Interbrain substrates of role switching during mother-child interaction.

Mother-child interaction is highly dynamic and reciprocal. Switching roles in these back-and-forth interactions serves as a crucial feature of reciprocal behaviors while the underlying neural entrainment is still not well-studied. Here, we designed a role-controlled cooperative task with dual EEG recording to explore how differently two brains interact when mothers and children hold different roles. When children were actors and mothers were observers, mother-child interbrain synchrony emerged primarily within the theta oscillations and the frontal lobe, which highly correlated with children's attachment to their mothers (self-reported by mothers). When their roles were reversed, this synchrony was shifted to the alpha oscillations and the central area and associated with mothers' perception of their relationship with their children. The results suggested an observer-actor neural alignment within the actor's oscillations, which was related to the actor-toward-observer emotional bonding. Our findings contribute to the understanding of how interbrain synchrony is established and dynamically changed during mother-child reciprocal interaction.

Changes in choroidal hemodynamics of form-deprivation myopia in Guinea pigs.

PURPOSE: We studied changes in the choroid, particularly variation in blood flow, during the development of myopia. The hemodynamic mechanism in play remains unclear. We evaluated blood flow by quantitating indocyanine green (ICG) fluorescence in a guinea pig model of form-deprivation myopia. METHODS: Guinea pigs were divided into form-deprivation myopia (FDM) and normal control (NC) groups. Ocular biometric and choroidal hemodynamics parameters were quantitatively derived via ICG imaging, and included the maximal ICG fluorescence intensity (Imax), rising time (Trising), blood flow index (BFI), and mean transit time (MTT). RESULTS: Form deprivation was associated with significant interocular differences in terms of both refractive error and axial length. ICG fluorescence hemodynamic maps of fundal blood flow and vasculature density were evident. In deprived eyes, the fluorescence signals exhibited significantly longer Trising and MTT but lower Imax and BFI than fellow eyes and NC group. The interocular differences in terms of the ocular biometric and hemodynamic parameters were significantly correlated. Hemodynamic analysis of choriocapillaris lobules revealed weakened fluorescence intensity and prolonged arrival and filling times in deprived eyes. Form deprivation reduced the number of lobulated choriocapillaris structures. CONCLUSION: Form-deprivation myopia triggered changes in the hemodynamic and vascular network structures of the choroid and choriocapillaris. The ICG fluorescence imaging/analysis method provides a unique tool for further myopia research.

The effects of pre-cue alpha and cueing strategy on age-related deficits in post-cue alpha activity and target processing during visual spatial attention.

Electroencephalography alpha-band (8-13 Hz) activity during visual spatial attention declines in normal aging. We recently reported the impacts of pre-cue baseline alpha and cueing strategy on post-cue anticipatory alpha activity and target processing in visual spatial attention (Wang et al., Cerebral Cortex, 2023). However, whether these factors affected aging effects remains unaddressed. We investigated this issue in two independent experiments (n = 114) with different cueing strategies (instructional vs. probabilistic). When median-splitting young adults (YA) by their pre-cue alpha power, we found that older adults exhibited similar pre-cue and post-cue alpha activity as YA with lower pre-cue alpha, and only YA with higher pre-cue alpha showed significant post-cue alpha activity, suggesting that diminished anticipatory alpha activity was not specific to aging but likely due to a general decrease with baseline alpha. Moreover, we found that the aging effects on cue-related event-related potentials were dependent on cueing strategy but were relatively independent of pre-cue alpha. However, age-related deficits in target-related N1 attentional modulation might depend on both pre-cue alpha and cueing strategy. By considering the impacts of pre-cue alpha and cueing strategy, our findings offer new insights into age-related deficits in anticipatory alpha activity and target processing during visual spatial attention.

The effects of pre-cue posterior alpha on post-cue alpha activity and target processing in visual spatial attention tasks with instructional and probabilistic cues.

