Auditory Processing under Cross-Modal Visual Load Investigated with Simultaneous EEG-fMRI

Christina Regenbogen,Maarten De Vos,Thilo Kellermann,Ute Habel,Carolin Mößnang,Irene Neuner,Bruce I Turetsky,Stefan Debener,Andreas Finkelmeyer,Francesco Di Russo

doi:10.1371/journal.pone.0052267

Abstract

Cognitive task demands in one sensory modality (T1) can have beneficial effects on a secondary task (T2) in a different modality, due to reduced top-down control needed to inhibit the secondary task, as well as crossmodal spread of attention. This contrasts findings of cognitive load compromising a secondary modality’s processing. We manipulated cognitive load within one modality (visual) and studied the consequences of cognitive demands on secondary (auditory) processing. 15 healthy participants underwent a simultaneous EEG-fMRI experiment. Data from 8 participants were obtained outside the scanner for validation purposes. The primary task (T1) was to respond to a visual working memory (WM) task with four conditions, while the secondary task (T2) consisted of an auditory oddball stream, which participants were asked to ignore. The fMRI results revealed fronto-parietal WM network activations in response to T1 task manipulation. This was accompanied by significantly higher reaction times and lower hit rates with increasing task difficulty which confirmed successful manipulation of WM load. Amplitudes of auditory evoked potentials, representing fundamental auditory processing showed a continuous augmentation which demonstrated a systematic relation to cross-modal cognitive load. With increasing WM load, primary auditory cortices were increasingly deactivated while psychophysiological interaction results suggested the emergence of auditory cortices connectivity with visual WM regions. These results suggest differential effects of crossmodal attention on fundamental auditory processing. We suggest a continuous allocation of resources to brain regions processing primary tasks when challenging the central executive under high cognitive load.

Highlights

The brain’s capacity to re-allocate resources and to deal with its attentional capacities is relevant for survival and serves adaptive functioning [1,2]
Post-hoc tests of hit rates showed a significant decrease from condition 0back to 2-back (t(14) = 3.92, p,.001) and from condition 1-back to 2-back (t(14) = 3.84, p = .013)
The present study investigated how increasing visual working memory (WM)-load (T1) affected secondary fundamental auditory processing (T2)

Summary

Introduction

The brain’s capacity to re-allocate resources and to deal with its attentional capacities is relevant for survival and serves adaptive functioning [1,2]. The results can be subsumed under different theoretical frameworks: The ‘automaticity theory’ [6] states automatic processing to be present in the unattended secondary task and immunity to cross-modal influences [7,8]. The ‘gain-load theory’ [1] suggests that the primarily engaged modality uses the limited capacities which causes inhibition and thereby decreased processing of secondary input. This was supported by others [10] and moderated by the assumption of differential effects on undistractable and distractable components of crossmodal attention (e.g. reduced distraction effect but intact automatic change-detection mechanisms, [11])

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Conclusion