Representation of the breast: According to the specific nerve architecture that underlies breast sensation, where the medial & lateral sides of one breast are asymmetrically represented in bilateral primary somatosensory cortex

Somatotopic mapping of the human breast using 7 T functional MRI. Jop Beugels et al. NeuroImage, September 18 2019, 116201. https://doi.org/10.1016/j.neuroimage.2019.116201

Highlights
•    Stimulation of the breast resulted in a robust response on the dorsal surface of S1.
•    Unilateral breast stimulation resulted in bilateral activity in S1.
•    Medial and lateral breast sides are asymmetrically represented in both hemispheres.
•    The nipple cluster is larger, more selective and more responsive than other parts.
•    No gender differences in the magnitude of cortical responses and representations.

Abstract: How are tactile sensations in the breast represented in the female and male brain? Using ultra high-field 7 T MRI in ten females and ten males, we demonstrate that the representation of tactile breast information shows a somatotopic organization, with cortical magnification of the nipple. Furthermore, we show that the core representation of the breast is organized according to the specific nerve architecture that underlies breast sensation, where the medial and lateral sides of one breast are asymmetrically represented in bilateral primary somatosensory cortex. Finally, gradual selectivity signatures allude to a somatotopic organization of the breast area with overlapping, but distinctive, cortical representations of breast segments. Our univariate and multivariate analyses consistently showed similar somatosensory breast representations in males and females. The findings can guide future research on neuroplastic reorganization of the breast area, across reproductive life stages, and after breast surgery.