Face processing without awareness in the right fusiform gyrus

Exploring the spatial interference effects elicited by social and non-social targets: A conditional accuracy function approach

Recent studies employing the spatial interference paradigm reveal qualitative differences in congruency effects between gaze and arrow targets. Typically, arrows produce a standard congruency effect (SCE), with faster responses when target direction aligns with its location. Conversely, gaze targets often lead to a reversed congruency effect (RCE), where responses are slower in similar conditions. We explored this dissociation using the Conditional Accuracy Function (CAF) to assess accuracy across reaction time bins. Using a hierarchical linear mixed modelling approach to compare cropped eyes, and full faces as social stimuli, and arrows as non-social stimuli, we synthesized findings from 11 studies, which led to three distinct models. The results showed that with non-social targets, incongruent trials exhibited lower accuracy rates in the first bin than in subsequent bins, while congruent trials maintained stable accuracy throughout the distribution. Conversely, social targets revealed a dissociation within the fastest responses; alongside a general reduction in accuracy for both congruency conditions, congruent trials resulted in even lower accuracy rates than incongruent ones. These results suggest with gaze targets that additional information, perhaps social, in addition to the automatic capture by the irrelevant target location, is being processed during the earlier stages of processing.

Impairment of unconscious emotional processing after unilateral medial temporal structure resection

The role of the amygdala in unconscious emotional processing remains a topic of debate. Past lesion studies have indicated that amygdala damage leads to impaired electrodermal activity in response to subliminally presented emotional stimuli. However, electrodermal activity can reflect both emotional and nonemotional processes. To provide behavioral evidence highlighting the critical role of the amygdala in unconscious emotional processing, we examined patients (n = 16) who had undergone unilateral resection of medial temporal lobe structures, including the amygdala. We utilized the subliminal affective priming paradigm in conjunction with unilateral visual presentation. Fearful or happy dynamic facial expressions were presented in unilateral visual fields for 30 ms, serving as negative or positive primes. Subsequently, neutral target faces were displayed, and participants were tasked with rating the valence of these targets. Positive primes, compared to negative ones, enhanced valence ratings of the target to a greater extent when they stimulated the intact hemisphere (i.e., were presented in the contralateral visual field of the intact hemisphere) than when they stimulated the resected hemisphere (i.e., were presented in the contralateral visual field of the resected hemisphere). These results suggest that the amygdala is causally involved in unconscious emotional processing.

Self-Face Activates the Dopamine Reward Pathway without Awareness

The self-face advantage has been demonstrated not only at the supraliminal level, but also at the subliminal level. However, it remains unclear whether subliminal self-face processing involves the same neural networks as those for supraliminal self-face processing. Here, we show that the ventral tegmental area, a center of the dopamine reward pathway, exhibited greater activation to subliminal presentations of the self-face than those of the others’ faces, whereas subliminal presentations of the others’ faces induced activation in the amygdala, which generally responds to unfamiliar information. This self-other difference in brain response was consistently observed even when the facial configuration was modified without changing the shape of the facial parts. The present findings suggest that the dopamine reward pathway is involved in automatic self-advantage in face processing, and the subliminal self-other facial discrimination does not depend on information of the precise facial configuration.

The neural correlates of moral comparison

Moral comparison supports the moral judgment that then evaluates social behaviors and restrains social interactions. However, previous studies have not investigated what neural networks support the process of moral comparison. The present study examined neural networks of moral and physical size comparisons using a distance paradigm and functional magnetic resonance imaging. In the experiment, participants judged which picture/sentence presented a more moral scenario in the moral comparison run or which picture/sentence had a larger physical size in the physical comparison run. Results demonstrated that both moral and physical comparisons induced a distance effect-participants' responses were faster for high than low distance comparisons. Moreover, moral and physical comparisons recruited similar neural networks, including the bilateral dorsomedial prefrontal cortex, bilateral intraparietal sulcus, and bilateral insula. Interestingly, compared with physical size comparisons, moral comparisons elicited stronger activity in the bilateral precuneus, bilateral angular gyrus, and bilateral superior frontal gyrus. Meanwhile, compared with moral comparisons, physical size comparisons elicited stronger activity in the right inferior parietal lobule. Together, these results suggest that the neural substrates of moral and physical comparisons not only share the frontoparietal network but also rely on specific neural underpinnings, depending on the specific comparison recruited.

The effect of cannabidiol (CBD) on low-frequency activity and functional connectivity in the brain of adults with and without autism spectrum disorder (ASD)

BACKGROUND

The potential benefits of cannabis and its major non-intoxicating component cannabidiol (CBD) are attracting attention, including as a potential treatment in neurodevelopmental disorders such as autism spectrum disorder (ASD). However, the neural action of CBD, and its relevance to ASD, remains unclear. We and others have previously shown that response to drug challenge can be measured using functional magnetic resonance imaging (fMRI), but that pharmacological responsivity is atypical in ASD.

AIMS

We hypothesized that there would be a (different) fMRI response to CBD in ASD.

METHODS

To test this, task-free fMRI was acquired in 34 healthy men (half with ASD) following oral administration of 600 mg CBD or matched placebo (random order; double-blind administration). The 'fractional amplitude of low-frequency fluctuations' (fALFF) was measured across the whole brain, and, where CBD significantly altered fALFF, we tested if functional connectivity (FC) of those regions was also affected by CBD.

