Brain Topography最新文献

The purpose of this study was to investigate the effects of dual-task standing on postural-related muscle activity and cortical activation in both young and older groups. Fourteen older adults and thirteen young adults were recruited. Participants performed single-task and dual-task standing. The surface electromyographic signals of tibialis anterior, solus, rectus femoris, and biceps femoris at left and right sides were recorded. Simultaneously, cortical activation in the dorsolateral prefrontal and motor cortices were measured. Two-way MANOVAs with repeated measures and Pearson correlation analyses were employed for the statistical analysis. Our results indicated that only the older group presented greater right (p = .002) and left (p = .003) ankle muscle co-activation index, and greater cortical activation in the dorsolateral prefrontal cortex (p < .001), premotor motor cortex (p = .011), supplementary motor area (p = .043), and primary motor cortex (p = .028) in the left hemisphere during dual-task compared to single-task standing. Additionally, the older group showed negative correlations, whereas the young group showed positive correlations between cortical activation and average linear envelope of muscle activity during the single-task standing. Furthermore, the older group showed more significant positive correlations between cortical activation and average linear envelope of muscle activity than the young group during dual-task standing. These observations suggest that age-related overactivation of the prefrontal-motor cortex may lead to redundant ankle joint muscle response during dual-task standing.

Different levels of reduced consciousness characterise human sleep stages at the behavioural level. On electroencephalography (EEG), the identification of sleep stages predominantly relies on localised oscillatory power within distinct frequency bands. Several theoretical frameworks converge on the central significance of long-range information sharing in maintaining consciousness, which experimentally manifests as high functional connectivity (FC) between distant brain regions. Here, we test the hypothesis that EEG-FC reflects sleep stages and hence changes in consciousness. We retrospectively investigated sleep EEG recordings in 14 participants undergoing all stages of non-rapid eye movement (NREM) sleep. We quantified FC with six phase coupling metrics and used the FC coefficients between electrode pairs as features for a gradient boosting classifier trained to distinguish between sleep stages. To characterise FC during each stage of NREM sleep, we compared these metrics regarding their classification accuracy and analysed the ranked feature importance across all electrode pairs. We observed frequency-specific differences in FC between sleep stages for all metrics except the imaginary part of coherence. Alpha coupling decreased from wake to sleep stages N1 and N2, whereas delta coupling increased in deep sleep (N3). FC-based sleep classifiers yielded 51% (phase locking index) to 73% (phase locking value) classification accuracy. Distributed FC patterns in the alpha band ranked highest in terms of feature importance. In a limited sample of 14 subjects, we demonstrated that FC computed from phase information changes significantly across sleep stages. The finding that EEG phase patterns are indicative of sleep stages supports the hypothesis that long-range and spatially distributed phase coupling within frequency bands, especially within the alpha band, is an electrophysiological correlate of consciousness across sleep stages.

The term Super-Recognizer (SR), which describes individuals with supposedly superior facial recognition abilities, may be something of a misnomer. In the same way that blind individuals would not be considered prosopagnosic, SR diagnoses should emphasise at least face identity processing (FIP) specificity, if not recognition in particular. However, SRs tend to be diagnosed with face-specific behavioral tasks, probing either perception and/or recognition, and leaving the neural basis and mechanisms underlying their abilities largely unexplored. The present study therefore sought to determine whether any common FIP subprocesses, among a sample of stringently and comparably diagnosed SRs, would distinguish them from neurotypical controls. To this end, we conducted three Fast Periodic Visual Stimulation (FPVS) EEG experiments in a group of Berlin Police officers identified as SRs using the only existing formal diagnostic framework for lab-based SR identification (Ramon in Neuropsychologia 158:107809, https://doi.org/10.1016/j.neuropsychologia.2021.107809 , 2021) that aligns with the seminal study of SRs (Russell et al. in Psychon Bull Rev 16(2):252-257, https://doi.org/10.3758/PBR.16.2.252 , 2009). These experiments aimed to isolate FIP from behavioral and general perceptual factors in terms of both the consistency and speed of face identity discrimination and categorization. Broadly, the results of all three experiments provided two key findings. First, whichever factors distinguish SRs from controls, they are not face-specific. Second, SRs are not all cut from the same cloth. Rather, the factors distinguishing SRs from controls seem to be individual-specific, warranting more nuanced and bespoke testing criteria for their deployment in practical applications.

