The directionality and functional organization of frontoparietal connectivity during consciousness and anesthesia in humans

Frontoparietal connectivity has been suggested to be important in conscious processing and its interruption is thought to be one mechanism of general anesthesia. Data in animals demonstrate that feedforward processing of information may persist during the anesthetized state, while feedback processing is inhibited. We investigated the directionality and functional organization of frontoparietal connectivity in 10 human subjects anesthetized with propofol on two separate occasions. Multichannel electroencephalography and a computational method of assessing directed functional connectivity were employed. We demonstrate that directed feedback connectivity is diminished with loss of consciousness and returns with responsiveness to verbal command. We also applied the Dendrogram classification method to assess the global organization of directed functional connectivity during consciousness and anesthesia. We demonstrate a state-specific hierarchy and subject-specific subhierarchy in functional organization. These data support the hypothesis that specific states of human consciousness are defined by specific states of frontoparietal connectivity.     

Strength of default mode resting-state connectivity relates to white matter integrity in children

A default mode network of brain regions is known to demonstrate coordinated activity during the resting state. While the default mode network is well characterized in adults, few investigations have focused upon its development. We scanned 9-13-year-old children with diffusion tensor imaging and resting-state functional magnetic resonance imaging. We identified resting-state networks using Independent Component Analysis and tested whether the functional connectivity between the medial prefrontal cortex (mPFC) and posterior cingulate cortex (PCC) depends upon the maturation of the underlying cingulum white matter tract. To determine the generalizability of this relationship, we also tested whether functional connectivity depends on white matter maturity between bilateral lateral prefrontal cortex (lateral PFC) within the executive control network. We found a positive relationship between mPFC-PCC connectivity and fractional anisotropy of the cingulum bundle; this positive relationship was moderated by the age of the subjects such that it was stronger in older children. By contrast, no such structure-function relationship emerged between right and left lateral PFC. However, functional and structural connectivity of this tract related positively with cognitive speed, fluency, and set-switching neuropsychological measures.     

Psychopathic traits associated with abnormal hemodynamic activity in salience and default mode networks during auditory oddball task

Psychopathy is a personality disorder accompanied by abnormalities in emotional processing and attention. Recent theoretical applications of network-based models of cognition have been used to explain the diverse range of abnormalities apparent in psychopathy. Still, the physiological basis for these abnormalities is not well understood. A significant body of work has examined psychopathy-related abnormalities in simple attention-based tasks, but these studies have largely been performed using electrocortical measures, such as event-related potentials (ERPs), and they often have been carried out among individuals with low levels of psychopathic traits. In this study, we examined neural activity during an auditory oddball task using functional magnetic resonance imaging (fMRI) during a simple auditory target detection (oddball) task among 168 incarcerated adult males, with psychopathic traits assessed via the Hare Psychopathy Checklist-Revised (PCL-R). Event-related contrasts demonstrated that the largest psychopathy-related effects were apparent between the frequent standard stimulus condition and a task-off, implicit baseline. Negative correlations with interpersonal-affective dimensions (Factor 1) of the PCL-R were apparent in regions comprising default mode and salience networks. These findings support models of psychopathy describing impaired integration across functional networks. They additionally corroborate reports which have implicated failures of efficient transition between default mode and task-positive networks. Finally, they demonstrate a neurophysiological basis for abnormal mobilization of attention and reduced engagement with stimuli that have little motivational significance among those with high psychopathic traits.     

Combined functional and causal connectivity analyses of language networks in children: a feasibility study

Instead of assessing activation in distinct brain regions, approaches to investigating the networks underlying distinct brain functions have come into the focus of neuroscience research. Here, we provide a completely data-driven framework for assessing functional and causal connectivity in functional magnetic resonance imaging (fMRI) data, employing Granger's causality. We investigate the networks underlying story processing in 17 healthy children (8f, 9m, 10.4+/-2.8 years, 6.5-15.4 years). Extensive functional connectivity exists between brain regions, including some not detected in standard random effects analyses. Causal connectivity analyses demonstrate a clear dominance of left-sided language regions for both forward and backward interactions with other network nodes. We believe our approach to be useful in helping to assess language networks in the normal or pathological setting; it may also aid in providing better starting estimates for the more hypothesis-driven approaches like structural equation or dynamic causal modeling.     

