Dataset Information

Hemispatial PCA dissociates temporal from parietal ERP generator patterns: CSD components in healthy adults and depressed patients during a dichotic oddball task.

ABSTRACT: Event-related potentials (31-channel ERPs) were recorded from 38 depressed, unmedicated outpatients and 26 healthy adults (all right-handed) in tonal and phonetic oddball tasks developed to exploit the perceptual challenge of a dichotic stimulation. Tonal nontargets were pairs of complex tones (corresponding to musical notes G and B above middle C) presented simultaneously to each ear (L/R) in an alternating series (G/B or B/G; 2-s fixed SOA). A target tone (note A) replaced one of the pair on 20% of the trials (A/B, G/A, B/A, A/G). Phonetic nontargets were L/R pairs of syllables (/ba/, /da/) with a short voice onset time (VOT), and targets contained a syllable (/ta/) with a long VOT. Subjects responded with a left or right button press to targets (counterbalanced across blocks). Target detection was poorer in patients than controls and for tones than syllables. Reference-free current source densities (CSDs; spherical spline Laplacian) derived from ERP waveforms were simplified and measured using temporal, covariance-based PCA followed by unrestricted Varimax rotation. Target-related N2 sinks and mid-parietal P3 sources were represented by CSD factors peaking at 245 and 440 ms. The P3 source topography included a secondary, left-lateralized temporal lobe maximum for both targets and nontargets. However, a subsequent hemispheric spatiotemporal PCA disentangled temporal lobe N1 and P3 sources as distinct factors. P3 sources were reduced in patients compared with controls, even after using performance as a covariate. Results are consistent with prior reports of P3 reduction in depression and implicate distinct parietal and temporal generators of P3 when using a dichotic oddball paradigm.

SUBMITTER: Tenke CE

PROVIDER: S-EPMC2271144 | biostudies-literature | 2008 Jan

REPOSITORIES: biostudies-literature

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Hemispatial PCA dissociates temporal from parietal ERP generator patterns: CSD components in healthy adults and depressed patients during a dichotic oddball task.

Tenke Craig E CE Kayser Jürgen J Shankman Stewart A SA Griggs Carlye B CB Leite Paul P Stewart Jonathan W JW Bruder Gerard E GE

International journal of psychophysiology : official journal of the International Organization of Psychophysiology 20070926 1

Event-related potentials (31-channel ERPs) were recorded from 38 depressed, unmedicated outpatients and 26 healthy adults (all right-handed) in tonal and phonetic oddball tasks developed to exploit the perceptual challenge of a dichotic stimulation. Tonal nontargets were pairs of complex tones (corresponding to musical notes G and B above middle C) presented simultaneously to each ear (L/R) in an alternating series (G/B or B/G; 2-s fixed SOA). A target tone (note A) replaced one of the pair on 2 ...[more]

PMID: 17963912

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Project description:Prior research suggests that event-related potentials (ERP) obtained during active and passive auditory paradigms, which have demonstrated abnormal neurocognitive function in schizophrenia, may provide helpful tools in predicting transition to psychosis. In addition to ERP measures, reduced modulations of EEG alpha, reflecting top-down control required to inhibit irrelevant information, have revealed attentional deficits in schizophrenia and its prodromal stage. Employing a three-stimulus novelty oddball task, nose-referenced 48-channel ERPs were recorded from 22 clinical high-risk (CHR) patients and 20 healthy controls detecting target tones (12% probability, 500Hz; button press) among nontargets (76%, 350Hz) and novel sounds (12%). After current source density (CSD) transformation of EEG epochs (-200 to 1000ms), event-related spectral perturbations were obtained for each site up to 30Hz and 800ms after stimulus onset, and simplified by unrestricted time-frequency (TF) principal components analysis (PCA). Alpha event-related desynchronization (ERD) as measured by TF factor 610-9 (spectral peak latency at 610ms and 9Hz; 31.9% variance) was prominent over right posterior regions for targets, and markedly reduced in CHR patients compared to controls, particularly in three patients who later developed psychosis. In contrast, low-frequency event-related synchronization (ERS) distinctly linked to novels (260-1; 16.0%; mid-frontal) and N1 sink across conditions (130-1; 3.4%; centro-temporoparietal) did not differ between groups. Analogous time-domain CSD-ERP measures (temporal PCA), consisting of N1 sink, novelty mismatch negativity (MMN), novelty vertex source, novelty P3, P3b, and frontal response negativity, were robust and closely comparable between groups. Novelty MMN at FCz was, however, absent in the three converters. In agreement with prior findings, alpha ERD and MMN may hold particular promise for predicting transition to psychosis among CHR patients.

Project description:Event-related potentials (ERPs) are often used in brain-computer interfaces (BCIs) for communication or system control for enhancing or regaining control for motor-disabled persons. Especially results from single-trial EEG classification approaches for BCIs support correlations between single-trial ERP detection performance and ERP expression. Hence, BCIs can be considered as a paradigm shift contributing to new methods with strong influence on both neuroscience and clinical applications. Here, we investigate the relevance of the choice of training data and classifier transfer for the interpretability of results from single-trial ERP detection. In our experiments, subjects performed a visual-motor oddball task with motor-task relevant infrequent (targets), motor-task irrelevant infrequent (deviants), and motor-task irrelevant frequent (standards) stimuli. Under dual-task condition, a secondary senso-motor task was performed, compared to the simple-task condition. For evaluation, average ERP analysis and single-trial detection analysis with different numbers of electrodes were performed. Further, classifier transfer was investigated between simple and dual task. Parietal positive ERPs evoked by target stimuli (but not by deviants) were expressed stronger under dual-task condition, which is discussed as an increase of task emphasis and brain processes involved in task coordination and change of task set. Highest classification performance was found for targets irrespective whether all 62, 6 or 2 parietal electrodes were used. Further, higher detection performance of targets compared to standards was achieved under dual-task compared to simple-task condition in case of training on data from 2 parietal electrodes corresponding to results of ERP average analysis. Classifier transfer between tasks improves classification performance in case that training took place on more varying examples (from dual task). In summary, we showed that P300 and overlaying parietal positive ERPs can successfully be detected while subjects are performing additional ongoing motor activity. This supports single-trial detection of ERPs evoked by target events to, e.g., infer a patient's attentional state during therapeutic intervention.

Dataset Information

Hemispatial PCA dissociates temporal from parietal ERP generator patterns: CSD components in healthy adults and depressed patients during a dichotic oddball task.

Publications

Hemispatial PCA dissociates temporal from parietal ERP generator patterns: CSD components in healthy adults and depressed patients during a dichotic oddball task.

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