Face-specific Impairment in Holistic Perception Following Focal Lesion

8/10/2019 Face-specific Impairment in Holistic Perception Following Focal Lesion

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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

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Face-specific Impairment in Holistic Perception Following Focal Lesion