RESULTS

CBD significantly increased fALFF in the cerebellar vermis and the right fusiform gyrus. However, post-hoc within-group analyses revealed that this effect was primarily driven by the ASD group, with no significant change in controls. Within the ASD group only, CBD also significantly altered vermal FC with several of its subcortical (striatal) and cortical targets, but did not affect fusiform FC with other regions in either group.

CONCLUSION

Our results suggest that, especially in ASD, CBD alters regional fALFF and FC in/between regions consistently implicated in ASD. Future studies should examine if this affects the complex behaviours these regions modulate.

Amygdala activation during unconscious visual processing of food

Hedonic or emotional responses to food have important positive and negative effects on human life. Behavioral studies have shown that hedonic responses to food images are elicited rapidly, even in the absence of conscious awareness of food. Although a number of previous neuroimaging studies investigated neural activity during conscious processing of food images, the neural mechanisms underlying unconscious food processing remain unknown. To investigate this issue, we measured neural activity using functional magnetic resonance imaging while participants viewed food and mosaic images presented subliminally and supraliminally. Conjunction analyses revealed that the bilateral amygdala was more strongly activated in response to food images than to mosaic images under both subliminal and supraliminal conditions. Interaction analyses revealed that the broad bilateral posterior regions, peaking at the posterior fusiform gyrus, were particularly active when participants viewed food versus mosaic images under the supraliminal compared with the subliminal condition. Dynamic causal modeling analyses supported the model in which the subcortical visual pathway from the pulvinar to the amygdala was modulated by food under the subliminal condition; in contrast, the model in which both subcortical and cortical (connecting the primary visual cortex, fusiform gyrus, and the amygdala) visual pathways were modulated by food received the most support under the supraliminal condition. These results suggest the possibility that unconscious hedonic responses to food may exert an effect through amygdala activation via the subcortical visual pathway.

Enhanced Early Visual Responses During Implicit Emotional Faces Processing in Autism Spectrum Disorder

Research on Autism Spectrum Disorder (ASD) has focused on processing of socially-relevant stimuli, such as faces. Nonetheless, before being 'social', faces are visual stimuli. The present magnetoencephalography study investigated the time course of brain activity during an implicit emotional task in visual emotion-related regions in 19 adults with ASD (mean age 26.3 ± 4.4) and 19 typically developed controls (26.4 ± 4). The results confirmed previously-reported differences between groups in brain responses to emotion and a hypo-activation in the ASD group in the right fusiform gyrus around 150 ms. However, the ASD group also presented early enhanced activity in the occipital region. These results support that impaired face processing in ASD might be sustained by atypical responses in primary visual areas.

Why Is 10 Past 10 the Default Setting for Clocks and Watches in Advertisements? A Psychological Experiment

Have you ever noticed that in watch advertisements the time is usually set at 10:10? The reasons and psychological effects of this default time setting are elusive. In Experiment 1, we hypothesized that watches showing a time setting resembling a smiling face (10:10) would enhance emotional valence and intention to buy compared to a neutral time setting (11:30), whereas a time setting resembling a sad face (8:20) would have the opposite effect. Moreover, we investigated a possible interaction effect with the gender of the participants. In Experiment 2, we directly tested the hypotheses that watches set at 10:10 resemble a smiling face, whereas watches set at 8:20 resemble a sad face. The data of the first experiment reveal that watches set at 10:10 showed a significant positive effect on the emotion of the observer and the intention to buy. However, watches set at 8:20 did not show any effect on the emotion or the intention to buy. Moreover, watches set at 10:10 induced in women significantly stronger ratings of pleasure than in men. The data of the second experiment show that participants consistently perceive high resemblance between watches set at 10:10 and a smiling face as well as high resemblance between watches set at 8:20 and a sad face. This study provides for the first time empirical evidence for the notion that using watches with a time setting resembling a smiling face (like 10:10) can positively affect the emotional response of the observers and their evaluation of a seen watch, even though they are not aware of the fact that the shown time setting is inducing this effect. Practical implications of the observed findings and alternative explanations are discussed.

Functional development of the brain's face-processing system

In the first 20 years of life, the human brain undergoes tremendous growth in size, weight, and synaptic connectedness. Over the same time period, a person achieves remarkable transformations in perception, thought, and behavior. One important area of development is face processing ability, or the ability to quickly and accurately extract extensive information about a person's identity, emotional state, attractiveness, intention, and numerous other types of information that are crucial to everyday social interaction and communication. Associating particular brain changes with specific behavioral and intellectual developments has historically been a serious challenge for researchers. Fortunately, modern neuroimaging is dramatically advancing our ability to make associations between morphological and behavioral developments. In this article, we demonstrate how neuroimaging has revolutionized our understanding of the development of face processing ability to show that this essential perceptual and cognitive skill matures consistently yet slowly over the first two decades of life. In this manner, face processing is a model system of many areas of complex cognitive development. WIREs Cogn Sci 2017, 8:e1423. doi: 10.1002/wcs.1423 For further resources related to this article, please visit the WIREs website.

