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• We developed a novel dual-site TMS setup to stimulate two adjacent brain regions. • It is subject to fewer technical and spatial limitations than previous attempts. • This enables more accurate and repeatable targeting of brain regions. Using dual-site transcranial magnetic stimulation (dsTMS), the effective connectivity between the primary motor cortex (M1) and adjacent brain areas such as the dorsal premotor cortex (PMd) can be investigated. However, stimulating two brain regions in close proximity (e.g., ±2.3 cm for intrahemispheric PMd–M1) is subject to considerable spatial restrictions that potentially can be overcome by combining two standard figure-of-eight coils in a novel dsTMS setup. After a technical evaluation of its induced electric fields, the dsTMS setup was tested in vivo (n = 23) by applying a short-interval intracortical inhibition (SICI) protocol. Additionally, the intrahemispheric PMd–M1 interaction was probed. E-field modelling was performed using SimNIBS. The technical evaluation yielded no major alterations of the induced electric fields due to coil overlap. In vivo , the setup reliably elicited SICI. Investigating intrahemispheric PMd–M1 interactions was feasible (inter-stimulus interval 6 ms), resulting in modulation of M1 output. The presented dsTMS setup provides a novel way to stimulate two adjacent brain regions with fewer technical and spatial limitations than previous attempts. This dsTMS setup enables more accurate and repeatable targeting of brain regions in close proximity and can facilitate innovation in the field of effective connectivity. [ABSTRACT FROM AUTHOR]

This study explores brain-network differences between the intrinsic and extrinsic motor coordinate frames. A connectivity model showing the coordinate frames difference was obtained using brain fMRI data of right wrist isometric flexions and extensions movements, performed in two forearm postures. The connectivity model was calculated by machine-learning-based neural representation and effective functional connectivity using psychophysiological interaction and dynamic causal modeling analyses. The model indicated the network difference wherein the inferior parietal lobule receives extrinsic information from the rostral lingual gyrus through the superior parietal lobule and transmits intrinsic information to the Handknob, whereas extrinsic information is transmitted to the Handknob directly from the rostral lingual gyrus. A behavioral experiment provided further evidence on the difference between motor coordinate frames showing onset timing delay of muscle activity of intrinsic coordinate-directed wrist movement compared to extrinsic one. These results suggest that, if the movement is externally directed, intrinsic coordinate system information is bypassed to reach the primary motor area. [ABSTRACT FROM AUTHOR]

This study explores brain-network differences between the intrinsic and extrinsic motor coordinate frames. A connectivity model showing the coordinate frames difference was obtained using brain fMRI data of right wrist isometric flexions and extensions movements, performed in two forearm postures. The connectivity model was calculated by machine-learning-based neural representation and effective functional connectivity using psychophysiological interaction and dynamic causal modeling analyses. The model indicated the network difference wherein the inferior parietal lobule receives extrinsic information from the rostral lingual gyrus through the superior parietal lobule and transmits intrinsic information to the Handknob, whereas extrinsic information is transmitted to the Handknob directly from the rostral lingual gyrus. A behavioral experiment provided further evidence on the difference between motor coordinate frames showing onset timing delay of muscle activity of intrinsic coordinate-directed wrist movement compared to extrinsic one. These results suggest that, if the movement is externally directed, intrinsic coordinate system information is bypassed to reach the primary motor area.

