Aberrant global and local dynamic properties in schizophrenia with instantaneous phase method based on Hilbert transform

Background Emerging functional imaging studies suggest that schizophrenia is associated with aberrant spatiotemporal interaction which may result in aberrant global and local dynamic properties. Methods We investigated the dynamic functional connectivity (FC) by using instantaneous phase method based on Hilbert transform to detect abnormal spatiotemporal interaction in schizophrenia. Based on resting-state functional magnetic resonance imaging, two independent datasets were included, with 114 subjects from COBRE [51 schizophrenia patients (SZ) and 63 healthy controls (HCs)] and 96 from OpenfMRI (36 SZ and 60 HCs). Phase differences and instantaneous coupling matrices were firstly calculated at all time points by extracting instantaneous parameters. Global [global synchrony and intertemporal closeness (ITC)] and local dynamic features [strength of FC (sFC) and variability of FC (vFC)] were compared between two groups. Support vector machine (SVM) was used to estimate the ability to discriminate two groups by using all aberrant features. Results We found SZ had lower global synchrony and ITC than HCs on both datasets. Furthermore, SZ had a significant decrease in sFC but an increase in vFC, which were mainly located at prefrontal cortex, anterior cingulate cortex, temporal cortex and visual cortex or temporal cortex and hippocampus, forming significant dynamic subnetworks. SVM analysis revealed a high degree of balanced accuracy (85.75%) on the basis of all aberrant dynamic features. Conclusions SZ has worse overall spatiotemporal stability and extensive FC subnetwork lesions compared to HCs, which to some extent elucidates the pathophysiological mechanism of schizophrenia, providing insight into time-variation properties of patients with other mental illnesses.

Fluctuations in functional connectivity associated with interictal epileptiform discharges (IEDs) in intracranial EEG

All epilepsies are defined by a propensity for recurrent seizures, characterized by hypersynchronous electrographic activity. Understanding this overarching property would be advanced by a thorough quantification of how the global synchrony of the epileptic brain responds to small perturbations that do not trigger seizures. Here, we leverage analysis of transient focal bursts of epileptiform activity, termed interictal epileptiform discharges (IEDs), to characterize this response. Specifically, we use a group of 145 participants implanted with intracranial EEG (iEEG) electrodes to quantify changes in 5 functional connectivity measures associated with three properties of IEDs: their presence, spread, and number. We perform this analysis in 5 frequency bands in order to contextualize our findings in relation to ongoing neural processes at different spatial and temporal scales. We find that, across frequency bands, both the presence and spread of IEDs tend to lead to independent increases of functional connectivity, but only in functional connectivity measures influenced by the amplitude, rather than the phase, of a signal. We find that these increases are not explained by simple subgroups of connections, such as the weakest connections in the brain, or only connections within the seizure onset zone. Evaluating patterns of similarity across different bands and measure combinations, we find that the presence of IEDs impacts high frequencies (gamma and high gamma)and low frequencies (theta, alpha, and beta) differently, although responses within each group are similar. Using grouped LASSO regression, we identify which individual-level features explain differences in functional connectivity changes associated with IEDs. While no single feature robustly explains observed differences, the most consistently included predictor across bands and measures is the anatomical locus of IEDs. Overall, this work provides compelling evidence for increases in global synchrony associated with IEDs, and delivers a thorough exploration of different functional connectivity measures, frequency bands, and IED properties. These observations show a disruption of several types of ongoing neural dynamics associated with IEDs. Additionally, we provide a starting point for future models of how small perturbations affect neural systems and how those systems support the hypersynchrony seen in epilepsy.

Neural and subjective effects of inhaled N,N-dimethyltryptamine in natural settings