Trait lasting alteration of the brain default mode network in experienced meditators and the experiential selfhood

Based on the finding in novices that four months of meditation training significantly increases frontal default mode network (DMN) module/subnet synchrony while decreasing left and right posterior DMN modules synchrony, the current study tested the prediction whether experienced meditators (those who are practising meditation intensively for several years) had a change in the DMN “trinity” of modules as a baseline trait characteristic and whether this change is in a similar direction as in the novice trainees who practised meditation for only four months. Comparison of functional connectivity within DMN subnets (measured by electroencephalogram operational synchrony in the three separate DMN modules) between five experienced meditators and 10 naïve participants (who were about to start the meditation training) fully support the prediction. Interpretation that links such DMN subnets changes to the three-dimensional components of the experiential selfhood was proposed.     

Predictive models for understanding body dissatisfaction among young males and females in China

The present study was designed to develop predictive models for understanding body dissatisfaction among young males and females (N=1377) in China. Six factors were assessed, including body mass index (BMI), perception of teasing, social pressure to be thin, appearance comparison, thin-ideal internalization and perceived social support. Variables were examined respectively for males and females. One SEM model, which had good fit indices, was developed for each gender. For both genders, BMI exerted its influence on body image directly and indirectly through perception of teasing. Two sources of sociocultural influence, perception of teasing and social pressure to be thin, also directly predicted body dissatisfaction. Gender differences were found in the relation between mediational mechanisms (social comparison and thin-ideal internalization) and body dissatisfaction. For females but not males, social comparison and internalization acted as weak but significant mediators between sociocultural influence and body image concerns. Implications and limitations are discussed.     

Long-term meditation training induced changes in the operational synchrony of default mode network modules during a resting state

Using theoretical analysis of self-consciousness concept and experimental evidence on the brain default mode network (DMN) that constitutes the neural signature of self-referential processes, we hypothesized that the anterior and posterior subnets comprising the DMN should show differences in their integrity as a function of meditation training. Functional connectivity within DMN and its subnets (measured by operational synchrony) has been measured in ten novice meditators using an electroencephalogram (EEG) recording in a pre-/post-meditation intervention design. We have found that while the whole DMN was clearly suppressed, different subnets of DMN responded differently after 4 months of meditation training: The strength of EEG operational synchrony in the right and left posterior modules of the DMN decreased in resting post-meditation condition compared to a pre-meditation condition, whereas the frontal DMN module on the contrary exhibited an increase in the strength of EEG operational synchrony. These findings combined with published data on functional–anatomic heterogeneity within the DMN and on trait subjective experiences commonly found following meditation allow us to propose that the first-person perspective and the sense of agency (the witnessing observer) are presented by the frontal DMN module, while the posterior modules of the DMN are generally responsible for the experience of the continuity of ‘I’ as embodied and localized within bodily space. Significance of these findings is discussed.     

Functional cortical connectivity analysis of mental fatigue unmasks hemispheric asymmetry and changes in small-world networks

Changes in functional connectivity across mental states can provide richer information about human cognition than simpler univariate approaches. Here, we applied a graph theoretical approach to analyze such changes in the lower alpha (8–10 Hz) band of EEG data from 26 subjects undergoing a mentally-demanding test of sustained attention: the Psychomotor Vigilance Test. Behavior and connectivity maps were compared between the first and last 5 min of the task. Reaction times were significantly slower in the final minutes of the task, showing a clear time-on-task effect. A significant increase was observed in weighted characteristic path length, a measure of the efficiency of information transfer within the cortical network. This increase was correlated with reaction time change. Functional connectivity patterns were also estimated on the cortical surface via source localization of cortical activities in 26 predefined regions of interest. Increased characteristic path length was revealed, providing further support for the presence of a reshaped global topology in cortical connectivity networks under fatigue state. Additional analysis showed an asymmetrical pattern of connectivity (right > left) in fronto-parietal regions associated with sustained attention, supporting the right-lateralization of this function. Interestingly, in the fatigue state, significance decreases were observed in left, but not right fronto-parietal connectivity. Our results indicate that functional network organization can change over relatively short time scales with mental fatigue, and that decreased connectivity has a meaningful relationship with individual difference in behavior and performance.     

