title: Is the auditory evoked P2 response a biomarker of learning?
abstract: Even though auditory training exercises for humans have been shown to improve certain perceptual skills of individuals with and without hearing loss, there is a lack of knowledge pertaining to which aspects of training are responsible for the perceptual gains, and which aspects of perception are changed. To better define how auditory training impacts brain and behavior, electroencephalography (EEG) and magnetoencephalography (MEG) have been used to determine the time course and coincidence of cortical modulations associated with different types of training. Here we focus on P1-N1-P2 auditory evoked responses (AEP), as there are consistent reports of gains in P2 amplitude following various types of auditory training experiences; including music and speech-sound training. The purpose of this experiment was to determine if the auditory evoked P2 response is a biomarker of learning. To do this, we taught native English speakers to identify a new pre-voiced temporal cue that is not used phonemically in the English language so that coinciding changes in evoked neural activity could be characterized. To differentiate possible effects of repeated stimulus exposure and a button-pushing task from learning itself, we examined modulations in brain activity in a group of participants who learned to identify the pre-voicing contrast and compared it to participants, matched in time, and stimulus exposure, that did not. The main finding was that the amplitude of the P2 auditory evoked response increased across repeated EEG sessions for all groups, regardless of any change in perceptual performance. What's more, these effects are retained for months. Changes in P2 amplitude were attributed to changes in neural activity associated with the acquisition process and not the learned outcome itself. A further finding was the expression of a late negativity (LN) wave 600-900 ms post-stimulus onset, post-training exclusively for the group that learned to identify the pre-voiced contrast.
authors.affiliation: Department of Speech and Hearing Sciences, University of Washington Seattle, WA, USA.
authors.forename: Kelly L
authors.initials: KL
authors.lastname: Tremblay
authors.affiliation: Baycrest Centre, Rotman Research Institute Toronto, ON, Canada ; Department of Medical Biophysics, University of Toronto Toronto, ON, Canada.
authors.forename: Bernhard
authors.initials: B
authors.lastname: Ross
authors.affiliation: Department of Speech and Hearing Sciences, University of Washington Seattle, WA, USA ; Department of Radiology, Integrated Brian Imaging Center, University of Washington Seattle, WA, USA.
authors.forename: Kayo
authors.initials: K
authors.lastname: Inoue
authors.affiliation: Department of Speech and Hearing Sciences, University of Washington Seattle, WA, USA.
authors.forename: Katrina
authors.initials: K
authors.lastname: McClannahan
authors.affiliation: Life Sciences Department, Royal Military Academy Brussels, Belgium ; Unité de Recherche en Neurosciences Cognitives, Centre de Recherches en Cognition et Neurosciences Université Libre de Bruxelles Brussels, Belgium.
authors.forename: Gregory
authors.initials: G
authors.lastname: Collet
keywords: ERP; P2; auditory; electrophysiology; exposure; learning; rehabilitation; training