Faces with no identity (prosopagnosia)

prosopagnosiaAcquired prosopagnosia (or face blindness) is the name of that rare syndrome (generally presenting, but not only, after stroke) affecting individuals who cannot recognize no more familiar faces or learn to recognize new faces. For example, these patients cannot differentiate known from unknown faces. Without other face-related inputs (such as voice, body movements, gait) and identity related data (such as age, profession, age and so on), most known faces (the one of relatives or famous persons) remain unknown and unfamiliar. Prosopagnosia is the most well-known and studied deficit of face-related cognitive and affective syndrome as there are others of them. For example patients with hyperfamiliarity for faces, contrarily to what it happens with psopagnosia, believe that all the faces, even the unknown ones, are familiar. Face recognition is a multistep process. First, visual processing of elemental traits of the face generates a face percept (that percept that allows recognizing that a face is a face, it has eyes, ears so on, or it is a masculine or feminine face). Then this first perceptual analysis is confronted with memorized pieces of information of already previously known faces, pieces that are usually indicated as ‘face recognition units’, or FRUs. This matching activates person-identity nodes (PINs), name recognition units (NRUs) and semantic information units (SRUs) containing biographical information about the person. PINs, SRUs and NRUs can be accessed through non-facial cues, such as voice or gait. In ‘apperceptive prosopagnosia’ the defect is an inability to use the elementary visual percepts to form an holistic visual representation of a face. In ‘associative prosopagnosia’ the patient can perceive well facial features and he can adequately compare similar or different faces but he cannot use that information to pick up the correct identity. Prosopagnosia has been extensively studied and several adaptations of the basic cognitive models of the syndrome have been advanced and largely debated. However, a world made without face-identities, as it happens with prosopagnosic patients, should be an emotional experience that is difficult to understand for healthy people. Actually, the role of the emotional processing in face identity recognition has been less studied than cognitive processing and should deserve major interest in the neurosciences.

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