Effect of functional and effective brain connectivity in identifying vowels from articulation imagery procedures

Cognitive Processing - Articulation imagery, a form of mental imagery, refers to the activity of imagining or speaking to oneself mentally without an articulation movement. It is an effective...     

Intelligence and neural efficiency: Measures of brain activation versus measures of functional connectivity in the brain

The neural efficiency hypothesis of intelligence suggests a more efficient use of the cortex (or even the brain) in brighter as compared to less intelligent individuals. This has been shown in a series of studies employing different neurophysiological measurement methods and a broad range of different cognitive task demands. However, most of the studies dealing with the brain–IQ relationship used parameters of absolute or relative brain activation such as the event-related (de-)synchronization of EEG alpha activity, allowing for interpretations in terms of more or less brain activation when individuals are confronted with cognitively demanding tasks. In order to investigate the neural efficiency hypothesis more thoroughly, we also used measures that inform us about functional connectivity between different brain areas (or functional coupling, respectively) when engaged in cognitive task performance. Analyses reveal evidence that higher intelligence is associated with a lower brain activation (or a lower ERD, respectively) and a stronger phase locking between short-distant regions of the frontal cortex.     

Task-related functional connectivity of the caudate mediates the association between trait mindfulness and implicit learning in older adults

Accumulating evidence shows a positive relationship between mindfulness and explicit cognitive functioning, i.e., that which occurs with conscious intent and awareness. However, recent evidence suggests that there may be a negative relationship between mindfulness and implicit types of learning, or those that occur without conscious awareness or intent. Here we examined the neural mechanisms underlying the recently reported negative relationship between dispositional mindfulness and implicit probabilistic sequence learning in both younger and older adults. We tested the hypothesis that the relationship is mediated by communication, or functional connectivity, of brain regions once traditionally considered to be central to dissociable learning systems: the caudate, medial temporal lobe (MTL), and prefrontal cortex (PFC). We first replicated the negative relationship between mindfulness and implicit learning in a sample of healthy older adults (60–90 years old) who completed three event-related runs of an implicit sequence learning task. Then, using a seed-based connectivity approach, we identified task-related connectivity associated with individual differences in both learning and mindfulness. The main finding was that caudate-MTL connectivity (bilaterally) was positively correlated with learning and negatively correlated with mindfulness. Further, the strength of task-related connectivity between these regions mediated the negative relationship between mindfulness and learning. This pattern of results was limited to the older adults. Thus, at least in healthy older adults, the functional communication between two interactive learning-relevant systems can account for the relationship between mindfulness and implicit probabilistic sequence learning.     

Composing lexical versus functional adjectives: Evidence for uniformity in the left temporal lobe

Psychonomic Bulletin & Review - Featural information (e.g., color or shape) allows interlocutors to focus their attention on the specific items under discussion from the vast set of...     

Emotion dysregulation and functional connectivity in children with and without a history of major depressive disorder

