While decreasing negative attitudes against outgroups are often reported by individuals themselves, biased behaviour prevails. This gap between words and actions may stem from unobtrusive mental processes that could be uncovered by using neuroimaging in addition to self-reports. In this study we investigated whether adding neuroimaging to a traditional intergroup bias measure could detect intersubject differences in intergroup bias processes in a societal context where opposing discrimination is normative. In a sample of 43 Finnish students, implicit behavioural measures failed to indicate intergroup bias against Middle Eastern and Muslim immigrants, and explicit measures reported rather positive attitudes and sentiments towards that targeted group. Yet, while implementing a repeatedly validated method for detecting intergroup bias, an implicit association paradigm presenting stereotypical ingroup and outgroup face stimuli while undergoing magnetoencephalography, we detected a clear neural difference between two experimental conditions. The neural effect is thought to reflect intergroup bias in the valence of the associations that faces evoke. The activity cluster of the neural bias peaked in BA37 and included significant activity in the fusiform gyrus, which has been repeatedly found to be active during face perception bias. Importantly, this neural pattern was driven by participants who were explicitly favourable of immigration - but to a lesser extent than others. These findings suggest that such variations in explicit support of immigration are associated with the differential neural sensitivity to the congruency of associations between intergroup faces and valence. This research showcases the potential of neuroimaging to unravel covert perceptual bias against outgroup members and its sensitivity to small variations in explicit attitudes.

Persisting symptoms after concussion (PSaC) represent a complex and poorly understood neuropsychiatric phenomenon with limited treatment options. Neural network dysfunction has been associated with PSaC, and neuromodulation, particularly repetitive transcranial magnetic stimulation, may be a promising intervention. However, neuroimaging findings have been inconsistent, limiting understanding of underlying network dysfunction. We aimed to identify a core neural network associated with PSaC and explore whether this network could yield candidate cortical targets for neuromodulation at the individual level. We hypothesized that differences in network disruption would be evident between individuals with high versus low symptom burden in PSaC. Here we show that a convergent multi-analytic approach combining symptom-activation maps generated from existing fMRI datasets, systematic review of resting-state fMRI studies of PSaC, and network-based meta-analysis of coordinates derived from these studies co-localize to the salience network in high symptom burden PSaC. Using Human Connectome Project data, we mapped this network to cortical regions that could serve as individualized targets for neuromodulation. This aligns with current clinical models of PSaC and may present a new direction for network-based therapy.

Purpose: Concurrent electroencephalography (EEG) and functional magnetic resonance imaging (fMRI) have been used to assist in the presurgical localization of seizure foci in people with epilepsy. Our study aimed to examine the clinical feasibility of an optimized concurrent EEG-fMRI protocol. Methods: The optimized protocol employed a fast-fMRI sequence (sampling rate = 10 Hz) with a spare arrangement, which allowed a time window of 1.9 s for EEG recording without radio frequency noise. Patients with a diagnosis of drug-resistant epilepsy who were candidates for surgical intervention were enrolled and underwent concurrent EEG-fMRI studies to map fMRI blood oxygen level-dependent (BOLD) signal changes related to interictal epileptiform discharges. The BOLD signals were compared to those in the epileptogenic zone determined by resective cavities or radiofrequency thermocoagulation lesions. Postoperative seizure outcomes were classified according to the ILAE classification. Results: The EEG-related BOLD results indicated that 15 of the 19 patients (78.9 %) had concordant findings in the epileptogenic zone determined by surgical intervention. The percentage of patients who achieved good surgical outcomes was significantly greater in the concordant group than in the discordant group (n = 9, 60.0 % vs. n = 0, 0 %, p = 0.033). Conclusions: Using fast MRI scan, the optimized protocol provides satisfactory accuracy (78.9 %) for detecting epileptogenic zones. A concordant BOLD signal and epileptogenic zone can predict good surgical outcomes.

