Right hemispheric dominance of auditory effects evoked by electrical cortical stimulation of Heschl's gyrus and planum temporale.

BACKGROUND

Hemispheric asymmetry is a fundamental feature of the human brain. Numerous studies on auditory functions have shown both structural and functional differences between the left and right auditory cortex in the superior temporal gyrus (STG). However, evidence for this asymmetry using direct electrical stimulation (DES) - a powerful method to causally inform about the localization of human brain function - is surprisingly weak.

OBJECTIVE/HYPOTHESIS: To provide a comprehensive report of auditory effects elicited by the stimulation of the left and right STG.

METHODS

We reported the probability of occurrence of auditory effects (number of auditory hallucinations or illusions out of the total number of stimulations) as a function of hemispheres and anatomical regions in a large sample of patients (n = 109).

RESULTS

We showed that the probability of eliciting positive auditory effects is maximal in and around the primary auditory cortex, with a right hemispheric dominance.

CONCLUSIONS

Our results show that the right auditory cortex has a specific structural and functional organization, as early as the primary auditory cortex, leading to a higher proportion of evoked auditory effects. Such early asymmetry in cortical hierarchy may represent a unique feature of the auditory cortex compared to other sensory cortices.