The electroencephalography alpha-band (8-13 Hz) activity may represent a crucial neural substrate of visual spatial attention. However, factors likely contributing to alpha activity have not been adequately addressed, which impedes understanding its functional roles. We investigated whether pre-cue alpha power was associated with post-cue alpha activity in 2 independent experiments (n = 30 each) with different cueing strategies (instructional vs. probabilistic) by median-splitting subjects (between-subject) or trials (within-subject) according to pre-cue alpha. In both experiments, only subjects with higher pre-cue alpha showed significant post-cue alpha desynchronization and alpha lateralization, while whether trials had higher or lower pre-cue alpha affected post-cue alpha desynchronization but not alpha lateralization. Furthermore, significant attentional modulation of target processing indexed by N1 component was observed in subjects and trials regardless of higher or lower pre-cue alpha in the instructional cueing experiment. While in the probabilistic cueing experiment, N1 attentional modulation was only observed in higher pre-cue alpha subjects and lower pre-cue alpha trials. In summary, by demonstrating the effects of pre-cue alpha and cueing strategy on post-cue alpha activity and target processing, our results suggest the necessity of considering these 2 contributing factors when investigating the functional roles of alpha activity in visual spatial attention.

Neuroimaging prognostic factors for treatment response to motor imagery training after stroke.

The efficacy of motor imagery training for motor recovery is well acknowledged, but with substantial inter-individual variability in stroke patients. To help optimize motor imagery training therapy plans and screen suitable patients, this study aimed to explore neuroimaging biomarkers explaining variability in treatment response. Thirty-nine stroke patients were randomized to a motor imagery training group (n = 22, received a combination of conventional rehabilitation therapy and motor imagery training) and a control group (n = 17, received conventional rehabilitation therapy and health education) for 4 weeks of interventions. Their demography and clinical information, brain lesion from structural MRI, spontaneous brain activity and connectivity from rest fMRI, and sensorimotor brain activation from passive motor task fMRI were acquired to identify prognostic factors. We found that the variability of outcomes from sole conventional rehabilitation therapy could be explained by the reserved sensorimotor neural function, whereas the variability of outcomes from motor imagery training + conventional rehabilitation therapy was related to the spontaneous activity in the ipsilesional inferior parietal lobule and the local connectivity in the contralesional supplementary motor area. The results suggest that additional motor imagery training treatment is also efficient for severe patients with damaged sensorimotor neural function, but might be more effective for patients with impaired motor planning and reserved motor imagery.

Deep-learning-based 3D blood flow reconstruction in transmissive laser speckle imaging.

Transmissive laser speckle imaging (LSI) is useful for monitoring large field-of-view (FOV) blood flow in thick tissues. However, after longer transmissions, the contrast of the transmitted speckle images is more likely to be blurred by multiple scattering, resulting in decreased accuracy and spatial resolution of deep vessels. This study proposes a deep-learning-based strategy for high spatiotemporal resolution three-dimensional (3D) reconstruction from a single transilluminated laser speckle contrast image, providing more structural and functional details without multifocus two-dimensional (2D) imaging or 3D optical imaging with point/line scanning. Based on the correlation transfer equation, a large training dataset is generated by convolving vessel masks with depth-dependent point spread functions (PSF). The UNet and ResNet are used for deblurring and depth estimation. The blood flow in the reconstructed 3D vessels is estimated by a depth-dependent contrast model. The proposed method is evaluated with simulated data and phantom experiments, achieving high-fidelity structural reconstruction with a depth-independent estimation of blood flow. This fast 3D blood flow imaging technique is suitable for real-time monitoring of thick tissue and the diagnosis of vascular diseases.

Progressive increase of high-frequency EEG oscillations during meditation is associated with its trait effects on heart rate and proteomics: a study on the Tibetan Buddhist.

Meditation has been a spiritual and healing practice in the East for thousands of years. However, the neurophysiologic mechanisms underlying its traditional form remain unclear. In this study, we recruited a large sample of monks (n = 73) who practice Tibetan Buddhist meditation and compared with meditation-naive local controls (n = 30). Their electroencephalography (EEG) and electrocardiogram signals were simultaneously recorded and blood samples were collected to investigate the integrative effects of Tibetan Buddhist on brain, heart, and proteomics. We found that the EEG activities in monks shifted to a higher frequency from resting to meditation. Meditation starts with decrease of the (pre)frontal delta activity and increase of the (pre)frontal high beta and gamma activity; while at the deep meditative state, the posterior high-frequency activity was also increased, and could be specified as a biomarker for the deep meditation. The state increase of posterior high-frequency EEG activity was significantly correlated with the trait effects on heart rate and nueropilin-1 in monks, with the source of brain-heart correlation mainly locating in the attention and emotion networks. Our study revealed that the effects of Tibetan Buddhist meditation on brain, heart, and proteomics were highly correlated, demonstrating meditation as an integrative body-mind training.

