A new approach to the diagnosis of deficits in processing faces: Potential application in autism research

Multiple-stage impairments of unfamiliar face learning in developmental prosopagnosia: Evidence from fMRI repetition suppression and multi-voxel pattern stability

Individuals with developmental prosopagnosia (DP) are characterized by severe face recognition deficits, yet it remains unknown how they are hindered in the process of unfamiliar face learning. Here we tracked the changes of neural activation during unfamiliar face repetition in DP with fMRI to reveal their neural deficits in learning unfamiliar faces. At the perceptual level, we found that the bilateral fusiform face area (FFA) in individuals with DP showed attenuated repetition suppression for faces, suggesting an inefficient perceptual analysis for learned faces. At the mnemonic level, individuals with DP showed decreased multi-voxel pattern stability for repeated faces in bilateral medial temporal lobe (MTL), suggesting an unstable mnemonic representation for learned faces. In addition, resting-state functional connectivity between the FFA and MTL was also disrupted in individuals with DP. Finally, the MTL's unstable mnemonic representation was associated with the impaired face recognition performance in DP. In sum, our study provides evidence that individuals with DP showed multi-stage neural deficits in unfamiliar face learning and sheds new light on how unfamiliar faces are learned in normal population.

Separate and Shared Neural Basis of Face Memory and Face Perception in Developmental Prosopagnosia

Developmental prosopagnosia (DP), also known as face blindness, is a cognitive disorder with a severe deficit in recognizing faces. However, the heterogeneous nature of DP leads to a longstanding debate on which stages the deficit occurs, face perception (e.g., matching two consecutively presented faces) or face memory (e.g., matching a face to memorized faces). Here, we used the individual difference approach with functional magnetic resonance imaging to explore the neural substrates of DPs' face perception and face memory that may illuminate DPs' heterogeneity. Specifically, we measured the behavioral performance of face perception and face memory in a large sample of individuals suffering DP (N = 64) and then associated the behavioral performance with their face-selective neural responses in the core face network (CFN) and the extended face network (EFN), respectively. Behaviorally, we found that DP individuals were impaired in both face perception and face memory; however, there was only a weak correlation between the performances of two tasks. Consistent with this observation, the neural correlate of DPs' performance in face memory task was localized in the bilateral fusiform face area, whereas DPs' performance in face perception task was correlated with the face selectivity in the right posterior superior temporal sulcus, suggesting that the neural substrates in the CFN for face memory and face perception were separate in DP. In contrast, shared neural substrates of deficits in face perception and face memory tasks were identified in the EFN, including the right precuneus and the right orbitofrontal cortex. In summary, our study provides one of the first empirical evidence that the separate and shared neural substrates of face perception and face memory were identified in the CFN and EFN, respectively, which may help illuminating DP's heterogeneous nature.

The neural network for face recognition: Insights from an fMRI study on developmental prosopagnosia

Face recognition is supported by collaborative work of multiple face-responsive regions in the brain. Based on findings from individuals with normal face recognition ability, a neural model has been proposed with the occipital face area (OFA), fusiform face area (FFA), and face-selective posterior superior temporal sulcus (pSTS) as the core face network (CFN) and the rest of the face-responsive regions as the extended face network (EFN). However, little is known about how these regions work collaboratively for face recognition in our daily life. Here we focused on individuals suffering developmental prosopagnosia (DP), a neurodevelopmental disorder specifically impairing face recognition, to shed light on the infrastructure of the neural model of face recognition. Specifically, we used a variant of global brain connectivity method to comprehensively explore resting-state functional connectivity (FC) among face-responsive regions in a large sample of DPs (N = 64). We found that both the FCs within the CFN and those between the CFN and EFN were largely reduced in DP. Importantly, the right OFA and FFA served as the dysconnectivity hubs within the CFN, i.e., FCs concerning these two regions within the CFN were largely disrupted. In addition, DPs' right FFA also showed reduced FCs with the EFN. Moreover, these disrupted FCs were related to DP's behavioral deficit in face recognition, with the FCs from the FFA to the anterior temporal lobe (ATL) and pSTS the most predictive. Based on these findings, we proposed a revised neural model of face recognition demonstrating the relatedness of interactions among face-responsive regions to face recognition.

Dissociated neural basis of two behavioral hallmarks of holistic face processing: The whole-part effect and composite-face effect

It has been long proposed that our extraordinary face recognition ability stems from holistic face processing. Two widely-used behavioral hallmarks of holistic face processing are the whole-part effect (WPE) and composite-face effect (CFE). However, it remains unknown whether these two effects reflect similar or different aspects of holistic face processing. Here we investigated this question by examining whether the WPE and CFE involved shared or distinct neural substrates in a large sample of participants (N=200). We found that the WPE and CFE showed hemispheric dissociation in the fusiform face area (FFA), that is, the WPE was correlated with face selectivity in the left FFA, while the CFE was correlated with face selectivity in the right FFA. Further, the correlation between the WPE and face selectivity was largely driven by the FFA response to faces, whereas the association between the CFE and face selectivity resulted from suppressed response to objects in the right FFA. Finally, we also observed dissociated correlation patterns of the WPE and CFE in other face-selective regions and across the whole brain. These results suggest that the WPE and CFE may reflect different aspects of holistic face processing, which shed new light on the behavioral dissociations of these two effects demonstrated in literature.

Visual Attention Processes and Oculomotor Control in Autism Spectrum Disorder: A Brief Review and Future Directions

Autism spectrum disorder (ASD) is defined as persistent deficits in social communication and social interaction, and restricted, repetitive patterns of behavior, interests or activities Diagnostic and Statistical Manual of Mental Disorders (5th ed., DSM-5; American Psychiatric Association, 2013). However, individuals with ASD show clearly atypical visual patterns. So far, indications of abnormal visual attention and oculomotor control concerning stimuli independent of social function in ASD have been found. The same findings have been shown in individuals suffering of other neurodevelopmental disorders (e.g., developmental coordination disorder and developmental dyslexia [DD]). Furthermore, visual attention processes and oculomotor control are supposed to be subserved by the magnocellular visual system, which has been found, in turn, to be dysfunctional in ASD and other neurodevelopmental disabilities (i.e., DD). The purpose of this article is to briefly review the link between oculomotor control and visual attention processes and ASD, and to discuss the specificity and overlap of eye movement findings between ASD and other neurodevelopmental disorders.

Altered spontaneous neural activity in the occipital face area reflects behavioral deficits in developmental prosopagnosia

Individuals with developmental prosopagnosia (DP) exhibit severe difficulties in recognizing faces and to a lesser extent, also exhibit difficulties in recognizing non-face objects. We used fMRI to investigate whether these behavioral deficits could be accounted for by altered spontaneous neural activity. Two aspects of spontaneous neural activity were measured: the intensity of neural activity in a voxel indexed by the fractional amplitude of spontaneous low-frequency fluctuations (fALFF), and the connectivity of a voxel to neighboring voxels indexed by regional homogeneity (ReHo). Compared with normal adults, both the fALFF and ReHo values within the right occipital face area (rOFA) were significantly reduced in DP subjects. Follow-up studies on the normal adults revealed that these two measures indicated further functional division of labor within the rOFA. The fALFF in the rOFA was positively correlated with behavioral performance in recognition of non-face objects, whereas ReHo in the rOFA was positively correlated with processing of faces. When considered together, the altered fALFF and ReHo within the same region (rOFA) may account for the comorbid deficits in both face and object recognition in DPs, whereas the functional division of labor in these two measures helps to explain the relative independency of deficits in face recognition and object recognition in DP.