Adaptation Patterns and Their Associations with Mismatch Negativity: A
Roving Electroencephalogram Paradigm with Expectations Maintained
Abstract
Adaptation is defined as reduced neural activation following repeated
stimulus presentation. While numerous previous electroencephalogram
studies used either one repetition or multiple repetitions to elicit
adaptation in event-related potentials, the adaptation patterns under
controlled expectations manifested in the two main auditory components,
N1 and P2, are still largely unknown. In addition, multiple repetitions
were used in mismatch negativity experiments to measure deviance
detection, but how adaptation in different time points contributes to
the mismatch negativity remains unclear. Therefore, in the present
study, 37 healthy adults participated in an electroencephalogram
experiment with a pure tone roving paradigm and a random stimulus
arrangement to maintain expectations. The amplitudes were traced along
with the first ten tones in the auditory event-related potentials
components, N1 and P2, to examine the adaptation patterns. Results
showed an L-shaped adaptation in the N1 with a large decrease after the
first repetition (N1 initial adaptation), and a continuous, linear
amplitude increase in the P2 even after the first repetition (P2
subsequent adaptation), possibly indicating memory trace formation.
Regression results showed that the peak amplitudes of the N1 initial
adaptation and the P2 subsequent adaptation significantly explained the
variance in the mismatch negativity amplitude. The results indicate
distinct adaptation patterns for multiple repetitions in different
components and suggest that the mismatch negativity combines two
processes as indicated by the initial adaptation in the N1 and a
continuous memory trace effect in the P2. Separating the two processes
may be relevant for models of cognitive processing and clinical
disorders.