Are Greebles like faces? Using the neuropsychological exception to test the rule

Longitudinal Changes in Functional Neural Activation and Sensitization During Face Processing in Fragile X Syndrome

BACKGROUND

Fragile X syndrome (FXS) is a genetic condition associated with increased risk for social anxiety and avoidance. Using functional near-infrared spectroscopy (fNIRS), we previously demonstrated aberrant neural activity responding to faces in young girls with FXS cross-sectionally. Here, we tested the hypothesis that abnormalities in neural activation and sensitization would increase with age in 65 girls with FXS (ages 6-16 years) relative to an age-matched control group of 52 girls who had comparable cognitive function and clinical symptoms.

METHODS

fNIRS data were collected at 2 time points (mean [SD] = 2.8 [0.6] years apart) during a face processing task. Linear mixed-effect models examined longitudinal neural profiles in girls with FXS and control participants. Correlational analysis was performed to examine associations between neural sensitization (increasing neural response to repeated stimuli) and clinical ratings.

RESULTS

In the FXS group, 24 participants had 1 fNIRS scan, and 32 had 2 scans. In the control group, 28 participants had 1 fNIRS scan, and 22 had 2 scans. Brain activations in the superior frontal gyrus were higher in girls with FXS than control participants at both time points. Neural sensitization also increased in girls with FXS at a higher rate than control participants in the superior frontal gyrus when responding to upright faces. For the FXS group, sensitization in the superior frontal gyrus positively correlated with longitudinal increases in anxiety and social avoidance scores.

CONCLUSIONS

Girls with FXS show increasingly abnormal neural activation and sensitization responding to faces over time. Aberrant neural sensitization in girls with FXS is associated with longitudinal changes in anxiety and social skills.

Aberrant Neural Response During Face Processing in Girls With Fragile X Syndrome: Defining Potential Brain Biomarkers for Treatment Studies

BACKGROUND

Children and adolescents with fragile X syndrome (FXS) manifest significant symptoms of anxiety, particularly in response to face-to-face social interaction. In this study, we used functional near-infrared spectroscopy to reveal a specific pattern of brain activation and habituation in response to face stimuli in young girls with FXS, an important but understudied clinical population.

METHODS

Participants were 32 girls with FXS (age: 11.8 ± 2.9 years) and a control group of 28 girls without FXS (age: 10.5 ± 2.3 years) matched for age, general cognitive function, and autism symptoms. Functional near-infrared spectroscopy was used to assess brain activation during a face habituation task including repeated upright/inverted faces and greeble (nonface) objects.

RESULTS

Compared with the control group, girls with FXS showed significant hyperactivation in the frontopolar and dorsal lateral prefrontal cortices in response to all face stimuli (upright + inverted). Lack of neural habituation (and significant sensitization) was also observed in the FXS group in the frontopolar cortex in response to upright face stimuli. Finally, aberrant frontopolar sensitization in response to upright faces in girls with FXS was significantly correlated with notable cognitive-behavioral and social-emotional outcomes relevant to this condition, including executive function, autism symptoms, depression, and anxiety.

CONCLUSIONS

These findings strongly support a hypothesis of neural hyperactivation and accentuated sensitization during face processing in FXS, a phenomenon that could be developed as a biomarker end point for improving treatment trial evaluation in girls with this condition.

A short humorous intervention protects against subsequent psychological stress and attenuates cortisol levels without affecting attention

Presentation of humor simultaneously with a stressful event has been shown to dampen the psychological and physiological responses of stress. However, whether a relatively short humorous intervention can be utilized to prevent the subsequent stress processing is still underinvestigated. Furthermore, it is unknown, whether such a humor intervention changes stress processing at a cost of cognitive functioning. According to the broaden-and-build theory inducing positive emotions may subsequently impact cognitive performance. Here, we investigated whether humor protects against subsequent stressors by attenuating both, psychological and physiological stress levels and whether this affects cognitive performance. Participants watched either a humorous or a neutral movie, underwent stress induction and performed in a visual search task. Compared to the control group, psychological stress levels and salivary cortisol levels were lower in the humor group, yet no differences were found in response times and accuracy rates for the visual search task. Our results demonstrate that a short humorous intervention shields against subsequent psychological stress leaving cognitive performance intact, thus making it highly applicable to improve mental and physical health in everyday life situations.

