Structural variation in the temporal lobe predicts learning and retention of non-native speech sounds

Abstract

ABSTRACT Studies of non-native speech sound learning report considerable individual variability in learning new sounds and retaining them in memory. The current study tested whether individual variation in brain structure (measured using MRI) accounts for differences in learning or retention of non-native speech sounds. Fifty-seven participants were tested on identification and discrimination of difficult non-native speech sounds in the evening before training, after training, and tested again the next morning. Surface area and volume of the left superior temporal gyrus positively predicted discrimination learning, whereas surface area of the left transverse temporal gyrus negatively predicted overnight improvement of identification. Hippocampal volume as well as gyrification of bilateral transverse temporal gyri positively predicted overnight improvement of discrimination. Findings suggest that individual differences in non-native speech sound learning can be traced to differences in brain structure supporting perception, while differences in retention are linked to the structure of hippocampal regions important for memory consolidation.