Sleepless and desynchronized: Impaired inter trial phase coherence of steady-state potentials following sleep deprivation Publication date: 15 November 2019 Source: NeuroImage, Volume 202 Author(s): M. Eidelman-Rothman, E. Ben-Simon, D. Freche, A. Keil, T. Hendler, N. Levit-Binnun Abstract Sleep loss has detrimental effects on cognitive and emotional functioning. These impairments have been associated with alterations in EEG measures of power spectrum and event-related potentials, however the impact of sleep loss on inter trial phase coherence (ITPC), a measure of phase consistency over experimental trials, remains mostly unknown. ITPC is thought to reflect the ability of the neural response to temporally synchronize with relevant events, thus optimizing information processing. In the current study we investigated the effects of sleep deprivation on information processing by evaluating the phase consistency of steady-state visual evoked potentials (ssVEPs) as well as amplitude-based measures of ssVEPs, obtained from a group of 18 healthy individuals following 24 h of total sleep deprivation and after a night of habitual sleep. An ssVEP task was utilized, which included the presentation of dots flickering at 7.5 Hz, along with a cognitive-emotional task. Our results show that ITPC is significantly reduced under sleep deprivation relative to habitual sleep. Interestingly, decreased ITPC under sleep deprivation was associated with decreased behavioral performance in the psychomotor vigilance task (PVT), a validated measure of reduced vigilance following a lack of sleep. The results suggest that the capability of the brain to synchronize with rhythmic stimuli is disrupted without sleep. Thus, decreased ITPC may represent an objective and mechanistic measure of sleep loss, allowing future work to study the relation between brain-world synchrony and the specific functional impairments associated with sleep deprivation.

Long-term training-dependent representation of individual finger movements in the primary motor cortex Publication date: 15 November 2019 Source: NeuroImage, Volume 202 Author(s): Kenji Ogawa, Kaoru Mitsui, Fumihito Imai, Shuhei Nishida Abstract We investigated the effects of long-term training on the neural representation of individual finger movements in the primary sensorimotor cortex. One group of participants (trained group) included subjects trained in playing the piano (mean years of experience = 17.9; range = 9–26; n = 20). The other group of participants (novice group) had no prior experience (n = 20). All participants performed finger-tapping movements using either of the four digits of the hand (index, middle, ring, and little fingers). Functional magnetic resonance imaging (fMRI) was used to analyze the spatial activation patterns elicited by individual finger movements. Subsequently, we tried to classify the finger that was being moved using a multi-voxel pattern analysis (MVPA). Our results showed significantly higher-than-chance classification accuracies in both primary motor cortex (M1) and somatosensory cortex (S1) contralateral to the hand. We also found significantly lower classification accuracies for both hands in the trained group compared with the novice group in M1, without significant differences in the average signal changes and the number of activated voxels for individual fingers or overlap between digits. Representational similarity analysis (RSA) also demonstrated the differences in similarity patterns of activations between the trained and novice groups in M1. Our results indicate the modulation of neural representations of individual finger movements of M1 due to long-term training.

Discourse management during speech perception: A functional magnetic resonance imaging (fMRI) study Publication date: 15 November 2019 Source: NeuroImage, Volume 202 Author(s): Susanne Dietrich, Ingo Hertrich, Verena C. Seibold, Bettina Rolke Abstract Discourse structures enable us to generate expectations based upon linguistic material that has already been introduced. We investigated how the required cognitive operations such as reference processing, identification of critical items, and eventual handling of violations correlate with neuronal activity within the language network of the brain. To this end, we conducted a functional magnetic resonance imaging (fMRI) study in which we manipulated spoken discourse coherence by using presuppositions (PSPs) that either correspond or fail to correspond to items in preceding context sentences. Definite and indefinite determiners were used as PSP triggers, referring to (non-) uniqueness or (non-) existence of an item. Discourse adequacy was tested by means of a behavioral rating during fMRI. Discourse violations yielded bilateral hemodynamic activation within the inferior frontal gyrus (IFG), the inferior parietal lobe including the angular gyrus (IPL/AG), the pre-supplementary motor area (pre-SMA), and the basal ganglia (BG). These findings illuminate cognitive aspects of PSP processing: (1) a reference process requiring working memory (IFG), (2) retrieval and integration of semantic/pragmatic information (IPL/AG), (3) cognitive control of inconsistency management (pre-SMA/BG) in terms of “successful” comprehension despite PSP violations at the surface. These results provide the first fMRI evidence needed to develop a functional neuroanatomical model for context-dependent sentence comprehension based on the example of PSP processing.