Exploring how harming and helping behaviors drive prediction and explanation during anthropomorphism

Cacioppo and colleagues advanced the study of anthropomorphism by positing three motives that moderated the occurrence of this phenomenon; belonging, effectance, and explanation. Here, we further this literature by exploring the extent to which the valence of a target's behavior influences its anthropomorphism when perceivers attempt to explain and predict that target's behavior, and the involvement of brain regions associated with explanation and prediction in such anthropomorphism. Participants viewed videos of varying visually complex agents - geometric shapes, computer generated (CG) faces, and greebles - in nonrandom motion performing harming and helping behaviors. Across two studies, participants reported a narrative that explained the observed behavior (both studies) while we recorded brain activity (study one), and participants predicted future behavior of the protagonist shapes (study two). Brain regions implicated in prediction error (striatum), not language generation (inferior frontal gyrus; IFG) engaged more to harming than helping behaviors during the anthropomorphism of such stimuli. Behaviorally, we found greater anthropomorphism in explanations of harming rather than helping behaviors, but the opposite pattern when participants predicted the agents' behavior. Together, these studies build upon the anthropomorphism literature by exploring how the valence of behavior drives explanation and prediction.

Hemispheric Organization for Visual Object Recognition: A Theoretical Account and Empirical Evidence

Despite the similarity in structure, the hemispheres of the human brain have somewhat different functions. A traditional view of hemispheric organization asserts that there are independent and largely lateralized domain-specific regions in ventral occipitotemporal (VOTC), specialized for the recognition of distinct classes of objects. Here, we offer an alternative account of the organization of the hemispheres, with a specific focus on face and word recognition. This alternative account relies on three computational principles: distributed representations and knowledge, cooperation and competition between representations, and topography and proximity. The crux is that visual recognition results from a network of regions with graded functional specialization that is distributed across both hemispheres. Specifically, the claim is that face recognition, which is acquired relatively early in life, is processed by VOTC regions in both hemispheres. Once literacy is acquired, word recognition, which is co-lateralized with language areas, primarily engages the left VOTC and, consequently, face recognition is primarily, albeit not exclusively, mediated by the right VOTC. We review psychological and neural evidence from a range of studies conducted with normal and brain-damaged adults and children and consider findings which challenge this account. Last, we offer suggestions for future investigations whose findings may further refine this account.

Unsupervised visual discrimination learning of complex stimuli: Accuracy, bias and generalization

Through same-different judgements, we can discriminate an immense variety of stimuli and consequently, they are critical in our everyday interaction with the environment. The quality of the judgements depends on familiarity with stimuli. A way to improve the discrimination is through learning, but to this day, we lack direct evidence of how learning shapes the same-different judgments with complex stimuli. We studied unsupervised visual discrimination learning in 42 participants, as they performed same-different judgments with two types of unfamiliar complex stimuli in the absence of labeling or individuation. Across nine daily training sessions with equiprobable same and different stimuli pairs, participants increased the sensitivity and the criterion by reducing the errors with both same and different pairs. With practice, there was a superior performance for different pairs and a bias for different response. To evaluate the process underlying this bias, we manipulated the proportion of same and different pairs, which resulted in an additional proportion-induced bias, suggesting that the bias observed with equal proportions was a stimulus processing bias. Overall, these results suggest that unsupervised discrimination learning occurs through changes in the stimulus processing that increase the sensory evidence and/or the precision of the working memory. Finally, the acquired discrimination ability was fully transferred to novel exemplars of the practiced stimuli category, in agreement with the acquisition of a category specific perceptual expertise.

Congenital prosopagnosia without object agnosia? A literature review

A longstanding controversy concerns the functional organization of high-level vision, and the extent to which the recognition of different classes of visual stimuli engages a single system or multiple independent systems. We examine this in the context of congenital prosopagnosia (CP), a neurodevelopmental disorder in which individuals, without a history of brain damage, are impaired at face recognition. This paper reviews all CP cases from 1976 to 2016, and explores the evidence for the association or dissociation of face and object recognition. Of the 238 CP cases with data permitting a satisfactory evaluation, 80.3% evinced an association between impaired face and object recognition whereas 19.7% evinced a dissociation. We evaluate the strength of the evidence and correlate the face and object recognition behaviour. We consider the implications for theories of functional organization of the visual system, and offer suggestions for further adjudication of the relationship between face and object recognition.

