Mental Time Travel (MTT) represents the ability to cognitively move through time, envisioning oneself at different temporal moments—Present, Past, or Future—while ordering events along the Mental Time Line (MTL). Several studies demonstrated that, in the Western culture, Time is cognitively represented along a horizontal line which is spatially oriented from left to right. This spatial representation is configured from an egocentric perspective, defining the directionality of temporal flow from the Past, located on the left portion of the MTL, towards the Future, represented on the right. The ability to mentally navigate the spatial representation of Time can be modulated by the spatial attention deviation induced by prismatic adaptation, and can be affected by the objective temporal distance of the events. However, the effects of temporal distance as perceived by the subject have never been investigated, and it remains unclear how such manipulations modulate the activity of the brain network subtending MTT. Therefore, the purpose of this doctoral thesis is to explore the neural correlates underlying the modulation of MTT by means of two functional Magnetic Resonance (fMRI) studies. In Experiment 1, thirty-seven healthy volunteers underwent an MTT task using a single-event protocol, both before and after prismatic adaptation with spatial attention deviation towards the left, corresponding to the representation of the past. Inside the MRI scanner, participants were asked to mentally project themselves (Self-Projections) into either the Present, or the Past (10 years ago), or the Future (in 10 years), and judge whether a series of events were either past or future (Self-Reference), relatively to the temporal Self Projection. In this study we showed improved performance for projection and reference to the past, following the spatial attention deviation to the left induced by the prismatic adaptation; furthermore, we revealed that this improvement is mediated by the modulation of activity in the bilateral inferior parietal lobule and decreased activity in the left superior frontal gyrus. Spatial attention deviation during the task was mediated by bilateral activation of the superior temporal gyrus. The effect of perceived temporal distance of events was studied in Experiment 2. Thirty-three of the participants who took part in the first experiment, subsequently provided an estimate of the perceived distance, relative to the temporal projection, for each task event. Parametric analyses of the BOLD signal using these estimates as factors allowed to identify the brain regions where activity during MTT is modulated by the perceived temporal distance. This study showed how events, both past and future, perceived as close, affect Mental Time Travel performance. Furthermore, this effect involves the angular gyrus bilaterally, retrosplenial cortex, temporo-parietal regions, and middle and superior frontal gyri, regions which could mediate the spatial representation of time. Additionally, future events that are perceived as close recruit the left parahippocampal and lingual gyri and the right cerebellum, which might be implicated in this task for their role in imaginative functions. In summary, the present studies have thus further confirmed that time and space share the modality of cognitive representation, and have identified the brain networks responsible for modulating Mental Time Travel in humans.

Mental Time Travel (MTT) è l’abilità di viaggiare mentalmente nel tempo, immaginandosi in diversi momenti temporali, Presente, Passato o Futuro, e ordinando gli eventi collocandoli lungo la linea mentale del tempo (Mental Time Line - MTL). Numerosi studi hanno dimostrato che nella cultura occidentale il Tempo viene cognitivamente rappresentato su una linea orizzontale spazialmente orientata da sinistra a destra. Questa rappresentazione spaziale ha una prospettiva egocentrica che definisce la direzionalità del flusso temporale dal Passato, collocato nella porzione sinistra della MTL, al Futuro, rappresentato nella porzione destra. La capacità di muoversi mentalmente lungo la MTL può essere influenzata dalla modulazione dell’attenzione spaziale mediante l’adattamento prismatico ed è influenzata dalla distanza temporale oggettiva degli eventi stessi. Tuttavia, in letteratura gli effetti della distanza temporale percepita dal soggetto non sono mai stati indagati e non è ancora del tutto chiaro come tali manipolazioni modulino l’attività del network cerebrale coinvolto nel MTT. Pertanto, lo scopo di questa tesi di dottorato era esplorare i correlati neurali sottostanti la modulazione della capacità di MTT mediante due studi di risonanza magnetica funzionale (fMRI ). Nell’Esperimento 1, trentasette soggetti volontari sani hanno svolto un compito di MTT organizzato in un protocollo a singolo evento, prima e dopo adattamento prismatico con deviazione dell’attenzione verso sinistra, ovvero verso la rappresentazione del passato. All’interno dello scanner MRI, ai partecipanti veniva chiesto di proiettarsi mentalmente (Self-Projection) nel Presente, nel Passato (10 anni fa) o nel Futuro (tra 10 anni), e giudicare se una serie di eventi presentati uditivamente fossero passati o futuri relativamente al momento temporale in cui si erano proiettati (Self-Reference). Lo studio ha mostrato un miglioramento delle performance dei soggetti nel proiettarsi e ordinare gli eventi nel passato in seguito alla deviazione dell’attenzione spaziale verso sinistra indotta dai prismi. Dal punto di vista funzionale, questo effetto è risultato supportato dalla modulazione dell’attività del lobulo parietale inferiore bilateralmente e dal decremento dell’attività del giro frontale superiore di sinistra. L’effetto della deviazione dell’attenzione spaziale durante il compito è supportato dall’attivazione bilaterale del giro temporale superiore. L’effetto della percezione della distanza temporale degli eventi è stato studiato nell’Esperimento 2. Trentatré dei partecipanti del primo studio hanno successivamente fornito per ogni evento presentato una stima soggettiva della distanza temporale percepita rispetto alla posizione nel tempo in cui si erano proiettati. È stata quindi condotta un’analisi parametrica per individuare le regioni cerebrali in cui l’attività funzionale viene modulata dalla distanza temporale percepita durante il compito MTT. I risultati hanno mostrato che per eventi percepiti come vicini la capacità di Self-Reference risulti alterata, e che questo effetto è supportato dall’attività di giro angolare bilaterale, corteccia retro-spleniale, regioni temporo-parietali e giri frontali medio e superiore, aree che potrebbero mediare la rappresentazione spaziale del tempo. Infine, gli eventi futuri considerati vicini reclutano i giri paraippocampale e linguale di sinistra e il cervelletto di destra; sulla base dei dati della letteratura, la loro attività sembra rispecchiare la necessità di richiamare funzioni immaginative per svolgere il compito. In conclusione, gli studi della presente tesi hanno permesso di confermare che la rappresentazione cognitiva di tempo e spazio è condivisa e di individuare i network cerebrali responsabili della modulazione della capacità di Mental Time Travel in vivo.

