Encoding of Race Categories by Single Neurons in the Human Brain

Area of Science:

• Neuroscience
• Social Cognitive Neuroscience

Background:

• Previous research suggests automatic processing of race during face perception, with out-group faces treated categorically.
• Functional imaging studies have identified hemodynamic correlates, but single-neuron responses remain less explored.

Purpose of the Study:

• To investigate single-neuron responses to race-specific features during face perception, even when race is task-irrelevant.
• To examine neural correlates of race processing in brain regions involved in emotion and decision-making.

Main Methods:

• Microwire recordings were performed in epilepsy patients during a face perception task.
• Patients viewed computer-generated faces varying in emotion and racial category, independent of the task.
• Neural firing rates were analyzed for race-driven changes in specific brain regions.

Main Results:

• Race-driven changes in neural firing rates were observed in the amygdala, anterior cingulate cortex, and hippocampus.
• A significant percentage of neurons in the amygdala (28%) and anterior cingulate cortex (45%) predicted racial categories.
• Nearly equal proportions of neurons responded to White and Black faces across regions, with a smaller fraction in the hippocampus responding only to White faces.

Conclusions:

• Race is represented in a distributed manner across brain areas involved in affective judgments, decision-making, and memory.
• Perceptual coding of race-specific cues occurs automatically, even when these cues are irrelevant to the task.