Phonological memory traces do not contain phonetic information.

We use a "varying standards" oddball paradigm and compare two phonetically differing conditions to find evidence that the auditory cortex has access to discrete phonological representations when making predictions about incoming speech sounds. Brain responses were recorded with a 128-electrode EEG system as subjects passively listened to synthetic speech sounds from a /dæ/-/tæ/ continuum. Deviant stimuli were compared to a control condition to obtain a mismatch negativity (MMN) response, indicative of a "surprise" at a stimulus that deviates from the memory trace. We tested two conditions with phonetically different varying standards - a "low-T" condition with VOT values of 60, 65, and 70 ms, and a "high-T" condition with VOT values of 75, 80, and 85 ms. The amplitude of the mismatch response is generally sensitive to acoustic distance. If the memory trace generated by the auditory cortex contains phonetic information about the standards, then a difference in mismatch amplitude is expected. However, if a phonological memory trace is used, every standard will be represented identically and no difference in mismatch amplitude will be observed. We found no distance effect in our results, indicating an absence of fine-grained phonetic information. This supports the claim that the auditory cortex has access to phonological category representations.