Nodal Memberships to Communities of Functional Brain Networks Reveal Functional Flexibility and Individualized Connectome.

Human brain network is organized as interconnected communities for supporting cognition and behavior. Despite studies on the nonoverlapping communities of brain network, overlapping community structure and its relationship to brain function remain largely unknown. With this consideration, we employed the Bayesian nonnegative matrix factorization to decompose the functional brain networks constructed from resting-state fMRI data into overlapping communities with interdigitated mapping to functional subnetworks. By examining the heterogeneous nodal membership to communities, we classified nodes into three classes: Most nodes in somatomotor and limbic subnetworks were affiliated with one dominant community and classified as unimodule nodes; most nodes in attention and frontoparietal subnetworks were affiliated with more than two communities and classified as multimodule nodes; and the remaining nodes affiliated with two communities were classified as bimodule nodes. This three-class paradigm was highly reproducible across sessions and subjects. Furthermore, the more likely a node was classified as multimodule node, the more flexible it will be engaged in multiple tasks. Finally, the FC feature vector associated with multimodule nodes could serve as connectome "fingerprinting" to gain high subject discriminability. Together, our findings offer new insights on the flexible spatial overlapping communities that related to task-based functional flexibility and individual connectome "fingerprinting."

Neural mechanisms of inhibitory control deficits in obesity revealed by P3 but not N2 event-related potential component.

The lack of inhibitory control toward foods may cause unhealthy eating behavior and lead to obesity. However, previous research failed to reach consensus on the alterations in event-related potential (ERP) markers of inhibitory control, i.e., N2 and P3. We hypothesized that the ERP effects of inhibitory control reported in previous food-based Go/NoGo studies might be obscured by non-inhibitory processes associated with stimulus probability. We designed two food-based Go/NoGo tasks composed of stimuli with the same type and frequency of occurrence (60% non-foods, 20% high-calorie foods, 20% low-calorie foods), one with response inhibition toward high- and the other toward low-calorie foods. Such an experimental design allowed us to isolate neural activity associated with inhibitory control from that associated with non-inhibitory processes by constructing ERP difference waves between NoGo and Go trials with the same frequency of occurrence. Electroencephalography data were collected from 32 obese participants and 29 normal-weight controls. Obese participants showed significantly lower accuracy in NoGo trials than normal-weight controls in both tasks. ERP data suggested inhibition-related effects for P3 (P3d) but not N2 in the difference waves, and obese participants showed significantly decreased P3d amplitudes than normal-weight controls in both tasks. In addition, we found that across both groups, individuals with larger waist-to-hip ratios showed smaller P3d amplitudes in both tasks, while such correlations between body mass index and P3d amplitude were only observed in the high-calorie task. Our findings suggest that the decreased effect of P3, not N2, might reflect the neural substrate of inhibitory control deficits in obese people. Thus, P3 could serve as an important neural marker in the future development of new therapeutic strategy that aims to improve inhibitory control in obesity.

Brain-Heart Interactions Underlying Traditional Tibetan Buddhist Meditation.

Despite accumulating evidence suggesting improvement in one's well-being as a result of meditation, little is known about if or how the brain and the periphery interact to produce these behavioral and mental changes. We hypothesize that meditation reflects changes in the neural representations of visceral activity, such as cardiac behavior, and investigated the integration of neural and visceral systems and the spontaneous whole brain spatiotemporal dynamics underlying traditional Tibetan Buddhist meditation. In a large cohort of long-term Tibetan Buddhist monk meditation practitioners, we found distinct transient modulations of the neural response to heartbeats in the default mode network (DMN), along with large-scale network reconfigurations in the gamma and theta bands of electroencephalography (EEG) activity induced by meditation. Additionally, temporal-frontal network connectivity in the EEG theta band was negatively correlated with the duration of meditation experience, and gamma oscillations were uniquely, directionally coupled to theta oscillations during meditation. Overall, these data suggest that the neural representation of cardiac activity in the DMN and large-scale spatiotemporal network integrations underlie the fundamental neural mechanism of meditation and further imply that meditation may utilize cortical plasticity, inducing both immediate and long-lasting changes in the intrinsic organization and activity of brain networks.

