Intensity-dependent activation of the primary auditory cortex in functional magnetic resonance imaging

Katie J. Lasota, John L. Ulmer, Jill B. Firszt, Bharat B. Biswal, David L. Daniels, Robert W. Prost

Research output: Contribution to journalArticlepeer-review

23 Scopus citations

Abstract

Purpose: The purpose of this study was to investigate the activation patterns of the primary auditory cortex in response to varying intensities of pure tone stimuli. Method: A 1,000-Hz pure tone stimulus was delivered monaurally to the right ear of 12 normal-hearing right-handed volunteers in 20-second on-off cycles. Stimuli were applied at 20 and 50 dB hearing level (HL) above threshold in 12 subjects and at 0, 20, 40, and 50 dB HL above threshold in 6 subjects. Functional magnetic resonance imaging (fMRI) data were obtained using a 1.5-T scanner and echoplanar imaging. Activated pixels were identified in the transverse temporal gyrus (TTG) of both hemispheres in response to pure tone stimuli at each intensity level using cross-correlation analysis (0.6; P < 0.0001). Results: Of the 24 right and left TTGs imaged (n = 12), activation to pure tone stimuli at 20 and 50 dB HL above threshold was seen in 46% and 79% of TTGs, respectively, with bilateral hemispheric activation in 27% and 64% of subjects, respectively. The mean numbers of activated voxels were 4. 0 and 13.0, respectively. Of the 12 right and left TTGs imaged at 0, 20, 40, and 50 dB HL above threshold, activation was seen in 33%, 42%, 58%, and 75% of TTGs, respectively. The mean numbers of activated voxels were 5.8, 3.2, 9.8, and 15.3, respectively. There was a nonsignificant trend toward contralateral (left) dominant TTG activation with increased tone intensity. Conclusion: Our results show an increased likelihood of TTG activation, increased TTG activation volume, and increased bilateral hemisphere TTG activation with increasing pure tone intensity. Our results suggest that the primary auditory cortex reflects or is directly involved in the central processing of sound intensity and that varying the intensity of even simple stimuli can alter the patterns of fMRI activation in auditory cortex.

Original languageEnglish (US)
Pages (from-to)213-218
Number of pages6
JournalJournal of Computer Assisted Tomography
Volume27
Issue number2
DOIs
StatePublished - Mar 2003
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Radiology Nuclear Medicine and imaging

Keywords

  • Auditory cortex
  • Functional magnetic resonance imaging
  • Pure tone stimuli
  • Sound intensity

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