Enhanced functional networks in absolute pitch

Abstract

Functional networks in the human brain give rise to complex cognitive and perceptual abilities. While the decrease of functional connectivity is linked to neurological and psychiatric disorders, less is known about the consequences of increased functional connectivity. One population that has exceptionally enhanced perceptual abilities is people with absolute pitch (AP) - an ability to categorize tones into pitch classes without reference. AP has been linked to exceptional talent as well as to psychiatric and neurological conditions. Here we show that AP possessors have increased functional activation during music listening, as well as increased degrees, clustering, and local efficiency of functional correlations, with the difference being highest around the left superior temporal gyrus. Our results provide the first evidence that increased functional connectivity in a small-world brain network is related to exceptional perceptual abilities in a healthy population.

Fig. 1

Behavioral results from arousal ratings for music. Each point represents mean ratings for AP group (X-axis) and the non-AP group (Y-axis) for a single trial. Error bars represent between-subject standard errors. Behavioral responses from the two groups are highly correlated.

Fig. 2

Second-level activations for all music vs. rest for the AP group (red) and the non-AP group (blue), and the overlap between the groups (purple). Results are at the p<0.05 (FWE-corrected) level, showing activations in the bilateral Heschl's gyri, superior temporal gyri and middle temporal gyri, with a wider spread of activations in the AP group, especially in the left superior temporal gyrus. (For interpretation of the references to color in this figure legend, the reader is referred to the web of this article.)

Fig. 3

Interactions between group (AP vs. non-AP) and task (music vs. rest), showing increased activations in the AP group during music listening. Results are significant at the p<0.05 (cluster-corrected) level. A) Activations in the left superior temporal gyrus (x=–48, y=–24, z=–9) and postcentral gyrus (x=–48, y=–24, z=50). B) Additional activations in the hippocampus and amygdala (x=–31, y=–8, z=–21). C) Additional activations in the ventral tegmental area/substantia nigra of the midbrain (x=–13, y=–24, z=–12).

Fig. 4

Network analysis pipeline for functional connectivity. Top: mean time-series data were obtained from fMRI scans of both AP and non-AP groups. Middle: Pairwise correlation matrices were obtained between every pair of regions from the modified AAL atlas. Bottom: Network statistics were calculated and visualized in brain space. Axial views of graphs obtained from both subject groups are shown here, with size of each node corresponding to degrees and color of each node corresponding to clustering coefficient.

Fig. 5

Small-world network statistics for the whole brain comparing AP and non-AP groups in degree, strength, clustering, and local efficiency for networks thresholded at correlation strengths of r=0.05 through 0.55.

Fig. 6

Functional networks from correlation matrices in AP and non-AP data overlaid on a T1 template brain. Each node is a single region of interest. Color of each node corresponds to clustering coefficients. Size of each node corresponds to degrees. Note that nodes are generally larger in the AP than in the non-AP brain, suggesting that degrees of connectivity are higher in the AP group. Furthermore, the nodes in superior temporal regions (indicated by black arrows) are brighter red in the AP group, representing increased clustering in the superior temporal lobe in the AP brain. (For interpretation of the references to color in this figure legend, the reader is referred to the web of this article.)

Fig. 7

Small-world network statistics of the whole brain comparing AP1, AP2, and non-AP groups as defined post-hoc using the pitch labeling test.

Fig. 8

Small-world networks statistics comparing AP and non-AP groups for correlation thresholds of 0.05 to 0.55 similar to Fig. 5, but separately for Rest condition trials (a) and Music condition trials (b).