Face-coding Mechanisms Research Articles

Facial expression coding in children and adolescents with autism: Reduced adaptability but intact norm-based coding.

Individuals with autism spectrum disorder (ASD) can have difficulty recognizing emotional expressions. Here, we asked whether the underlying perceptual coding of expression is disrupted. Typical individuals code expression relative to a perceptual (average) norm that is continuously updated by experience. This adaptability of face-coding mechanisms has been linked to performance on various face tasks. We used an adaptation aftereffect paradigm to characterize expression coding in children and adolescents with autism. We asked whether face expression coding is less adaptable in autism and whether there is any fundamental disruption of norm-based coding. If expression coding is norm-based, then the face aftereffects should increase with adaptor expression strength (distance from the average expression). We observed this pattern in both autistic and typically developing participants, suggesting that norm-based coding is fundamentally intact in autism. Critically, however, expression aftereffects were reduced in the autism group, indicating that expression-coding mechanisms are less readily tuned by experience. Reduced adaptability has also been reported for coding of face identity and gaze direction. Thus, there appears to be a pervasive lack of adaptability in face-coding mechanisms in autism, which could contribute to face processing and broader social difficulties in the disorder.

Individual differences in adaptive norm-based coding and holistic coding are associated yet each contributes uniquely to unfamiliar face recognition ability.

We can discriminate and recognize many faces, despite their visual similarity. Individual differences in this ability have been linked to 2 face coding mechanisms: adaptive norm-based coding of identity and holistic coding. However, it is not yet known whether these mechanisms are distinct. Nor is it known whether they make unique contributions to face recognition ability because no studies have measured the operation of both these mechanisms in the same individuals. We measured individual differences in both the strength of adaptive norm-based coding (with a face identity aftereffect task) and holistic coding (with a composite face task). For the first time, we show that these 2 mechanisms are positively and moderately associated and that each makes significant unique contributions to unfamiliar face recognition ability (Cambridge Face Memory Test [CMFT]). Importantly, these relationships were face-specific. We also show that the combined contribution of these mechanisms to face recognition performance is significantly larger than the contribution of nonface recognition memory, consistent with the view that face recognition relies on the operation of face-sensitive mechanisms. Overall, our results raise intriguing questions regarding what these mechanisms may have in common, and what other mechanisms support face recognition performance. (PsycINFO Database Record

Reduced adaptability, but no fundamental disruption, of norm‐based face coding following early visual deprivation from congenital cataracts

Faces are adaptively coded relative to visual norms that are updated by experience, and this adaptive coding is linked to face recognition ability. Here we investigated whether adaptive coding of faces is disrupted in individuals (adolescents and adults) who experience face recognition difficulties following visual deprivation from congenital cataracts in infancy. We measured adaptive coding using face identity aftereffects, where smaller aftereffects indicate less adaptive updating of face-coding mechanisms by experience. We also examined whether the aftereffects increase with adaptor identity strength, consistent with norm-based coding of identity, as in typical populations, or whether they show a different pattern indicating some more fundamental disruption of face-coding mechanisms. Cataract-reversal patients showed significantly smaller face identity aftereffects than did controls (Experiments 1 and 2). However, their aftereffects increased significantly with adaptor strength, consistent with norm-based coding (Experiment 2). Thus we found reduced adaptability but no fundamental disruption of norm-based face-coding mechanisms in cataract-reversal patients. Our results suggest that early visual experience is important for the normal development of adaptive face-coding mechanisms.

Reduced adaptability, but no fundamental disruption, of norm-based face-coding mechanisms in cognitively able children and adolescents with autism

Faces are adaptively coded relative to visual norms that are updated by experience. This coding is compromised in autism and the broader autism phenotype, suggesting that atypical adaptive coding of faces may be an endophenotype for autism. Here we investigate the nature of this atypicality, asking whether adaptive face-coding mechanisms are fundamentally altered, or simply less responsive to experience, in autism. We measured adaptive coding, using face identity aftereffects, in cognitively able children and adolescents with autism and neurotypical age- and ability-matched participants. We asked whether these aftereffects increase with adaptor identity strength as in neurotypical populations, or whether they show a different pattern indicating a more fundamental alteration in face-coding mechanisms. As expected, face identity aftereffects were reduced in the autism group, but they nevertheless increased with adaptor strength, like those of our neurotypical participants, consistent with norm-based coding of face identity. Moreover, their aftereffects correlated positively with face recognition ability, consistent with an intact functional role for adaptive coding in face recognition ability. We conclude that adaptive norm-based face-coding mechanisms are basically intact in autism, but are less readily calibrated by experience.

Individual differences in adaptive coding of face identity are linked to individual differences in face recognition ability.