Decoding attention control and selection in visual spatial attention.

Event-related potentials (ERPs) are used extensively to investigate the neural mechanisms of attention control and selection. The univariate ERP approach, however, has left important questions inadequately answered. We addressed two questions by applying multivariate pattern classification to multichannel ERPs in two cued visual spatial attention experiments (N = 56): (a) impact of cueing strategies (instructional vs. probabilistic) on attention control and selection and (b) neural and behavioral effects of individual differences. Following cue onset, the decoding accuracy (cue left vs. cue right) began to rise above chance level earlier and remained higher in instructional cueing (~80 ms) than in probabilistic cueing (~160 ms), suggesting that unilateral attention focus leads to earlier and more distinct formation of the attention control set. A similar temporal sequence was also found for target-related processing (cued target vs. uncued target), suggesting earlier and stronger attention selection under instructional cueing. Across the two experiments: (a) individuals with higher cue-related decoding accuracy showed higher magnitude of attentional modulation of target-evoked N1 amplitude, suggesting that better formation of anticipatory attentional state leads to stronger modulation of target processing, and (b) individuals with higher target-related decoding accuracy showed faster reaction times (or larger cueing effects), suggesting that stronger selection of task-relevant information leads to better behavioral performance. Taken together, multichannel ERPs combined with machine learning decoding yields new insights into attention control and selection that complement the univariate ERP approach, and along with the univariate ERP approach, provides a more comprehensive methodology to the study of visual spatial attention.

Enhancing neural efficiency of cognitive processing speed via training and neurostimulation: An fNIRS and TMS study.

Speed of Processing (SoP) represents a fundamental limiting step in cognitive performance which may underlie General Intelligence. The measure of SoP is particularly sensitive to aging, neurological or cognitive diseases, and has become a benchmark for diagnosis, cognitive remediation, and enhancement. Neural efficiency of the Dorsolateral Prefrontal Cortex (DLPFC) is proposed to account for individual differences in SoP. However, the mechanisms by which DLPFC efficiency is shaped by training and whether it can be enhanced remain elusive. To address this, we monitored the brain activity of sixteen healthy participants using functional Near Infrared Spectroscopy (fNIRS) while practicing a common SoP task (Symbol Digit Substitution Task) across 4 sessions. Furthermore, in each session, participants received counterbalanced excitatory repetitive transcranial magnetic stimulation (rTMS) during mid-session breaks. Results indicate a significant involvement of the left-DLPFC in SoP, whose neural efficiency is consistently increased through task practice. Active neurostimulation, but not Sham, significantly enhanced the neural efficiency. These findings suggest a common mechanism by which neurostimulation may aid to accelerate learning.

Hemodynamic effects of intraoperative anesthetics administration in photothrombotic stroke model: a study using laser speckle imaging.

BACKGROUND: Previous neuroimaging studies have shown the hemodynamic effect of either preconditioning or postconditioning anesthesia in ischemic stroke model. However, the anesthetic effect in hemodynamics during and immediately after the stroke modeling surgery remains unknown due to the lack of appropriate anesthesia-free stroke model and intraoperative imaging technology. In the present study, we utilized our recently developed photothrombotic model of focal cerebral ischemia in conscious and freely moving rats, and investigated transient hemodynamic changes with or without isoflurane administration. Laser speckle imaging was applied to acquire real-time two-dimensional full-field cerebral blood flow (CBF) information throughout the surgical operations and early after. RESULTS: Significantly larger CBF reduction area was observed in conscious rats from 8 min immediately after the onset of stroke modeling, compared with anesthetized rats. Stroke rats without isoflurane administration also showed larger lesion volume identified by magnetic resonance imaging 3 h post occlusion (58.9%), higher neurological severity score 24 h post occlusion (28.3%), and larger infarct volume from 2,3,5-triphenyltetrazolium chloride staining 24 h post occlusion (46.9%). CONCLUSIONS: Our results demonstrated that the hemodynamic features were affected by anesthetics at as early as during the stroke induction. Also, our findings about the neuroprotection of intraoperative anesthetics administration bring additional insights into understanding the translational difficulty in stroke research.

