Self-focused attention vs. negative attentional bias during public speech task in socially anxious individuals.

Enhanced self-focused attention (SFA) and negative attentional bias (NAB) towards social cues are characteristic hallmarks of social anxiety. It is essential to investigate these two attentional phenomena under socially relevant situations using comparable stimuli. In the present study, individuals with high social anxiety (HSA, n = 32) and low social anxiety (LSA, n = 29) were compared according to their attention toward self-related stimuli and toward positive, neutral, and negative feedback related stimuli. Video stimuli of moving indicators of self-anxiety-status and positive, neutral, and negative feedback from an audience were presented during an impromptu speech task (high anxiety condition) and a re-watching phase (low anxiety condition). Eye movements in response to the different stimuli served as readouts for attentional preference. An interaction effect suggested that the HSA group directed more attention to self-related stimuli relative to other stimuli and the LSA group only during the high anxiety condition. The LSA group exhibited a general attentional preference toward positive feedback, especially during the low anxiety condition. Meanwhile, only the total duration of fixation on positive feedback negatively correlated with subjective anxiety rating. Our results point to increased SFA rather than NAB in HSA individuals under social threats.

Avoidance of all feedback? Attention allocation during and after public speech in social anxiety.

BACKGROUND AND OBJECTIVES: Attention avoidance of feedback-related stimuli is proposed to be associated with and maintain social anxiety. However, previous research has mainly focused on comparing the attention bias between two types of stimuli, while little is known about attention distribution patterns among positive, neutral, and negative feedback and non-feedback stimuli in individuals with high trait social anxiety (HSA) or low trait social anxiety (LSA). METHODS: The current study assessed eye movement pattern of participants with HSA or LSA during a speech task (high anxiety condition) or while solely watching audience feedback of the speech (low anxiety condition). A pre-recorded audience who displayed approving, neutral, or disapproving gestures was presented as feedback stimuli, while neutral facial photos were used as non-feedback stimuli. RESULTS: Only in the high anxiety condition, participants with HSA exhibited longer total fixation on non-feedback stimuli compared to those with LSA; whereas in the low anxiety condition, both groups paid more attention to emotional feedback stimuli. LIMITATIONS: The final sample size was modest due to a high suspicion rate of the reality of the audience. CONCLUSIONS: These findings suggest that only in highly anxious social situations, socially anxious individuals lack the attentional preference toward positive feedback that individuals with low anxious have.

The Critical Role of V2 Population Receptive Fields in Visual Orientation Crowding.

Crowding, the identification difficulty for a target in the presence of nearby flankers, is an essential bottleneck for object recognition and visual awareness [1, 2]. As suggested by multitudes of behavioral studies, crowding occurs because the visual system lacks the necessary resolution (e.g., small receptive field or high resolution of spatial attention) to isolate the target from flankers and therefore integrates them mistakenly [3-12]. However, this idea has rarely been tested with neuroscience methods directly. Here, using the fMRI-based population receptive field (pRF) technique [13, 14], we found that, across individual subjects, the average pRF size of the voxels in V2 responding to the target could predict the magnitude of visual orientation crowding. The smaller the pRF size, the weaker the crowding effect. Furthermore, we manipulated the magnitude of the crowding effect within subjects. The pRF size in V2 was smaller in a weak crowding condition than in a strong crowding condition, and this difference was attention dependent. More importantly, we found that perceptual training could alleviate the orientation crowding and causally shrink the pRF size in V2. Taken together, these findings provide strong and converging evidence for a critical role of V2 pRFs in visual orientation crowding. We speculate that, synergistic with spatial attention, the dynamic and plastic nature of the V2 pRFs serves to prevent interference from the flankers through adjusting their size and consequently reduces visual crowding.

[Applications of the population receptive field technique in the field of neural mechanisms of sensory perception].

The population receptive field (pRF) of a voxel is the joint receptive field of the population of neurons within the voxel. Using a non-invasive pRF technique, researcher can estimate the pRF position and size parameters of each voxel in human brain. These pRF parameters provide an excellent research basis to study neural mechanisms of sensory perception. Although the pRF technique has developed very rapidly in recent years and been widely used in the field of neural mechanisms of sensory perception, related review article is still absent. Here, we provide an overview of the pRF technique. First, we briefly introduce research methods of this technique. Next, we focus on applications of this technique in the field of neural mechanisms of sensory perception. Then, we discuss advantages and limitations of the pRF technique in practical application. In the end, we give some suggestions on the future application direction of the pRF technique. The pRF technique has played an important role in the research of neural mechanism of sensory perception, and it would play a more important role in the future.

