ORCID Profile
0000-0002-1395-9005
Current Organisation
IRCCS Istituto Centro San Giovanni di Dio Fatebenefratelli
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Publisher: Springer Science and Business Media LLC
Date: 10-05-2019
DOI: 10.1007/S10548-019-00715-X
Abstract: Existing literature on sensory deprivation suggests that short-lasting periods of dark adaptation (DA) can cause changes in visual cortex excitability. DA cortical effects have previously been assessed through phosphene perception, i.e., the ability to report visual sensations when a transcranial magnetic stimulation (TMS) pulse is delivered over the visual cortex. However, phosphenes represent an indirect measure of visual cortical excitability which relies on a subjective report. Here, we aimed at overcoming this limitation by assessing visual cortical excitability by combining subjective (i.e., TMS-induced phosphenes) and objective (i.e., TMS-evoked potentials - TEPs) measurements in a TMS-EEG protocol after 30 min of DA. DA effects were compared to a control condition, entailing 30 min of controlled light exposure. TMS was applied at 11 intensities in order to estimate the psychometric function of phosphene report and explore the relationship between TEPs and TMS intensity. Compared to light adaptation, after DA the slope of the psychometric function was significantly steeper, and the litude of a TEP component (P60) was lower, only for high TMS intensities. The perceptual threshold was not affected by DA. These results support the idea that DA leads to a change in the excitability of the visual cortex, accompanied by a behavioral modification of visual perception. Furthermore, this study provides a first valuable description of the relationship between TMS intensity and visual TEPs.
Publisher: Cold Spring Harbor Laboratory
Date: 25-01-2020
DOI: 10.1101/2020.01.24.918102
Abstract: It has been theorized that hemispheric dominance and a more segregated information processing have evolved to overcome long conduction delay through the corpus callosum (TCD) but that this may still impact behavioral performance mostly in tasks requiring high timing accuracy. Nevertheless, a thorough understanding of the temporal features of interhemispheric communication is missing due to methodological shortcomings. Here, we show in the motor system that TCD can be measured from transcranial magnetic stimulation (TMS) -evoked potentials (TEPs): by integrating TEPs with diffusion tensor imaging (DTI) and peripheral measures of interhemispheric inhibition (i.e., the ipsilateral silent period-iSP), we show that P15 TEP component reflects TCD between motor areas. Importantly, we report that better bimanual coordination is achieved when TCD between motor areas is asymmetric. These results suggest that interhemispheric communication can be optimized through asymmetric connectivity, in which information transfer is faster from the dominant hemisphere to the non-dominant hemisphere.
Publisher: Frontiers Media SA
Date: 16-09-2022
DOI: 10.3389/FNHUM.2022.937515
Abstract: In a recently published study combining transcranial magnetic stimulation and electroencephalography (TMS-EEG), an early component of TMS-evoked potentials (TEPs), i.e., M1-P15, was proposed as a measure of transcallosal inhibition between motor cortices. Given that early TEPs are known to be highly variable, further evidence is needed before M1-P15 can be considered a reliable index of effective connectivity. Here, we conceived a new preregistered TMS-EEG study with two aims. The first aim was validating the M1-P15 as a cortical index of transcallosal inhibition by replicating previous findings on its relationship with the ipsilateral silent period (iSP) and with performance in bimanual coordination. The second aim was inducing a task-dependent modulation of transcallosal inhibition. A new s le of 32 healthy right-handed participants underwent behavioral motor tasks and TMS-EEG recording, in which left and right M1 were stimulated both during bimanual tasks and during an iSP paradigm. Hypotheses and methods were preregistered before data collection. Results show a replication of our previous findings on the positive relationship between M1-P15 litude and the iSP normalized area. Differently, the relationship between M1-P15 latency and bimanual coordination was not confirmed. Finally, M1-P15 litude was modulated by the characteristics of the bimanual task the participants were performing, and not by the contralateral hand activity during the iSP paradigm. In sum, the present results corroborate our previous findings in validating the M1-P15 as a cortical marker of transcallosal inhibition and provide novel evidence of its task-dependent modulation. Importantly, we demonstrate the feasibility of preregistration in the TMS-EEG field to increase methodological rigor and transparency.
