title: Spatio-temporal dynamics of working memory maintenance and scanning of verbal information.
abstract: During verbal communication, humans briefly maintain mental representations of speech sounds conveying verbal information, and constantly scan these representations for comparison to incoming information. We determined the spatio-temporal dynamics of such short-term maintenance and subsequent scanning of verbal information, by intracranially measuring high-gamma activity at 70-110Hz during a working memory task.
  
  
  
  Patients listened to a stimulus set of two or four spoken letters and were instructed to remember those letters over a two-second interval, following which they were asked to determine if a subsequent target letter had been presented earlier in that trial's stimulus set.
  
  
  
  Auditory presentation of letter stimuli sequentially elicited high-gamma augmentation bilaterally in the superior-temporal and pre-central gyri. During the two-second maintenance period, high-gamma activity was augmented in the left pre-central gyrus, and this effect was larger during the maintenance of stimulus sets consisting of four compared to two letters. During the scanning period following target presentation, high-gamma augmentation involved the left inferior-frontal and supra-marginal gyri.
  
  
  
  Short-term maintenance of verbal information is, at least in part, supported by the left pre-central gyrus, whereas scanning by the left inferior-frontal and supra-marginal gyri.
  
  
  
  The cortical structures involved in short-term maintenance and scanning of speech stimuli were segregated with an excellent temporal resolution.
authors.affiliation: Department of Pediatrics, Children's Hospital of Michigan, Wayne State University, Detroit Medical Center, Detroit, MI 48201, USA; Postdoctoral Fellowship for Research Abroad, Japan Society for the Promotion of Science (JSPS), Chiyoda-ku, Tokyo 1020083, Japan.
authors.forename: Toshimune
authors.initials: T
authors.lastname: Kambara
authors.affiliation: Department of Neurological Surgery, Oregon Health and Science University, Portland, OR 97239, USA.
authors.forename: Erik C
authors.initials: EC
authors.lastname: Brown
authors.affiliation: Department of Pediatrics, Children's Hospital of Michigan, Wayne State University, Detroit Medical Center, Detroit, MI 48201, USA; Department of Neurology, Children's Hospital of Michigan, Wayne State University, Detroit Medical Center, Detroit, MI 48201, USA.
authors.forename: Jeong-Won
authors.initials: JW
authors.lastname: Jeong
authors.affiliation: Institute of Gerontology, Wayne State University, Detroit, MI 48202, USA; Department of Psychology, Wayne State University, Detroit, MI 48202, USA.
authors.forename: Noa
authors.initials: N
authors.lastname: Ofen
authors.affiliation: Department of Pediatrics, Children's Hospital of Michigan, Wayne State University, Detroit Medical Center, Detroit, MI 48201, USA.
authors.forename: Yasuo
authors.initials: Y
authors.lastname: Nakai
authors.affiliation: Department of Pediatrics, Children's Hospital of Michigan, Wayne State University, Detroit Medical Center, Detroit, MI 48201, USA; Department of Neurology, Children's Hospital of Michigan, Wayne State University, Detroit Medical Center, Detroit, MI 48201, USA. Electronic address: eishi@pet.wayne.edu.
authors.forename: Eishi
authors.initials: E
authors.lastname: Asano
mesh_terms: D000293:Adolescent; D000328:Adult; D002648:Child; D000069280:Electrocorticography; D004828:Epilepsies, Partial / Q000503:physiopathology; D005260:Female; D065818:Gamma Rhythm; D006801:Humans; D008297:Male; D008570:Memory, Short-Term; D013067:Speech Perception; D014705:Verbal Behavior
keywords: 4D brain mapping; High-frequency oscillations (HFOs); Intracranial electrocorticography (ECoG) recording; Pediatric epilepsy surgery; Sternberg paradigm; Subdural electroencephalography (EEG)