RATIONALE:Focused ultrasound (FUS) in combination with intravenous microbubbles is being studied clinically for modulation of the blood-brain barrier. Contrast-enhanced MRI can be used to visualize the enhanced permeability resulting from the treatment. However, contrast enhancement in the white matter (WM) are inconsistently observed compared to the gray matter (GM). Intrinsic tissue differences are believed to result in reduced treatment efficacy and insufficient drug delivery to the WM. In this study we evaluate the deposition of MRI contrast and clinically relevant antineoplastics in GM and WM tissues following single and repeated FUS and microbubble treatments. METHODS:The brains of Fischer-344 rats (n = 24) and Yorkshire pigs (n = 6) underwent FUS (rats: 580 kHz; pigs: 220 kHz) treatments targeting the internal capsule and thalamus, repeated at 30-min intervals. Definity microbubbles (rats: 20 μL/kg bolus; pigs: 4 μL/kg/5-min infusion) were administered intravenously for each sonication with MRI contrast to measure gadolinium-mediated signal change. Feedback-controlled algorithms were used to monitor treatments and modulate the pressure based on emitted microbubble signals to ensure safe and effective exposures. The delivery of methotrexate (MTX; 454.4 Da) and bevacizumab (BVZ; 149 kDa) was evaluated via immunofluorescence microscopy in rats, and respectively quantified via liquid chromatography mass spectrometry and enzyme-linked immunosorbent assay in pigs. RESULTS:Repeated FUS exposures successfully increased the vascular permeability of both gray and white matter tissues to MRI contrast and drugs of both small and large molecular sizes. In rats, single treatments showed statistically significant higher enhancements in the GM (23.5 ± 4.3 %; WM: 4.68 ± 3.75 %), however following a second sonication there were no between-tissue differences (GM: 38.0 ± 6.4 %; WM: 34.0 ± 8.7 %). In pigs, the smaller focus size relative to the brain enabled separate targeting of GM vs WM and the treatment controller used higher average power level in the WM to achieve the same cavitation dose. This resulted in no difference in gray and white matter permeability levels (to both contrast and pharmacological agents) after a single sonication. Repeated treatments sustained MRI enhancements for a longer time and enhanced drug deposition (MTX increased 6.5 and 8.3 folds after single and repeated treatment; BVZ increased 6.8 and 20.4 folds respectively). CONCLUSIONS:Feedback-controlled algorithms and the possibility to individually target gray and white matter highlighted the impact of tissue composition on treatment outcomes. Repeated FUS-mediated modulation of the brain microvasculature achieved higher levels of permeabilization to contrast and pharmacological agents in both gray and white matter.

Individualized transcranial magnetic stimulation (TMS) targeting using functional connectivity analysis of functional magnetic resonance imaging (fMRI) has been demonstrated to be advantageous in inducing neuroplasticity. However, how this approach can benefit modulating the episodic memory function supported by the hippocampal network remains elusive. We use the resting-state fMRI data from a large cohort to reveal tentative TMS targets at cortical regions within the hippocampal network. Functional MRI from 1,133 individuals in the Human Connectome Project was used to analyze the hippocampal network using seed-based functional connectivity. Using a weighted sum of time series at the cortex, we identified the average centroids of individualized targets at the medial prefrontal cortex (mPFC) and posterior parietal cortices (PPCs) at (-10, 49, 7) and (-40, -67, 30) in the left hemisphere, respectively. The mPFC and PPC coordinate at the right hemispheres are (11, 51, 6) and (48, -59, 24) in the right hemisphere, respectively. Centroids of the individualized functional connectivity at the mPFC and PPC were reproducible between sessions with separations in average about 2 and 4 mm, respectively. These separations were significantly smaller than the distance to average functional connectivity centroids (~10 mm) and atlas coordinate (~20 mm). These coordinates can be reliably identified (> 90% of individuals) using cortical "seedmaps." Our results suggest candidate TMS target coordinates to modulate the hippocampal function.

The thalamus has extensive inter-connectedness with different brain regions in serving cognitive processes. In a community-dwelling aging population from the United Kingdom, this study examined the independent contribution of thalamus volume loss to cognitive performances and the longitudinal anatomical relationship between the thalamus and the interconnected hippocampus. We accessed MRI data from 4348 cognitively unimpaired older adults from the UK Biobank, of whom 653 participants had follow-up MRI. We estimated regional brain volumes using T1-weighted MRI. Linear models tested the association between the thalamus volume and a cognitive composite score derived from digit-symbol substitution and trail-making tests. We used latent change score models to test the longitudinal associations between thalamus volume at baseline and the trajectory of hippocampal atrophy, and vice versa. Baseline thalamus volume was positively associated with the cognitive composite score ( β = 0.055 ± 0.018 , P = 0.002, R 2 = 0.09). A larger baseline thalamus volume predicted slower hippocampal atrophy ( γ T → dH = - 0.048 ± 0.015 , P = 0.001 , R 2 = 0.09 ), while larger hippocampal volume at baseline predicted faster thalamic atrophy ( γ H → d T = 0.043 ± 0.022 , P = 0.048 , R 2 = 0.04 ). Sex-stratified analysis revealed that hippocampal volume significantly predicted thalamic atrophy only in women. This study revealed that thalamic volume loss was associated with impaired processing speed and executive function. Thalamus and hippocampus anatomy showed bidirectional longitudinal associations and demonstrated sex differences. These findings underscore the thalamus anatomy as an important marker of brain health in the aging population.