Publisher: Cold Spring Harbor Laboratory
Date: 13-03-2022
DOI: 10.1101/2022.03.10.483631
Abstract: In a recently published study combining transcranial magnetic stimulation and electroencephalography (TMS-EEG), we provided first evidence of M1-P15, an early component of TMS-evoked potentials, as a measure of transcallosal inhibition between motor cortices. However, considering the technical challenges of TMS-EEG recordings, further evidence is needed before M1-P15 can be considered a reliable index. Here, we aimed at validating M1-P15 as a cortical index of transcallosal inhibition, by replicating previous findings on its relationship with the ipsilateral silent period (iSP) and with performance in bimanual coordination. Moreover, we aimed at inducing a task-dependent modulation of transcallosal inhibition. A new s le of 32 healthy right-handed participants underwent behavioral motor tasks and TMS-EEG recording, in which left and right M1 were stimulated during bimanual tasks and during an iSP paradigm. Hypotheses and methods were preregistered before data collection. We successfully replicated our previous findings on the positive relationship between M1-P15 litude and the iSP normalized area. However, we did not confirm the relationship between M1-P15 latency and bimanual coordination. Finally, we show a task-dependent modulation of M1-P15 litude, which was affected by the characteristics of the bimanual task the participants were performing, but not by the contralateral hand activity during the iSP paradigm. The present results corroborate our previous findings in validating the M1-P15 as a reliable cortical marker of transcallosal inhibition, and provide novel evidence of its task-dependent modulation. Importantly, we demonstrate the feasibility of a preregistration approach in the TMS-EEG field to increase methodological rigor and transparency.
Publisher: Wiley
Date: 31-08-2023
DOI: 10.1111/EJN.16127
Abstract: Transcranial magnetic stimulation (TMS)‐evoked potentials (TEPs) are a promising proxy for measuring effective connectivity, that is, the directed transmission of physiological signals along cortico‐cortical tracts, and for developing connectivity‐based biomarkers. A crucial point is how stimulation parameters may affect TEPs, as they may contribute to the general variability of findings across studies. Here, we manipulated two TMS parameters (i.e. current direction and pulse waveform) while measuring ( a ) an early TEP component reflecting contralateral inhibition of motor areas, namely, M1‐P15, as an operative model of interhemispheric cortico‐cortical connectivity, and ( b ) motor‐evoked potentials (MEP) for the corticospinal pathway. Our results showed that these two TMS parameters are crucial to evoke the M1‐P15, influencing its litude, latency, and replicability. Specifically, ( a ) M1‐P15 litude was strongly affected by current direction in monophasic stimulation ( b ) M1‐P15 latency was significantly modulated by current direction for monophasic and biphasic pulses. The replicability of M1‐P15 was substantial for the same stimulation condition. At the same time, it was poor when stimulation parameters were changed, suggesting that these factors must be controlled to obtain stable single‐subject measures. Finally, MEP latency was modulated by current direction, whereas non‐statistically significant changes were evident for litude. Overall, our study highlights the importance of TMS parameters for early TEP responses recording and suggests controlling their impact in developing connectivity biomarkers from TEPs. Moreover, these results point out that the excitability of the corticospinal tract, which is commonly used as a reference to set TMS intensity, may not correspond to the excitability of cortico‐cortical pathways.
