The inferior parietal lobule and temporoparietal junction: A network perspective

Vestibular Stimulation Modulates Neural Correlates of Own-body Mental Imagery

There is growing evidence that vestibular information is not only involved in reflexive eye movements and the control of posture but it also plays an important role in higher order cognitive processes. Previous behavioral research has shown that concomitant vestibular stimuli influence performance in tasks that involve imagined self-rotations. These results suggest that imagined and perceived body rotations share common mechanisms. However, the nature and specificity of these effects remain largely unknown. Here, we investigated the neural mechanisms underlying this vestibulocognitive interaction. Participants (n = 20) solved an imagined self-rotation task during caloric vestibular stimulation. We found robust main effects of caloric vestibular stimulation in the core region of the vestibular network, including the rolandic operculum and insula bilaterally, and of the cognitive task in parietal and frontal regions. Interestingly, we found an interaction of stimulation and task in the left inferior parietal lobe, suggesting that this region represents the modulation of imagined body rotations by vestibular input. This result provides evidence that the inferior parietal lobe plays a crucial role in the neural integration of mental and physical body rotation.

Brain structural connectivity network alterations in insomnia disorder reveal a central role of the right angular gyrus

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People with insomnia show widespread brain structural hyperconnectivity.

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The right angular gyrus is central to the structural connectivity alterations.

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Connectivity of this angular gyrus subnetwork correlates with reactive hyperarousal.

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Brain structural hyperconnectivity may mark vulnerability to insomnia.

Insomnia Disorder (ID) is a prevalent and persistent condition, yet its neural substrate is not well understood. The cognitive, emotional, and behavioral characteristics of ID suggest that vulnerability involves distributed brain networks rather than a single brain area or connection. The present study utilized probabilistic diffusion tractography to compare the whole-brain structural connectivity networks of people with ID and those of matched controls without sleep complaints.

Diffusion-weighted images and T1-weighed images were acquired in 51 people diagnosed with ID (21–69 years of age, 37 female) and 48 matched controls without sleep complaints (22–70 years of age, 31 female). Probabilistic tractography was performed to construct the whole-brain structural connectivity network of each participant. Case–control differences in connectivity strength and network efficiency were evaluated with permutation tests.

People with ID showed structural hyperconnectivity within a subnetwork that spread over frontal, parietal, temporal, and subcortical regions and was anchored at the right angular gyrus. The result was robust across different edge-weighting strategies. Moreover, converging support was given by the finding of heightened right angular gyrus nodal efficiency (harmonic centrality) across varying graph density in people with ID. Follow-up correlation analyses revealed that subnetwork connectivity was associated with self-reported reactive hyperarousal.

The findings demonstrate that the right angular gyrus is a hub of enhanced structural connectivity in ID. Hyperconnectivity within the identified subnetwork may contribute to increased reactivity to stimuli and may signify vulnerability to ID.

Toward a standard model of consciousness: Reconciling the attention schema, global workspace, higher-order thought, and illusionist theories

Here we examine how people's understanding of consciousness may have been shaped by an implicit theory of mind. This social cognition approach may help to make sense of an apparent divide between the physically incoherent consciousness we think we have and the complex, rich, but mechanistic consciousness we may actually have. We suggest this approach helps reconcile some of the current cognitive neuroscience theories of consciousness. We argue that a single, coherent explanation of consciousness is available and has been for some time, encompassing the views of many researchers, but is not yet recognized. It is obscured partly by terminological differences, and partly because researchers view isolated pieces of it as rival theories. It may be time to recognize that a deeper, coherent pool of ideas, a kind of standard model, is available to explain multiple layers of consciousness and how they relate to specific networks within the brain.

Abnormal Functional Connectivity in Cognitive Control Network, Default Mode Network, and Visual Attention Network in Internet Addiction: A Resting-State fMRI Study

Internet addiction (IA) has become a global mental and social problem, which may lead to a series of psychiatric symptoms including uncontrolled use of internet, and lack of concentration. However, the exact pathophysiology of IA remains unclear. Most of functional connectivity studies were based on pre-selected regions of interest (ROI), which could not provide a comprehensive picture of the communication abnormalities in IA, and might lead to limited or bias observations. Using local functional connectivity density (lFCD), this study aimed to explore the whole-brain abnormalities of functional connectivity in IA. We evaluated the whole-brain lFCD resulting from resting-state fMRI data in 28 IA individuals and 30 demographically matched healthy control subjects (HCs). The correlations between clinical characteristics and aberrant lFCD were also assessed. Compared with HCs, subjects with IA exhibited heightened lFCD values in the right dorsolateral prefrontal cortex (DLPFC), left parahippocampal gyrus (PHG), and cerebellum, and the bilateral middle cingulate cortex (MCC) and superior temporal pole (STP), as well as decreased lFCD values in the right inferior parietal lobe (IPL), and bilateral calcarine and lingual gyrus. Voxel-based correlation analysis revealed the significant correlations between the Young's Internet Addiction Test (IAT) score and altered lFCD values in the left PHG and bilateral STP. These findings revealed the hyper-connectivity in cognitive control network and default mode network as well as the hypo-connectivity in visual attention network, verifying the common mechanism in IA and substance addiction, and the underlying association between IA, and attention deficit/hyperactivity disorder in terms of neurobiology.

Neurofeedback and neuroplasticity of visual self-processing in depressed and healthy adolescents: A preliminary study

Adolescence is a neuroplastic period for self-processing and emotion regulation transformations, that if derailed, are linked to persistent depression. Neural mechanisms of adolescent self-processing and emotion regulation ought to be targeted via new treatments, given moderate effectiveness of current interventions. Thus, we implemented a novel neurofeedback protocol in adolescents to test the engagement of circuits sub-serving self-processing and emotion regulation.

