title: The effect of rehearsal rate and memory load on verbal working memory.
abstract: While many neuroimaging studies have investigated verbal working memory (WM) by manipulating memory load, the subvocal rehearsal rate at these various memory loads has generally been left uncontrolled. Therefore, the goal of this study was to investigate how mnemonic load and the rate of subvocal rehearsal modulate patterns of activity in the core neural circuits underlying verbal working memory. Using fMRI in healthy subjects, we orthogonally manipulated subvocal rehearsal rate and memory load in a verbal WM task with long 45-s delay periods. We found that middle frontal gyrus (MFG) and superior parietal lobule (SPL) exhibited memory load effects primarily early in the delay period and did not exhibit rehearsal rate effects. In contrast, we found that inferior frontal gyrus (IFG), premotor cortex (PM) and Sylvian-parietal-temporal region (area Spt) exhibited approximately linear memory load and rehearsal rate effects, with rehearsal rate effects lasting through the entire delay period. These results indicate that IFG, PM and area Spt comprise the core articulatory rehearsal areas involved in verbal WM, while MFG and SPL are recruited in a general supervisory role once a memory load threshold in the core rehearsal network has been exceeded.
authors.affiliation: Helen Wills Neuroscience Institute, University of California, Berkeley, Berkeley, CA 94720, USA. Electronic address: dfegen@gmail.com.
authors.forename: David
authors.initials: D
authors.lastname: Fegen
authors.affiliation: Rotman Research Institute, Baycrest Hospital, Toronto, ON M6A 2E1, Canada; Department of Psychology, University of Toronto, Toronto, ON M6A 2E1, Canada.
authors.forename: Bradley R
authors.initials: BR
authors.lastname: Buchsbaum
authors.affiliation: Helen Wills Neuroscience Institute, University of California, Berkeley, Berkeley, CA 94720, USA; Department of Psychology, University of California, Berkeley, Berkeley, CA 94720, USA.
authors.forename: Mark
authors.initials: M
authors.lastname: D'Esposito
mesh_terms: D000293:Adolescent; D000328:Adult; D001921:Brain / Q000502:physiology*; D001931:Brain Mapping; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D007858:Learning / Q000502:physiology*; D008279:Magnetic Resonance Imaging; D008297:Male; D008570:Memory, Short-Term / Q000502:physiology*; D055815:Young Adult
keywords: Memory load; Middle frontal gyrus; Subvocal rehearsal; Sylvian-parietal-temporal (area Spt); Verbal working memory; fMRI