Wanting it Too Much: An Inverse Relation Between Social Motivation and Facial Emotion Recognition in Autism Spectrum Disorder

This study examined social motivation and early-stage face perception as frameworks for understanding impairments in facial emotion recognition (FER) in a well-characterized sample of youth with autism spectrum disorders (ASD). Early-stage face perception (N170 event-related potential latency) was recorded while participants completed a standardized FER task, while social motivation was obtained via parent report. Participants with greater social motivation exhibited poorer FER, while those with shorter N170 latencies exhibited better FER for child angry faces stimuli. Social motivation partially mediated the relationship between a faster N170 and better FER. These effects were all robust to variations in IQ, age, and ASD severity. These findings augur against theories implicating social motivation as uniformly valuable for individuals with ASD, and augment models suggesting a close link between early-stage face perception, social motivation, and FER in this population. Broader implications for models and development of FER in ASD are discussed.

Task relevance differentially shapes ventral visual stream sensitivity to visible and invisible faces

Top-down modulations of the visual cortex can be driven by task relevance. Yet, several accounts propose that the perceptual inferences underlying conscious recognition involve similar top-down modulations of sensory responses. Studying the pure impact of task relevance on sensory responses requires dissociating it from the top-down influences underlying conscious recognition. Here, using visual masking to abolish perceptual consciousness in humans, we report that functional magnetic resonance imaging (fMRI) responses to invisible faces in the fusiform gyrus are enhanced when they are task-relevant, but suppressed when they are task-irrelevant compared to other object categories. Under conscious perceptual conditions, task-related modulations were also present but drastically reduced, with visible faces always eliciting greater activity in the fusiform gyrus compared to other object categories. Thus, task relevance crucially shapes the sensitivity of fusiform regions to face stimuli, leading from enhancement to suppression of neural activity when the top-down influences accruing from conscious recognition are prevented.

Exploring the Neural Representation of Novel Words Learned through Enactment in a Word Recognition Task

Vocabulary learning in a second language is enhanced if learners enrich the learning experience with self-performed iconic gestures. This learning strategy is called enactment. Here we explore how enacted words are functionally represented in the brain and which brain regions contribute to enhance retention. After an enactment training lasting 4 days, participants performed a word recognition task in the functional Magnetic Resonance Imaging (fMRI) scanner. Data analysis suggests the participation of different and partially intertwined networks that are engaged in higher cognitive processes, i.e., enhanced attention and word recognition. Also, an experience-related network seems to map word representation. Besides core language regions, this latter network includes sensory and motor cortices, the basal ganglia, and the cerebellum. On the basis of its complexity and the involvement of the motor system, this sensorimotor network might explain superior retention for enactment.

Consciousness is not necessary for visual feature binding

When visual information enters the brain, it is relayed to different specialized regions, processing features such as shape, color, or motion. And yet, in our conscious experience of a colored, moving shape, all the different features seem to be integrated into one unified percept. Therefore, it has been hypothesized that consciousness and feature binding share an intimate relationship. To study this relationship, we used a paradigm in which the behavioral effects of feature binding can be measured. Using masks, we investigated whether spontaneous binding between the orientation and location of a Gabor patch takes place when the Gabor patch is processed consciously or unconsciously. The results of our study suggest that orientation and location of a visually presented object are automatically integrated, even when subjects are unaware of that object. We conclude that binding and consciousness share a less intimate relationship than previously hypothesized, since consciousness is not a necessary condition for binding to occur.

Greater sensitivity of the cortical face processing system to perceptually-equated face detection

Face detection, the perceptual capacity to identify a visual stimulus as a face before probing deeper into specific attributes (such as its identity or emotion), is essential for social functioning. Despite the importance of this functional capacity, face detection and its underlying brain mechanisms are not well understood. This study evaluated the roles that the cortical face processing system, which is identified largely through studying other aspects of face perception, play in face detection. Specifically, we used functional magnetic resonance imaging (fMRI) to examine the activations of the fusifom face area (FFA), occipital face area (OFA) and superior temporal sulcus (STS) when face detection was isolated from other aspects of face perception and when face detection was perceptually-equated across individual human participants (n=20). During face detection, FFA and OFA were significantly activated, even for stimuli presented at perceptual-threshold levels, whereas STS was not. During tree detection, however, FFA and OFA were responsive only for highly salient (i.e., high contrast) stimuli. Moreover, activation of FFA during face detection predicted a significant portion of the perceptual performance levels that were determined psychophysically for each participant. This pattern of result indicates that FFA and OFA have a greater sensitivity to face detection signals and selectively support the initial process of face vs. non-face object perception.

Facial blindsight

Blindsight denotes unconscious residual visual capacities in the context of an inability to consciously recollect or identify visual information. It has been described for color and shape discrimination, movement or facial emotion recognition. The present study investigates a patient suffering from cortical blindness whilst maintaining select residual abilities in face detection. Our patient presented the capacity to distinguish between jumbled/normal faces, known/unknown faces or famous people's categories although he failed to explicitly recognize or describe them. Conversely, performance was at chance level when asked to categorize non-facial stimuli. Our results provide clinical evidence for the notion that some aspects of facial processing can occur without perceptual awareness, possibly using direct tracts from the thalamus to associative visual cortex, bypassing the primary visual cortex.