Despite their similarity as visual patterns, we can discriminate and recognize many thousands of faces. This expertise has been linked to 2 coding mechanisms: holistic integration of information across the face and adaptive coding of face identity using norms tuned by experience. Recently, individual differences in face recognition ability have been discovered and linked to differences in holistic coding. Here we show that they are also linked to individual differences in adaptive coding of face identity, measured using face identity aftereffects. Identity aftereffects correlated significantly with several measures of face-selective recognition ability. They also correlated marginally with own-race face recognition ability, suggesting a role for adaptive coding in the well-known other-race effect. More generally, these results highlight the important functional role of adaptive face-coding mechanisms in face expertise, taking us beyond the traditional focus on holistic coding mechanisms.

Autistic traits are linked to reduced adaptive coding of face identity and selectively poorer face recognition in men but not women

Our ability to discriminate and recognize thousands of faces despite their similarity as visual patterns relies on adaptive, norm-based, coding mechanisms that are continuously updated by experience. Reduced adaptive coding of face identity has been proposed as a neurocognitive endophenotype for autism, because it is found in autism and in relatives of individuals with autism. Autistic traits can also extend continuously into the general population, raising the possibility that reduced adaptive coding of face identity may be more generally associated with autistic traits. In the present study, we investigated whether adaptive coding of face identity decreases as autistic traits increase in an undergraduate population. Adaptive coding was measured using face identity aftereffects, and autistic traits were measured using the Autism-Spectrum Quotient (AQ) and its subscales. We also measured face and car recognition ability to determine whether autistic traits are selectively related to face recognition difficulties. We found that men who scored higher on levels of autistic traits related to social interaction had reduced adaptive coding of face identity. This result is consistent with the idea that atypical adaptive face-coding mechanisms are an endophenotype for autism. Autistic traits were also linked with face-selective recognition difficulties in men. However, there were some unexpected sex differences. In women, autistic traits were linked positively, rather than negatively, with adaptive coding of identity, and were unrelated to face-selective recognition difficulties. These sex differences indicate that autistic traits can have different neurocognitive correlates in men and women and raise the intriguing possibility that endophenotypes of autism can differ in males and females.

Autistic traits and adaptive coding of face identity

Event Abstract Back to Event Autistic traits and adaptive coding of face identity Gillian Rhodes1*, Linda Jeffery1, Libby Taylor1 and Louise Ewing1 1 ARC Centre of Excellence in Cognition and its Disorders, School of Psychology, University of Western Australia, Australia Background Our ability to discriminate and recognize thousands of faces despite their similarity as visual patterns relies on adaptive, norm-based, coding mechanisms that are continuously updated by experience. Reduced adaptive coding of face identity has been proposed as a neurocognitive endophenotype for autism, because it is found in autism and in relatives of individuals with autism. Autistic traits can also extend continuously into the general population, raising the possibility that reduced adaptive coding of face identity may be more generally associated with autistic traits. In the present study, we investigated whether adaptive coding of face identity decreases as autistic traits increase in an undergraduate population. Methods Adaptive coding was measured using face identity aftereffects, and autistic traits were measured using the Autism-Spectrum Quotient (AQ) and its subscales. We also measured face and car recognition ability to determine whether autistic traits are selectively related to face recognition difficulties. Results We found that men who scored higher on levels of autistic traits related to social interaction had reduced adaptive coding of face identity. This result is consistent with the idea that atypical adaptive face-coding mechanisms are an endophenotype for autism. Autistic traits were also linked with face-selective recognition difficulties in men. However, there were some unexpected sex differences. In women, autistic traits were linked positively, rather than negatively, with adaptive coding of identity, and were unrelated to face-selective recognition difficulties. Discussion The sex differences observed here indicate that autistic traits can have different neurocognitive correlates in men and women and raise the intriguing possibility that endophenotypes of autism can differ in men and women. However, our results suggest that, at least for men, atypical adaptive coding of faces may be an endophenotype for autism. Acknowledgements This research was supported by the Australian Research Council Centre of Excellence in Cognition and its Disorders (CE110001021), an ARC Professorial Fellowship to Rhodes (DP0877379) and an ARC Discovery Outstanding Researcher Award to Rhodes (DP130102300). We thank Mayu Nishimura and Daphne Maurer for co-creating the Robbers Game used in the Identity Aftereffects task and Ainsley Read for assistance with testing. Ethical approval was granted by the Human Research Ethics Committee of the Univer Keywords: autistic traits, broader autism phenotype, face recognition, face identity aftereffects, adaptive coding, Endophenotypes Conference: ACNS-2013 Australasian Cognitive Neuroscience Society Conference, Clayton, Melbourne, Australia, 28 Nov - 1 Dec, 2013. Presentation Type: Oral Topic: Other Citation: Rhodes G, Jeffery L, Taylor L and Ewing L (2013). Autistic traits and adaptive coding of face identity. Conference Abstract: ACNS-2013 Australasian Cognitive Neuroscience Society Conference. doi: 10.3389/conf.fnhum.2013.212.00193 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 15 Oct 2013; Published Online: 25 Nov 2013. * Correspondence: Prof. Gillian Rhodes, ARC Centre of Excellence in Cognition and its Disorders, School of Psychology, University of Western Australia, perth, Australia, gillian.rhodes@uwa.edu.au Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Gillian Rhodes Linda Jeffery Libby Taylor Louise Ewing Google Gillian Rhodes Linda Jeffery Libby Taylor Louise Ewing Google Scholar Gillian Rhodes Linda Jeffery Libby Taylor Louise Ewing PubMed Gillian Rhodes Linda Jeffery Libby Taylor Louise Ewing Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Ignored Faces Produce Figural Face Aftereffects

