Coordinate based meta-analysis of networks in neuroimaging studies Publication date: 15 January 2020 Source: NeuroImage, Volume 205 Author(s): C.R. Tench, Radu Tanasescu, C.S. Constantinescu, W.J. Cottam, D.P. Auer Abstract Meta-analysis of summary results from published neuroimaging studies independently testing a common hypothesis is performed using coordinate based meta-analysis (CBMA), which tests for consistent activation (in the case of functional MRI studies) of the same anatomical regions. Using just the reported coordinates it is also possible to meta-analyse coactivated regions to reveal a network-like structure of coordinate clusters (network nodes) distributed at the coactivated locations and a measure of the coactivation strength (network edges), which is determined by the presence/absence of reported activation. Here a new coordinate-based method to estimate a network of coactivations is detailed, which utilises the Z score accompanying each reported. Coordinate based meta-analysis of networks (CBMAN) assumes that if the activation pattern reported by independent studies is truly consistent, then the relative magnitude of these Z scores might also be consistent. It is hypothesised that this is detectable as Z score covariance between coactivated regions provided the within study variances are small. Advantages of using the Z scores instead of coordinates to measure coactivation strength are that censoring by the significance thresholds can be considered, and that using a continuous measure rather than a dichotomous one can increase statistical power. CBMAN uses maximum likelihood estimation to fit multivariate normal distributions to the standardised Z scores, and the covariances are considered as edges of a network of coactivated clusters (nodes). Here it is validated by numerical simulation and demonstrated on real data used previously to demonstrate CBMA. Software to perform CBMAN is freely available.

Spatiotemporal dynamics of brightness coding in human visual cortex revealed by the temporal context effect Publication date: 15 January 2020 Source: NeuroImage, Volume 205 Author(s): Hao Zhou, Matthew Davidson, Peter Kok, Li Yan McCurdy, Floris P. de Lange, Hakwan Lau, Kristian Sandberg Abstract Human visual perception is modulated by both temporal and spatial contexts. One type of modulation is apparent in the temporal context effect (TCE): In the presence of a constant luminance patch (a long flash), the perceived brightness of a short flash increases monotonically with onset asynchrony. The aim of the current study was to delineate the neural correlates of this illusory effect, particularly focusing on its dynamic neural representation among visual cortical areas. We reconstructed sources of magnetoencephalographic (MEG) data recorded from observers (6 male and 9 female human adults) experiencing the TCE. Together with retinotopic mapping, signals from different occipital lobe areas were extracted to investigate whether different visual areas have differential representation of the onset vs. offset synchronized short flashes. From the data, TCE related responses were observed in LO and V4 in the time window of 200–250 m s, while neuronal responses to physical luminances were observed in the early time window at around 100 m s across early visual cortex, such as V1 and V2, also in V4 and VO. Based on these findings, we suggest that two distinct processes might be involved in brightness coding: one bottom-up process which is stimulus energy driven and responds fast, and another process which may be broadly characterized as top-down or lateral, is context driven, and responds slower. For both processes, we found that V4 might play a critical role in dynamically integrating luminances into brightness perception, a finding that is consistent with the view of V4 as a bottom-up and top-down integration complex.

Anterior fissure, central canal, posterior septum and more: New insights into the cervical spinal cord gray and white matter regional organization using T1 mapping at 7T Publication date: 15 January 2020 Source: NeuroImage, Volume 205 Author(s): Aurélien Massire, Henitsoa Rasoanandrianina, Maxime Guye, Virginie Callot Abstract T1 mapping lacks specificity toward a single particular biological feature, however it has the potential to discriminate spinal cord regional tissue organization and characterize tissue microstructural impairments occurring in neurodegenerative pathologies. In this exploratory work, T1 mapping of the cervical spinal cord with a 300-μm in-plane resolution was performed on fourteen healthy subjects at 7T, using the MP2RAGE sequence. Individual images from C1 to C7 vertebral levels provided a clear delineation of spinal cord anatomical details and substructures including motor columns within gray matter (GM) horns, anterior median fissure, central canal, ventral, lateral and dorsal white matter (WM) fasciculi, and posterior median septum. Group studies highlighted regional T1 differences between regions of interest so far hardly visible at lower spatial resolution. Two-dimensional averaged T1 maps and manual parcellation of GM and WM substructures were built based on these data. Benefiting from the very high spatial resolution achievable at ultra-high field for T1 mapping, this work contributes to improve the in vivo characterization of the cervical spinal cord. By allowing investigation within a wider range of functional regions, it also opens new perspectives for pathology diagnosis such as motor neuron disease, neuropathic pain or refined investigation of neurodegeneration. Graphical abstract

