Test-retest stability and short-term habituation of the N1 and gamma band response

The gamma band response (GBR) is an exogenous, cortically generated, event-related potential that occurs between 20- and 170-msec post-stimulus onset. The auditory GBR is superimposed on the transient evoked middle and long latency cortical auditory evoked potentials and demonstrates a peak spectral frequency between 30 and 40 Hz. The present investigations were conducted to evaluate the test-retest stability and short-term habituation of the GBR. Both the GBR and N1 were recorded from six normal-hearing, neurologically intact subjects (Investigation 1, test-retest stability) and two subjects with intractable epilepsy with implanted subdural electrode grid arrays (Investigation 2, short-term habituation characteristics). For Investigation 1, the test-retest interval was 1 month. For Investigation 2, 300 samples were acquired per stimulus block (a 10-minute interval) and then subaveraged in blocks of 25 to 50 samples each. Results suggest that (1) like N1, the GBR shows high repeatability (qualitative) and test-retest stability (quantitative) and (2) the GBR does not demonstrate evidence of short-term habituation.