Neural evidence for the subliminal processing of facial trustworthiness in infancy

Face evaluation is thought to play a vital role in human social interactions. One prominent aspect is the evaluation of facial signs of trustworthiness, which has been shown to occur reliably, rapidly, and without conscious awareness in adults. Recent developmental work indicates that the sensitivity to facial trustworthiness has early ontogenetic origins as it can already be observed in infancy. However, it is unclear whether infants' sensitivity to facial signs of trustworthiness relies upon conscious processing of a face or, similar to adults, occurs also in response to subliminal faces. To investigate this question, we conducted an event-related brain potential (ERP) study, in which we presented 7-month-old infants with faces varying in trustworthiness. Facial stimuli were presented subliminally (below infants' face visibility threshold) for only 50ms and then masked by presenting a scrambled face image. Our data revealed that infants' ERP responses to subliminally presented faces differed as a function of trustworthiness. Specifically, untrustworthy faces elicited an enhanced negative slow wave (800-1000ms) at frontal and central electrodes. The current findings critically extend prior work by showing that, similar to adults, infants' neural detection of facial signs of trustworthiness occurs also in response to subliminal face. This supports the view that detecting facial trustworthiness is an early developing and automatic process in humans.

Comparing Cross-Sections and 3D Renderings for Surface Matching Tasks Using Physical Ground Truths

Within the visualization community there are some well-known techniques for visualizing 3D spatial data and some general assumptions about how perception affects the performance of these techniques in practice. However, there is a lack of empirical research backing up the possible performance differences among the basic techniques for general tasks. One such assumption is that 3D renderings are better for obtaining an overview, whereas cross sectional visualizations such as the commonly used Multi-Planar Reformation (MPR) are better for supporting detailed analysis tasks. In the present study we investigated this common assumption by examining the difference in performance between MPR and 3D rendering for correctly identifying a known surface. We also examined whether prior experience working with image data affects the participant's performance, and whether there was any difference between interactive or static versions of the visualizations. Answering this question is important because it can be used as part of a scientific and empirical basis for determining when to use which of the two techniques. An advantage of the present study compared to other studies is that several factors were taken into account to compare the two techniques. The problem was examined through an experiment with 45 participants, where physical objects were used as the known surface (ground truth). Our findings showed that: 1. The 3D renderings largely outperformed the cross sections; 2. Interactive visualizations were partially more effective than static visualizations; and 3. The high experience group did not generally outperform the low experience group.

The DalHouses: 100 new photographs of houses with ratings of typicality, familiarity, and degree of similarity to faces

Houses have often been used as comparison stimuli in face-processing studies because of the many attributes they share with faces (e.g., distinct members of a basic category, consistent internal features, mono-orientation, and relative familiarity). Despite this, no large, well-controlled databases of photographs of houses that have been developed for research use currently exist. To address this gap, we photographed 100 houses and carefully edited these images. We then asked 41 undergraduate students (18 to 31 years of age) to rate each house on three dimensions: typicality, likeability, and face-likeness. The ratings had a high degree of face validity, and analyses revealed a significant positive correlation between typicality and likeability. We anticipate that this stimulus set (i.e., the DalHouses) and the associated ratings will prove useful to face-processing researchers by minimizing the effort required to acquire stimuli and allowing for easier replication and extension of studies. The photographs of all 100 houses and their ratings data can be obtained at http://dx.doi.org/10.6084/m9.figshare.1279430.

Normal acquisition of expertise with greebles in two cases of acquired prosopagnosia

Face recognition is generally thought to rely on different neurocognitive mechanisms than most types of objects, but the specificity of these mechanisms is debated. One account suggests the mechanisms are specific to upright faces, whereas the expertise view proposes the mechanisms operate on objects of high within-class similarity with which an observer has become proficient at rapid individuation. Much of the evidence cited in support of the expertise view comes from laboratory-based training experiments involving computer-generated objects called greebles that are designed to place face-like demands on recognition mechanisms. A fundamental prediction of the expertise hypothesis is that recognition deficits with faces will be accompanied by deficits with objects of expertise. Here we present two cases of acquired prosopagnosia, Herschel and Florence, who violate this prediction: Both show normal performance in a standard greeble training procedure, along with severe deficits on a matched face training procedure. Herschel and Florence also meet several response time criteria that advocates of the expertise view suggest signal successful acquisition of greeble expertise. Furthermore, Herschel's results show that greeble learning can occur without normal functioning of the right fusiform face area, an area proposed to mediate greeble expertise. The marked dissociation between face and greeble expertise undermines greeble-based claims challenging face-specificity and indicates face recognition mechanisms are not necessary for object recognition after laboratory-based training.

