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  1. 1. BentonMiranda Srnka
  2. 2.  Basic strategies underlying facial perception? How are faces encoded? Does spatial recognition have a special status?... Determine this by asking is impairment of this capacity an autonomous deficit or one expression of a pervasive visuoperceptive disability
  3. 3.  Failure to recognize or identify a visual stimulus w/ in the context of apparently adequate visuosensory capacity FACIAL AGNOSIA (prosopagnosia)- incapacity of patient to identify familiar faces on the basis of visual perception Caused by bilateral disease (lesion to inferior occipital area of right hemisphere) Simplest interpretation = impairment to analysis and synthesis of complex visual stimulus configurations that most clearly manifests itself in facial recognition because its such a formidable discriminative task (visuoperceptive disability)
  4. 4.  Some prosopagnosia patients can identify unfamiliar faces quite well Patients with serve visuoanalytic and visuosynthetic capacity generally do not show facial agnosia There is something special about facial recognition and its disturbances
  5. 5.  Incapacity to perceive individuality within a single class of objects Material specific defect in memory (defect in integrating current facial percepts with past experience of them) *no single explanation is supported with impressive empirical evidence b/c facial agnosia is too rare to accumulate ample data
  6. 6.  Series of different facial recognition tasks given to brain-disease patients to determine relationship of performance level w/ locus of lesion. A.) matching of identical front-view photographs of a face B.) Matching of a front-view w/ views from different angles C.) Matching of front-view photographs under different lighting conditions
  7. 7.  Right anterior Right posterior Left anterior (nonaphasic) Left posterior (nonaphasic) Left anterior (aphasic w/o comprehension defect) Left posterior (aphasic w/o comprehension defect) Left anterior (aphasic w/ comprehension defect) Left posterior (aphasic w/ comprehension defect)
  8. 8.  Patients w/ posterior right hemisphere lesions & visual field defects performed at a lower level than the rest of the groups Among patients w/ posterior right hemi. Lesions, those w/ visual field defects showed higher frequency of failing facial recognition performance Only a minimal difference for patients w/ left hemi. Posterior lesions Injury to central visual pathways in not a determinant in failing performance on facial recognition in patients with posterior lesions Right hemisphere plays a particularly important role in mediating the discrimination of unfamiliar faces.
  9. 9.  Group of patients with left hemisphere disease that show noticeably high frequency of failure in facial recognition (aphasic patients w/ defective aural lang. comprehension) Therefore, in addition to visuoperceptive mechanisms of the right hemisphere, mechanisms of the left hemi. are also involved in the discrimination of faces Left hemisphere = linguistic (verbal encoding of perceptions help out in facial recognition) ex: “long nose” “she’s pretty” “big ears”
  10. 10.  Assumption that detection of familiar and unfamiliar faces relies on the same capacities proved incorrect Disabilities in identifying familiar and unfamiliar faces are dissociative Prosopagnosia patients can identify unfamiliar faces but not familiar faces. Prosopagnosia = bilateral disease (product of occipito-temporal disease) Incapacity to ID unfamiliar faces = unilateral hemispheric disease Impairment of facial recognition comes in 2 forms… Prosopagnosia and defect in discriminating unfamiliar faces.