Methods

Depressed (n = 34) and healthy (n = 19) adolescents underwent neurofeedback training using a novel task. They saw their happy face as a cue to recall positive memories and increased displayed amygdala and hippocampus activity. The control condition was counting-backwards while viewing another happy face. A self vs. other face recognition task was administered before and after neurofeedback training.

Results

Adolescents showed higher frontotemporal activity during neurofeedback and higher amygdala and hippocampus and hippocampi activity in time series and region of interest analyses respectively. Before neurofeedback there was higher saliency network engagement for self-face recognition, but that network engagement was lower after neurofeedback. Depressed youth exhibited higher fusiform, inferior parietal lobule and cuneus activity during neurofeedback, but controls appeared to increase amygdala and hippocampus activity faster compared to depressed adolescents.

Conclusions

Neurofeedback recruited frontotemporal cortices that support social cognition and emotion regulation. Amygdala and hippocampus engagement via neurofeedback appears to change limbic-frontotemporal networks during self-face recognition. A placebo group or condition and contrasting amygdala and hippocampus, hippocampi or right amygdala versus frontal loci of neurofeedback, e.g. dorsal anterior cingulate cortex, with longer duration of neurofeedback training will elucidate dosage and loci of neurofeedback in adolescents.

Mean diffusivity related to rule-breaking guilt: the Macbeth effect in the sensorimotor regions

Guilt, a self-conscious emotion, includes self-focused role taking and also correlates with other-oriented role-taking. Excess guilt proneness might be relevant to obsessive compulsive disorders. The white matter (WM) neural correlates of the degree of guilt have not yet been determined. We hypothesized that the WM structures involved in feelings of guilt are associated with social and moral cognition (inferior parietal lobule [IPL], prefrontal cortex [PFC], and cingulate), and aimed to visualize this using diffusion MRI. We investigated the association between regional WM structures (WM volume, and fractional anisotropy, and mean diffusivity [MD]), and feelings of guilt in 1196 healthy, young students using MRI and the Guilty Feeling Scale, which comprises interpersonal situation (IPS; guilt from hurting friends) and rule-breaking situation (RBS; deontological guilt) scores. The primary novel finding presented here is that MD in the right somatosensory and motor cortices from arm to hand were positively correlated with RBS scores. Further, consistent with our hypothesis, RBS scores were positively correlated with MD in the same regions. These results would be predicted by the Macbeth effect, an obsession with dirt leading to hand-washing rituals resulting from guilt, made famous by the Shakespearian character Lady Macbeth. “What, will these hands ne’er be clean?” William Shakespeare (Shakespeare, 1606) Macbeth.

Neural correlates of emotion processing predict resilience in youth at familial risk for mood disorders

Aberrant face emotion processing has been demonstrated in youth with and at a familial risk for bipolar and major depressive disorders. However, the neurobiological factors related to emotion processing that underlie resilience from youth-onset mood disorders are not well understood. Functional magnetic resonance imaging data during an implicit emotion processing task were collected at baseline from a sample of 50 youth, ages 8-17, who were healthy but also familially at high risk for either bipolar disorder or major depressive disorder, and 24 healthy controls with no family history of psychopathology (HCL). Participants were reevaluated 3 years later and classified into three groups for analysis: high-risk youth who converted to a psychiatric diagnosis (CVT; N = 23), high-risk youth who were resilient from developing any psychopathology (RES; N = 27), and HCL youth (N = 24) who remained healthy at follow-up. For happy > calm faces, the CVT and RES groups had significantly lower activation in the left inferior parietal lobe (IPL), while the RES group had lower activation in the right supramarginal gyrus. For fear > calm faces, the RES group had lower activation in the right precuneus and inferior frontal gyrus (IFG) compared to the CVT group. Connectivity analyses revealed the RES group exhibited higher left IPL connectivity with visual cortical regions for happy > calm faces, and higher IFG connectivity with frontal, temporal, and limbic regions for fear > calm faces. These connectivities were correlated with improvements in prosocial behaviors and global functioning. Our findings suggest that differential activation and connectivity in the IPL, IFG, and precuneus in response to emotional stimuli may represent distinct resilience and risk markers for youth-onset mood disorders.

Adolescent suicide attempts and ideation are linked to brain function during peer interactions

Understanding the neural correlates of social interaction among depressed adolescents with suicidal tendencies might help personalize treatment. We tested whether brain function during social interaction is disrupted for depressed adolescents with (1) high suicide ideation and (2) recent attempts. Depressed adolescents with high suicide ideation, including attempters (n = 45;HS) or low suicide ideation (n = 42;LS), and healthy adolescents (n = 39;HC), completed a version of the Cyberball peer interaction task during an fMRI scan. Groups were compared on brain activity during peer exclusion and inclusion versus a non-social condition. During peer exclusion and inclusion, HS youth showed significantly lower activity in precentral and postcentral gyrus, superior temporal gyrus, medial frontal gyrus, insula, and putamen compared to LS youth; and significantly reduced activity in caudate and anterior cingulate cortex compared to HC youth. In a second analysis, suicide attempters (n = 26;SA) were compared to other groups. SA adolescents showed significantly higher activity in ACC and superior and middle frontal gyrus than all other groups. Brain activity was significantly correlated with negative emotionality, social functioning, and cognitive control. Conclusions: Adolescent suicide ideation and attempts were linked to altered neural function during positive and negative peer interactions. We discuss the implications of these findings for suicide prevention efforts.

