ventromedial prefrontal cortex. Importantly, we also identified significant interaction between frequency bands and groups in inferior occipital gyrus, precunus, and thalamus. The results suggest that the abnormalities of LFOs in schizophrenia is dependent on the frequency band and suggest that future studies should take the different frequency bands into account when measure intrinsic brain activity. Hum Brain Mapp 35:627–637, 2014. © 2012 Wiley Periodicals, Inc.     

On the relevance of EEG resting theta activity for the neurophysiological dynamics underlying motor inhibitory control

The modulation of theta frequency activity plays a major role in inhibitory control processes. However, the relevance of resting theta band activity and of the ability to spontaneously modulate this resting theta activity for neural mechanisms underlying inhibitory control is elusive. Various theoretical conceptions suggest to take these aspects into consideration. In the current study, we examine whether the strength of resting theta band activity or the ability to modulate the resting state theta activity affects response inhibition. We combined EEG‐time frequency decomposition and beamforming in a conflict‐modulated Go/Nogo task. A sample of N = 66 healthy subjects was investigated. We show that the strength of resting state theta activity modulates the effects of conflicts during motor inhibitory control. Especially when resting theta activity was low, conflicts strongly affected response inhibition performance and total theta band activity during Nogo trials. These effects were associated with theta‐related activity differences in the superior (BA7) and inferior parietal cortex (BA40). The results were very specific for total theta band activity since evoked theta activity and measures of intertrial phase coherency (phase‐locking factor) were not affected. The data suggest that the strength of resting state theta activity modulates processing of a theta‐related alarm or surprise signal during inhibitory control. The ability to voluntarily modulate theta band activity did not affect conflict‐modulated inhibitory control. These findings have important implications for approaches aiming to optimize human cognitive control.     

Dissociation of sustained attention from central executive functions: local activity and interregional connectivity in the theta range

Human brain oscillatory activity was analysed in the electroencephalographic theta frequency range (4-7 Hz) while subjects executed complex sequential finger movements with varying task difficulty and memory load. Local frontal-midline theta activity was associated with the general level of cognitive demand, with the highest amplitudes in the most demanding condition. Using low-resolution electromagnetic tomography analysis (LORETA), this theta activity was localized in the anterior cingulate gyrus including the cingulate motor area. These results suggest that local theta activity in the anterior cingulate gyrus represents correlates of an attentional system that allocate cognitive resources. In addition, interregional connectivity in the theta frequency range was modulated by memory-related executive functions independently of task difficulty. Connectivity analyses revealed a more distributed long-range network including frontal and parietal cortices during execution of novel compared with well-trained finger movement sequences. Thus, these results are compatible with a model in which theta long-range coupling indicates integration of sensory information into executive control components of complex motor behaviour.     

Distinction between perceptual and attentional processing in working memory tasks: a study of phase-locked and induced oscillatory brain dynamics

Working memory involves the short-term storage and manipulation of information necessary for cognitive performance, including comprehension, learning, reasoning and planning. Although electroencephalogram (EEG) rhythms are modulated during working memory, the temporal relationship of EEG oscillations with the eliciting event has not been well studied. In particular, the dynamics of the neural network supporting memory processes may be best captured in induced oscillations, characterized by a loose temporal link with the stimulus. In order to differentiate induced from evoked functional processes, the present study proposes a time-frequency analysis of the 3 to 30 Hz EEG oscillatory activity in a verbal n-back working memory paradigm. Control tasks were designed to identify oscillatory activity related to stimulus presentation (passive task) and focused attention to the stimulus (detection task). Evoked theta activity (4-8 Hz) phase-locked to the visual stimulus was evidenced in the parieto-occipital region for all tasks. In parallel, induced theta activity was recorded in the frontal region for detection and n-back memory tasks, but not for the passive task, suggesting its dependency on focused attention to the stimulus. Sustained induced oscillatory activity was identified in relation to working memory in the theta and beta (15-25 Hz) frequency bands, larger for the highest memory load. Its late occurrence limited to nonmatched items suggests that it could be related to item retention and active maintenance for further task requirements. Induced theta and beta activities displayed respectively a frontal and parietal topographical distribution, providing further functional information on the fronto-posterior network supporting working memory.     

