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At least 19 recordsLinked to original sources
PubMed2002

Synthetic faces, face cubes, and the geometry of face space.

To simplify the study of visual face processing, we introduce a novel class of synthetic face stimuli based upon 37 measurements (head shape, feature locations, etc.) extracted from individual face photographs in both frontal and 20 degrees side views. Synthetic faces are bandpass filtered optimally for face perception and include both line and edge information. Pilot experiments establish that subjects are extremely accurate in matching a synthetic face with the original grayscale photograph, even across views. To determine the perceptual metric of face space, we introduce face cubes in which the geometric differences between any faces in a four-dimensional face subspace can be precisely determined. Experiments on face discrimination using face cubes establish the metric of synthetic face space as locally Euclidean, with discrimination thresholds representing 4-6% total geometric variation (as a percent of mean head radius) between faces. Discrimination thresholds are lowest for face cubes constructed around the average face, thus indicating that the mean face for each gender represents a natural origin for face space. Finally, synthetic faces exhibit a pronounced inversion effect for 20 degrees side views and a characteristic "Thatcher effect" for inverted front views. Synthetic faces and face cubes thus provide a useful new quantitative approach to the study of face perception and face space.

Computer Simulation↗
PubMed2005

The fusiform face area is not sufficient for face recognition: evidence from a patient with dense prosopagnosia and no occipital face area.

We tested functional activation for faces in patient D.F., who following acquired brain damage has a profound deficit in object recognition based on form (visual form agnosia) and also prosopagnosia that is undocumented to date. Functional imaging demonstrated that like our control observers, D.F. shows significantly more activation when passively viewing face compared to scene images in an area that is consistent with the fusiform face area (FFA) (p < 0.01). Control observers also show occipital face area (OFA) activation; however, whereas D.F.'s lesions appear to overlap the OFA bilaterally. We asked, given that D.F. shows FFA activation for faces, to what extent is she able to recognize faces? D.F. demonstrated a severe impairment in higher level face processing--she could not recognize face identity, gender or emotional expression. In contrast, she performed relatively normally on many face categorization tasks. D.F. can differentiate faces from non-faces given sufficient texture information and processing time, and she can do this is independent of color and illumination information. D.F. can use configural information for categorizing faces when they are presented in an upright but not a sideways orientation and given that she also cannot discriminate half-faces she may rely on a spatially symmetric feature arrangement. Faces appear to be a unique category, which she can classify even when she has no advance knowledge that she will be shown face images. Together, these imaging and behavioral data support the importance of the integrity of a complex network of regions for face identification, including more than just the FFA--in particular the OFA, a region believed to be associated with low-level processing.

Adolescent↗
PubMed1989

Electric brain potentials evoked by pictures of faces and non-faces: a search for "face-specific" EEG-potentials.

In three different experimental series, electroencephalographic responses evoked by changes in pictorial patterns were recorded in 29 adult human subjects (19 females, 10 males). Quantitative data evaluation for the evoked responses from electrodes T5, T6, Cz, Pz (10-20 system) was performed. The stimuli were projected to a 4 x 6 degree binocularly viewed field. The patterns changed within 6 ms every 2.5-4.5 s according to a random program. Paradigm (1): Identical line drawings of a face, a tree and a chair were used, either black on white (P-stimuli) or white on black (N-stimuli); in each set altogether 160 slides appeared in semi-random order. At Cz and Pz a prototypical EEG-response evoked by face stimuli was found exhibiting 3 prominent peaks, very similar for P-stimuli and N-stimuli. A P150 maximum was especially pronounced in the responses to face stimuli but absent in the evoked potentials aroused by chair or tree stimuli. The difference curves (face-chair, face-tree, chair-tree) supported the hypothesis of "face-responsive" components in these responses. Paradigm (2): 4 x 6 degree slides (black and white photographs) of 54 different human faces, 53 different vases and 53 different pairs of shoes were projected as in paradigm (1), but instruction to the subjects on a supposed post-test memory task raised their attention during the recordings. "Face-responsive" components (an early N 140-160, P 210-240, N 300) were more marked in female than in male subjects, and again most pronounced at electrode Cz. Paradigm (3): When a recognition task was included in paradigm (2)--9 out of 192 items were memorized 20 minutes before the recording session--essentially the same evoked potentials were obtained as in (2), but an additional late positive wave (450-600 ms) appeared in the responses to all stimuli. We assume that the "face-specific" components--a designation which is used cautiously considering the limited number of non-face stimuli--do not originate in the temporo-occipital cortical face region, but in limbic structures (amygdala, hippocampus) deep in the temporal lobe or in the gyrus cinguli. In the present study no significant hemispheric differences (T5, T6) in the evoked responses were found (all stimulus categories), but such differences are known to appear with highly schematic face stimuli.