Neural mechanisms underlying conscious and unconscious attentional shifts triggered by eye gaze

Behavioral studies have shown that eye gaze triggers attentional shifts both with and without conscious awareness. However, the neural substrates of conscious and unconscious attentional shifts triggered by eye gaze remain unclear. To investigate this issue, we measured brain activity using event-related functional magnetic resonance imaging while participants observed averted or straight eye-gaze cues presented supraliminally or subliminally in the central visual field and then localized a subsequent target in the peripheral visual field. Reaction times for localizing the targets were shorter under both supraliminal and subliminal conditions when eye-gaze cues were directionally congruent with the target locations than when they were directionally neutral. Conjunction analyses revealed that a bilateral cortical network, including the middle temporal gyri, inferior parietal lobules, anterior cingulate cortices, and superior and middle frontal gyri, was activated more in response to averted eyes than to straight eyes under both supraliminal and subliminal conditions. Interaction analyses revealed that the right inferior parietal lobule was specifically active when participants viewed averted eyes relative to straight eyes under the supraliminal condition; the bilateral subcortical regions, including the superior colliculus and amygdala, and the middle temporal and inferior frontal gyri in the right hemisphere were activated in response to averted versus straight eyes under the subliminal condition. These results suggest commonalities and differences in the neural mechanisms underlying conscious and unconscious attentional shifts triggered by eye gaze.

Psychophysical "blinding" methods reveal a functional hierarchy of unconscious visual processing

Numerous non-invasive experimental "blinding" methods exist for suppressing the phenomenal awareness of visual stimuli. Not all of these suppressive methods occur at, and thus index, the same level of unconscious visual processing. This suggests that a functional hierarchy of unconscious visual processing can in principle be established. The empirical results of extant studies that have used a number of different methods and additional reasonable theoretical considerations suggest the following tentative hierarchy. At the highest levels in this hierarchy is unconscious processing indexed by object-substitution masking. The functional levels indexed by crowding, the attentional blink (and other attentional blinding methods), backward pattern masking, metacontrast masking, continuous flash suppression, sandwich masking, and single-flash interocular suppression, fall at progressively lower levels, while unconscious processing at the lowest levels is indexed by eye-based binocular-rivalry suppression. Although unconscious processing levels indexed by additional blinding methods is yet to be determined, a tentative placement at lower levels in the hierarchy is also given for unconscious processing indexed by Troxler fading and adaptation-induced blindness, and at higher levels in the hierarchy indexed by attentional blinding effects in addition to the level indexed by the attentional blink. The full mapping of levels in the functional hierarchy onto cortical activation sites and levels is yet to be determined. The existence of such a hierarchy bears importantly on the search for, and the distinctions between, neural correlates of conscious and unconscious vision.

An integrative neural model of social perception, action observation, and theory of mind

In the field of social neuroscience, major branches of research have been instrumental in describing independent components of typical and aberrant social information processing, but the field as a whole lacks a comprehensive model that integrates different branches. We review existing research related to the neural basis of three key neural systems underlying social information processing: social perception, action observation, and theory of mind. We propose an integrative model that unites these three processes and highlights the posterior superior temporal sulcus (pSTS), which plays a central role in all three systems. Furthermore, we integrate these neural systems with the dual system account of implicit and explicit social information processing. Large-scale meta-analyses based on Neurosynth confirmed that the pSTS is at the intersection of the three neural systems. Resting-state functional connectivity analysis with 1000 subjects confirmed that the pSTS is connected to all other regions in these systems. The findings presented in this review are specifically relevant for psychiatric research especially disorders characterized by social deficits such as autism spectrum disorder.

The functional architecture for face-processing expertise: FMRI evidence of the developmental trajectory of the core and the extended face systems

Expertise in processing faces is a cornerstone of human social interaction. However, the developmental course of many key brain regions supporting face preferential processing in the human brain remains undefined. Here, we present findings from an FMRI study using a simple viewing paradigm of faces and objects in a continuous age sample covering the age range from 6 years through adulthood. These findings are the first to use such a sample paired with whole-brain FMRI analyses to investigate development within the core and extended face networks across the developmental spectrum from middle childhood to adulthood. We found evidence, albeit modest, for a developmental trend in the volume of the right fusiform face area (rFFA) but no developmental change in the intensity of activation. From a spatial perspective, the middle portion of the right fusiform gyrus most commonly found in adult studies of face processing was increasingly likely to be included in the FFA as age increased to adulthood. Outside of the FFA, the most striking finding was that children hyperactivated nearly every aspect of the extended face system relative to adults, including the amygdala, anterior temporal pole, insula, inferior frontal gyrus, anterior cingulate gyrus, and parietal cortex. Overall, the findings suggest that development is best characterized by increasing modulation of face-sensitive regions throughout the brain to engage only those systems necessary for task requirements.

Laterality effect for faces in chimpanzees (Pan troglodytes)

Face perception in humans is governed more by right-hemispheric than left-hemispheric neural correlate. Some but not all neurophysiological studies depict a right-side dominance for face responsive neurons in the brains of macaques. Hence, it is an open question whether and to what extent a right-hemisphere preference of processing faces exists across primate brains. We investigated chimpanzees discriminating chimeric faces of chimpanzees and humans, i.e., the combination of either left or right sides of a face vertically flipped and merged into a whole face. We found an effect of choosing the left-chimeric face more often than the right-chimeric face as being the one of the two that is closer to the original face, reflecting an advantage for the right side of the brain to process faces, as reported in humans. Moreover, we found a modulation by age of the participants, suggesting that the exposure history with a particular category shapes the right-hemispheric neural correlate to a configural/holistic processing strategy. In other words, the findings in chimpanzee participants parallel those in human participants and are suggestive for similar neural machineries in the occipital-temporal cortices in both species.

