Think Outside the Box: Small, Enclosed Spaces Alter Brain Activity as Measured with Electroencephalography (EEG)

This within-subjects study investigated the effect of small enclosed spaces on human brain activation during a simple word encoding task. A small and movable wooden box was designed, inside of which participants were exposed to visually presented words while asked to decide whether or not the first and last letters of each word were in alphabetical order. Simultaneously, brain activity was recorded via EEG. Respective encoding-related brain potentials were contrasted to an open space condition with the same task instruction. Data processing revealed that brain potentials were significantly more negative going at left lateral-frontal electrode locations when participants were inside the box compared to outside. First, we interpret this finding to show an increase in frontal brain activity reflecting higher amygdala activation while inside the box, i.e. a bottom-up process. Given the enclosed nature of this condition, one may assume fear-related brain responses to occur, reflecting projections from the amygdaloid complex to the frontal cortex. A second interpretation is that the increased lateral-frontal activity while inside the box stems from frontal regulation of negative affective responses, i.e. a top-down process, associated with the enclosed space. A third alternative interpretation is that attentional processes mediated by the anterior cingulate cortex (ACC) are active on higher levels while inside the box versus outside. Under the assumption that the event-related potential (ERP) differences are indeed fear-related, we want to suggest a new psychological construct that is subsequently introduced as implicit claustrophobia, i.e. a non-conscious fear of enclosed spaces.