Attention Priority Map of Face Images in Human Early Visual Cortex.

Attention priority maps are topographic representations that are used for attention selection and guidance of task-related behavior during visual processing. Previous studies have identified attention priority maps of simple artificial stimuli in multiple cortical and subcortical areas, but investigating neural correlates of priority maps of natural stimuli is complicated by the complexity of their spatial structure and the difficulty of behaviorally characterizing their priority map. To overcome these challenges, we reconstructed the topographic representations of upright/inverted face images from fMRI BOLD signals in human early visual areas primary visual cortex (V1) and the extrastriate cortex (V2 and V3) based on a voxelwise population receptive field model. We characterized the priority map behaviorally as the first saccadic eye movement pattern when subjects performed a face-matching task relative to the condition in which subjects performed a phase-scrambled face-matching task. We found that the differential first saccadic eye movement pattern between upright/inverted and scrambled faces could be predicted from the reconstructed topographic representations in V1-V3 in humans of either sex. The coupling between the reconstructed representation and the eye movement pattern increased from V1 to V2/3 for the upright faces, whereas no such effect was found for the inverted faces. Moreover, face inversion modulated the coupling in V2/3, but not in V1. Our findings provide new evidence for priority maps of natural stimuli in early visual areas and extend traditional attention priority map theories by revealing another critical factor that affects priority maps in extrastriate cortex in addition to physical salience and task goal relevance: image configuration.SIGNIFICANCE STATEMENT Prominent theories of attention posit that attention sampling of visual information is mediated by a series of interacting topographic representations of visual space known as attention priority maps. Until now, neural evidence of attention priority maps has been limited to studies involving simple artificial stimuli and much remains unknown about the neural correlates of priority maps of natural stimuli. Here, we show that attention priority maps of face stimuli could be found in primary visual cortex (V1) and the extrastriate cortex (V2 and V3). Moreover, representations in extrastriate visual areas are strongly modulated by image configuration. These findings extend our understanding of attention priority maps significantly by showing that they are modulated, not only by physical salience and task-goal relevance, but also by the configuration of stimuli images.

Predictive feature remapping before saccadic eye movements.

Saccadic eye movements cause rapid and dramatic displacements of the retinal image of the visual world, yet our conscious perception of the world remains stable and continuous. A popular explanation for this remarkable ability of our visual system to compensate for the displacements is the predictive feature remapping theory. The theory proposes that, before saccades, the representation of a visual stimulus can be predictively transferred from neurons that initially encode the stimulus to neurons whose receptive fields will encompass the stimulus location after the saccade. Visual adaptation aftereffect experiments performed by Melcher (2007) provided psychophysical evidence for this theory. However, it was argued that the visual aftereffects were not measured at the "appropriate" remapped location (Rolfs, Jonikaitis, Deubel, & Cavanagh, 2011). Therefore, whether the remapped representation contains feature information (e.g., orientation, motion direction, or contrast) is still a subject of intense debate. Here, to explore the nature of the predictive transfer during trans-saccadic perception, we measured visual aftereffects (tilt aftereffect, motion aftereffect, and threshold elevation aftereffect) at the appropriate remapped location of adapting stimuli before saccades. We observed a significant tilt aftereffect and motion aftereffect, but little threshold elevation aftereffect. Furthermore, the tilt aftereffect and motion aftereffect exhibited spatial specificity. These findings provide strong evidence for the predictive feature remapping theory and suggest that intermediate visual processing stages (i.e., extrastriate visual cortex) might be critical for feature remapping. Finally, we propose that the feature remapping process might also contribute to the spatiotopic representation of visual features.

Decoding Visual Location From Neural Patterns in the Auditory Cortex of the Congenitally Deaf.

Sensory cortices of individuals who are congenitally deprived of a sense can exhibit considerable plasticity and be recruited to process information from the senses that remain intact. Here, we explored whether the auditory cortex of congenitally deaf individuals represents visual field location of a stimulus-a dimension that is represented in early visual areas. We used functional MRI to measure neural activity in auditory and visual cortices of congenitally deaf and hearing humans while they observed stimuli typically used for mapping visual field preferences in visual cortex. We found that the location of a visual stimulus can be successfully decoded from the patterns of neural activity in auditory cortex of congenitally deaf but not hearing individuals. This is particularly true for locations within the horizontal plane and within peripheral vision. These data show that the representations stored within neuroplastically changed auditory cortex can align with dimensions that are typically represented in visual cortex.

