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From covert to overt recognition of faces in a prosopagnosic patient.

Prosopagnosia is an inability to recognize known persons as a result of a failure to access relevant memories through the inspection of their faces. The nature of this disturbance, and the fate of memories related to faces, were investigated in a long-standing prosopagnosic woman (P.V.). An examination of P.V.'s perceptual capacities indicated no major impairment at matching faces, including different views of the same faces, and multidimensional scaling analysis showed that she could achieve configurational representations of faces as do normal subjects. In spite of her inability to evoke memories of known persons from their faces, P.V. displayed clear evidence that she could use pertinent memories related to these faces in tasks that did not explicitly call for their evocation. This covert recognition of faces was observed in perceptual learning and cued-recognized faces, attempts were made at surmounting the blocked activation of pertinent memories. Some of these attempts were successful in inducing P.V. into experiencing a sense of familiarity with the faces and identifying them, and this was the first occurrence of overt face recognition by P.V. since the onset of her illness. These findings provide clarification of the nature of the prosopagnosic disturbance and new information about the processes by which faces are recognized. They suggest that (1) prosopagnosia may result from a breakdown at different levels of face-recognition processes, (2) prosopagnosia may occur in spite of normal configurational encoding of facial representations, (3) covert recognition of overtly unrecognized faces requires the integrity of perceptual processes, and (4) failure of overt face recognition reflects a disturbance in the normal interactions between pertinent memories and facial representations which thus remain meaningless.

Agnosia↗

Holistic and part-based face recognition in children with autism.

BACKGROUND: There is substantial evidence that children with autism are impaired in face recognition. Although many researchers have suggested that this impairment derives from a failure of holistic face processing and a tendency to represent and encode faces on a part-by-part basis, this hypothesis has not been tested directly. METHOD: Holistic face processing was assessed by comparing children's ability to recognize a face part (eyes, nose, or mouth) in the context of the whole face in which it was learned with their ability to recognize the same face part in isolation. RESULTS: In Study 1, as expected, typically developing 9-year-olds (n = 27) and 11-year-olds (n = 30) were significantly better at recognizing face parts presented in the whole than in the part test condition, and this effect was limited to upright faces and not found for inverted faces. Consistent with prior findings, typically developing children were most accurate when face recognition depended on the eyes. In Study 2, high-functioning children with autism (n = 22) evidenced a whole-test advantage for mouths only, and were markedly deficient when face recognition depended on the eyes. Their pattern of performance diverged from age- and IQ-matched comparison participants (n = 20), who performed similarly to the typically developing children in Study 1. CONCLUSIONS: These findings suggest that face recognition abnormalities in autism are not fully explained by an impairment of holistic face processing, and that there is an unusual significance accorded to the mouth region when children with autism process information from people's faces.

Autistic Disorder↗

Are preschoolers sensitive to configural information in faces?

Several researchers have proposed that developmental improvements in children's face recognition abilities might reflect an increasing reliance on configural information (i.e. spatial relations between features) in faces (Carey & Diamond, 1994; Mondloch, Le Grand & Maurer, 2002). We investigated 4- and 5-year-olds' use of configural information for upright and inverted faces using Tanaka and Sengco's (1997) configural change paradigm. Participants saw a photograph of a child's face (e.g. Luke). Memory for features (e.g. Luke's mouth) was then tested in a face with the same configuration as the study face (e.g. Luke's face), in a face with a novel spatial configuration (e.g. Luke's face with the eyes shifted further apart), and presented on their own (e.g. Luke's mouth alone). We found that preschoolers and adults recognized target features from upright faces better when tested in the context of a face with the same configuration as the study face, than when they were embedded in a face with a new spatial configuration or when they were presented in isolation. This effect was lost when faces were inverted. The results suggest that adult-like styles of face processing are present from 4 years of age.

Adult↗

Processing the trees and the forest during initial stages of face perception: electrophysiological evidence.