MRI monitoring of temperature and displacement for transcranial focus ultrasound applications Publication date: 1 January 2020 Source: NeuroImage, Volume 204 Author(s): Valéry Ozenne, Charlotte Constans, Pierre Bour, Mathieu D. Santin, Romain Valabrègue, Harry Ahnine, Pierre Pouget, Stephane Lehéricy, Jean-François Aubry, Bruno Quesson Abstract Background Transcranial focus ultrasound applications applied under MRI-guidance benefit from unrivaled monitoring capabilities, allowing the recording of real-time anatomical information and biomarkers like the temperature rise and/or displacement induced by the acoustic radiation force. Having both of these measurements could allow for better targeting of brain structures, with improved therapy monitoring and safety. Method We investigated the use of a novel MRI-pulse sequence described previously in Bour et al., (2017) to quantify both the displacement and temperature changes under various ultrasound sonication conditions and in different regions of the brain. The method was evaluated in vivo in a non-human primate under anesthesia using a single-element transducer (f = 850 kHz) in a setting that could mimic clinical applications. Acquisition was performed at 3 T on a clinical imaging system using a modified single-shot gradient echo EPI sequence integrating a bipolar motion-sensitive encoding gradient. Four slices were acquired sequentially perpendicularly or axially to the direction of the ultrasound beam with a 1-Hz update frequency and an isotropic spatial resolution of 2-mm. A total of twenty-four acquisitions were performed in three different sets of experiments. Measurement uncertainty of the sequence was investigated under different acoustic power deposition and in different regions of the brain. Acoustic simulation and thermal modeling were performed and compared to experimental data. Results The sequence simultaneously provides relevant information about the focal spot location and visualization of heating of brain structures: 1) The sequence localized the acoustic focus both along as well as perpendicular to the ultrasound direction. Tissue displacements ranged from 1 to 2 μm. 2) Thermal rise was only observed at the vicinity of the skull. Temperature increase ranged between 1 and 2 °C and was observed delayed relative the sonication due to thermal diffusion. 3) The fast frame rate imaging was able to highlight magnetic susceptibility artifacts related to breathing, for the most caudal slices. We demonstrated that respiratory triggering successfully restored the sensitivity of the method (from 0.7 μm to 0.2 μm). 4) These results were corroborated by acoustic simulations. Conclusions The current rapid, multi-slice acquisition and real-time implementation of temperature and displacement visualization may be useful in clinical practices. It may help defining operational safety margins, improving therapy precision and efficacy. Simulations were in good agreement with experimental data and may thus be used prior treatment for procedure planning.

Inter-subject pattern analysis: A straightforward and powerful scheme for group-level MVPA Publication date: 1 January 2020 Source: NeuroImage, Volume 204 Author(s): Qi Wang, Bastien Cagna, Thierry Chaminade, Sylvain Takerkart Abstract Multivariate pattern analysis (MVPA) has become vastly popular for analyzing functional neuroimaging data. At the group level, two main strategies are used in the literature. The standard one is hierarchical, combining the outcomes of within-subject decoding results in a second-level analysis. The alternative one, inter-subject pattern analysis, directly works at the group-level by using, e.g. a leave-one-subject-out cross-validation. This study provides a thorough comparison of these two group-level decoding schemes, using both a large number of artificial datasets where the size of the multivariate effect and the amount of inter-individual variability are parametrically controlled, as well as two real fMRI datasets comprising 15 and 39 subjects, respectively. We show that these two strategies uncover distinct significant regions with partial overlap, and that inter-subject pattern analysis is able to detect smaller effects and to facilitate the interpretation. The core source code and data are openly available, allowing to fully reproduce most of these results.