Cortical, subcortical and spinal neural correlates of slackline training-induced balance performance improvements Publication date: 15 November 2019 Source: NeuroImage, Volume 202 Author(s): Louis-Solal Giboin, Kristian Loewe, Thomas Hassa, Andreas Kramer, Christian Dettmers, Stefan Spiteri, Markus Gruber, Mircea Ariel Schoenfeld Abstract Humans develop posture and balance control during childhood. Interestingly, adults can also learn to master new complex balance tasks, but the underlying neural mechanisms are not fully understood yet. Here, we combined broad scale brain connectivity fMRI at rest and spinal excitability measurements during movement. Six weeks of slackline training improved the capability to walk on a slackline which was paralleled by functional connectivity changes in brain regions associated with posture and balance control and by task-specific changes of spinal excitability. Importantly, the performance of trainees was not better than control participants in a different, untrained balance task. In conclusion, slackline training induced large-scale neuroplasticity which solely transferred into highly task specific performance improvements.

Bifurcation structure determines different phase-amplitude coupling patterns in the activity of biologically plausible neural networks Publication date: 15 November 2019 Source: NeuroImage, Volume 202 Author(s): Osvaldo Matías Velarde, Eugenio Urdapilleta, Germán Mato, Damián Dellavale Abstract Phase-amplitude cross frequency coupling (PAC) is a rather ubiquitous phenomenon that has been observed in a variety of physical domains; however, the mechanisms underlying the emergence of PAC and its functional significance in the context of neural processes are open issues under debate. In this work we analytically demonstrate that PAC phenomenon naturally emerges in mean-field models of biologically plausible networks, as a signature of specific bifurcation structures. The proposed analysis, based on bifurcation theory, allows the identification of the mechanisms underlying oscillatory dynamics that are essentially different in the context of PAC. Specifically, we found that two PAC classes can coexist in the complex dynamics of the analyzed networks: 1) harmonic PAC which is an epiphenomenon of the nonsinusoidal waveform shape characterized by the linear superposition of harmonically related spectral components, and 2) nonharmonic PAC associated with “true” coupled oscillatory dynamics with independent frequencies elicited by a secondary Hopf bifurcation and mechanisms involving periodic excitation/inhibition (PEI) of a network population. Importantly, these two PAC types have been experimentally observed in a variety of neural architectures confounding traditional parametric and nonparametric PAC metrics, like those based on linear filtering or the waveform shape analysis, due to the fact that these methods operate on a single one-dimensional projection of an intrinsically multidimensional system dynamics. We exploit the proposed tools to study the functional significance of the PAC phenomenon in the context of Parkinson's disease (PD). Our results show that pathological slow oscillations (e.g. β band) and nonharmonic PAC patterns emerge from dissimilar underlying mechanisms (bifurcations) and are associated to the competition of different BG-thalamocortical loops. Thus, this study provides theoretical arguments that demonstrate that nonharmonic PAC is not an epiphenomenon related to the pathological βband oscillations, thus supporting the experimental evidence about the relevance of PAC as a potential biomarker of PD. Graphical abstract