Although configural processing is considered a hallmark of normal face perception in humans, there is ample evidence that processing face components also contributes to face recognition and identification. Indeed, most contemporary models posit a dual-code view in which face identification relies on the analysis of individual face components as well as the spatial relations between them. We explored the interplay between processing face configurations and inner face components by recording the N170, an event-related potential component that manifests early detection of faces. In contrast to a robust N170 effect elicited by line-drawn schematic faces compared to line-drawn schematic objects, no N170 effect was found if a pair of small objects substituted for the eyes in schematic faces. However, if a pair of two miniaturized faces substituted for the eyes, the N170 effect was restored. Additional experiments ruled out an explanation on the basis of miniaturized faces attracting attention independent of their location in a face-like configuration and show that global and local face characteristics compete for processing resources when in conflict. The results are discussed as they relate to normal and abnormal face processing.

Adolescent↗

Spatial summation of face information.

Do all parts of the face contribute equally to face detection or are some parts more detectable than others? To evaluate this issue, we studied detection of the presence of normalized frontal-face images within aperture windows of varying extent. We performed a face summation study using two-alternative forced-choice psychophysics. The face stimuli were scaled to equal eye-to-chin distance, centered on the bridge of the nose, and windowed by fourth-power Gaussian envelopes of various sizes. The faces were intermixed with control stimuli consisting inverted faces to test for configuration effects, split-half inverted faces to perturb the symmetry, and phase-scrambled versions of the faces with equal Fourier energy. Face detectability improved rapidly at first, then at a progressively shallower rate for larger window sizes, in a similar fashion for the three face-based stimulus types. The spectrally equated noise stimuli were less detectable than the face stimuli for all except the smallest apertures. The results were fit with a model incorporating global face-specific and local nonspecific spatial integration mechanisms. Detection of the noise images was consistent with local detection mechanisms accessed through a wide-field attention mechanism. The data for face detection implied detection mechanisms that integrated linearly up to some small size, integrated more slowly up to an intermediate size, and failed to gain any improvement for information beyond some larger size. This performance supports the concept of a specialized face configuration mechanism operating at detection threshold, similar in extent among the observers.

Artifacts↗

N400-like potentials elicited by faces and knowledge inhibition.

Within the theoretical framework of reference, the brain errs in processing complex stimuli, such as faces. Thus, these stimuli not only activate accurate representations but also inaccurate representations corresponding to known persons who resemble the face stimulus, and hence knowledge about these known persons. Since more errors are made in processing unfamiliar than familiar stimuli, these inaccurate activations are assumed to be more frequent, and/or more intense, with unknown than with known faces. Moreover, top-down mechanisms favor representations of stimuli that are congruent with the context, and representations of known persons, even if inaccurate, receive an additional amount of activation in contexts wherein known faces are expected. Inaccurate representations have to be inhibited to achieve accurate recognition. Thus, more inhibition would be required for unknown than for known faces, and in contexts wherein known faces are expected. The aim of the present work is to study the hypothesis that the N400 component of the event-related potentials (ERPs) reflects the inhibition of knowledge, and to see whether this hypothesis accounts for the N400-like potential elicited by faces. To achieve that goal, ERPs to known and unknown faces were recorded while the richness in known faces of each experimental block, and thus the expectancy for known faces, was manipulated. Consistent with the hypothesis, the amplitudes of the N400-like components were greater in conditions where more inhibition was required, i.e. for unknown rather than for known faces, and in the context of the block rich in known faces. This context effect was larger for unknown than for faces, and in the context of the block rich in known faces. This context effect was larger for unknown than for known faces.

Adult↗

Inversion and configuration of faces.

If the mouth and eyes of a face are inverted, the altered construction appears grotesque when upright, but not when upside-down. Three studies of this "Thatcher illusion" employed faces that were grotesque when upright because: (a) their eyes and mouths had been inverted ("Thatcherized" faces), (b) their eyes and mouths had been moved (spatially distorted faces), or (c) they had grotesque posed expressions. Inversion reduced the apparent grotesqueness of both Thatcherized and spatially distorted faces, but not grotesque-expression faces. Moreover, Thatcherized and distorted faces, although not grotesque-expression faces, were judged as more similar to normal, smiling faces when face-pairs were inverted than when they were upright. Similarity ratings to inverted face-pairs were correlated with latencies of response to these pairs in a task that encouraged attention to components (e.g., mouths, eyes) rather than wholistic properties. Similarity ratings to upright face-pairs showed no such correlation, and this and other findings suggested that although similarity ratings to upright faces are based on wholistic information, similarity ratings to inverted faces are based largely on components. The Thatcher illusion reflects a disruption of encoding of wholistic information when faces are inverted.

