Neurodynamics and hemispheric lateralization in threat and ambiguous negative scene recognition

Abstract

Efficient threat detection and appropriate action are critical for survival. However, some stimuli are merely negative without an impending threat and may offer useful clues about past or future dangers. We have shown previously (Kveraga et al., 2015) that threat and merely negative scene images are well discriminated and activate distinct brain networks in fMRI. However, the neurodynamics and hemispheric contributions underlying this process have not been studied. Methods: In this MEG study, we employed bilaterally presented threat or merely negative scene images paired with contextually matched neutral scenes in a 2AFC paradigm. Participants (N=64) had to identify the threatening or negative scene in each pair via a key press corresponding to the side of presentation. We extracted source-localized MEG activity from five ROIs in both hemispheres: fusiform face area (FFA), posterior STS (pSTS), periamygdaloid cortex (PAC), parrahippocampal cortex (PHC), and orbitofrontal cortex (OFC). Results: When threat or merely negative scenes were presented in the left visual hemifield, the contralateral right hemisphere (RH) and the ipsilateral left hemisphere (LH) showed significantly greater activation starting at about 300-400 ms for threat vs. merely negative scenes. This threat amplitude advantage was significantly greater in LH. Conversely, when threat or merely negative scenes were presented in the right visual hemifield, the contralateral LH generally had a phase lead in activity for threat vs. merely negative stimuli but no amplitude difference, while the ipsilateral RH had higher activity to merely negative scenes late in the trial, beginning at ~700 ms. Conclusions: Our findings show that deciding between two scene images leads to differential hemispheric dynamics. Threat images evoke greater activity when presented on the left, in both LH and RH, while merely negative images evoke increased later activity when presented in the right hemifield.

Meeting abstract presented at VSS 2017