Role Of Functional Connectivity Research Articles

Estradiol associations with brain functional connectivity in postmenopausal women.

Previous studies have found that estrogens play a role in functional connectivity in the brain; however, little research has been done regarding how estradiol is associated with functional connectivity in postmenopausal women. The purpose of this study was to examine the relationship between estradiol and functional connectivity in postmenopausal women. Structural and blood oxygenation level-dependent resting-state magnetic resonance imaging scans of 88 cognitively healthy postmenopausal individuals were obtained along with blood samples collected the same day as the magnetic resonance imaging to assess hormone levels. We generated connectivity values in CONN toolbox version 20.b, an SPM-based software. A regression analysis was run using estradiol level and regions of interest (ROI), including the hippocampus, parahippocampus, dorsolateral prefrontal cortex, and precuneus. Estradiol level was found to enhance parahippocampal gyrus anterior division left functional connectivity during ROI-to-ROI regression analysis. Estradiol enhanced functional connectivity between the parahippocampal gyrus anterior division left and the precuneus as well as the parahippocampal gyrus anterior division left and parahippocampal gyrus posterior division right. An exploratory analysis showed that years since the final menstrual period was related to enhanced connectivity between regions within the frontoparietal network. These results illustrated the relationship between estradiol level and functional connectivity in postmenopausal women. They have implications for understanding how the functioning of the brain changes for individuals after menopause that may eventually lead to changes in cognition and behavior in older ages.

Reduced Cerebellar Brain Inhibition Measured Using Dual-Site TMS in Older Than in Younger Adults.

Dual-site transcranial magnetic stimulation (TMS) can be used to measure the cerebellar inhibitory influence on the primary motor cortex, known as cerebellar brain inhibition (CBI), which is thought to be important for motor control. The aim of this study was to determine whether age-related differences in CBI (measured at rest) were associated with an age-related decline in bilateral motor control measured using the Purdue Pegboard task, the Four Square Step Test, and a 10-m walk. In addition, we examined test re-test reliability of CBI measured using dual-site TMS with a figure-of-eight coil in two sessions. There were three novel findings. First, CBI was less in older than in younger adults, which is likely underpinned by an age-related loss of Purkinje cells. Second, greater CBI was associated with faster 10-m walking performance in older adults, but slower 10-m walking performance in younger adults. Third, moderate intraclass correlation coefficients (ICCs: 0.53) were found for CBI in younger adults; poor ICCs were found for CBI (ICC: 0.40) in older adults. Together, these results have important implications for the use of dual-site TMS to increase our understanding of age- and disease-related changes in cortical motor networks, and the role of functional connectivity in motor control.

Propagating patterns of intrinsic activity along macroscale gradients coordinate functional connections across the whole brain

The intrinsic activity of the human brain, observed with resting-state fMRI (rsfMRI) and functional connectivity, exhibits macroscale spatial organization such as functional networks and gradients. Dynamic analysis techniques have shown that functional connectivity is a mere summary of time-varying patterns with distinct spatial and temporal characteristics. A better understanding of these patterns might provide insight into aspects of the brain's intrinsic activity that cannot be inferred by functional connectivity or the spatial maps derived from it, such as functional networks and gradients. Here, we describe three spatiotemporal patterns of coordinated activity across the whole brain obtained by averaging similar ~20-second-long segments of rsfMRI timeseries. In each of these patterns, activity propagates along a particular macroscale functional gradient, simultaneously across the cerebral cortex and in most other brain regions. In some regions, like the thalamus, the propagation suggests previously-undescribed gradients. The coordinated activity across areas is consistent with known tract-based connections, and nuanced differences in the timing of peak activity between regions point to plausible driving mechanisms. The magnitude of correlation within and particularly between functional networks is remarkably diminished when these patterns are regressed from the rsfMRI timeseries, a quantitative demonstration of their significant role in functional connectivity. Taken together, our results suggest that a few recurring patterns of propagating intrinsic activity along macroscale gradients give rise to and coordinate functional connections across the whole brain.

Phase/Amplitude Synchronization of Brain Signals During Motor Imagery BCI Tasks.