Transcranial direct current stimulation (tDCS) is a form of non-invasive brain stimulation that delivers a constant low electric current through electrodes placed on the scalp. A significant amount of research has explored the clinical potential of tDCS in psychiatric disorders. However, the mechanism of tDCS' behavioural effects remains largely unknown. Cerebral blood flow (CBF) is a surrogate marker of neural activity and has been used as an index of brain dysfunction in various psychiatric disorders. Studies have shown that single-session tDCS can modulate regional CBF in humans, however, these results as yet have not been systematically reviewed. The primary objective of this systematic review and meta-analysis was to evaluate the immediate effects of single-session tDCS on regional CBF. A literature search of English language publications in humans was conducted through Ovid database using Medline, Embase, and PsycINFO (last search in August 2023). The following search terms were used: (transcranial direct current stimulation or tDCS) and (cerebral blood flow or cerebrovascular circulation). Studies that reported sufficient data for calculating the pooled effect size of regional CBF change from baseline to immediately post-tDCS were included. The analysis was separated by anodal, cathodal, and sham stimulation. The search identified 188 English language publications. Four papers were deemed eligible for the analysis, while two of them were based on the same sample. Studies varied in terms of tDCS montage, stimulation protocol, and population studied. The meta-analysis found a decrease in regional CBF following single-session cathodal tDCS stimulation (n = 34) and no effect of single-session anodal (n = 58) or sham tDCS (n = 52). However, increased regional CBF following anodal tDCS was significantly associated with older age, sex (% male), and higher current intensity and density based on the results of exploratory moderator and subgroup analyses. The results of this meta-analysis contribute to the growing body of knowledge investigating the cerebral mechanisms of tDCS. Given the limited number and heterogeneity of available studies, further investigation into the effects of single- and multi-session tDCS on regional CBF in clinical or healthy participant samples is warranted to gain a better mechanistic understanding of tDCS' therapeutic effects.

Perceptual awareness of threshold or multi-stable stimuli varies with the pre-stimulus global state of the brain as indexed by EEG microstates. Similarly, awareness also varies with cyclic fluctuations of visceral signals across the cardiac and the respiratory cycle. It remains to be investigated whether the momentary state of the brain contributes to awareness jointly or independently of the bodily phase. We used an orientation discrimination task to determine to what degree the subjective awareness of a visual threshold stimulus varied with the pre-stimulus microstate, cardiac and respiratory phase and whether the brain and body exerted a joint or independent influence on fluctuations of subjective awareness. We compared the pre-stimulus EEG microstates preceding correct aware and unaware trials for the cardiac and respiratory phase. Our findings indicate that the canonical Microstate D was more prevalent in the unaware compared to the aware condition, and the canonical Microstate A accounted for more variance during inhalation compared to exhalation. The pre-stimulus activation of Microstate D, which is anticorrelated with attentional networks preceded trials in which the stimulus was not perceived. Inhalation was instead associated with Microstate A, suggesting increased arousal during this phase. However, we observed no interaction between the bodily phase and awareness, suggesting that the states of the brain and the body exert independent influence on perceptual awareness at the discrimination threshold.

The international 10-20 system's C3/C4 positions are standard for locating the primary motor hand area (M1-HAND) in tDCS and as TMS motor mapping references. While cost-effective, their accuracy for M1-HAND localization is limited as compared to specialized methods. This study aimed to establish a novel position within the 10-20 system for accurately identifying the anatomical hand knob, thereby providing an accurate indirect reference for the M1-HAND. We analyzed 116 MRI scans to define standardized X and Y coordinates representing the scalp projection of the anatomical hand knob. These coordinates were converted into percentages (X% and Y%) based on the nasion-inion and tragus-to-tragus distances, respectively. Initial testing revealed X% didn't improve accuracy and thus was excluded. However, Y% (13% of the tragus-to-tragus distance) significantly enhanced targeting by shifting the optimal site medially relative to C3/C4 placements. We then evaluated the accuracy of this new position against C1/C2, C3h/C4h, and C3/C4. While X coordinates of the corresponding anatomical area of the hand knob on the scalp and C3/C4 positions were similar, their Y coordinates differed significantly. The new position (hand knob position) demonstrated the closest proximity to the anatomical hand knob area on the scalp among all evaluated positions. Our study establishes an accurate position within the 10-20 system for identifying the corresponding anatomical area on the scalp of the hand knob. The Y% value (13% of tragus-to-tragus distance) notably enhances the specificity of M1-HAND localization (via its anatomical correlate) as compared to traditional 10-20 system positions.