Altered intrinsic insular activity predicts symptom severity in unmedicated obsessive-compulsive disorder patients: a resting state functional magnetic resonance imaging study.

BACKGROUND: Previous neuroimaging data indicated that the dysfunction in cortico-striato-thalamo-cortical (CSTC) circuit contributed to the neuropathological mechanism of obsessive-compulsive disorder (OCD). Whereas, emerging work has shown that the pathophysiology of OCD might be related to more widely distributed large-scale brain systems including limbic system and the salience network. This study aims to investigate the aberrant spontaneous neuronal activity within the whole brain, and its association with the symptom severity for unmedicated OCD patients. METHOD: Twenty-eight unmedicated OCD adults and twenty-eight matched healthy controls were recruited for a resting state functional magnetic resonance imaging (fMRI) study. The amplitude of low-frequency fluctuation (ALFF) analysis over whole brain was performed to examine the intrinsic cerebral activity of subjects. In addition, we conducted the voxel-based Pearson's correlative analysis to probe into the relationship between ALFF values and symptom severity for OCD patients. RESULTS: Our results showed that OCD patients had increased ALFF measures in the left frontopolar cortex and left orbital frontal cortex (OFC), with decreased ALFF values in the right insula. Moreover, the right insular intrinsic activity was significantly correlated with total YBOCS score (r = 0.611, p = 0.002) and compulsion score (r = 0.640, p = 0.001) for OCD patients. CONCLUSION: The results showed abnormal intrinsic neuronal activity within CSTC circuit and salience network of OCD patients. Our finding of aberrant insular activity advanced the understanding of OCD pathophysiology beyond the traditional CSTC circuit. To the best of our knowledge, it is the first finding about a reduced insular activity at the resting state for unmedicated OCD patients, which might serve as an informative biomarker for OCD pathophysiology.

Plastic Change along the Intact Crossed Pathway in Acute Phase of Cerebral Ischemia Revealed by Optical Intrinsic Signal Imaging.

The intact crossed pathway via which the contralesional hemisphere responds to the ipsilesional somatosensory input has shown to be affected by unilateral stroke. The aim of this study was to investigate the plasticity of the intact crossed pathway in response to different intensities of stimulation in a rodent photothrombotic stroke model. Using optical intrinsic signal imaging, an overall increase of the contralesional cortical response was observed in the acute phase (≤48 hours) after stroke. In particular, the contralesional hyperactivation is more prominent under weak stimulations, while a strong stimulation would even elicit a depressed response. The results suggest a distinct stimulation-response pattern along the intact crossed pathway after stroke. We speculate that the contralesional hyperactivation under weak stimulations was due to the reorganization for compensatory response to the weak ipsilateral somatosensory input.

Normal aging selectively diminishes alpha lateralization in visual spatial attention.

EEG studies of cue-induced visual alpha power (8-13 Hz) lateralization have been conducted on young adults without examining differences that may develop as a consequence of normal aging. Here, we examined age-related differences in spatial attention by comparing healthy older and younger adults. Our key finding is that cue-induced alpha power lateralization was observed in younger, but not older adults, even though both groups exhibited classic event-related potential signatures of spatial orienting. Specifically, both younger and older adults showed significant early directing-attention negativity (EDAN), anterior directing-attention negativity (ADAN), late directing-attention positivity (LDAP) and contingent negative variation (CNV). Furthermore, target-evoked sensory components were enhanced for attended relative to unattended targets in both younger and older groups. This pattern of results suggests that although older adults can successfully allocate spatial attention, they do so without the lateralization of alpha power that is commonly observed in younger adults. Taken together, our findings demonstrate that younger and older adults might engage different neural mechanisms for attentional orienting, and that alpha power lateralization during visual spatial attention is a phenomenon that diminishes during normal aging.

