In the present doctoral thesis, I have explored whether Hebbian learning may rule the functioning of cross-modal and sensory-motor networks of the human brain. To this aim, during my doctorate, I have developed and tested two novel Paired Associative Stimulation (PAS) protocols, a class of non-invasive brain stimulation techniques in which a peripheral, sensory, stimulation is repeatedly paired with a Transcranial Magnetic Stimulation (TMS) pulse to induce Hebbian associative plasticity. The two PAS protocols presented in my thesis target sensory-motor networks with mirror functioning, exploiting a visuo-tactile (cross-modal PAS), and a visuo-motor pathway (mirror PAS), respectively. In the first chapter of the present work, after a brief introduction to the concept of Hebbian associative plasticity, I will provide an exhaustive review of PAS protocols targeting sensory-motor systems, proposing a classification in three macro-categories: within-system, cross-systems, and cortico-cortical protocols, according to the characteristics of the paired stimulations. In the second chapter, I will describe the principal properties of the Mirror Neuron System (MNS) also considering its cross-modal (i.e., visuo-tactile) characteristics and the plastic mechanisms that are been hypothesize at the ground of the development of mirror neurons’ matching properties. In the third chapter, I will introduce the cross-modal PAS (cm-PAS), a novel cross-systems PAS developed to exploit the visuo-tactile mirroring properties of the primary somatosensory cortex (S1) to induce Hebbian associative plasticity in such primary sensory region. In a series of three experiments, timing dependency (Experiment 1), cortical (Experiment 2), and visual specificity (Experiment 3) of the protocol have been tested, by measuring changes in participants’ tactile acuity. In Experiment 3, also possible neurophysiological changes within S1 has been assessed, recording somatosensory-evoked potentials (SEP). Then, in a fourth experiment, cm-PAS timing dependency has been further investigated, testing the hypothesis that anticipatory, predictive-like, mechanisms within S1 may play a central role in the effectiveness of the protocol. In the fourth chapter, a second cross-systems PAS will be introduced: the mirror PAS (m-PAS) which exploits visuo-motor mirroring properties of the human brain. Differently from the cm-PAS, this second protocol targets visuo-motor integration within the MNS and aims at induce a novel, atypical, motor resonance phenomena (assessed recording motor-evoked potentials – MEPs) following Hebbian learning. In three experiments, timing dependency (Experiment 1), visual (Experiment 2), and cortical specificity (Experiment 3) of the protocol have been tested. Furthermore, in the third experiment, the behavioral effects of the m-PAS are explored, using an imitative compatibility task exploiting automatic imitation phenomenon. Finally, in the conclusive chapter, I will discuss theoretical, methodological, and clinical outcomes and future perspectives that arise from these two protocols and the related results.

Nella presente tesi di dottorato, ho esplorato se fenomeni di apprendimento Hebbiano possano governare il funzionamento dei sistemi cross-modali e sensorimotori del cervello umano. A tal fine, durante il mio dottorato, ho sviluppato e testato due nuovi protocolli Paired Associative Stimulation (PAS), una classe di tecniche di stimolazione cerebrale non invasiva in cui una stimolazione sensoriale periferica viene ripetutamente accoppiata con un impulso di stimolazione magnetica transcranica (TMS) su un’area bersaglio al fine di indurre plasticità associativa Hebbiana. I due protocolli PAS presentati nella mia tesi mirano a due sistemi cerebrali sensoriali-motori con funzionamento a specchio (tactile mirror system e action observation network), sfruttando rispettivamente una via cross-corticale visuo-tattile (cross-modal PAS) e una visuo-motoria (mirror PAS). Nel primo capitolo del presente lavoro, dopo una breve introduzione al concetto di plasticità associativa Hebbiana, fornirò una revisione esaustiva dei protocolli PAS che mirano ai sistemi sensorimotori, proponendo una classificazione in tre macro-categorie (within-system, cross-systems e cortico-cortical), a seconda delle caratteristiche delle stimolazioni accoppiate. Nel secondo capitolo descriverò le principali proprietà del sistema dei neuroni specchio (MNS) considerando anche le sue proprietà cross-modali visuo-tattili ed i meccanismi di plasticità neuronale che sono stati ipotizzati alla base dello sviluppo dei neuroni specchio. Nel terzo capitolo, introdurrò il cross-modal PAS (cm-PAS), un nuovo cross-systems PAS sviluppato per sfruttare le proprietà visuo-tattili della corteccia somatosensoriale primaria, al fine di indurre plasticità associativa Hebbiana in tale regione sensoriale. In una serie di tre esperimenti, ho testo la dipendenza temporale (Esperimento 1), la specificità corticale (Esperimento 2) e visiva (Esperimento 3) del protocollo, misurando possibili cambiamenti nell'acuità tattile dei partecipanti. Nell'esperimento 3, ho valutato anche possibili cambiamenti neurofisiologici all'interno di S1, registrando i potenziali evocati somatosensoriali. Infine, in un quarto esperimento, la dipendenza temporale del cm-PAS è stata ulteriormente studiata, testando l'ipotesi che meccanismi anticipatori di tipo predittivo possano svolgere un ruolo centrale nell'efficacia del protocollo. Nel quarto capitolo introdurrò un secondo cross-systems PAS: il mirror PAS (m-PAS) che sfrutta le proprietà ‘mirror’ visuo-motorie del cervello umano. A differenza del cm-PAS, questo secondo protocollo sfrutta la natura associativa dell'integrazione visuo-motoria all'interno del MNS, mirando a indurre un nuovo, atipico, fenomeno di risonanza motoria attraverso apprendimento Hebbiano. In tre esperimenti ho testato la dipendenza temporale (Esperimento 1), la specificità visiva (Esperimento 2) e corticale (Esperimento 3) del protocollo registrando i potenziali evocati motori durante la visione di semplici movimenti (i.e., risonanza motoria). Inoltre, nel terzo esperimento, ho esplorato anche possibili effetti comportamentali dell’m-PAS, utilizzando un compito di compatibilità imitativa che sfrutta il fenomeno dell'imitazione automatica. Infine, nel capitolo conclusivo, discuterò i risultati teorici, metodologici e clinici e le prospettive future che derivano da questi due protocolli.

