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. 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. 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. 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. 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. 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. 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. 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. 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.