Adult↗
PubMed2006

Face perception in high-functioning autistic adults: evidence for superior processing of face parts, not for a configural face-processing deficit.

Configural processing in autism was studied in Experiment 1 by using the face inversion effect. A normal inversion effect was observed in the participants with autism, suggesting intact configural face processing. A priming paradigm using partial or complete faces served in Experiment 2 to assess both local and configural face processing. Overall, normal priming effects were found in participants with autism, irrespective of whether the partial face primes were intuitive face parts (i.e., eyes, nose, etc.) or arbitrary segments. An exception, however, was that participants with autism showed magnified priming with single face parts relative to typically developing control participants. The present findings argue for intact configural processing in autism along with an enhanced processing for individual face parts. The face-processing peculiarities known to characterize autism are discussed on the basis of these results and past congruent results with nonsocial stimuli.

Adolescent↗
PubMed2003

Role of face-to-face and edge-to-face aromatic interactions in the inclusion complexation of cyclobis(paraquat-p-phenylene): a theoretical study.

A B3LYP/6-31G(d,p) and MP2/6-31G(d,p)//B3LYP/6-31G(d,p) computational study of the gas-phase complexation of cyclobis(paraquat-p-phenylene) (1(4+)) with four typical aromatic guests, namely, 1,4-dimethoxybenzene (2), 1,5-dimethoxynaphthalene (3), benzidine (4), and tetrathiafulvalene (5), has been carried out. The structure of the host has been successively split into two responsible substructures, respectively, for the face-to-face and edge-to-face interactions with the guests. The sum of the two interactions calculated at the B3LYP/6-31G(d,p) and MP2/6-31G(d,p)//B3LYP/6-31G(d,p) levels for each guest proved to be in good agreement with the overall binding energy of the host calculated at the corresponding level of theory. The results show that the binding of the complexes is primarily due to London dispersion interactions which require wave function-based correlation methods for an adequate description. Face-to-face interactions are about 1 order of magnitude more important than edge-to-face interactions in determining the overall binding energy. While edge-to-face interactions essentially depend on London dispersion forces, face-to-face interactions depend about one-half on electrostatic and frontier orbital contributions (the latter being more important) and the other half on London dispersion forces.

Journal Article↗
PubMedDate not supplied

Electrophysiological studies of human face perception. I: Potentials generated in occipitotemporal cortex by face and non-face stimuli.

This and the following two papers describe event-related potentials (ERPs) evoked by visual stimuli in 98 patients in whom electrodes were placed directly upon the cortical surface to monitor medically intractable seizures. Patients viewed pictures of faces, scrambled faces, letter-strings, number-strings, and animate and inanimate objects. This paper describes ERPs generated in striate and peristriate cortex, evoked by faces, and evoked by sinusoidal gratings, objects and letter-strings. Short-latency ERPs generated in striate and peristriate cortex were sensitive to elementary stimulus features such as luminance. Three types of face-specific ERPs were found: (i) a surface-negative potential with a peak latency of approximately 200 ms (N200) recorded from ventral occipitotemporal cortex, (ii) a lateral surface N200 recorded primarily from the middle temporal gyrus, and (iii) a late positive potential (P350) recorded from posterior ventral occipitotemporal, posterior lateral temporal and anterior ventral temporal cortex. Face-specific N200s were preceded by P150 and followed by P290 and N700 ERPs. N200 reflects initial face-specific processing, while P290, N700 and P350 reflect later face processing at or near N200 sites and in anterior ventral temporal cortex. Face-specific N200 amplitude was not significantly different in males and females, in the normal and abnormal hemisphere, or in the right and left hemisphere. However, cortical patches generating ventral face-specific N200s were larger in the right hemisphere. Other cortical patches in the same region of extrastriate cortex generated grating-sensitive N180s and object-specific or letter-string-specific N200s, suggesting that the human ventral object recognition system is segregated into functionally discrete regions.

