Illustration of a Mooney face based on the manipulation proposed by Craig M Mooney—note: this specific illustration is not part of the original set of Mooney faces and was not used in the present experiment.

<p>On the left (a), an original photograph of a bust of Gaius Julius Caesar (bust is situated in Naples National Archaeological Museum; the photo stems from the Wikimedia Commons), on the right (b), a two-tone (“Mooney”) image of it with high contrasts, which was previously smoothed by a Gaussian filter.</p

Correctness data split by age classes for the age (red, unfilled dots) and the gender (black, filled dots) decision task, respectively.

<p>Error cars indicate 95%-confidence intervals. Additional information given by “<i>n.s.</i>” show non-significant pairwise comparisons, e.g. the pairwise comparison between age group “01-05” was not significant when compared with “06-10” and “81-88”, meaning all <i>other</i> comparisons were significant at the Bonferroni adjusted level (see body text for more information on the alpha-error correction).</p

The 170ms Response to Faces as Measured by MEG (M170) Is Consistently Altered in Congenital Prosopagnosia

<div><p>Modularity of face processing is still a controversial issue. Congenital prosopagnosia (cPA), a selective and lifelong impairment in familiar face recognition without evidence of an acquired cerebral lesion, offers a unique opportunity to support this fundamental hypothesis. However, in spite of the pronounced behavioural impairment, identification of a functionally relevant neural alteration in congenital prosopagnosia by electrophysiogical methods has not been achieved so far. Here we show that persons with congenital prosopagnosia can be distinguished as a group from unimpaired persons using magnetoencephalography. Early face-selective MEG-responses in the range of 140 to 200ms (the M170) showed prolonged latency and decreased amplitude whereas responses to another category (houses) were indistinguishable between subjects with congenital prosopagnosia and unimpaired controls. Latency and amplitude of face-selective EEG responses (the N170) which were simultaneously recorded were statistically indistinguishable between subjects with cPA and healthy controls which resolves heterogeneous and partly conflicting results from existing studies. The complementary analysis of categorical differences (evoked activity to faces minus evoked activity to houses) revealed that the early part of the 170ms response to faces is altered in subjects with cPA. This finding can be adequately explained in a common framework of holistic and part-based face processing. Whereas a significant brain-behaviour correlation of face recognition performance and the size of the M170 amplitude is found in controls a corresponding correlation is not seen in subjects with cPA. This indicates functional relevance of the alteration found for the 170ms response to faces in cPA and pinpoints the impairment of face processing to early perceptual stages.</p></div

Stimuli and task for experiment 1 with two typical trials (face or house).

<p>The targets were inserted in the random sequence of faces and houses and persons responded differently to vertical or horizontal movement (illustrated by arrows).</p

EEG result.

<p>In contrast to MEG amplitudes and latencies of grand averaged curves (A) are statistically indistinguishable both for faces and for houses. (B) Representation of categorical differences (faces vs. houses) by box plots. (C) Categorical difference curves: faces minus houses (red: persons with cPA, black: controls, blue: categorical difference cPA minus categorical difference controls “double difference”). (D) Temporal evolution of interaction term (stimulus with group). The peak coincides with the peak of the “double–difference curve” (right hemisphere).</p

MEG result.

<p>Grand averaged curves (A) reveal significant differences of amplitude and latency (left) between persons with cPA and controls for faces and indistinguishable evoked responses for objects. The semitransparent confidence surfaces illustrate 1 SD. (B) Categorical differences (faces vs. houses) of M 170 peak amplitudes are represented by box plots representing the median, the lower and the upper quartile as well as the minimum and maximum values. (D) Categorical difference curves: faces minus houses (red: persons with cPA, black: controls, blue: categorical difference cPA minus categorical difference controls “double difference”). (E) Temporal evolution of interaction term (stimulus with group). The peak coincides with the peak of the “double–difference curve” (bilaterally).</p

Scatter plot relating performance in two tests of face processing (CMTF versus FFHRT).

<p>Performance of persons with cPA is illustrated by filled red circles; performance by unimpaired controls is illustrated by filled black squares.</p

Scatter plots: M170 amplitude versus dprime (d’).

<p>For colour coding cf. <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0137624#pone.0137624.g002" target="_blank">Fig 2</a>. <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0137624#pone.0137624.t002" target="_blank">Table 2</a> displays the statistics. Open symbols represent medians; error bars show IQR’s.</p

Famous face/house recognition test.

<p>Persons with cPA show significantly reduced accuracy and significantly extended reaction times for face recognition (red squares) compared to controls (black circles). For object recognition behaviour is indistinguishable between groups (cPA: blue; controls: green). Group medians are represented by open symbols. Error bars indicate the IQR.</p

Face recognition tests for controls and individuals with Prosopagnosia.

<p>Face recognition tests for controls and individuals with Prosopagnosia.</p