Biology subjects

Tagliaferri, M.

Publications and source records attributed to Tagliaferri, M..

3 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↗

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↗