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Open Access Highly Accessed Research

EEG correlates of verbal and nonverbal working memory

Grace Hwang12, Joshua Jacobs2, Aaron Geller2, Jared Danker1, Robert Sekuler1 and Michael J Kahana2*

Author Affiliations

1 Volen Center for Complex Systems, Brandeis University, Waltham, MA, 02454, USA

2 Department of Psychology, University of Pennsylvania, Philadelphia, PA, 19104, USA

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Behavioral and Brain Functions 2005, 1:20  doi:10.1186/1744-9081-1-20

Published: 15 November 2005

Abstract

Background

Distinct cognitive processes support verbal and nonverbal working memory, with verbal memory depending specifically on the subvocal rehearsal of items.

Methods

We recorded scalp EEG while subjects performed a Sternberg task. In each trial, subjects judged whether a probe item was one of the three items in a study list. Lists were composed of stimuli from one of five pools whose items either were verbally rehearsable (letters, words, pictures of common objects) or resistant to verbal rehearsal (sinusoidal grating patterns, single dot locations).

Results

We found oscillatory correlates unique to verbal stimuli in the θ (4–8 Hz), α (9–12 Hz), β (14–28 Hz), and γ (30–50 Hz) frequency bands. Verbal stimuli generally elicited greater power than did nonverbal stimuli. Enhanced verbal power was found bilaterally in the θ band, over frontal and occipital areas in the α and β bands, and centrally in the γ band. When we looked specifically for cases where oscillatory power in the time interval between item presentations was greater than oscillatory power during item presentation, we found enhanced β activity in the frontal and occipital regions.

Conclusion

These results implicate stimulus-induced oscillatory activity in verbal working memory and β activity in the process of subvocal rehearsal.