Adolescent↗
PubMed2000

Categorical perception occurs in newly learned faces, other-race faces, and inverted faces.

On the basis of findings that categorical perception (CP) is possible in complex visual stimuli such as faces, the present study tested for CP on continua between unfamiliar face pairs. Results indicate that CP can be observed for unfamiliar faces, in both familiar (same-race) and unfamiliar (other-race) groups. In addition, significant CP effects were observed in inverted faces. Finally, half-continua were tested where midpoint stimuli became endpoints. This was done to ensure that stimulus artifacts did not account for the observed CP effects. Consistent with the perceptual rescaling associated with CP, half-continua showed a rescaled CP effect. We argue that these CP effects are based on the rapid acquisition of perceptual equivalence classes.

Adult↗
PubMed2005

Cocaine exposure is associated with subtle compromises of infants' and mothers' social-emotional behavior and dyadic features of their interaction in the face-to-face still-face paradigm.

Prenatal cocaine and opiate exposure are thought to subtly compromise social and emotional development. The authors observed a large sample of 236 cocaine-exposed and 459 nonexposed infants (49 were opiate exposed and 646 nonexposed) with their mothers in the face-to-face still-face paradigm. Infant and maternal behaviors were microanalytically coded. No opiate-exposure effects were detected. However, mothers of cocaine-exposed infants showed more negative engagement than other mothers. The cocaine-exposed dyads also showed higher overall levels of mismatched engagement states than other dyads, including more negative engagement when the infants were in states of neutral engagement. Infants exposed to heavier levels of cocaine showed more passive-withdrawn negative engagement and engaged in more negative affective matching with their mothers than other infants. Although effect sizes were small, cocaine exposure, especially heavy cocaine exposure, was associated with subtly negative interchanges, which may have a cumulative impact on infants' later development and their relationships with their mothers.

Adolescent↗
PubMed1993

Cooperative face-to-face and edge-to-face aromatic interactions of tryptophan indole ring with N7-quarternized guanine and neutral cytosine bases.

In order to investigate the effect of cytosine base upon the stacking interaction of N7-quarternized guanine base with tryptophan indole ring, the X-ray crystal structure of a 1:1 complex of model compounds 1 and 2 was carried out. Contrary to the expectation of the interaction of both molecules in aqueous solution, the crystal structure showed the first example of the simultaneous recognition of the Trp indole ring by guanine and cytosine bases by the coupling of the face-to-face and edge-to-face aromatic interactions, respectively.

Cytosine↗
PubMed2002

An electrochemically controllable nanomechanical molecular system utilizing edge-to-face and face-to-face aromatic interactions.

[formula: see text] A new molecular system, 2,11-dithio[4,4]metametaquinocyclophane containing a quinone moiety, was designed and synthesized. As the quinone moiety can readily be converted into an aromatic pi-system (hydroquinone) upon reduction, the nanomechanical molecular cyclophane system exhibits a large flapping motion like a molecular flipper from the electrochemical redox process. The conformational changes upon reduction and oxidation are caused by changes of nonbonding interaction forces (devoid of bond formation/breaking) from the edge-to-face to face-to-face aromatic interactions and vice versa, respectively.

Journal Article↗
PubMed2005

Gaining face or losing face? Framing the debate on face transplants.