Differential Effects of Sustained Manual Pressure Stimulation According to Site of Action

Sustained pressure stimulation of the body surface has been used in several physiotherapeutic techniques, such as reflex locomotion therapy. Clinical observations of global motor responses and subsequent motor behavioral changes after stimulation in certain sites suggest modulation of central sensorimotor control, however, the neuroanatomical correlates remain undescribed. We hypothesized that different body sites would specifically influence the sensorimotor system during the stimulation. We tested the hypothesis using functional magnetic resonance imaging (fMRI) in thirty healthy volunteers (mean age 24.2) scanned twice during intermittent manual pressure stimulation, once at the right lateral heel according to reflex locomotion therapy, and once at the right lateral ankle (control site). A flexible modeling approach with finite impulse response basis functions was employed since non-canonical hemodynamic response was expected. Subsequently, a clustering algorithm was used to separate areas with differential timecourses. Stimulation at both sites induced responses throughout the sensorimotor system that could be mostly separated into two anti-correlated subsystems with transient positive or negative signal change and rapid adaptation, although in heel stimulation, insulo-opercular cortices and pons showed sustained activation. In direct voxel-wise comparison, heel stimulation was associated with significantly higher activation levels in the contralateral primary motor cortex and decreased activation in the posterior parietal cortex. Thus, we demonstrate that the manual pressure stimulation affects multiple brain structures involved in motor control and the choice of stimulation site impacts the shape and amplitude of the blood oxygenation level-dependent response. We further discuss the relationship between the affected structures and behavioral changes after reflex locomotion therapy.

Spatial orientation: Model-based approach to multi-sensory mechanisms

Perception of spatial orientation is generated through multimodal sensory integration. In this process, there are systematic errors with changes in the head or body position, which reflect challenges for the brain in maintaining a common sensory reference frame for spatial orientation. Here, we focus on this multisensory aspect of spatial orientation. We review a Bayesian spatial perception model that can be used as a framework to study sensory contributions to spatial orientation during lateral head tilts and probe neural networks involved in this process.

Neuroimaging Markers of Risk, Disease Expression, and Resilience to Bipolar Disorder

PURPOSE OF REVIEW

Familial predisposition to bipolar disorder is associated with increased risk of affective morbidity in the first-degree relatives of patients. Nevertheless, a substantial proportion of relatives remain free of psychopathology throughout their lifetime. A series of studies reviewed here were designed to test whether resilience in these high-risk individuals is associated with adaptive brain plasticity.

RECENT FINDINGS

The findings presented here derive from structural and functional magnetic resonance imaging data obtained from patients, their resilient first-degree relatives, and healthy individuals. Patients and relatives showed similar abnormalities in activation and connectivity while performing tasks of interference control and facial affect recognition and in the resting-state connectivity of sensory and motor regions. Resilient relatives manifested unique neuroimaging features that differentiated them from patients and healthy individuals. Specifically, they had larger cerebellar vermis volume, enhanced prefrontal connectivity during task performance, and enhanced functional integration of the default mode network in task-free conditions. Resilience to bipolar disorder is not the reverse of risk but is associated with adaptive brain changes indicative of increased neural reserve. This line of research may open new avenues in preventing and treating bipolar disorder.

Maturation changes the excitability and effective connectivity of the frontal lobe: A developmental TMS-EEG study

The combination of transcranial magnetic stimulation with simultaneous electroencephalography (TMS-EEG) offers direct neurophysiological insight into excitability and connectivity within neural circuits. However, there have been few developmental TMS-EEG studies to date, and they all have focused on primary motor cortex stimulation. In the present study, we used navigated high-density TMS-EEG to investigate the maturation of the superior frontal cortex (dorsal premotor cortex [PMd]), which is involved in a broad range of motor and cognitive functions known to develop with age. We demonstrated that reactivity to frontal cortex TMS decreases with development. We also showed that although frontal cortex TMS elicits an equally complex TEP waveform in all age groups, the statistically significant between-group differences in the topography of the TMS-evoked peaks and differences in current density maps suggest changes in effective connectivity of the right PMd with maturation. More generally, our results indicate that direct study of the brain's excitability and effective connectivity via TMS-EEG co-registration can also be applied to pediatric populations outside the primary motor cortex, and may provide useful information for developmental studies and studies on developmental neuropsychiatric disorders.

Intrinsic Rivalry. Can White Bears Help Us With the Other Side of Consciousness?

Studies of consciousness have traditionally been based mainly upon the perceptual domains of consciousness. However, there is another side of consciousness, represented by various types of intrinsic conscious experiences. Even though intrinsic experiences can represent up to 50% of our conscious experiences, they are still largely neglected in conscious studies. We assume there are two reasons for this. First, the field of intrinsic conscious experiences is methodologically far more problematic than any other. Second, specific paradigms for capturing the correlates of intrinsic conscious experiences are almost nonexistent. Nevertheless, we expect the intrinsic side of consciousness to soon take its place in conscious studies, but first new experimental paradigms will have to be devised, which would be of a similar design to the paradigms used in studies of perceptual consciousness. In this hypothesis and theory article, we propose such a hypothetical paradigm, presenting the exploratory data of our proof-of-concept study, discussing its use, and addressing its shortcomings and their possible remediation.

The relationship between spatial configuration and functional connectivity of brain regions revisited

Previously we showed that network-based modelling of brain connectivity interacts strongly with the shape and exact location of brain regions, such that cross-subject variations in the spatial configuration of functional brain regions are being interpreted as changes in functional connectivity (Bijsterbosch et al., 2018). Here we show that these spatial effects on connectivity estimates actually occur as a result of spatial overlap between brain networks. This is shown to systematically bias connectivity estimates obtained from group spatial ICA followed by dual regression. We introduce an extended method that addresses the bias and achieves more accurate connectivity estimates.