In the last decade, functional connectivity (FC) has been increasingly adopted based on its ability to capture statistical dependencies between multivariate brain signals. However, the role of FC in the context of brain-computer interface applications is still poorly understood. To address this gap in knowledge, we considered a group of 20 healthy subjects during an EEG-based hand motor imagery (MI) task. We studied two well-established FC estimators, i.e. spectral- and imaginary-coherence, and we investigated how they were modulated by the MI task. We characterized the resulting FC networks by extracting the strength of connectivity of each EEG sensor and we compared the discriminant power with respect to standard power spectrum features. At the group level, results showed that while spectral-coherence based network features were increasing in the sensorimotor areas, those based on imaginary-coherence were significantly decreasing. We demonstrated that this opposite, but complementary, behavior was respectively determined by the increase in amplitude and phase synchronization between the brain signals. At the individual level, we eventually assessed the potential of these network connectivity features in a simple off-line classification scenario. Taken together, our results provide fresh insights into the oscillatory mechanisms subserving brain network changes during MI and offer new perspectives to improve BCI performance.

The Effects of the BAILAMOS Dance Program on Brain Functional Connectivity of Older Latinos: An Exploratory Study

Compared to non-Latinos whites, older Latinos are at higher risk of cognitive impairment and engage in less leisure-time physical activity (PA). Resting-state brain functional connectivity (FC) is a putative biomarker for age-related cognitive decline. PA plays a role in FC of brain networks associated with cognitive decline. Objective: Investigate the effects of the BAILAMOS™ dance program on FC in three brain networks associated with age-related cognitive decline (Default Mode [DMN], Frontoparietal [FPN], and Salience [SAL] networks). Methods: Single-group pre-post design. Ten cognitively intact older Latinos participated in the four-month (2x/week for 60min) BAILAMOS™ dance program with four Latin dance styles. MRI was obtained pre- and post-intervention. FC was analyzed using the resting-state fMRI toolbox (CONN) via pairwise BOLD signal correlations and then converted into z-scores. We performed dependent t-tests, computed Cohen’s d and 95%CI for p < 0.05. Results: Within-FPN FC significantly increased (t(9) = 2.35, p = 0.043, d = 0.70) from pre (M=0.49±0.15) to post-intervention (M=0.59±0.13). In the DMN, we observed moderate effect size changes in the ratio of the FC between-networks by the FC within-networks (Mdiff = 0.10; 95%CI = -0.01; 0.21, p = 0.08, d = 0.64). Conclusions: The BAILAMOS™ program increased within-FPN FC, which is a cognitive-control network related to adaptive control and flexibility. Moderate changes between- vs. within-DMN FC suggest BAILAMOS™ also increased whole-brain DMN integration. Taken together, results might signal that Latin dance can combat the disruption of FC between the DMN and other networks, and within-FPN, which are associated with cognitive decline.

Cerebello-basal ganglia connectivity fingerprints related to motor/cognitive performance in Parkinson's disease

IntroductionThe role of the cerebellum in Parkinson's disease (PD) has attracted increasing attention; however, the role of functional connectivity (FC) between the basal ganglia and particular cerebellar subregions remains to be elucidated. We aimed to clarify the FC and its contribution to motor and cognitive performances in patients with PD. MethodsWe included 99 patients with PD and 99 age- and sex-matched healthy controls in this study. We created a cerebellar functional parcellation by performing cerebellum-only independent component analysis. Using the functional parcellation map, we performed seed-based connectivity analysis using each region as a seed and extracted the mean correlation coefficients within the thalamus and basal ganglia, including the caudate, pallidum, putamen and subthalamic nucleus. We examined the group differences and correlations with the motor and general cognitive scores. In addition, we conducted a mediation analysis to clarify the relationship among FC, motor severity, and cognition. ResultsThe PD group showed decreased FC between a wide range of cerebellar subregions and the basal ganglia. Motor severity was correlated with FC between the subthalamic nucleus and posterior Crus I/II, and general cognitive performance scores correlated with FC between the caudate nucleus and medial-posterior part of the Crus I/II (p < 0.05, corrected for multiple comparisons). The cerebello-caudate network had a direct effect on cognitive performance (p = 9.0 × 10−3), although partially mediated by motor performance (p = 8.2 × 10−3). ConclusionFC between cerebellar Crus I/II and divergent basal ganglia related to motor and cognitive performance in PD.

Cortico-limbic functional connectivity mediates the effect of early life stress on suicidality in bipolar depressed 5-HTTLPR*s carriers