Development of face discrimination abilities, and relationship to magnocellular pathway development, between childhood and adulthood

The current study tested the development of face and object processing in young children (mean age = 5.24 years), adolescents (mean age = 15.8 years), and adults (mean age = 21.1 years) using stimuli that were equated for low-level visual characteristics (luminance, contrast, and spatial frequency make-up) and methods that equate for difficulty across ages. We also tested sensitivity to luminance and chromatic contrast (i.e., thought to be mediated primarily by the subcortical Magnocellular (M) and Parvocellular (P) pathways, respectively) to determine whether age-related improvements in face or object discrimination were driven by age-related changes in the M and/or P pathways. Results showed a selective age-related improvement in face sensitivity and a relationship between age-related increases in face sensitivity and luminance contrast sensitivity. These results add to the mounting evidence that the M pathway may influence face processing.

The influence of stimulus material on attention and performance in the visual expectation paradigm

This longitudinal study examined the influence of stimulus material on attention and expectation learning in the visual expectation paradigm. Female faces were used as attention-attracting stimuli, and non-meaningful visual stimuli of comparable complexity (Greebles) were used as low attention-attracting stimuli. Expectation learning performance was operationalized using the average reaction time and number of anticipations. For the measurement of attention, the percentage of trials with on-task attention behavior was calculated. To analyze attention and differences in performance, a total of 108 German infants (3–6 months of age) were assessed. Significant differences were found between the two types of stimuli concerning the infants’ rate of attention and anticipations. The results indicate learning material to influence attentional processes and expectation learning.

Activation of Fusiform Face Area by Greebles Is Related to Face Similarity but Not Expertise

Some of the brain areas in the ventral temporal lobe, such as the fusiform face area (FFA), are critical for face perception in humans, but what determines this specialization is a matter of debate. The face specificity hypothesis claims that faces are processed in a domain-specific way. Alternatively, the expertise hypothesis states that the FFA is specialized in processing objects of expertise. To disentangle these views, some previous experiments used an artificial class of novel objects called Greebles. These experiments combined a learning and fMRI paradigm. Given the high impact of the results in the literature, we replicated and further investigated this paradigm. In our experiment, eight participants were trained for ten 1-hr sessions at identifying Greebles. We scanned participants before and after training and examined responses in FFA and lateral occipital complex. Most importantly and in contrast to previous reports, we found a neural inversion effect for Greebles before training. This result suggests that people process the “novel” Greebles as faces, even before training. This prediction was confirmed in a postexperimental debriefing. In addition, we did not find an increase of the inversion effect for Greebles in the FFA after training. This indicates that the activity in the FFA for Greebles does not depend on the degree of expertise acquired with the objects but on the interpretation of the stimuli as face-related.

Recognition of faces and Greebles in 3-month-old infants: Influence of temperament and cognitive abilities

The aim of the present study was to investigate whether temperament and cognitive abilities are related to recognition performance of Caucasian and African faces and of a nonfacial stimulus class, Greebles. Seventy Caucasian infants were tested at 3 months with a habituation/dishabituation paradigm and their temperament and cognitive abilities were measured. Analyses revealed that only infants with easy temperament recognized familiar Greebles from the habituation phase. A similar pattern was found for cognitive abilities showing that only infants with higher cognitive abilities recognized Greebles. Irrespectively of temperament and cognitive abilities, all infants recognized the faces. Thus, the data suggest that recognition of unfamiliar Greebles, but not of faces, is demanding for 3-month-old infants with difficult temperament or lower cognitive abilities.

The neural bases of prosopagnosia and pure alexia: recent insights from functional neuroimaging

PURPOSE OF REVIEW

To discuss whether recent functional neuroimaging results can account for clinical phenomenology in visual associative agnosias.

RECENT FINDINGS

Functional neuroimaging studies in healthy human subjects have identified only two regions of ventral occipitotemporal cortex that invariantly respond to individual faces and visual words, respectively. The signature of face identity coding in the fusiform neural response was shown to be missing in a patient with prosopagnosia. Another case study established that a surgical lesion close to the region sensitive to visual words can result in pure alexia.