Increased Functional Connectivity of the Angular Gyrus During Imagined Music Performance

The angular gyrus (AG) is a hub of several networks that are involved in various functions, including attention, self-processing, semantic information processing, emotion regulation, and mentalizing. Since these functions are required in music performance, it is likely that the AG plays a role in music performance. Considering that these functions emerge as network properties, this study analyzed the functional connectivity of the AG during the imagined music performance task and the resting condition. Our hypothesis was that the functional connectivity of the AG is modulated by imagined music performance. In the resting condition, the AG had connections with the medial prefrontal cortex (mPFC), posterior cingulate cortex (PCC), and precuneus as well as the superior and inferior frontal gyri and with the temporal cortex. Compared with the resting condition, imagined music performance increased the functional connectivity of the AG with the superior frontal gyrus (SFG), mPFC, precuneus, PCC, hippocampal/parahippocampal gyrus (H/PHG), and amygdala. The anterior cingulate cortex (ACC) and superior temporal gyrus (STG) were newly engaged or added to the AG network during the task. In contrast, the supplementary motor area (SMA), sensorimotor areas, and occipital regions, which were anti-correlated with the AG in the resting condition, were disengaged during the task. These results lead to the conclusion that the functional connectivity of the AG is modulated by imagined music performance, which suggests that the AG plays a role in imagined music performance.

Region-specific association between basal blood insulin and cerebral glucose metabolism in older adults

Background

Although previous studies have suggested that insulin plays a role in brain function, it still remains unclear whether or not insulin has a region-specific association with neuronal and synaptic activity in the living human brain. We investigated the regional pattern of association between basal blood insulin and resting-state cerebral glucose metabolism (CMglu), a proxy for neuronal and synaptic activity, in older adults.

Method

A total of 234 nondiabetic, cognitively normal (CN) older adults underwent comprehensive clinical assessment, resting-state 18F-fluodeoxyglucose (FDG)-positron emission tomography (PET) and blood sampling to determine overnight fasting blood insulin and glucose levels, as well as apolipoprotein E (APOE) genotyping.

Results

An exploratory voxel-wise analysis of FDG-PET without a priori hypothesis demonstrated a positive association between basal blood insulin levels and resting-state CMglu in specific cerebral cortices and hippocampus, rather than in non-specific overall cerebral regions, even after controlling for the effects of APOE e4 carrier status, vascular risk factor score, body mass index, fasting blood glucose, and demographic variables. Particularly, a positive association of basal blood insulin with CMglu in the right posterior hippocampus and adjacent parahippocampal region as well as in the right inferior parietal region remained significant after multiple comparison correction. Conversely, no region showed negative association between basal blood insulin and CMglu.

Conclusions

Our finding suggests that basal fasting blood insulin may have association with neuronal and synaptic activity in specific cerebral regions, particularly in the hippocampal/parahippocampal and inferior parietal regions.

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We investigated regional pattern of association between basal blood insulin and resting-state cerebral glucose metabolism.

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Significant clusters with positive associations were found mainly in the hippocampal and inferior parietal regions.

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Our finding suggests a region-specific association of basal blood insulin with resting-state cerebral glucose metabolism.

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Further studies to elucidate underlying mechanism and implication of this region-specific association will be necessary.

Neurodevelopmental correlates of the emerging adult self

The self-concept – the set of beliefs that a person has about themselves – shows significant development from adolescence to early adulthood, in parallel with brain development over the same period. We sought to investigate how age-related changes in self-appraisal processes corresponded with brain network segregation and integration in healthy adolescents and young adults. We scanned 88 participants (46 female), aged from 15 to 25 years, as they performed a self-appraisal task. We first examined their patterns of activation to self-appraisal, and replicated prior reports of reduced dorsomedial prefrontal cortex activation with older age, with similar reductions in precuneus, right anterior insula/operculum, and a region extending from thalamus to striatum. We used independent component analysis to identify distinct anterior and posterior components of the default mode network (DMN), which were associated with the self-appraisal and rest-fixation parts of the task, respectively. Increasing age was associated with reduced functional connectivity between the two components. Finally, analyses of task-evoked interactions between pairs of nodes within the DMN identified a subnetwork that demonstrated reduced connectivity with increasing age. Decreased network integration within the DMN appears to be an important higher-order maturational process supporting the emerging adult self.

The evolution of the temporoparietal junction and posterior superior temporal sulcus

The scale at which humans can handle complex social situations is massively increased compared to other animals. However, the neural substrates of this scaling remain poorly understood. In this review, we discuss how the expansion and rearrangement of the temporoparietal junction and posterior superior temporal sulcus (TPJ-pSTS) may have played a key role in the growth of human social abilities. Comparing the function and anatomy of the TPJ-pSTS in humans and macaques, which are thought to be separated by 25 million years of evolution, we find that the expansion of this region in humans has shifted the architecture of the dorsal and ventral processing streams. The TPJ-pSTS contains areas related to face-emotion processing, attention, theory of mind operations, and memory; its expansion has allowed for the elaboration and rearrangement of the cortical areas contained within, and potentially the introduction of new cortical areas. Based on the arrangement and the function of these areas in the human, we propose that the TPJ-pSTS is the basis of a third frontoparietal processing stream that underlies the increased social abilities in humans. We then describe a model of how the TPJ-pSTS areas interact as a hub that coordinates the activities of multiple brain networks in the exploration of the complex dynamic social scenes typical of the human social experience.

