Perplexity of utterances in untreated first-episode psychosis: an ultra-high field MRI dynamic causal modelling study of the semantic network.

Background: Psychosis involves a distortion of thought content, which is partly reflected in anomalous ways in which words are semantically connected into utterances in speech. We sought to explore how these linguistic anomalies are realized through putative circuit-level abnormalities in the brain's semantic network.

Methods: Using a computational large-language model, Bidirectional Encoder Representations from Transformers (BERT), we quantified the contextual expectedness of a given word sequence (perplexity) across 180 samples obtained from descriptions of 3 pictures by patients with first-episode schizophrenia (FES) and controls matched for age, parental social status, and sex, scanned with 7 T ultra-high field functional magnetic resonance imaging (fMRI).

A radiofrequency coil for infants and toddlers.

Infants and toddlers are a challenging population upon which to perform magnetic resonance imaging (MRI) of the brain, both in research and clinical settings. Because of the large range in head size during the early years of development, paediatric neuro-MRI requires a radiofrequency (RF) coil, or set of coils, that is tailored to head size to provide the highest image quality. Mitigating techniques must also be employed to reduce and correct for subject motion.

Language network self-inhibition and semantic similarity in first-episode schizophrenia: A computational-linguistic and effective connectivity approach.

Introduction: A central feature of schizophrenia is the disorganization and impoverishment of language. Recently, we observed higher semantic similarity in first-episode-schizophrenia (FES) patients. In this study, we investigate if this aberrant similarity relates to the 'causal' connectivity between two key nodes of the word production system: inferior frontal gyrus (IFG) and the semantic-hub at the ventral anterior temporal lobe (vATL).

An open access resource for functional brain connectivity from fully awake marmosets.

The common marmoset (Callithrix jacchus) is quickly gaining traction as a premier neuroscientific model. However, considerable progress is still needed in understanding the functional and structural organization of the marmoset brain to rival that documented in longstanding preclinical model species, like mice, rats, and Old World primates. To accelerate such progress, we present the Marmoset Functional Brain Connectivity Resource (marmosetbrainconnectome.

Integration of an RF coil and commercial field camera for ultrahigh-field MRI.

Purpose: To develop an RF coil with an integrated commercial field camera for ultrahigh field (7T) neuroimaging. The RF coil would operate within a head-only gradient coil and be subject to the corresponding design constraints. The RF coil can thereafter be used for subject-specific correction of k-space trajectories-notably in gradient-sensitive sequences such as single-shot spiral imaging.

Simultaneous functional MRI of two awake marmosets.

Social cognition is a dynamic process that requires the perception and integration of a complex set of idiosyncratic features between interacting conspecifics. Here we present a method for simultaneously measuring the whole-brain activation of two socially interacting marmoset monkeys using functional magnetic resonance imaging. MRI hardware (a radiofrequency coil and peripheral devices) and image-processing pipelines were developed to assess brain responses to socialization, both on an intra-brain and inter-brain level.

Effects of phase regression on high-resolution functional MRI of the primary visual cortex.

High-resolution functional MRI studies have become a powerful tool to non-invasively probe the sub-millimeter functional organization of the human cortex. Advances in MR hardware, imaging techniques and sophisticated post-processing methods have allowed high resolution fMRI to be used in both the clinical and academic neurosciences. However, consensus within the community regarding the use of gradient echo (GE) or spin echo (SE) based acquisition remains largely divided.

Radiofrequency coil for routine ultra-high-field imaging with an unobstructed visual field.

Many neuroscience applications have adopted functional MRI as a tool to investigate the healthy and diseased brain during the completion of a task. While ultra-high-field MRI has allowed for improved contrast and signal-to-noise ratios during functional MRI studies, it remains a challenge to create local radiofrequency coils that can accommodate an unobstructed visual field and be suitable for routine use, while at the same time not compromise performance. Performance (both during transmission and reception) can be improved by using close-fitting coils; however, maintaining sensitivity over the whole brain often requires the introduction of coil elements proximal to the eyes, thereby partially occluding the subject's visual field.