An American surgical team has announced its intention to perform the first human facial transplantation. The team has, however, invited further analysis of the ethical issues before it proceeds and in this paper we take up that challenge in seeking to frame the debate with a particular focus on the recipients of the transplant. We address seven related areas of concern and identify numerous questions that require answers or, perhaps, better answers. We start by examining the nature of the procedure and its intended benefits, why the procedure is being developed, and whether or not this should be viewed as experimental. Having concluded that this is experimental in nature, we then consider the broad question, who is the patient? Here we perceive difficulties in terms of the autonomy of the recipient, the unpredictable effects of receiving the transplant, and the role and influence of society. We conclude by asking whether the question should be 'whether or not?' rather than 'when?', particularly while the risks of losing face appear to far outweigh the likelihood of gaining face.

Body Image↗
PubMed1999

Theoretical Study of the Conformations and Strain Energies of [n,n]Metaparacyclophanes: Indication of Stable Edge-to-Face and Displaced Face-to-Face Conformers for n = 4.

We have studied [n,n]metaparacyclophanes-model compounds exhibiting edge-to-face and displaced stacked aromatic-aromatic interactions-using semiempirical calculations for n = 2-5 and ab initio calculations for n = 2-4. For n = 2 and 3, the strain energies govern the conformational preference, while for n = 4 and 5 the aromatic-aromatic and strain energies are equally important. The 3,12-dithio[4,4]metaparacyclophanes exhibit edge-to-face aromatic-aromatic intereactions, while the [4,4]metaparacyclophanes and 2,11-dithio[4,4]metaparacyclophanes exhibit displaced stacked aromatic-aromatic interactions.

Journal Article↗
PubMed2006

Neural substrates for functionally discriminating self-face from personally familiar faces.

Understanding the neurobiological substrates of self-recognition yields important insight into socially and clinically critical cognitive functions such as theory of mind. Experimental evidence suggests that right frontal and parietal lobes preferentially process self-referent information. Recognition of one's own face is an important parameter of self-recognition, but well-controlled experimental data on the brain substrates of self-face recognition is limited. The goal of this study was to characterize the activation specific to self-face in comparison with control conditions of two levels of familiarity: unknown unfamiliar face and the more stringent control of a personally familiar face. We studied 12 healthy volunteers who made "unknown," "familiar," and "self" judgments about photographs of three types of faces: six different novel faces, a personally familiar face (participant's fraternity brother), and their own face during an event-related functional MRI (fMRI) experiment. Contrasting unknown faces with baseline showed activation of the inferior occipital lobe, which supports previous findings suggesting the presence of a generalized face-processing area within the inferior occipital-temporal region. Activation in response to a familiar face, when contrasted with an unknown face, invoked insula, middle temporal, inferior parietal, and medial frontal lobe activation, which is consistent with an existing hypothesis suggesting familiar face recognition taps neural substrates that are different from those involved in general facial processing. Brain response to self-face, when contrasted with familiar face, revealed activation in the right superior frontal gyrus, medial frontal and inferior parietal lobes, and left middle temporal gyrus. The contrast familiar vs. self produced activation only in the anterior cingulate gyrus. Our results support the existence of a bilateral network for both perceptual and executive aspects of self-face processing that cannot be accounted for by a simple hemispheric dominance model. This network is similar to those implicated in social cognition, mirror neuron matching, and face-name matching. Our findings also show that some regions of the medial frontal and parietal lobes are specifically activated by familiar faces but not unknown or self-faces, indicating that these regions may serve as markers of face familiarity and that the differences between activation associated with self-face recognition and familiar face recognition are subtle and appear to be localized to lateral frontal, parietal, and temporal regions.

Brain↗
PubMed2000

Effects of face inversion on the structural encoding and recognition of faces. Evidence from event-related brain potentials.

