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FACE-SPECIFIC IMPAIRMENT IN
HOLISTIC PERCEPTION FOLLOWING
FOCAL LESION OF THE RIGHT
ANTERIOR TEMPORAL LOBE
Thomas Busigny, Goedele Van Belle,Boutheina Jemel, Anthony Hosein, SvenJoubert, Bruno Rossion
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INTRODUCTION
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Is LR's Visual recognition impairment limited to
faces?
Experiment 1: Face And Object Discrimination At
The Individual Level
Task
Intra-category discrimination
Inter-category
discrimination
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Result
Inter-category disc r iminat ion: Performance was at ceiling forall participants as well as categories.
Intra-category disc r iminat ion: LR performed in the normalrange for the five categories, including faces.
Regarding RTs, LR performed in the normal range for thefour nonface categories. However, he was significantlyslowed down for faces.
Conclusion: LR probably uses an abnormal strategy toprocess faces and his impairment does not seem to extendto other visual categories.
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Experiment 2: Discrimination Of Similar Items:
Cars And Faces
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Result
Car p ictures: LR performed in the normal range in accuracy
and correct RTs. For the most difficult level, in which thedissimilarity between the target and the distractor is only of20%, LR scored at chance level, as did four of the controls.
Face pic tures: Control participants' performance decreased
progressively as similarity between the target face and itsdistractor increased.
Although LR's overall performance did not differ significantlyfrom normal controls, he was significantly impaired inaccuracy for the three first levels of dissimilarity, the three
easiest ones, that is 100%, 80%, and 60%. His accuracy rateswere in the range of normal controls for the last two levels.He was slowed down overall, and significantly slowed downrelative to controls for the first four levels of dissimilarity, at100%, 80%, 60% and 40%. He performed in the normal rangeat the fifth level of dissimilarity the most difficult one.
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Conclusion: This finding directly contradicts the view that
prosopagnosia is due to a difficulty in processing items that
are visually similar.
If LR's prosopagnosia is not a problem at disambiguating
items that are visually similar, alternative explanations need
to be considered.
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Holistic Perception Of The Individual Face
Experiment 3: Benton face recognition test
(BFRT) upright and inverted
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Experiment 4: Delayed Matching Of Faces And
Cars Upright And Upside-down
Task: One full front and one 3/4 profile grayscale photographs of36 faces and 36 cars were used. The target picture was always afull-front picture, and the probe a 3/4 profile picture. Eachphotograph was presented in upright and inverted orientations.Participants had to choose which of two 3/4 profile probes was
the same identity as the full-front target presented earlier.
Result: Control participants had a large face inversion effect.For upright faces, LR performed lower than controls and he wassignificantly slowed down.
With inverted faces, his performance was within the normalrange for accuracy, but he was also slowed down relative tocontrols.
Importantly, there was no face inversion effect for LR.
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Pictures of cars: control participants did not show a
significant inversion effect in accuracy but they did so in
correct RTs.
LR did not show a significant car inversion effect in
accuracy.
Regarding RTs, he was no different from controls at any
orientation.
Index of the inversion effect was also computed.
The indexes indicated that LR was the only participant who
showed a tendency for a larger inversion index for cars than
faces.
In contrast, all normal participants had a larger inversioneffect for faces than for cars.
Conclusion: LR's acquired prosopagnosia seems to affect
primarily a process that is specific to upright faces.
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Result
Normal controls show both a whole-part advantage and a
part-whole disadvantage, while LR shows only the second
effect. That is, he does not perform better at discriminating a
part embedded in a whole face than when presented in
isolation. However, when he is presented with a face part atencoding, he recognizes the part better if it is isolated than
when it is embedded in a whole face.
Conclusion: It could be the consequence of residual face
holistic processing. This residual face holistic processing
could be insufficient to produce a positive effect (anadvantage of the face configuration), but could be sufficient
to produce a negative effect (the disadvantage of
supplementary facial information).
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Experiment 6. Composite Face Effect: Top
Composite (Alignment X identity)
Effect of al ignm ent: Misaligned trials are performed better than aligned
trials.
Effect of id ent i ty :
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Experiment 7: Gaze Contingent Individual
Face Discrimination