Unconscious presentation of fearful face modulates electrophysiological responses to emotional prosody

Cross-modal integration of visual and auditory emotional cues is supposed to be advantageous in the accurate recognition of emotional signals. However, the neural locus of cross-modal integration between affective prosody and unconsciously presented facial expression in the neurologically intact population is still elusive at this point. The present study examined the influences of unconsciously presented facial expressions on the event-related potentials (ERPs) in emotional prosody recognition. In the experiment, fearful, happy, and neutral faces were presented without awareness by continuous flash suppression simultaneously with voices containing laughter and a fearful shout. The conventional peak analysis revealed that the ERPs were modulated interactively by emotional prosody and facial expression at multiple latency ranges, indicating that audio-visual integration of emotional signals takes place automatically without conscious awareness. In addition, the global field power during the late-latency range was larger for shout than for laughter only when a fearful face was presented unconsciously. The neural locus of this effect was localized to the left posterior fusiform gyrus, giving support to the view that the cortical region, traditionally considered to be unisensory region for visual processing, functions as the locus of audiovisual integration of emotional signals.

Disruption of visual awareness during the attentional blink is reflected by selective disruption of late-stage neural processing

Any information represented in the brain holds the potential to influence behavior. It is therefore of broad interest to determine the extent and quality of neural processing of stimulus input that occurs with and without awareness. The attentional blink is a useful tool for dissociating neural and behavioral measures of perceptual visual processing across conditions of awareness. The extent of higher-order visual information beyond basic sensory signaling that is processed during the attentional blink remains controversial. To determine what neural processing at the level of visual-object categorization occurs in the absence of awareness, electrophysiological responses to images of faces and houses were recorded both within and outside the attentional blink period during a rapid serial visual presentation stream. Electrophysiological results were sorted according to behavioral performance (correctly identified targets vs. missed targets) within these blink and nonblink periods. An early index of face-specific processing (the N170, 140- to 220-msec poststimulus) was observed regardless of whether the participant demonstrated awareness of the stimulus, whereas a later face-specific effect with the same topographic distribution (500- to 700-msec poststimulus) was only seen for accurate behavioral discrimination of the stimulus content. The present findings suggest a multistage process of object-category processing, with only the later phase being associated with explicit visual awareness.

Neural correlates of covert face processing: fMRI evidence from a prosopagnosic patient

Brains can perceive or recognize a face even though we are subjectively unaware of the existence of that face. However, the exact neural correlates of such covert face processing remain unknown. Here, we compared the fMRI activities between a prosopagnosic patient and normal controls when they saw famous and unfamiliar faces. When compared with objects, the patient showed greater activation to famous faces in the fusiform face area (FFA) though he could not overtly recognize those faces. In contrast, the controls showed greater activation to both famous and unfamiliar faces in the FFA. Compared with unfamiliar faces, famous faces activated the controls', but not the patient's lateral prefrontal cortex (LPFC) known to be involved in familiar face recognition. In contrast, the patient showed greater activation in the bilateral medial frontal gyrus (MeFG). Functional connectivity analyses revealed that the patient's right middle fusiform gyrus (FG) showed enhanced connectivity to the MeFG, whereas the controls' middle FG showed enhanced connectivity to the LPFC. These findings suggest that the FFA may be involved in both covert and overt face recognition. The patient's impairment in overt face recognition may be due to the absence of the coupling between the right FG and the LPFC.

Problems in using d' measures to assess subjective awareness

An accurate method of assessing the awareness to primes is crucial to investigations of subliminal perception. In a recent paper, Vermeiren and Cleeremans (2012) contend that traditional measures of prime detection potentially overestimate awareness to the prime. This can lead to wrongly classifying effects as subliminal, since even when primes are detected at chance level, it could be due to factors other than visibility. Here, I address this and point to another fundamental issue that is inherent to d′ calculations, and has to be considered when using signal detection methods to assess awareness. In subliminal perception studies, unconscious processing of the stimuli is assumed when d′ is not significantly different from zero. However, this is a null finding that leaves open the possibility of there being differences that the statistical test was not sensitive enough to detect. Hence, reported subliminal effects, especially small effects, could have occurred as a consequence of visible trials even when d′ did not significantly differ from chance. Therefore, additional measures such as bootstrapping, which could complement d′ in ensuring that the effects were not a consequence of a small number of trials, should be utilized in future studies.

Gray matter volume abnormalities in individuals with cognitive vulnerability to depression: a voxel-based morphometry study

BACKGROUND

The hopelessness theory of depression posits that individuals with negative cognitive styles are at an increased risk for depression following negative life events. In neuroimaging studies, brain gray matter volume abnormalities correlate with the presence of depressive disorders. However, it is unknown whether changes in gray matter volume also appear in healthy individuals with cognitive vulnerability to depression (CVD).

METHODS

30 subjects diagnosed with CVD, 33 first-episode patients with major depressive disorder (MDD), and 32 healthy controls were examined using voxel-based morphometry following magnetic resonance imaging (MRI).

