Processing of task-irrelevant sounds while performing a visual task : A study of auditory steady-state evoked potentials

Sammanfattning: Perceptual capacity and selection in attention have for long been an interest in cognitive science, with early theories of early selection to late selection. Hearing is an important subject to investigate when it comes to attention and early auditory processing can be investigated by using auditory steady state responses (ASSRs). Studies on ASSRs to irrelevant sounds have investigated the 40 Hz ASSR and concluded no effect of load. As studies on temporal activation of ASSRs indicate that lower and higher frequencies activate different stages of the auditory pathway, there is a need to investigate other frequencies than the 40 Hz. This study investigated the 20 Hz and 80 Hz amplitude modulations using EEG. The visual stimuli were a rapid stream of letters and varied between no load, low load, and high load. The auditory stimuli were an amplitude-modulated tone with a carrier frequency of 500 Hz, with three varying modulation frequencies: 20 Hz, 40 Hz, and 80 Hz. Load level and amplitude modulation alternated over 18 blocks. The statistical analysis was comprised of t tests and Bayes Factor. Results provided support for the null hypothesis for the 20 Hz frequency but were inconclusive for the 40 Hz and 80 Hz frequency. More data is needed to give a conclusion for effect of load for the 40 Hz and 80 Hz frequency. As we did not have enough data, we cannot say anything about the temporal activation of ASSRs in the brain.