Unconscious processing of coarse visual information during anticipatory threat

Fear lies in the eyes of the beholder-Robust evidence for reduced gaze dispersion upon avoidable threat

A rapid detection and processing of relevant information in our environment is crucial for survival. The human eyes are drawn to social or threatening stimuli as they may carry essential information on how to behave appropriately in a given context. Recent studies further showed a centralization of gaze that reminded of freezing behaviors in rodents. Probably constituting a component of an adaptive defense mode, centralized eye movements predicted the speed of motor actions. Here we conducted two experiments to examine if and how these presumably survival-relevant gaze patterns interact. Subjects viewed images including social, that is, faces (Experiment 1, N = 50) or threatening stimuli, that is, snakes or spiders (Experiment 2, N = 50) while awaiting an inevitable (shock), no (safety), or an avoidable shock (flight) they could escape from by a fast button press. The social and threatening cues within the scenes differed in their distance from the image center and we acquired eye-tracking and autonomic physiological data. Although we observed an initial orienting toward social and threatening stimulus aspects, this exploration pattern vanished towards the end of flight trials when a pronounced centralization of gaze emerged. Replicating previous findings, the amount of this center bias predicted the speed of motor reactions, and we observed a concurrent activation of the sympathetic and parasympathetic nervous system. Taken together, the exploration of potentially relevant cues seems to be part of a reflexive-orienting response regardless of contextual valence. However, centralization of gaze may be a threat-specific action-preparatory response that occurs across a wide range of stimulus contexts.

Recognizing the Death Motif in the Near-Death Experience

The typical near-death experience (NDE) is generally understood as an altered state of consciousness in which the experient has the impression of existing as an extrapersonal self out of and/or away from their physical body during real or presumed life-threatening and/or near-death circumstances. This presumed extrapersonal self can sometimes have a perception of being located within the proximity of the physical body whereas at other times it is under the assumption of having ventured to a transcendental location such as an otherworldly realm. The ego, while in this presumed disembodied state, often has the impression of encountering NDE personages such as deceased people, otherworldly spirits, and/or divine beings, especially during transcendental NDEs. However, this paper suggests that all of these noted features are part of a broader recognizable death motif in NDE reports, and provides qualitative examples of different types of this death symbolism for examination and exploration. It then discusses how the death motif in NDE reports possibly indicates a purposeful psychological function to heighten awareness of a threat to life though death symbolism that is meant to boost the desire and resilience to live and survive.

Identifying the duration of emotional stimulus presentation for conscious versus subconscious perception via hierarchical drift diffusion models

To investigate subliminal priming effects, different durations for stimulus presentation are applied ranging from 8 to 30 ms. This study aims to select an optimal presentation span whichleads to a subconscious processing. 40 healthy participants rated emotional faces (sad, neutral or happy expression) presented for 8.3 ms, 16.7 ms and 25 ms. Alongside subjective and objectivestimulus awareness, task performance was estimated via hierarchical drift diffusion models. Participants reported stimulus awareness in 65 % of the 25 ms trials,in 36 % of 16.7 ms trials, and in 2.5 % of 8.3 ms trials.Emotion-dependent responses were reflected in decreased performance (drift rates, accuracy)during sad trials. The detection rate (probability of making a correct response) during 8.3 ms was 12.2 % and slightly above chance level (33.333 % for three response options) during 16.7 ms trials (36.8 %). The experiments suggest a presentation time of 16.7 ms as optimal for subconscious priming. An emotion-specific response was detected during 16.7 ms while the performanceindicates a subconscious processing.

Threat shapes visual context sensitivity selectively through low-spatial-frequency channels

Threat has long been supposed to affect human cognitive processing including visual size perception. Whether such threat-related modulation effect varies as a function of spatial frequency is largely unexplored. Here we used low- or high-pass filtered threatening animal and fearful face images as primes and measured their effects on the processing of the Ebbinghaus illusion. Results showed that threatening-animal primes relative to neutral ones significantly decreased the illusion magnitude in low-spatial-frequency rather than in high-spatial-frequency ranges. However, fearful- and neutral-face primes had a comparable effect on the illusion magnitude in both spatial frequency ranges. Notably, when inhibitory transcranial magnetic stimulation was applied to the left temporo-parietal junction (TPJ), fearful-face primes significantly decreased the illusion magnitude in low-spatial-frequency rather than in high-spatial-frequency ranges. However, the opposite pattern of results was observed with right TPJ stimulation. The findings suggest that threat shapes basic aspects of visual perception in a spatial frequency-specific manner, possibly via magnocellular projections from both subcortical and cortical fear-processing systems to early visual cortex.

Low-spatial-frequency information facilitates threat detection in a response-specific manner

The role of different spatial frequency bands in threat detection has been explored extensively. However, most studies use manual responses and the results are mixed. Here, we aimed to investigate the contribution of spatial frequency information to threat detection by using three response types, including manual responses, eye movements, and reaching movements, together with a priming paradigm. The results showed that both saccade and reaching responses were significantly faster to threatening stimuli than to nonthreatening stimuli when primed by low-spatial-frequency gratings rather than by high-spatial-frequency gratings. However, the manual response times to threatening stimuli were comparable to nonthreatening stimuli, irrespective of the spatial frequency content of the primes. The findings provide clear evidence that low-spatial-frequency information can facilitate threat detection in a response-specific manner, possibly through the subcortical magnocellular pathway dedicated to processing threat-related signals, which is automatically prioritized in the oculomotor system and biases behavior.

Anodal tDCS of right temporo-parietal junction promotes threat detection in low-spatial-frequency channels

Fast detection of threat is crucial for survival. Previous studies have suggested the involvement of low- and high-spatial-frequency (LSF and HSF) information in the process of threat detection. However, the specific contributions of LSF and HSF information to it are still controversial. Here we probed this issue by utilizing a prime procedure coupled with the transcranial direct current stimulation (tDCS) technique. Specifically, in a single-blind design, participants were exposed to LSF or HSF faces prior to the presentation of looming or receding spheres. Meanwhile, tDCS was applied over the right or left temporo-parietal junction (TPJ), which has been found to be preferentially associated with the processing of LSF and HSF information, respectively. The results showed significant LSF-related facilitation of threat detection when anodal tDCS was applied to the right TPJ. However, HSF-related facilitation of threat detection was not observed when anodal tDCS was applied to the left TPJ. The findings support the idea that LSF information can facilitate threat detection, and provide direct evidence that the right TPJ is vital for LSF-related facilitation of threat detection.