RESULTS

We found significant volumetric differences between three groups in the left precentral gyrus, right fusiform gyrus and the right thalamus. In these regions, compared to controls, CVD subjects showed reduced gray matter volumes in the left precentral gyrus and right fusiform gyrus. MDD patients demonstrated reduced gray matter volume in the left precentral gyrus and increased gray matter volume in the right thalamus. Additionally, CVD individuals had significantly smaller right fusiform gyrus and right thalamus than MDD patients. The weakest-link scores on CSQ were negatively correlated with gray matter volumes in the left precentral gyrus.

CONCLUSIONS

Reductions in brain gray matter volume exist widely in individuals with CVD. In addition, there exist similar abnormalities in gray matter volume in both CVD subjects and MDD patients. Reductions of gray matter volume in the left precentral gyrus might be correlated to the negative cognitive styles, as well as an increased risk for depression.

Crossmodal interactions in audiovisual emotion processing

Emotion in daily life is often expressed in a multimodal fashion. Consequently emotional information from one modality can influence processing in another. In a previous fMRI study we assessed the neural correlates of audio-visual integration and found that activity in the left amygdala is significantly attenuated when a neutral stimulus is paired with an emotional one compared to conditions where emotional stimuli were present in both channels. Here we used dynamic causal modelling to investigate the effective connectivity in the neuronal network underlying this emotion presence congruence effect. Our results provided strong evidence in favor of a model family, differing only in the interhemispheric interactions. All winning models share a connection from the bilateral fusiform gyrus (FFG) into the left amygdala and a non-linear modulatory influence of bilateral posterior superior temporal sulcus (pSTS) on these connections. This result indicates that the pSTS not only integrates multi-modal information from visual and auditory regions (as reflected in our model by significant feed-forward connections) but also gates the influence of the sensory information on the left amygdala, leading to attenuation of amygdala activity when a neutral stimulus is integrated. Moreover, we found a significant lateralization of the FFG due to stronger driving input by the stimuli (faces) into the right hemisphere, whereas such lateralization was not present for sound-driven input into the superior temporal gyrus. In summary, our data provides further evidence for a rightward lateralization of the FFG and in particular for a key role of the pSTS in the integration and gating of audio-visual emotional information.

Exposure to subliminal arousing stimuli induces robust activation in the amygdala, hippocampus, anterior cingulate, insular cortex and primary visual cortex: a systematic meta-analysis of fMRI studies

Functional Magnetic Resonance Imaging (fMRI) demonstrates that the subliminal presentation of arousing stimuli can activate subcortical brain regions independently of consciousness-generating top-down cortical modulation loops. Delineating these processes may elucidate mechanisms for arousal, aberration in which may underlie some psychiatric conditions. Here we are the first to review and discuss four Activation Likelihood Estimation (ALE) meta-analyses of fMRI studies using subliminal paradigms. We find a maximum of 9 out of 12 studies using subliminal presentation of faces contributing to activation of the amygdala, and also a significantly high number of studies reporting activation in the bilateral anterior cingulate, bilateral insular cortex, hippocampus and primary visual cortex. Subliminal faces are the strongest modality, whereas lexical stimuli are the weakest. Meta-analyses independent of studies using Regions of Interest (ROI) revealed no biasing effect. Core neuronal arousal in the brain, which may be at first independent of conscious processing, potentially involves a network incorporating primary visual areas, somatosensory, implicit memory and conflict monitoring regions. These data could provide candidate brain regions for the study of psychiatric disorders associated with aberrant automatic emotional processing.

Sandwich masking eliminates both visual awareness of faces and face-specific brain activity through a feedforward mechanism

It is generally agreed that considerable amounts of low-level sensory processing of visual stimuli can occur without conscious awareness. On the other hand, the degree of higher level visual processing that occurs in the absence of awareness is as yet unclear. Here, event-related potential (ERP) measures of brain activity were recorded during a sandwich-masking paradigm, a commonly used approach for attenuating conscious awareness of visual stimulus content. In particular, the present study used a combination of ERP activation contrasts to track both early sensory-processing ERP components and face-specific N170 ERP activations, in trials with versus without awareness. The electrophysiological measures revealed that the sandwich masking abolished the early face-specific N170 neural response (peaking at ~170 ms post-stimulus), an effect that paralleled the abolition of awareness of face versus non-face image content. Furthermore, however, the masking appeared to render a strong attenuation of earlier feedforward visual sensory-processing signals. This early attenuation presumably resulted in insufficient information being fed into the higher level visual system pathways specific to object category processing, thus leading to unawareness of the visual object content. These results support a coupling of visual awareness and neural indices of face processing, while also demonstrating an early low-level mechanism of interference in sandwich masking.