Whole brain mapping of somatosensory responses in awake marmosets investigated with ultra-high-field fMRI.

The common marmoset () is a small-bodied New World primate that is becoming an important model to study brain functions. Despite several studies exploring the somatosensory system of marmosets, all results have come from anesthetized animals using invasive techniques and postmortem analyses. Here, we demonstrate the feasibility for getting high-quality and reproducible somatosensory mapping in awake marmosets with functional magnetic resonance imaging (fMRI).

Cortico-Subcortical Functional Connectivity Profiles of Resting-State Networks in Marmosets and Humans.

Understanding the similarity of cortico-subcortical networks topologies between humans and nonhuman primate species is critical to study the origin of network alternations underlying human neurologic and neuropsychiatric diseases. The New World common marmoset () has become popular as a nonhuman primate model for human brain function. Most marmoset connectomic research, however, has exclusively focused on cortical areas, with connectivity to subcortical networks less extensively explored.

Divergence of rodent and primate medial frontal cortex functional connectivity.

With the medial frontal cortex (MFC) centrally implicated in several major neuropsychiatric disorders, it is critical to understand the extent to which MFC organization is comparable between humans and animals commonly used in preclinical research (namely rodents and nonhuman primates). Although the cytoarchitectonic structure of the rodent MFC has mostly been conserved in humans, it is a long-standing question whether the structural analogies translate to functional analogies. Here, we probed this question using ultra high field fMRI data to compare rat, marmoset, and human MFC functional connectivity.

Elimination of low-inversion-efficiency induced artifacts in whole-brain MP2RAGE using multiple RF-shim configurations at 7 T.

The magnetization-prepared two-rapid-gradient-echo (MP2RAGE) sequence is used for structural T -weighted imaging and T mapping of the human brain. In this sequence, adiabatic inversion RF pulses are commonly used, which require the B magnitude to be above a certain threshold. Achieving this threshold in the whole brain may not be possible at ultra-high fields because of the short RF wavelength.

Frontal-striatal connectivity and positive symptoms of schizophrenia: implications for the mechanistic basis of prefrontal rTMS.

Repetitive transcranial magnetic stimulation (rTMS), when applied to left dorsolateral prefrontal cortex (LDLPFC), reduces negative symptoms of schizophrenia, but has no effect on positive symptoms. In a small number of cases, it appears to worsen the severity of positive symptoms. It has been hypothesized that high-frequency rTMS of the LDLPFC might increase the dopaminergic neurotransmission by driving the activity of the left striatum in the basal ganglia (LSTR)-increasing striatal dopaminergic activity.

Altered Resting-State Functional Connectivity Between Awake and Isoflurane Anesthetized Marmosets.

The common marmoset (Callithrix jacchus) is a New World primate that is becoming increasingly popular as a preclinical model. To assess functional connectivity (FC) across the marmoset brain, resting-state functional MRI (RS-fMRI) is often performed under isoflurane anesthesia to avoid the effects of motion, physiological stress, and training requirements. In marmosets, however, it remains unclear how isoflurane anesthesia affects patterns of FC.

Looming and receding visual networks in awake marmosets investigated with fMRI.

An object that is looming toward a subject or receding away contains important information for determining if this object is dangerous, beneficial or harmless. This information (motion, direction, identity, time-to-collision, size, velocity) is analyzed by the brain in order to execute the appropriate behavioral responses depending on the context: fleeing, freezing, grasping, eating, exploring. In the current study, we performed ultra-high-field functional MRI (fMRI) at 9.

Comparison of resting-state functional connectivity in marmosets with tracer-based cellular connectivity.

Resting-state functional MRI (RS-fMRI) is widely used to assess how strongly different brain areas are connected. However, this connection obtained by RS-fMRI, which is called functional connectivity (FC), simply refers to the correlation of blood oxygen level-dependent (BOLD) signals across time it has yet to be quantified how accurately FC reflects cellular connectivity (CC). In this study, we elucidated this relationship using RS-fMRI and quantitative tracer data in marmosets.