Chemotherapy disrupts learning,neurogenesis and theta activity in the adult brain

Chemotherapy, especially if prolonged, disrupts attention, working memory and speed of processing in humans. Most cancer drugs that cross the blood–brain barrier also decrease adult neurogenesis. Because new neurons are generated in the hippocampus, this decrease may contribute to the deficits in working memory and related thought processes. The neurophysiological mechanisms that underlie these deficits are generally unknown. A possible mediator is hippocampal oscillatory activity within the theta range (3–12 Hz). Theta activity predicts and promotes efficient learning in healthy animals and humans. Here, we hypothesised that chemotherapy disrupts learning via decreases in hippocampal adult neurogenesis and theta activity. Temozolomide was administered to adult male Sprague–Dawley rats in a cyclic manner for several weeks. Treatment was followed by training with different types of eyeblink classical conditioning, a form of associative learning. Chemotherapy reduced both neurogenesis and endogenous theta activity, as well as disrupted learning and related theta‐band responses to the conditioned stimulus. The detrimental effects of temozolomide only occurred after several weeks of treatment, and only on a task that requires the association of events across a temporal gap and not during training with temporally overlapping stimuli. Chemotherapy did not disrupt the memory for previously learned associations, a memory independent of (new neurons in) the hippocampus. In conclusion, prolonged systemic chemotherapy is associated with a decrease in hippocampal adult neurogenesis and theta activity that may explain the selective deficits in processes of learning that describe the ‘chemobrain’.     

Predicting effective connectivity from resting‐state networks in healthy elderly and patients with prodromal Alzheimer's disease

Using functional neuroimaging techniques two aspects of functional integration in the human brain have been investigated, functional connectivity and effective connectivity. In this study we examined both connectivity types in parallel within an executive attention network during rest and while performing an attention task. We analyzed the predictive value of resting‐state functional connectivity on task‐induced effective connectivity in patients with prodromal Alzheimer's disease (AD) and healthy elderly. We found that in healthy elderly, functional connectivity was a significant predictor for effective connectivity, however, it was frequency‐specific. Effective top‐down connectivity emerging from prefrontal areas was related with higher frequencies of functional connectivity (e.g., 0.08–0.15 Hz), in contrast to effective bottom‐up connectivity going to prefrontal areas, which was related to lower frequencies of functional connectivity (e.g., 0.001–0.03 Hz). In patients, the prediction of effective connectivity by functional connectivity was disturbed. We conclude that functional connectivity and effective connectivity are interrelated in healthy brains but this relationship is aberrant in very early AD. Hum Brain Mapp 35:954–963, 2014. © 2013 Wiley Periodicals, Inc.     

Abnormal neural oscillations in clinical high risk for psychosis: a magnetoencephalography method study

BackgroundNeural oscillations directly reflect the rhythmic changes of brain activities during the resting state or while performing specific tasks. Abnormal neural oscillations have been discovered in patients with schizophrenia. However, there is limited evidence available on abnormal spontaneous neural oscillations in clinical high risk for psychosis (CHR-P). The brain signals recorded by the magnetoencephalography (MEG) technique are not to be disrupted by the skull and scalp.MethodsIn this study, we applied the MEG technique to record the resting-state neural activities in CHR-P. This was followed by a detailed MEG analysis method including three steps: (1) preprocessing, which was band-pass filtering based on the 0.5–60 Hz frequency range, removal of 50 Hz power frequency interference, and removal of electrocardiography (ECG) and electrooculography (EOG) artefacts by independent component analysis; (2) time-frequency analysis, a multitaper time-frequency transformation based on the Hanning window, and (3) source localisation, an exact low-resolution brain electromagnetic tomography. The method was verified by comparing a participant with CHR-P with a healthy control during the MEG recordings with an eyes-closed resting state.ResultsExperimental results show that the neural oscillations in CHR-P were significantly abnormal in the theta frequency band (4–7 Hz) and the delta frequency band (1–3 Hz). Also, relevant brain regions were located in the left occipital lobe and left temporo-occipital junction for the theta band and in the right dorsolateral prefrontal lobe and near orbitofrontal gyrus for the delta band.ConclusionsAbnormal neural oscillations based on specific frequency bands and corresponding brain sources may become biomarkers for high-risk groups. Further work will validate these characteristics in CHR-P cohorts.     

Test‐retest reliability of resting‐state magnetoencephalography power in sensor and source space

Several studies have reported changes in spontaneous brain rhythms that could be used as clinical biomarkers or in the evaluation of neuropsychological and drug treatments in longitudinal studies using magnetoencephalography (MEG). There is an increasing necessity to use these measures in early diagnosis and pathology progression; however, there is a lack of studies addressing how reliable they are. Here, we provide the first test‐retest reliability estimate of MEG power in resting‐state at sensor and source space. In this study, we recorded 3 sessions of resting‐state MEG activity from 24 healthy subjects with an interval of a week between each session. Power values were estimated at sensor and source space with beamforming for classical frequency bands: delta (2–4 Hz), theta (4–8 Hz), alpha (8–13 Hz), low beta (13–20 Hz), high beta (20–30 Hz), and gamma (30–45 Hz). Then, test‐retest reliability was evaluated using the intraclass correlation coefficient (ICC). We also evaluated the relation between source power and the within‐subject variability. In general, ICC of theta, alpha, and low beta power was fairly high (ICC > 0.6) while in delta and gamma power was lower. In source space, fronto‐posterior alpha, frontal beta, and medial temporal theta showed the most reliable profiles. Signal‐to‐noise ratio could be partially responsible for reliability as low signal intensity resulted in high within‐subject variability, but also the inherent nature of some brain rhythms in resting‐state might be driving these reliability patterns. In conclusion, our results described the reliability of MEG power estimates in each frequency band, which could be considered in disease characterization or clinical trials. Hum Brain Mapp 37:179–190, 2016. © 2015 Wiley Periodicals, Inc.     

