Effects of 7.5% carbon dioxide (CO2) inhalation and ethnicity on face memory

Alcohol Use Predicts Face Perception Impairments and Difficulties in Face Recognition

Background: Risky alcohol use is related to a variety of cognitive impairments, including memory and visuo-perceptual difficulties. Remarkably, no prior work has assessed whether usage of alcohol can predict difficulties perceiving facial identity. Objectives: Therefore, this study aimed to investigate whether riskier alcohol consumption predicted impairments in face perception and self-reported difficulties in face recognition. Results: Participants (N = 239, male = 77) were over 18 years old and had normal or corrected-to-normal vision. Alcohol use was assessed using the Alcohol Use Disorder Identification Test (AUDIT), while face recognition difficulties were determined by the 20-item Prosopagnosia Index questionnaire (PI20). A subsample of participants (N = 126, male = 51) completed the Cambridge Face Perception task (CFPT) to assess their face perception ability. Multiple linear regressions showed significant models of prediction on both face perception and face recognition when considering AUDIT score and age as predictors. Conclusion: This study suggested, for the first time, that risky alcohol use predicts both poorer visuo-perceptual processing for faces and self-reported difficulties in face recognition.

Can anxiety and race interact to influence face-recognition accuracy? A systematic literature review

Wrongful convictions continue to occur through eyewitness misidentification. Recognising what factors, or interaction between factors, affect face-recognition is therefore imperative. Extensive research indicates that face-recognition accuracy is impacted by anxiety and by race. Limited research, however, has examined how these factors interact to potentially exacerbate face-recognition deficits. Brigham (2008) suggests that anxiety exacerbates other-race face-recognition deficits. Conversely, Attentional Control Theory predicts that anxiety exacerbates deficits for all faces. This systematic review examined existing studies investigating the possible interaction between anxiety and face-race to compare these theories. Recent studies included in this review found that both anxiety and race influence face-recognition accuracy but found no interaction. Potential moderators existing in reviewed studies, however, might have influenced their results. Separately, in some studies reviewed, anxiety induced during retrieval impacted recognition, contrasting with the conclusions of previous reviews. Recommendations for future research are given to address moderators potentially impacting results observed previously.

The effects of carbon dioxide exposure concentrations on human vigilance and sentiment in an enclosed workplace environment

In this study, fifteen participants were exposed to different carbon dioxide (CO₂ ) concentrations in an enclosed environmental chamber to investigate the potential effects of elevated CO₂ concentrations on human vigilance and sentiment. The psychomotor vigilance test (PVT), the Karolinska Sleepiness Scale (KSS), and the Positive and Negative Affect Schedule (PANAS) were measured before and after each 4-hour CO₂ exposure session. The statistical analyses of the PVT performance metrics showed that the human vigilance decreased significantly with the elevated CO₂ concentration from 1500 ppm to above 3500 ppm, but no significant change was observed in the KSS score. Moreover, although the participants reported less positive and more negative emotions as the CO₂ exposure concentration increased, the effect of CO₂ concentration on human sentiment was not potent. In sum, the findings suggested a detrimental effect of CO₂ exposure concentration on human vigilance at the CO₂ concentration of 3500 ppm, which is below the current occupational exposure limit of 5000 ppm. It is worth noting that the order of CO₂ exposures was not balanced among the participants, which remains a major limitation of this study.

Effects of state anxiety on gait: a 7.5% carbon dioxide challenge study

We used the 7.5% carbon dioxide (CO₂) model of anxiety induction to investigate the effects of state anxiety on normal gait and gait when navigating an obstacle. Healthy volunteers (n = 22) completed a walking task during inhalations of 7.5% CO₂ and medical air (placebo) in a within-subjects design. The order of inhalation was counterbalanced across participants and the gas was administered double-blind. Over a series of trials, participants walked the length of the laboratory, with each trial requiring participants to navigate through an aperture (width adjusted to participant size), with gait parameters measured via a motion capture system. The main findings were that walking speed was slower, but the adjustment in body orientation was greater, during 7.5% CO₂ inhalation compared to air. These findings indicate changes in locomotor behaviour during heightened state anxiety that may reflect greater caution when moving in an agitated state. Advances in sensing technology offer the opportunity to monitor locomotor behaviour, and these findings suggest that in doing so, we may be able to infer emotional states from movement in naturalistic settings.

