Automatic processing of unattended mean emotion: Evidence from visual mismatch responses.

The mean emotion from multiple facial expressions can be extracted rapidly and precisely. However, it remains debated whether mean emotion processing is automatic which can occur under no attention. To address this question, we used a passive oddball paradigm and recorded event-related brain potentials when participants discriminated the changes in the central fixation while a set of four faces was presented in the periphery. The face set consisted of one happy and three angry expressions (mean negative) or one angry and three happy expressions (mean positive), and the mean negative and mean positive face sets were shown with a probability of 20% (deviant) and 80% (standard) respectively in the sequence, or the vice versa. The cluster-based permutation analyses showed that the visual mismatch negativity started early at around 92 ms and was also observed in later time windows when the mean emotion was negative, while a mismatch positivity was observed at around 168-266 ms when the mean emotion was positive. The results suggest that there might be different mechanisms underlying the processing of mean negative and mean positive emotions. More importantly, the brain can detect the changes in the mean emotion automatically, and ensemble coding for multiple facial expressions can occur in an automatic fashion without attention.

Saliency affects attentional capture and suppression of abrupt-onset and color singleton distractors: Evidence from event-related potential studies.

Attention is the process of selecting relevant information and suppressing irrelevant information. However, it is still controversial whether attentional capture by salient but task-irrelevant stimuli operates in a bottom-up fashion (stimulus-driven theory) or a top-down fashion (goal-driven theory) or if even salient distractors can be suppressed before capturing attention (signal suppression theory). In the present study, we investigated how saliency affects attentional capture (indexed by N2-posterior-contralateral [N2pc]) and suppression (indexed by distractor positivity [PD ]) of abrupt-onset and color singleton distractors in a visual search task. Experiment 1 showed that an abrupt-onset distractor elicited both N2pc and PD , while a color singleton distractor elicited only PD . Moreover, the abrupt-onset distractor elicited a larger N2pc and a larger PD relative to the color singleton distractor. In addition, both distractors elicited an early positive component, the positivity posterior contralateral (Ppc), which was also larger for abrupt onsets than for color singletons. Experiment 2 further demonstrated that when both the abrupt onset and color singleton were designed as targets, and thus required no attentional suppression, Ppc was elicited, but PD was not. This corroborated the finding in Experiment 1 that the later PD , not the early Ppc, reflected attentional suppression. Therefore, a more salient distractor demonstrates stronger early perceptual processing, can capture attention better and needs more attentional resources to be suppressed later. Based on these results, a three-stage hypothesis is proposed, in which the saliency of a distractor modulates processing at early perception, attentional capture, and suppression stages.

Neural correlates of conscious processing of emotional faces: Evidence from event-related potentials.

There is a theoretical debate between the early and late neural correlates of consciousness (NCCs). Previous studies using neutral face stimuli supported an early NCC and suggested that visual awareness negativity (VAN) is associated with consciousness, while late positivity (LP) reflects post-perceptual activity. However, emotional faces may help to examine the relationship between LP and consciousness due to the differences in late processing between emotional and neutral faces. To explore the effects of facial emotional information on NCCs, the present study manipulated consciousness with the inattentional blindness paradigm and used happy, fearful, and neutral faces as visual stimuli. The results showed that the conscious processing of emotional faces was correlated with VAN and LP, while the conscious processing of neutral faces was associated with VAN. First, the results suggest that VAN is an NCC, and the relationship between LP and consciousness is affected by facial emotional information. Second, VAN reflects the early perceptual experience of emotional faces, whereas LP may reflect the late conscious processing of emotional faces. Furthermore, source localization analysis showed that the LPs of emotional faces were mainly located in the frontal and parietal lobes, whereas those of neutral faces showed no significant activation. This suggests that facial emotional information may affect the brain regions associated with conscious processing. Time-frequency analysis showed that conscious processing is related to the enhancement of alpha and theta oscillation, indicating that conscious processing may be associated with the suppression of irrelevant stimuli. Overall, the present study suggests that the integration of the theories that support early and late NCCs helps explain the conscious processing of emotional faces.

Visual Mismatch Negativity Reflects Enhanced Response to the Deviant: Evidence From Event-Related Potentials and Electroencephalogram Time-Frequency Analysis.

Automatic detection of information changes in the visual environment is crucial for individual survival. Researchers use the oddball paradigm to study the brain's response to frequently presented (standard) stimuli and occasionally presented (deviant) stimuli. The component that can be observed in the difference wave is called visual mismatch negativity (vMMN), which is obtained by subtracting event-related potentials (ERPs) evoked by the deviant from ERPs evoked by the standard. There are three hypotheses to explain the vMMN. The sensory fatigue (or refractoriness) hypothesis considers that weakened neural activity caused by repetition results in decreased ERPs of the standard. The memory trace hypothesis proposes that vMMN results from increased responses to the deviant. The predictive coding hypothesis attributes the difference to enhanced responses for deviants and suppression for standards. However, when distinguishing between these effects, previous researchers did not consider the effect of low-level features on the vMMN. In this experiment, we used face sequences composed of different emotions (e.g., neutral and fearful face) and presented an oddball sequence, a reverse oddball sequence, and an equiprobable sequence to participants. The deviant of the oddball sequence was subtracted from the standard of the oddball sequence, the reverse oddball sequence, and the same type of stimulus of the equiprobable sequence to get oddball-vMMN (vMMN1), reverse oddball-vMMN (vMMN2), and equiprobable-vMMN (vMMN3), respectively. The results showed no significant difference between vMMN2 and vMMN3 in 100-350 ms following stimulus onset, while the vMMN effect was significant, indicating that the probability of the standard did not affect vMMN, which supported the memory trace hypothesis. Additionally, the fearful-related vMMN were more negative than the neutral-related vMMN within the range of 100-150 ms, suggesting a negative bias. We analyzed the source location of different vMMNs. There was no significant difference in brain regions between different vMMNs. Time-frequency analysis showed that the deviant had stronger theta-band oscillatory than the standard (visual mismatch oscillatory responses, vMORs). However, there was no difference between vMORs2 and vMORs3, indicating that vMORs reflect an enhanced response to the deviant in terms of neural oscillation, supporting the memory trace hypothesis.

