Brain potentials reflect residual face processing in a case of prosopagnosia

Abstract

Here, ERPs were employed to characterise the residual face processing of FE, a patient with extensive damage to the ventral temporal-occipital cortex and a dense prosopagnosia. A large N170 was present in FE and he performed well in tests of face structural processing. Covert recognition of the faces of personal acquaintances was demonstrated with P300 oddball experiments. The onset latency of the P300 effect was normal, indicating fast availability of covert memory. The scalp topography of this component in FE was different from that of the P3b, presenting a centro-frontal maximum. FE also presented larger skin conductance responses to familiar than to unfamiliar faces. The amplitudes of both the single-trial P300s and the SCRs triggered by familiar faces were positively correlated with the degree of person-familiarity that FE had for the poser. He performed at chance when asked to select between the face of a familiar person and that of an unfamiliar person on the basis of explicit recognition, whereas he selected more the previously known face if the forced choice was based on trustworthiness or a vague sense of familiarity. The results suggest that in FE, early face processing was relatively intact and covert recognition was fast. Neural structures involved in the processing of emotional or social cues possibly mediate the covert recognition present in FE.

Impaired face and body perception in developmental prosopagnosia

“…Although a relative absence of an increased N170 amplitude for faces as compared with objects may relate to face recognition problems (28)(29)(30), other cases of prosopagnosia have not shown this pattern (31,32). One explanation of this diverse pattern again observed here may be that the N170 is, in addition to the encoding of the whole face, related to the perception of facial features and may reflect the extent to which a featural strategy is adopted.…”

“…For some prosopagnosic cases, the N170 did not show the characteristic increased amplitude for faces as compared with objects (28-31), whereas for other cases an increase of the N170 for faces relative to objects was reported much as in normal subjects (31,32). This lack of consistency may be related to the heterogeneous nature of developmental disorders like prosopagnosia and is in line with mixed results obtained in behavioral (9,20,33) and functional MRI studies (34)(35)(36), mostly of single patients.…”

Covert face recognition without the fusiform-temporal pathways

“…This patient suffered extensive bilateral damage to his ventral occipito-temporal cortex (Lopera and Ardila, 1992), which produced a severe deficit in face identification. He also exhibited robust emotionally-based covert recognition of the same previously-known faces that he was unable to recognize consciously (Bobes et al, 2004). The study of FE suggested that a previously ignored pathway (and not the fusiform-temporal route) was responsible for his covert face processing.…”

“…Another expression of covert recognition is an increased emotional arousal to NeuroImage 57 (2011NeuroImage 57 ( ) 1162NeuroImage 57 ( -1176 faces of celebrities or acquaintances relative to unfamiliar faces, as indexed by larger skin conductance responses -SCRs - (Bauer, 1984;Bobes et al, 2004;Tranel and Damasio, 1985) and P300 brain waves (Bobes et al, 2004;Renault et al, 1989). Also, implicit preference for some faces, which indicates access to memories for their emotional valence, has been found in AP (Bobes et al, 2004;Tranel and Damasio, 1993). Note that activation of emotional memories by known faces is conceptually distinct from the processing of facial expressions.…”

The P300 is sensitive to concealed face recognition

“…2 Especially the latter has been found to be sensitive to the recognition of familiar faces, whether famous (Henson et al, 2003), learned during a study phase (Joyce and Kutas, 2005;Paller et al, 1999Paller et al, , 2000Paller et al, , 2003, or the participant's own face (Ninomiya et al, 1998). Moreover, a late positive ERP component in response to familiar faces has even been observed in prosopagnosia patients, regardless of their incapability of familiar face recognition (Bobes et al, 2004;Renault et al, 1989). However, paradigms used in the studies cited above vary greatly and in each case deviate from a typical P300 based CIT.…”