Perception and memory of threatening human faces in the crow brain: FDG-PET mapping

Objectives Crows scrutinize humans they encounter, learn human faces, and remember brief associations with specific people. This study investigates the neural correlates underlying a crow’s ability to remember a threatening face using (F-18) flurodeoxyglucose with postitron emission tomography (FDG-PET).

Methods Crows (Corvus brachyrhynchos, n=12) were captured by investigators wearing masks, then subsequently fed by persons with different masks. For the FDG-PET activation protocol, crows were removed from a covered cage, with head covered, received 1 mCi FDG via ip injection and returned to cage for 2 min rest. During uptake, awake crows were shown either; 1) face that captured it (THREAT), 2) face that fed it (NEUT), or empty room (NOFACE) in 1min. on/off blocks for 14 min. After stimulation, crows were anesthetized and micro-PET imaging performed. Optimal imaging time was determined by pilot dynamic imaging. High-res images were reconstructed by 3D OSEM/MAP to spatial resolution of 2.5 mm. Images were stereotactically aligned to a crow atlas and global normalized. Voxel-wise Z-mapping was used to evaluate group changes between different stimulation protocols.

Results Compared to NOFACE, THREAT activated arcopallium (Z=4.4), brainstem (Z=4.2) and nido/mesopallium (Z=4.1) where descending nerve tracts from the arcopallium through brainstem are known to be active in fear and startle responses. Compared to NOFACE, NEUT activated septum (Z=4.0), medial striatum (Z=3.9) and hippocampus (Z=3.9), which are involved in memory and social behavior. Combining THREAT+NEUT as a measure of generic “face perception” activated nidopallium (Z=4.2), lateral striatum (Z=4.0) and hippocampus (Z=3.8).

Conclusions In this novel application of micro-PET to crow brain mapping, we found activation patterns analogous to human emotion/fear processing with the perception of a threatening human face. Neutral faces activated memory, affiliative and reward circuits. Future studies will examine activation related to predator fear (hawk) and the acquisition of human face memory