On the detection of auditory deviations: a pre-attentive activation model.

The conscious perception of infrequent deviant sounds occurring in a series of frequent standard sounds may in part be based on the output of an obligatorily operating deviance detection system. This system encodes invariances inherent to the recent auditory stimulation into short-lived representations of auditory sensory memory and compares each actual input with these representations. The underlying processes may be regarded as preattentive in the sense that they do not rely on the explicit intention of a person to detect deviants and that they may be active even in the absence of attention (although they may be prone to attentional modulations). The output of this feature-specific preattentive deviance detection system fuses into an integrated mismatch signal that in turn may activate subsequent processes that result in the triggering of a motor response.