Wikipedia (source warning) has an image that shows the orbitofrontal cortex (green):
The volunteers underwent a brain scan using Magnetic Resonance Imaging (MRI). They also completed a questionnaire that asked them to rate themselves on items such as 'I make a warm personal connection with most people', or 'I like to please other people as much as I can'. The answers to the questionnaire provide an overall measure of emotional warmth and sociability called social reward dependence.
The researchers then analysed the relationship between social reward dependence and the concentration of grey matter (brain-cell containing tissue) in different brain regions. They found that the greater the concentration of tissue in the orbitofrontal cortex (the outer strip of the brain just above the eyes), and in the ventral striatum (a deep structure in the centre of the brain), the higher they tended to score on the social reward dependence measure. The research is published in the European Journal of Neuroscience. ....
Interestingly, the orbitofrontal cortex and ventral striatum have previously been shown to be important for the brain's processing of much simpler rewards like sweet tastes or sexual stimuli.
An image from NIH shows the ventral striatum below (purple):