The processing of facial expressions is often studied using static pictorial cues. Recent work, however, suggests that viewing changing expressions more robustly evokes physiological responses. Here, we examined the sensitivity of steady-state visual evoked potentials and intrinsic oscillatory brain activity to transient emotional changes in facial expressions. Twenty-two participants viewed sequences of grayscale faces periodically turned on and off at a rate of 17.5 Hz, to evoke flicker steady-state visual evoked potentials (ssVEPs) in visual cortex. Each sequence began with a neutral face (flickering for 2290 ms), immediately followed by a face from the same actor (also flickering for 2290 ms) with one of four expressions (happy, angry, fearful, or another neutral expression), followed by the initially presented neutral face (flickering for 1140 ms). The amplitude of the ssVEP and the power of intrinsic brain oscillations were analyzed, comparing the four expression-change conditions. We found a transient perturbation (reduction) of the ssVEP that was more pronounced after the neutral-to-angry change compared to the other conditions, at right posterior sensors. Induced alpha-band (8-13 Hz) power was reduced compared to baseline after each change. This reduction showed a central-occipital topography and was strongest in the subtlest and rarest neutral-to-neutral condition. Thus, the ssVEP indexed involvement of facesensitive cortical areas in decoding affective expressions, whereas mid-occipital alpha power reduction reflected condition frequency rather than expression-specific processing, consistent with the role of alpha power changes in selective attention.

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Visual features associated with a task and those that predict noxious events both prompt selectively heightened visuocortical responses. Conflicting views exist regarding how the competition between a task‐related and a threat‐related feature is resolved when they co‐occur in time and space. Utilizing aversive classical Pavlovian conditioning, we investigated the visuocortical representation of two simultaneously presented, fully overlapping visual stimuli. Isoluminant red and green random dot kinematogram (RDK) stimuli were flickered at distinct tagging frequencies (8.57 Hz, 12 Hz) to elicit distinguishable steady‐state visual evoked potentials (ssVEPs). Occasional coherent motion events prompted a motor response (task) or predicted a noxious noise (threat). These events occurred either in the green (task cue), the red (threat cue), or in both RDKs simultaneously. In the initial habituation phase, participants responded to coherent motion of the green RDK with a key press, but no loud noise was presented at any time. Here, selective amplification was seen for the task‐relevant (green) RDK, and interference was observed when both RDKs simultaneously showed coherent motion. Upon pairing the threat cue with the noxious noise in the subsequent acquisition phase, the threat cue‐evoked ssVEP (red RDK) was also amplified, but this amplification did not interact with amplification of the task cue or alter the behavioral or visuocortical interference effect observed during simultaneous coherent motion. Although competing feature conjunctions resulted in interference in the visual cortex, the acquisition of a bias toward an individual threat‐related feature did not result in additional cost effects.

The extent to which visuocortical processing is altered when observers learn to categorize novel visual stimuli via labeling is not well understood. The present investigation used steady state visual evoked potential (ssVEP) frequency tagging to test the hypothesis that learning to categorize novel objects via labeling prompts a competitive advantage over concurrently presented stimuli. In the learning (label-training) phase, participants (n = 24) categorized objects according to two different species labels and faces according to gender. A control group (n = 26) viewed the same stimuli without label learning. Before and after learning, faces and objects were superimposed and viewed concurrently while periodically turned on and off at unique temporal rates (5/s or 6/s). The spectral power of the ssVEP at each frequency was projected to an L2 (minimum) norm estimated source space, and competition between faces and objects was compared using permutation-controlled mass univariate t tests. Results showed that, only in the training group, learning to label novel objects led to a competitive advantage over faces across a network of occipito-temporal and fronto-parietal cortical regions. These changes were more pronounced in participants showing more improvement across the label learning phase. Together, the findings support the notion that learning to label novel object categories affects neural competition though recurrent neural interactions in regions commonly associated with visual perception and selective attention.

16Visual features that are associated with a task and those that predict noxious events both prompt 17 selectively heightened visuocortical responses. Conflicting views exist regarding how the 18 competition between a task-related and a threat-related feature is resolved when they co-occur in 19 time and space. Utilizing aversive differential Pavlovian conditioning, we investigated the 20 visuocortical representation of two simultaneously presented, fully overlapping visual stimuli. 21 Stimuli were isoluminant red and green random dot kinematograms (RDKs) which flickered at 22 two tagging frequencies (8.57 Hz, 12 Hz) to elicit distinguishable steady-state visual evoked 23 potentials (ssVEPs). Occasional coherent motion events prompted a motor response or predicted 24 a noxious noise. These events occurred either in the green (task cue), the red (threat cue), or in 25 both RDKs simultaneously. In an initial habituation phase, participants responded to coherent 26 motion of the green RDK with a key press, but no loud noise was presented at any time. Here, 27 selective amplification was seen for the task-relevant (green) RDK, but interference was 28 observed when both RDKs simultaneously showed coherent motion. Upon pairing the threat cue 29 with the noxious noise in the subsequent acquisition phase, the threat cue-evoked ssVEP (red 30 RDK) was also amplified, but this amplification did not interact with amplification of the task 31 cue, and did not alter the behavioral or visuocortical interference effect seen during simultaneous 32 coherent motion. Results demonstrate that although competing feature conjunctions result in 33 interference in visual cortex, the acquisition of a bias towards an individual threat-related feature 34 does not result in additional cost effects. 35 36 37 Cortical competition between task and threat cues 3 Significance statement 38 Selectively perceiving and adaptively responding to cues associated with danger are fundamental 39 functions of the vertebrate brain. In humans, their disruption or dysregulation is at the core of 40 many psychiatric diagnoses, including fear, anxiety, post-traumatic syndromes, and mood 41 disorders. The present study examined the competitive interactions between the prioritization of 42 threat cues and a concurrent cognitive task, to characterize how the human attention system 43 manages limited resources in the presence of threat. Results showed that the selection of an 44 individual feature signaling imminent threat is not at the cost of concurrent attention 45 performance, even when threat and task stimuli overlapped in space. Findings support recent 46 models of emotion/attention interactions that emphasize flexible, feature-based allocation of 47 resources to biologically relevant stimuli. 48 49 Cortical competition between task and threat cues 4 Introduction 50 The visual system receives dense sensory information, continually exceeding the limited 51 capacity of visual cognition. In response to this challenge, the human brain has evolved 52 mechanisms...