Spectral Analysis of the Averaged Auditory Evoked Response During Learning of Speech and Nonspeech Stimuli

Changes during learning and cortical hemispheric comparison of the averaged auditory evoked response (AER) to speech and nonspeech auditory stimuli were investigated. Right‐handed subjects were required to learn ensembles of eight CV syllables and five piano notes by the process of association while electroencephalographic (EEG) activity was being recorded from right and left temporal lobe electrode placements. Fourier analysis of the AERS was performed at 60%, 70%, 80%, 90%, and 100% performance levels. The first 24 spectral components were examined in terms of variation of the largest amplitude spectral component and amplitude variation of the 24 components divided into three frequency bands. A progressive decrease in the amplitude of the AER spectral components occurred during the learning of the speech and nonspeech stimuli. These variations were similar for both ensembles of stimuli and were viewed as reflecting increased cortical activation. Hemispheric differences were found in the AER spectrums that were related to the type of stimulus. Although confounding activity may have been introduced by the language‐oriented learning task, indications were that the right hemisphere plays a dominant role in nonspeech discriminations, with the left hemisphere being responsible for speech learning.