The spatiotemporal characteristics of N170s for faces and words: A meta-analysis study.

N170 is a negative event-related potential (ERP) component in response to visual stimuli, such as faces. It remains controversial whether N170 reflects the specific processing of faces or can also be elicited by objects of expertise (e.g., words). In this research, we conducted a meta-analysis for the spatiotemporal characteristics of N170 of face and word stimuli from 24 studies in which both stimuli were presented for each subject. We observed that (1) both face and word stimuli can elicit conspicuous N170s and that there was no difference between the amplitude of face-N170 and word-N170; (2) there is no difference in the latencies between the two N170s; and (3) both N170s are distributed in the occipitotemporal regions but with a reversed hemispheric distribution pattern-face-N170 is more negative in the right than left occipitotemporal regions, while word-N170 is the opposite. These results showed that the face- and word-N170s are qualitatively the same but have different hemispheric lateralization advantages-N170 might be a general neural index of the expertise-dependent object-recognition process in occipitotemporal regions.

Design and Engineering of Hypoxia and Acidic pH Dual-Stimuli-Responsive Intelligent Fluorescent Nanoprobe for Precise Tumor Imaging.

Stimulus-responsive fluorescence imaging modality shows great promise for detection of tumor due to the advantages of high sensitivity, simplicity and noninvasiveness. However, some non-cancer regions including nodules and inflammation may also exhibit a stimulus-related characteristic, which cause the problem of nonspecific responsiveness and then cause "false positive" results for tumor recognition. Herein, hypoxia and acidic pH, two typical features strongly associated with tumor invasion, progression and metastasis in tumor microenvironment (TME), are chosen as dual stimuli to fabricate "dual lock-and-key" fluorescent nanoprobe for highly specific and precise imaging of tumor cells. Mesoporous silica coated gold nanorods (AuNR@mSiO2 ) are employed as nanocarrier and nanoquencher to load the pH-sensitive fluorescent reporter (Rho-TP). Azobenzene (azo) which can be reduced to amines by the highly expressed azoreductase under hypoxic conditions, is elected as the effective gatekeeper for AuNR@mSiO2 by forming complex with ß-cyclodextrin polymer via host-guest interaction (azo/ß-CDP). By elaborately combining the hypoxia-responsive gatekeeper and pH-responsive fluorescent signal reporter into one nanoprobe, sensitive and specific imaging of tumor cells can be realized. The fabricated dual lock-and-key fluorescent nanoprobe successfully further apply in tumor-bearing mice model, which indicate potential of early diagnosis and assessment of cancer treatment.

A near-infrared fluorogenic probe with fast response for detecting sodium dithionite in living cells.

Developing a reliable fluorescence probe is crucial for accurately monitoring sodium dithionite (Na2S2O4, SDT) in biosystems, but the current reported azo-based ones suffers from short excitation/emission wavelengths and relative slow response speed. To address this issue, we herein present a novel near-infrared emissive fluorescence probe for SDT, namely DCM-MQ, consisting of a dicyanomethylene-benzopyran fluorogenic reporter and a 1-methylquinolinium as recognition moiety. On the basis of the specific reduction mechanism, DCM-MQ exhibited a rapid colorimetric and fluorescent recognition for SDT (less than 3 s) with large Stokes shift (112 nm) and high sensitivity (detection limit was 19 nM). The fluorescence imaging results demonstrate that DCM-MQ is competent for monitoring SDT in living systems.

Blocking Polysulfides and Facilitating Lithium-Ion Transport: Polystyrene Sulfonate@HKUST-1 Membrane for Lithium-Sulfur Batteries.

Minimizing the shuttle effect of polysulfides (PS) is crucial for practical applications of lithium-sulfur (Li-S) batteries. However, the trade-off between effective suppression of the shuttle effect and fast redox reaction kinetics is inevitable for separator-based Li-S batteries. Herein, via a self-confined solid-conversion process, we develop a polystyrene sulfonate (PSS)-threaded well-intergrown HKUST-1 (Cu3(BTC)2) (BTC: 1,3,5-benzenetricarboxylic acid)-coated Celgard separator (PSS@HKUST-1/Celgard, PHC) for high-performance Li-S batteries. The PHC membrane favors the interception and accommodation of long-chain PS. Notably, enormous sulfonate groups of the three-dimensional PSS networks in PSS@HKUST-1 membrane significantly facilitate lithium-ion transport, which guarantee fast redox kinetics. The PHC separator demonstrates efficient inhibition of PS (i.e., 4 orders of magnitude lower in PS permeation rate) with fast Li+ transportation (i.e., 71% higher in ionic conductivity) than the Celgard separator. When applying the PHC membrane in Li-S batteries with conventional sulfur/super P carbon cathode, highly reversible capacity with an average fading rate of 0.05% per cycle is maintained for 500 cycles at 0.5 C, excellent rate performance up to 5 C, and high areal capacity over 7 mA h cm-2 are also achieved. This work paves a new way for addressing the trade-off between suppressing the PS shuttle effect and fast kinetic reaction for separator-based Li-S batteries.