BackgroundIn bipolar disorder (BD) the risk of suicide in adult life can be influenced by the interaction of adverse childhood experiences with the serotonin transporter polymorphism (5-HTTLPR). The cortico-limbic connectivity is a candidate endophenotype for the disorder, also related to suicidality and affected by the 5-HT system. MethodsIn 64 (*s carriers = 41; l/l = 23) depressed BD patients, we explored the effect of 5-HTTLPR on corticolimbic functional connectivity (FC) during emotional processing, and the role of FC in moderating/mediating the effect of early stressful events on suicidality among 5-HTTLPR groups, by implementing Generalized Structural Equation Model. Results5-HTTLPR affects FC between amygdala (Amy) and anterior cingulate cortex (ACC), temporal pole, putamen/thalamus, and precuneus. The short allele was associated to a more inefficient corticolimbic connectivity. In 5-HTTLPR*s carriers, but not in l/l, the Amy-ACC functional coupling mediated the relationship between stress load and current suicidality. LimitationsPatients were not drug-naive, and the recruitment took place in a single center, thus raising the possibility of population stratifications. The sample size is relatively small, but our findings can provide the background for replication study in independent and larger datasets. ConclusionsOur results confirm the link between the 5-HTT promoter polymorphism and susceptibility to stress in BD, and suggest that cortico-limbic functional connectivity mediates these effects. This pattern could identify a vulnerability factor for the exacerbation of mood episodes after stressful life events particularly relevant in *s carriers.

Study on functional connectivity between the subgenual anterior cingulate cortes and limbic cortices in predicting the efficacy of early antidepressant treatment outcome

Objective To explore the role of functional connectivity(FC) between the subgenual anterior cingulate cortes(sgACC) and limbic cortices in predicting the efficacy of early antidepressant treatment. Methods Resting state magnetoencephalography(MEG) data were collected from 32 patients with major depressive disorder(MDD) and 20 matched healthy control subjects at baseline.According to whether the HAMD17 total score reduction rate reached 50% after 2 weeks, the patients were divided into responder group and non-responder group.The difference of the FC, the relationship between the FC and the change rate of HAMD17 were explored. Results Compared with controls, MDD patients showed decreased connectivity of the sgACC with the right hippocampus(MNI coordinate: x=30, y=-3, z=-24; F=5.11, P=0.028), the right amygdala(MNI coordinate: x=22, y=-2, z=-15; F=6.90, P=0.012) and the left amygdala(MNI coordinate: x=-24, y=-6, z=-16; F=5.75, P=0.020). Compared with non-responders, the connectivity of the sgACC with the right hippocampus(MNI coordinate: x=30, y=-3, z=-24; F=8.74, P=0.0065), the right amygdala(MNI coordinate: x=22, y=-2, z=-15; F=12.417, P=0.0016) were higher in responders.Pretreatment connectivity of the sgACC with the right hippocampus(r=-0.50, P=0.0066), the right amygdala(r=-0.56, P=0.0018) were negatively correlated with clinical improvement.ROC analyses confirmed the value of the connectivity of sgACC with the right hippocampus(area under curve(AUC)=0.71, P=0.042), the right amygdala(AUC=0.73, P=0.029) in classifying responders versus non-responders in 2 weeks of treatment. Conclusion The decreased FC of the sgACC with the right hippocampus and the right amygdala at baseline is associated with a better improvement, which can potentially serve as a treatment outcome biomarker in early curative effect of depression. Key words: Major depressive disorder; Theta wave; Curative effect; Magnetoencephalography; Functional connectivity

Repetitive Transcranial Magnetic Stimulation, Cognition, and Multiple Sclerosis: An Overview.

Multiple sclerosis (MS) affects cognition in the majority of patients. A major aspect of the disease is brain volume loss (BVL), present in all phases and types (relapsing and progressive) of the disease and linked to both motor and cognitive disabilities. Due to the lack of effective pharmacological treatments for cognition, cognitive rehabilitation and other nonpharmacological interventions such as repetitive transcranial magnetic stimulation (rTMS) have recently emerged and their potential role in functional connectivity is studied. With recently developed advanced neuroimaging and neurophysiological techniques, changes related to alterations of the brain's functional connectivity can be detected. In this overview, we focus on the brain's functional reorganization in MS, theoretical and practical aspects of rTMS utilization in humans, and its potential therapeutic role in treating cognitively impaired MS patients.

Intrinsic connectivity of hippocampal subfields in normal elderly and mild cognitive impairment patients.

Hippocampal connectivity has been widely described but connectivity specificities of hippocampal subfields and their changes in early AD are poorly known. The aim of this study was to highlight hippocampal subfield networks in healthy elderly (HE) and their changes in amnestic patients with mild cognitive impairment (aMCI). Thirty-six HE and 27 aMCI patients underwent resting-state functional MRI scans. Specific intrinsic connectivity of bilateral CA1, SUB (subiculum), and CA2/3/4/DG was identified in HE (using seeds derived from manually delineation on high-resolution scans) and compared between HE and aMCI. Compared to the other subfields, CA1 was more strongly connected to the amygdala and occipital regions, CA2/3/4/DG to the left anterior cingulate cortex, temporal, and occipital regions, and SUB to the angular, precuneus, putamen, posterior cingulate, and frontal regions. aMCI patients showed reduced connectivity within the SUB network (with frontal and posterior cingulate regions). Our study highlighted for the first time three specific and distinct hippocampal subfield functional networks in HE, and their alterations in aMCI. These findings are important to understand AD specificities in both cognitive deficits and lesion topography, given the role of functional connectivity in these processes. Hum Brain Mapp 38:4922-4932, 2017. © 2017 Wiley Periodicals, Inc.

