Biology subjects

Cattaneo, L.

Publications and source records attributed to Cattaneo, L..

7 recordsLinked to original sources

bioRxiv2026

TIDE: Tractography-Informed Dose Estimation for individualised TMS intensity

Transcranial magnetic stimulation (TMS) is commonly dosed by setting stimulation intensity as a fixed percentage of the resting motor threshold (RMT), although a motor-derived intensity may not produce comparable neural recruitment across non-motor targets. We present TIDE (Tractography-Informed Dose Estimation), an open-source, SimNIBS-based pipeline designed to derive individualised stimulation intensities for non-motor white-matter targets. TIDE combines individual RMT measurements, finite-element electric-field modelling and diffusion MRI tractography to rescale the stimulation intensity according to the geometry and stimulation efficiency of the pathway of interest. Specifically, it computes the activating function along subject-specific streamlines and estimates the stimulator output, expressed as a percentage of maximum stimulator output, required for the target pathway to reach the activation level produced in the corticospinal tract at RMT. In an independent dataset of 19 participants, in which stimulation had been dosed conventionally as a fixed percentage of RMT, the relative difference between delivered and TIDE-estimated intensity was associated with the magnitude of TMS-induced behavioural effects at two frontal aslant tract (FAT) stimulation sites, while the delivered intensity alone was not. TIDE therefore extends conventional E-field dosing from cortical field magnitude to subject-specific pathway geometry, providing a method to move beyond the assumption of homogeneous pathway engagement while accounting for inter-individual variability in pathway-specific stimulation efficiency.

neuroscience↗

bioRxiv2025

MEP-independent silent periods in hand muscles elicited by Transcranial Magnetic Stimulation of the ventral premotor cortex: a non-invasive tool to explore premotor negative motor areas

ObjectiveWe investigate the possibility to disrupt motor activity via premotor and parietal cortex stimulation, by inducing cortical silent periods (cSPs) in the voluntarily activated upper limb. MethodsWe analyzed data from 17 subjects with normal brain function, using navigated TMS (nTMS) on individual MR anatomies. We applied single-pulse biphasic stimulation at 120% of resting motor threshold (rMT) in blocks of 30 stimulations on each spot of a 10-16 point grid covering the inferior parietal and frontal lobes in the dominant hemisphere while participants performed voluntary submaximal contraction. Electromyography (EMG) was recorded bilaterally from intrinsic hand muscles. ResultsWe observed cSPs not preceded by a MEP in the contralateral hand in 16/17 participants. The maximum overlap, of individual areas where such MEP-independent cSPs could be evoked, corresponded to the ventral precentral gyrus (MNI coordinates: [x=-57, y=7, z=33]). In a subset of stimulus sites, MEP-independent cSPs were bilateral, with contralateral predominance. Canonical short-latency MEPs were observed in all patients, with maximum overlap over the primary motor cortex. We also observed rare contralateral long-latency (> 23 ms) MEP-like responses from peri-Rolandic TMS. ConclusionsMEP-independent cSPs are systematically elicitable in healthy participants They likely reflect interference with premotor representations of ongoing movements. They offer a novel possibility to investigate higher-order motor functions in the experimental and clinical neurosciences.

neuroscience↗

bioRxiv2024

Stimulation of the Frontal Aslant Tract's origin in the caudal superior frontal gyrus alters ongoing spontaneous rhythmic activity independently from the effector. Evidence from tractography-guided Transcranial Magnetic Stimulation.

the crown of the human Superior Frontal Gyrus (SFG-crown) is a functionally independent region, nestled between the dorsal premotor and supplementary motor cortices, that supports internally-timed action control. The unique SFG-crowns connectivity fingerprint by the Frontal Aslant Tract (FAT), suggests a caudal-rostral pattern of increasing abstractness of action representations. Coherently, since the mid-portion of the caudal SFG contains a representation of action strategies that involve internal timing, we hypothesized that the caudal portion of the SFG may be involved in action execution of internally-timed actions. To test this, we asked 21 healthy participants to perform a self-paced tapping movement with the right index finger or a self-paced articulation of the syllable /da/ while applying online single-pulse TMS to the posterior, middle and anterior origins of the FAT in the left SFG-crown. Results showed that effective TMS (compared to sham) impacted rhythm production in both tasks, only when applied to the posterior SFG region, by reducing the probability of motor events in the 200 ms following TMS. The present data support the hypothesis, that the posterior SFG-crown, associated with the most posterior origin of the FAT fibers, is involved in the production of internally-timed actions, in an effector-independent modality, suggesting a domain-general role in the execution of internally-timed movements.

neuroscience↗

bioRxiv2022

Connectivity by the Frontal Aslant Tract (FAT) explains local functional specialization of the superior and inferior frontal gyri in humans while choosing predictive over reactive strategies: a tractography-guided TMS study