Children with attention-deficit hyperactivity disorder (ADHD) have difficulties in social interactions. Studying brain activity during social interactions is difficult with conventional artificial stimuli. This pioneering study examined the neural correlates of social perception in children with ADHD and matched controls using naturalistic stimuli. We presented 20 children with ADHD and 20 age-and-sex-matched controls with tailored movies featuring high- or low-level social interactions while recording electroencephalographic signals. Both groups exhibited synchronized gamma-band oscillations, but controls demonstrated greater inter-subject correlations. Additionally, the difference in inter-subject correlations between high- and low-interaction movies was significantly larger in controls compared to ADHD patients. Between 55 and 75 Hz comparing viewing high interaction movies with low interaction moves, controls had a significantly larger weighting in the right parietal lobe, while ADHD patients had a significantly smaller weighting in the left occipital lobe. These findings reveal distinct spatiotemporal neural signatures in social interaction processing among children with ADHD and controls using naturalistic stimuli. These neural markers offer potential for group differentiation and assessing intervention efficacy, advancing our understanding ADHD-related social interaction mechanisms.

Background: The operation of a transcranial magnetic stimulation (TMS) coil produces high-intensity impulse sounds. In TMS, a magnetic field is generated by a shortduration pulse in the range of thousands of amperes in the TMS coil. When placed in a strong magnetic field, such as inside a magnetic resonance imaging (MRI) bore, the interaction of the magnetic field and the current in the TMS coil can cause strong forces on the coil casing. The strengths of these forces depend on the coil orientation in the main magnetic field (B0). Part of the energy in this process is dissipated in the form of acoustic noise. Objective: Our objective was to measure the sound pressure levels (SPL) of TMS "click" sounds created by commercial TMS stimulators and coils in a typical environment and inside a 3-T MRI scanner and advance the knowledge of the acoustic behaviour of TMS to safely conduct TMS alone as well as concurrently with functional MRI (fMRI). Methods: We report SPL measurements of two commercial MRI-compatible TMS systems in the 3-T B0 field of an MRI scanner and in the earth's magnetic field. Also, we present the acoustic noise measurements of four commercial TMS stimulators and three different TMS coils in a typical operational environment without the B0 field. Results: The maximum peak SPL measured was 158 dB(C) inside the 3-T MRI scanner. Outside the scanner, the maximum peak SPL was 117 dB(C). Inside the scanner, the peak SPL increased by 21-45 dB(C) depending on the stimulator and the orientation of the electric field relative to the B field. Conclusions: Hearing protection is obligatory during concurrent TMS-fMRI experiments and highly recommended during any TMS experiment. The manufacturing of quieter TMS systems is encouraged to reduce the risk of hearing damage and other unwanted effects.

Objectives: Stereoelectroencephalography (SEEG) can define the epileptogenic zone (EZ). However, SEEG is susceptible to the sampling bias, where no SEEG recording is taken within a circumscribed EZ. Methods: Nine patients with medically refractory epilepsy underwent SEEG recording, and brain resection got positive outcomes. Ictal neuronal currents were estimated by distributed source modeling using the SEEG data and individual's anatomical magnetic resonance imaging. Using a retrospective leave -oneout data sub -sampling, we evaluated the sensitivity and specificity of the current estimates using MRI after surgical resection or radio -frequency ablation. Results: The sensitivity and specificity in detecting the EZ were indistinguishable from either the data from all electrodes or the sub -sampled data (rank sum test: rank sum = 23719, p = 0.13) when at least one remaining electrode contact was no more than 20 mm away. Conclusions: The distributed neuronal current estimates of ictal SEEG data can mitigate the challenge of delineating the boundary of the EZ in cases of missing an electrode implanted within the EZ and a required second SEEG exploration. Significance: Distributed source modeling can be a tool for clinicians to infer the EZ by allowing for more flexible planning of the electrode implantation route and minimizing the number of electrodes. (c) 2024 International Federation of Clinical Neurophysiology. Published by Elsevier B.V. This is an open access article under the CC BY -NC -ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

Neuronal activation sequence information is essential for understanding brain functions. Extracting such timing information from blood-oxygenation-level-dependent functional magnetic resonance imaging (fMRI) signals is confounded by local cerebral vascular reactivity (CVR), which varies across brain locations. Thus, detecting neuronal synchrony as well as inferring inter-regional causal modulation using fMRI signals can be biased. Here we used fast fMRI measurements sampled at 10 Hz to measure the fMRI latency difference between visual and sensorimotor areas when participants engaged in a visuomotor task. The regional fMRI timing was calibrated by subtracting the CVR latency measured by a breath-holding task. After CVR calibration, the fMRI signal at the lateral geniculate nucleus (LGN) preceded that at the visual cortex by 496 ms, followed by the fMRI signal at the sensorimotor cortex with a latency of 464 ms. Sequential LGN, visual, and sensorimotor cortex activations were found in each participant after the CVR calibration. These inter-regional fMRI timing differences across and within participants were more closely related to the reaction time after the CVR calibration. Our results suggested the feasibility of mapping brain activity using fMRI with accuracy in hundreds of milliseconds.

