Removing electroencephalographic artifacts by blind source separation

IntroductionSpatio‐temporal distributions of cortical activity to audio‐visual presentations of meaningless vowel‐consonant‐vowels and the effects of audio‐visual congruence/incongruence, with emphasis on the McGurk effect, were studied. The McGurk effect occurs when a clearly audible syllable with one consonant, is presented simultaneously with a visual presentation of a face articulating a syllable with a different consonant and the resulting percept is a syllable with a consonant other than the auditorily presented one.MethodsTwenty subjects listened to pairs of audio‐visually congruent or incongruent utterances and indicated whether pair members were the same or not. Source current densities of event‐related potentials to the first utterance in the pair were estimated and effects of stimulus–response combinations, brain area, hemisphere, and clarity of visual articulation were assessed.ResultsAuditory cortex, superior parietal cortex, and middle temporal cortex were the most consistently involved areas across experimental conditions. Early (<200 msec) processing of the consonant was overall prominent in the left hemisphere, except right hemisphere prominence in superior parietal cortex and secondary visual cortex. Clarity of visual articulation impacted activity in secondary visual cortex and Wernicke's area. McGurk perception was associated with decreased activity in primary and secondary auditory cortices and Wernicke's area before 100 msec, increased activity around 100 msec which decreased again around 180 msec. Activity in Broca's area was unaffected by McGurk perception and was only increased to congruent audio‐visual stimuli 30–70 msec following consonant onset.ConclusionsThe results suggest left hemisphere prominence in the effects of stimulus and response conditions on eight brain areas involved in dynamically distributed parallel processing of audio‐visual integration. Initially (30–70 msec) subcortical contributions to auditory cortex, superior parietal cortex, and middle temporal cortex occur. During 100–140 msec, peristriate visual influences and Wernicke's area join in the processing. Resolution of incongruent audio‐visual inputs is then attempted, and if successful, McGurk perception occurs and cortical activity in left hemisphere further increases between 170 and 260 msec.

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“…1997; Jung et al. 2000). Individual concatenated single‐trial epochs were decomposed with Infomax ICA.…”

Section: Methodsmentioning

confidence: 99%

Spatio‐temporal distribution of brain activity associated with audio‐visually congruent and incongruent speech and the McGurk Effect

2015

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“…Epochs containing eye blinks or movements (VEOG or HEOG exceeding 670 mV) around target onset (6200 ms), voltages exceeding 6150 mV or gradients exceeding 650 mV were rejected. Remaining ocular artifacts were removed using Independent Component Analysis (Jung et al, 2000). After this procedure, six participants had to be excluded, because they had fewer than 40 trials per within condition.…”

Section: Eeg Recording and Analysismentioning

confidence: 99%

Social conformity is due to biased stimulus processing: electrophysiological and diffusion analyses

Germar

Albrecht

Voss

et al. 2016

Social Cognitive and Affective Neuroscience

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Hundreds of studies have found that humans' decisions are strongly influenced by the opinions of others, even when making simple perceptual decisions. In this study, we aimed to clarify whether this effect can be explained by social influence biasing (early) perceptual processes. We employed stimulus evoked potentials, lateralized readiness potentials (LRPs) and a diffusion model analysis of reaction time data to uncover the neurocognitive processes underlying social conformity in perceptual decision-making. The diffusion model analysis showed that social conformity was due to a biased uptake of stimulus information and accompanied by more careful stimulus processing. As indicated by larger N1-amplitudes, social influence increased early attentional resources for stimulus identification and discrimination. Furthermore, LRP analyses revealed that stimulus processing was biased even in cases of non-conformity. In conclusion, our results suggest that the opinion of others can cause individuals to selectively process stimulus information supporting this opinion, thereby inducing social conformity. This effect is present even when individuals do not blindly follow the majority but rather carefully process stimulus information.

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“…Current EEG systems can have as few as four electrodes [11] or as many as 256 electrodes. Until recently, the use of EEG has been limited to stationary settings (i.e., settings where the subject is seated or prone) because of the susceptibility of EEG electrodes to movement and electromyographic artifacts [12][13][14]. However, we have recently demonstrated that these artifacts can be removed from high-density (256-channel) EEG using advanced computational methods; thus enabling the use of EEG during walking [15][16][17].…”

Section: Introductionmentioning

confidence: 99%

How Many Electrodes Are Really Needed for EEG-Based Mobile Brain Imaging?

Lau¹,

Gwin²,

Ferris³

2012

JBBS

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A noninvasive method for imaging the human brain during mobile activities could have far reaching benefits for studies of human motor control, for research and treatment of neurological disabilities, and for brain-controlled powered prosthetic limbs or orthoses. Several recent studies have demonstrated that electroencephalography (EEG) can be used to image the brain during locomotion provided that signal processing techniques, such as independent Component Analysis (ICA), are used to parse electrocortical activity from artifact contaminated EEG. However, these studies used high-density 256-channel EEG sensor arrays, which are likely too time-consuming to setup in a clinical or field setting. Therefore, it is important to evaluate how reducing the number of EEG channel signals affects the electrocortical source signals that can be parsed from EEG recorded during standing and walking while concurrently performing a visual oddball discrimination task. Specifically, we computed temporal and spatial correlations between electrocortical sources parsed from high-density EEG and electrocortical sources parsed from reduced-channel subsets of the original high-density EEG. For this task, our results indicate that on average an EEG montage with as few as 35 channels may be sufficient to record the two most dominate electrocortical sources (temporal and spatial R2 > 0.9). Correlations for additional electrocortical sources decreased linearly such that the least dominant sources extracted from the 35 channel dataset had temporal and spatial correlations of approximately 0.7. This suggests that for certain applications the number of EEG sensors used for mobile brain imaging could be vastly reduced, but researchers and clinicians must consider the expected distribution of relevant electrocortical sources when determining the number of EEG sensors necessary for a particular application.

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Removing electroencephalographic artifacts by blind source separation

Cited by 2,395 publications

References 23 publications

Spatio‐temporal distribution of brain activity associated with audio‐visually congruent and incongruent speech and the McGurk Effect

Spatio‐temporal distribution of brain activity associated with audio‐visually congruent and incongruent speech and the McGurk Effect

Social conformity is due to biased stimulus processing: electrophysiological and diffusion analyses

How Many Electrodes Are Really Needed for EEG-Based Mobile Brain Imaging?

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