Hemifacial spasm (HFS) is a chronic neurological disorder characterized by involuntary muscle contractions of the face, significantly impacting patients' quality of life. Although the facial nerve nucleus has been implicated in HFS pathogenesis, specific research on its functional connectivity within whole-brain networks remains limited. This study aimed to investigate alterations in whole-brain functional connectivity with the facial nerve nucleus as the region of interest (ROI) in HFS patients, before and after microvascular decompression (MVD), to uncover potential mechanisms underlying the disorder and the impact of surgical intervention. Resting-state functional magnetic resonance imaging (rs-fMRI) was conducted on 30 HFS patients and 30 matched healthy controls. Functional connectivity (FC) was analyzed using the facial nerve nucleus as the seed ROI. Demographic, clinical, and laboratory data were collected, including spasm severity, anxiety and depression scores, and preoperative biomarkers. Statistical analyses assessed differences in FC and its correlation with clinical parameters. HFS patients demonstrated significantly increased FC between the left facial nucleus and the right parahippocampal gyrus, as well as between the right facial nucleus and the right fusiform gyrus, compared to healthy controls. These patterns persisted postoperatively, with additional increased FC observed between the right facial nucleus and bilateral superior temporal gyri. Correlation analyses revealed that left facial nucleus-right parahippocampal gyrus FC was positively associated with spasm severity and fibrinogen levels, while right facial nucleus-right fusiform gyrus FC was negatively correlated with monoamine oxidase (MAO) levels. ReHo of both facial nucleus showed significant differences between preoperative HFS patients and healthy controls, whereas ALFF/fALFF and lateralisation of facial nucleus did not show significant between-group differences. This study highlights the role of altered FC between the facial nucleus and brain regions involved in memory, emotion, and visual processing in HFS pathogenesis. While MVD provides symptomatic relief, its short-term effects on FC appear limited, suggesting that functional connectivity changes are chronic and may serve as biomarkers for disease monitoring. These findings provide novel insights into the neural mechanisms of HFS and emphasize the need for further research on long-term brain network adaptations post-surgery.

The study of speech planning/programming may require analysing Event-Related Potentials (ERPs) during articulation. However, ERPs identified during speech production also contain brain signals associated with auditory feedback. Because these processes are both time-locked to the vocal onset, existing algorithms for signal separation have difficulties distinguishing one from the other. Here, we investigated the use of the multi-channel Wiener filter (MWF) to remove the ERP signal related to auditory processing from the ERP signal related to speech production. In a first step, participants were asked to overtly produce mono- or disyllabic pseudowords. In a second step, they had to listen to the recording of their own productions. We used the ERP signal associated with hearing one's own production (referred to as listening ERPs) to estimate and filter out the auditory part of the production ERP. We investigated three versions of the ERPs during speech articulation: (1) the original production ERPs, (2) the ERPs filtered through the MWF, and (3) subtraction ERPs obtained by subtracting the listening ERPs from the original ERPs. Firstly, we conducted a microstate analysis comparing all three versions of the ERPs. Secondly, we conducted separate microstate analyses comparing mono- versus disyllabic conditions on each of the three versions. The results indicate that the subtraction method alters topography consistency and may remove relevant signal from the ERPs. The filtered ERP produced similar results to the original production ERP and thus, it may be unnecessary to remove auditory feedback or other overlapping signal if time-locked to the production onset.

Structural adaptations of the corpus callosum have been well documented in early-trained instrumental musicians, reflecting experience-dependent plasticity in response to bimanual coordination and auditory-motor integration. Although the sensorimotor demands of singing differ, professional vocal training also requires precise control of bilateral vocal tract musculature and integration of auditory feedback; yet, less is known about whether similar adaptations occur in professional singers. This study used structural neuroimaging to investigate variations in callosal thickness in relation to vocal training in 55 participants, including 27 professionally trained opera singers and 28 non-singers. A significant negative correlation between age at first singing lesson and callosal thickness was observed in singers, with effects surviving correction for multiple comparisons in the anterior third (rostrum, genu, rostral body), at the anterior-posterior midbody border, and the isthmus. While group comparisons revealed greater callosal thickness in singers than non-singers in these same regions, these differences did not remain significant after correction. Likewise, a positive correlation between years of professional singing and callosal thickness in the midbody did not survive correction for multiple comparisons. Our main finding aligns with prior evidence of training-related plasticity in the corpus callosum and suggests that early musical experience-including in the context of intensive vocal practice-may contribute to enhanced interhemispheric connectivity. Although the current design does not allow us to isolate effects specific to singing compared to other forms of sensorimotor training, the results underscore developmental timing as a key factor in how prolonged musical experience may shape brain structure.

Although the interstimulus interval (ISI) is one of the crucial parameters in the transcranial magnetic stimulation (TMS), the ISI effect on the results of the TMS motor mapping is usually overlooked. This study explored the influence of ISI, ranging from 1.5 to 41 s, on multi-muscle navigated TMS (nTMS) motor mapping results. Twenty-six healthy male volunteers underwent four nTMS motor mapping sessions on two separate days. We mapped the muscles' cortical representations (MCRs) of the five upper limb muscles: abductor pollicis brevis (APB), abductor digiti minimi (ADM), first dorsal interosseous (FDI), extensor digitorum communis (EDC), and biceps brachii (BB). We estimated the relationship between ISIs and trial-to-trial motor evoked potentials (MEPs) amplitudes and MCR areas. In addition, we accounted for the association between the ISI and TMS mapping procedure parameters such as the distance between the successive stimulation points, the number of stimuli in a TMS session, and the stimulus counting number. A weak positive association was observed between: (1) trial-to-trial ISI and MEP amplitude and (2) median ISI and MCR areas. We recommend reporting ISI values in TMS motor mapping studies and monitoring the impact of ISI on MEP amplitudes.