Perhaps you're referring to Naomi Eisenberger's work on the neural basis of social pain. Her seminal paper found that the neural correlates of distress from social rejection overlapped with those of physical pain, i.e., dorsal anterior cingulate cortex and anterior insula.
She's recently published a literature review on social pain in the brain (Eisenberger, 2015), summarizing her work and addressing its various controversies.
However, Woo et al. (2014) recently challenged the notion of overlapping neural bases for social and physical pain. They used fancy multivariate methods to analyze the shared vs. distinct neural representations of social vs. physical pain. They conclude:
These findings demonstrate that separate representations underlie pain and rejection despite common [shared] fMRI activity at the gross anatomical level. Rather than co-opting pain circuitry, rejection involves distinct affective representations in humans.