Functional Correlates of Resting-State Connectivity in the Default Mode Network of Heroin Users on Methadone Treatment and Medication-Free Therapeutic Community Program

The treatment of heroin addiction is a complex process involving changes in addictive behavior and brain functioning. The goal of this study was to explore the brain default mode network (DMN) functional connectivity using resting-state functional magnetic resonance imaging (rs-fMRI) and decision-making performance based on the Cambridge gambling task in heroin-dependent individuals undergoing methadone treatment (MT, n = 11) and medication-free faith-based therapeutic community program (TC, n = 11). The DMN involved the medial prefrontal cortex (mPFC), left inferior parietal lobe (IPL_L), right inferior parietal lobe (IPL_R), and posterior cingulate cortex (PCC) subregions for all participants in both the MT and TC groups. Compared with MT, TC had an increased functional connectivity in IPL_L-IPL_R and IPL_R-PCC and decreased functional connectivity in mPFC-IPL_L and IPL_L-PCC. Both groups exhibited no significant difference in the regional rs-fMRI metric [i.e., amplitude of low-frequency fluctuation (ALFF)]. In the analysis of the neural correlates for decision-making performance, risk adjustment was positively associated with ALFF in IPL_L for all participants considering the group effects. The involvement of IPL in decision-making performance and treatment response among heroin-dependent patients warrants further investigation.

Abnormal Voxel-Wise Degree Centrality in Patients With Late-Life Depression: A Resting-State Functional Magnetic Resonance Imaging Study

OBJECTIVES

Late-life depression (LLD) has negative impacts on somatic, emotional and cognitive domains of the lives of patients. Elucidating the abnormality in the brain networks of LLD patients could help to strengthen the understanding of LLD pathophysiology, however, the studies exploring the spontaneous brain activity in LLD during the resting state remain limited. This study aimed at identifying the voxel-level whole-brain functional connectivity changes in LLD patients.

METHODS

Fifty patients with late-life depression (LLD) and 33 healthy controls were recruited. All participants underwent a resting-state functional magnetic resonance imaging scan to assess the voxel-wise degree centrality (DC) changes in the patients. Furthermore, DC was compared between two patient subgroups, the late-onset depression (LOD) and the early-onset depression (EOD).

RESULTS

Compared with the healthy controls, LLD patients showed increased DC in the inferior parietal lobule, parahippocampal gyrus, brainstem and cerebellum (p < 0.05, AlphaSim-corrected). LLD patients also showed decreased DC in the somatosensory and motor cortices and cerebellum (p < 0.05, AlphaSim-corrected). Compared with EOD patients, LOD patients showed increased centrality in the superior and middle temporal gyrus and decreased centrality in the occipital region (p < 0.05, AlphaSim-corrected). No significant correlation was found between the DC value and the symptom severity or disease duration in the patients after the correction for multiple comparisons.

CONCLUSIONS

These findings indicate that the intrinsic abnormality of network centrality exists in a wide range of brain areas in LLD patients. LOD patients differ with EOD patients in cortical network centrality. Our study might help to strengthen the understanding of the pathophysiology of LLD and the potential neural substrates underlie related emotional and cognitive impairments observed in the patients.

Interactions between monoamine oxidase A rs1137070 and smoking on brain structure and function in male smokers

The monoamine oxidase A (MAOA) enzyme metabolizes monoamine neurotransmitters such as dopamine, serotonin and norepinephrine, and its genetic polymorphism (rs1137070) influences its activity level and is associated with smoking behaviors. However, the underlying neural mechanisms of the gene × environment interactions remain largely unknown. In this study, we aimed to explore the interactive effects of the rs1137070 and cigarette smoking on gray matter volume (GMV) and functional connectivity strength (FCS). A total of 81 smokers and 42 nonsmokers were enrolled in the present study. Voxel-based morphometry analysis showed a significant rs1137070 genotype × smoking effect on the GMV of the left orbitofrontal cortex (OFC), such that individuals with risk allele had greater GMV among nonsmokers but not smokers. Meanwhile, rs1137070 variant and nicotine dependence interactively altered the FCS of the right hippocampus, the left inferior parietal lobule (IPL), the left dorsolateral prefrontal cortex and bilateral OFC. In addition, the FCS in the left IPL was correlated with smoking initiation and smoking years in smokers with the risk allele. These findings suggest that MAOA rs1137070 contributes to the susceptibility to nicotine dependence through its influence on brain circuits involved in reward and attention, and interacts with smoking in the progression.

Common Recruitment of Angular Gyrus in Episodic Autobiographical Memory and Bodily Self-Consciousness

Parietal cortex and adjacent parts of the temporal cortex have recently been associated with bodily self-consciousness (BSC). Similarly, growing evidence suggests that the lateral parietal cortex is crucial for the subjective aspects of episodic autobiographical memory (EAM), which is based on the conscious experience of reliving past events. However, the neuroanatomical relationship between both fundamental aspects remains currently unexplored. Moreover, despite the wealth of neuroimaging data on EAM, only few neuroimaging studies have examined BSC and even fewer examined those aspects of BSC that are most closely related to EAM. Here, we investigated whether regions in the inferior parietal lobule (IPL) that have been involved in spatial aspects of BSC (self-location and first-person perspective), as described by Ionta et al. (2011) are also active in studies investigating autobiographical memory. To examine this relation, we thus compared the regions indicated in the study by Ionta et al. (2011) based on data in healthy participants and neurological patients, with the results from a meta-analytical study we performed based on functional neuroimaging studies on EAM and semantic autobiographical memory (SAM). We report an anatomical overlap bilaterally in the angular gyrus (AG), but not in other parietal or temporal lobe structures between BSC and EAM. Moreover, there was no overlap between BSC and SAM. These preliminary data suggest that the bilateral AG may be a key structure for the conscious re-experiencing of past life episodes (EAM) and the conscious on-line experience of being located and experiencing the world in first-person (BSC).

