Does the fusiform face area in patients with Prosopagnosia (face blindness) show lower activity under an fMRI? I watched last night's episode of 60 minutes (and part 2) about Prosopagnosia (Face Blindness) and found it absolutely fascinating. They mentioned in the segment (Around 5:22 into the second part of the online video) that Nancy Kanwisher of MIT has studied the MRI scans of people without Prosopagnosia and found that the fusiform face area lit up on an MRI when an individual was shown an image of a face.

Nancy Kanwisher then goes on to state the following:


  I really did not expect to see a fusiform face area [on an MRI scan of a patient with Prosopagnosia]. [...] And we looked at the data and his face area was beautiful, it was textbook. [...] It tells us that the problem is not that this thing [(the fusiform face area)] does not exist, there it is!




The image shows an MRI scan of a patient who has Prosopagnosia, demonstrating that the patient does have a fusiform face area. However, it was unclear to me whether the fusiform face area of an individual suffering from Prosopagnosia is less active when presented with a face than that of an individual without Prosopagnosia.

What did Nancy Kanwisher find with regards to that? Does the fusiform face area in individuals with Prosopagnosia exist but remains dormant? Or is it just as active but for some other (probably unknown) reason simply fail to relay the proper information to the rest of the brain?
It is not widely thought that impaired function or destruction of the fusiform is sufficient to produce prosoganosia. It is currently widely held that face processing involves a network of regions in the occipital and temporal lobes (e.g., the occipital face area, posterior superior temporal sulus, anterior superior temporal sulus, anterior collateral sulcus). For example, Bruno Rossion reports a patient with prosopagnoisa who has widespread damage to bilateral occipital and temporal brain regions but with a spared right FFA. Moreover, work by Marlene Behrmann has shown that people with developmental prosopagnosia have disrupted connections between the posterior temporal lobes (ie near the FFA) and the anterior temporal lobes. This is significant because there is growing evidence that there may be face selective regions in the anterior temporal lobes and that they are more directly involved in face recognition. Moreover there is some evidence that this anterior temporal region modulates the activity in the FFA (Nestor, Plaut, Behrmann, 2011 PNAS). So it might very well be that the FFA does show decreased activity in a face recognition task, but this might be due to impaired feedback to this region. On this view, lower activity in FFA is the effect of prosopagnosia not the cause, so making comparisons on levels of activity within one region might not be as meaningful as you think.

References


Nestor, A., Plaut, D.C., &amp; Behrmann, M. (2011). Unraveling the distributed neural code of facial identity through spatiotemporal pattern analysis. Proceedings of the National Academy of Sciences, 108, 9998. LINK