Fractional Anisotropy is Higher in Heschl’s Gyrus Than in Superior Temporal Gyrus in Normal Subjects¹

Rationale and Objectives

The first Heschl’s gyrus (HG) is believed to receive the core projection of the acoustic radiation. We examined if it were possible to differentiate the subcortical white matter of the HG from the superior temporal gyrus (STG) using diffusion tensor (DT) imaging.

Materials and Methods

The study was approved and informed consent was obtained in accordance with the guidelines of our Institutional Review Board for human subject studies. We examined six healthy adult volunteers with DT images using 20 orientations and repeated 11 times. The fractional anisotropy (FA) and the apparent diffusion coefficient (ADC) were calculated.

Results

The mean FA of the subcortical white matter of the HG (0.37) was higher than that of the STG (0.27) on both sides (P < .01). There was no statistically significant difference when comparing left and right HG and STG (P > .05). There was no statistically significant difference in mean ADC of the HGs and STGs (0.75 × 10⁻³ mm²/sec, P > .05).

Conclusions

The FA in the subcortical white matter of the HG was higher than that of the STG in both hemispheres. These changes in DT imaging may be accounted for by the presence of the auditory radiations.

Key Words:  Auditory cortex , acoustic radiation , diffusion tensor imaging , fractional anisotropy , apparent diffusion coefficient