THE EFFECT OF RETROSPECTIVELY CUED TASK RELEVANCE ON AUDITORY AWARENESS NEGATIVITY AND P3-RELATED NETWORKS

During investigations of perceptual awareness and its neural correlates, task relevance and participants’ responses are common confounds. To minimize these influences, we developed a paradigm in which the relevance of near-threshold tones only became apparent with a subsequent supra-threshold tone of the same frequency. Using combined MEG and EEG, we investigated auditory-cortex activity and the P3 network based on this indirect measure of tone detection. Simultaneous recordings of the pupil dilation response (PDR) provided information on subcortical attention and arousal systems.
All supra-threshold tones elicited strong auditory activity and a P3 in retro-splenial and insular cortex. For near-threshold tones, detected targets and correctly rejected non-targets elicited activity in the auditory and insular cortex. Activity for missed targets was only significant in the insular cortex. The difference between detected and missed targets was significant in both regions. A similar pattern was observed for the PDR, which was stronger for hit compared to miss trials for both near- and supra-threshold tones. Activation evoked by supra-threshold tones was generally stronger than for near-threshold tones in auditory cortex, the P3 network and the PDR.
These data confirm the differential activation of auditory cortex for detected targets, also known as auditory awareness negativity, in a situation where the detection task is not directly coupled to the near-threshold tones. In the P3 range, activity for near-threshold tones was only prominent in the insula. We suggest that insula activity and PDR reflect fluctuation in cortical and subcortical attention and arousal systems that influence near-threshold tone perception.