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Acquired prosopagnosia is primarily defined as a defect in recognizing familiar faces. Nonetheless, for practical and methodological reasons, studies of such rare patients typically use pictures of unfamiliar faces. Here, we report an extensive investigation (17 behavioural tasks grouped in nine experiments) with a homogenous set of personally familiar faces in patient PS (Rossion et al., 2003. A network of occipito-temporal face-sensitive areas besides the right middle fusiform gyrus is necessary for normal face processing.), a well-documented case of acquired prosopagnosia with intact object recognition. PS’s recognition of the face pictures of 3–4-yearold children of her kindergarten is severely impaired—both in terms of accuracy and speed of recognition—and differs qualitatively from her colleagues’ performance. Relative to these typical individuals, PS relies more on external features, colour and local details of faces. She is also specifically impaired at processing the eye region in two-alternative face matching tasks, as well as in a familiar face recognition task performed both with pre-defined isolated parts and with randomly placed apertures revealing selective parts (“Bubbles”, >20.000 trials) of the personally familiar faces. These observations indicate that the same impairment observed previously with unfamiliar faces for PS and other cases of acquired prosopagnosia is associated with a deficient long-term representation of the eye region. Various manipulations that differentially affect the processing of the eye region suggest that this impairment is a consequence of the inability to represent the multiple parts of the eye region, and of the whole familiar face, as a single unit. This impairment in holistic processing is further evidenced here across different paradigms with composite faces, wholes and parts, and configurally distorted faces, mirroring and strengthening previous observations made with unfamiliar faces in PS and other cases of acquired prosopagnosia. Altogether, these observations suggest that prosopagnosia following brain damage affects unfamiliar and familiar face processing in a qualitatively similar way.

A B S T R A C T Purpose: The Wada test is still the gold standard procedure to predict language and memory deficits before temporal lobe epilepsy surgery. As amobarbital was no longer available, our aim was to validate propofol as an alternative. Method: We retrospectively studied 47 patients who underwent a bilateral intracarotid procedure, performed with amobarbital (18), or propofol (29), between 2000 and 2010 during the preoperative evaluation of temporal lobe epilepsy. Results: The number of patients experiencing an adverse event (mostly transient disturbance of consciousness or benign ocular symptoms) during both injections did not differ significantly between amobarbital and propofol. Hemispheric dominance was successfully determined in 96.5% patients with propofol vs. 94.4% with amobarbital for language, and in 72.4% under propofol vs. 77.7% under amobarbital for memory with no significant difference between groups. Conclusion: Propofol can be used for the Wada test with an efficacy and safety comparable to amobarbital.

Previous studies have shown that acquired prosopagnosia is characterized by impairment at holistic/configural processing. However, this view is essentially supported by studies performed with patients whose face recognition difficulties are part of a more general visual (integrative) agnosia. Here, we tested the patient PS, a case of acquired prosopagnosia whose face-specific recognition difficulties have been related to the inability to process individual faces holistically (absence of inversion, composite, and whole-part effects with faces). Here, we show that in contrast to this impairment, the patient presents with an entirely normal response profile in a Navon hierarchical letter task: she was as fast as normal controls, faster to identify global than local letters, and her sensitivity to global interference during identification of local letters was at least as large as normal observers. These observations indicate that holistic processing as measured with global/local interference in the Navon paradigm is functionally distinct from the ability to perceive an individual face holistically.

How a visual stimulus is initially categorized as a face in a network of human brain areas remains largely unclear. Hierarchical neuro-computational models of face perception assume that the visual stimulus is first decomposed in local parts in lower order visual areas. These parts would then be combined into a global representation in higher order face-sensitive areas of the occipito-temporal cortex. Here we tested this view in fMRI with visual stimuli that are categorized as faces based on their global configuration rather than their local parts (2-tones Mooney figures and Arcimboldo’s facelike paintings). Compared to the same inverted visual stimuli that are not categorized as faces, these stimuli activated the right middle fusiform gyrus (Fusiform face area, FFA) and superior temporal sulcus (pSTS), with no significant activation in the posteriorly located inferior occipital gyrus (i.e., no occipital face area, OFA). This observation is strengthened by behavioral and neural evidence for normal face categorization of these stimuli in a brain-damaged prosopagnosic patient (PS) whose intact right middle fusiform gyrus and superior temporal sulcus are devoid of any potential face-sensitive inputs from the lesioned right inferior occipital cortex. Together, these observations indicate that face-preferential activation may emerge in higher order visual areas of the right hemisphere without any face-preferential inputs from lower order visual areas, supporting a non-hierarchical view of face perception in the visual cortex.

Prosopagnosia is classically defined as a disorder of visual recognition specific to faces, following brain damage. However, according to a long-standing alternative view, these patients would rather be generally impaired in recognizing objects belonging to visually homogenous categories, including faces. We tested this alternative hypothesis stringently with a well-documented brain-damaged prosopagnosic patient (PS) in three delayed forced-choice recognition experiments in which visual similarity between a target and its distractor was manipulated parametrically: novel 3D geometric shapes, morphed pictures of common objects, and morphed photographs of a highly homogenous familiar category (cars). In all experiments, PS showed normal performance and speed, and there was no evidence of a steeper increase of error rates and RTs with increasing levels of visual similarity, compared to controls. These data rule out an account of acquired prosopagnosia in terms of a more general impairment in recognizing objects from visually homogenous categories. An additional experiment with morphed faces confirmed that PS was specifically impaired at individual face recognition. However, in stark contrast to the alternative view of prosopagnosia, PS was relatively more impaired at the easiest levels of discrimination, i.e. when individual faces differ clearly in global shape rather than when faces were highly similar and had to be discriminated based on fine-grained details. Overall, these observations as well as a review of previous evidence, lead us to conclude that this alternative view of prosopagnosia does not hold. Rather, it seems that brain damage in adulthood may lead to selective recognition impairment for faces, perhaps the only category of visual stimuli for which holistic/configural perception is not only potentially at play, but is strictly necessary to individualize members of the category efficiently.

Normal observers process individual faces holistically, meaning that facial features are processed simultaneously over a face-wide perceptual span and that the face is represented as a single perceptual unit. Acquired prosopagnosia, an impairment of face recognition following brain damage is thought to be caused by a problem with holistic processing of faces (Sergent & Villlemure, 1989). However, previous studies have only demonstrated an impairment of interactive processing of features in patients who, in addition, present general visual integrative agnosia (e.g., Boutsen & Humphreys, 2002; Levine & Calvanio, 1989), so that direct evidence for a deficit in holistic face processing in prosopagnosia is lacking. In an experiment with a brain damaged case of prosopagnosia (PS, Rossion et al., 2003), we used two gaze-contingent techniques allowing manipulation of the amount of information that was simultaneously available. First, a gaze-contingent foveal mask, prevented the use of foveal, high resolution information, necessary for detailed investigation of the facial features, but allowed holistic processing based on lower resolution peripheral information. Second, a gaze-contingent foveal window covering all peripheral information, prevented the simultaneous use of several facial features, but allowed detailed investigation of each feature individually. In a face matching task, normal control participants showed increased errors and RTs with a foveal window in comparison to conditions with a foveal mask or with a full face. PS, on the contrary, was almost unimpaired by a foveal window relative to a full face, while she had major difficulties recognizing faces with a foveal mask. Moreover, the eye movement data confirmed the findings from previous studies, that for face recognition, PS mainly relies on the mouth region, while normal observers attend to the region just below the eyes. These data provide direct evidence for impairment of holistic face processing in acquired prosopagnosia.