Adult↗

Hyperfamiliarity for unknown faces after left lateral temporo-occipital venous infarction: a double dissociation with prosopagnosia.

Right hemisphere dominance in face processing is well established and unilateral right inferior temporo-occipital damage can result in prosopagnosia. Here, we describe a 21-year-old right-handed woman with acute impairment in face recognition that selectively concerned unfamiliar faces, following a focal left lateral temporo-occipital venous infarct. She was severely impaired in discerning that unknown people seen in everyday life were unfamiliar, although she had no difficulty recognizing familiar people. Thus, she had no prosopagnosia, but abnormal 'hyperfamiliarity' for unknown faces. Her difficulty was not accompanied by delusions or deficits in discrimination, identification or memory for faces. Standard neuropsychological testing showed that her recognition of familiar faces was entirely normal. By contrast, her sense of personally knowing faces was severely impaired when unknown faces evoked weak signals of familiarity based on spurious cues, to the extent that she would misattribute fame to faces that were unknown but to which she had been incidentally exposed on a prior occasion. Priming experiments also revealed that, unlike normal subjects, she made familiarity judgements without accessing semantic identity representations. Moreover, in face recognition tests, she generally showed bias in that she relied more on right-hemisphere strategies to identify global traits and less on left-hemisphere processes compared with healthy subjects. This case provides novel evidence for a differential contribution of the two hemispheres to face recognition. Hyperfamiliarity for unknown faces might arise from an imbalance between reciprocal hemispheric functions in face recognition, with relative hypoactivation of left hemisphere processes but hyperactivation of right-hemisphere processes for retrieving stored associations about people, linking seen faces to representations of affective and personal relevance. Hence, abnormal bias in attributing some personal meaning to unknown faces could be evoked by spurious signals of familiarity based on irrelevant affective associations in the right hemisphere.

Adult↗

Size and contrast have only small effects on the responses to faces of neurons in the cortex of the superior temporal sulcus of the monkey.

There is a population of neurons in the cortex in the middle and anterior part of the superior temporal sulcus (STS) of the monkey with responses which are selective for faces. To investigate whether the responses of these neurons show some of the perceptual properties of face recognition such as tolerance to changes in the size and contrast of the face, the effects of alteration of the size and contrast of an effective face stimulus on the responses of these neurons were analysed quantitatively in macaque monkeys. First, it was shown that the majority of these neurons had responses which were relatively invariant with respect to the size of the stimulus. The median size change tolerated with a response of greater than half the maximal response was 12 times. Second, it was found that for a few of these neurons, the size of the face did affect the neuronal response. For most of these neurons, it was found that when the size of the image and its distance were altered, the neuronal response was related to the retinal angle subtended by the image. But for four neurons the absolute size of the image determined the magnitude of the neuronal response, independently of the distance of the image. Thus these four neurons showed size constancy. It is suggested that these neurons would be useful as part of a face recognition system, because only objects in a certain absolute size range should normally be classified as faces. Third, the responses of the neurons were relatively invariant with respect to the contrast of the face. The mean contrast at which the neurons still responded with more than half the maximal response was 0.26. Fourth, the responses of the neurons were relatively invariant with respect to the sign of the contrast of the face, that is the neurons responded to negative as well as to positive images of faces. Fifth, the neurons typically responded to a face when the information in it had been reduced from 3D to a 2D representation in gray on a monitor, with a response which was on average 0.5 that to a real face. These results show that the responses of these neurons have some of the invariant properties with respect to size and contrast alteration shown by face perception, and show that their processing is at a level which would be useful in face recognition.(ABSTRACT TRUNCATED AT 400 WORDS)

Action Potentials↗

Effects of the menstrual cycle on looking preferences for faces in female rhesus monkeys.