Abstract Background Resting-state functional magnetic resonance imaging (Rs-fMRI) has confirmed sensorimotor network (SMN) dysfunction in migraine without aura (MwoA). However, the underlying mechanisms of SMN effective functional connectivity in MwoA remain unclear. We aimed to explore the association between clinical characteristics and effective functional connectivity in SMN, in interictal patients who have MwoA. Methods We used Rs-fMRI to acquire imaging data in 40 episodic patients with MwoA in the interictal phase and 34 healthy controls (HCs). Independent component analysis was used to profile the distribution of SMN and calculate the different SMN activity between the two groups. Subsequently, Granger causality analysis was used to analyze the effective functional connectivity between the SMN and other brain regions. Results Compared to the HCs, MwoA patients showed higher activity in the bilateral postcentral gyri (PoCG), but lower activity in the left midcingulate cortex (MCC). Moreover, MwoA patients showed decreased effective functional connectivity from the SMN to left middle temporal gyrus, right putamen, left insula and bilateral precuneus, but increased effective functional connectivity to the right paracentral lobule. There was also significant effective functional connectivity from the primary visual cortex, right cuneus and right putamen to the SMN. In the interictal period, there was positive correlation between the activity of the right PoCG and the frequency of headache. The disease duration was positively correlated with abnormal effective functional connectivity from the left PoCG to right precuneus. In addition, the headache impact scores were negatively correlated with abnormal effective functional connectivity from the left MCC to right paracentral lobule, as well as from the right precuneus to left PoCG. Conclusions These differential, resting-state functional activities of the SMN in episodic MwoA may contribute to the understanding of migraine-related intra- and internetwork imbalances associated with nociceptive regulation and chronification.

Multiple areas in the cerebellum have been reported to be engaged in reading. However, how these regions cooperate with the reading-related areas in the cerebrum remains unclear. Here, brain images of fifty-two adults were acquired via functional magnetic resonance imaging. By comparing the cerebellar activation across three localization tasks targeting orthographic, phonological, and semantic processing, we first identified three different reading-related areas in the cerebellum, biased toward orthography, phonology, and semantics, respectively. Then, functional connectivity (FC) analyses demonstrated that the mean FC between functionally corresponding areas across the cerebrum and cerebellum was greater than that between noncorresponding areas during silent word reading. FC patterns of functionally corresponding areas could significantly predict reading speed, with the FC driven from orthographic and semantic areas contributing the most. Effective FC analyses further showed that orthographic and semantic areas in the cerebellum had selective and direct connectivity to areas in the cerebrum with similar functional specificity. These results suggest that reading-related areas vary in their functions to reading, and cooperation between areas with corresponding functions was greater than that between noncorresponding areas. These findings emphasize the importance of functional cooperation between the cerebrum and cerebellum during reading from a new perspective., (© The Author(s) 2022. Published by Oxford University Press. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

Highlights: [•] We introduce a version of the Symbol Digit Modalities Test suitable for fMRI studies. [•] Using different inter-stimuli intervals, information processing speed can be assessed. [•] This SDMT version avoids motor responses. [•] SDMT is suitable for fMRI studies involving neurological or pediatric samples. [ABSTRACT FROM AUTHOR]

Abstract: We investigate the effective connectivity in the lateral geniculate nucleus and visual cortex of humans with amblyopia. Six amblyopes participated in this study. Standard retinotopic mapping stimuli were used to define the boundaries of early visual cortical areas. We obtained fMRI time series from thalamic, striate and extrastriate cortical regions for the connectivity study. Thalamo-striate and striate-extrastriate networks were constructed based on known anatomical connections and the effective connectivities of these networks were assessed by means of a nonlinear system identification method. The effective connectivity of all networks studied was reduced when driven by the amblyopic eye, suggesting contrary to the current single-cell model of localized signal reduction, that a significant part of the amblyopic deficit is due to anomalous interactions between cells in disparate brain regions. The effective connectivity loss was unrelated to the fMRI loss but correlated with the degree of amblyopia (ipsilateral LGN to V1 connection), suggesting that it may be a more relevant measure. Feedforward and feedback connectivities were similarly affected. A hemispheric dependence was found for the thalamo-striate feedforward input that was not present for the feedback connection, suggesting that the reduced function of the LGN recently found in amblyopic humans may not be solely determined by the feedback influence from the cortex. Both ventral and dorsal connectivities were reduced. [ABSTRACT FROM AUTHOR]