Identifying inter-individual differences in pain threshold using brain connectome: a test-retest reproducible study Publication date: 15 November 2019 Source: NeuroImage, Volume 202 Author(s): Yiheng Tu, Binlong Zhang, Jin Cao, Georgia Wilson, Zhiguo Zhang, Jian Kong Abstract Individuals are unique in terms of brain and behavior. Some are very sensitive to pain, while others have a high tolerance. However, how inter-individual intrinsic differences in the brain are related to pain is unknown. Here, we performed longitudinal test-retest analyses to investigate pain threshold variability among individuals using a resting-state fMRI brain connectome. Twenty-four healthy subjects who received four MRI sessions separated by at least 7 days were included in the data analysis. Subjects’ pain thresholds were measured using two modalities of experimental pain (heat and pressure) on two different locations (heat pain: leg and arm; pressure pain: leg and thumbnail). Behavioral results showed strong inter-individual variability and strong within-individual stability in pain threshold. Resting state fMRI data analyses showed that functional connectivity profiles can accurately identify subjects across four sessions, indicating that an individual’s connectivity profile may be intrinsic and unique. By using multivariate pattern analyses, we found that connectivity profiles could be used to predict an individual’s pain threshold at both within-session and between-session levels, with the most predictive contribution from medial-frontal and frontal-parietal networks. These results demonstrate the potential of using a resting-state fMRI brain connectome to build a ‘neural trait’ for characterizing an individual’s pain-related behavior, and such a ‘neural trait’ may eventually be used to personalize clinical assessments.

Higher striatal D2-receptor availability in aerobically fit older adults but non-selective intervention effects after aerobic versus resistance training Publication date: 15 November 2019 Source: NeuroImage, Volume 202 Author(s): Lars S. Jonasson, Lars Nyberg, Jan Axelsson, Arthur F. Kramer, Katrine Riklund, Carl-Johan Boraxbekk Abstract There is much evidence that dopamine is vital for cognitive functioning in aging. Here we tested the hypothesis that aerobic exercise and fitness influence dopaminergic neurotransmission in the striatum, and in turn performance on offline working-memory updating tasks. Dopaminergic neurotransmission was measured by positron emission tomography (PET) and the non-displacable binding potential (BPND) of [11C]raclopride, i.e. dopamine (DA) D2-receptor (D2R) availability. Fifty-four sedentary older adults underwent a six-months exercise intervention, performing either aerobic exercise or stretching, toning, and resistance active control training. At baseline, higher aerobic fitness levels (VO2peak) were associated with higher BPND in the striatum, providing evidence of a link between an objective measure of aerobic fitness and D2R in older adults. BPND decreased substantially over the intervention in both groups but the intervention effects were non-selective with respect to exercise group. The decrease was several times larger than any previously estimated annual decline in D2R, potentially due to increased endogenous DA. Working-memory was unrelated to D2R both at baseline and following the intervention. To conclude, we provide partial evidence for a link between physical exercise and DA. Utilizing a PET protocol able to disentangle both D2R and DA levels could shed further light on whether, and how, aerobic exercise impacts the dopaminergic system in older adults.

Replication and generalization in applied neuroimaging Publication date: 15 November 2019 Source: NeuroImage, Volume 202 Author(s): Garikoitz Lerma-Usabiaga, Pratik Mukherjee, Zhimei Ren, Michael L. Perry, Brian A. Wandell Abstract There is much interest in translating neuroimaging findings into meaningful clinical diagnostics. The goal of scientific discoveries differs from clinical diagnostics. Scientific discoveries must replicate under a specific set of conditions; to translate to the clinic we must show that findings using purpose-built scientific instruments will be observable in clinical populations and instruments. Here we describe and evaluate data and computational methods designed to translate a scientific observation to a clinical setting. Using diffusion weighted imaging (DWI), Wahl et al. (2010) observed that across subjects the mean fractional anisotropy (FA) of homologous pairs of tracts is highly correlated. We hypothesize that this is a fundamental biological trait that should be present in most healthy participants, and deviations from this assessment may be a useful diagnostic metric. Using this metric as an illustration of our methods, we analyzed six pairs of homologous white matter tracts in nine different DWI datasets with 44 subjects each. Considering the original FA measurement as a baseline, we show that the new metric is between 2 and 4 times more precise when used in a clinical context. Our framework to translate research findings into clinical practice can be applied, in principle, to other neuroimaging results.

