When the brain remembers, but the patient doesn't: Converging fMRI and EEG evidence for covert recognition in a case of prosopagnosia

Stéphane R. Simon, Asaid Khateb, Alexandra Darque, François Lazeyras, Eugene Mayer, Alan J. Pegna

Research output: Contribution to journalArticlepeer-review

Abstract

The role of the occipito-temporal cortex in visual awareness remains an open question and with respect to faces in particular, it is unclear to what extent the fusiform face area (FFA) may be involved in conscious identification. An answer may be gleaned from prosopagnosia, a disorder in which familiar faces are no longer recognized. This impairment has sometimes been reported to be associated with implicit processing of facial identity, although the neural substrates responsible for unconscious processing remain unknown. In this study, we addressed these issues by investigating the functional magnetic resonance imaging (fMRI) and electroencephalography (EEG) responses to familiar and unfamiliar faces in a well-known prosopagnosic patient (P.S.). Our fMRI results show that faces known prior to the onset of prosopagnosia produce an increase in activation in the lateral fusiform gyrus encompassing the FFA, as well as the right middle frontal gyrus, when compared to unknown faces. This effect is not observed with photographs of celebrities dating after the onset of prosopagnosia. Furthermore, electrophysiological responses show that previously familiar faces differ from unfamiliar ones at around 550. msec. Since covert processing of familiarity is associated with activation in FFA, this structure does not appear to be sufficient to produce awareness of identity. Furthermore, the results support the view that FFA participates in face individuation.

Original languageEnglish
Pages (from-to)825-838
Number of pages14
JournalCortex
Volume47
Issue number7
DOIs
StatePublished - Jul 2011

Bibliographical note

Funding Information:
This research was supported by the Swiss National Science Foundation grants no. 320030-125196 and 325100-118362 , and the Center for Biomedical Imaging (CIBM) of Geneva and Lausanne.

Keywords

  • Awareness
  • Event-related potentials
  • FFA
  • Faces
  • Functional imaging

ASJC Scopus subject areas

  • Experimental and Cognitive Psychology
  • Neuropsychology and Physiological Psychology
  • Cognitive Neuroscience

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