Single-trial estimation of the cerebral metabolic rate of oxygen with imaging photoplethysmography and laser speckle contrast imaging.

Cortical cerebral metabolic rate of oxygen (CMRO(2)) could conventionally be measured by combining laser Doppler flowmetry and multispectral reflectance imaging across multiple trials of stimulation, which compromises the real-time capacity. Monitoring transient change of CMRO(2) has been challenging. In this Letter, imaging photoplethysmography (iPPG) and laser speckle contrast imaging were combined into a multi-modal optical imaging system for single-trial estimation of CMRO(2). In a physiologically stable experiment, the iPPG-based method showed a less than 4% variance in comparison with the conventional method over 20 trials, and its temporal stability could be comparable to that by conventional method over 6 trials. While the oxygen supply was decreased deliberately, the new method was able to detect the transient changes of CMRO(2) in real time, which could not be revealed by the conventional method.

Directly measuring absolute flow speed by frequency-domain laser speckle imaging.

Laser speckle contrast imaging (LSCI) is a simple yet powerful tool to image blood flow. However, traditional LSCI has limited quantitative analysis capabilities due to various factors affecting flow speed evaluation, including illumination intensity, scattering from static tissues, and mathematical complexity of blood flow estimation. Here, we present a frequency-domain laser speckle imaging (FDLSI) method that can directly measure absolute flow speed. In phantom experiments, the measured flow speed agreed well with the preset actual values (10% deviation). Furthermore, in vivo experiments demonstrated that FDLSI was minimally affected by illumination condition changes.

Willed Attentional Selection of Visual Features: An EEG Study.

Visual selective attention studies generally tend to apply cuing paradigms to instructively direct observers' attention to certain locations, features or objects. However, in real situations, attention in humans often flows spontaneously without any specific instructions. Recently, a concept named "willed attention" was raised in visuospatial attention, in which participants are free to make volitional attention decisions. Several ERP components during willed attention were found, along with a perspective that ongoing alpha activity may bias the subsequent attentional choice. However, it remains unclear whether similar neural mechanisms exist in feature- or object-based willed attention. Here, we included choice cues and instruct cues in a feature-based selective attention paradigm, allowing participants to freely choose or to be instructed to attend a color for the subsequent target detection task. Pre-cue ongoing alpha oscillations, cue-evoked potentials and target-related steady-state visual evoked potentials (SSVEPs) were simultaneously measured as markers of attentional processing. As expected, SSVEP responses were similarly modulated by attention between choice and instruct cue trials. Similar to the case of spatial attention, a willed-attention component (Willed Attention Component, WAC) was isolated during the cue-related choice period by comparing choice and instruct cues. However, pre-cue ongoing alpha oscillations did not predict the color choice (yellow vs blue), as indicated by the chance level decoding accuracy (50%). Overall, our results revealed both similarities and differences between spatial and feature-based willed attention, and thus extended the understanding toward the neural mechanisms of volitional attention.

Low intensity transcranial ultrasound stimulation induces hemodynamic responses through neurovascular coupling.

Collective studies have demonstrated that transcranial ultrasound stimulation (TUS) can elicit activation in hemodynamics, implying its potential in treating cerebral or peripheral vessel-related malfunction. The theory for hemodynamic response to TUS is neurovascular coupling (NVC) following the ultrasound-induced cellular (de)polarization. However, it was not conclusive due to the co-existence of the pathway of direct ultrasound-vessel interactions. This study thus aims to investigate and provide direct evidence for NVC pathway in a rodent model of TUS by inhibiting neural activity with sodium valproate (VPA), a GABAergic agent. Twenty Sprague-Dawley rats were randomly assigned to VPA and Saline groups. Microelectrode and optical imaging were utilized to record local field potential and relative cerebral blood flow (rCBF) during baseline, before, and after TUS periods. We found the attenuated neural activity was associated with reduced rCBF responses. These results provided direct evidence for the presence of NVC pathway in hemodynamic modulation by TUS.