Michal Tanzer

Impaired holistic processing in congenital prosopagnosia

It has long been argued that face processing requires disproportionate reliance on holistic or configural processing, relative to that required for non-face object recognition, and that a disruption of such holistic processing may be causally implicated in prosopagnosia. Previously, we demonstrated that individuals with congenital prosopagnosia (CP) did not show the normal face inversion effect (better performance for upright compared to inverted faces) and evinced a local (rather than the normal global) bias in a compound letter global/local (GL) task, supporting the claim of disrupted holistic processing in prosopagnosia. Here, we investigate further the nature of holistic processing impairments in CP, first by confirming, in a large sample of CP individuals, the absence of the normal face inversion effect and the presence of the local bias on the GL task, and, second, by employing the composite face paradigm, often regarded as the gold standard for measuring holistic face processing. In this last task, we show that, in contrast with controls, the CP group perform equivalently with aligned and misaligned faces and was impervious to (the normal) interference from the task-irrelevant bottom part of faces. Interestingly, the extent of the local bias evident in the composite task is correlated with the abnormality of performance on diagnostic face processing tasks. Furthermore, there is a significant correlation between the magnitude of the local bias in the GL and performance on the composite task. These results provide further evidence for impaired holistic processing in CP and, moreover, corroborate the critical role of this type of processing for intact face recognition.

A Double Dissociation Between Action and Perception in the Context of Visual Illusions Opposite Effects of Real and Illusory Size

The idea that there are two distinct cortical visual pathways, a dorsal action stream and a ventral perception stream, is supported by neuroimaging and neuropsychological evidence. Yet there is an ongoing debate as to whether or not the action system is resistant to pictorial illusions in healthy participants. In the present study, we disentangled the effects of real and illusory object size on action and perception by pitting real size against illusory size. In our task, two objects that differed slightly in length were placed within a version of the Ponzo illusion. Even though participants erroneously perceived the physically longer object as the shorter one (or vice versa), their grasping was remarkably tuned to the real size difference between the objects. These results provide the first demonstration of a double dissociation between action and perception in the context of visual illusions and together with previous findings converge on the idea that visually guided action and visual perception make use of different metrics and frames of reference.

Response: When does grasping escape Weber's law?

Summary In a recent study [1], we found that Webers law, a fundamental principle of perception, does not govern visual control of grasping and concluded that different representations of object size are used for action and for perception [1]. Smeets and Brenner [2] suggest instead that grasping is computed on the basis of position rather than on the basis of size, and that this accounts for the apparent absence of Webers law. However, their alternative explanation cannot readily account for memory-based grasping, which does obey Webers law. In this response, we present additional data to show that, even when memory-based and real-time grasping both are executed without visual feedback, only the former obeys Webers law. This dissociation further supports the conclusion that action and perception are sustained by qualitatively different computations.

General holistic impairment in congenital prosopagnosia: Evidence from Garner's speeded-classification task

Congenital prosopagnosia (CP), a lifelong impairment in face processing in the absence of brain damage, is often ascribed to impairment in holistic processing. It is still debated whether such difficulties are restricted to faces or whether they can also be observed for nonfacial stimuli. Here, we investigate this issue by examining CP individuals and their controls on two variations of the Garner speeded classification task tailored to assess holistic processing of nonfacial stimuli. In Experiment 1, participants were asked to judge the width of visually presented rectangles while ignoring their irrelevant height, or to judge changes in width while height remained constant. Critically, while controls exhibited the expected Garner interference, no such interference was observed for the CPs, indicating impaired holistic processing of integral, nonfacial shape dimensions. Experiment 2, utilized the same Garner paradigm, but here participants were asked to judge integral dimensions that are unrelated to shape (colour). Importantly, both CPs and controls exhibited the same level of Garner interference, indicating intact integral processing of colour dimensions. This dissociation between the performance on the two Garner tasks indicates that CPs do not exhibit a general local processing bias or impaired integration of any perceptual dimensions, but rather a deficit that is restricted to tasks requiring holistic integral perception of shape dimensions. Taken together, these results provide evidence for the existence of a general impairment in holistic shape perception in CP, which may be related to the mechanisms underlying this disorder.

Altered topology of neural circuits in congenital prosopagnosia

Using a novel, fMRI-based inter-subject functional correlation (ISFC) approach, which isolates stimulus-locked inter-regional correlation patterns, we compared the cortical topology of the neural circuit for face processing in participants with an impairment in face recognition, congenital prosopagnosia (CP), and matched controls. Whereas the anterior temporal lobe served as the major network hub for face processing in controls, this was not the case for the CPs. Instead, this group evinced hyper-connectivity in posterior regions of the visual cortex, mostly associated with the lateral occipital and the inferior temporal cortices. Moreover, the extent of this hyper-connectivity was correlated with the face recognition deficit. These results offer new insights into the perturbed cortical topology in CP, which may serve as the underlying neural basis of the behavioral deficits typical of this disorder. The approach adopted here has the potential to uncover altered topologies in other neurodevelopmental disorders, as well. DOI: http://dx.doi.org/10.7554/eLife.25069.001

Does social support protect against recognition of angry facial expressions following failure

Herein we examined the ability of perceived social support to modulate the recognition of facial expressions. Specifically, we hypothesised that perceived social support would serve as a “protective lens”, biasing individuals against recognition of angry faces and towards recognizing happy ones. Experimentally inducing failure and success in a performance task, we examined both main and interactive effects of perceived social support. Under experimentally induced failure, perceived social support was negatively associated with recognizing angry emotional face expression. Interestingly, we also found a trend toward a positive association between perceived social support and recognition of happy facial expression, irrespective of the failure/success experimental manipulation. These findings elucidate a potential link between social/personality and cognitive processes underlying the perception of emotional facial expression.

Project PAVE (Personality And Vision Experimentation): role of personal and interpersonal resilience in the perception of emotional facial expression.

The aim of the proposed theoretical model is to illuminate personal and interpersonal resilience by drawing from the field of emotional face perception. We suggest that perception/recognition of emotional facial expressions serves as a central link between subjective, self-related processes and the social context. Emotional face perception constitutes a salient social cue underlying interpersonal communication and behavior. Because problems in communication and interpersonal behavior underlie most, if not all, forms of psychopathology, it follows that perception/recognition of emotional facial expressions impacts psychopathology. The ability to accurately interpret one’s facial expression is crucial in subsequently deciding on an appropriate course of action. However, perception in general, and of emotional facial expressions in particular, is highly influenced by individuals’ personality and the self-concept. Herein we briefly outline well-established theories of personal and interpersonal resilience and link them to the neuro-cognitive basis of face perception. We then describe the findings of our ongoing program of research linking two well-established resilience factors, general self-efficacy (GSE) and perceived social support (PSS), with face perception. We conclude by pointing out avenues for future research focusing on possible genetic markers and patterns of brain connectivity associated with the proposed model. Implications of our integrative model to psychotherapy are discussed.