Novelty P3 Reductions in Depression: Characterization Using Principal Components Analysis (PCA) of Current Source Density (CSD) Waveforms
Craig E. Tenke1,2, Jürgen Kayser1,2, Jonathan W. Stewart2,3, Gerard E. Bruder1,2
1Division of Cognitive Neuroscience, New York State Psychiatric Institute, New York, NY, USA; 2Department of Psychiatry, Columbia University College of Physicians and Surgeons, New York, NY, USA; 3Depression Evaluation Service, New York State Psychiatric Institute, New York, NY, USA
Received 7 October 2008; revised 3 March 2009; accepted 5 March 2009.
Abstract
We previously reported a novelty P3 reduction in depressed patients compared to healthy controls (n = 20 per group) in a novelty oddball task using a 31-channel montage. In an independent replication and extension using a 67-channel montage (n = 49 per group), reference-free CSD waveforms were simplified and quantified by a temporal, covariance-based PCA (unrestricted Varimax rotation), yielding factor solutions consistent with other oddball tasks. A factor with a loadings peak at 343 ms summarized the target P3b source, as well as a secondary midline frontocentral source for novels and targets. An earlier novelty vertex source (NVS) at 241 ms was present for novels, but not targets, and was reduced in patients. Compatible CSD-PCA findings were also confirmed for the original low-density sample. Results are consistent with a reduced novelty response in clinical depression, involving the early phase of the frontocentral novelty P3.
Key Words: event-related potential (ERP); principal components analysis (PCA); current source density (CSD); surface Laplacian; oddball task; P300; depression; novelty P3