Background. The ability to adaptively transfer acquired fear to novel situations is fundamental for survival in ever-changing environments and may contribute to the emergence and persistence of anxiety disorders. Consequently, research has focused on the assessment of fear generalization profiles to predict individual differences in anxiety. However, substantial heterogeneity in the operationalization of generalization hampers comparisons across studies and poses a risk to the replicability of findings. Methods. To address these issues, we reviewed the literature to identify commonly used methods for characterizing perceptual fear generalization profiles. Then, we conducted simulation analyses to examine correlations between indices and probe their robustness against measurement noise. Finally, we used 2 large empirical datasets (N = 1175 and N = 256 healthy humans) to examine the reliability of these indices and their validity in predicting anxiety-related traits. Results. All identified indices were substantially correlated but highly sensitive to measurement noise, with only minimal differences between methods. Reliabilities were moderate for subjective ratings but poor for skin conductance responses. All indices of fear generalization were unrelated to anxiety-related traits. Conclusions. Overall, a more comprehensive discussion of conceptual and methodological issues is needed to enable informed decisions about how to reliably and validly estimate fear generalization and its relationship with anxiety-related traits or clinical symptoms.
Adapting behavior to environmental demands is a fundamental aspect of survival. In the face of unfamiliar potential dangers, organisms display a wide range of defensive mechanisms, such as using contextual information to prepare for upcoming threats and extrapolating from previous experiences with similar encounters. Importantly, these different types of threat-related information place distinct demands on the attentional system, potential, context-related threat induces a state of hypervigilance, whereas imminent, acute threat requires selective attention. While these individual mechanisms are increasingly well understood, their interactions remain elusive, particularly at the neurophysiological level. Therefore, the current study aimed to orthogonally combine threat generalization with aversive contextual information and measure correlates of defensive behavior on a subjective, autonomic, and electrocortical level. Fifty-two human participants completed a threat generalization paradigm followed by a context phase in which the conditioned visual cues were presented against aversive or neutral background images, respectively. Results revealed successful threat generalization for subjective and pupillary responses with overall heightened responses for cues presented in aversive compared to neutral contexts. For visuocortical activity as measured by steady-state visually evoked potentials, this response pattern was separated into different frequencies. While the fundamental frequency showed the general main effect of aversive contexts, the second harmonic followed a generalization gradient, suggesting a segregation of competing attentional demands via neural harmonics. Together, these findings provide new insights into adaptive defensive behavior in complex situations, characterized by an additive model of different defensive processes.
In response to avoidable danger, organisms often exhibit freezing-like behavior. Recent research suggests that freezing is not merely a passive response but involves a state of attentive immobility aimed at enhancing threat avoidance and perception. However, the attentional mechanisms involved in response to avoidable threats at the level of the brain remain poorly understood. To address this gap, we employed EEG, eye-tracking, and measurements of autonomic activity. Our findings revealed a suppression of EEG alpha power, along with cardiac deceleration, reduced eye-movements, and heightened sympathetic activity during the anticipation of avoidable threats. Moreover, this response pattern was predictive of motor response times. These results underscore the significance of heightened perceptual processing during freezing-like behavior in humans.
This study investigated how potential and acute threat states interact by examining physiological and subjective responses to fear cues in different contextual settings. Results showed that inherently aversive contexts amplified defensive responses more than conditioned contexts, highlighting the additive nature of threat processing.