Mapping mental calculation systems with electrocorticography

Keisuke Ueda, Erik C. Brown, Katsuaki Kojima, Csaba Juhász, Eishi Asano

Research output: Contribution to journalArticlepeer-review

6 Scopus citations


Objective: We investigated intracranially-recorded gamma activity during calculation tasks to better understand the cortical dynamics of calculation. Methods: We studied 11 patients with focal epilepsy (age range: 9-28. years) who underwent measurement of calculation- and naming-related gamma-augmentation during extraoperative electrocorticography (ECoG). The patients were instructed to overtly verbalize a one-word answer in response to auditorily-delivered calculation and naming questions. The assigned calculation tasks were addition and subtraction involving integers between 1 and 17. Results: Out of the 1001 analyzed cortical electrode sites, 63 showed gamma-augmentation at 50-120. Hz elicited by both tasks, 88 specifically during naming, and 7 specifically during calculation. Common gamma-augmentation mainly took place in the Rolandic regions. Calculation-specific gamma-augmentation, involving the period between the question-offset and response-onset, was noted in the middle-temporal, inferior-parietal, inferior post-central, middle-frontal, and premotor regions of the left hemisphere. Calculation-specific gamma-augmentation in the middle-temporal, inferior-parietal, and inferior post-central regions peaked around the question offset, while that in the frontal lobe peaked after the question offset and before the response onset. This study failed to detect a significant difference in calculation-specific gamma amplitude between easy trials and difficult ones requiring multi-digit operations. Conclusions: Auditorily-delivered stimuli can elicit calculation-specific gamma-augmentation in multiple regions of the left hemisphere including the parietal region. However, the additive diagnostic value of measurement of gamma-augmentation related to a simple calculation task appears modest. Significance: Further studies are warranted to determine the functional significance of calculation-specific gamma-augmentation in each site, and to establish the optimal protocol for mapping mental calculation.

Original languageEnglish
Pages (from-to)39-46
Number of pages8
JournalClinical Neurophysiology
Issue number1
StatePublished - Jan 1 2015


  • Angular gyrus
  • Auditory
  • Cognition
  • Event-related synchronization
  • Functional brain mapping
  • Intracranial ECoG recording
  • Language
  • Number
  • Numeral
  • Pediatric epilepsy surgery
  • Physiological high-frequency oscillations (HFOs)
  • Ripples
  • Spatio-temporal-dynamics
  • Speech
  • Subdural EEG
  • Time-frequency analysis


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