Following adaptation to faces with contracted (or expanded) internal features, faces previously perceived as normal appear distorted in the opposite direction. This figural face aftereffect suggests face-coding mechanisms adapt to changes in the spatial relations of features and/or the global structure of faces. Here, we investigated whether the figural aftereffect requires spatial attention. Participants ignored a distorted adapting face and performed a highly demanding letter-count task. Before and after adaptation, participants rated the normality of morphed distorted faces ranging from 50% contracted through undistorted to 50% expanded. A robust aftereffect was observed. These results suggest that the figural face aftereffect can occur in the absence of spatial attention, even when the attentional demands of the relevant task are high.

Enhanced attention amplifies face adaptation

Perceptual adaptation not only produces striking perceptual aftereffects, but also enhances coding efficiency and discrimination by calibrating coding mechanisms to prevailing inputs. Attention to simple stimuli increases adaptation, potentially enhancing its functional benefits. Here we show that attention also increases adaptation to faces. In Experiment 1, face identity aftereffects increased when attention to adapting faces was increased using a change detection task. In Experiment 2, figural (distortion) face aftereffects increased when attention was increased using a snap game (detecting immediate repeats) during adaptation. Both were large effects. Contributions of low-level adaptation were reduced using free viewing (both experiments) and a size change between adapt and test faces (Experiment 2). We suggest that attention may enhance adaptation throughout the entire cortical visual pathway, with functional benefits well beyond the immediate advantages of selective processing of potentially important stimuli. These results highlight the potential to facilitate adaptive updating of face-coding mechanisms by strategic deployment of attentional resources.

Orientation-sensitivity of face identity aftereffects

Our ability to recognize faces despite their similarity as visual patterns depends on high-level face-coding mechanisms that are strongly tuned to upright faces. If face aftereffects reflect adaptation of these mechanisms, as widely assumed, then they should be sensitive to face orientation. Previous studies have not supported this hypothesis, but have generally used a figural aftereffect paradigm, which may not optimally engage expert face-coding mechanisms. Here, we used an identity aftereffect paradigm, which requires identification of target faces, to provide a stronger test of the hypothesis. We measured identity aftereffects for upright and inverted faces, with and without eliminating low-level retinotopic adaptation. Baseline identification performance was substantially better for upright than inverted faces, confirming that our task tapped orientation-selective face expertise. With orientation varied between participants, aftereffects were almost twice as large for upright as inverted faces, on three different aftereffect measures (change in threshold, change in overall proportion correct, change in perceived identity of the average face). With orientation varied within participants, the results were less clear. We suggest that adaptation of expert face-coding mechanisms can contribute to face identity aftereffects, although the effect may not be very robust.

View-Contingent Aftereffects Suggest Joint Coding of Face Shape and View

While it is well established that different neural populations code different face views, behavioural evidence that these neurons also code other aspects of face shape is equivocal. For example, previous studies have interpreted the partial transfer of face aftereffects across different viewpoints as evidence for either view-specific coding of face shape or that the locus of adaptation is in face-coding mechanisms that are relatively robust to changes in face view. Here we show that it is possible to simultaneously induce aftereffects in opposite directions for 3/4 and front views of upright faces with manipulated mouth position (experiment 1). For example, simultaneous adaptation to 3/4 views with raised mouth position and front views with lowered mouth position caused raised mouth position to appear more normal for 3/4 views of novel faces, but less normal for front views. View-contingent adaptation did not occur for inverted faces, however (experiment 2). Dissociable aftereffects for different views of upright faces, but not for different views of inverted faces, suggest that neurons that code face view can also code other aspects of face shape.

