Neural plasticity induced by different degrees of perturbation in auditory and visual sensory systems

Visual or auditory sensory deprivation represents a key model for studying experience-dependent plasticity. Different types of deprivations (congenital-late, temporary-permanent, peripheral-central) are characterized by a certain degree of perturbation of the typical sensory experience and can be represented in a three-dimensional space showing the distance from the typical experience. The dimensions are: (i) when the deprivation occurs, (ii) how long the deprivation lasts, and (iii) where is the barrier that causes the deprivation. Each dimension can be responsible for a low, medium, or high degree of perturbation. In this dissertation, visual and auditory deprivation models are employed to investigate unisensory and multisensory neural plasticity. The first study (low degree of perturbation) aimed to unveil whether short-term monocular deprivation in the adult brain can induce neural plasticity beyond the visual system. The second study (medium degree of perturbation), using the model of temporary deprivation, assessed whether neural tracking of speech envelope could develop even in the absence of auditory stimulation from birth. Finally, the third study (high degree of perturbation) investigated how cerebral visual impairment affects visuospatial processing. Neural oscillations were used as windows to investigate plasticity mechanisms; time-frequency analysis was employed when short stimuli were presented, and neural tracking when the stimuli were continuous. Results revealed that even a low degree of sensory perturbation induces plasticity that extends beyond the deprived modality (study 1); altered neural tracking develops following a medium degree perturbation (study 2); a high degree of perturbation has a widespread impact on neural activity (study 3). These results strengthen evidence of the pivotal role of sensory experience revealing multifaced aspects of experience-dependent plasticity. Modeling the degree of perturbation could be a helpful perspective for a deeper understanding of how neural dynamics are affected by different types of deprivation and for shedding light on ranges of flexibility in neural processing with potential clinical implications.