|Angry face of a female intending to seriously |
hurt or scare someone/thing. Blue points represent
fixations from a person looking at the picture
|Fig. 1. Visual processing of 'What' along the inferotemporal|
(IT) cortex of monkey (and human). IT cortex is largely
dividedinto the caudal portion (TEO) and the more
anterior portion (TE) (source)
|Fig, 2. Inferior view of the brain (e.g. taking the brain and flipping it|
up-side down). Bilateral FFA activation along the
ventral occtipito-temporal cortex (source)
Skipping along to the good stuff: connectivity....
You can see how one can get bogged down into this one particular area, namely the FFA, and forget the 'big' picture. Obviously, when we look at a face, there are massive amounts of connections being activated all throughout the brain. For me, I tend to disagree with a lot of areas that are said to be 'modular', as I think processing rarely, if ever, takes place in one locale. You have so many different dimensions, not only in visual appearance, that need to be processed.
As stated above, faces convey a wealth of information: gender, trustworthiness, beauty and/or attractiveness, intentions, emotions, etc. If you just look over the figure below, you can start to appreciate the highly connected areas involved with the simplest feat of processing a face. Imagine what your brain is doing when you see a child trowing a snow ball, a dragon flying while breathing fire on TV.... countless more areas are activated.
Monkey Face Patches & Emotion
What one must keep in mind, however, is that these areas mentioned are feedforward and feedback systems.
Red = face-selective regions;
Yellow = face-responsive regions.
Before we begin, briefly, I'll describe face processing in the monkey. There appears to be a posterior 'face patch' and an anterior 'face patch' located within IT cortex. Face patches have also been found in the frontal cortex, but as to whether they're truly face-selective is not currently known.In the figure to the left, regions of the monkey IT cortex appear to be homologous to human face areas for face responsiveness (e.g. FFA). The one believed to be closely related to the human FFA is posterior face patch in the temporal cortex, located in area TEO. As you can see, an anterior face patch is detected in monkey (in area TE), and this has recently been reported in the human (see Rajimehr, et al. 2009). Indeed, there is a difference between face-selective and face-responsive areas in monkey, as alluded to earlier. Face-selective areas are those that respond to only faces, as compared to objects, scenes, body parts (areas in red in picture). Face-responsive areas are those that respond to faces but also may respond to the other said categories (yellow in picture).
|These scans show the emotional modulation of IT cortex, not|
the face processing regions. This modulation
is independent of face selectivity (those regions circled in black)
These possibilities are currently being investigated. This is only one example of how feedback projections play in to not only face processing but further visual processing and in other modalities.
I'll leave you with a video of a lady with prosopagnosia, which is the inability to recognize faces ('face blindness'), while having otherwise normal object processing and recognition. The question that, again, remains is: Is this a problem in processing faces or a facial recognition problem, in the broadest sense? Nonetheless, here you are...
Becoming a 'Greeble' expert: exploring mechanisms for face recognition (source)
FFA: a flexible fusiform area for subordinate-level visual processing automatized by expertise (source)
Expertise for cars and birds recruits brain areas involved in face recognition (source)
Domain specificity in face perception (source)
What is special about face recogintion? Nineteen experiments on a person with visual object agnosia and dyslexia but normal face recognition (source)
What is "special" about face perception? (source)
Can generic expertise explain special processing for faces? (source)