Distinguishing pain from nociception, salience, and arousal: How autonomic nervous system activity can improve neuroimaging tests of specificity Publication date: 1 January 2020 Source: NeuroImage, Volume 204 Author(s): In-Seon Lee, Elizabeth A. Necka, Lauren Y. Atlas Abstract Pain is a subjective, multidimensional experience that is distinct from nociception. A large body of work has focused on whether pain processing is supported by specific, dedicated brain circuits. Despite advances in human neuroscience and neuroimaging analysis, dissociating acute pain from other sensations has been challenging since both pain and non-pain stimuli evoke salience and arousal responses throughout the body and in overlapping brain circuits. In this review, we discuss these challenges and propose that brain-body interactions in pain can be leveraged in order to improve tests for pain specificity. We review brain and bodily responses to pain and nociception and extant efforts toward identifying pain-specific brain networks. We propose that autonomic nervous system activity should be used as a surrogate measure of salience and arousal to improve these efforts and enable researchers to parse out pain-specific responses in the brain, and demonstrate the feasibility of this approach using example fMRI data from a thermal pain paradigm. This new approach will improve the accuracy and specificity of functional neuroimaging analyses and help to overcome current difficulties in assessing pain specific responses in the human brain.

Dopamine D1, but not D2, signaling protects mental representations from distracting bottom-up influences Publication date: 1 January 2020 Source: NeuroImage, Volume 204 Author(s): Wiebke Bensmann, Nicolas Zink, Larissa Arning, Christian Beste, Ann-Kathrin Stock Abstract Goal-directed behavior is affected by subliminally and consciously induced conflicts. Both seem to be modulated by catecholamines, especially dopamine. On the basis of cognitive theoretical and neurobiological considerations, we investigated the effects of dopamine D1 and D2 signaling with the help of unweighted polygenic scores in n = 207 healthy young human subjects. We used a task that combines subliminal primes with conscious flankers to induce conflicts. Dopamine D1 scores were formed based on DRD1 rs4532, CALY rs2298122 and TH rs10770141 single nucleotide polymorphisms (SNPs), while dopamine D2 scores were formed based on DRD2 rs6277 and NPY2R rs2234759 SNPs. We used EEG recordings and source localization analyses to identify differentially modulated neurophysiological sub-processes and functional neuroanatomical structures. Increased dopamine D1 signaling was associated with decreases in consciously induced conflicts. This decrease was due to enhanced stimulus-response mapping in the premotor cortex (BA6), as reflected by an increased P3 amplitude in incongruent trials. Attentional processes remained unaffected by dopamine D1 signaling. The effect of dopamine D2 signaling on conscious conflicts did not reach significance. Subliminally induced conflicts were neither modulated by dopamine D1, nor by dopamine D2 signaling. Our findings suggest that dopamine D1 signaling benefits consciously induced conflicts, presumably by improving the suppression of distracting information via gain control-initiated increases in top-down control processes associated with pre-motor regions. Dopamine D2 signaling does not seem to mediate behavioral differences. Probably, this is because the D2 state facilitates switching between (conflicting) top-down-selected mental representations, but not necessarily between top-down processes and bottom-up distractor information.