Conscious awareness is necessary for processing race and gender information from faces

Previous studies suggested that emotions can be correctly interpreted from facial expressions in the absence of conscious awareness of the face. Our goal was to explore whether subordinate information about a face's gender and race could also become available without awareness of the face. Participants classified the race or the gender of unfamiliar faces that were ambiguous with regard to these dimensions. The ambiguous faces were preceded by face-images that unequivocally represented gender and race, rendered consciously invisible by simultaneous continuous-flash-suppression. The classification of ambiguous faces was biased away from the category of the adaptor only when it was consciously visible. The duration of subjective visibility correlated with the aftereffect strength. Moreover, face identity was consequential only if consciously perceived. These results suggest that while conscious awareness is not needed for basic level categorization, it is needed for subordinate categorization. Emotional information might be unique in this respect.

fMRI evidence of neural abnormalities in the subcortical face processing system in ASD

Recent evidence suggests that a rapid, automatic face detection system is supported by subcortical structures including the amygdala, pulvinar, and superior colliculus. Early-emerging abnormalities in these structures may be related to reduced social orienting in children with autism, and subsequently, to aberrant development of cortical circuits involved in face processing. Our objective was to determine whether functional abnormalities in the subcortical face processing system are present in adults with autism spectrum disorders (ASD) during supraliminal fearful face processing. Participants included twenty-eight individuals with ASD and 25 controls group-matched on age, IQ, and behavioral performance. The ASD group met diagnostic criteria on the ADI-R, ADOS-G, and DSM-IV. Both the ASD and control groups showed significant activation in bilateral fusiform gyri. The control group exhibited additional significant responses in the right amygdala, right pulvinar, and bilateral superior colliculi. In the direct group comparison, the controls showed significantly greater activation in the left amygdala, bilateral fusiform gyrus, right pulvinar, and bilateral superior colliculi. No brain region showed significantly greater activation in the ASD group compared to the controls. Thus, basic rapid face identification mechanisms appear to be functional in ASD. However, individuals with ASD failed to engage the subcortical brain regions involved in face detection and automatic emotional face processing, suggesting a core mechanism for impaired socioemotional processing in ASD. Neural abnormalities in this system may contribute to early-emerging deficits in social orienting and attention, the putative precursors to abnormalities in social cognition and cortical face processing specialization.

Brain mechanisms for representing what another person sees

We used functional magnetic resonance imaging (fMRI) and a naturalistic joint attention scenario to evaluate two, alternative hypotheses concerning the social brain. The first, Content Specific Attribution hypothesis, was that core regions previously identified as being involved in social cognition also participate in representing the contents of another mind. The second, Dual Role hypothesis, was that extrastriate, category-specific visual regions respond to a visible stimulus of a specific category and to the same stimulus occluded, but when it appears to be the focus of another person's visual attention. Participants viewed category-specific stimuli (Place and Body images) to localize the extrastriate body area (EBA) and parahippocampal place area (PPA). Then, they observed a computerized character viewing each stimulus category, occluded from the participant's view. In support of the Content Specific Attribution hypothesis, whole-brain analyses revealed that viewing someone else looking at an occluded picture of a body activated brain regions previously associated with components of social cognition more than viewing someone else looking at an occluded picture of a place. Counter to the Dual Role hypothesis, functional region of interest (ROI) analyses revealed that the EBA and PPA were not clearly involved in representing what the character was seeing.

Difficulty identifying feelings and automatic activation in the fusiform gyrus in response to facial emotion

Difficulties in identifying and differentiating one's emotions are a central characteristic of alexithymia. In the present study, automatic activation of the fusiform gyrus to facial emotion was investigated as a function of alexithymia as assessed by the 20-item Toronto Alexithymia Scale. During 3 Tesla fMRI scanning, pictures of faces bearing sad, happy, and neutral expressions masked by neutral faces were presented to 22 healthy adults who also responded to the Toronto Alexithymia Scale. The fusiform gyrus was selected as the region of interest, and voxel values of this region were extracted, summarized as means, and tested among the different conditions (sad, happy, and neutral faces). Masked sad facial emotions were associated with greater bilateral activation of the fusiform gyrus than masked neutral faces. The subscale, Difficulty Identifying Feelings, was negatively correlated with the neural response of the fusiform gyrus to masked sad faces. The correlation results suggest that automatic hyporesponsiveness of the fusiform gyrus to negative emotion stimuli may reflect problems in recognizing one's emotions in everyday life.

Functional brain correlates of social and nonsocial processes in autism spectrum disorders: an activation likelihood estimation meta-analysis

BACKGROUND

Functional neuroimaging studies of autism spectrum disorders (ASD) have examined social and nonsocial paradigms, although rarely in the same study. Here, we provide an objective, unbiased survey of functional brain abnormalities in ASD, related to both social and nonsocial processing.

METHODS

We conducted two separate voxel-wise activation likelihood estimation meta-analyses of 39 functional neuroimaging studies consisting of 24 studies examining social processes (e.g., theory of mind, face perception) and 15 studies examining nonsocial processes (e.g., attention control, working memory). Voxel-wise significance threshold was p<.05, corrected by false discovery rate.

RESULTS

Compared with neurotypical control (NC) subjects, ASD showed greater likelihood of hypoactivation in two medial wall regions: perigenual anterior cingulate cortex (ACC) in social tasks only and dorsal ACC in nonsocial studies. Further, right anterior insula, recently linked to social cognition, was more likely to be hypoactivated in ASD in the analyses of social studies. In nonsocial studies, group comparisons showed greater likelihood of activation for the ASD group in the rostral ACC region that is typically suppressed during attentionally demanding tasks.

CONCLUSIONS

Despite substantial heterogeneity of tasks, the rapidly increasing functional imaging literature showed ASD-related patterns of hypofunction and aberrant activation that depended on the specific cognitive domain, i.e., social versus nonsocial. These results provide a basis for targeted extensions of these findings with younger subjects and a range of paradigms, including analyses of default mode network regulation in ASD.