Position shifts of fMRI-based population receptive fields in human visual cortex induced by Ponzo illusion.

Ponzo illusion is a well-known perceptual phenomenon in which the perceived sizes of visual objects are altered by visual depth cues created by converging lines at the horizon. One possible neural mechanism of the Ponzo illusion is the receptive field position shifts of V1 neurons, as supported by a recent monkey electrophysiological study (Ni et al. in Curr Biol 24(14):1653-1658, 2014). Here, we used fMRI-based population receptive field (pRF) mapping technique in combination of psychophysics to investigate this idea. We found that, relative to the close apparent depth in a 3D scene, the far apparent depth in the scene caused the pRF positions of voxels in V1-V3 to shift toward the fovea, in line with subjects' percept of the Ponzo illusion. Moreover, the pRF position shift in V1 significantly correlated with the magnitude of the Ponzo illusion across individual subjects. Our findings thus provide evidence for the close association between the perceived object size and the pRF position shift in human visual areas, especially in V1, lending further support for the receptive field position shift explanation for the Ponzo illusion.

Opposite modulation of high- and low-level visual aftereffects by perceptual grouping.

A fundamental task of visual perception is to group visual features - sometimes spatially separated and partially occluded - into coherent, unified representations of objects. Perceptual grouping can vastly simplify the description of a visual scene and is critical for our visual system to understand the three-dimensional visual world. Numerous neurophysiological and brain imaging studies have demonstrated that neural mechanisms of perceptual grouping are characterized by the enhancement of neural responses throughout the visual processing hierarchy, from lower visual areas processing grouped features to higher visual areas representing objects and shapes from grouping. In a series of psychophysical adaptation experiments, we made the counterintuitive observation that perceptual grouping amplified the shape aftereffect but meanwhile, reduced the tilt aftereffect and the threshold elevation aftereffect (TEAE). Furthermore, the modulation of perceptual grouping on the TEAE showed a partial interocular transfer. This finding suggests a 2-fold effect of perceptual grouping - enhancing the high-level shape representation and attenuating the low-level feature representation even at a monocular level. We propose that this effect is a functional manifestation of a predictive coding scheme and reflects an efficient code of visual information across lower and higher visual cortical areas.

Effects of face view discrimination learning on N170 latency and amplitude.

Learning is critical for fast and efficient object recognition. However, the neural implementation of object learning in the human brain remains largely unknown. Using combined psychophysics and electroencephalogram (EEG), we investigated the effects of perceptual learning on face processing. Human subjects were trained to discriminate face views at an in-depth face orientation (i.e. 30°) over eight daily sessions, which resulted in a significant improvement in sensitivity to the trained face view. Psychophysical results showed that this improvement was highly specific to the trained view. Before and after training, we recorded subjects' EEG signals responding to the trained and the untrained face views. Analyses of event-related potentials (ERPs) showed that face view discrimination training led to a larger reduction of N170 latency at the left occipital-temporal area with the trained face view, compared with the untrained ones. These findings provide evidence for the facilitation model on neuronal plasticity from visual experience, suggesting a faster processing speed of face induced by perceptual learning.

Learning to discriminate face views.

Although perceptual learning of simple visual features has been studied extensively and intensively for many years, we still know little about the mechanisms of perceptual learning of complex object recognition. In a series of seven experiments, human perceptual learning in discrimination of in-depth orientation of face view was studied using psychophysical methods. We trained subjects to discriminate face orientations around a face view (i.e., 30°) over eight daily sessions, which resulted in a significant improvement in sensitivity to the face view orientation. This improved sensitivity was highly specific to the trained orientation and persisted up to 6 mo. Different from perceptual learning of simple visual features, this orientation-specific learning effect could completely transfer across changes in face size, visual field, and face identity. A complete transfer also occurred between two partial face images that were mutually exclusive but constituted a complete face. However, the transfer of the learning effect between upright and inverted faces and between a face and a paperclip object was very weak. These results shed light on the mechanisms of the perceptual learning of face view discrimination. They suggest that the visual system had learned how to compute face orientation from face configural information more accurately and that a large amount of plastic changes took place at a level of higher visual processing where size-, location-, and identity-invariant face views are represented.