(2021). Cross-modal plasticity in sensory-motor cortices and non-invasive brain stimulation techniques: new ways to explore and modulate brain plasticity. (Tesi di dottorato, Università degli Studi di Milano-Bicocca, 2021).

Cross-modal plasticity in sensory-motor cortices and non-invasive brain stimulation techniques: new ways to explore and modulate brain plasticity

GUIDALI, GIACOMO
2021

Abstract

In the present doctoral thesis, I have explored whether Hebbian learning may rule the functioning of cross-modal and sensory-motor networks of the human brain. To this aim, during my doctorate, I have developed and tested two novel Paired Associative Stimulation (PAS) protocols, a class of non-invasive brain stimulation techniques in which a peripheral, sensory, stimulation is repeatedly paired with a Transcranial Magnetic Stimulation (TMS) pulse to induce Hebbian associative plasticity. The two PAS protocols presented in my thesis target sensory-motor networks with mirror functioning, exploiting a visuo-tactile (cross-modal PAS), and a visuo-motor pathway (mirror PAS), respectively. In the first chapter of the present work, after a brief introduction to the concept of Hebbian associative plasticity, I will provide an exhaustive review of PAS protocols targeting sensory-motor systems, proposing a classification in three macro-categories: within-system, cross-systems, and cortico-cortical protocols, according to the characteristics of the paired stimulations. In the second chapter, I will describe the principal properties of the Mirror Neuron System (MNS) also considering its cross-modal (i.e., visuo-tactile) characteristics and the plastic mechanisms that are been hypothesize at the ground of the development of mirror neurons’ matching properties. In the third chapter, I will introduce the cross-modal PAS (cm-PAS), a novel cross-systems PAS developed to exploit the visuo-tactile mirroring properties of the primary somatosensory cortex (S1) to induce Hebbian associative plasticity in such primary sensory region. In a series of three experiments, timing dependency (Experiment 1), cortical (Experiment 2), and visual specificity (Experiment 3) of the protocol have been tested, by measuring changes in participants’ tactile acuity. In Experiment 3, also possible neurophysiological changes within S1 has been assessed, recording somatosensory-evoked potentials (SEP). Then, in a fourth experiment, cm-PAS timing dependency has been further investigated, testing the hypothesis that anticipatory, predictive-like, mechanisms within S1 may play a central role in the effectiveness of the protocol. In the fourth chapter, a second cross-systems PAS will be introduced: the mirror PAS (m-PAS) which exploits visuo-motor mirroring properties of the human brain. Differently from the cm-PAS, this second protocol targets visuo-motor integration within the MNS and aims at induce a novel, atypical, motor resonance phenomena (assessed recording motor-evoked potentials – MEPs) following Hebbian learning. In three experiments, timing dependency (Experiment 1), visual (Experiment 2), and cortical specificity (Experiment 3) of the protocol have been tested. Furthermore, in the third experiment, the behavioral effects of the m-PAS are explored, using an imitative compatibility task exploiting automatic imitation phenomenon. Finally, in the conclusive chapter, I will discuss theoretical, methodological, and clinical outcomes and future perspectives that arise from these two protocols and the related results.
BOLOGNINI, NADIA
Mirror Neuron System; Plasticità Hebbiana; TMS; Sistema motorio; Sistema somatosensor
Mirror Neuron System; Hebbian Plasticity; TMS; Motor system; Sistema somatosensor
M-PSI/02 - PSICOBIOLOGIA E PSICOLOGIA FISIOLOGICA
English
20-gen-2021
NEUROSCIENZE
33
2019/2020
open
(2021). Cross-modal plasticity in sensory-motor cortices and non-invasive brain stimulation techniques: new ways to explore and modulate brain plasticity. (Tesi di dottorato, Università degli Studi di Milano-Bicocca, 2021).
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/10281/306484
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