Dynamic Interactions between Emotion Perception and Action Preparation for Reacting to Social Threat: A Combined cTBS-fMRI Study

Expressions of emotion are powerful triggers for situation-appropriate responses by the observer. Of particular interest regarding the preparation of such adaptive actions are parietal and premotor cortices, given their potential for interaction with the amygdala (AMG), which is known to play a crucial role in the processing of affective information and in motor response. We set out to disentangle the respective roles of the inferior parietal lobule (IPL) and ventral premotor cortex (PMv) in humans in the processing of emotional body expressions by assessing remote effects of continuous theta burst stimulation (cTBS) in the action network and in AMG. Participants were presented with blocks of short videos showing either angry or neutral whole-body actions. The experiment consisted of three fMRI sessions: two sessions were preceded by stimulation of either right IPL (rIPL) or right PMv (rPMv); and a third session assessed baseline activity. Interestingly, whereas at baseline the left AMG did not differentiate between neutral and angry body postures, a significant difference between these conditions emerged after stimulation of either rIPL or rPMv, with much larger responses to angry than to neutral stimuli. In addition, the effects of cTBS stimulation and emotion were also observed in two other action-relevant areas, the supplementary motor area and the superior parietal cortex. Together, these results show how areas involved in action and emotion perception and in action preparation interact dynamically.

Exploring the Role of Temporoparietal Cortex in Upright Perception and the Link With Torsional Eye Position

Upright perception is a key aspect of orientation constancy, as we maintain a stable perception of the world despite continuous movements of our eyes, head, and body. Torsional position of the eyes can impact perception of upright by changing orientation of the images on the retina relative to gravity. Here, we investigated the role of temporoparietal cortex in upright perception with respect to ocular torsion, by means of the inhibitory effect of continuous theta burst transcranial magnetic stimulation (TMS). We used a subjective visual vertical (SVV) paradigm to track changes in upright perception, and a custom video method to track ocular torsion simultaneously. Twelve participants were tested during a lateral head tilt of 20° to the left. TMS at the posterior aspect of the supramarginal gyrus (SMGp) resulted in an average SVV shift in the opposite direction of the head tilt compared to a sham stimulation (1.8°). Ocular torsion following TMS at SMGp showed no significant change compared to the sham stimulation (-0.1°). Thus, changes in upright perception at SMGp were dissociated from ocular torsion. This finding suggests that perception of upright at SMGp is primarily related to sensory processing for spatial orientation, as opposed to subcortical regions that have direct influence on ocular torsion.

Structural correlates of Openness and Intellect: Implications for the contribution of personality to creativity

Openness/Intellect (i.e., openness to experience) is the Big Five personality factor most consistently associated with individual differences in creativity. Recent psychometric evidence has demonstrated that this factor consists of two distinct aspects-Intellect and Openness. Whereas Intellect reflects perceived intelligence and intellectual engagement, Openness reflects engagement with fantasy, perception, and aesthetics. We investigated the extent to which Openness and Intellect are associated with variations in brain structure as measured by cortical thickness, area, and volume (N = 185). Our results demonstrated that Openness was correlated inversely with cortical thickness and volume in left middle frontal gyrus (BA 6), middle temporal gyrus (MTG, BA 21), and superior temporal gyrus (BA 41), and exclusively with cortical thickness in left inferior parietal lobule (BA 40), right inferior frontal gyrus (IFG, BA 45), and MTG (BA 37). When age and sex were statistically controlled for, the inverse correlations between Openness and cortical thickness remained statistically significant for all regions except left MTG, whereas the correlations involving cortical volume remained statistically significant only for left middle frontal gyrus. There was no statistically significant correlation between Openness and cortical area, and no statistically significant correlation between Intellect and cortical thickness, area, or volume. Our results demonstrate that individual differences in Openness are correlated with variation in brain structure-particularly as indexed by cortical thickness. Given the involvement of the above regions in processes related to memory and cognitive control, we discuss the implications of our findings for the possible contribution of personality to creative cognition.

Subanaesthetic ketamine and altered states of consciousness in humans

BACKGROUND

Despite its designation as a 'dissociative anaesthetic,' the dissociative and psychoactive effects of ketamine remain incompletely understood. The goal of this study was to characterise the subjective experiences and accompanying EEG changes with subanaesthetic doses of ketamine.

METHODS

High-density EEG was recorded in 15 human volunteers before, during, and after subanaesthetic ketamine infusion (0.5 mg kg^-1 over 40 min), with self-reported measures of altered states of consciousness obtained after ketamine exposure. Sensor- and source-level EEG changes were analysed with a focus on spectral power and regional changes.

RESULTS

Ketamine-induced altered states were characterised predominantly by dissociative experiences such as disembodiment and ego transcendence; sensory disturbances were also common. Ketamine broadly decreased low-frequency power, with mean reductions largest at alpha (8-12 Hz) in parietal (-0.94 dB, P<0.001) and occipital (-1.8 dB, P<0.001) channel clusters. Significant decreases in alpha were identified in the precuneus and temporal-parietal junction.

CONCLUSIONS

Ketamine induces altered states of consciousness during periods of reduced alpha power in the precuneus and temporal-parietal junction. Modulation of these temporal-parietal loci are candidate mechanisms of the psychoactive effects of ketamine, given that this region is involved in multisensory integration, body representation, and consciousness.

