Psychophysiology, 44:S97, 2007.
Reference-independent ERP Old/New Effects of Auditory and Visual Word Recognition Memory: Joint Extraction of Stimulus- and Response-locked Neuronal Generator Patterns
Jürgen Kayser1,2, Craig E. Tenke1,2, Nathan A. Gates2, Gerard E. Bruder1,2
1Department of Biopsychology, New York State Psychiatric Institute, New York, NY, USA; 2Department of Psychiatry, Columbia University College of Physicians and Surgeons, New York, NY, USA
Abstract
The interpretation of ERPs, which have been used to study episodic memory retrieval, crucially depends on the choice of EEG reference location and on analysis procedures. By contrast, temporal principal components analysis (unrestricted Varimax rotation of covariance loadings) of current source density (CSD) waveforms provides a data-driven, reference-free summary of generator patterns underlying scalp-recorded ERPs. To clarify polarity, topography and time course of recognition memory ERP old/new effects during matched visual and auditory continuous word recognition tasks, unrestricted temporal PCA jointly analyzed stimulus- and response-locked CSDs (31-channel, N = 40). Randomization tests provided unbiased statistics for complete factor topographies. Old/new left parietal source effects were complemented by old/new lateral frontocentral sink effects in both modalities, overlapping highly distinct (temporally and topographically) modality-specific P3 sources occurring approximately 160 ms before response onset. A sharp mid-frontal sink 45 ms post-response terminated the frontoparietal generator pattern, showed old/new effects consistent with bilateral activation of anterior cingulate and supplementary motor area, and preceded similar activity extending posteriorly along the longitudinal fissure. These methods separated old/new stimulus source (pre-response) and response sink (post-response) effects from motor and modality-specific ERPs, indicating considerable independence of modality-unspecific old/new effects within a frontal-parietal recognition memory network.
Key Words: recognition memory; current source density (CSD); principal components analysis (PCA)