Neurorehabilitation in Stroke: The Role of Functional Connectivity

Neurorehabilitation in Stroke: The Role of Functional Connectivity

Right anterior insula connectivity is important for cue‐induced craving in nicotine‐dependent smokers

The insula has been implicated in cue-induced craving and relapse in nicotine-dependent tobacco cigarette smokers. The aims of the present study were to identify brain regions that exhibit greater functional connectivity with the right anterior insula in response to smoking cues than to neutral cues and the role of functional connectivity between these regions in mediating cue-induced craving in healthy (free of axis I psychiatric disorders) nicotine-dependent tobacco cigarette smokers. Functional magnetic resonance imaging data were collected from 63 healthy nicotine-dependent smokers viewing blocks of smoking and neutral cues. Craving ratings were obtained after each block. A psychophysiologic interaction approach was used to identify regions that exhibited significantly greater functional connectivity with the right anterior insula (seed) during the smoking cues than during the neutral (corrected cluster thresholding, Z > 2.3, P = 0.05). Parameter estimates of the interaction effects from each region were regressed against the mean cue-induced craving scores. Significant task by seed interactions were observed in two clusters centered in the bilateral precuneus and left angular gyrus. The strength of connectivity between the right anterior insula and the precuneus, which is involved interoceptive processing and self-awareness, was positively correlated with the magnitude of the craving response to the smoking cues (r(2) = 0.15; P < 0.01). These data suggest that among smokers, cue-induced craving may be a function of connectivity between two regions involved in interoception and self-awareness. Moreover, treatment strategies that incorporate mindful attention may be effective in attenuating cue-induced craving and relapse in nicotine-dependent smokers.

Amygdala Inputs to the Ventral Hippocampus Bidirectionally Modulate Social Behavior

Impairments in social interaction represent a core symptom of a number of psychiatric disease states, including autism, schizophrenia, depression, and anxiety. Although the amygdala has long been linked to social interaction, little is known about the functional role of connections between the amygdala and downstream regions in noncompetitive social behavior. In the present study, we used optogenetic and pharmacological tools in mice to study the role of projections from the basolateral complex of the amygdala (BLA) to the ventral hippocampus (vHPC) in two social interaction tests: the resident-juvenile-intruder home-cage test and the three chamber sociability test. BLA pyramidal neurons were transduced using adeno-associated viral vectors (AAV5) carrying either channelrhodopsin-2 (ChR2) or halorhodopsin (NpHR), under the control of the CaMKIIα promoter to allow for optical excitation or inhibition of amygdala axon terminals. Optical fibers were chronically implanted to selectively manipulate BLA terminals in the vHPC. NpHR-mediated inhibition of BLA-vHPC projections significantly increased social interaction in the resident-juvenile intruder home-cage test as shown by increased intruder exploration. In contrast, ChR2-mediated activation of BLA-vHPC projections significantly reduced social behaviors as shown in the resident-juvenile intruder procedure as seen by decreased time exploring the intruder and in the three chamber sociability test by decreased time spent in the social zone. These results indicate that BLA inputs to the vHPC are capable of modulating social behaviors in a bidirectional manner.

The frontal laterality of emotion: a historical overview

The processing and experience of emotions in humans are complex phenomena that involve a brain circuitry of cortical and subcortical structures. Amongst the most successful cortical centred theories in affective and social neuroscience is the frontal asymmetry of emotion model. Early views on emotion in humans predominantly implicated the right hemisphere in the processing of emotions. In the late 1970s, evidence was provided that positive and negative affect was associated with patterns of left and right frontal brain activity, respectively. Building on motives of approach- and avoidance-related emotions, more recent electrophysiological studies have found support for left hemispheric involvement in the processing of the approach-related emotion anger. Finally, transcranial magnetic stimulation studies have added causal evidence for the lateralised involvement of the left prefrontal cortex in the approach-related emotion anger and the right prefrontal cortex in the avoidance-related emotion fear. Current research focuses on the role of functional connectivity between the hemispheres to further elucidate the neural underpinnings of emotion and emotional behaviour. (Netherlands Journal of Psychology, 64, 112-118.)