The temporoparietal junction and awareness

Visual attention and awareness can be experimentally separated. In a recent study (Webb et al., Cortical networks involved in visual awareness independently of visual attention. Proc Natl Acad USA 2016a;113:13923-8), we suggested that awareness was associated with activity in a set of cortical networks that overlap the temporoparietal junction. In a comment, Morales et al. (Measuring away an attentional confound? Neurosci Conscious 2017;3:doi:10.1093/nc/nix018) suggested that we had imperfectly controlled attention thereby jeopardizing the experimental logic. Though we agree that attention behaves differently in the presence and absence of awareness, we argue it is still possible to roughly equate the level of attention between aware and unaware conditions, and that an imbalance in attention probably does not explain our experimental results.

Cognitive control over memory - individual differences in memory performance for emotional and neutral material

It is widely accepted that people differ in memory performance. The ability to control one’s memory depends on multiple factors, including the emotional properties of the memorized material. While it was widely demonstrated that emotion can facilitate memory, it is unclear how emotion modifies our ability to suppress memory. One of the reasons for the lack of consensus among researchers is that individual differences in memory performance were largely neglected in previous studies. We used the directed forgetting paradigm in an fMRI study, in which subjects viewed neutral and emotional words, which they were instructed to remember or to forget. Subsequently, subjects’ memory of these words was tested. Finally, they assessed the words on scales of valence, arousal, sadness and fear. We found that memory performance depended on instruction as reflected in the engagement of the lateral prefrontal cortex (lateral PFC), irrespective of emotional properties of words. While the lateral PFC engagement did not differ between neutral and emotional conditions, it correlated with behavioural performance when emotional – as opposed to neutral – words were presented. A deeper understanding of the underlying brain mechanisms is likely to require a study of individual differences in cognitive abilities to suppress memory.

One-way traffic: The inferior frontal gyrus controls brain activation in the middle temporal gyrus and inferior parietal lobule during divergent thinking

Contrary to earlier approaches that focused on the contributions of isolated brain regions to the emergence of creativity, there is now growing consensus that creative thought emerges from the interaction of multiple brain regions, often embedded within larger brain networks. Specifically, recent evidence from studies of divergent thinking suggests that kernel ideas emerge in posterior brain regions residing within the semantic system and/or the default mode network (DMN), and that the prefrontal cortex (PFC) regions within the executive control network (ECN) constrain those ideas for generating outputs that meet task demands. However, despite knowing that regions within these networks exhibit interaction, to date the direction of the relationship has not been tested directly. By applying Dynamic Causal Modeling (DCM) to fMRI data collected during a divergent thinking task, we tested the hypothesis that the PFC exerts unidirectional control over the middle temporal gyrus (MTG) and the inferior parietal lobule (IPL), vs. the hypothesis that these two sets of regions exert bidirectional control over each other (in the form of feedback loops). The data were consistent with the former model by demonstrating that the right inferior frontal gyrus (IFG) exerts unidirectional control over MTG and IPL, although the evidence was somewhat stronger in the case of the MTG than the IPL. Our findings highlight potential causal pathways that could underlie the neural bases of divergent thinking.

Projecting one's own spatial bias onto others during a theory-of-mind task

Most people have an intrinsic spatial bias—many are better at processing objects to the left, whereas some are biased to the right. Here, we found that this subtle bias in one’s own awareness is mirrored in one’s ability to process what is likely to be in other people’s minds. If you are biased toward processing your own right side of space, then you may be faster at recognizing when someone else processes an object to his or her right side. One possible interpretation is that we process the space around us, and understand how others process the space around them, using at least partially shared mechanisms.

Many people show a left-right bias in visual processing. We measured spatial bias in neurotypical participants using a variant of the line bisection task. In the same participants, we measured performance in a social cognition task. This theory-of-mind task measured whether each participant had a processing-speed bias toward the right of, or left of, a cartoon agent about which the participant was thinking. Crucially, the cartoon was rotated such that what was left and right with respect to the cartoon was up and down with respect to the participant. Thus, a person’s own left-right bias could not align directly onto left and right with respect to the cartoon head. Performance on the two tasks was significantly correlated. People who had a natural bias toward processing their own left side of space were quicker to process how the cartoon might think about objects to the left side of its face, and likewise for a rightward bias. One possible interpretation of these results is that the act of processing one’s own personal space shares some of the same underlying mechanisms as the social cognitive act of reconstructing someone else’s processing of their space.

Neural Correlates of Social Inclusion in Borderline Personality Disorder

Humans engage in social interactions and have a fundamental need and motivation to establish and maintain social connections. Neuroimaging studies particularly focused on the neural substrates of social exclusion in healthy subjects (HC), borderline personality disorder (BPD), and major depression (MD). However, there is evidence regarding neural alterations also during social inclusion in BPD that we intended to elucidate in our study. Considering that patients with BPD often have comorbid MD, we investigated patients with BPD, and comorbid MD, patients with MD without BPD, and a sample of HC. By investigating these two clinical samples within one study design, we attempted to disentangle potential confounds arising by psychiatric disorder or medication and to relate neural alterations under social inclusion specifically to BPD. We investigated 48 females (15 BPD and MD, 16 MD, and 17 HC) aged between 18 and 40 years by fMRI (3T), using the established cyberball paradigm with social exclusion, inclusion, and passive watching conditions. Significant group-by-condition interaction effects (p < 0.05, FWE-corrected on cluster level) were observed within the dorsolateral (dlPFC) and dorsomedial prefrontal cortex (dmPFC), the temporo-parietal junction (TPJ), the posterior cingulate cortex (PCC), and the precuneus. Comparisons of estimated neural activations revealed that significant interaction effects were related to a relative increase in neural activations during social inclusion in BPD. In detail, we observed a significant increase in differential (social inclusion vs. passive watching) neural activation within the dmPFC and the PCC in BPD compared to both, MD and HC. However, significant interaction effects within the dlPFC and the TPJ could not specifically be linked to BPD considering that they did not differ significantly between the two clinical groups in post-hoc comparisons. Our study supports previous results on effects of social and inclusion in BPD, and provides further evidence regarding disorder specific neural alterations in BPD for brain regions associated with self-referential and mentalizing processes during social inclusion.

