Behavioral and Neural Correlates of Stress in Response to Threat In Virtual Reality
Post by Cody Walters
What’s the science?
It has been challenging to study fear and anxiety in humans owing to the limited number of experimental paradigms that mimic naturalistic threat scenarios in a lab setting. This week in Current Biology, Balban et al. utilized a novel virtual reality task to study the behavioral, physiological, and neural correlates of visually evoked threat in human subjects.
How did they do it?
Subjects wore a virtual reality (VR) headset that realistically depicted the laboratory room where the experiment was being conducted. While wearing the headset, subjects were instructed to complete a cognitive task using a virtual panel on the wall, then 1 minute into the task the panel would move to the other end of the virtual room. At the moment of the panel transition, the VR room would undergo one of two possible modifications: a ‘no heights’ stimulus (during which the walls and ceiling were removed to reveal a gray background) and a ‘heights’ stimulus (during which the walls, ceiling, and parts of the floor were removed to reveal a 150 ft above-the-ground skyscraper landscape).
During the heights stimulus, participants navigated across a plank to reach the panel on the other side of the room and complete the cognitive task, eliciting a height-induced visual threat response. While subjects performed the task the authors recorded their heart rate, skin conductance levels, eye movements, and respiration. Additionally, the authors ran a similar experiment in a cohort of epilepsy patients fitted with intracranial electroencephalography (iEEG) for seizure localization, thus allowing for the recording of neural data in tandem with skin conductance and eye tracking metrics in this group.
What did they find?
The authors found that the participants’ skin conductance, heart rate, and respiration all increased upon seeing the heights stimulus. During the heights condition, visual scans surrounding the plank positively correlated with skin conductance levels and latency to step out onto the plank (a measure of behavioral inhibition). These data indicate that the virtual heights stimulus triggered a physiological threat response. The authors observed that participants in the control condition exhibited less physiological arousal, fewer visual scans, and a reduction in the latency to approach the opposite side of the room compared to the heights condition. Individuals with anxiety disorders experience heightened levels of physiological arousal, yet it remains unclear how it affects their threat reactivity. To explore this question, the authors recruited a cohort of subjects who scored high in generalized or trait anxiety to perform the task. Relative to control subjects, anxious individuals (1) experienced an elevated skin conductance response (the fast-changing component of the galvanic skin response), (2) performed more visual scans, and (3) exhibited a significantly greater latency to step out onto the plank. Interestingly, there were sex differences among the anxious subjects, with females exhibiting a greater degree of behavioral inhibition than males.
In order to relate these behavioral and peripheral measures of arousal with neural signals, the authors recorded iEEG data from the insula and orbitofrontal cortex in epilepsy patients while they performed the task. They found that gamma activity in the insula positively correlated with skin conductance response during the heights stimulus, with high gamma activity preceding an elevated skin conductance response by approximately 8 seconds. Additionally, the authors found that there was elevated gamma activity in the insula during moments of threat-induced visual scanning. In the orbitofrontal cortex, on the other hand, theta activity negatively correlated with skin conductance response during the heights stimulus.
What’s the impact?
This study showed that increased visual scanning is a behavioral correlate of anxiety, and that brain activity is altered prior to sympathetic arousal induced by visual threat. Altogether, this study used a novel virtual reality paradigm to identify behavioral, physiological, and neural correlates of human stress in response to a semi-naturalistic threat scenario.
Balban et al. Human Responses to Visually Evoked Threat. Current Biology (2020). Access the publication here.