Predictive and reactive behaviors represent two mutually exclusive strategies for successfully completing a sensorimotor task. It is thought that predictive actions are based on the medial premotor system, in the superior frontal gyrus (SFG) and reactive stimulus-response behaviors rely on a lateral premotor system, in the inferior frontal gyrus (IFG). The frontal aslant tract (FAT), a white matter tract connecting SFG and IFG, is a possible neural substrate of the predictive/reactive interactions. We used diffusion-weighted imaging (DWI) of 17 male and female healthy human volunteers, to dissect 3 sub-bundles of fibers belonging to the left FAT (bundles 1, 2 and 3), arising ventrally from 1) the ventral precentral gyrus, 2) midway between the PCG and pars opercularis (POp) and 3) the POp and terminating dorsally in 3 different parts of the SFG, in a caudal-rostral order. We applied online transcranial magnetic stimulation (TMS) to 6 spots, corresponding to the medial and lateral terminations of bundles 1-3 during the fixed-duration set period of a delayed reaction task, that can be solved using a predictive (anticipatory) strategy or with a reactive strategy. Results showed that TMS changed the frequency of predictive/reactive strategies only when applied over 2 spots, the SFG and IFG terminations of bundle 2. Importantly, the effects of TMS were opposite when applied to the SFG or to the IFG. Our data show that the SFG and the IFG have opposite roles in producing predictive or reactive behavior and that reciprocal integration or competition is probably mediated by the FAT. Significance StatementAs is well-known by athletes at starting blocks, interaction with the world can occur with a predictive strategy (anticipating a GO-signal) or a reactive strategy (waiting for the GO-signal to be manifest) and they are mutually exclusive. Here we showed, by using non-invasive brain stimulation (TMS), that two specific cortical regions in the superior frontal gyrus (SFG) and the inferior frontal gyrus (IFG) have opposite roles in facilitating a predictive or a reactive strategy. Importantly these two very distant regions but with highly interconnected functions are specifically connected by a small white matter bundle, which probably mediates the competition between predictive and reactive strategies. More generally, we show that the implementing anatomical connectivity in TMS studies strongly reduces spatial noise.

neuroscience↗

bioRxiv2021

Decellularized Normal and Tumor Scaffolds for Cancer Organoid Cultures as a Model of Colorectal Peritoneal Metastases

Peritoneal metastases (PM) from colorectal cancer (CRC) are associated with poor survival. The extracellular matrix (ECM) plays a fundamental role in modulating the homing of CRC metastases to the peritoneum. The mechanisms underlying the interactions between metastatic cells and the ECM, however, remain poorly understood and the number of in vitro models available for the study of the peritoneal metastatic process is limited. Here, we show that decellularized ECM of the peritoneal cavity allows the growth of organoids obtained from PM, favoring the development of three-dimensional nodules that maintain the characteristics of in vivo PM. Organoids preferentially grow on scaffolds obtained from neoplastic peritoneum, which are characterized by greater stiffness than normal scaffolds. A gene expression analysis of organoids grown on different substrates reflected faithfully the clinical and biological characteristics of the organoids. An impact of the ECM on the response to standard chemotherapy treatment for PM was also observed. SignificanceEvidence of the value of ex vivo 3D models obtained by combining patient-derived extracellular matrices depleted of cellular components and organoids to mimic the metastatic niche, to be used as a tool to develop new therapeutic strategies in a biologically relevant context, to personalize treatments and increase their efficacy.

cancer biology↗

bioRxiv2019

A study of parietal-motor connectivity by intraoperative dual cortical stimulation

the function of the primates posterior parietal cortex in sensorimotor transformations is well-established, though in humans its complexity is still challenging. Well-established models indicate that the posterior parietal cortex influences motor output indirectly, by means of connections to the premotor cortex, which in turn is directly connected to the motor cortex. The possibility that the posterior parietal cortex could be at the origin of direct afferents to M1 has been suggested in humans but has never been confirmed directly. In the present work we assessed during intraoperative monitoring of the corticospinal tract in brain tumour patients the existence of short-latency effects of parietal stimulation on corticospinal excitability to the upper limb. We identified several foci within the inferior parietal lobule that drove short-latency influences on cortical motor output. Active foci were distributed along the postcentral gyrus and clustered around the anterior intraparietal area and around the parietal operculum. For the first time in humans, the present data show direct evidence in favour of a distributed system of connections from the posterior parietal cortex to the ipsilateral primary motor cortex.

neuroscience↗

bioRxiv2018

Action intention modulates the representation of object features in early visual cortex

The role of the visual cortex has been extensively studied to determine its role in object recognition but to a lesser degree to determine how action planning influences the representation of objects features. We used functional MRI and pattern classification methods to determine if during action planning, object features (orientation and location) could be decoded in an action-dependent way. Sixteen human participants used their right dominant hand to perform movements (Align or Open reach) towards one of two 3D-real oriented objects that were simultaneously presented and placed on either side of a fixation cross. While both movements required aiming toward target location, Align but not Open reach movements required participants to precisely adjust hand orientation. Therefore, we hypothesized that if the representation of object features is modulated by the upcoming action, pre-movement activity pattern would allow more accurate dissociation between object features in Align than Open reach tasks. We found such dissociation in the anterior and posterior parietal cortex, as well as in the dorsal premotor cortex, suggesting that visuomotor processing is modulated by the upcoming task. The early visual cortex showed significant decoding accuracy for the dissociation between object features in the Align but not Open reach task. However, there was no significant difference between the decoding accuracy in the two tasks. These results demonstrate that movement-specific preparatory signals modulate object representation in the frontal and parietal cortex, and to a lesser extent in the early visual cortex, likely through feedback functional connections.

neuroscience↗