"When Music Speaks": Auditory Cortex Morphology as a Neuroanatomical Marker of Language Aptitude and Musicality

Abstract

Recent research has shown that the morphology of certain brain regions may indeed correlate with a number of cognitive skills such as musicality or language ability. The main aim of the present study was to explore the extent to which foreign language aptitude, in particular phonetic coding ability, is influenced by the morphology of Heschl's gyrus (HG; auditory cortex), working memory capacity, and musical ability. In this study, the auditory cortices of German-speaking individuals (N = 30; 13 males/17 females; aged 20-40 years) with high and low scores in a number of language aptitude tests were compared. The subjects' language aptitude was measured by three different tests, namely a Hindi speech imitation task (phonetic coding ability), an English pronunciation assessment, and the Modern Language Aptitude Test (MLAT). Furthermore, working memory capacity and musical ability were assessed to reveal their relationship with foreign language aptitude. On the behavioral level, significant correlations were found between phonetic coding ability, English pronunciation skills, musical experience, and language aptitude as measured by the MLAT. Parts of all three tests measuring language aptitude correlated positively and significantly with each other, supporting their validity for measuring components of language aptitude. Remarkably, the number of instruments played by subjects showed significant correlations with all language aptitude measures and musicality, whereas, the number of foreign languages did not show any correlations. With regard to the neuroanatomy of auditory cortex, adults with very high scores in the Hindi testing and the musicality test (AMMA) demonstrated a clear predominance of complete posterior HG duplications in the right hemisphere. This may reignite the discussion of the importance of the right hemisphere for language processing, especially when linked or common resources are involved, such as the inter-dependency between phonetic and musical aptitude.

Keywords: Heschl’s gyrus; auditory cortex morphology; language aptitude; musicality; neuroanatomical correlates; working memory.

FIGURE 1

Examples of 3D reconstructions of the three types of HG distinguished in this paper. Examples from the right hemisphere are given (from left to right): (1) single gyrus (SG), (2) common stem duplication (CSD), and (3) complete posterior duplication (CPD). (aSTG anterior superior temporal gyrus; PT planum temporale).

FIGURE 2

Individual factor scores (positive/negative: above/below average; M = 0, SD = 1) on each of the three identified PCA components compared for the three types of HG in the right hemisphere. Error bars: SEM (standard error of the mean); Single, single gyrus; CSD, common stem duplication; CPD, complete posterior duplication.

FIGURE 3

Group-averaged auditory cortex (AC) surfaces of subjects with high Hindi (left) and low Hindi scores (right). The predominance of posterior duplications in the right hemisphere (red) of subjects with high Hindi Score is clearly visible from the averaged surface. Subjects with low Hindi score show in the averaged map a lateral HG duplication, which is also visible in the averaged left hemisphere of subjects with high Hindi score.

FIGURE 4

Individual AC surfaces of all 30 subjects, subdivided in subjects with high (top) and low (bottom) Hindi scores. Subjects of the first group show a clear predominance of CPDs in the right hemisphere. However, trends in the left hemisphere could not be statistically verified. Overall, the incidence of duplications was about twice larger in the right hemisphere (red) as compared to the left hemisphere (blue).

FIGURE 5

Results of the one-way ANOVA comparing mean total Hindi score (overall range: 0–10) with the three types of HG in the right hemisphere (for a visual presentation, see Figure 1). Error bars: SEM (standard error of the mean). Individuals with CPD scored significantly higher in the Hindi testing in comparison to subjects with SG or CSD in the right hemisphere.

FIGURE 6

Results of the one-way ANOVA comparing mean total AMMA score with the three defined types of HG in the right hemisphere (for a visual presentation, see Figure 1). Error bars: SEM (standard error of the mean). Individuals with CPD had significantly higher scores in the AMMA test in comparison to subjects with SG or CSD in the right hemisphere.