Poster #: 98
Thursday, Sep 10, 2015
Regularity encoding in the human auditory brainstem is enhanced by timing predictability of the upcoming sounds
Department of Psychiatry and Clinical Psychobiology, Institute for Brain, Cognition and Behavior (IR3C), University of Barcelona, Barcelona, Spain
Repeated presentation of a stimulus leads to reduced neural activity to it, a phenomenon known as repetition suppression (RS). In the auditory domain, repetition suppression has been observed in animal cortical and subcortical structures and in the human auditory cortex, and incidentally reported in the human inferior colliculus with fMRI. Moreover, timing regularity of the ongoing stimulation influences the encoding of the repetitive environment at the level of the auditory cortex. However, before auditory information reaches the cortex, it is deeply processed in the auditory brainstem, which has the ability to encode context–dependent information. This study was set out to investigate how a repetitive environment is encoded at the level of the auditory brainstem and ascertain whether the described influence of timing regularity on the auditory cortex can be also observed at earlier stages of the auditory hierarchy. Here we recorded the human auditory brainstem frequency following response (FFR) to consonant–vowel stimuli (/wa/) delivered in two timing conditions (predictable and unpredictable) among a six–talker babble background. In the predictable timing condition, stimuli were delivered with isochronous stimulus onset–to–onset intervals (366 ms) and in the unpredictable timing condition, onset–to–onset time varied randomly between 183 and 549 ms. Our results confirm that repetition suppression is observable at the level of the human auditory brainstem and demonstrate that timing predictability influences the brainstem response to repetitive sounds, eliciting a better and faster encoding of regularities.