Monitoring diffuse injury during disease progression in experimental autoimmune encephalomyelitis with on resonance variable delay multiple pulse (onVDMP) CEST MRI Publication date: 1 January 2020 Source: NeuroImage, Volume 204 Author(s): Aline M. Thomas, Jiadi Xu, Peter A. Calabresi, Peter C.M. van Zijl, Jeff W.M. Bulte Abstract Multiple sclerosis (MS) is an autoimmune disorder that targets myelin proteins and results in extensive damage in the central nervous system in the form of focal lesions as well as diffuse molecular changes. Lesions are currently detected using T1-weighted, T2-weighted, and gadolinium-enhanced magnetic resonance imaging (MRI); however, monitoring such lesions has been shown to be a poor predictor of disease progression. Chemical exchange saturation transfer (CEST) MRI is sensitive to many of the biomolecules in the central nervous system altered in MS that cannot be detected using conventional MRI. We monitored disease progression in an experimental autoimmune encephalomyelitis (EAE) model of MS using on resonance variable delay multiple pulse (onVDMP) CEST MRI. Alterations in onVDMP signal were observed in regions responsible for hindlimb function throughout the central nervous system. Histological analysis revealed glial activation in areas highlighted in onVDMP CEST MRI. onVDMP signal changes in the 3rd ventricle preceded paralysis onset that could not be observed with conventional MRI techniques. Hence, the onVDMP CEST MRI signal has potential as a novel imaging biomarker and predictor of disease progression in MS.

Causal topography of visual cortex in perceptual learning Publication date: 1 January 2020 Source: NeuroImage, Volume 204 Author(s): Paolo Capotosto, Giorgia Committeri, Antonello Baldassarre Abstract Individuals are able to improve their visual skill with practice, a phenomenon called Visual Perceptual Learning (VPL). We previously observed that after training on a difficult shape identification task, the dorsal visual regions (i.e. right V2d/V3 and right lateral occipital, LO) corresponding to the trained visual quadrant, and their homologous in the opposite hemisphere, exhibited a selective activation at the end of the learning. By contrast, such modulation was not observed in the ventral visual regions, corresponding to the untrained quadrants. The causal role of the trained visual cortex was previously showed in a TMS study as its inactivation impaired behavioral performance to learned stimuli. Here, using the same experimental design, we employed TMS over the homologous of the trained area (i.e. left V2d/V3) as well as over the untrained region (i.e. right V4) to causally map the visual network during the perceptual learning. We report a decrease of accuracy after TMS over left V2d/V3 as compared to both right V4 and Sham (inactive stimulation) conditions. Importantly, TMS effect was correlated with the degree of learning, such that subjects with lower accuracy at the end of the training exhibited stronger TMS impairment. These results provide evidence that segregated regions within the visual network are causally involved in visual perceptual learning.

Simultaneous EEG and MEG recordings reveal vocal pitch elicited cortical gamma oscillations in young and older adults Publication date: 1 January 2020 Source: NeuroImage, Volume 204 Author(s): Bernhard Ross, Kelly L. Tremblay, Claude Alain Abstract The frequency-following response with origin in the auditory brainstem represents the pitch contour of voice and can be recorded with electrodes from the scalp. MEG studies also revealed a cortical contribution to the high gamma oscillations at the fundamental frequency (f0) of a vowel stimulus. Therefore, studying the cortical component of the frequency-following response could provide insights into how pitch information is encoded at the cortical level. Comparing how aging affects the different responses may help to uncover the neural mechanisms underlying speech understanding deficits in older age. We simultaneously recorded EEG and MEG responses to the syllable /ba/. MEG beamformer analysis localized sources in bilateral auditory cortices and the midbrain. Time-frequency analysis showed a faithful representation of the pitch contour between 106 Hz and 138 Hz in the cortical activity. A cross-correlation revealed a latency of 20 ms. Furthermore, stimulus onsets elicited cortical 40-Hz responses. Both the 40-Hz and the f0 response amplitudes increased in older age and were larger in the right hemisphere. The effects of aging and laterality of the f0 response were evident in the MEG only, suggesting that both effects were characteristics of the cortical response. After comparing f0 and N1 responses in EEG and MEG, we estimated that approximately one-third of the scalp-recorded f0 response could be cortical in origin. We attributed the significance of the cortical f0 response to the precise timing of cortical neurons that serve as a time-sensitive code for pitch. Graphical abstract