It’s a good idea to break down the question into its different aspects and use these to organise your material – for example, you might want to keep discussion of whether there are separate types of mechanism for recognising objects and faces separate from the question of whether these involve different parts of the brain.
Make sure that you answer the question directly – don’t just regurgitate everything that was in the lectures and key readings. For example, since the question is about visual object agnosia and prosopagnosia, fMRI studies of neurologically normal people won’t be relevant unless you are using them as a direct comparison.
As well as various other matters, we expect that you will want to explain the criteria for visual object agnosia and prosopagnosia and mention briefly how these relate to other neuropsychological disorders, discuss the implications of cases HJA and DF, evaluate Farah’s (1991) hypothesis concerning the relation between different types of visual recognition impairment, and discuss the extent to which prosopagnosia can be considered a face-specific deficit.
Don’t forget too that there are congenital as well as acquired forms of prosopagnosia.
Evidence of appropriate additional reading is likely to be rewarded, especially for primary source material (journal papers).