Fluctuations of ovarian hormones across the menstrual cycle influence a variety of social and cognitive behaviors in primates. For example, female rhesus monkeys exhibit heightened interest for males and increased agonistic interactions with other females during periods of high estrogen levels. In the present study, we hypothesized that females' preference for males during periods of high estrogen levels is also expressed at the level of face perception. We tested four intact females on two face-tasks involving neutral portraits of male and female rhesus monkeys, chimpanzees and humans. In the visual preference task (VP), monkeys had to touch a button to view a face image. The image remained on the screen as long as the button was touched, and the duration of pressing was taken as an index of the monkey's looking time for the face stimulus. In the Face-Delayed Recognition Span Test (Face-DRST), monkeys were rewarded for touching the new face in an increasing number of serially presented faces. Monkeys were tested 5 days a week across one menstrual cycle. Blood was collected every other day for analysis of estradiol and progesterone. Two of the four females were cycling at the time of testing. We did not find an influence of the cycle on Face-DRST, likely due to a floor effect. In the VP however, the two cycling individuals looked longer at conspecific male faces than female faces during the peri-ovulatory period of the cycle. Such effects were absent for human and chimpanzee faces and for the two noncycling subjects. These data suggest that ovarian hormones may influence females' preferences for specific faces, with heightened preference for male faces during the peri-ovulatory period of the cycle. Heightened interest for stimuli of significant reproductive relevance during periods of high conception risk may help guide social and sexual behavior in the rhesus monkey.

Animals↗

Cognitive modelling of face processing: evidence from Alzheimer patients.

This is a prospective neuropsychological study on face processing in Alzheimer's disease (AD). The aim was to assess the prevalence and the nature of face processing disorders in AD, and at investigating possible inter-test dissociations within the framework of currently used face processing models. A standardized four-test battery of unknown face discrimination and familiar face recognition was given to 30 mildly deteriorated patients with AD. Half of the patients performed below the cut-off in at least one of the tests. Deficits in familiar face recognition tests were more frequently observed than deficits in unknown face discrimination tests. There was no correlation between impairment of face processing and overall cognitive impairment or visual disorders. A multiple single case approach allowed us to elicit statistically warranted double dissociations between tasks assessing unknown face discrimination and tasks assessing familiar face recognition. Moreover, the ability to decide whether or not a stimulus is a face or a non-face has proven to be a non-mandatory step to further process the face stimuli. All together, these findings support the hypothesis that distinct pathways are involved in the processing of unknown and familiar faces, as posited by Bruce and Young [Br. J. Psychol. 77, 305-327, 1986].

Aged↗

Distinct representations for facial identity and changeable aspects of faces in the human temporal lobe.

The neural system underlying face perception must represent the unchanging features of a face that specify identity, as well as the changeable aspects of a face that facilitate social communication. However, the way information about faces is represented in the brain remains controversial. In this study, we used fMR adaptation (the reduction in fMRI activity that follows the repeated presentation of identical images) to ask how different face- and object-selective regions of visual cortex contribute to specific aspects of face perception. We report that activity in the face-selective region of the fusiform gyrus (FG) was reduced following repeated presentations of the same face. Adaptation in this area was not sensitive to changes in image size, but was sensitive to changes in viewpoint. In contrast, face-selective regions in the superior temporal lobe failed to adapt to identical presentations of the same face, but showed an increased response when the same face was shown from different viewpoints and with different expressions. These results reveal a largely size-invariant neural representation in the inferior temporal lobe that could be involved in the recognition of facial identity, and a separate face-selective region in the superior temporal lobe that could be used to detect changeable aspects of faces. The absence of fMR-adaptation in object-selective regions of visual cortex challenges the idea that a more distributed network of areas is used to represent information about faces.

Adaptation, Psychological↗

Size-invariant but viewpoint-dependent representation of faces.

The present study investigated the role of size and view on face discrimination, using a novel set of synthetic face stimuli. Face discrimination thresholds were measured using a 2AFC match-to-sample paradigm, where faces were discriminated from a mean face. In Experiment 1, which assessed the effect of size alone, subjects had to match faces that differed in size up to four-fold. In Experiment 2 where only viewpoint was manipulated, a target face was presented at one of four different views (0 degree front, 6.7 degrees, 13.3 degrees, and 20 degrees side) and subsequent matches appeared either at the same or different view. Experiment 3 investigated how face view interacts with size changes, and subjects matched faces differing both in size and view. The results were as follows: (1) size changes up to four-fold had no effect on face discrimination; (2) threshold for matching different face views increased with angular difference from frontal view; (3) size differences across different views had no effect on face discrimination. Additionally, the present study found a perceptual boundary between 6.7 degrees and 13.3 degrees side views, grouping 0 degrees front and 6.7 degrees side views together and 13.3 degrees and 20 degrees side views together. This suggests categorical perception of face view. The present study concludes that face view and size are processed by parallel mechanisms.