It was investigated how face inversion affects face-specific components of event-related brain potentials (ERPs) which are assumed to reflect the structural encoding and the recognition of faces. ERPs were recorded to upright and inverted photographs of familiar faces, unfamiliar faces, and houses. In Part I, participants had to detect infrequently presented targets (hands), in Part II, attention was either directed towards or away from the pictorial stimuli. When compared with upright unfamiliar faces, upright familiar faces elicited an enhanced negativity between 300 ms and 450 ms ('N400f') and an enhanced positivity between 450 and 650 ms post-stimulus ('P600f'). It is suggested that these ERP modulations are generated by processes involved in the recognition of faces. Face inversion is known to disrupt face recognition processes. Accordingly, 'N400f' and 'P600f' were generally absent in response to inverted familiar and unfamiliar faces. The face-specific N170 component at lateral posterior electrodes was not affected by face familiarity, indicating that it reflects processing stages prior to face identification. N170 was delayed and enhanced for inverted relative to upright faces. While N170 enhancements were also observed for inverted relative to upright houses, the N170 latency shift caused by stimulus inversion was face-specific. Directing attention away from the faces towards a demanding primary visual task resulted in an N170 delay for inverted as well as for upright faces, suggesting that the time course of structural encoding of faces is affected by attentional factors. These results demonstrate that ERPs can be used as electrophysiological markers of specialised brain processes underlying the structural encoding and subsequent recognition of faces.

Adolescent↗
PubMed2001

How does the brain discriminate familiar and unfamiliar faces?: a PET study of face categorical perception.

Where and how does the brain discriminate familiar and unfamiliar faces? This question has not been answered yet by neuroimaging studies partly because different tasks were performed on familiar and unfamiliar faces, or because familiar faces were associated with semantic and lexical information. Here eight subjects were trained during 3 days with a set of 30 faces. The familiarized faces were morphed with unfamiliar faces. Presented with continua of unfamiliar and familiar faces in a pilot experiment, a group of eight subjects presented a categorical perception of face familiarity: there was a sharp boundary in percentage of familiarity decisions between 40% and 60% faces. In the main experiment, subjects were scanned (PET) on the fourth day (after 3 days of training) in six conditions, all requiring a sex classification task. Completely novel faces (0%) were presented in Condition 1 and familiar faces (100%) in Condition 6, while faces of steps of 20% in the continuum of familiarity were presented in Conditions 2 to 5 (20% to 80%). A principal component analysis (PCA) indicated that most variations in neural responses were related to the dissociation between faces perceived as familiar (60% to 100%) and faces perceived as unfamiliar (0 to 40%). Subtraction analyses did not disclose any increase of activation for faces perceived as familiar while there were large relative increases for faces perceived as unfamiliar in several regions of the right occipito-temporal visual pathway. These changes were all categorical and were observed mainly in the right middle occipital gyrus, the right posterior fusiform gyrus, and the right inferotemporal cortex. These results show that (1) the discrimination between familiar and unfamiliar faces is related to relative increases in the right ventral pathway to unfamiliar/novel faces; (2) familiar and unfamiliar faces are discriminated in an all-or-none fashion rather than proportionally to their resemblance to stored representations; and (3) categorical perception of faces is associated with abrupt changes of brain activity in the regions that discriminate the two extremes of the multidimensional continuum.

Adult↗
PubMed2006

Activation of preexisting and acquired face representations: the N250 event-related potential as an index of face familiarity.

Electrophysiological studies using event-related potentials have demonstrated that face stimuli elicit a greater negative brain potential in right posterior recording sites 170 msec after stimulus onset (N170) relative to nonface stimuli. Results from repetition priming paradigms have shown that repeated exposures of familiar faces elicit a larger negative brainwave (N250r) at inferior temporal sites compared to repetitions of unfamiliar faces. However, less is known about the time course and learning conditions under which the N250 face representation is acquired. In the familiarization phase of the Joe/no Joe task, subjects studied a target "Joe" face ("Jane" for female subjects) and, during the course of the experiment, identified a series of sequentially presented faces as either Joe or not Joe. The critical stimulus conditions included the subject's own face, a same-sex Joe ( Jane) face and a same-sex "other" face. The main finding was that the subject's own face produced a focal negative deflection (N250) in posterior channels relative to nontarget faces. The task-relevant Joe target face was not differentiated from other nontarget faces in the first half of the experiment. However, in the second half, the Joe face produced an N250 response that was similar in magnitude to the own face. These findings suggest that the N250 indexes two types of face memories: a preexperimentally familiar face representation (i.e., the "own face" and a newly acquired face representation (i.e., the Joe/Jane face) that was formed during the course of the experiment.