Background: N,N-dimethyltryptamine is a short-acting psychedelic tryptamine found naturally in many plants and animals. Few studies to date have addressed the neural and psychological effects of N,N-dimethyltryptamine alone, either administered intravenously or inhaled in freebase form, and none have been conducted in natural settings. Aims: Our primary aim was to study the acute effects of inhaled N,N-dimethyltryptamine in natural settings, focusing on questions tuned to the advantages of conducting field research, including the effects of contextual factors (i.e. “set“ and “setting“), the possibility of studying a comparatively large number of subjects, and the relaxed mental state of participants consuming N,N-dimethyltryptamine in familiar and comfortable settings. Methods: We combined state-of-the-art wireless electroencephalography with psychometric questionnaires to study the neural and subjective effects of naturalistic N,N-dimethyltryptamine use in 35 healthy and experienced participants. Results: We observed that N,N-dimethyltryptamine significantly decreased the power of alpha (8–12 Hz) oscillations throughout all scalp locations, while simultaneously increasing power of delta (1–4 Hz) and gamma (30–40 Hz) oscillations. Gamma power increases correlated with subjective reports indicative of some features of mystical-type experiences. N,N-dimethyltryptamine also increased global synchrony and metastability in the gamma band while decreasing those measures in the alpha band. Conclusions: Our results are consistent with previous studies of psychedelic action in the human brain, while at the same time the results suggest potential electroencephalography markers of mystical-type experiences in natural settings, thus highlighting the importance of investigating these compounds in the contexts where they are naturally consumed.

Neural and subjective effects of inhaled DMT in natural settings

BackgroundN,N-Dimethyltryptamine (DMT) is a short acting psychedelic tryptamine found naturally in many plants and animals. Few studies to date addressed the neural and psychological effects of DMT alone, either administered intravenously or inhaled in freebase form, and none conducted in natural settings.AimsOur primary aim was to study the acute effects of inhaled DMT in natural settings, focusing on questions tuned to the advantages of conducting field research, including the effects of contextual factors (i.e. “set” and “setting”), the possibility of studying a comparatively large number of subjects, and the relaxed mental state of participants consuming DMT in familiar and comfortable settings.MethodsWe combined state-of-the-art wireless electroencephalography (EEG) with psychometric questionnaires to study the neural and subjective effects of naturalistic DMT use in 35 healthy and experienced participants.ResultsWe observed that DMT significantly decreased the power of alpha (8-12 Hz) oscillations throughout all scalp locations, while simultaneously increasing power of delta (1-4 Hz) and gamma (30-40 Hz) oscillations. Gamma power increases correlated with subjective reports indicative of mystical-type experiences. DMT also increased/decreased global synchrony and metastability in the gamma/alpha band, and resulted in widespread increases in signal complexity.ConclusionsOur results are consistent with previous studies of psychedelic action in the human brain, while at the same time suggesting potential EEG markers of mystical-type experiences in natural settings, thus highlighting the importance of investigating these compounds in the contexts where they are naturally consumed.

Comparing nonconscious nonverbal synchrony in racially concordant and racially discordant oncology interactions.

169 Background: Communication in racially discordant (Black patient, non-Black physician) oncology interactions, which constitute about 80% of Black patients’ interactions, is generally poorer than in racially concordant interactions, and likely contributes to treatment disparities. However, the nonverbal behaviors that contribute to this problem are largely unknown. We examined nonverbal synchrony, or the nonconscious coordination of movement, which can reflect relationship quality. We hypothesized that racially discordant interactions will have lower levels of nonverbal synchrony. Methods: Data include video recordings of 68 Black patients and 163 White patients discussing treatment with their non-Black oncologists. Recordings were submitted to motion detection software to measure nonverbal synchrony. This software measures global synchrony (all correlated motion), peak synchrony (all positively correlated motion), who is leading the interaction (similar to who is leading in ballroom dancing), and how much synchrony occurs based on who is leading the interaction. Using multi-level models, we investigated whether nonverbal synchrony differed in racially concordant and racially discordant dyads. Results: Findings showed greater levels of global synchrony (p < .05) and greater peak synchrony (p < .05) in racially discordant interactions compared to racially concordant interactions. Global synchrony was the same in racially concordant interactions regardless of who was leading, but greater global synchrony occurred in racially discordant interactions when the patient was leading (p < .05). Conclusions: This is the first study to use a dynamic jointly determined measure of behavior to assess oncology interactions. Contrary to our hypothesis, nonverbal synchrony was greater in racially discordant interactions than in racially concordant interactions. Patients are driving more of the synchrony in racially discordant interactions. This may suggest that patients in racially discordant interactions adapt to their physicians to bridge racial differences. Findings could contribute to physician training to enhance coordination and outcomes in oncology interactions.

