prosopagnosia (impaired facial recognition / blindness)

Introduction

the ability to recognise faces is a critical component of social networking and for most people, they are excellent at recognising a wide range of faces
recognising someone sends them a signal that they are important to you
failure to recognise someone may cause social embarrassment, distress and can limit employment opportunities
impaired recognition may also result in false recognition making one think they have met that person before

up to 3% of the population have genetic or developmental impaired facial recognition (prosopagnosia)
- 1% of the population have a more severe form whilst 2% of the population have a milder form ¹⁾
- prosopagnosia can also affect individuals on the autism spectrum or with Asperger's syndrome
1 in 30,000 have acquired prosopagnosia - mainly due to brain trauma or stroke involving occipital or temporal lobes

genetic or developmental prosopagnosia
- never adequately develops the ability to recognize faces
- hereditary prosopagnosia (HPA) appears to be autosomal dominant
acquired prosopagnosia can be characterized into three main types:
- Apperceptive prosopagnosia
  - defined as the inability to even perceive and cognitively process the face.
  - they are unable to even perceive a face at all (but can perceive other objects), let alone recognize who the face belongs to
- Associative prosopagnosia
  - defined as inability to recognize or apply any meaning to the face, despite perceiving it
  - often recognize other cues, such as voice and clothing, to recognize the individual
- “mirror-image” prosopagnosia
  - presents with the patient not recognizing their own face in the mirror or photographs

visual information
- ⇒ the V1-2 visual cortex
  - ⇒ the V3-5 visual association cortex
  - a ventral and dorsal stream are necessary to further interpret “what” is seen and “where” it is seen, respectively
    - ⇒ facial recognition is processed in the inferior occipital lobe at the fusiform gyrus, where communication occurs with the anterior part of the temporal lobe to associate with memory and apply meaning to the face

lesions are usually in the bilateral inferior occipitotemporal lobes
unilateral cases are less common and are most often attributable to right-sided lesions
unilateral left temporo-occipital lesions result in object agnosia, but spare face recognition processes

famous face recognition tests
- Bielefelder Famous Faces Test (BFFT)
face matching tests
- these are best for evaluating associative prosopagnosia
- Benton Facial Recognition Test (BFRT)
- Cambridge Face Memory Test (CFMT)
self-report questionnaires
- 20-item Prosopagnosia Index (PI20) ²⁾

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