Mapping social target detection with functional magnetic resonance imaging

The neural correlates of cognitive control and social processing functions, as well as the characteristic patterns of anomalous brain activation patterns in psychiatric conditions associated with impairment in these functions, have been well characterized. However, these domains have primarily been examined in isolation. The present study used event-related functional magnetic resonance imaging to map brain areas recruited during a target-detection task designed to evaluate responses to both non-social (i.e. shape) and social (i.e. face) target stimuli. Both shape and face targets activated a similar brain network, including the postcentral gyrus, the anterior and posterior cingulate gyri and the right midfrontal gyrus, whereas face targets additionally activated the thalamus, fusiform and temporooccipital cortex, lingual gyrus and paracingulate gyrus. Comparison of activations to social and non-social target events revealed that a small portion of the dorsal anterior cingulate gyrus (Brodmann's area 32) and the supracalcarine cortex were preferentially activated to face targets. These findings indicate that non-social and social stimuli embedded within a cognitive control task activate overlapping and distinct brain regions. Clinical cognitive neuroscience research of disorders characterized by cognitive dysfunction and impaired social processing would benefit from the use of tasks that evaluate the combined effects of deficits in these two domains.

Early category-specific cortical activation revealed by visual stimulus inversion

Visual categorization may already start within the first 100-ms after stimulus onset, in contrast with the long-held view that during this early stage all complex stimuli are processed equally and that category-specific cortical activation occurs only at later stages. The neural basis of this proposed early stage of high-level analysis is however poorly understood. To address this question we used magnetoencephalography and anatomically-constrained distributed source modeling to monitor brain activity with millisecond-resolution while subjects performed an orientation task on the upright and upside-down presented images of three different stimulus categories: faces, houses and bodies. Significant inversion effects were found for all three stimulus categories between 70-100-ms after picture onset with a highly category-specific cortical distribution. Differential responses between upright and inverted faces were found in well-established face-selective areas of the inferior occipital cortex and right fusiform gyrus. In addition, early category-specific inversion effects were found well beyond visual areas. Our results provide the first direct evidence that category-specific processing in high-level category-sensitive cortical areas already takes place within the first 100-ms of visual processing, significantly earlier than previously thought, and suggests the existence of fast category-specific neocortical routes in the human brain.

A tale of two recognition systems: implications of the fusiform face area and the visual word form area for lateralized object recognition models

Two areas of current intense interest in the neuroimaging literature are that of the visual word form area (VWFA) and of the fusiform face area (FFA) and their roles in word and face perception, respectively. These two areas are of particular relevance to laterality research because visual word identification and face identification have long been shown to be especially lateralized to the left hemisphere and the right hemisphere, respectively. This review therefore seeks to evaluate their significance for the broader understanding of lateralization of object recognition. A multi-level model of lateralized object recognition is proposed based on a combination of behavioral and neuroimaging findings. Rather than seek to characterize hemispheric asymmetries according to a single principle (e.g., serial-parallel), it is suggested that current observations can be understood in terms of three asymmetric levels of processing, using the framework of the Janus model of hemispheric function. It is suggested that the left hemisphere represents features using an abstract-category code whereas the RH utilizes a specific-exemplar code. The relationships between these features are also coded asymmetrically, with the LH relying on associative co-occurrence values and the RH relying on spatial metrics. Finally, the LH controlled selection system focuses on isolating features and the RH focuses on conjoining features. It is suggested that each hemisphere utilizes efficient (apparently parallel) processing when stimuli are congruent with its preferred processing style and inefficient (apparently serial) processing when they are not, resulting in the typical left-lateralization for orthographic analysis and right-lateralization for face analysis.

Guided saccades modulate face- and body-sensitive activation in the occipitotemporal cortex during social perception

Functional magnetic resonance imaging (fMRI) has identified distinct brain regions in ventral occipitotemporal cortex (VOTC) and lateral occipitotemporal cortex (LOTC) that are differentially activated by pictures of faces and bodies. Recent work from our laboratory has shown that the strong LOTC activation evoked by bodies in which the face is occluded is attenuated when the occlusion is removed. We hypothesized that this attenuation may occur because subjects preferentially fixate upon faces when present in the scene. Here, we experimentally manipulated subjects' fixations while they viewed a static picture of a character whose face, hand, and torso were continuously visible throughout each run. The subject's saccades and fixations were guided by a small fixation cross that made discrete jumps to a new location every 500ms. Subjects were instructed to follow the fixation cross and make a button press whenever it changed size. In a series of blocks, the fixation cross shifted from locations on the face, on the hand, and to locations on a background image of a phase-scrambled face. In a second study, the fixation cross moved similarly, but the hand locations were changed to locations along the character's body or torso. A localizer task was used to identify face- and body-sensitive regions of LOTC. Body-sensitive regions were strongly activated when the subjects' saccades were guided over the character's torso relative to when the saccades were guided over the character's face. Little to no activity occurred in the body-sensitive region of LOTC when the subjects' saccades were guided over the character's hand. The localizer task was unable to differentiate body-sensitive regions in lateral VOTC from face-sensitive regions, or body-sensitive regions in medial VOTC from flower-sensitive regions. Guided saccades over the body strongly activated both lateral and medial VOTC. These results provide new insights into the function of body-sensitive visual areas in both LOTC and VOTC, and illustrate the potential confounding influence of uncontrolled eye movements for neuroimaging studies of social perception.