Publisher: Elsevier BV
Date: 06-2022
DOI: 10.1016/J.CORTEX.2022.03.007
Abstract: When acting together, we may represent not only our own in idual goals but also a collective goal. Although behavioural evidence suggests that agents' motor plans might be related to collective goals, direct neurophysiological evidence of whether collective goals are motorically represented is still scarce. The aim of the present transcranial magnetic stimulation (TMS) study is to begin to fill this gap. A participant and a confederate were asked to sequentially perform a two-choice reaction time task by acting on pressure sensors. In their own turn, they saw a cue indicating whether to lift their fingers from (or to press them on) a pressure sensor to shoot a ball across the screen as fast as possible. The confederate responded with the right hand, the participant with the left hand. While the confederate acted on the sensor, the participant's motor evoked potentials (MEPs) were collected from the right Extensor Carpi Ulnaris. If participants represent their own and the confederate's actions as being directed to a collective goal, MEPs litude should be modulated according to the action the confederate should perform. To test this conjecture, we contrasted three conditions: a Joint condition, in which both players worked together with their collective goal being to shoot the ball to get it to a common target, a Parallel condition, in which the players performed exactly the same task but received independent outcomes for their performance, and a Competitive condition, in which the outcome of the game still depended on the other player performance, but without the collective goal feature. Results showed no MEPs modulation according to the confederate's action in the Joint condition. Post-hoc exploratory analyses both provide some hints about this negative finding and also suggest possible improvements (i.e., adopting a different dependent variable, avoiding task-switching between conditions) for testing our hypothesis that collective goal can be represented motorically.
Publisher: Elsevier BV
Date: 05-2020
Publisher: Elsevier BV
Date: 2023
Publisher: Cold Spring Harbor Laboratory
Date: 30-08-2019
DOI: 10.1101/752766
Abstract: Substantial evidence has shown that ongoing neural activity significantly contributes to how the brain responds to upcoming stimuli. In visual perception, a considerable portion of trial-to-trial variability can be accounted for by prestimulus magneto/electroencephalographic (M/EEG) alpha oscillations, which play an inhibitory function by means of cross-frequency interactions with gamma-band oscillations. Despite the fundamental theories on the role of oscillations in perception and cognition, a clear theorization of the neural mechanisms underlying prestimulus activity effects that includes electrophysiological phenomena at different scales (e.g., local field potentials and macro-scale M/EEG) is still missing. Here, we present a model called the oscillation-based probability of response (OPR), which directly assesses the link between meso-scale neural mechanisms, macro-scale M/EEG, and behavioural outcome. The OPR model includes distinct meso-scale mechanisms through which alpha oscillations modulate M/EEG gamma activity, namely, by decreasing a) the litude and/or b) the degree of neural synchronization of gamma oscillations. Crucially, the OPR model makes specific predictions on the effects of these mechanisms on visual perception, as assessed through the psychometric function. The oscillation-based probability of response (OPR) is grounded on a psychophysical approach focusing on the psychometric function estimation and may be highly informative in the study of ongoing brain activity because it provides a tool for distinguishing different neural mechanisms of alpha-driven modulation of sensory processing.
Publisher: Elsevier BV
Date: 03-2021
Publisher: Frontiers Media SA
Date: 12-08-2022
DOI: 10.3389/FNINS.2022.896746
Abstract: In the seed-based method for studying functional connectivity (FC), seed selection is relevant. Here, we propose a new methodological approach for resting-state FC analysis of hand motor networks using the in idual hand motor hotspot (hMHS) as seed. Nineteen right-handed healthy volunteers underwent a transcranial magnetic stimulation (TMS) session and resting-state fMRI. For each subject, the hMHS in both hemispheres was identified by TMS with the contralateral abductor pollicis brevis muscle as the target, the site eliciting the highest and most reliable motor-evoked potentials. Seed regions were built on coordinates on the cortex corresponding to the in idual left and right hMHSs. For comparison, the left and right Brodmann’s area 4 (BA4) masks extracted from a standard atlas were used as seed. The left and right hMHSs showed FC patterns at rest mainly including sensorimotor regions, with a bilateral connectivity only for the left hMHS. The statistical contrast BA4 & hMHS for both hemispheres showed different extension and lateralization of the functionally connected cortical regions. On the contrary, no voxels survived the opposite contrast (hMHS & BA4). This suggests that detection of in idual hand motor seeds by TMS allows to identify functionally connected motor networks that are more specific with respect to those obtained starting from the a priori atlas-based identification of the primary motor cortex.
Location: Italy
No related grants have been discovered for AGNESE ZAZIO.