Human electroencephalographic correlates of defensive approach towards a social threat

Introduction: The behavioural inhibition system (BIS) is thought to respond to goal conflict and motivate defensive approach towards threats (1). There is substantial neurological evidence for this theory in non-human animals (1). Conversely, in humans, there is growing neurological evidence that the BIS responds to goal conflict (1-2) and almost no neurological evidence that it motivates defensive approach. To address this, we used a social stimulus to create threat within a goal conflict task and recorded electroencephalogram (EEG) activity.

Methods: Participants repeatedly ‘approached’ a confederate in a dark room by making eye contact. The confederate’s distance and expression varied between trials to adjust the threat level and the participant’s motivation for defensive approach. Continuous EEG activity was recorded and transformed into current source density (CSD) power and coherence spectra within the theta and alpha wavebands.

Approach for statistical analysis: EEG data were entered into a PCA to produce spatial components. EEG data within the spatial components were then compared between high and low defensive approach conditions using hierarchical ANOVAs. Forced entry regression models were used to identify any EEG variables that predicted psychometric scores.

Results and conclusions: Theta coherence significantly increased and alpha CSD power significantly decreased during the high defensive approach condition. The increased theta coherence provides evidence that the BIS does direct defensive approach in humans, as previously found in animals.The decreased alpha CSD power suggests that the stimuli were highly engaging. Subsequently, social stimuli should be considered for use in future goal conflict experiments.