Aesthetic judgments, like most judgments, depend on context. Whether an object or image is seen in daily life or in an art gallery can significantly modulate the aesthetic value humans attach to it. We investigated the neural system supporting this modulation by presenting human subjects with artworks under different contexts whilst acquiring fMRI data. Using the same database of artworks, we randomly labelled images as being either sourced from a gallery or computer generated. Subjects' aesthetic ratings were significantly higher for stimuli viewed in the 'gallery' than 'computer' contexts. This contextual modulation correlated with activity in the medial orbitofrontal cortex and prefrontal cortex, whereas the context, independent of aesthetic value, correlated with bilateral activations of temporal pole and bilateral entorhinal cortex. This shows that prefrontal and orbitofrontal cortices recruited by aesthetic judgments are significantly biased by subjects' prior expectations about the likely hedonic value of stimuli according to their source.