Resumen de Regularity encoding in the auditory brain as revealed by human evoked potentials

Jordi Costa Faidella

• Acoustic regularity encoding has been associated with a decrease of the neural response to repeated stimulation underlying the representation of auditory objects in the brain. The present thesis encloses two studies that sought to assess the neural correlates of acoustic regularity encoding in the human auditory system, by means of analyzing auditory evoked potentials. Study I was conducted at the Cognitive Neuroscience Research Group, at the Faculty of Psychology of the University of Barcelona (Barcelona, Catalonia, Spain), under the direct supervision of Dr. Carles Escera. This study aimed to explore the dynamics of adaptation of the auditory evoked potentials to probabilistic stimuli embedded in a complex sequence of sounds. The main outcome of this study was the demonstration that the amplitude of auditory evoked potentials adapts to the complex history of stimulation with different time constants concurrently: it adapts faster to local and slower to global probabilities of stimulation. This study also showed that auditory evoked potential amplitudes correlate with stimulus expectancy as defined by a combination of local and global stimulus probabilities. Study II was conducted at the Institute of Child Health (ICH), at the University College of London (UCL; London, United Kingdom), under the direct supervision of Dr. Torsten Baldeweg. This study aimed to explore the influence of timing predictability in the neural adaptation to probabilistic stimuli. The main outcome of this study was the demonstration that timing predictability enhances the repetition-related modulation of the auditory evoked potentials amplitude, being essential for repetition effects at early stages of the auditory processing hierarchy.