Poster #: 91
Topic: Neuronal models
Wednesday, Sep 9, 2015
Stimulus-specific adaptation in the late auditory-evoked cortical potentials exhibits long memory and sensitivity to sequential stimulus relationships
1Institute of Hearing Research, Medical Research Council, Nottingham, United Kingdom
Auditory neural responses tend to be suppressed, or “adapted”, by preceding stimuli, and the amount of adaptation tends greater when the current and preceding stimuli are the same than when they are different. Initially, this stimulus-specific adaptation (SSA) was thought of as a passive process of neural fatigue, to be contrasted with the active processes underlying the mismatch negativity (MMN), a scalp-recorded response to deviant, or “oddball”, sounds. Subsequently, however, SSA was observed in single-neuron responses and evidence was found suggesting that single-neuron SSA shares many of the complex properties of the MMN. Here, we used special types of oddball sequences and analysis techniques to estimate the memory span, and investigate the properties, of SSA in the stimulus-driven deflections of the late auditory-evoked cortical scalp potentials in humans. Different deflections differed starkly in their adaptational properties. The earliest measured deflection, the P1, showed little evidence of SSA at all. For the latest deflection, the P2, SSA mostly depended on the short-term stimulus history and was consistent with the adaptational effects of each preceding stimulus separately, irrespective of any stimulus relationships. In contrast, for the middle deflection, the N1, SSA was mostly dependent on the longer-term stimulus history and seemed to be strongly influenced by sequential stimulus relationships. These results indicate that SSA in human auditory cortex represents a complex and multi-faceted phenomenon, which is unlikely to reflect a unitary causal mechanism.