Auditory attention in young adults: a P300 study

Objectives: Deficits in auditory attention switching have been identified as a potential underlying problem in some individuals who struggle with speech perception in the presence of noise. The purpose of this study was therefore to investigate the underlying markers of this skill using adult participants. It is hoped that by developing a greater understanding of the processes involved, we may work towards the long-term aim of developing a screening test that is able to identify deficits in auditory attention switching to add to the auditory processing disorder (APD) test battery. Methods: Eight normal-hearing adults participated in this study. Each participant was presented 2 blocks of stimuli trains at 10dB SNR. Each block consisted of three stimuli trains where position of /da/ was varied within the 2.5s train. One block referred to as discrimination paradigm had /da/ interspersed with /ba/ such that the presentation was /da, ba, ba/ with 60% probability of /da/ occurring in first position. The remaining two trains had /da/ occurring in either second or third position with 10% probability. The other block or control paradigm was identical to the first paradigm with only /da/ present. The participants were asked to press the response button whenever they heard /da/. CAEP data was collected from 25 electrodes. P1-N1-P2 and P300 were evaluated for /da/ when presented in different positions. Wavelet time-frequency analysis was performed to analyse the epoched frequency band power information and cluster permutation statistics was used to test the differences. Results: Significantly larger N1-P2 were observed for the control block compared to discriminative block. P300 was elicited for both second and third positions in the discrimination paradigm. P300 was not significantly different at Pz between the second and third position but was found to be significantly larger at Fz for second position compared to the third position (p=0.041). A cluster-based permutation test revealed that there was a significant left fronto-central left midline difference in the discrimination paradigm between the /da/ responses (frequencies : 38-42 Hz and timing 0.1 s and 0.16 s relative to aligned 'da' stimulus onset) (p<0.05). Hence 38-42 Hz region within gamma band power showed significant differences with a p-value of 0.01. Conclusion: These results are preliminary, P300 showed some evidence of the selective attention mechanism in current research. In addition, time-frequency analysis also showed that there were differences in the gamma (38-42Hz) band power which may be associated with selective attention.