Gray Matter and Functional Connectivity in Anterior Cingulate Cortex are Associated with the State of Mental Silence During Sahaja Yoga Meditation

Some meditation techniques teach the practitioner to achieve the state of mental silence. The aim of this study was to investigate brain regions that are associated with their volume and functional connectivity (FC) with the depth of mental silence in long-term practitioners of Sahaja Yoga Meditation. Twenty-three long-term practitioners of this meditation were scanned using Magnetic Resonance Imaging. In order to identify the neural correlates of the depth of mental silence, we tested which gray matter volumes (GMV) were correlated with the depth of mental silence and which regions these areas were functionally connected to under a meditation condition. GMV in medial prefrontal cortex including rostral anterior cingulate cortex were positively correlated with the subjective perception of the depth of mental silence inside the scanner. Furthermore, there was significantly increased FC between this area and bilateral anterior insula/putamen during a meditation-state specifically, while decreased connectivity with the right thalamus/parahippocampal gyrus was present during the meditation-state and the resting-state. The capacity of long-term meditators to establish a durable state of mental silence inside an MRI scanner was associated with larger gray matter volume in a medial frontal region that is crucial for top-down cognitive, emotion and attention control. This is furthermore corroborated by increased FC of this region during the meditation-state with bilateral anterior insula/putamen, which are important for interoception, emotion, and attention regulation. The findings hence suggest that the depth of mental silence is associated with medial fronto-insular-striatal networks that are crucial for top-down attention and emotional control.

Supramodal effect of rightward prismatic adaptation on spatial representations within the ventral attentional system

Rightward prismatic adaptation (R-PA) was shown to alleviate not only visuo-spatial but also auditory symptoms in neglect. The neural mechanisms underlying the effect of R-PA have been previously investigated in visual tasks, demonstrating a shift of hemispheric dominance for visuo-spatial attention from the right to the left hemisphere both in normal subjects and in patients. We have investigated whether the same neural mechanisms underlie the supramodal effect of R-PA on auditory attention. Normal subjects underwent a brief session of R-PA, which was preceded and followed by an fMRI evaluation during which subjects detected targets within the left, central and right space in the auditory or visual modality. R-PA-related changes in activation patterns were found bilaterally in the inferior parietal lobule. In either modality, the representation of the left, central and right space increased in the left IPL, whereas the representation of the right space decreased in the right IPL. Thus, a brief exposure to R-PA modulated the representation of the auditory and visual space within the ventral attentional system. This shift in hemispheric dominance for auditory spatial attention offers a parsimonious explanation for the previously reported effects of R-PA on auditory symptoms in neglect.

Perception of Upright: Multisensory Convergence and the Role of Temporo-Parietal Cortex

We inherently maintain a stable perception of the world despite frequent changes in the head, eye, and body positions. Such "orientation constancy" is a prerequisite for coherent spatial perception and sensorimotor planning. As a multimodal sensory reference, perception of upright represents neural processes that subserve orientation constancy through integration of sensory information encoding the eye, head, and body positions. Although perception of upright is distinct from perception of body orientation, they share similar neural substrates within the cerebral cortical networks involved in perception of spatial orientation. These cortical networks, mainly within the temporo-parietal junction, are crucial for multisensory processing and integration that generate sensory reference frames for coherent perception of self-position and extrapersonal space transformations. In this review, we focus on these neural mechanisms and discuss (i) neurobehavioral aspects of orientation constancy, (ii) sensory models that address the neurophysiology underlying perception of upright, and (iii) the current evidence for the role of cerebral cortex in perception of upright and orientation constancy, including findings from the neurological disorders that affect cortical function.

Brain encoding of saltatory velocity through a pulsed pneumotactile array in the lower face

Processing dynamic tactile inputs is a primary function of the somatosensory system. Spatial velocity encoding mechanisms by the nervous system are important for skilled movement production and may play a role in recovery of sensorimotor function following neurological insult. Little is known about tactile velocity encoding in mechanosensory trigeminal networks required for speech, suck, mastication, and facial gesture. High resolution functional magnetic resonance imaging (fMRI) was used to investigate the neural substrates of velocity encoding in the human orofacial somatosensory system during unilateral saltatory pneumotactile stimulation of perioral and buccal hairy skin in 20 neurotypical adults. A custom multichannel, scalable pneumotactile array consisting of 7 TAC-Cells was used to present 5 stimulus conditions: 5cm/s, 25cm/s, 65cm/s, ALL-ON synchronous activation, and ALL-OFF. The spatiotemporal organization of whole-brain blood oxygen level-dependent (BOLD) response was analyzed with general linear modeling (GLM) and fitted response estimates of percent signal change to compare activations associated with each velocity, and the main effect of velocity alone. Sequential saltatory inputs to the right lower face produced localized BOLD responses in 6 key regions of interest (ROI) including; contralateral precentral and postcentral gyri, and ipsilateral precentral, superior temporal (STG), supramarginal gyri (SMG), and cerebellum. The spatiotemporal organization of the evoked BOLD response was highly dependent on velocity, with the greatest amplitude of BOLD signal change recorded during the 5cm/s presentation in the contralateral hemisphere. Temporal analysis of BOLD response by velocity indicated rapid adaptation via a scalability of networks processing changing pneumotactile velocity cues.