Adult↗

With a careful look: still no low-level confound to face pop-out.

In this issue of Vision Research, VanRullen, R. (2006). On second glance: Still no high-level pop-out effect for faces. Vision Research, in press. challenges our earlier Vision Research paper, "At first sight: A high-level pop-out effect for faces" (Hershler, O., & Hochstein, S. (2005). At first sight: A high-level pop-out effect for faces. Vision Research, 45, 1707-1724). In that paper, we showed that faces pop-out from a great variety of heterogeneous distractors. This search must have been based on a holistic combination of facial features, since it could not have relied on any single low-level distinguishing feature-each of which was present in at least some of the distractors. VanRullen implies that the pop-out effect is not limited to faces, is not holistic, and is due to a low-level confound, namely that the "low-level" Fourier amplitude spectrum may differentiate between faces and other categories. We now show that he fails to substantiate all three claims. His first experiment replicates our own and shows once again that faces do indeed pop-out, while other objects, such as cars, do not. The claim regarding the non-holistic nature of face search is based on a failure to differentiate between holistic processing for face detection and for individual face identification. His central claim is that the Fourier amplitude spectrum is processed low-level and could be used for face pop-out. However, changing the amplitude spectrum may well affect high-level representations as well. For example, his demonstration uses hybrid images which are extremely fuzzy, rendering them difficult to identify. More importantly, this claim would lead to the conclusion that targets with a non-face phase spectrum and only a face amplitude spectrum would pop-out among distractors with different amplitude spectra. We demonstrate that this is, of course, not the case and that the Fourier amplitude is not the hoped for "low-level confound". Until another such "hidden" low level feature is found, we must accept that face pop out depends on a high level mechanism.

Discrimination, Psychological↗

Implicit face perception in a patient with visual agnosia? Evidence from behavioural and eye-tracking analyses.

This paper investigates face perception in a visual agnosic and prosopagnosic patient (SB). Despite very extensive lesions of visual areas, SB remains capable of some visual processing [Brain 125 (2002) 58]. However, in everyday situations SB does not exhibit signs of specific face recognition. To investigate how SB may process faces, we tested two hypotheses. According to the 'spared module hypothesis,' SBs abilities come from spared modules of implicit face processing. According to the 'general strategy hypothesis,' SB may have developed some deliberate compensatory strategies. A two-session experimental design was constructed. In both sessions, face and non-face pictures were shown to participants. In Session 1 (implicit condition), participants had to decide whether each picture was a vegetable. In Session 2 (explicit condition), participants had to decide whether each picture was a face. Verbal reports showed that SB was not aware of faces in Session 1. However, behavioural results showed that (1). SB could process faces; (2). even when SB was not aware of faces, he processed them differently than non-faces; (3). when knowing the presence of faces, he did not process faces better. In addition, eye-tracking data suggested that SB did not change the nature of his processing from Sessions 1 to 2. Pupil diameters showed that fixated facial features were processed similarly as in control participants. Together, these results are not compatible with a general compensatory strategy hypothesis and suggest sparing of an implicit face processing module in SB.

Adult↗

The size-tuning of the face-distortion after-effect.

