报告摘要：

Auditory responses, both in humans and in animal models, are highly sensitive to context. For example, the rare stimuli in an oddball sequence evoke a number of specific components in the auditory event-related potentials, the best known of which is the Mismatch Negativity. Here I describe responses at the single-neuron level to oddball sequences, demonstrating that they are strong and robust in the ascending auditory system starting as early as the inferior colliculus. These responses seem to be computed de-novo at least twice, once in the inferior colliculus and a second time in auditory cortex, with somewhat different properties. Responses to rare tones are shaped not only by tone probability but also by how expected it is - for example, the responses to the same tones, with the same probability of occurrence, are smaller when they are embedded in periodic sequences in which they are expected than when they are embedded in random sequences, and broad-band stimuli evoke robust SSA in auditory cortex but only minor one, if any, at the IC. Finally, I discuss shortly some cellular mechanisms that may underlie the production and enhancement of these responses.