Task-based fMRI of a free-viewing visuo-saccadic network in the marmoset monkey.

Saccadic tasks are often used to index aberrations of cognitive function in patient populations, with several neuropsychiatric and neurologic disorders characterized by saccadic dysfunction. The common marmoset (Callithrix jacchus) has received recent attention as an additional primate model for studying the neural basis of these dysfunctions - marmosets are amenable to a host of genetic manipulation techniques and have a lissencephalic cortex, which is well suited for a variety of recording techniques (e.g.

Integrated radiofrequency array and animal holder design for minimizing head motion during awake marmoset functional magnetic resonance imaging.

Marmosets are small New World primates that are posited to become an important preclinical animal model for studying intractable human brain diseases. A critical step in the development of marmosets as a viable model for human brain dysfunction is to characterize brain networks that are homologous with human network topologies. In this regard, the use of functional magnetic resonance imaging (fMRI) holds tremendous potential for functional brain mapping in marmosets.

Exploring the limits of network topology estimation using diffusion-based tractography and tracer studies in the macaque cortex.

Reconstructing the anatomical pathways of the brain to study the human connectome has become an important endeavour for understanding brain function and dynamics. Reconstruction of the cortico-cortical connectivity matrix in vivo often relies on noninvasive diffusion-weighted imaging (DWI) techniques but the extent to which they can accurately represent the topological characteristics of structural connectomes remains unknown. We addressed this question by constructing connectomes using DWI data collected from macaque monkeys in vivo and with data from published invasive tracer studies.

Intrinsic Functional Boundaries of Lateral Frontal Cortex in the Common Marmoset Monkey.

The common marmoset () is a small New World primate species that has been recently targeted as a potentially powerful preclinical model of human prefrontal cortex dysfunction. Although the structural boundaries of frontal cortex were described in marmosets at the start of the 20th century (Brodmann, 1909) and refined more recently (Paxinos et al., 2012), the broad functional boundaries of marmoset frontal cortex have yet to be established.

Open-source hardware designs for MRI of mice, rats, and marmosets: Integrated animal holders and radiofrequency coils.

Background: Small-animal MRI is an important investigative tool for basic and preclinical research. High-resolution anatomical and functional studies of the brain require artifact-free images that are acquired with a highly sensitive radiofrequency (RF) coil.

New Method: The animal holder plays an important role in mitigating image artifacts: motion artifacts are reduced by immobilizing the animal and geometric-distortion artifacts are reduced by accurately positioning the animal to improve static-field shimming.

Intrinsic functional clustering of anterior cingulate cortex in the common marmoset.

The common marmoset (Callithrix jacchus) has garnered recent attention as a potentially powerful preclinical model and complement to other canonical mammalian models of human brain diseases (e.g., rodents and Old World non-human primates).

1H MR spectroscopy of the motor cortex immediately following transcranial direct current stimulation at 7 Tesla.

Transcranial direct current stimulation (tDCS) is a form of non-invasive brain stimulation that may modulate cortical excitability, metabolite concentration, and human behaviour. The supplementary motor area (SMA) has been largely ignored as a potential target for tDCS neurorehabilitation but is an important region in motor compensation after brain injury with strong efferent connections to the primary motor cortex (M1). The objective of this work was to measure tissue metabolite changes in the human motor cortex immediately following tDCS.

In vivo manganese tract tracing of frontal eye fields in rhesus macaques with ultra-high field MRI: Comparison with DWI tractography.

The saccadic eye movement system has emerged as a valuable model for studying neural circuitry related to flexible control of behavior. Although connections of the saccadic circuitry are well documented via histochemical tracers, these methods require fixed tissue and thus cannot provide longitudinal assessments of connectivity. To circumvent this, diffusion weighted imaging (DWI) is often used as a proxy for connectivity in vivo, allowing for the tracing of connections longitudinally and noninvasively.