Experience in judging intent to harm modulates parahippocampal activity: an fMRI study with experienced CCTV operators.

Does visual experience in judging intent to harm change our brain responses? And if it does, what are the mechanisms affected? We addressed these questions by studying the abilities of Closed Circuit Television (CCTV) operators, who must identify the presence of hostile intentions using only visual cues in complex scenes. We used functional magnetic resonance imaging to assess which brain processes are modulated by CCTV experience. To this end we scanned 15 CCTV operators and 15 age and gender matched novices while they watched CCTV videos of 16 sec, and asked them to report whether each clip would end in violence or not. We carried out four separate whole-brain analyses including 3 model-based analyses and one analysis of intersubject correlation to examine differences between the two groups. The three model analyses were based on 1) experimentally pre-defined clip activity labels of fight, confrontation, playful, and neutral behaviour, 2) participants' reports of violent outcomes during the scan, and 3) visual saliency within each clip, as pre-assessed using eye-tracking. The analyses identified greater activation in the right superior frontal gyrus for operators than novices when viewing playful behaviour, and reduced activity for operators in comparison with novices in the occipital and temporal regions, irrespective of the type of clips viewed. However, in the parahippocampal gyrus, all three model-based analyses consistently showed reduced activity for experienced CCTV operators. Activity in the anterior part of the parahippocampal gyrus (uncus) was found to increase with years of CCTV experience. The intersubject correlation analysis revealed a further effect of experience, with CCTV operators showing correlated activity in fewer brain regions (superior and middle temporal gyrus, inferior parietal lobule and the ventral striatum) than novices. Our results indicate that long visual experience in action observation, aimed to predict harmful behaviour, modulates brain mechanisms of intent recognition.