Acute anxiety and autonomic arousal induced by CO2 inhalation impairs prefrontal executive functions in healthy humans

Acute anxiety impacts cognitive performance. Inhalation of air enriched with carbon dioxide (CO2) in healthy humans provides a novel experimental model of generalised anxiety, but has not previously been used to assess cognition. We used inhalation of 7.5% CO2 to induce acute anxiety and autonomic arousal in healthy volunteers during neuropsychological tasks of cognitive flexibility, emotional processing and spatial working memory in a single-blind, placebo-controlled, randomized, crossover, within-subjects study. In Experiment 1 (n = 44), participants made significantly more extra-dimensional shift errors on the Cambridge Neuropsychological Test Automated Battery (CANTAB) Intra-Extra Dimensional Set Shift task under CO2 inhalation compared with 'normal' air. Participants also had slower latencies when responding to positive words and made significantly more omission errors for negative words on the CANTAB Affective Go/No-go task. In Experiment 2 (n = 28), participants made significantly more total errors and had poorer heuristic search strategy on the CANTAB Spatial Working Memory task. In both experiments, CO2 inhalation significantly increased negative affect; state anxiety and fear; symptoms of panic; and systolic blood pressure/heart rate. Overall, CO2 inhalation produced robust anxiogenic effects and impaired fronto-executive functions of cognitive flexibility and working memory. Effects on emotional processing suggested a mood-congruent slowing in processing speed in the absence of a negative attentional bias. State-dependent effects of anxiety on cognitive-emotional interactions in the prefrontal cortex warrant further investigation.

State anxiety and information processing: A 7.5% carbon dioxide challenge study

We used the 7.5% carbon dioxide model of anxiety induction to investigate the effects of state anxiety on simple information processing. In both high- and low-anxious states, participants (n = 36) completed an auditory–visual matching task and a visual binary categorization task. The stimuli were either degraded or clear, so as to investigate whether the effects of anxiety are greater when signal clarity is compromised. Accuracy in the matching task was lower during CO₂ inhalation and for degraded stimuli. In the categorization task, response times and indecision (measured using mouse trajectories) were greater during CO₂ inhalation and for degraded stimuli. For most measures, we found no evidence of Gas × Clarity interactions. These data indicate that state anxiety negatively impacts simple information processing and do not support claims that anxiety may benefit performance in low-cognitively-demanding tasks. These findings have important implications for understanding the impact of state anxiety in real-world situations.

The impact of threat of shock-induced anxiety on memory encoding and retrieval

Anxiety disorders are the most common mental health disorders, and daily transient feelings of anxiety (or "stress") are ubiquitous. However, the precise impact of both transient and pathological anxiety on higher-order cognitive functions, including short- and long-term memory, is poorly understood. A clearer understanding of the anxiety-memory relationship is important as one of the core symptoms of anxiety, most prominently in post-traumatic stress disorder (PTSD), is intrusive reexperiencing of traumatic events in the form of vivid memories. This study therefore aimed to examine the impact of induced anxiety (threat of shock) on memory encoding and retrieval. Eighty-six healthy participants completed tasks assessing: visuospatial working memory, verbal recognition, face recognition, and associative memory. Critically, anxiety was manipulated within-subjects: information was both encoded and retrieved under threat of shock and safe (no shock) conditions. Results revealed that visuospatial working memory was enhanced when information was encoded and subsequently retrieved under threat, and that threat impaired the encoding of faces regardless of the condition in which it was retrieved. Episodic memory and verbal short-term recognition were, however, unimpaired. These findings indicate that transient anxiety in healthy individuals has domain-specific, rather than domain-general, impacts on memory. Future studies would benefit from expanding these findings into anxiety disorder patients to delineate the differences between adaptive and maladaptive responding.

Dynamic Dazzle Distorts Speed Perception

Static high contrast (‘dazzle’) patterns, such as zigzags, have been shown to reduce the perceived speed of an object. It has not escaped our notice that this effect has possible military applications and here we report a series of experiments on humans, designed to establish whether dynamic dazzle patterns can cause distortions of perceived speed sufficient to provide effective defence in the field, and the extent to which these effects are robust to a battery of manipulations. Dynamic stripe patterns moving in the same direction as the target are found to increase the perceived speed of that target, whilst dynamic stripes moving in the opposite direction to the target reduce the perceived speed. We establish the optimum position for such dazzle patches; confirm that reduced contrast and the addition of colour do not affect the performance of the dynamic dazzle, and finally, using the CO₂ challenge, show that the effect is robust to stressful conditions.