Decoding The Neural Correlates of Implicit Racial Bias Using Intracranial Electroencephalography

Introduction: Implicit racial bias refers to unconscious negative attitudes towards another person or group based on their racial background and may act as a critical mechanism for driving health disparities. In this study, we investigated human intracranial recordings to determine the neural correlates that encode the cognitive processing of implicit racial bias.

Methods: We recorded from 17 stereotactic EEG electrodes implanted in one patient with medically refractory epilepsy. To measure unconscious preferences, the patient performed the race and weapons implicit association tests (IAT) which involves making rapid association of white and black faces with positive or negative words and tools or weapons, respectively. IAT D scores were analyzed and ranged from -2 to 2 with positive values indicating a pro-white bias and negative scores indicating a pro-black bias. Power spectral densities were computed for each epoch and were dimensionally reduced with principal component analysis (PCA). The PCA components were then passed into a linear support vector machine (SVM) classification algorithm to identify neural correlates of implicit racial bias.

Results: The patient demonstrated slight pro-black bias on the race IAT (D=-0.22) and moderate pro-white bias on the weapons IAT (D=0.36). During the race IAT, neural activity was highest in the right hippocampus, bilateral inferior temporal, bilateral middle temporal, and right parahippocampal and lateral occipital regions. For the weapons IAT, similar regions demonstrated the highest classification, including the right hippocampus, and bilateral parahippocampal and left middle temporal regions. However, significant neural activity was observed in the right insula and right amygdala.

Conclusion : In this preliminary pilot study, we identified several corticolimbic structures involved in the cognitive processing of the implicit bias test, including the parahippocampal, middle temporal, and right hippocampal regions. We found evidence that the amygdala and insula may be important in encoding stronger racially biased responses.