Recently, Webster and MacLin demonstrated a face-distortion after-effect (FDAE) for both upright and inverted faces: adaptation to a distorted face makes a normal face appear distorted in the direction opposite to the adapting direction. Neurophysiological studies (e.g. Experimental Brain Research 65 (1986) 38) show that face-selective neurons in the superior temporal sulcus (STS) are remarkably size-invariant in their responses. If the site of adaptation underlying the FDAE is the homologous neuron population in human vision, then the FDAE should also be highly tolerant to changes in size between adapting and test faces. Here, we test this prediction. Observers were adapted to distorted upright/inverted faces of three different sizes (3.3 degrees x 3.7 degrees, 6.6 degrees x 7.5 degrees, and 13.1 degrees x 14.8 degrees ). For adapting faces of all three sizes, observers adjusted test faces of all three sizes until they appeared normal. Significant FDAEs were observed in all conditions. For both upright and inverted faces, FDAEs were approximately twice as strong when adapting and test faces were the same size than when they differed by even a single octave in size. The magnitudes of FDAEs were comparable for upright and inverted faces. The larger FDAEs for same-size adapting and test faces suggest that part of the FDAE derives from a neuron population with narrow size-tuning. However, the significant FDAEs obtained for adapting and test images differing by two octaves implicate a different neuron population with broad size-tuning, possibly the human homolog of the face-selective neuron population in monkey STS.

Afterimage↗

Estradiol selectively affects processing of conspecifics' faces in female rhesus monkeys.

Estrogen deficiency following ovariectomy or menopause increases the risk of developing diseases such as osteoporosis and may also lead to memory impairment. Although estrogen replacement therapy (ERT) alleviates many symptoms associated with estrogen loss, it is not clear whether it also benefits cognitive function. The effect of estrogens upon cognition can best be studied in an animal model of human menopause, in which estrogen levels can be experimentally manipulated. Six young ovariectomized female rhesus monkeys (6-9 years old) were tested on a battery of touchscreen-based cognitive tasks, including the Matching-to-Sample (MTS) task with mixed delays and the spatial, object, and face conditions of the Delayed Recognition Span Test (DRST). Monkeys were tested 5 days a week, one task per week, for a total of 8 months, while undergoing treatments with placebo and ethinyl estradiol (EE2) in alternating 28-days blocks. Blood samples were collected to verify EE2 levels. We also observed the monkeys by video monitor during test sessions and recorded locomotor activity and response topology. Performance on the face-DRST, a task that involved selecting the new face in an increasing array of rhesus monkey faces, was impaired by EE2 treatment, as compared to placebo. Other tasks were unaffected by EE2. There was no clear evidence of EE2 effects upon motor activity or anxiety. In order to test the reliability of our findings, we conducted an additional experiment in which the monkeys were again given the face-DRST with different categories of face stimuli for 4 months, while receiving placebo and EE2 in alternating 7-days blocks. They performed each task 4-5 days/week for 4 weeks with (1) the same rhesus monkey faces as in the first experiment, (2) human faces, (3) chimpanzee faces, and (4) novel rhesus monkey faces. Face-DRST performance did not vary as a function of treatment when human or chimpanzee faces were used as stimuli. In contrast, periods of EE2 treatment were associated with a lower performance for both sets of rhesus monkey faces. These findings suggest that EE2 treatment has a detrimental effect on processing faces of conspecifics by female rhesus monkeys. We speculate that estrogens may produce this effect by enhancing emotional reactivity to socially relevant stimuli.

Animals↗

Regional variation in the inversion effect for faces: differential effects for feature shape, feature configuration, and external contour.

Faces are perceived via an orientation-dependent expert mechanism. We previously showed that inversion impaired perception of the spatial relations of features more in the lower face than in the (more salient) upper face, suggests a failure to rapidly process this type of structural data from the entire face. In this study we wished to determine if this interaction between inversion and regional salience, which we consider a marker for efficient whole-face processing, was specific to second-order (coordinate) spatial relations or also affected other types of structural information in faces. We used an oddity paradigm to test the ability of seventeen subjects to discriminate changes in feature size, feature spatial relations, and external contour in both the upper and lower face. We also tested fourteen subjects on perception of two different types of spatial relations: second-order changes that create plausible alternative faces, and illegal spatial changes that transgress normal rules of facial geometry. In both experiments we examined for asymmetries between upper-face and lower-face perceptual accuracy with brief stimulus presentations. While all structural changes were less easily discerned in inverted faces, only changes to spatial relations showed a marked asymmetry between the upper and lower face, with far worse performance in the mouth region. Furthermore, this asymmetry was found only for second-order spatial relations and not illegal spatial changes. These results suggest that the orientation-dependent face mechanism has a rapid whole-face processing capacity specific to the internal second-order (coordinate) spatial relations of facial features.

Adult↗