Functional connectivity of brain associated with passive range of motion exercise: Proprioceptive input promoting motor activation? Publication date: 15 November 2019 Source: NeuroImage, Volume 202 Author(s): Fatima A. Nasrallah, Abdalla Z. Mohamed, Megan EJ. Campbell, Hong Kai Yap, Chen-Hua Yeow, Jeong Hoon Lim Abstract Soft robotics have come to the forefront of devices available for rehabilitation following stroke; however, objective evaluation of the specific brain changes following rehabilitation with these devices is lacking. In this study, we utilized functional Magnetic Resonance Imaging (fMRI) and dynamic causal modeling (DCM) to characterize the activation of brain areas with a MRI compatible glove actuator compared to the conventional manual therapy. Thirteen healthy volunteers engaged in a motor-visual fMRI task under four different conditions namely active movement, manual passive movement, passive movement using a glove actuator, and crude tactile stimulation. Brain activity following each task clearly identified the somatosensory motor area (SMA) as a major hub orchestrating activity between the primary motor (M1) and sensory (S1) cortex. During the glove-induced passive movement, activity in the motor-somatosensory areas was reduced, but there were significant increases in motor cortical activity compared to manual passive movement. We estimated the modulatory signaling from within a defined sensorimotor network (SMA, M1, and S1), through DCM and highlighted a dual-gating of sensorimotor inputs to the SMA. Proprioceptive signaling from S1 to the SMA reflected positive coupling for the manually assisted condition, while M1 activity was positively coupled to the SMA during the glove condition. Importantly, both the S1 and M1 were shown to influence each other’s connections with the SMA, with inhibitory nonlinear modulation by the M1 on the S1-SMA connection, and similarly S1 gated the M1-SMA connection. The work is one of the first to have applied effective connectivity to examine sensorimotor activity ensued by manual or robotic passive range of motion exercise, crude tactile stimulation, and voluntary movements to provide a basis for the mechanism by which soft actuators can alter brain activity.

Sensorimotor cortex neurometabolite levels as correlate of motor performance in normal aging: evidence from a 1H-MRS study Publication date: 15 November 2019 Source: NeuroImage, Volume 202 Author(s): Oron Levin, Akila Weerasekera, Bradley R. King, Kirstin F. Heise, Diana M. Sima, Sima Chalavi, Celine Maes, Ronald Peeters, Stefan Sunaert, Koen Cuypers, Sabine Van Huffel, Dante Mantini, Uwe Himmelreich, Stephan P. Swinnen Abstract Aging is associated with gradual alterations in the neurochemical characteristics of the brain, which can be assessed in-vivo with proton-magnetic resonance spectroscopy (1H-MRS). However, the impact of these age-related neurochemical changes on functional motor behavior is still poorly understood. Here, we address this knowledge gap and specifically focus on the neurochemical integrity of the left sensorimotor cortex (SM1) and the occipital lobe (OCC), as both regions are main nodes of the visuomotor network underlying bimanual control. 1H-MRS data and performance on a set of bimanual tasks were collected from a lifespan (20–75 years) sample of 86 healthy adults. Results indicated that aging was accompanied by decreased levels of N-acetylaspartate (NAA), glutamate-glutamine (Glx), creatine ​+ ​phosphocreatine (Cr) and myo-inositol (mI) in both regions, and decreased Choline (Cho) in the OCC region. Lower NAA and Glx levels in the SM1 and lower NAA levels in the OCC were related to poorer performance on a visuomotor bimanual coordination task, suggesting that NAA could serve as a potential biomarker for the integrity of the motor system supporting bimanual control. In addition, lower NAA, Glx, and mI levels in the SM1 were found to be correlates of poorer dexterous performance on a bimanual dexterity task. These findings highlight the role for 1H-MRS to study neurochemical correlates of motor performance across the adult lifespan.