A controlled clinical crossover trial of exercise training to improve cognition and neural communication in pediatric brain tumor survivors

ObjectiveTo assess the efficacy of aerobic exercise training to improve controlled attention, information processing speed and neural communication during increasing task load and rest in pediatric brain tumor survivors (PBTS) treated with cranial radiation. Methods: Participants completed visual-motor Go and Go/No-Go tasks during magnetoencephalography recording prior to and following the completion of 12-weeks of exercise training. Exercise-related changes in response accuracy and visual-motor latency were evaluated with Linear Mixed models. The Phase Lag Index (PLI) was used to estimate functional connectivity during task performance and rest. Changes in PLI values after exercise training were assessed using Partial Least Squares analysis. Results: Exercise training predicted sustained (12-weeks) improvement in response accuracy (p<0.05) during No-Go trials. Altered functional connectivity was detected in theta (4–7Hz) alpha (8–12Hz) and high gamma (60–100Hz) frequency bands (p<0.001) during Go and Go/No-Go trials. Significant changes in response latency and resting state connectivity were not detected. Conclusion: These findings support the efficacy of aerobic exercise to improve controlled attention and enhance functional mechanisms under increasing task load in participants. Significance: It may be possible to harness the beneficial effects of exercise as therapy to promote cognitive recovery and enhance brain function in PBTS.     

Spectral signatures of mirror movements in the sensori‐motor connectivity in kallmann syndrome

Mirror movements (MM) might be observed in congenital and acquired neurodegenerative conditions but their anatomic‐functional underpinnings are still largely elusive. This study investigated the spectral changes of resting‐state functional connectivity in Kallmann Syndrome (hypogonadotropic hypogonadism with hypo/anosmia with or without congenital MM) searching for insights into the phenomenon of MM. Forty‐four Kallmann syndrome patients (21 with MM) and 24 healthy control subjects underwent task (finger tapping) and resting‐state functional MRI. The spatial pattern of task‐related activations was used to mask regions and select putative motor networks in a spatially independent component analysis of resting‐state signals. For each resting‐state independent component time‐course power spectrum, we extracted the relative contribution of four separate bands: slow‐5 (0.01–0.027 Hz), slow‐4 (0.027–0.073 Hz), slow‐3 (0.073–0.198 Hz), slow‐2 (0.198–0.25 Hz), and analyzed the variance between groups. For the sensorimotor network, the analysis revealed a significant group by frequency interaction (P = 0.002) pointing to a frequency shift in the spectral content among subgroups with lower slow‐5 band and higher slow‐3 band contribution in Kallmann patients with MM versus controls (P = 0.028) and with lower slow‐5 band contribution between patients with and without MM (P = 0.057). In specific regions, as obtained from hand motor activation task analysis, spectral analyses demonstrated a lower slow‐5 band contribution in Kallmann patients with MM versus both controls and patients without MM (P < 0.05). In Kallmann syndrome, the peculiar phenomenon of bimanual synkinesis is associated at rest with regionally and spectrally selective functional connectivity changes pointing to a distinctive cortical and subcortical functional reorganization. Hum Brain Mapp 39:42–53, 2018. © 2017 Wiley Periodicals, Inc.     

Functional connectivity of cortical motor areas in the resting state in Parkinson's disease

Parkinson's disease (PD) patients have difficulty in initiating movements. Previous studies have suggested that the abnormal brain activity may happen not only during performance of self‐initiated movements but also in the before movement (baseline or resting) state. In the current study, we investigated the functional connectivity of brain networks in the resting state in PD. We chose the rostral supplementary motor area (pre‐SMA) and bilateral primary motor cortex (M1) as “seed” regions, because the pre‐SMA is important in motor preparation, whereas the M1 is critical in motor execution. FMRIs were acquired in 18 patients and 18 matched controls. We found that in the resting state, the pattern of connectivity with both the pre‐SMA or the M1 was changed in PD. Connectivity with the pre‐SMA in patients with PD compared to normal subjects was increased connectivity to the right M1 and decreased to the left putamen, right insula, right premotor cortex, and left inferior parietal lobule. We only found stronger connectivity in the M1 with its own local region in patients with PD compared to controls. Our findings demonstrate that the interactions of brain networks are abnormal in PD in the resting state. There are more connectivity changes of networks related to motor preparation and initiation than to networks of motor execution in PD. We postulate that these disrupted connections indicate a lack of readiness for movement and may be partly responsible for difficulty in initiating movements in PD. Hum Brain Mapp, 2010. © 2010 Wiley‐Liss, Inc.