Frequency-dependent organization of the brain’s functional network through delayed-interactions

The structure of the brain network shows modularity at multiple spatial scales. The effect of the modular structure on the brain dynamics has been the focus of several studies in recent years but many aspects remain to be explored. For example, it is not well-known how the delays in the transmission of signals between the neurons and the brain regions, interact with the modular structure to determine the brain dynamics. In this paper, we show an important impact of the delays on the collective dynamics of the brain network with modular structure; that is, the degree of the synchrony between different brain regions is dependent on the frequency. In particular, we show that increasing the frequency the network transits from a global synchrony state to an asynchronous state, through a transition region over which the local synchrony inside the modules is stronger than the global synchrony. When the delays are dependent on the distance between the nodes, the modular structure of different spatial scales appears in the correlation matrix over different specific frequency bands, so that, finer spatial modular structure reveal in higher frequency bands. The results are justified by a simple theoretical argument and elaborated by simulations on several simplified modular networks and the connectome with different spatial resolutions.

Comparing nonverbal synchrony in racially concordant and racially discordant oncology interactions.

11525 Background: Communication in racially discordant (Black patient, non-Black physician) oncology interactions, which constitute about 80% of Black patients’ interactions, is generally poorer than in racially concordant interactions, and likely contributes to treatment disparities. However, the nonverbal behaviors that contribute to this problem are largely unknown. We examined nonverbal synchrony, or the nonconscious coordination of movement, which can reflect relationship quality. We hypothesized that racially discordant interactions will have lower levels of nonverbal synchrony. Methods: Data include video recordings of 68 Black patients and 163 White patients discussing treatment with their non-Black oncologists. Recordings were submitted to motion detection software to measure nonverbal synchrony. This software measures global synchrony (all correlated motion), peak synchrony (all positively correlated motion), who is leading the interaction (similar to who is leading in ballroom dancing), and how much synchrony occurs based on who is leading the interaction. Using multi-level models, we investigated whether nonverbal synchrony differed in racially concordant and racially discordant dyads. Results: Findings showed greater levels of global synchrony (p < .05) and greater peak synchrony (p < .05) in racially discordant interactions compared to racially concordant interactions. Global synchrony was the same in racially concordant interactions regardless of who was leading, but greater global synchrony occurred in racially discordant interactions when the patient was leading (p < .05). Conclusions: This is the first study to use a dynamic jointly determined measure of behavior to assess oncology interactions. Contrary to our hypothesis, nonverbal synchrony was greater in racially discordant interactions than in racially concordant interactions. It appears patients are driving more of the synchrony in racially discordant interactions. This may suggest that patients in racially discordant interactions adapt to their physicians to bridge racial differences. Findings could contribute to physician training to enhance coordination and outcomes in oncology interactions.

Phase response theory explains cluster formation in sparsely but strongly connected inhibitory neural networks and effects of jitter due to sparse connectivity

We show how to predict whether a neural network will exhibit global synchrony (a one-cluster state) or a two-cluster state based on the assumption of pulsatile coupling and critically dependent upon the phase response curve (PRC) generated by the appropriate perturbation from a partner cluster. Our results hold for a monotonically increasing (meaning longer delays as the phase increases) PRC, which likely characterizes inhibitory fast-spiking basket and cortical low-threshold-spiking interneurons in response to strong inhibition. Conduction delays stabilize synchrony for this PRC shape, whereas they destroy two-cluster states, the former by avoiding a destabilizing discontinuity and the latter by approaching it. With conduction delays, stronger coupling strength can promote a one-cluster state, so the weak coupling limit is not applicable here. We show how jitter can destabilize global synchrony but not a two-cluster state. Local stability of global synchrony in an all-to-all network does not guarantee that global synchrony can be observed in an appropriately scaled sparsely connected network; the basin of attraction can be inferred from the PRC and must be sufficiently large. Two-cluster synchrony is not obviously different from one-cluster synchrony in the presence of noise and may be the actual substrate for oscillations observed in the local field potential (LFP) and the electroencephalogram (EEG) in situations where global synchrony is not possible. Transitions between cluster states may change the frequency of the rhythms observed in the LFP or EEG. Transitions between cluster states within an inhibitory subnetwork may allow more effective recruitment of pyramidal neurons into the network rhythm. NEW & NOTEWORTHY We show that jitter induced by sparse connectivity can destabilize global synchrony but not a two-cluster state with two smaller clusters firing alternately. On the other hand, conduction delays stabilize synchrony and destroy two-cluster states. These results hold if each cluster exhibits a phase response curve similar to one that characterizes fast-spiking basket and cortical low-threshold-spiking cells for strong inhibition. Either a two-cluster or a one-cluster state might provide the oscillatory substrate for neural computations.