Adolescent↗
PubMed2006

The fusiform face area: a cortical region specialized for the perception of faces.

Faces are among the most important visual stimuli we perceive, informing us not only about a person's identity, but also about their mood, sex, age and direction of gaze. The ability to extract this information within a fraction of a second of viewing a face is important for normal social interactions and has probably played a critical role in the survival of our primate ancestors. Considerable evidence from behavioural, neuropsychological and neurophysiological investigations supports the hypothesis that humans have specialized cognitive and neural mechanisms dedicated to the perception of faces (the face-specificity hypothesis). Here, we review the literature on a region of the human brain that appears to play a key role in face perception, known as the fusiform face area (FFA). Section 1 outlines the theoretical background for much of this work. The face-specificity hypothesis falls squarely on one side of a longstanding debate in the fields of cognitive science and cognitive neuroscience concerning the extent to which the mind/brain is composed of: (i) special-purpose ('domain-specific') mechanisms, each dedicated to processing a specific kind of information (e.g. faces, according to the face-specificity hypothesis), versus (ii) general-purpose ('domain-general') mechanisms, each capable of operating on any kind of information. Face perception has long served both as one of the prime candidates of a domain-specific process and as a key target for attack by proponents of domain-general theories of brain and mind. Section 2 briefly reviews the prior literature on face perception from behaviour and neurophysiology. This work supports the face-specificity hypothesis and argues against its domain-general alternatives (the individuation hypothesis, the expertise hypothesis and others). Section 3 outlines the more recent evidence on this debate from brain imaging, focusing particularly on the FFA. We review the evidence that the FFA is selectively engaged in face perception, by addressing (and rebutting) five of the most widely discussed alternatives to this hypothesis. In section 4, we consider recent findings that are beginning to provide clues into the computations conducted in the FFA and the nature of the representations the FFA extracts from faces. We argue that the FFA is engaged both in detecting faces and in extracting the necessary perceptual information to recognize them, and that the properties of the FFA mirror previously identified behavioural signatures of face-specific processing (e.g. the face-inversion effect). Section 5 asks how the computations and representations in the FFA differ from those occurring in other nearby regions of cortex that respond strongly to faces and objects. The evidence indicates clear functional dissociations between these regions, demonstrating that the FFA shows not only functional specificity but also area specificity. We end by speculating in section 6 on some of the broader questions raised by current research on the FFA, including the developmental origins of this region and the question of whether faces are unique versus whether similarly specialized mechanisms also exist for other domains of high-level perception and cognition.

Animals↗
PubMedDate not supplied

Electrophysiological studies of human face perception. II: Response properties of face-specific potentials generated in occipitotemporal cortex.

In the previous paper the locations and basic response properties of N200 and other face-specific event-related potentials (ERPs) were described. In this paper responsiveness of N200 and related ERPs to the perceptual features of faces and other images was assessed. N200 amplitude did not vary substantially, whether evoked by colored or grayscale faces; normal, blurred or line-drawing faces; or by faces of different sizes. Human hands evoked small N200s at face-specific sites, but evoked hand-specific ERPs at other sites. Cat and dog faces evoked N200s that were 73% as large as to human faces. Hemifield stimulation demonstrated that the right hemisphere is better at processing information about upright faces and transferring it to the left hemisphere, whereas the left hemisphere is better at processing information about inverted faces and transferring it to the right hemisphere. N200 amplitude was largest to full faces and decreased progressively to eyes, face contours, lips and noses viewed in isolation. A region just lateral to face-specific N200 sites was more responsive to internal face parts than to faces, and some sites in ventral occipitotemporal cortex were face-part-specific. Faces with eyes averted or closed evoked larger N200s than those evoked by faces with eyes forward. N200 amplitude and latency were affected by the joint effects of eye and head position in the right but not in the left hemisphere. Full and three-quarter views of faces evoked larger N200s than did profile views. The results are discussed in relation to behavioral studies in humans and single-cell recordings in monkeys.

Animals↗