SUMMARY

Evidence is increasing that functional specialization for processing face identity and visual word forms is restricted to two specialized sensory modules in the occipitotemporal cortex. A structural or functional lesion to face-sensitive and word-sensitive regions in the ventral occipitotemporal cortex can provide the most parsimonious account for the clinical syndromes of prosopagnosia and agnosic alexia. This review suggests that functional specialization should be considered in terms of whether exclusively one brain region (instead of many) underpins a defined function and not as whether this brain region underpins exclusively one cognitive function. Such functional specialization seems to exist for at least two higher-order visual perceptual functions, face and word identification.

Perceptual Expertise Effects Are Not All or None: Spatially Limited Perceptual Expertise for Faces in a Case of Prosopagnosia

We document a seemingly unique case of severe prosopagnosia, L. R., who suffered damage to his anterior and inferior right temporal lobe as a result of a motor vehicle accident. We systematically investigated each of three factors associated with expert face recognition: fine-level discrimination, holistic processing, and configural processing (Experiments 1-3). Surprisingly, L. R. shows preservation of all three of these processes; that is, his performance in these experiments is comparable to that of normal controls. However, L. R. is only able to apply these processes over a limited spatial extent to the fine-level detail within faces. Thus, when the location of a given change is unpredictable (Experiment 3), L. R. exhibits normal detection of features and spatial configurations only for the lower half of each face. Similarly, when required to divide his attention over multiple face features, L. R. is able to determine the identity of only a single feature (Experiment 4). We discuss these results in the context of forming a better understanding of prosopagnosia and the mechanisms used in face recognition and visual expertise. We conclude that these mechanisms are not “all-or-none”, but rather can be impaired incrementally, such that they may remain functional over a restricted spatial area. This conclusion is consistent with previous research suggesting that perceptual expertise is acquired in a spatially incremental manner [Gauthier, I., & Tarr, M. J. Unraveling mechanisms for expert object recognition: Bridging brain activity and behavior. Journal of Experimental Psychology: Human Perception & Performance, 28, 431-446, 2002].

Detailed Exploration of Face-related Processing in Congenital Prosopagnosia: 1. Behavioral Findings

We show that five individuals with congenital prosopagnosia (CP) are impaired at face recognition and discrimination and do not exhibit the normal superiority for upright over inverted faces despite intact visual acuity, low-level vision and intelligence, and in the absence of any obvious neural concomitant. Interestingly, the deficit is not limited to faces: The CP individuals were also impaired at discriminating common objects and novel objects although to a lesser extent than discriminating faces. The perceptual deficit may be attributable to a more fundamental visual processing disorder; the CP individuals exhibited difficulty in deriving global configurations from simple visual stimuli, even with extended exposure duration and considerable perceptual support in the image. Deriving a global configuration from local components is more critical for faces than for other objects, perhaps accounting for the exaggerated deficit in face processing. These findings elucidate the psychological mechanisms underlying CP and support the link between configural and face processing.

Behavioral change and its neural correlates in visual agnosia after expertise training

Agnosia, the impairment in object and face recognition despite intact vision and intelligence, is one of the most intriguing and debilitating neuropsychological deficits. The goal of this study was to determine whether S.M., an individual with longstanding visual agnosia and concomitant prosopagnosia, can be retrained to perform visual object recognition and, if so, what neural substrates mediate this reacquisition. Additionally, of interest is the extent to which training on one type of visual stimulus generalizes to other visual stimuli, as this informs our understanding of the organization of ventral visual cortex. Greebles were chosen as the stimuli for retraining given that, in neurologically normal individuals, these stimuli can engage the fusiform face area. Posttraining, S.M. showed significant improvement in recognizing Greebles, although he did not attain normal levels of performance. He was also able to recognize untrained Greebles and showed improvement in recognizing common objects. Surprisingly, his performance on face recognition, albeit poor initially, was even more impaired following training. A comparison of pre- and postintervention functional neuroimaging data mirrored the behavioral findings: Face-selective voxels in the fusiform gyrus prior to training were no longer so and were, in fact, more Greeble-selective. The findings indicate potential for experience-dependent dynamic reorganization in agnosia with the possibility that residual neural tissue, with limited capacity, will compete for representations.