Hemispatial PCA dissociates temporal from parietal ERP generator patterns: CSD components in healthy adults and depressed patients during a dichotic oddball task.
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.
Tenke
Craig E
CE
Division of Cognitive Neuroscience, New York State Psychiatric Institute, New York, NY 10032, USA. tenkecr@pi.cpmc.columbia.edu
Kayser
Jürgen
J
Shankman
Stewart A
SA
Griggs
Carlye B
CB
Leite
Paul
P
Stewart
Jonathan W
JW
Bruder
Gerard E
GE
D000328:Adult; D001288:Attention / Q000502:physiology; D001307:Auditory Perception / Q000502:physiology*; D001931:Brain Mapping; D016022:Case-Control Studies; D003866:Depressive Disorder / Q000503:physiopathology*; D004007:Dichotic Listening Tests; D004192:Discrimination, Psychological / Q000502:physiology; D018913:Event-Related Potentials, P300 / Q000502:physiology; D005072:Evoked Potentials, Auditory / Q000502:physiology*; D005260:Female; D007839:Functional Laterality / Q000502:physiology; D006801:Humans; D008297:Male; D010296:Parietal Lobe / Q000502:physiology*; D010700:Phonetics; D025341:Principal Component Analysis; D011930:Reaction Time / Q000502:physiology; D012016:Reference Values; D013028:Space Perception / Q000502:physiology; D013702:Temporal Lobe / Q000502:physiology*