Recent interest has emerged in understanding the neural mechanisms by which deficits in emotion regulation (ER) early in development may relate to later depression. Corticolimbic alterations reported in emotion dysregulation and depression may be one possible link. We examined the relationships between emotion dysregulation in school age, corticolimbic resting-state functional connectivity (rs-FC) in preadolescence, and depressive symptoms in adolescence. Participants were 143 children from a longitudinal preschool onset depression study who completed the Children Sadness Management Scale (CSMS; measuring ER), Child Depression Inventory (CDI-C; measuring depressive symptoms), and two resting-state MRI scans. Rs-FC between four primary regions of interest (ROIs; bilateral dorsolateral prefrontal cortex [dlPFC] and amygdala) and six target ROIs thought to contribute to ER were examined. Findings showed that ER in school age did not predict depressive symptoms in adolescence, but did predict preadolescent increases in dlPFC-insula and dlPFC-ventromedial PFC rs-FC across diagnosis, as well as increased dlPFC-dorsal anterior cingulate cortex (dACC) rs-FC in children with a history of depression. Of these profiles, only dlPFC-dACC rs-FC in preadolescence predicted depressive symptoms in adolescence. However, dlPFC-dACC connectivity did not mediate the relationship between ER in school age and depressive symptoms in adolescence. Despite the absence of a direct relationship between ER and depressive symptoms and no significant rs-FC mediation, the rs-FC profiles predicted by ER are consistent with the hypothesis that emotion dysregulation is associated with abnormalities in top-down control functions. The extent to which these relationships might confer greater risk for later depression, however, remains unclear.     

Movement structure in young and elderly adults during goal-directed movements of the left and right arm

Elderly adults often exhibit performance deficits during goal-directed movements of the dominant arm compared with young adults. Recent studies involving hemispheric lateralization have provided evidence that the dominant and non-dominant hemisphere-arm systems are specialized for controlling different movement parameters and that hemispheric specialization may be reduced during normal aging. The purpose was to examine age-related differences in the movement structure for the dominant (right) and non-dominant (left) during goal-directed movements. Young and elderly adults performed 72 aiming movements as fast and as accurately as possible to visual targets with both arms. The findings suggest that previous research utilizing the dominant arm can be generalized to the non-dominant arm because performance was similar for the two arms. However, as expected, the elderly adults showed shorter relative primary submovement lengths and longer relative primary submovement durations, reaction times, movement durations, and normalized jerk scores compared to the young adults.     

Spatial and temporal episodic memory retrieval recruit dissociable functional networks in the human brain

Imaging, electrophysiological studies, and lesion work have shown that the medial temporal lobe (MTL) is important for episodic memory; however, it is unclear whether different MTL regions support the spatial, temporal, and item elements of episodic memory. In this study we used fMRI to examine retrieval performance emphasizing different aspects of episodic memory in the context of a spatial navigation paradigm. Subjects played a taxi-driver game ("yellowcab"), in which they freely searched for passengers and delivered them to specific landmark stores. Subjects then underwent fMRI scanning as they retrieved landmarks, spatial, and temporal associations from their navigational experience in three separate runs. Consistent with previous findings on item memory, perirhinal cortex activated most strongly during landmark retrieval compared with spatial or temporal source information retrieval. Both hippocampus and parahippocampal cortex activated significantly during retrieval of landmarks, spatial associations, and temporal order. We found, however, a significant dissociation between hippocampal and parahippocampal cortex activations, with spatial retrieval leading to greater parahippocampal activation compared with hippocampus and temporal order retrieval leading to greater hippocampal activation compared with parahippocampal cortex. Our results, coupled with previous findings, demonstrate that the hippocampus and parahippocampal cortex are preferentially recruited during temporal order and spatial association retrieval--key components of episodic "source" memory.     

Developmental changes in personal goal orientation from young to late adulthood: from striving for gains to maintenance and prevention of losses

Using a multimethod approach, the authors conducted 4 studies to test life span hypotheses about goal orientations across adulthood. Confirming expectations, in Studies 1 and 2 younger adults reported a primary growth orientation in their goals, whereas older adults reported a stronger orientation toward maintenance and loss prevention. Orientation toward prevention of loss correlated negatively with well-being in younger adults. In older adults, orientation toward maintenance was positively associated with well-being. Studies 3 and 4 extend findings of a self-reported shift in goal orientation to the level of behavioral choice involving cognitive and physical fitness goals. Studies 3 and 4 also examine the role of expected resource demands. The shift in goal orientation is discussed as an adaptive mechanism to manage changing opportunities and constraints across adulthood.