Basi neurali della modulazione della capacità di Mental Time Travel / Claudia Casadio , 2024 Mar 18. 36. ciclo, Anno Accademico 2022/2023.

Basi neurali della modulazione della capacità di Mental Time Travel

CASADIO, CLAUDIA
2024

Abstract

Mental Time Travel (MTT) represents the ability to cognitively move through time, envisioning oneself at different temporal moments—Present, Past, or Future—while ordering events along the Mental Time Line (MTL). Several studies demonstrated that, in the Western culture, Time is cognitively represented along a horizontal line which is spatially oriented from left to right. This spatial representation is configured from an egocentric perspective, defining the directionality of temporal flow from the Past, located on the left portion of the MTL, towards the Future, represented on the right. The ability to mentally navigate the spatial representation of Time can be modulated by the spatial attention deviation induced by prismatic adaptation, and can be affected by the objective temporal distance of the events. However, the effects of temporal distance as perceived by the subject have never been investigated, and it remains unclear how such manipulations modulate the activity of the brain network subtending MTT. Therefore, the purpose of this doctoral thesis is to explore the neural correlates underlying the modulation of MTT by means of two functional Magnetic Resonance (fMRI) studies. In Experiment 1, thirty-seven healthy volunteers underwent an MTT task using a single-event protocol, both before and after prismatic adaptation with spatial attention deviation towards the left, corresponding to the representation of the past. Inside the MRI scanner, participants were asked to mentally project themselves (Self-Projections) into either the Present, or the Past (10 years ago), or the Future (in 10 years), and judge whether a series of events were either past or future (Self-Reference), relatively to the temporal Self Projection. In this study we showed improved performance for projection and reference to the past, following the spatial attention deviation to the left induced by the prismatic adaptation; furthermore, we revealed that this improvement is mediated by the modulation of activity in the bilateral inferior parietal lobule and decreased activity in the left superior frontal gyrus. Spatial attention deviation during the task was mediated by bilateral activation of the superior temporal gyrus. The effect of perceived temporal distance of events was studied in Experiment 2. Thirty-three of the participants who took part in the first experiment, subsequently provided an estimate of the perceived distance, relative to the temporal projection, for each task event. Parametric analyses of the BOLD signal using these estimates as factors allowed to identify the brain regions where activity during MTT is modulated by the perceived temporal distance. This study showed how events, both past and future, perceived as close, affect Mental Time Travel performance. Furthermore, this effect involves the angular gyrus bilaterally, retrosplenial cortex, temporo-parietal regions, and middle and superior frontal gyri, regions which could mediate the spatial representation of time. Additionally, future events that are perceived as close recruit the left parahippocampal and lingual gyri and the right cerebellum, which might be implicated in this task for their role in imaginative functions. In summary, the present studies have thus further confirmed that time and space share the modality of cognitive representation, and have identified the brain networks responsible for modulating Mental Time Travel in humans.
Neural bases of the modulation of the Mental Time Travel ability.
18-mar-2024
LUI, Fausta
BENUZZI, Francesca
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11380/1334926
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