Cortical Response Variation with Different Sound Pressure Levels: A Combined Event-Related Potentials and fMRI Study

Irene Neuner,Wolfram Kawohl,Christine Wyss,Jorge Arrubla,Konrad Hitz,Tracy Warbrick,Frank Boers,N Jon Shah,Manuel S Malmierca

doi:10.1371/journal.pone.0109216

Irene Neuner, Wolfram Kawohl + Show 7 more

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https://doi.org/10.1371/journal.pone.0109216

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Abstract

IntroductionSimultaneous recording of electroencephalography (EEG) and functional magnetic resonance imaging (fMRI) provides high spatial and temporal resolution. In this study we combined EEG and fMRI to investigate the structures involved in the processing of different sound pressure levels (SPLs).MethodsEEG data were recorded simultaneously with fMRI from 16 healthy volunteers using MR compatible devices at 3 T. Tones with different SPLs were delivered to the volunteers and the N1/P2 amplitudes were included as covariates in the fMRI data analysis in order to compare the structures activated with high and low SPLs. Analysis of variance (ANOVA) and ROI analysis were also performed. Additionally, source localisation analysis was performed on the EEG data.ResultsThe integration of averaged ERP parameters into the fMRI analysis showed an extended map of areas exhibiting covariation with the BOLD signal related to the auditory stimuli. The ANOVA and ROI analyses also revealed additional brain areas other than the primary auditory cortex (PAC) which were active with the auditory stimulation at different SPLs. The source localisation analyses showed additional sources apart from the PAC which were active with the high SPLs.DiscussionThe PAC and the insula play an important role in the processing of different SPLs. In the fMRI analysis, additional activation was found in the anterior cingulate cortex, opercular and orbito-frontal cortices with high SPLs. A strong response of the visual cortex was also found with the high SPLs, suggesting the presence of cross-modal effects.

Highlights

Simultaneous recording of electroencephalography (EEG) and functional magnetic resonance imaging provides high spatial and temporal resolution
The EEG data were successfully corrected for gradient and pulse artefacts and the trial-average showed clear Auditory evoked potentials (AEPs) for the four sound pressure levels (SPLs) (Figure 1)
Increasing amplitudes were observed at higher SPLs, proving that the stimulation paradigm was successful in exhibiting loudness dependence of auditory evoked potentials (LDAEP)

Summary

Introduction

Simultaneous recording of electroencephalography (EEG) and functional magnetic resonance imaging (fMRI) provides high spatial and temporal resolution. Simultaneous recording of electroencephalography (EEG) and functional magnetic resonance imaging (fMRI) has shown a number of advantages that make this multimodal technique superior to fMRI alone [1,2,3,4,5,6,7]. Recording these multiple measures of brain activity at the same time, under the same physiological and psychological conditions is advantageous for many aspects of cognitive neuroscience, in particular, pharmacological challenge studies, sleep studies, studies investigating epilepsy or evoked potential studies [3,8,9]. It requires the synchronous activity of a large number of neurons to generate measurable electric potentials, it has the intrinsic problem of source localization uncertainly caused mostly by the skull and the inverse problem itself, lacking of good spatial resolution

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