Contact, configural coding and the other‐race effect in face recognition

The other-race effect (ORE) in face recognition describes a well-established finding of better recognition for own-race than other-race faces. Although widely thought to reflect differences in contact between own- and other-race faces, little is known about how different contact levels relate to changes in processing of those faces. This study investigated how contact affects the size of the ORE and the use of expert configural face-coding mechanisms. Using inversion decrements as an index of configural coding, we predicted that increased self-reported contact would be associated with greater use of configural-coding mechanisms. Chinese and Caucasian participants varying in contact with other-race faces were recruited. The Chinese participants also varied in their length of residence in a Western country. Results showed that higher levels of contact were associated with a reduction in the ORE in both face recognition and configural coding. Importantly, smaller cross-race differences in configural coding were also associated with a smaller ORE in face recognition.

Specialised Higher-Level Mechanisms for Facial-Symmetry Perception: Evidence from Orientation-Tuning Functions

Bilateral symmetry is important in many perceptual analyses from low-level figure-ground segmentation to higher-level face and object perception. Despite the success of low-level, image-based symmetry-detection models, these may not provide a complete account of symmetry perception. Better symmetry detection and stronger preferences for symmetry in upright faces than comparable patterns (e.g. inverted faces) that do not engage specialised face-coding mechanisms suggest a contribution of higher-level mechanisms to symmetry perception. We replicated better symmetry detection and stronger symmetry preferences for upright than inverted faces in experiment 1, and examined their orientation tuning in more detail in experiment 2. Decreasing performance as faces are mis-oriented away from the canonical upright orientation is the signature of specialised face-processing mechanisms, which are engaged less effectively as faces are mis-oriented. Lower-level symmetry-detection mechanisms, which operate better with vertical than horizontal, and horizontal than oblique, axes of symmetry would produce a W-shaped orientation-tuning function. Identical orientation-tuning functions were obtained for symmetry detection and preferences. Both declined with increasing mis-orientation over the 0 degrees-135 degrees range, consistent with a contribution from specialised face-coding mechanisms. Both increased from 135 degrees to 180 degrees, consistent with reliance on lower-level image-based mechanisms for severely misoriented faces. Taken together, the results implicate specialised, higher-level mechanisms in the detection of, and preference for, facial symmetry.

Abnormal Adaptive Face-Coding Mechanisms in Children with Autism Spectrum Disorder

In low-level vision, exquisite sensitivity to variation in luminance is achieved by adaptive mechanisms that adjust neural sensitivity to the prevailing luminance level. In high-level vision, adaptive mechanisms contribute to our remarkable ability to distinguish thousands of similar faces [1]. A clear example of this sort of adaptive coding is the face-identity aftereffect [2, 3, 4, 5], in which adaptation to a particular face biases perception toward the opposite identity. Here we investigated face adaptation in children with autism spectrum disorder (ASD) by asking them to discriminate between two face identities, with and without prior adaptation to opposite-identity faces. The ASD group discriminated the identities with the same precision as did the age- and ability-matched control group, showing that face identification per se was unimpaired. However, children with ASD showed significantly less adaptation than did their typical peers, with the amount of adaptation correlating significantly with current symptomatology, and face aftereffects of children with elevated symptoms only one third those of controls. These results show that although children with ASD can learn a simple discrimination between two identities, adaptive face-coding mechanisms are severely compromised, offering a new explanation for previously reported face-perception difficulties [6, 7, 8] and possibly for some of the core social deficits in ASD [9, 10].

Orientation-Contingent Face Aftereffects and Implications for Face-Coding Mechanisms

Humans have an impressive ability to discriminate between faces despite their similarity as visual patterns. This expertise relies on configural coding of spatial relations between face features and/or holistic coding of overall facial structure. These expert face-coding mechanisms appear to be engaged most effectively by upright faces, with inverted faces engaging primarily feature-coding mechanisms. We show that opposite figural aftereffects can be induced simultaneously for upright and inverted faces, demonstrating that distinct neural populations code upright and inverted faces. This result also suggests that expert (upright) face-coding mechanisms can be selectively adapted. These aftereffects occur for judgments of face normality and face gender and are robust to changes in face size, ruling out adaptation of low-level, retinotopically organized coding mechanisms. Our results suggest a resolution of a paradox in the face recognition literature. Neuroimaging studies have found surprisingly little orientation selectivity in the fusiform face area (FFA) despite evidence that this region plays a role in expert face coding and that expert face-coding mechanisms are selectively engaged by upright faces. Our results, demonstrating orientation-contingent adaptation of face-coding mechanisms, suggest that the FFA's apparent lack of orientation selectivity may be an artifact of averaging across distinct populations within the FFA that respond to upright and inverted faces.