We present a design of an inductively coupled radio frequency (ICRF) marker for magnetic resonance (MR)-based positional tracking, enabling the robust increase of tracking signal at all scanning orientations in quadrature-excited closed MR imaging (MRI). The marker employs three curved resonant circuits fully covering a cylindrical surface that encloses the signal source. Each resonant circuit is a planar spiral inductor with parallel plate capacitors fabricated monolithically on flexible printed circuit board (FPC) and bent to achieve the curved structure. Size of the constructed marker is Ø3-mm ×5 -mm with quality factor > 22, and its tracking performance was validated with 1.5 T MRI scanner. As result, the marker remains as a high positive contrast spot under 360° rotations in 3 axes. The marker can be accurately localized with a maximum error of 0.56 mm under a displacement of 56 mm from the isocenter, along with an inherent standard deviation of 0.1-mm. Accrediting to the high image contrast, the presented marker enables automatic and real-time tracking in 3D without dependency on its orientation with respect to the MRI scanner receive coil. In combination with its small form-factor, the presented marker would facilitate robust and wireless MR-based tracking for intervention and clinical diagnosis. This method targets applications that can involve rotational changes in all axes (X-Y-Z).

Neuroimaging studies suggest cross-sensory visual influences in human auditory cortices (ACs). Whether these influences reflect active visual processing in human ACs, which drives neuronal firing and concurrent broadband high-frequency activity (BHFA; >70 Hz), or whether they merely modulate sound processing is still debatable. Here, we presented auditory, visual, and audiovisual stimuli to 16 participants (7 women, 9 men) with stereo-EEG depth electrodes implanted near ACs for presurgical monitoring. Anatomically normalized group analyses were facilitated by inverse modeling of intracranial source currents. Analyses of intracranial event-related potentials (iERPs) suggested cross-sensory responses to visual stimuli in ACs, which lagged the earliest auditory responses by several tens of milliseconds. Visual stimuli also modulated the phase of intrinsic low-frequency oscillations and triggered 15–30 Hz event-related desynchronization in ACs. However, BHFA, a putative correlate of neuronal firing, was not significantly increased in ACs after visual stimuli, not even when they coincided with auditory stimuli. Intracranial recordings demonstrate cross-sensory modulations, but no indication of active visual processing in human ACs.

Here, we report onset latencies for multisensory processing of letters in the primary auditory and visual sensory cortices. Healthy adults were presented with 300-ms visual and/or auditory letters (uppercase Roman alphabet and the corresponding auditory letter names in English). Magnetoencephalography (MEG) evoked response generators were extracted from the auditory and visual sensory cortices for both within-modality and cross-sensory activations; these locations were mainly consistent with functional magnetic resonance imaging (fMRI) results in the same subjects. In the primary auditory cortices (Heschl’s gyri) activity to auditory stimuli commenced at 25 ms and to visual stimuli at 65 ms (median values). In the primary visual cortex (Calcarine fissure) the activations started at 48 ms to visual and at 62 ms to auditory stimuli. This timing pattern suggests that the origins of the cross-sensory activations may be in the primary sensory cortices of the opposite modality, with conduction delays (from one sensory cortex to another) of 17–37 ms. Audiovisual interactions for letters started at 125 ms in the auditory and at 133 ms in the visual cortex (60–71 ms after inputs from both modalities converged). Multivariate pattern analysis suggested similar latency differences between the sensory cortices. Combined with our earlier findings for simpler stimuli (noise bursts and checkerboards), these results suggest that primary sensory cortices participate in early cross-modal and interaction processes similarly for different stimulus materials, but previously learned audiovisual associations and stimulus complexity may delay the start of the audiovisual interaction stage.

With the rapid development of resting-state fMRI (rs-fMRI), there has been a latent but growing focus on the benefits of novel MRI acquisition techniques. Of particular note is the family of highly accelerated fMRI data acquisition methods, which hold great promise for enhancing the capability of resting-state fMRI (rs-fMRI), providing faster sampling of whole-brain BOLD signals for increased functional sensitivity or improved physiological noise reduction. In this chapter, we first introduce signal and noise characteristics in fMRI and outline the benefits of faster sampling for rs-fMRI. Then, we will survey several methods for accelerated fMRI, including echo-planar imaging (EPI), echo-volumar imaging (EVI), simultaneous multislice (SMS)-EPI, inverse imaging (InI), and MR-encephalography (MR-EG). Finally, the chapter ends with some recommendations for fast fMRI acquisition protocols for rs-fMRI research.