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Investigating the role of auditory deprivation in shaping the mechanisms of repetition suppression and novelty detection in the visual system.

Evgenia Bednaya;Emiliano Ricciardi;Pietro Pietrini;Davide Bottari
2019-01-01
2019
The ability to differentiate between repeated and novel information is a basic property of the visual system which, in turn, allows environmental change detection. When stimuli are repeated, the neural response generally reduces. This phenomenon is known as repetition suppression (RS) or adaptation. When instead a novel stimulus occurs, an enhancement of the neural activity is typically observed. To what extent the functional development in the visual system of RS and of novelty detection depends on sensory experience is unknown. Early auditory deprivation provides a unique model to study the degree of plasticity of such basic properties of the visual system. Indeed, following an auditory deprivation, the spared sensory modalities have been found to reorganize, and in some cases, have revealed a better functional tuning. The assessment of both RS and novelty detection in early-onset deaf individuals is lacking. EEG data were recorded from 11 early deaf individuals (ED) and 11 normal hearing controls (HC). Stimuli consisted of a circle continuously transitioning into an ellipse. In 76% of the trials, the circle deformed in one direction (Standard) and, in the rest of the trials, it deformed in the opposite direction (Deviant). A Deviant stimulus was always preceded by at least three Standard stimuli and occurred pseudo-randomly. Standard trials were used to assess RS to repeated visual stimuli. Deviant trials were used to investigate the response to an unexpected change in the visual stream. A white cross at the centre of the circle served both as a fixation point and as a target. Participants were asked to keep gaze at the fixation cross and press a button as fast as possible after its disappearance (17% of the trials). Thus, the task was orthogonal to Standard and Deviant stimuli occurrence. We compared the changes in brain oscillatory activity between ED and HC for RS, and for the response to the novel stimulus. Cluster-based permutation tests revealed that: (1) Stimulus repetition led to a significantly greater attenuation in the induced theta activity (4-7 Hz) in ED as compared to HC, from 200 to 300 ms after stimulus onset and across a broad range of electrodes. Conversely, the response to the novel stimulus elicited significantly lower degree of suppression of the induced activity in alpha band (8-12 Hz) in ED as compared to HC. The effects involved a broad range of posterior and central electrodes and peaked between 200 and 300 ms after the stimulus onset. Our results demonstrate how early-life experience can shape the development of two fundamental mechanisms of visual processing. We interpret both results as signs of a better functional tuning of the visual system in early deaf individuals.
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/20.500.11771/13499
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